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The Linux Users` Guide

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1. o e 95 10 8 10 Specializing Buffers Modes o 96 8 11 Programming Modes e 97 8 11 1 E Mode cores a ea es 97 SLIZ Scheme Mode ies a a adas Aa aed 98 8 11 3 Mall Mode veces a Pee E 99 8 12 Being Even More Efficient o o 100 8 13 Customizing Emacs e 101 8 14 Finding Out More 20 0 0 reni e rc a ge e 106 I Gotta Be Me 109 9 1 bash Customization 2 0 0 0 0 2 0 000000 109 Ol Shell Stattip oid os at oe ele ew Ra ea ee Poe AG a 109 9 1 2 Startup Files ocios er ee ete ee Be 110 9 1 3 Aliasings opaco A A Boe BES 110 9 1 4 Environment Variables o e 112 9 2 The X Window System Init Files o 119 9 2 1 Twm Configuration e 122 9 2 2 Fvwm Configuration e 128 93 Other Init Files oir res eR ee E a he ee N 129 9 3 1 TheEmacsImtFile o 129 932 FTP Defaults 2 4 32 44 22 a Sa Ba a A toa 129 9 3 3 Allowing Easy Remote Access to Your Account 130 9 3 4 Mail Forwarding o 132 9 4 Seeing Some Examples e e 132 Talking to Others 133 10 1 Electronic Mal 133 TOTT Sending Mall 2 2 7 4 4 te Seed he ee ee Ra ea ee 134 10 1 2 Reading Mail 2 2 2 2 en 134 10 2 More than Enough News 200000500008 136 10 3 Searching for Peop
2. Our method of protecting your rights has two steps 1 copyright the library and 2 offer you this license which gives you legal permission to copy distribute and or modify the library Also for each distributor s protection we want to make certain that everyone under stands that there is no warranty for this free library If the library is modified by someone else and passed on we want its recipients to know that what they have is not the original version so that any problems introduced by others will not reflect on the original authors reputations Finally any free program is threatened constantly by software patents We wish to avoid the danger that companies distributing free software will individually obtain patent licenses thus in effect transforming the program into proprietary software To prevent this we have made it clear that any patent must be licensed for everyone s free use or not licensed at all Most GNU software including some libraries is covered by the ordinary GNU General Public License which was designed for utility programs This license the GNU Library General Public License applies to certain designated libraries This license is quite differ ent from the ordinary one be sure to read it in full and don t assume that anything in it is the same as in the ordinary license The reason we have a separate public license for some libraries is that they blur the distinction we usually make between
3. u Undo the last command U Undo the current line from all changes on that line e Edit again Restores to the state of the last save vi not only allows you to undo changes it can reverse the undo Using the command delete 5 lines then restore the lines with u The changes can be restored by the again vi offers commands which allow changes to the text to be made without first deleting then typing in the new version re Replace the character under the cursor with c Moves cursor right if repeat modifier used eg 2rc R Overwrites the text with the new text CW Changes the text of the current word cs Changes the text from current position to end of the line cnw Changes next n words same as ncw cn Changes to the end of the nth line el Changes to the end of the line same as c ec Changes the current line s Substitutes text you type for the current character ns Substitutes text you type for the next n characters The series of change commands which allow a string of characters to be entered are exited with the ESC key The command started from the current location in the word to the end of the word When using a change command that specifies a distance the change will apply vi will place a at the last character position The new text can overflow or underflow the original text length A 4 3 Copying and Moving sections of text Moving text involves a number of commands all combined to achieve the end r
4. WITHOUT WARRANTY OF ANY KIND EITHER EXPRESSED OR IM PLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PRO GRAM IS WITH YOU SHOULD THE PROGRAM PROVE DEFECTIVE YOU ASSUME THE COST OF ALL NECESSARY SERVICING REPAIR OR COR RECTION IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER OR ANY OTHER PARTY WHO MAY MODIFY AND OR REDISTRIBUTE THE PROGRAM AS PERMIT TED ABOVE BE LIABLE TO YOU FOR DAMAGES INCLUDING ANY GEN ERAL SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCU RATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSI BILITY OF SUCH DAMAGES How to Apply These Terms to Your New Programs If you develop a new program and you want it to be of the greatest possible use to the pub lic the best way to achieve this is to make it free software which everyone can redistribute and change under these terms To do so attach the following notices to the program It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty and each file should have at least the copy
5. home larry jobs 1 Running 3 Stopped home larry yes gt dev null amp yes unig gt dev null The means that job number is second in line to be put in the foreground if you just type fg without giving it any parameters The means the specified job is first in line a fg without parameters will bring job number 3 to the foreground However you can get to it by naming it if you wish home larry fg 1 yes gt dev null now type ctrl z to suspend it 1 Stopped yes gt dev null home larry Having changed to job number 1 and then suspending it has also changed the priorities of all your jobs You can see this with the jobs command home larry jobs 1 Stopped 3 Stopped home larry yes gt dev null yes unig gt dev null Now they are both stopped because both were suspended with ctrl z and number 1 is next in line to come to the foreground by default This is because you put it in the foreground manually and then suspended it The always refers to the most recent job that was suspended from the foreground You can start it running again hnome larry bg 1 yes gt dev null amp home larry jobs 1 Running 3 Stopped home larry yes gt dev null yes unig gt dev null Notice that now it is running and the other job has moved back up in line and has the Now let s kill them all so your system isn t permanently slowed b
6. s configuration look at Section 9 2 1 fvwm s configuration is covered in Section 9 2 2 5 4 1 When New Windows are Created There are three possible things a window manager will do when a new window is created It is possible to configure a window manager so that an outline of the new window is shown and you are allowed to position it on your screen That is called manual placement If you are presented with the outline of a window simply use the mouse to place it where you wish it to appear and click the left mouse button It is also possible that the window manager will place the new window somewhere on the screen by itself This is known as random placement Finally sometimes an application will ask for a specific spot on the screen or the window manager will be configured to display certain applications on the same place of the screen all the time For instance I specify that I want xc lock to always appear in the upper right hand corner of the screen 5 4 2 Focus The window manager controls some important things The first thing you ll be interested in is focus The focus of the server is which window will get what you type into the keyboard Usually in X the focus is determined by the position of the mouse cursor If the mouse cursor is in one xt erm s window that xterm will get your keypresses This is different from many other windowing systems such as Microsoft Windows OS 2 or the Macintosh where you must click
7. then the permission bits of the file must exactly match them A leading means that all permission bits must be set but makes no assumption for the other a leading is satisfied just if any of the bits are set Oops I forgot saying that the mode is written in octal or symbolically like you use them in chmod Next group of tests is related to the time in which a file has been last used This comes handy when a user has filled his space as usually there are many files he did not use since ages and whose meaning he has forgot The trouble is to locate them and find is the only hope in sight atime nn is true if the file was last accessed nn days ago ctime nn if the file status was last changed nn days ago for example with a chmod and mtime nn 1f the file was last modified nn days ago Sometimes you need a more precise timestamp the test newer file is satisfied if the file considered has been modified later than file So you just have to use touch with the desidered date and you re done GNU find add the tests anewer and cnewer which behave similarly and the tests amin cmin and mmin which count time in minutes instead than 24 hours periods Last but not the least the test I use more often name pattern is true if the file name exactly matches pattern which is more or less the one you would use in a standard 1s Why more or less Because of course you have to remember that all the parameters are processed by the
8. If you have one of these filesystems some of the information will merely be unavailable operation will be mostly unchanged of programs execute it Each of these permissions can be toggled seperately for the owner the group and all other users touch filel file2 fileN touch will update the time stamps of the files listed on the command line to the current time If a file doesn t exist touch will create it It is also possible to specify the time that touch will set files to consult the the manpage for touch chmod Rfv mode filel file2 fileN The command used to change the permissions on a file is called chmoa short for change mode Before I go into how to use the command let s discuss what permissions are in Unix Each file has a group of permissions associated with it These permissions tell Unix whether or not the file can be read from written to or executed as a program In the next few paragraphs IIl talk about users doing these things Any programs a user runs are allowed to do the same things a user is This can be a security problem if you don t know what a particular program does Unix recognizes three different types of people first the owner of the file and the person allowed to use chmod on that file Second the group The group of most of your files might be users meaning the normal users of the system To find out the group of a particular file use 1s 1 file Then there s
9. If you started X manually these methods should return you to the text mode prompt If you wish to logout type Logout at this prompt 5 2 What is The X Window System The X Window System is a distributed graphical method of working developed primarily at the Massachusetts Institute of Technology It has since been passed to a consortium of vendors aptly named The X Consortium and is being maintained by them The X Window System hereafter abbreviated as X has new versions every few years called releases As of this writing the latest revision is X11R6 or release six The eleven in X11 is officially the version number but there hasn t been a new version in many years and one is not currently planned There are two terms when dealing with X that you should be familiar The client is a X program For instance xterm is the client that displays your shell when you log on The server is a program that provides services to the client program For instance the server draws the window for xterm and communicates with the user There are several acceptable ways to refer to The X Window System A common though incorrect way of referring to X is X Windows Since the client and the server are two separate programs it is possible to run the client and the server on two physically separate machines In addition to supplying a standard method of doing graphics you can run a program on a remote machine across the country i
10. It overrides ibs and obs keywords cbs nn sets the conversion buffers to nn bytes This buffer is used when translating from ASCII to EBCDIC or from an unblocked device to a blocked one For example files created under VMS have often a block size of 512 so you have to set cbs to 1b when reading a foreign VMS tape Hope that you don t have to mess with these things skip nb and seek nb tell the program to skip nbl blocks respectively at the begin ning of input and at the beginning of output Of course the latter case makes sense if conversion not runc is given see below Each block s size is the value of ibs obs Beware if you did not set ibs and write skip 1b you are actually skip ping 512x512 bytes that is 256KB It was not precisely what you wanted wasn t it count nb means to copy only nbl blocks from input each of the size given by ibs This option together with the previous turns useful if for example you have a corrupted file and you want to recover how much it is possible from it You just skip the unreadable part and get what remains e conv conversion conversion convert the file as specified by its argument Possible conversions are aSCii which converts from EBCDIC to ASCII ebcdic and ibm which both perform an inverse conversion yes there is not a unique conversion from EBCDIC to ASCII The first is the standard one but the second works better when printing files on a IBM printer block which pads ne
11. Log in as guest pass word explorer and poke around Most of the example files given here can be found in home kfogel but there are other user directories as well You are free to copy any thing that you can read Please be careful floss is not a terribly secure box and you can almost certainly gain root access if you try hard enough I prefer to rely on trust rather than constant vigilance to maintain security Chapter 10 Talking to Others One basic notion underlying Usenet is that it is a cooperative Having been on Usenet for going on ten years I disagree with this The basic notion underlying Usenet is the flame Chuq Von Rospach Modern Unix operating systems are very good at talking to other computers or net working Two different Unix computers can exchange information in many many different ways This chapter is going to try to talk about how you can take advantage of that strong network ability We ll try to cover electronic mail Usenet news and several basic Unix utilities used for communication 10 1 Electronic Mail One of the most popular standard features of Unix is electronic mail With it you are spared the usual hassle of finding an envelope a piece of paper a pen a stamp and the postal service and instead given the hassle of negotiating with the computer 133 10 1 1 Sending Mail All you need to do is type mail username and type your message For instance suppose I wa
12. The second to last line the one with the long string of dashes is called the mode line Figure 8 1 Emacs was just started with emacs README Linux kernel release 1 0 These are the release notes for linux version 1 0 Read them carefully as they tell you what this is all about explain how to install the kernel and what to do if something goes wrong WHAT IS LINUX Linux is a Unix clone for 386 486 based PCs written from scratch by Linus Torvalds with assistance from a loosely knit team of hackers across the Net It aims towards POSIX compliance It has all the features you would expect in a modern fully fledged Unix including true multitasking virtual memory shared libraries demand loading shared copy on write executables proper memory management and TCP IP networking It is distributed under the GNU General Public License see the accompanying COPYING file for more details INSTALLING the kernel Fundamental Top In my mode line you see Top It might be All instead and there may be other minor differences Many people have the current time displayed in the mode line The line immediately below the mode line is called the minibuffer or sometimes the echo area Emacs uses the minibuffer to flash messages at you and occasionally uses it to read input from you when necessary In fact right now Emacs is telling you For information about the GNU Project and its goals type C h C p Ig
13. and there it has a hit bin 1s does exist and is executable so Bash stops searching for a program named 1s and runs it There might well have been another 1s sitting in the directory usr bin but bash would never run it unless I asked for it by specifying an explicit pathname hnome larry usr bin ls The PATH variable exists so that we don t have to type in complete pathnames for every command When you type a command Bash looks for it in the directories named in PATH in order and runs it if it finds it If it doesn t find it you get a rude error hnome larry clubly clubly command not found Notice that my PATH does not have the current directory in it If it did it might look like this home larry echo PATH usr TeX bin home larry bin bin usr bin usr local bin usr bin X11 usr TeX bin home larry This is a matter of some debate in Unix circles which you are now a member of whether you like it or not The problem is that having the current directory in your path can be a security hole Suppose that you cd into a directory where somebody has left a Trojan Horse program called 1s and you do an 1s as would be natural on entering a new directory Since the current directory came first in your PATH the shell would have found this version of 1s and executed it Whatever mischief they might have put into that program you have just gone ahead and executed and that could be quit
14. and type in the name of the function Or if you want to know what a function does in detail use C h f which prompts for a function name Remember since Emacs does completion on function names you don t really have to be sure what a function is called to ask for help on it If you think you can guess the word it might start with type that and hit to see if it completes to anything If not back up and try something else The same goes for file names even if you can t remember quite what you named some file that you haven t accessed for three months you can guess and use completion to find out if you re right Get used to using completion as means of asking questions not just as a way of saving keystrokes There are other characters you can type after C h and each one gets you help in a different way The ones you will use most often are C h k C h w and C h f Once you are more familiar with Emacs another one to try is C h a which prompts you for a string and then tells you about all the functions who have that string as part of their name the a means for apropos or about Another source of information is the Info documentation reader Info is too complex a subject to go into here but if you are interested in exploring it on your own type C h i and read the paragraph at the top of the screen It will tell you how get more help 8 10 Specializing Buffers Modes Emacs buffers have modes associated with
15. contents of the second line 2p There are some special modifiers that refer to positions that can change in the lifetime of the edit session The is the last line of the text To print the last line Sp The current line number uses the special modifier symbol 7 To display the current line using a modifier P This may appear to be unnecessary although it is very useful in the context of line number ranges To display the contents of the text from line 1 to line 2 the range needs to be supplied to ed 1 2p The first number refers to the starting line and the second refers to the finishing line The current line will subsequently be the second number of the command range If you want to display the contents of the file from the start to the current line O To display the contents from the current line to the end of the file 7 SP All that is left is to display the contents of the entire file which is left to you How can you delete the first 2 lines of the file 12d The command key a deletes the text line by line If you wanted to delete the entire contents you would issue 1 d If you have made to many changes and do not want to save the contents of the file then the best option is to quit the editor without writing the file beforehand Most users do not use ed as the main editor of choice The more modern editors offer a full edit screen and more flexible command sets Ed offers a good introduction t
16. man xclock If you re going to try running a few of your own xclocks you should probably read Sec tion 6 4 Multitasking to learn how to run them in addition to your current programs If you run an xclock in the foreground the usual way of running a program and want to get out of it type Figure 5 1 An annotated example of a standard X screen In this example the user is running t wm The standard clock has been replaced by a transparent clock called oclock E gt n a nawaBnoonosssomosonon ha Sink to ho 2823 2988 econ cooooscosocoson ins sorgeryeTy SSSSesesss sERBEzag Base Bor so 26 gE 22592 22593 22593 1 2 3 3 35 38 43 50 52 55 57 58 60 22388 22390 22399 cause I want a small space after it o rel A pA Hb returns Sokotra a patel like wet change the floatstyle for figure Floatstyletruled gt restylefloat f igure p r3 poponpppopopoppopppppproe 888 SRA y x rs ee a insi t s menu bar Fo Each word I heading of scrollbar tse hia adef Cat PLY docks atti recae ey up new files and By convention this is also the category that contains to quit the program begin figure tb I label x11 nenu bar begintoenter root menu 5 3 2 XTerm The window with a prompt in it something that probably looks like home larry is being controlled by a program called xterm xterm is a deceptively complicated program At first glance it doesn
17. sent to the process buffer exactly as if you had typed it in yourself C c M e sends the definition and then brings you to the process buffer to do some interactive work C c C 1 loads a file of Scheme code this one works from either the process buffer or the source code buffer And like other programming language modes hitting anywhere on a line of code correctly indents that line If you re at the prompt in the process buffer you can use M p and M n to move through your previous commands also known as the input history So if you are debugging the function rotate and have already applied it to arguments in the process buffer like so gt rotate ab cd e then you can get that command back by typing M p at the prompt later on There should be no need to retype long expressions at the Scheme prompt get in the habit of using the input history and you ll save a lot of time Emacs knows about quite a few programming languages C C Lisp and Scheme are just some Generally it knows how to indent them in intuitive ways 8 11 3 Mail Mode You can also edit and send mail in Emacs To enter a mail buffer type C x m You need to fill in the To and Subject fields and then use C n to get down below the separator line into the body of the message which is empty when you first start out Don t change or delete the separator line or else Emacs will not be able to send your mail it uses that line to distinguish
18. title f raise Buttonl frame f raise Buttonl icon f iconify Buttonl m window f iconify Button2 root f menu stuff Button2 2 licen f move Button2 m window f move Button2 title f move Button2 frame f move Button2 s frame f zoom Button2 s window f zoom Button3 root f menu x Button3 title lower Button3 Button3 frame lower icon f raiselower You can write your own functions this one gets used in the menu windowops near the end of this file Function raise n focus f raise f focus Okay below are the actual menus referred to in the mouse button section Note that many of these menu entries themselves call sub menus You can have as many levels of menus as you want but be aware that recursive menus don t work I ve tried it menu main Vanilla f title Emacs f menu emacs Logins f menu logins Xlock f menu xlock isc f menu misc This allows me to invoke emacs on several different machines See n the section on rhosts files for more information about how this works menu emacs Emacs tf title here usr bin emacs f nop phylo rsh phylo emacs d floss 0 amp geta rsh geta emacs d floss 0 amp darwin rsh darwin emacs d floss 0 amp ninja rsh ninja emacs d floss 0 amp indy rsh indy emacs d floss 0 amp oberlin I rsh cs obe
19. to refrain entirely from distribution of the Program If any portion of this section is held invalid or unenforceable under any particular circumstance the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances It is not the purpose of this section to induce you to infringe any patents or other prop erty right claims or to contest validity of any such claims this section has the sole 10 purpose of protecting the integrity of the free software distribution system which is implemented by public license practices Many people have made generous contri butions to the wide range of software distributed through that system in reliance on consistent application of that system it is up to the author donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice This section is intended to make thoroughly clear what is believed to be a conse quence of the rest of this License If the distribution and or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries so that distribution is permitted only in or among countries not thus excluded In such case this License incorporates the limitation as if written in the body of
20. 6 2 Time Saving With bash o e 59 6 2 1 Command Line Editing o 59 6 2 2 Command and File Completion 60 6 3 The Standard Input and The Standard Output 60 6 3 1 Unix Concepts 2 00 02 2 0000 61 6 3 2 Output Redirection o o e e 61 6 3 3 InputRedirectiOd e 62 6 3 4 Ehe Pipe lts a AA wed 63 6 4 Multitasking be Be oe e A ee 64 6 4 1 UsingJob Control o o o 64 6 4 2 The Theory of Job Control o o 69 6 5 Virtual Consoles Being in Many Places atOnce 70 Powerful Little Programs 73 TL The Power of UNIX a ek A A A EO RAPER 74 1 2 Operating on Files 2 6 26 2 8 er as ee A OR ee 74 1 3 System Statistics 600 ek woe ee BE Re EER A o 76 7 4 What s in the File 2 2 640 bea a de a a 78 7 5 Information Commands 0 0000 004 80 Editing files with Emacs 85 8 1 What s Emacs sois lara rr ale tok Sd 85 8 2 Getting Started Quickly in X o 88 8 3 Editing Many Files at Once o o 89 8 4 Ending an Editing Session e 90 80 TheMeta Key coli e eee bk Bt ee ee 91 8 6 Cutting Pasting Killing and Yanking 92 8 7 Searching and Replacing e 93 8 8 What s Really Going On Here o o 94 8 9 Asking Emacs for Help
21. Directory or Path to Working Directory But the evaluation of PWD takes place inside single quotes The single quotes serve to evaluate the expression inside them which itself evaluates the variable PWD If you just did export PS1 SPWD your prompt would constantly display the path to the current directory at the time that PS1 was set instead of constantly updating it as you change directories Well that s sort of confusing and not really all that important Just keep in mind that you need the quotes if you want the current directory displayed in your prompt You might prefer export PS1 SPWD gt oreven the name of your system export Ps1 hostname gt Let me dissect that last example a little further That last example used a new type of quoting the back quotes These don t protect something in fact you 1l notice that hostname doesn t appear anywhere in the prompt when you run that What actually happens is that the command inside the backquotes gets evaluated and the output is put in place of the backquotes and the command name Try echo 1s orwc ls As you get more experienced using the shell this technique gets more and more powerful There s a lot more to configuring your bashrc and not enough room to explain it here You can read the bash man page for more or ask questions of experienced Bash users Here is a complete bashrc for you to study it s fairly standard although the search pa
22. Repeat the last or command Repeats the last or in the Reverse direction When using the or commands a line will be cleared along the bottom of the screen You enter the search string followed by RETURN The string in the command or can be a regular expression A regular expression is a description of a set of characters The description is build using text intermixed with special characters The special characters in regular expressions are atches any single character except newlin Escapes any special characters atches 0 or More occurances of the atches exactly one of the enclosed atch of the next character must be atches characters preceding at the preceding character characters at the begining of the line end of the line Matches anything not enclosed after the not character l Matches a range of characters The only way to get use to the regular expression is to use them Following is a series of examples c pe c pe sto p car n xyz The atime only b aou rn Ver D F Ver 1 9 the ir re A Za z A Za z atc atc atc atc atc atc atc atc atc atc atc atc atc any line with Only as the only word in the line hes cope cape caper etc hes c pe c per etc hes stp stop stoop etc hes carton cartoon carmen etc hes xyz to the end of the line hes any line starting with The hes any line e
23. a complex symbolic manipulation package for Linux For any readers interested in the legalities of Linux this is allowed by the Linux license While the GNU General Public License reproduced in Appendix B covers the Linux kernel and would seemingly bar commercial software the GNU Library General Public License reproduced in Appendix C covers most of the computer code applications depend on This allows commercial software providers to sell their applications and withhold the source code Please note that those two documents are copyright notices and not licenses to use They do not regulate how you may use the software merely under what circumstances you can copy it and any derivative works To the Free Software Foundation this is an important distinction Linux doesn t involve any shrink wrap licenses but is merely protected by the same law that keeps you from photocopying a book Chapter 3 Getting Started This login session 13 99 but for you 11 88 You may have previous experience with MS DOS or other single user operating sys tems such as OS 2 or the Macintosh In these operating systems you didn t have to identify yourself to the computer before using it it was assumed that you were the only user of the system and could access everything Well Unix is a multi user operating system not only can more than one person use it at a time different people are treated differently To tell people apart Unix needs
24. a list of people who deserve to be recognized on every Linux system in the file usr src linux CREDITS 2 2 1 Linux Now The first number in Linux s version number indicates truly huge revisions These change very slowly and as of this writing February 1996 only version 1 is available The second number indicates less major revisions Even second numbers signify more stable dependable versions of Linuxwhile odd numbers are developing versions that are more prone to bugs The final version number is the minor release number every time a new version is released that may just fix small problems or add minor features that number is The source code of a program is what the programmer reads and writes It is later translated into unreadable machine code that the computer interprets increased by one As of February 1996 the latest stable version is 1 2 11 and the latest development version is 1 3 61 Linux is a large system and unfortunately contains bugs which are found and then fixed Although some people still experience bugs regularly it is normally because of non standard or faulty hardware bugs that effect everyone are now few and far between Of course those are just the kernel bugs Bugs can be present in almost every facet of the system and inexperienced users have trouble seperating different programs from each other For instance a problem might arise that all the characters are some type of gibberish is it
25. a telnet command I m presented with a login prompt for the remote system I can enter any username as long as I know the password and then use that remote system almost the same as if I was sitting there The normal way of exiting telnet is to logout on the remote system but another way is to type the escape character which as in the example above is usually Ctrl This presents me with a new prompt titled telnet gt I can now type quit and return land the connection to the other system will be closed and telnet will exit If you change your mind simply hit return and you ll be returned to the remote system If you re using X let s create a new xt erm for the other system we re travelling to Use the command xterm title lionsden e telnet lionsden This will create a new xterm window that s automatically running telnet If you do some thing like that often you might want to create an alias or shell script for it 10 5 Exchanging Files ftp remote system The normal way of sending files between Unix systems is ftp for the file transfer protocol After running the ftp command you ll be asked to login to the remote system much like telnet After doing so you ll get a special prompt an ftp prompt The cd command works as normal but on the remote system it changes your directory on the other system Likewise the 1s command will list your files on the remote system The two most important comma
26. all the function names that begin with insert and insert file is one of them So you complete the function name and read about how it works and then use M x insert file Ifyou re wondering whether it s also bound to a key youtypeC h w insert file and find out The more you know about Emacs s help facilities the more easily you can ask Emacs questions about itself The ability to do so combined with a spirit of exploration and a willingness to learn new ways of doing things can end up saving you a lot of keystrokes To order a copy of the Emacs user s manual and or the Emacs Lisp Programming man ual write to Free Software Foundation 675 Mass Ave Cambridge MA 02139 USA Both of these manuals are distributed electronically with Emacs in a form readable by using the Info documentation reader C h i but you may find it easier to deal with tree ware than with the online versions Also their prices are quite reasonable and the money goes to a good cause quality free software At some point you should type C h C c to read the copyright conditions for Emacs It s more interesting than you might think and will help clarify the concept of free software If you think the term free software just means that the program doesn t cost anything please do read that copyright as soon as you have time Chapter 9 I Gotta Be Me If God had known we d need foresight she would have given it to us 9 1 bas
27. and your CMOS clock a battery powered clock in your computer is probably set on local time This means that some program must read the time from your hardware clock and correct it to UCT After init is finished with its duties at boot up it goes on to its regularly scheduled activities init can be called the parent of all processes on a Unix system A process is simply a running program Since one program can be running two or more times there can be two or more processes for any particular program In Unix a process an instance of a program is created by a system call a service provided by the kernel called fork It s called fork since one process splits off into two seperate ones init forks a couple of processes which in turn fork some of their own On your Linux system what init runs are several instances of a program called getty getty is the program that will allow a user to login and eventually calls a program called login 3 3 The User Acts 3 3 1 Logging In The first thing you have to do to use a Unix machine is to identify yourself The login is Unix s way of knowing that users are authorized to use the system It asks for an account name and password An account name is normally similar to your regular name you should have already received one from your system administrator or created your own if you are the system administrator Information on doing this should be available in Installation and Getting S
28. as I were also logged in as the corresponding user given for that machine when I tried to do it The exact mechanism by which one runs a remote program is usually the rsh program It stands for remote shell and what it does is start up a shell on a remote machine and execute a specified command For example frobbo whoami trixie frobbo rsh floss life uiuc edu ls foo txt mbox url ps snax txt frobbo rsh floss life uiuc edu more snax txt snax txt comes paging by here User trixie at floss life uiuc edu who had the example rhosts shown previously explicitly allows trixie at frobbo hoola com to run programs as trixie from floss You don t have to have the same username on all machines to make a rhosts work right Use the 1 option to rsh to tell the remote machine what username you d like to use for logging in If that username exists on the remote machine and has a rhosts file with your current i e local machine and username in it then your rsh will succeed frobbo whoami trixie frobbo rsh 1 larry floss life uiuc edu ls Insert a listing of my directory on floss here This will work if user larry on floss life uiuc edu has a rhosts file which allows trixie from frobbo hoopla com to run programs in his account Whether or not they are the same person is irrelevant the only important things are the usernames the machine names and the entry in larry s rhosts file on floss Note th
29. calling up the program in the editor to make a small change and then exiting from the editor to run the program again ZZ will be a command you use often Actually ZZ is not an exact synonym for wq if you have not made any changes to the file you are editing since the last save ZZ will just exit from the editor whereas wq will redundantly save before exiting If you have hopelessly messed things up and just want to start all over again you can type q remember to press the key first If you omit the vi will not allow you to quit without saving A 3 5 What s next The ten commands you have just learned should be enough for your work However you have just scratched the surface of the vi editor There are commands to copy material from one place in a file to another to move material from one place in a file to another to move material from one file to another to fine tune the editor to your personal tastes etc In all there about 150 commands A 4 Advanced Vi Tutorial The advantage and power of vi is the ability to use it successfully with only knowing a small subset of the commands Most users of vi feel a bit awkward at the start however after a small amount of time they find the need for more command knowledge The following tutorial is assuming the user has completed the quick tutorial above and hence feels comfortable with vi It will expose some of the more powerful features of ex vi from copying text to ma
30. clicked that position is taken to be the midpoint of the data to be displayed Figure 5 4 An Athena type scroll bar is visible on the left of this xt erm window Next to it a Motif type scroll bar is visible on the net scape window la larry 16249 1 4 924 332 pp2 larry 16339 0 0 1 5 836 348 ppl F root 1 0 0 0 4 848 100 root 2 0 0 0 0 0 Q x2 SE root 8 0 0 0 3 840 84 root 33 0 0 1 2 804 300 root 35 0 0 0 2 828 60 root 38 0 0 0 7 884 172 root 48 0 0 0 4 920 96 root 50 0 0 0 3 868 88 root 0 0 0 5 872 116 root 0 0 1 3 1096 304 root 0 0 0 5 888 124 v04 root 0 0 0 4 892 112 s01 root 0 0 1 9 1784 448 root 1 1 19 5 11000 4520 root 0 0 1 2912 296 i root 0 0 4 4 1824 1032 root 0 0 39 19 912 9 root 0 0 4 1 2084 960 root 0 0 1 4 916 328 s02 root 0 0 4 1 2080 956 ppl steve 8 6 0 9 904 220 F mousehouse gt m key Mosaic or other estions evaluations 26 AA Chapter 6 Working with Unix A UNIX saleslady Lenore Enjoys work but she likes the beach more She found a good way To combine work and play She sells C shells by the seashore Unix is a powerful system for those who know how to harness its power In this chapter I ll try to describe various ways to use Unix s shell bash more efficently 6 1 Wildcards In the previous chapter you learned about the file maintence commands cp mv and rm Occasionally y
31. command more etc rc and that s the normal way of invoking 1t However that doesn t help the problem that 1s usr bin displays more information than you can see more lt ls usr bin won t work input redirection only works with files not commands You could do this home larry ls usr bin gt temp ls home larry more temp ls hnome larry rm temp 1s However Unix supplies a much cleaner way of doing that You can just use the com te mand 1s usr bin more The character indicates a pipe Like a water pipe a Unix pipe controls flow Instead of water we re controlling the flow of information A useful tool with pipes are programs called filters A filter is a program that reads the standard input changes it in some way and outputs to standard output more is a filter it reads the data that it gets from standard input and displays it to standard output one screen at a time letting you read the file more isn t a great filter because its output isn t suitable for sending to another program 4more is named because that s the prompt it originally displayed more In many versions of Linux the more command is identical to a more advanced command that does all that more can do and more Proving that computer programmers make bad comedians they named this new program less Other filters include the programs cat sort head and tail For instance if you wanted to read only the first ten lines of the output
32. deleted and placed into the unnamed buffer You can then paste the contents just as you had when copying the text into the desired position the LEFT of the cursor ne cursor EFT of the cursor add Delete the line and place it into named buffer a a4dd Delete 4 lines and place into named buffer a dw Delete a word and place into unnamed buffer See the section on modifying text for more examples of deleting text On the event of a system crash the named and unnamed buffer contents are lost but the edit buffers content can be recovered See Usefull commands A 4 4 Searching and replacing text vi has a number of search command You can search for individual charaters through to regular expressions The main two character based search commands are and t EC Fc tc Tc Find the next character c Moves RIGHT to the next Find the next character c Moves LEFT to the preceding Move RIGHT to character before the next c Move LEFT to the character following the preceding c Some clones this is the same as Fc Repeats the last f F t T command Same as but reverses the direction to the orginal command If the character you were searching for was not found vi will beep or give some other sort of signal vi allows you to search for a string in the edit buffer str str n N Searches Right and Down for the next occurance of str Searches Left and UP for the next occurance of str
33. driver version 4 11 with no serial options enabled tty00 at 0x03f8 irq 4 is a 16450 tty01 at 0x02f8 irq 3 is a 16450 tty02 at 0x03e8 irq 4 is a 16450 Here it found 3 serial ports A serial port is the equivalent of a DOS COM port and is a device normally used to communicate with modems and mice What it is trying to say is that serial port 0 COM1 has an address of 0x03 8 When it interrupts the kernel usually to say that it has data it uses IRQ 4 An IRQ is another means of a peripheral talking to the software Each serial port also has a controller chip The usual one for a port to have is a 16450 other values possible are 8250 and 16550 Next comes the parallel port driver A parallel port is normally connected to a printer and the names for the parallel ports in Linux start with 1p lp stands for Line Printer although in modern times it makes more sense for it to stand for Laser Printer However Linux will happily communicate with any sort of parallel printer dot matrix ink jet or laser 1p0 at 0x03bc polling That message says it has found one parallel port and is using the standard driver for it Linux next identifies your hard disk drives In the example system I m showing you mousehouse I ve installed two IDE hard disk drives hda WDC AC2340 325MB w 127KB Cache CHS 1010 12 55 hdb WDC AC2850F 814MB w 64KB Cache LBA CHS 827 32 63 The kernel now moves onto looking at your floppy drives In
34. extremely unfriendly Not only does it not ask you for confir mation but it will also delete things even if the whole command line wasn t correct This could actually be dangerous Consider the difference between these two commands home larry ls F toad frog home larry ls F frog toad home larry rm frog toad home larry and this home larry rm frog toad rm frog is a directory home larry ls F frog home larry As you can see the difference of one character made a world of difference in the LOW outcome of the command It is vital that you check your command lines before hitting return 4 4 3 A Forklift Can Be Very Handy mv i old name new name mv 1 filel file2 fileN new directory Finally the other file command you should be aware of is mv mv looks a lot like cp except that it deletes the original file after copying it It s a lot like using cp and rm together Let s take a look at what we can do home larry cp etc passwd home larry ls F asswd home larry mv passwd frog home larry ls F rog home larry mv frog report home larry ls F eport home larry ls F report rog Pp f home larry mkdir report r Zi f home larry As you can see mv will rename a file if the second parameter is a file If the second parameter is a directory mv will move the file to the new directory keeping it s shortname the same You should
35. fairly minor differences and are nothing to worry about If there is a severe difference between this book and your actual experience please inform me the author If you re the superuser the maintainer the installer of the system you also should have created a normal user account for yourself Please consult the installation manual s for this information If you aren t the superuser you should have obtained an account from the superuser You should have time and patience Learning Linux isn t easy most people find learn ing the Macintosh Operating System is easier Once you learn Linux things get a lot easier Unix is a very powerful system and it is very easy to do some complex tasks In addition this book assumes that you are moderately familiar with some computer terms Although this requirement isn t necessary it makes reading the book easier You should know about computer terms such as program and execution If you don t you might want to get someone s help with learning Unix 1 2 How to Avoid Reading This Book The best way to learn about almost any computer program is at your computer Most people find that reading a book without using the program isn t beneficial The best way to learn Unix and Linux is by using them Use Linux for everything you can Experiment Don t be afraid 1t s possible to mess things up but you can always reinstall Keep backups and have fun Unix isn t as intuitivel
36. files the files that end in BAT These shell scripts function like mini programs While they are usually much slower than a regular compiled program it is often true that they re easier to write Depending on the type of shell different files will be used at shell startup Type of Shel The file bash_profile is read and executed Non interactive The shell script is read and executed The file bashrc is read and executed 9 1 2 Startup Files Since most users want to have largely the same environment no matter what type of inter active shell they wind up with whether or not it s a login shell we ll start our configuration by putting a very simple command into our bash_profile source bashrc The source command tells the shell to interprete the argument as a shell script What it means for us is that everytime bash_profileis run bashrc is also run Now we ll just add commands to our bashrc If you ever want a command to only be run when you login add it to your bash_profile 9 1 3 Aliasing What are some of the things you might want to customize Here s something that I think about 90 of Bash users have put in their bashrc alias 11 1s 1 That command defined a shell alias called 11 that expands to the normal shell com mand ls 1 when invoked by the user So assuming that Bash has read that command in from your bashrc you can just type 11 to get the effect of ls 1 in
37. form of the same work You may not copy modify sublicense link with or distribute the Library except as expressly provided under this License Any attempt otherwise to copy modify sub license link with or distribute the Library is void and will automatically terminate your rights under this License However parties who have received copies or rights from you under this License will not have their licenses terminated so long as such parties remain in full compliance You are not required to accept this License since you have not signed it However nothing else grants you permission to modify or distribute the Library or its deriva tive works These actions are prohibited by law if you do not accept this License Therefore by modifying or distributing the Library or any work based on the Li brary you indicate your acceptance of this License to do so and all its terms and conditions for copying distributing or modifying the Library or works based on it Each time you redistribute the Library or any work based on the Library the recipi ent automatically receives a license from the original licensor to copy distribute link with or modify the Library subject to these terms and conditions You may not im pose any further restrictions on the recipients exercise of the rights granted herein You are not responsible for enforcing compliance by third parties to this License If as a consequence of a court judgment or allegatio
38. from 1s you could use ls usr bin head 6 4 Multitasking 6 4 1 Using Job Control Job control refers to the ability to put processes another word for programs essentially in the background and bring them to the foreground again That is to say you want to be able to make something run while you go and do other things but have it be there again when you want to tell it something or stop it In Unix the main tool for job control is the shell it will keep track of jobs for you if you learn how to speak its language The two most important words in that language are fg for foreground and bg for background To find out how they work use the command yes at a prompt hnome larry yes This will have the startling effect of running a long column of y s down the left hand side of your screen faster than you can follow To get them to stop you d normally type to kill it but instead you should type this time It appears to have stopped but there will be a message before your prompt looking more or less like this 1 Stopped yes It means that the process yes has been suspended in the background You can get it running again by typing fg at the prompt which will put it into the foreground again If you wish you can do other things first while it s suspended Try a few 1s s or something before you put it back in the foreground Once it s returned to the foreground the y s will start coming again as fast as b
39. in which this happens is Emacs s Scheme interaction features There are two different Scheme interfaces distributed with Emacs in version 19 at least xscheme and cmuscheme prompt gt ls usr lib emacs 19 19 lisp scheme usr lib emacs 19 19 lisp cmuscheme el usr lib emacs 19 19 lisp cmuscheme elc usr lib emacs 19 19 lisp scheme el usr lib emacs 19 19 lisp scheme elc usr lib emacs 19 19 lisp xscheme el usr lib emacs 19 19 lisp xscheme elc I happen to like the interface offered by cmuscheme much better than that offered by xscheme but the one Emacs will use by default is xscheme How can I cause Emacs to act in accordance with my preference I put this in my emacs 7 notice how the expression can be broken across two lines Lisp 7 ignores whitespace generally autoload run scheme cmuscheme Run an inferior Scheme the way I like it t The function autoload takes the name of a function quoted with for reasons having to do with how Lisp works and tells Emacs that this function is defined in a certain file The file is the second argument a string without the e1 or elc extension indicating the name of the file to search for in the Lload path The remaining arguments are optional but necessary in this case the third argument is a documentation string for the function so that if you call describe function on it you get some useful information The fourth argument tells Emacs that
40. it untouched ok command Y behaves like exec with the difference that for each selected file the user is asked to confirm the command if the answer starts with y or Y it is executed otherwise not and the action returns false 11 1 6 Operators There are a number of operators here there is a list in order of decreasing precedence expr forces the precedence order The parentheses must of course be quoted as they are mean ingful for the shell too expr not expr change the truth value of expression that is if expr is true it becomes false The excla mation mark needn t be escaped because it is followed by a white space expr1 expr2 expr1 a expr2 expr and expr2 all correspond to the logical AND operation which in the first and most common case is implied expr2 is not evaluated if expr is false expr o expr2 expr1 or expr2 correspond to the logical OR operation expr2 is not evaluated if exprl is true expr expr2 is the list statement both expr and expr2 are evaluated together with all side effects of course and the final value of the expression is that of expr2 11 1 7 Examples Yes find has just too many options I know But there are a lot of cooked instances which are worth to remember because they are usen very often Let s see some of them find name foo print finds all file names starting with foo If the string is embedded in the name probably it is more sensiti
41. just a side effect its real occupation is to evaluate The basic structure of the command is as follows find path expression This at least on the GNU version other version do not allow to specify more than one path and besides it is very uncommon the need to do such a thing The rough explanation of the command syntax is rather simple you say from where you want to start the search the path part with GNU find you can omit this and it will be taken as default the current directory and which kind of search you want to perform the expression part The standard behavior of the command is a little tricky so it s worth to note it Let s suppose that in your home directory there is a directory called garbage containing a file foobar You happily type find name foobar which as you can guess searches for files named foobar and you obtain nothing else than the prompt again The trouble lies in the fact that find is by default a silent command it just returns 0 if the search was completed with or without finding anything or a non zero value if there had been some problem This does not happen with the version you can find on Linux but it is useful to remember it anyway 11 1 2 Expressions The expression part can be divided itself in four different groups of keywords options tests actions and operators Each of them can return a true false value together with a side effect The difference among the grou
42. ki11 and can be used in the following way home larry kill 1 1 Stopped yes home larry That message about it being stopped again is misleading To find out whether it s still alive that is either running or frozen in a suspended state type jobs home larry jobs 1 Terminated yes home larry There you have it the job has been terminated It s possible that the jobs command showed nothing at all which just means that there are no jobs running in the background If you just killed a job and typing jobs shows nothing then you know the kill was suc cessful Usually it will tell you the job was terminated Now start yes running again like this hnome larry yes gt dev null If you read the section about input and output redirection you know that this is sending the output of yes into the special file dev null dev null is a black hole that eats any output sent to it you can imagine that stream of y s coming out the back of your computer and drilling a hole in the wall if that makes you happy After typing this you will not get your prompt back but you will not see that column of y s either Although output is being sent into dev nu11 the job is still running in the foreground As usual you can suspend it by hitting ctrl z Do that now to get the prompt back hnome larry yes gt dev null yes is running and we just typed ctrl z 1 Stopped yes gt dev null home la
43. library The former contains code derived from the library while the latter only works together with the library Note that it is possible for a library to be covered by the ordinary General Public License rather than by this special one Terms and Conditions for Copying Distribution and Mod ification 0 This License Agreement applies to any software library which contains a notice placed by the copyright holder or other authorized party saying it may be distributed under the terms of this Library General Public License also called this License Each licensee is addressed as you A library means a collection of software functions and or data prepared so as to be conveniently linked with application programs which use some of those functions and data to form executables The Library below refers to any such software library or work which has been distributed under these terms A work based on the Library means either the Li brary or any derivative work under copyright law that is to say a work containing the Library or a portion of it either verbatim or with modifications and or translated straightforwardly into another language Hereinafter translation is included without limitation in the term modification Source code for a work means the preferred form of the work for making mod ifications to it For a library complete source code means all the source code for all modules it
44. nn and nn which means a value strictly less than nn This is rather silly in the case of UIDs but it will turn handy with other tests Another useful option is type c which returns true if the file is of type c The mnemon ics for the possible choices are the same found in 1s so we have b when the file is a block special c when the file is character special d for directories p for named pipes for sym bolic links and s for sockets Regular files are indicated with f A related test is xtype which is similar to type except in the case of symbolic links If follow has not been given the file pointed at is checked instead of the link itself Completely unrelated is the test fstype type In this case the filesystem type is checked I think that the information is got from file etc mtab the one stating the mounting filesystems I am certain that types nfs tmp msdos and ext2 are recognized Tests inum nn and links nn check whether the file has inode number nn or nn links while size nn is true if the file has nn 512 bytes blocks allocated well not precisely for sparse files unallocated blocks are counted too As nowadays the result of 1s s is not always measured in 512 bytes chunks Linux for example uses 1k as the unit it is possible to append to nn the character b which means to count in butes or k to count in kilobytes Permission bits are checked through the test perm mode If mode has no leading sign
45. of the vi command set A 1 A Quick History of Vi Early text editors were line oriented and typically were used from dumb printing terminals A typical editor that operates in this mode is Ed The editor is powerful and efficient using 159 a very small amount of computer resources and worked well with the display equipment of the time vi offers the user a visual alternative with a significantly expanded command set compared with ed vi as we know it today started as the line editor ex In fact ex is seen as a special editing mode of vi although actually the converse is true The visual component of ex can be initiated from the command line by using the vi command or from within ex The ex vi editor was developed at the University of California at Berkeley by William Joy It was originally supplied as an unsupported utility until its official inclusion in the release of AT amp T System 5 Unix It has steadily become more popular even with the challenges of more modern full screen editors Due to the popularity of vi there exists many clone variants and versions can be found for most operation systems It is not the intention of this chapter to include all the com mands available under vi or its variants Many clones have expanded and changed the original behaviour of vi Most clones do not support all the original commands of vi If you have a good working knowledge of ed then vi offers a smaller learning curve to master Even if you
46. of the window fifty pixels from the right edge of the screen It s generally impossible to start the window off the screen although a window can be moved off the screen The main exception 1s when the window is very large The vertical distance from either the top or the bottom A positive vertical distance 1s measured from the top of the screen a negative vertical distance is measured from the bottom of the screen All four components get put together into a geometry string that looks like 503x73 78 0 That translates into a window 503 pixels long 73 pixels high put near the top right hand corner of the screen Another way of stating it is hsizexvsize hplace vplace Figure 5 2 Standard options for X programs Followed by geometry geometry of the window xterm geometry 80x24 0 90 display display you want the program to ap xterm display pear lionsden 0 0 fg the primary foreground color xterm fg yellow e the primary background color xterm bg blue 5 5 2 Display Every X application has a display that it is associated with The display is the name of the screen that the X server controls A display consists of three components e The machine name that the server is running on At stand alone Linux installations the server is always running on the same system as the clients In such cases the machine name can be omitted e The number of the server running on that machine Since any one machine could hav
47. on the terms of this License whose permissions for other licensees extend to the entire whole and thus to each and every part regardless of who wrote it Thus it is not the intent of this section to claim rights or contest your rights to work written entirely by you rather the intent is to exercise the right to control the distribution of derivative or collective works based on the Library In addition mere aggregation of another work not based on the Library with the Library or with a work based on the Library on a volume of a storage or distribution medium does not bring the other work under the scope of this License You may opt to apply the terms of the ordinary GNU General Public License instead of this License to a given copy of the Library To do this you must alter all the notices that refer to this License so that they refer to the ordinary GNU General Public License version 2 instead of to this License If a newer version than version 2 of the ordinary GNU General Public License has appeared then you can specify that version instead if you wish Do not make any other change in these notices Once this change is made in a given copy it is irreversible for that copy so the ordinary GNU General Public License applies to all subsequent copies and derivative works made from that copy This option is useful when you wish to copy part of the code of the Library into a program that is not a library 4 You may copy and dis
48. one of the most popular editors around partly because it s very easy for a complete beginner to get actual work done with it The classic Unix editor vi is covered in Appendix A To learn emacs you need to find a file of plain text letters numbers and the like copy it to your home directory we don t want to modify the actual file if it contains important information and invoke Emacs on the file home larry emacs READ Of course if you decided to co E py etc rc etc inittab or any other file substitute that file name for R EADM emacs rc E For instance if you cp etc rc rc then Invoking Emacs can have different effects depending on where where you do it From a plain console displaying only text characters Emacs will just take over the whole console lFor instance cp usr src linux README README 85 If you invoke it from X Emacs will actually bring up its own window I will assume that you are doing it from a text console but everything carries over logically into the X Windows version just substitute the word window in the places I ve written screen Also remeber that you have to move the mouse pointer into Emacs s window to type in it Your screen or window if you re using X should now resemble Figure 8 1 Most of the screen contains your text document but the last two lines are especially interesting if you re trying to learn Emacs
49. s That puts you in isearch mode Now start typing the word you are searching for gadfly But as soon as 6699 6699 you type the g you see that Emacs has jumped you to the first occurence of g in the buffer If the above quote is the entire contents of the buffer then that would be the first g of the word growing Now type the a of gadfly and Emacs leaps over to gasoline which contains the first occurence of a ga The d gets you to gadzooks and finally f gets you to gadfly without your having had to type the entire word What you are doing in an isearch is defining a string to search for Each time you add a character to the end of the string the number of matches is reduced until eventually you have entered enough to define the string uniquely Once you have found the match you are looking for you can exit the search with or any of the normal movement commands If you think the string you re looking for is behind you in the buffer then you should use C r which does an isearch backwards If you encounter a match but it s not the one you were looking for then hit C s again while still in the search This will move you forward to the next complete match each time you hit it If there is no next match it will say that the search failed but if you press C s again at that point the search will wrap around from the beginning of the buffer The reverse holds tru
50. shell and those lovely metacharacters are expanded So a test like name foo won t return what you want and you should either write name foo or name foo This is probably one of the most common mistakes made by careless users so write it in BIG letters on your screen Another problem is that like with 1s leading dots are not recognized To cope with this you can use test path pattern which does not worry about dot and slashes when comparing the path of the considered file with pattern 11 1 5 Actions I have said that actions are those which actually do something Well prune rather does not do something i e descending the directory tree unless depth is given It is usally find together with fstype to choose among the various filesystems which should be checked The other actions can be divided into two broad categories e Actions which print something The most obvious of these and indeed the default action of find is print which just print the name of the file s matching the other conditions in the command line and returns true A simple variants of print is fprint file which uses file instead of standard output Is lists the current file in the same format as 1s dils printf format behaves more or less like C function printf so that you can specify how the output should be formatted and fprintf file format does the same but writing on file These action too return true e Actions which execute someth
51. start of the previous line the end of the file the start of the file the current line number line of the screen le line of the screen bottom of the screen more cursor to column n The screen will automatically scroll when the cursor reaches either the top or the bottom of the screen There are alternative commands which can control scrolling the text lt Cntl lt Cntl lt Cntel lt Cnt I Vv vVvovV cao sm scroll scroll scroll scroll forward a screen backward a screen down hal down hal lf a screen lf a screen The above commands control cursor movement Some of the commands use a com mand modifier in the form of a number preciding the command This feature will usually repeat the command that number of times To move the cursor a number of positions left nl move the cursor n positions left If you wanted to enter a number or spaces in front of the some text you could use the command modifier to the insert command Enter the repeat number then i followed by the space then press ni insert some text and repeat the text n times The commands that deal with lines use the modifier to refer to line numbers The is a good example 1G Move the cursor to the first line vi has a large set of commands which can be used to move the cursor around the file Single character movement through to direct line placement of the cursor vi can also place the cursor a
52. t seem to do much but it actually has to do a lot of work xterm emulates a terminal so that regular text mode Unix applications work correctly It also maintains a buffer of information so that you can refer back to old commands To see how to use this look at Section 5 6 3 For much of this book we re going to be learning about the Unix command line and you ll find that inside your xterm window In order to type into xterm you usually have to move your mouse cursor possibly shaped like an X or an arrow into the xterm window However this behavior is dependent on the window manager One way of starting more programs under X is through an xterm Since X programs are standard Unix programs they can be run from normal command prompts such as xterms Since running a long term program from a xterm would tie up the xterm as long as the program was running people normally start X programs in the background For more information about this see Section 6 4 5 4 Window Managers On Linux there are two different window managers that are commonly used One of them called t wm is short for Tab Window Manager It is larger than the other window manager usually used fvwm fvwm stands for F Virtual Window Manager the author neglected to tie down exactly what the f stood for Both twm and fvwm are highly configurable which means I can t tell you exactly what keys do what in your particular setup To learn about twm
53. talks about the Free Software Foundation and the GNU Project Chapter 3 talks about how to start and stop using your computer and what happens at these times Much of it deals with topics not needed for using Linux but still quite useful and interesting Chapter 4 introduces the Unix shell This is where people actually do work and run programs It talks about the basic programs and commands you must know to use Unix Chapter 5 covers the X Window System X is the primary graphical front end to Unix and some distributions set it up by default Chapter 6 covers some of the more advanced parts of the Unix shell Learning techniques described in this chapter will help make you more efficent Chapter 7 has short descriptions of many different Unix commands The more tools a user knows how to use the quicker he will get his work done Chapter 8 describes the Emacs text editor Emacs is a very large program that integrates many of Unix s tools into one interface Chapter 9 talks about ways of customizing the Unix system to your personal tastes Chapter 10 investigates the ways a Unix user can talk to other machines around the world including electronic mail and the World Wide Web Chapter 11 describes some of the larger harder to use commands Chapter 12 talks about easy ways to avoid errors in Unix and Linux 1 4 Linux Documentation This book The Linux Users Guide is intended for the Unix beginner Luckily the Linux Doc
54. ten lines of stdin if no files are specified on the command line Any numeric option will be taken as the number of lines to print so head 15 frog will print the first fifteen lines of the file frog tail lines filel file2 fileN Like head tail will display only a fraction of the file Naturally tail will display the end of the file or the last ten lines that come through stdin tail also accepts a option specifying the number of lines file filel file2 fileN The file command attempts to identify what format a particular file is written in Since not all files have extentions or other easy to identify marks the file command performs some rudimentary checks to try and figure out exactly what it contains Be careful though because it is quite possible for f i le to make a wrong identification 7 5 Information Commands This section discusses the commands that will alter a file perform a certain operation on the file or display statistics on the file grep nvwx number expression filel file2 fileN One of the most useful commands in Unix is grep the generalized regular expression parser This is a fancy name for a utility which can only search a text file The easiest way to use grep is like this home larry cat animals A the tiger a fearsome beast with large teeth I also like the lion it s really neat t home larry grep iger animals he tiger a fearsome beast
55. the mouse in a window before that window gets focus Usually under X if your mouse cursor wanders from a window focus will be lost and you ll no longer be able to type there Note however that it is possible to configure both twm and fvwm so that you must click on or in a window to gain focus and click somewhere else to lose it identical to the behavior of Microsoft Windows Either discover how your window manager is configured by trial and error or consult local documentation 5 4 3 Moving Windows Another very configurable thing in X is how to move windows around In my personal configuration of t wm there are three different ways of moving windows around The most obvious method is to move the mouse cursor onto the title bar and drag the window around the screen Unfortunately this may be done with any of the left right or middle buttons To drag move the cursor above the title bar and hold down on the button while moving the mouse Most likely your configuration is set to move windows using the left mouse buttons Another way of moving windows may be holding down a key while dragging the mouse For instance in my configuration if I hold down the key move the cursor above a window I can drag the window around using the left mouse button Again you may be able to understand how the window manager is configured by trial and error or by seeing local documentation Alternatively if you want to try to interpret the window
56. the tar file In this case we could write rsh beta dd if dev rst0 ibs 8k obs 20k tar xvBf to do in a single pass the whole operation In this case we have used the facilities of rsh to perform the reading from the tape Input and output sizes are set to the default for these operations that is 8KB for reading from a tape and 20KB for writing to ethernet from the point of view of the other side of the tar there is the same flow of bytes which could be got from the tape except the fact that it arrives in a rather erratic way and the option B is necessary I forgot I don t think at all that dd is an acronym for data duplicator but at least this is a nice way to remember its meaning 11 4 sort the data sorter 11 4 1 Introduction 11 4 2 Options 11 4 3 Examples Chapter 12 Errors Mistakes Bugs and Other Unpleasantries Unix was never designed to keep people from doing stupid things because that policy would also keep them from doing clever things Doug Gwyn 12 1 Avoiding Errors Many users report frustration with the Unix operating system at one time or another fre quently because of their own doing A feature of the Unix operating system that many users love when they re working well and hate after a late night session is how very few commands ask for confirmation When a user is awake and functioning they rarely think about this and it is an assest since it let s them work smoother Howev
57. these names mean right now Let s cover what each of these utilities do seperately and then I ll give some examples of how to use them together 7 2 Operating on Files In addition to the commands like cd mv and rm you learned in Chapter 4 there are other commands that just operate on files but not the data in them These include touch chmod du and df All of these files don t care what is in the file the merely change some of the things Unix remembers about the file Some of the things these commands manipulate e The time stamp Each file has three dates associated with it The three dates are the creation time when the file was created the last modification time when the file was last changed and the last access time when the file was last read e The owner Every file in Unix is owned by one user or the other e The group Every file also has a group of users it is associated with The most common group for user files is called users which is usually shared by all the user account on the system e The permissions Every file has permissions sometimes called privileges associ ated with it which tell Unix who can access what file or change it or in the case Please note that the short summaries on commands in this chapter are not comprehensive Please consult the command s manpage if you want to know every option Older filesystems in Linux only stored one date since they were derived from Minix
58. they are logged into the same machine Let s take a look at one more command to understand what P IDs are The ps command will list all running processes including your shell Try it out It also has a few options the most important of which to many people are a u and x The a option will list processes belonging to any user not just your own The x switch will list processes that don t have a terminal associated with them Finally the u switch will give additionally information This only makes sense for certain system programs that don t have to talk to users through a keyboard about the process that is frequently useful To really get an idea of what your system is doing put them all together ps aux You can then see the process that uses the more memory by looking at the 3MEM column and the most CPU by looking at the CPU column The TIME column lists the total amount of CPU time used Another quick note about PIDs ki11 in addition to taking options of the form job will take options of raw PIDs So puta yes gt dev null in the background run ps and look for yes Then type kill PID If you start to program in C on your Linux system you will soon learn that the shell s job control is just an interactive version of the function calls fork and execl This is too complex to go into here but may be helpful to remember later on when you are programming and want to run multiple processes from a single p
59. things to your screen Remember to see some of the stranger and perhaps less useful options use the man command man cat cat will accept input from stdin if no files are specified on the command line more l linenumber filel file2 fileN more is much more useful and is the command that you ll want to use when browsing ASCII text files The only interesting option is 1 which will tell more that you aren t interested in treating the character as a new page character more will start on a specified linenumber Since more is an interactive command I ve summarized the major interactive com mands below Spacebar Moves to the next screen of text a This will scroll the screen by 11 lines or about half a normal 25 line screen Searches for a regular expression While a regular expression can be quite complicated you can just type in a text string to search for For example toad return would search for the next occurence of toad in your current file A slash followed by a return will search for the next occurence of what you last searched for This will also search for the next occurence of your regular expression BD If you specified more than one file on the command line this will move to the next file P This will move the the previous file a Exits from more head lines filel file2 fileN head will display the first ten lines in the listed files or the first
60. this example the machine has two drives drive A is a 5 1 4 inch drive and drive B is a 3 1 2 inch drive Linux calls drive A d0 and drive B fdl Floppy drive s fd0 is 1 44M fdl is 1 2M floppy FDC 0 is a National Semiconductor PC87306 The next driver to start on my example system is the SLIP driver It prints out a message about its configuration SLIP version 0 8 3 NET3 019 NEWTTY dynamic channels max 256 6 bit encapsulation enabled CSLIP code copyright 1989 Regents of the University of California 14 The kernel also scans the hard disks it found It will look for the different partitions 15 on each of them A partition is a logical separation on a drive that is used to keep operating systems from interfering with each other In this example the computer had two hard disks hda hdb with four partitions and one partition respectively Partition check hda hdal hda2 hda3 hda4 hdb hdb1 Finally Linux mounts the root partition The root partition is the disk partition where the Linux operating system resides When Linux mounts this partition it is making the partition available for use by the user VFS Mounted root ext2 filesystem readonly Chapter 4 The Unix Shell Making files is easy under the UNIX operating system Therefore users tend to create numerous files using large amounts of file space It has been said that the only standard thing about all UNIX sy
61. to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice This section is intended to make thoroughly clear what is believed to be a conse quence of the rest of this License If the distribution and or use of the Library is restricted in certain countries either by patents or by copyrighted interfaces the original copyright holder who places the Library under this License may add an explicit geographical distribution limitation excluding those countries so that distribution is permitted only in or among countries not thus excluded In such case this License incorporates the limitation as if written in the body of this License The Free Software Foundation may publish revised and or new versions of the Li brary General Public License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns Each version is given a distinguishing version number If the Library specifies a version number of this License which applies to it and any later version you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation If the Library does not specify a license version number you may choose any version ever published by the Free Software Foundation 14 If you wish to incorporate parts of the Library into othe
62. to most of the Free Software Foundation s software and to any other program whose authors commit to using it Some other Free Software Foun dation software is covered by the GNU Library General Public License instead You can apply it to your programs too When we speak of free software we are referring to freedom not price Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software and charge for this service if you wish that you receive source code or 177 can get it if you want it that you can change the software or use pieces of it in new free programs and that you know you can do these things To protect your rights we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights These restrictions translate to certain responsibilities for you if you distribute copies of the software or if you modify it For example if you distribute copies of such a program whether gratis or for a fee you must give the recipients all the rights that you have You must make sure that they too receive or can get the source code And you must show them these terms so they know their rights We protect your rights with two steps 1 copyright the software and 2 offer you this license which gives you legal permission to copy distribute and or modify the software Also for each author s protection and ours we want to make certa
63. want to contact whoever you got Linux from eventually you re bound to encounter someone who either has electronic mail or sells Linux commercially and therefore wants to remove as many bugs as possible Remember though that no one is under any obligation to fix any bugs unless you have a contract When you send a bug report in include all the information you can think of This includes A description of what you think is incorrect For instance I get 5 when I com pute 2 2 or It says segmentation violation core dumped It is important to say exactly what is happening so the maintainer can fix your bug e Include any relevant environment variables e The version of your kernel see the file proc version and your system libraries see the directory 1ib if you can t decipher it send a listing of 1ib e How you ran the program in question or if it was a kernel bug what you were doing at the time e All peripheral information For instance the command w may not be displaying the current process for certain users Don t just say w doesn t work when for a certain user The bug could occur because the user s name is eight characters long or when he is logging in over the network Instead say w doesn t display the current process for user greenfie when he logs in over the network e And remember be polite Most people work on free software for the fun of it and because they have big h
64. we ve suceeded or what we should improve on You can contact the author at leg andrew cmu edu and or Matt Welsh at mdw cs cornell edu 1 5 Operating Systems An operating system s primary purpose is to support programs that actually do the work you re interested in For instance you may be using an editor so you can create a document This editor could not do its work without help from the operating system it needs this help for interacting with your terminal your files and the rest of the computer Tf all the operating system does is support your applications why do you need a whole book just to talk about the operating system There are lots of routine maintenance activ ities apart from your major programs that you also need to do In the case of Linux the operating system also contains a lot of mini applications to help you do your work more efficently Knowing the operating system can be helpful when you re not working in one huge application Operating systems frequently abbreviated as OS can be simple and minimalist like DOS or big and complex like OS 2 or VMS Unix tries to be a middle ground While it supplies more resources and does more than early operating systems it doesn t try to do everything Unix was originally designed as a simplification of an operating system named Multics The original design philosophy for Unix was to distribute functionality into small parts the programs That way you ca
65. when you installed Linux you were prompted for some very witty name It isn t very important but whenever it comes up Ill be using mousehouse or rarely Lionsden when I need to use a second system for clarity or contrast After entering larry and pressing return I m faced with the following mousehouse login larry Password What Linux is asking for is your password When you type in your password you won t be able to see what you type Type carefully it is possible to delete but you won t be able to see what you are editing Don t type too slowly if people are watching they ll be able to learn your password If you mistype you ll be presented with another chance to login LOW If you ve typed your login name and password correctly a short message will appear called the message of the day This could say anything the system adminstrator decides what it should be After that a prompt appears A prompt is just that something prompting you for the next command to give the system It should look something like this home larry If you ve already determined you re using X you ll probably see a prompt like the one above in a window somewhere on the screen A window is a rectangular box To type into the prompt move the mouse cursor it probably looks like a big x or an arrow using the mouse into the window 3 3 2 Leaving the Computer Do not just turn off the computer You ris
66. with large teeth home larry One disadvantage of this is although it shows you all the lines containing your word it doesn t tell you where to look in the file no line number Depending on what you re doing this might be fine For instance if you re looking for errors from a programs output you might trya out grep error where a out is your program s name If you re interested in where the match es are use the n switch to grep to tell it to print line numbers Use the v switch if you want to see all the lines that don t match the specified expression Another feature of grep is that it matches only parts of a word like my example above where iger matched tiger To tell grep to only match whole words use the w and the x switch will tell grep to only match whole lines If you don t specify any files grep will examine stdin wc clw filel file2 fileN wc stands for word count It simply counts the number of words lines and characters in the file s If there aren t any files specified on the command line it operates on stdin The three parameters clw stand for character line and word respectively and tell wc which of the three to count Thus wc cw will count the number of characters and words but not the number of lines wc defaults to counting everything words lines and characters One nice use of wc is to find how many files are in the present directory 1s wc w If you wa
67. 1 The path an Intel PC takes to get to a shell prompt init may or may not start the X Window System If it does xdm runs Otherwise get ty runs the kernel LILO gt Linux gt init BIOS login getty xdm the X Window System bash e the shell Linux then looks at the type of hardware it s running on It wants to know what type of hard disks you have whether or not you have a bus mouse whether or not you re on a net work and other bits of trivia like that Linux can t remember things between boots so it has to ask these questions each time it starts up Luckily it isn t asking you these questions it is asking the hardware During boot up the Linux kernel will print variations on several messages You can read about the messages in Section 3 4 This query process can some cause problems with your system but if it was going to it probably would have when you first installed Linux If you re having problems consult your distribution s documentation The kernel merely manages other programs so once it is satisfied everything is okay it must start another program to do anything useful The program the kernel starts is called init Notice the difference in font Things in this font are usually the names of programs files directories or other computer related items After the kernel starts init it never star
68. 18 12 9 191 amp The prompt inside the mail program is an ampersand amp It allows a couple of simple commands and will give a short help screen if you type and then return The basic commands for mail are t message list Show or type the messages on the screen d message list Delete the messages s message list file Save the messages into file r message list Reply to the messages that is start composing a new message to who ever sent you the listed messages q Quit and save any messages you didn t delete into a file called mbox in your home directory What s a message list It consists of a list of integers seperated by spaces or even a range such as 2 4 which is identical to 2 3 4 You can also enter the username of the sender so the command t sam would type all the mail from Sam If a message list is omitted it is assumed to be the last message displayed or typed There are several problems with the mail program s reading facilities First of all if a message is longer than your screen the mail program doesn t stop You ll have to save it and use more on it later Second of all it doesn t have a very good interface for old mail if you wanted to save mail and read it later Emacs also has a facility for reading mail called rmai 1 but it is not covered in this book Additionally most Linux systems have several other mailreaders available such as elmor pine 10 2 More than En
69. Directories Moving Information oaa a 4 4 1 cp LikeaMonk 0 2002000004 4 4 2 Pruning Back with rm o ee ee 4 4 3 A Forklift Can Be Very Handy 5 The X Window System 5 1 5 2 Starting and Stopping the X Window System SS AA A ek me Bde ee es ae XL JEM A oye he a hehe rio e ros What is The X Window System 20008 44 5 3 What s This on my Screen o o 45 IL ACTO doc a es ape ee oe oo ee ed 45 S32 CAC va noth Bie phase Modes ete o had va Bes 46 5 4 Window Managers so sa saosa iea a asi 00020000 eae 47 5 4 1 When New Windows are Created 47 DAD MBOCUS 2 a a a A ae 48 5 4 3 Moving WindoWS e 48 DAD DEP a co a e A E A 49 DAD ICONO ee AE AR REA 49 DADO RESIZING e o E a AA See A 50 54 7 Maximization 2 4 5 o 2 ee ba ees Pa EE we ees 50 DALE Menus 04 ob ek a SA Ae OR eS ed 50 D X Attrbutes to 4 4 acts e Pe eee a Bie Sgt tS 51 A E IN 51 5 3 2 A cece Beate peng Boas Seg gt peaks a es oe Beaded a 52 5 0 Common Fear Si se 6b gee abe Seb et ee ae ae eet 53 3 6 1 Buttons ses soerah E a o A EN Ae eb Gare Be 53 3 0 2 Menu Bars pitidos A els Be ete A ae BEA 53 26 3 Croll Bars eis ie A abe Pee aS ee 54 Working with Unix 57 A yA ee es Ae a ee Pe aS 57 6 1 1 What Really Happens o 58 6 1 2 The Question Mark s be sanace anea h gpa 00 eee 59
70. If the work during execution displays copyright notices you must include the copyright notice for the Library among them as well as a reference directing the user to the copy of this License Also you must do one of these things a Accompany the work with the complete corresponding machine readable source code for the Library including whatever changes were used in the work which must be distributed under Sections 1 and 2 above and if the work is an ex ecutable linked with the Library with the complete machine readable work that uses the Library as object code and or source code so that the user can modify the Library and then relink to produce a modified executable containing the modified Library It is understood that the user who changes the contents of definitions files in the Library will not necessarily be able to recompile the application to use the modified definitions b Accompany the work with a written offer valid for at least three years to give the same user the materials specified in Subsection 6a above for a charge no more than the cost of performing this distribution c If distribution of the work is made by offering access to copy from a designated place offer equivalent access to copy the above specified materials from the same place d Verify that the user has already received a copy of these materials or that you have already sent this user a copy For an executable the required form of the work tha
71. If you use many C n s to move down screenfuls of text be very ashamed and use C v forever after If you are using repeated C p s to move up screenfuls be embarrassed to show your face and use M v instead If you are nearing the end of a line and you realize that there s a mispelling or a word left out somewhere earlier in the line don t use or to get back to that spot That would require retyping whole portions of perfectly good text Instead use combinations of M b C b and C f to move to the precise location of the error fix it and then use C e to move to the end of the line again When you have to type in a filename don t ever type in the whole name Just type in enough of it to identify it uniquely and let Emacs s completion finish the job by hitting or Why waste keystrokes when you can waste CPU cycles instead If you are typing some kind of plain text and somehow your auto filling or auto wrapping has gotten screwed up use M q which is i11 paragraph in common text modes This will adjust the paragraph you re in as if it had been wrapped line by line but without your having to go mess around with it by hand M q will work from inside the paragraph or from its very beginning or end Sometimes it s helpful to use C x u undo which will try to undo the last change s you made Emacs will guess at how much to undo usually it guesses very intelligently Calling it repeatedly will und
72. RENDERED INACCU RATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBIL ITY OF SUCH DAMAGES How to Apply These Terms to Your New Libraries If you develop a new library and you want it to be of the greatest possible use to the public we recommend making it free software that everyone can redistribute and change You can do so by permitting redistribution under these terms or alternatively under the terms of the ordinary General Public License To apply these terms attach the following notices to the library It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty and each file should have at least the copyright line and a pointer to where the full notice is found one line to give the library s name and a brief idea of what it does Copyright C year name of author This library is free software you can redistribute it and or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation either version 2 of the License or at your option any later version This library is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABIL ITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU Library General Public License for more deta
73. S the kernel supplies functions for running programs to use and schedules them to be run It basically says program A can get so much time program B can get this much time and so on A kernel is always running it is the first program to start when the system is turned on and the last program to do anything when the system is halted Chapter 2 What s Unix anyway Ken Thompson has an automobile which he helped design Unlike most automobiles it has neither speedometer nor gas gage nor any of the numerous idiot lights which plague the modern driver Rather if the driver makes any mistake a giant lights up in the center of the dashboard The experienced driver he says will usually know what s wrong 2 1 Unix History In 1965 Bell Telephone Laboratories Bell Labs a division of AT amp T was working with General Electric and Project MAC of MIT to write an operating system called Multics To make a long story slightly shorter Bell Labs decided the project wasn t going anywhere and broke out of the group This left Bell Labs without a good operating system Ken Thompson and Dennis Ritchie decided to sketch out an operating system that would meet Bell Labs needs When Thompson needed a development environment 1970 to run on a PDP 7 he implemented their ideas As a pun on Multics Brian Kernighan an other Bell Labs researcher gave the system the name Unix Later Dennis Ritchie invented the C progra
74. Should Have Done Before Reading This Book 3 1 2 Howto Avoid Reading This Book 0004 4 1 3 Howto Read This Book o e eee eee 5 1 4 Linux Documentation 0 2 00 ee eee ees 6 1 4 1 Other Linux Books o o e 6 14 2 HOWTOS 224 0 8 oe Se ae e Pe ee de EE 6 1 4 3 What s the Linux Documentation Project 7 LS Operating Systems ye ata a A ce ee le eh 7 2 What s Unix anyway 9 201 UniX HISO aes Goose we es A a Seaweed doe Me eed 9 2 2 Linux History 33 ee ce ae Ra ee ee PR ae eae ons 10 2261 CLIM UENOW d chi ti See deg o GAN ea Gad Ga Gl gel 11 2 2 2 A Few Questions and Answers a eee 12 2 2 3 Commercial Software in Linux o 12 3 Getting Started 3 1 3 2 3 3 3 4 Power to the Computer e Linux Takes OVer os a e a eS oa The User Alias a RA A Eee A iS 3 32 Logging In can ee koh ee eRe EA E 3 3 2 Leaving the Computer 3 3 3 Turning the Computer Off o o Kernel Messages aci A A Bik ci Sle aed 4 The Unix Shell 4 1 4 2 4 3 4 4 Unix Commands i as ec 08855 a a e a ee 4 1 1 A Typical Unix Command Helping Yourself nise snara a eh te Bee AAA e ii Storing Information oaa e 4 3 1 Looking at Directories with 1s e 4 3 2 The Current Directory and cd o a 4 3 3 Creating and Removing
75. The Linux Users Guide 1993 1994 1996 Larry Greenfield All you need to know to start using Linux a free Unix clone This manual covers the basic Unix commands as well as the more specific Linux ones This manual is in tended for the beginning Unix user although it may be useful for more experienced users for reference purposes UNIX is a trademark of X Open MS DOS and Microsoft Windows are trademarks of Microsoft Corporation OS 2 and Operating System 2 are trademarks of IBM X Window System is a trademark of X Consortium Inc Motif is a trademark of the Open Software Foundation Linux is not a trademark and has no connection to UNIX Unix System Labratories or to X Open Please bring all unacknowledged trademarks to the attention of the author Copyright Larry Greenfield 427 Harrison Avenue Highland Park NJ 08904 legt t andrew cmu edu Permission is granted to make and distribute verbatim copes of this manual provided the copyright notice and this permission notice are preserved on all copies Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying provided also that the sections that reprint The GNU General Public License The GNU Library General Public License and other clearly marked sections held under seperate copyright are reproduced under the conditions given within them and provided that the entire resulting derived work is distribu
76. a bug or a feature Surprisingly this is a feature the gibberish is caused by certain control sequences that somehow appeared Hopefully this book will help you to tell the different situations apart 2 2 2 A Few Questions and Answers Before we embark on our long voyage let s get the ultra important out of the way Question Just how do you pronounce Linux Answer According to Linus it should be pronounced with a short ih sound like print mInImal etc Linux should rhyme with Minix another Unix clone It should not be pronounced like American pronounciation of the Peanuts character Linus but rather LIH nucks And the u is sharp as in rule not soft as in ducks Linux should almost rhyme with cynics Question Why work on Linux Answer Why not Linux is generally cheaper or at least no more expensive than other operating systems and is frequently less problematic than many commercial systems It might not be the best system for your particular applications but for someone who is interested in using Unix applications available on Linux it is a high performance system 2 2 3 Commercial Software in Linux There is a lot of commercial software available for Linux Starting with Motif a user interface for the X Window System that vaguely resembles Microsoft Windows Linux has been gaining more and more commercial software These days you can buy anything from Word Perfect a popular word processor to Maple
77. a common way of adding options that you use every time you call a program Notice the comments with the character in Figure 9 1 3 Whenever a appears the shell ignores the rest of the line You might have noticed a few odd things about them First of all I leave off the quotes in a few of the aliases like pu Strictly speaking quotes aren t necessary when you only have one word on the right of the equal sign It never hurts to have quotes either so don t let me get you into any bad habits You should certainly use them if you re going to be aliasing a command with options and or arguments alias rf refrobnicate verbose prolix wordy o foo out Also the final alias has some funky quoting going on alias ed2 emacs d floss 0 fg grey95 bg grey50 As you might have guessed I wanted to pass double quotes in the options themselves so I had to quote those with a backslash to prevent bash from thinking that they signaled the end of the alias Finally I have actually aliased two common typing mistakes mroe and moer to the command I meant to type more Aliases do not interfere with your passing arguments to a program The following works just fine home larry mroe hurd txt In fact knowing how to make your own aliases is probably at least half of all the shell customization you 1l ever do Experiment a little find out what long commands you find yourself typing frequently and make aliases for the
78. a computer e Keep track of your present directory Sometimes the prompt you re using doesn t display what directory you are working in and danger strikes It is a sad thing to read a post on comp unix admin about a root user who was in instead of tmp For example mousehouse gt pwd etc mousehouse gt ls tmp passwd mousehouse gt rm passwd The above series of commands would make the user very unhappy seeing how they have just removed the password file for their system Without it people can t login 1 A international discussion group on Usenet which talks about administring Unix computers 12 2 What to do When Something Goes Wrong 12 3 Not Your Fault Unfortunately for the programmers of the world not all problems are caused by user error Unix and Linux are complicated systems and all known versions have bugs Sometimes these bugs are hard to find and only appear under certain circumstances First of all what is a bug An example of a bug is if you ask the computer to compute 5 3 and it tells you 7 Although that s a trivial example of what can go wrong most bugs in computer programs involve arithmetic in some extremely strange way 12 3 1 When Is There a Bug If the computer gives a wrong answer verify that the answer is wrong or crashes it is a bug If any one program crashes or gives an operating system error message it is a bug If a command never finishes running can be a bug but yo
79. a user to identify him or herself by a process called logging in When you first turn on the computer a complex process takes place before the computer is ready for someone to use it Since this guide is geared towards Linux I ll tell you what happens during the Linux boot up sequence If you re using Linux on some type of computer besides an Intel PC some things in this chapter won t apply to you Mostly they ll be in Section 3 1 If you re just interested in using your computer you can skip all the information in the chapter except for Section 3 3 From here on in this book I shall be using the masculine pronouns to identify all people This is the standard English convention and people shouldn t take it as a statement that only men can use computers 15 3 1 Power to the Computer The first thing that happens when you turn an Intel PC on is that the BIOS executes BIOS stands for Basic Input Output System It s a program permenantly stored in the computer on read only chips It performs some minimal tests and then looks for a floppy disk in the first disk drive If it finds one it looks for a boot sector on that disk and starts executing code from it if any If there is a disk but no boot sector the BIOS will print a message like Non system disk or disk error Removing the disk and pressing a key will cause the boot process to continue If there isn t a floppy disk in the drive the BIOS looks for a mast
80. amed ct and gives you another prompt to work with Remember Unix is case sensitive CAT is a misspelling e You could have also placed whitespace before the command like this home larry cat iii This produces the correct result and runs the cat program e You might also press return on a line by itself Go right ahead it does absolutely nothing I assume you are now in cat Hopefully you re wondering what it is doing No it is not a game cat is a useful utility that won t seem useful at first Type anything and hit return What you should have seen is home larry cat Help I m stuck in a Linux program Help I m stuck in a Linux program The slanted text indicates what I typed to cat What cat seems to do is echo the text right back at yourself This is useful at times but isn t right now So let s get out of this program and move onto commands that have more obvious benefits To end many Unix commands type Ctrl d Ctrl d is the end of file character or EOF for short Alternatively it stands for end of text depending on what book you read I ll refer to it as an end of file It is a control character that tells Unix programs that you or another program is done entering data When cat sees you aren t typing anything else it terminates For a similar idea try the program sort As its name indicates it is a sorting program If you type a couple of lines then press Ctrl a it wil
81. and then it will print out our silly sentence Thus the command cat listing fox gt listandfox will create a new file containing the contents of both list ing and fox 6 3 3 Input Redirection Like redirecting standard output it is also possible to redirect standard input Instead of a program reading from your keyboard it will read from a file Since input redirection 3For impatient readers the command you might want to try is more However there s still a bit more to talk about before we get there is related to output redirection it seems natural to make the special character for input redirection be lt It too is used after the command you wish to run This is generally useful if you have a data file and a command that expects input from standard input Most commands also let you specify a file to operate on so lt isn t used as much in day to day operations as other techniques 6 3 4 The Pipe Many Unix commands produce a large amount of information For instance it is not un common for a command like 1s usr bin to produce more output than you can see on your screen In order for you to be able to see all of the information that a command like 4 more will ls usr bin it s necessary to use another Unix command called more pause once every screenful of information For instance more lt etc rc will display the file etc rc just like cat etc rc would except that more will let you read it more also allows the
82. anguage specially made for twm believe it or not The main thing people like to play with in their twmrc is window style colors and such and making cool menus so here s an example t wmrc that does that Set colors for the various parts of windows This has a great impact on the feel of your environment Color BorderColor OrangeRed BorderTileForeground Black BorderTileBackground Black TitleForeground black TitleBackground gold MenuForeground black MenuBackground LightGrey MenuTitleForeground LightGrey MenuTitleBackground LightSlateGrey MenuShadowColor black IconForeground DimGray IconBackground Gold IconBorderColor OrangeRed IconManagerForeground black 4This is one of the harsh facts about init files they generally each have their own idiosyncratic command language This means that users get very good at learning command languages quickly I suppose that it would have been nice if early Unix programmers had agreed on some standard init file format so that we wouldn t have to learn new syntaxes all the time but to be fair it s hard to predict what kinds of information programs will need IconManagerBackground honeydew I hope you don t have a monochrome system but if you do Monochrome BorderColor black BorderTileForeground black BorderTileBackground white TitleForeground black TitleBackground white I created beifang bmp with the program bitmap H
83. arry ls F rog passwd passwd_version Li f home larry cp frog passwd passwd_version f home larry ls F passwd_version frog passwd home larry How did I just use cp Evidentally cp can take more than two parameters This is the second line in the command template What the above command did is copied all the files listed frog and passwd and placed them in the passwd_version directory In fact cp can take any number of parameters and interprets the first n 1 parameters to be files to copy and the n parameter as what directory to copy them too You cannot rename files when you copy more than one at a time they always keep their short name This leads to an interesting question What if I type cp frog passwd toad where frog and passwd exist and toad isn t a directory Try it and see 4 4 2 Pruning Back with rm rm 1 filel file2 fileN Now that we ve learned how to create millions of files with cp and believe me you ll find new ways to create more files soon it may be useful to learn how to delete them Actually it s very simple the command you re looking for is rm and it works just like you d expect any file that s a parameter to rm gets deleted For example home larry ls F frog passwd passwd_version home larry rm frog toad passwd rm toad No such file or directory home larry ls F passwd_version home larry As you can see rm is
84. as created at the Massachusetts Institute of Technology It was written to allow Unix systems to create graphical windows and easily interact with each other Today the X Window System is used on every version of Unix available In addition to the two variations of Unix System V and BSD there is also a set of stan dardization documents published by the IEEE entitled POSIX Linux is first and foremost compliant with the POSIX 1 and POSIX 2 documents Its look and feel is much like BSD in some places and somewhat like System V in others It is a blend and to most people a good one of all three standards Many of the utilities included with Linux distributions are from the Free Software Foun dation and are part of GNU Project The GNU Project is an effort to write a portable ad vanced operating system that will look a lot like Unix Portable means that it will run on a variety of machines not just Intel PCs Macintoshes or whatever The GNU Project s operating system is called the Hurd The main difference between Linux and GNU Hurd is not in the user interface but in the programmer s interface the Hurd is a modern operating system while Linux borrows more from the original Unix design The above history of Linux is deficient in mentioning anybody besides Linux Torvalds For instance H J Lu has maintained gcc and the Linux C Library two items needed for all the programs on Linux since very early in Linux s life You can find
85. at trixie s rhosts file on frobbo doesn t enter into it only the one on the remote machine matters There are other combinations that can go ina rhosts file for example you can leave off the username following a remote machine name to allow any user from that machine to run programs as you on the local machine This is of course a security risk someone could remotely run a program that removes your files just by virtue of having an account on a certain machine If you re going to do things like leave off the username then you ought to make sure that your rhost s file is readable by you and no one else 9 3 4 Mail Forwarding You can also have a forward file which is not strictly speaking an init file If it contains an email address then all mail to you will be forwarded to that address instead This is useful when you have accounts on many different systems but only want to read mail at one location There is a host of other possible initialization files The exact number will vary from system to system and is dependent on the software installed on that system One way to learn more is to look at files in your home directory whose names begin with These files are not all guaranteed to be init files but it s a good bet that most of them are 9 4 Seeing Some Examples The ultimate example I can give you is a running Linux system So if you have Inter net access feel free to telnet to floss life uiuc edu
86. available memory on your machine Don t worry you don t have to set all these autoloads in your emacs they were taken care of when Emacs was built 8 14 Finding Out More I have not told you everything there is to know about Emacs In fact I don t think I have even told you 1 of what there is to know about Emacs While you know enough to get by there are still lots of time saving tricks and conveniences that you ought to find out about The best way to do this is to wait until you find yourself needing something and then look for a function that does it The importance of being comfortable with Emacs s online help facilities cannot be em phasized enough For example suppose you want to be able to insert the contents of some file into a buffer that is already working on a different file so that the buffer contains both 10By the way cmuscheme was the interface I was talking about earlier in the section on working with Scheme so if you want to use any of the stuff from that tutorial you need to make sure that you run cmuscheme of them Well if you were to guess that there is a command called insert file you d be right To check your educated guess type C h f At the prompt in the minibuffer en ter the name of a function that you want help on Since you know that there is completion on function names and you can guess that the command you are looking for begins with insert you type insert and hit Tab This shows you
87. be used for stylistic purposes The file chapter 1 would be the file called chapter 1 in the current directory Occasionally you need to put the for some commands to work although this is rare In most cases chapter 1 and chapter 1 will be identical The directory is most useful in backing up usr local bin cd usr local ls F archives bin emacs etc ka9q lib tcl usr local ls F srce cweb linux xmris usr local In this example I changed to the parent directory using cd and I listed the direc tory usr srcfrom usr local using src Note that if I was in home larry typing ls F src wouldn t do me any good The directory is an alias for your home directory usr local ls F usr local You can see ata glance that there isn t anything in your home directory will become more useful as we learn more about how to manipulate files 4 3 3 Creating and Removing Directories mkdir directory directory2 directoryN Creating your own directories is extremely simple under Unix and can be a useful or ganizational tool To create a new directory use the command mkdir Of course mkdir stands for make directory Let s do a small example to see how this works hnome larry ls F home larry mkdir report 1993 home larry ls F report 1993 home larry cd report 1993 home larry report 1993 mkdir can take more than one parameter
88. be very careful with mv it doesn t check to see if the file already ex ists and will remove any old file in its way For instance if I had a file named frog already in my directory report the command mv frog report would delete the file report frog and replace it with frog In fact there is one way to make rm cp and mv ask you before deleting files All three of these commands accept the i option which makes them query the user before removing any file If you use an alias you can make the shell do rm i automatically when you type rm You ll learn more about this later in Section 9 1 3 on page 110 Figure 4 1 A typical abridged Unix directory tree bin dev etc home larry E sam lib proc tmp usr X11R6 bin emacs etc g include include lib local bin emacs etc lib man spool src linux tmp Chapter 5 The X Window System The nice thing about standards is that there are so many of them to choose from Andrew S Tanenbaum This chapter only applies to those using the X Window System If you encounter a screen with multiply windows colors or a cursor that is only movable with your mouse you are using X If your screen consists of white characters on a black background you are not currently using X If you want to start it up take a look at Section 5 1 5 1 Starting and Stopping the X Window System 5 1 1 Starting X Even if X doesn t start automatically when you login it is possi
89. ble to start it from the regular text mode shell prompt There are two possible commands that will start X either startx or xinit Try startx first If the shell complains that no such command is found try using xinit and see if X starts If neither command works you may not have X installed on your system consult local documentation for your distribution If the command runs but you are eventually returned to the black screen with the shell prompt X is installed but not configured Consult the documentation that came with your 43 distribution on how to setup X 5 1 2 Exiting X Depending on how X is configured there are two possible ways you might have to exit X The first is if your window manager controls whether or not X is running If it does you ll have to exit X using a menu see Section 5 4 8 on page 50 To display a menu click a button on the background The important menu entry should be Exit Window Manager or Exit X or some entry containing the word Exit Try to find that entry there could be more than one menu try different mouse buttons and choose it The other method would be for a special xterm to control X If this is the case there is probably a window labeled login or system xterm To exit from X move the mouse cursor into that window and type exit If X was automatically started when you logged in one of these methods should log you out Simply login again to return
90. blem to programmers how could they know what a terminal supported and didn t support And how could they support new features without making old terminals worthless In Unix the answer to these questions was etc termcap etc termcap is a list of all of the terminals that your system knows about and how they control the cursor If a system administrator got a new terminal all they d have to do is add an entry for that terminal into etc termcap instead of rebuilding all of Unix Sometimes it s even simplier Along the way Digital Equipment Corporation s vt100 terminal became a pseudo standard and many new terminals were built so that they could emulate it or behave as if they were a vt100 Under Linux TERM s value is sometimes console which is a vt100 like terminal with some extra features Another variable PATH is also crucial to the proper functioning of the shell Here s mine home larry env grep PATH PATH home larry bin bin usr bin usr local bin usr bin X11 home larry Your PATH is a colon separated list of the directories the shell should search for pro grams when you type the name of a program to run When I type 1s and hit Return for example the Bash first looks in home larry bin a directory I made for storing pro grams that I wrote However I didn t write 1s in fact I think it might have been written before I was born Failing to find itin home larry bin Bash looks nextin bin
91. click and hold down on the left button Then move the pointer to the action you want and release the mouse button If you change your mind move the mouse pointer away from the menu and release the button The Buffers menu lists the different files you ve been editing in this incarnation of Emacs The File menu shows a bunch of commands for loading and saving files many of them will be described later The Edit menu displays some commands for editing one buffer and the Help menu should hopefully give on line documentation You ll notice keyboard equivalents are listed next to the choices in the menu Since in the long run they ll be quicker you might want to learn them Also for better or for worse most of Emacs s functionality is only available through the keyboard you might want to read the rest of this chapter 8 3 Editing Many Files at Once Emacs can work on more than one file at a time In fact the only limit on how many buffers your Emacs can contain is the actual amount of memory available on the machine The command to bring a new file into an Emacs buffer is C x C f When you type it you will be prompted for a filename in the minibuffer Find file The syntax here is the same one used to specify files from the shell prompt slashes represent subdirectories means your home directory You also get filename comple tion meaning that if you ve typed enough of a filename at the prompt to identify the file u
92. contains plus any associated interface definition files plus the scripts used to control compilation and installation of the library Activities other than copying distribution and modification are not covered by this License they are outside its scope The act of running a program using the Library is not restricted and output from such a program is covered only if its contents constitute a work based on the Library independent of the use of the Library in a tool for writing it Whether that is true depends on what the Library does and what the program that uses the Library does You may copy and distribute verbatim copies of the Library s complete source code as you receive it in any medium provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty keep intact all the notices that refer to this License and to the absence of any warranty and distribute a copy of this License along with the Library You may charge a fee for the physical act of transferring a copy and you may at your option offer warranty protection in exchange for a fee You may modify your copy or copies of the Library or any portion of it thus forming a work based on the Library and copy and distribute such modifications or work un der the terms of Section above provided that you also meet all of these conditions a The modified work must itself be a software library b You must ca
93. cro definitions There is a section on ex and its settings which helps customize the editor This tutorial describes the commands rather then taking you set by set through each of them It is recommended you spend the time trying the commands out on some example text which you can afford to destroy This tutorial does not expose all the commands of vi though all of the commonly used commands and more are covered Even if you choose to use an alternative text editor it is hoped you will appreciate vi and what it offers those who do choose to use it A 4 1 Moving around The most basic functionality of an editor is to move the cursor around in the text Here are more movement commands He wu y move move move move th on on on e cursor one space to the left e line down e line up e line right Some implementations also allow the arrows keys to move the cursor O 3 ira gt OO Ur lt CR gt 1G nG lt Cntl gt G ale So Ee Ss ove ove ove ove ove ove ove ove ove ove ove 3 3 8 83 8 8 8 8 3 88 8 ove disp to the ma top midd to to to to to to to to to to to to Lay line number n tching bracket the start of the next word the end of the next word the end of the next word before a space the start of the previous word the start of the line the first word of the current line the end of the line the start of the next line the
94. d before you hit return notice that there was a spelling mistake early in the line You could just delete all the way back and retype everything you need to but that takes much too much effort Instead you can use the arrow keys to move back there delete the bad character or two and type the correct information There are many special keys to help you edit your command line most of them similar to the commands used in GNU Emacs For instance flips two adjacent characters You ll be able to find most of the commands in the chapter on Emacs Chapter 8 c means hold down the key labeled Ctrl then press the t key Then release the Ctrl key 6 2 2 Command and File Completion Another feature of bash is automatic completion of your command lines For instance let s look at the following example of a typical cp command hnome larry ls F this is a long file home larry cp this is a long file shorter home larry ls F shorter this is a long fil home larry It s a big pain to have to type every letter of this is a long file whenever you try to access it So create this is a long file by copying etc passwa to it Now we re going to do the above cp command very quickly and with a smaller chance of mistyping Instead of typing the whole filename type cp th and press and release the Tab Like magic the rest of the filename shows up on the command line and you can type i
95. d gray but could look like anything To try to see a menu click and hold down a button on the desktop A 4One fun program to try is called xfishtank It places a small aquarium in the background for you menu should pop up To make a selection move without releasing the mouse button the cursor over one of the items any then release the mouse button 5 5 X Attributes There are many programs that take advantage of X Some programs like emacs can be run either as a text mode program or as a program that creates its own X window However most X programs can only be run under X 5 5 1 Geometry There are a few things common to all programs running under X In X the concept of geometry is where and how large a window is A window s geometry has four components e The horizontal size usually measured in pixels A pixel is the smallest unit that can be colored Many X setups on Intel PCs have 1024 pixels horizontally and 768 pixels vertically Some applications like xterm and emacs measure their size in terms of number of characters they can fit in the window For instance eighty characters across The vertical size also usually measured in pixels It s possible for it to be measured in characters e The horizontal distance from one of the sides of the screen For instance 35 would mean make the left edge of the window thirty five pixels from the left edge of the screen On the other hand 50 would mean make the right edge
96. d hold down the left mouse button This will display a variety of commands To select one of the commands move the mouse cursor over that command and release Figure 5 3 emacs will change its menu bar depending on the type of file you re working on Here is one possible menu bar Buffers Files Tools Edit Search Help the left mouse button Some menu bars let you click on a category if this is the case clicking on the category will display the menu until you click on either a command another menu or outside the menu bar indicating that you are not interested in running a particular command 5 6 3 Scroll Bars A scroll bar is a method to allow people to display only part of a document while the rest is off the screen For instance the xt erm window is currently displaying the bottom third of the text available in Figure 5 4 It s easy to see what part of the available text is current being displayed the darkened part of the scroll bar is relative to both the position and the amount of displayed text If the text displayed is all there is the entire scroll bar is dark If the middle half of the text is displayed the middle half of the scroll bar is darkened A vertical scroll bar may be to the left or right of the text and a horizontal one may be above or below depending the application Athena scroll bars Athena scroll bars operate differently from scroll bars in other windowing systems Each of the three buttons of the mouse
97. d not attempt auto login by invoking it with the n option ftp n You must make sure that your net rc file is readable only by you Use the chmod program to set the file s read permissions If other people can read it that means they can find out your password at various other sites This is about as big a security hole as one can have to encourage you to be careful ftp and other programs that look for the netrc file will actually refuse to work if the read permissions on the file are bad There s more to the netrc file than what I ve said when you get a chance do g3 man netrc or man ftp 9 3 3 Allowing Easy Remote Access to Your Account If you have an rhosts file in your home directory it will allow you to run programs on this machine remotely That is you might be logged in on the machine cs oberlin edu but with a correctly configured rhosts file on floss life uiuc edu you could run a pro gramon floss life uiuc eduand have the output go to cs oberlin edu with out ever having to log in or type a password A rhosts file looks like this frobnozz cs knowledge edu jsmith aphrodite classics hahvaahd edu wphilps frobbo hoola com trixie The format is fairly straightforward a machine name followed by username Suppose that that example is in fact my rhosts file on 1oss life uiuc edu That would mean that I could run programs on floss with output going to any of the machines listed as long
98. e different line numbers it is much more efficent then listing out every single line if there is an extra return early in one file gzip v filel file2 fileN gunzip v filel file2 fileN zcat filel file2 fileN These three programs are used to compress and decompress data gzip or GNU Zip is the program that reads in the original file s and outputs files that are smaller gzip deletes the files specified on the command line and replaces them with files that have an identical name except that they have gz appended to them tr string string2 The translate characters command operates on standard input it doesn t accept a filename as a parameter Instead it s two parameters are arbitrary strings It replaces all occurences of string in the input with string2 In addition to relatively simple com mands such as tr frog toad tr can accept more complicated commands For in stance here s a quick way of converting lowercase characters into uppercase ones nome larry tr lower upper this is a WEIRD sentence THIS IS A WEIRD SENTENCE tr is fairly complex and usually used in small shell programs Chapter 8 Editing files with Emacs FUNNY SOMETHING OR OTHER 8 1 What s Emacs In order to get anything done on a computer you need a way to put text into files and a way to change text that s already in files An editor is a program for doing this Emacs is
99. e a derivative work of the Library even though the source code is not Whether this is true is especially significant if the work can be linked without the Library or if the work is itself a library The threshold for this to be true is not precisely defined by law If such an object file uses only numerical parameters data structure layouts and accessors and small macros and small inline functions ten lines or less in length then the use of the object file is unrestricted regardless of whether it is legally a derivative work Executables containing this object code plus portions of the Library will still fall under Section 6 Otherwise if the work is a derivative of the Library you may distribute the object code for the work under the terms of Section 6 Any executables containing that work also fall under Section 6 whether or not they are linked directly with the Library itself 6 As an exception to the Sections above you may also compile or link a work that uses the Library with the Library to produce a work containing portions of the Library and distribute that work under terms of your choice provided that the terms permit modification of the work for the customer s own use and reverse engineering for debugging such modifications You must give prominent notice with each copy of the work that the Library is used in it and that the Library and its use are covered by this License You must supply a copy of this License
100. e a lot of mischief indeed The person did not need root privileges to do this they only needed write permission on the directory where the false 1s was located It might even have been their home directory if they knew that you would be poking around in there at some point On your own system it s highly unlikely that people are leaving traps for each other All the users are probably friends or colleagues of yours However on a large multi user system like many university computers there could be plenty of unfriendly programmers whom you ve never met Whether or not you want to take your chances by having in your path depends on your situation I m not going to be dogmatic about it either way I just want you to be aware of the risks involved Multi user systems really are communities where people can do things to one another in all sorts of unforseen ways The actual way that I set my PATH involves most of what you ve learned so far about environment variables Here is what is actually in my bashrc export PATH S PATH HOME bin bin usr bin usr local bin usr bin X11 usr TeX bin Here I am taking advantage of the fact that the HOME variable is set before Bash reads my bashrc by using its value in setting my PATH The curly braces Y are a further level of quoting they delimit the extent of what the is to evaluate so that the shell doesn t get confused by the text immedia
101. e for C r it wraps around the end of the buffer Try bringing up a buffer of plain English text and doing and isearch for the string the First you d type in as much as you wanted then use repeated C s s to go to all instances of it Notice that it will match words like them as well since that also contains the substring the To search only for the you d have to do add a space to the end of your search string You can add new characters to the string at any point in the search even after you ve hit C s repeatedly to find the next matches You can also use Backspace or Delete to remove characters from the search string at any point in the search and hitting Return exits the search leaving you at the last match Emacs also allows you to replace all instances of a string with some new string this is known as query replace To invoke it type query replace and hit Return Completion is done on the command name so once you have typed query re you can just hit to finish it Say you wish to replace all instances of gadfly with housefly At the Query replace prompt type gadfly and hit Return Then you will be prompted again and you should enter housefly Emacs will then step through the buffer stopping at every instance of the word gadfly and asking 1f you want to replace it Just hit y or n at each instance for Yes or No until i
102. e just seen an example of hackers humor Besides look at it from the bright side there is no MS DOS equivalent of these commands If you need them you have to purchase them and you never know how their interface will be Here they are a useful and inexpensive add on so enjoy The set of commands dwelled on in this chapter covers ind which lets the user search in the directory tree for specified groups of files t ar useful to create some archive to be shipped or just saved dd the low level copier and sort which yes sorts files A last proviso these commands are by no means standardized and while a core of common options could be found on all IX systems the GNU version which is explained below and which you can find in your Linux system has usually many more capabilities So if you plan to use other UNIX like operating systems please don t forget to check their man page in the target system to learn the maybe not so little differences 141 11 1 find the file searcher 11 1 1 Generalities Among the various commands seen so far there were some which let the user recursively go down the directory tree in order to perform some action the canonical examples are 1s Rand rm R Good find is the recursive command Whenever you are thinking Well I have to do so and so on all those kind of files in my own partition you have better think about using find Ina certain sense the fact that find finds files is
103. e moment is a directory then the first exec is evaluated and the permission of the inode is changed to 771 otherwise it forgets all and steps to the next subexpression Probably it s easier to see it in practice than to writing it down but after a while it will become a natural thing 11 2 tar the tape archiver 11 2 1 Introduction 11 2 2 Main options 11 2 3 Modifiers 11 2 4 Examples 11 3 dd the data duplicator Legend says that back in the mists of time when the first UNIX was created its developers needed a low level command to copy data between devices As they were in a hurry they decided to borrow the syntax used by IBM 360 machines and to develop later an interface consistent with that of the other commands Time passed and all were so used with the odd way of using dd that it stuck I don t know whether it is true but it is a nice story to tell 11 3 1 Options To say the truth dd it s not completely unlike the other Unix command it is indeed a filter that is it reads by default from the standard input and writes to the standard output So if you just type dd at the terminal it remains quiet waiting for input and a ctrl C is the only sensitive thing to type The syntax of the command is as follows dd if file of file ibs bytes obs bytes bs bytes cbs bytes skip blocks seek blocks count blocks conv ascii ebcdic ibm block unblock Icase ucase swab noerror notrunc sync Al
104. e multiple X servers running on it unlikely for most Linux machines but possi ble each must have a unique number e The screen number X supports a particular server controlling more than one screen at a time You can imagine that someone wants a lot of screen space so they have two monitors sitting next to each other Since they don t want two X servers running on one machine for performance reasons they let one X server control both screens These three things are put together like so machine server number screen number For instance on mousehouse all my applications have the display set to 0 0 which means the first screen of the first server on the local display However if I am using a remote computer the display might be set to mousehouse 0 0 By default the display is taken from the environment variable see Section 9 1 4 named DISPLAY and can be overridden with a command line option see Figure 5 2 To see how DISPLAY is set try the command echo DISPLAY 5 6 Common Features While X is a graphical user interface itis a very uneven graphical user interface It s impos sible to say how any component of the system is going to work because every component can easily be reconfigured changed and even replaced This means it s hard to say exactly how to use various parts of the interface We ve already encountered one cause of this the different window managers and how configurable each window manager is Ano
105. e user without using standard input or output but most of the com mands I cover in this book use stdin and stdout For example the 1s command prints the list of the directories to standard output which is normally connected to your terminal An interactive command such as your shell bash reads your commands from standard input It is also possible for a program to write to standard error since it is very easy to make standard output point somewhere besides your terminal Standard error stderr is almost always connected to a terminal so an actual human will read the message In this section we re going to examine three ways of fiddling with the standard input and output input redirection output redirection and pipes 6 3 2 Output Redirection A very important feature of Unix is the ability to redirect output This allows you instead of viewing the results of a command to save it in a file or send it directly to a printer For instance to redirect the output of the command 1s usr bin we place a gt sign at the end of the line and say what file we want the output to be put in home larry 1s home larry ls F usr bin gt listing hnome larry 1s listing home larry As you can see instead of writing the names of all the files the command created a totally new file in your home directory Let s try to take a look at this file using the command cat If you think back you ll remember cat was a fairly usel
106. earts Don t ruin it for them the Linux community has already disillusioned too many developers and it s still early in Linux s life Appendix A Introduction to Vi vi pronounced vee eye is really the only editor you can find at almost every Unix in stallation It was originally written at the University of California at Berkeley and versions can be found it almost every vendor s edition of Unix including Linux It is initially some what hard to get used to but it has many powerful features In general we suggest that a new user learn Emacs which is generally easier to use However people who will use more than one platform or find they dislike Emacs may want to try to learn vi A brief historical view of vi is necessary to understand how the key can mean move cursor up one line and why there are three different modes of use If you are itchy to learn the editor then the two tutorials will guide you from being a raw beginner through to having enough knowledge of the command set you are ever likely to need The chapter also incorporates a command guide which makes a useful reference to keep by the terminal Even if vi does not become your regular text editor the knowledge of its use is not wasted It is almost certain that the Unix system you are using will have some variant of the vi editor It may be necessary to use vi while installing another editor such as Emacs Many Unix tools applications and games use a subset
107. ective works based on the Program In addition mere aggregation of another work not based on the Program with the Program or with a work based on the Program on a volume of a storage or distri bution medium does not bring the other work under the scope of this License You may copy and distribute the Program or a work based on it under Section 2 in object code or executable form under the terms of Sections and 2 above provided that you also do one of the following a Accompany it with the complete corresponding machine readable source code which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or b Accompany it with a written offer valid for at least three years to give any third party for a charge no more than your cost of physically performing source distribution a complete machine readable copy of the corresponding source code to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or c Accompany it with the information you received as to the offer to distribute cor responding source code This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer in accord with Subsection b above The source code for a work means the preferred form of the work for making mod ifications to it For an executable wo
108. efore You do not need to worry that while you had it suspended it was storing up more y s to send to the screen when a program is suspended the whole program doesn t run until you bring it back to life Now type to kill it for good once you ve seen enough gt There are good reasons for this strange command to exist Occasional commands ask for confirmation a yes answer to a question The yes command allows a programmer to automate the response to these questions Let s pick apart that message we got from the shell 1 Stopped yes The number in brackets is the job number of this job and will be used when we need to refer to it specifically Naturally since job control is all about running multiple processes we need some way to tell one from another The following it tells us that this is the current job that is the one most recently moved from the foreground to the background If you were to type g you would put the job with the in the foreground again More on that later when we discuss running multiple jobs at once The word Stopped means that the job is stopped The job isn t dead but it isn t running right now Linux has saved it in a special suspended state ready to jump back into the action should anyone request it Finally the yes is the name of the process that has been stopped Before we go on let s kill this job and start it again in a different way The command is named
109. ehaviour a Append some text from the current cursor postion A Append at the end of the line i Insert text to the Left of the cursor I Inserts text to the Left of the first non white character on current line o Open a new line and adds text Below current line O Open a new line and adds text Above the current line We give it and we take it away vi has a small set of delete commands which can be enhanced with the use of command modifiers x Delete one character from under the cursor dw Delete from the current position to the end of the word dd Delete the current line D Delete from the current position to the end of the line The modifiers can be used to add greater power to the commands The following ex amples are a subset of the posibilities nx Delete n characters from under the cursor ndd Delete n lines dnw Deletes n words Same as ndw dG Delete from the current position to the end of the file dic Delete from the current postion to the start of the file ds Delete from current postion to the end of the line This is the same as D dns Delete from current line the end of the nth line The above command list shows the delete operating can be very powerfull This is evident when applied in combination with the cursor movement commands One command to note is D since it ignores the modifier directives On occasions you may need to undo the changes The following commands restore the text after changes
110. er there are some disadvantages rm and mv never ask for confirmation and this frequently leads to problems Thus let s go through a small list that might help you avoid total disaster e Keep backups This applies especially to the one user system all system admin strators should make regular backups of their system Once a week is good enough 155 to salvage many files See the The Linux System Adminstrator s Guide for more information e Individual user s should keep there own backups if possible If you use more than one system regularly try to keep updated copies of all your files on each of the systems If you have access to a floppy drive you might want to make backups onto floppies of your critical material At worst keep additional copies of your most important material lying around your account in a seperate directory e Think about commands especially destructive ones like mv rm and cp before you act You also have to be careful with redirection gt it ll overwrite your files when you aren t paying attention Even the most harmless of commands can become sinister nome larry report cp report 1992 report 1993 backups can easily become disaster home larry report cp report 1992 report 1993 e The author also recommends from his personal experience not to do file mainta nence late at night Does you directory structure look a little messy at 1 32am Let it stay a little mess never hurt
111. er boot record MBR on the hard disk It will start executing the code found there which loads the operating system On Linux systems LILO the LInux LOader can occupy the MBR position and will load Linux For now we ll assume that happens and that Linux starts to load Your particular distribution may handle booting from the hard disk differently Check with the documentation included with the distribution Another good reference is the LILO documentation 1 3 2 Linux Takes Over After the BIOS passes control to LILO LILO passes control to the Linux kernel A kernel is the central program of the operating system in control of all other programs The first thing that Linux does once it starts executing is to change to protected mode The 803867 CPU that controls your computer has two modes called real mode and protected mode DOS runs in real mode as does the BIOS However for more advanced operating systems it is necessary to run in protected mode Therefore when Linux boots it discardes the BIOS Other CPUs will get to this stage differently No other CPU needs to switch into pro tected mode and few have to have such a heavy framework around the loading procedure as LILO and the BIOS Once the kernel starts up Linux works much the same 2When I refer to the 80386 I am also talking about the 80486 Pentium and Pentium Pro computers unless I specifically say so Also I ll be abbreviating 80386 as 386 Figure 3
112. ere I tell twm to use it as the default highlight pattern on windows title bars Pixmaps TitleHighlight home larry x beifang bmp Don t worry about this stuff it s only for power users BorderWidth 2 TitleFont adobe new century schoolbook bold r normal 14 140 75 75 p 87 iso8859 1 enuFont toOxT30 IconFont lucidasans italic 14 ResizeFont fixed Zoom 50 RandomP lacement These programs will not get a window titlebar by default NoTitle stamp xload xclock xlogo xbi t xeyes oclock xoid AutoRaise means that a window is brought to the front whenever the mouse pointer enters it I find this annoying so I have it turned off As you can see I inherited my twmrc from people who also did not like autoraise AutoRaise nothing I don t like auto rais M ither nor I Here is where the mouse button functions are defined Notice the pattern a mouse button pressed on the root window with no modifier key being pressed always brings up a menu Other locations usually result in window manipulation of some kind and modifier keys are used in conjunction with the mouse buttons to get at the more sophisticated window manipulations You don t have to follow this pattern in your own twmrc it s entirely up to you how you arrange your environment Button KEYS CONTEXT FUNCTION Buttonl root f menu main Buttonl
113. ess command that copied what you typed the standard input to the terminal the standard output cat can also print a file to the standard output if you list the file as a parameter to cat home larry cat listing home larry The exact output of the command 1s usr bin appeared in the contents of listing All well and good although it didn t solve the original problem However cat does do some interesting things when it s output is redirected What does the command cat listing gt newfile do Normally the gt newfile says take all the output of the command and put it in newf f ile The output of the command cat listing is the file listing So we ve invented a new and not so efficient method of copying files How about the command cat gt fox cat by itself reads in each line typed at the terminal standard input and prints it right back out standard output until it reads Ctri d In this case standard output has been redirected into the file fox Now cat is serving as a rudimentary editor home larry cat gt fox The quick brown fox jumps over the lazy dog press Ctrl d We ve now created the file fox that contains the sentence The quick brown fox jumps over the lazy dog One last use of the versitile cat command is to concatenate files together cat will print out every file it was given as a parameter one after another So the command cat listing fox will print out the directory listing of usr bin
114. estroy quit Whew Believe me that s not even the most involved twmrc I ve ever seen It s quite probable that some decent example t wmrc files came with your X Take a look in the directory usr lib X11 twm or usr X11 1ib X11 twmand see what s there One bug to watch out for with twmrc files is forgetting to put the amp after a command on a menu If you notice that X just freezes when you run certain commands chances are that this is the cause Break out of X with Control Alt Backspace edit your twmrc and try again 9 2 2 Fvwm Configuration If you are using fvwm the directory usr 1ib X11 fvwm or usr X11 1ib X11 fvwm has some good example config files in it as well Folks I don t know anything about fvwm although I might be able to grok something from the example config files Then again so could the reader Also given the decent but small system twmrc in the above mentioned directory I wonder if it s worth it for me to provide that lengthy example with my own twmrc It s in for now but I don t know whether we want to leave it there or not Karl 9 3 Other Init Files Some other initialization files of note are emacs Read by the Emacs text editor when it starts up netrca Gives default login names and passwords for ftp rhosts Makes your account remotely accessible forward For automatic mail forwarding 9 3 1 The Emacs Init File If you use emacs as your pri
115. esult This section will introduce named and unnamed buffers along with the commands which cut and paste the text Coping text involves three main steps 1 Yanking copying the text to a buffer 2 Moving the cursor to the destination location 3 Pasting putting the text to the edit buffer To Yank text to the unnamed use command YY Y nyy nY yw ynw nyw ys ove a copy of the current line to the unnamed buffer ove a copy of the current line to the unnamed buffer ove the next n lines to the unnamed buffer ove the next n lines to the unnamed buffer ove a word to the unnamed buffer ove n words to the unnamed buffer ove n words to the unnamed buffer ove the current position to the end of the line The unnamed buffer is a tempory buffer that is easily currupted by other common com mands On occations the text my be needed for a long period of time In this case the named buffers would be used vi has 26 named buffers The buffers use the letters of the alphabet as the identification name To distinguish the difference between a command or a named buffer vi uses the P character When using a named buffer by the lowercase letter the contents are over written while the uppercase version appends to the current contents ayy ay byw Byw by3w Move current Move current line to named buffer a line to named buffer a Move current word to named buffer b Append the
116. ethod used to resize windows Another method used is to create a resizing button on the titlebar In Figure 5 3 a small button is visible on the right of each titlebar To resize windows the mouse is moved onto the resize button and the left mouse button is held down You can then move the mouse outside the borders of the window to resize it The button is released when the desired size has been reached 5 4 7 Maximization Most window managers support maximization In twm for instance you can maximize the height the width or both dimensions of a window This is called zooming in t wm s language although I prefer the term maximization Different applications respond differ ently to changes in their window size For instance xterm won t make the font bigger but will give you a larger workspace Unfortunately it is extremely non standard on how to maximize windows 5 4 8 Menus Another purpose for window managers is for them to provide menus for the user to quickly accomplish tasks that are done over and over For instance I might make a menu choice that automatically launches Emacs or an additional xterm for me That way I don t need to type in an xt erm an especially good thing if there aren t any running xt erms that I need to type in to start a new program In general different menus can be accessed by clicking on the root window which is an immovable window behind all the other ones By default it is colore
117. everybody else who isn t the owner and isn t a member of the group appropriately called other So a file could have read and write permissions for the owner read permissions for the group and no permissions for all others Or for some reason a file could have read write permissions for the group and others but no permissions for the owner Let s try using chmod to change a few permissions First create a new file using cat emacs or any other program By default you ll be able to read and write this file The permissions given other people will vary depending on how the system and your account is setup Make sure you can read the file using cat Now let s take away your read privilege by using chmod u r filename The parameter u r decodes to user minus read Now if you try to read the file you get a Permission denied error Add read privileges back by using chmod utr filename Directory permissions use the same three ideas read write and execute but act slightly differently The read privilege allows the user or group or others to read the directory list the names of the files The write permission allows the user or group or others to add or remove files The execute permission allows the user to access files in the directory or any subdirectories If a user doesn t have execute permissions for a directory they can t even cd to it To use chmod replace the mode with what to operate on either user
118. f them in the last year or so It takes a little practice but the learning curve is not steep at all Another thing people often do in their emacs is set certain variables to preferred values For example put this in your emacs and then start up a new Emacs setq inhibit startup message t Emacs checks the value of the variable inhibit startup message to decide whether or not to display certain information about version and lack of warranty when it starts up The Lisp expression above uses the command setq to set that variable to the gt value t which is a special Lisp value that means true The opposite of t is nil which is the designated false value in Emacs Lisp Here are two things that are in my emacs that you might find useful setq case fold search nil gives case insensitivity in searching 7 make C programs indent the way I like them to setq c indent level 2 The first expression causes searches including isearch to be case insensitive that 1s the search will match upper or lower case versions of a character even though the search string contains only the lower case version The second expression sets the default indentation for C language statements to be a little smaller than it is normally this is just a personal preference I find that it makes C code more readable The comment character in Lisp is Emacs ignores anything following one unless it appears inside a lite
119. f you like and have it display on the workstation right in front of you A third term you should be familiar with is the window manager The window man ager is a special client that tells the server where to position various windows and provides a way for the user to move these windows around The server by itself does nothing for the user It is merely there to provide a buffer between the user and the client 5 3 What s This on my Screen When you first start X several programs are started First the server is started Then several clients are usually started Unfortunately this is not standardized across various distributions It is likely that among these clients are a window manager either fvwm or twm a prompt xterm and a clock xclock 5 3 1 XClock xclock digital analog update seconds hands color Pll explain the simpliest one first xc lock functions exactly as you d expect it would It ticks off the seconds minutes and hours in a small window No amounts of clicking or typing in xclock s window will affect it that s all it does Or is it In fact there are various different options you can give to the program to have it act in different ways For instance xclock digital will create a digital clock xclock update 1 will create a second hand that moves every second while update 5 will create a second hand that moves every 5 seconds For more information on xclock s options consult its manpage
120. freedom to share and change free software to make sure the software is free for all its users This license the Library General Public License applies to some specially designated Free Software Foundation software and to any other libraries whose authors decide to use it You can use it for your libraries too 187 When we speak of free software we are referring to freedom not price Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software and charge for this service if you wish that you receive source code or can get it if you want it that you can change the software or use pieces of it in new free programs and that you know you can do these things To protect your rights we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights These restrictions translate to certain responsibilities for you if you distribute copies of the library or if you modify it For example if you distribute copies of the library whether gratis or for a fee you must give the recipients all the rights that we gave you You must make sure that they too receive or can get the source code If you link a program with the library you must provide complete object files to the recipients so that they can relink them with the library after making changes to the library and recompiling it And you must show them these terms so they know their rights
121. good portion of diff is beyond the scope of this book Pll just talk about the basic operation of diff In short diff takes two parameters and displays the differences between them on a line by line basis For instance home larry cat frog Animals are very interesting creatures One of my favorite animals is the tiger a fearsome beast with large teeth 3While there are versions of this for several other European languages the copy on your Linux machine is most likely for American English I also like the lion it s really neat home larry cp frog toad home larry diff frog toad home larry cat dog A the tiger a fearsome beast with large teeth I also like the lion it s really neat home larry diff frog dog Led 2 lt Animals are very interesting creatures One of my favorite animals nimals are very nteresting creatures One of my favorite animals is is gt Animals are very nteresting creatures One of my favorite animals is gt 3c4 lt I also like the lion it s really neat gt I also like the lion it s really neat home larry As you can see diff outputs nothing when the two files are identical Then when I compared two different files it had a section header 1c1 2 saying it was comparing line 1 of the left file frog to lines 1 2 of dog and what differences it noticed Then it compared line 3 of frog to line 4 of dog While it may seem strange at first to compar
122. group other or all and what to do with them That is use a plus sign to indicate adding a privilege or a minus sign to indicate taking one away Or an equals sign will specify the exact permissions The possible permissions to add are read write and execute chmod s R flag will change a directory s permissions and all files in that directory and all subdirecties all the way down the line The R stands for recursive The f flag forces chmod to attempt to change permissions even if the user isn t the owner of the file If chmod is given the f flag it won t print an error message when it fails to change a file s permissions The v flag makes chmod verbose it will report on what it s done 7 3 System Statistics Commands in this section will display statistics about the operating system or a part of the operating system du abs path path2 pathN du stands for disk usage It will count the amount of disk space a given directory and all its subdirectories take up on the disk du by itself will return a list of how much space every subdirectory of the current directory consumes and at the very bottom how much space the current directory plus all the previously counted subdirectories use If you give it a parameter or two it will count the amount of space used by those files or directories instead of the current one The a flag will display a count for files as well as directories An option of b
123. h Customization One of the distinguishing things about the Unix philosophy is that the system s designers did not attempt to predict every need that users might have instead they tried to make it easy for each individual user to tailor the environment to their own particular needs This is mainly done through configuration files These are also known as init files rc files for run control or even dot files because the filenames often begin with If you ll recall filenames that start with aren t normally displayed by 1s The most important configuration files are the ones used by the shell Linux s default shell is bash and that s the shell this chapter covers Before we go into how to customize bash we should know what files bash looks at 9 1 1 Shell Startup There are several different ways bash can run It can run as a login shell which is how it runs when you first login The login shell should be the first shell you see Another way bash can run is as an interactive shell This is any shell which presents 109 a prompt to a human and waits for input A login shell is also an interactive shell A way you can get a non login interactive shell is say a shell inside xterm Any shell that was created by some other way besides logging in is a non login shell Finally there are non interactive shells These shells are used for executing a file of commands much like MS DOS s batch
124. have no intention of using vi as your regular editor a basic knowledge of vi can only be an asset A 2 Quick Ed Tutorial The aim of this tutorial is to get you started using ed ed is designed to be easy to use and requires little training to get started The best way to learn is to practice so follow the instructions and try the editor before discounting its practical advantages A 2 1 Creating a file ed is only capable of editing one file at a time Follow the next example to create your first text file using ed home larry ed a This is my first text file using Ed This is really fun w firstone txt home larry q You can verify the file s contents using the Unix concatenate utility home larry cat firstone txt The above example has illustrated a number of important points When invoking ed as above you will have an empty file The key a is used to add text to the file To end the text entering session a period 7 is used in the first column of the text To save the text to a file the key a is used in combination with the file s name and finally the key a is used to exit the editor The most important observation is the two modes of operation Initially the editor is in command mode A command is defined by characters so to ascertain what the user s intention is ed uses a text mode and a command mode A 2 2 editing a existing file To add a line of text to an existing file follow the next e
125. he export command as meaning Please export this variable out to the environment where I will be calling programs so that its value is visible to them There are actually reasons to call it export as you ll see later This particular variable is used by Phil Zimmerman s infamous public key encryption program pgp By default pgp uses your home directory as a place to find certain files that it needs containing encryption keys and also as a place to store temporary files that it creates when it s running By setting variable PGPPATH to this value I have told it to use the directory home larry secrets pgp instead I had to read the pgp manual to find out the exact name of the variable and what it does but it is farily standard to use the name of the program in capital letters prepended to the suffix PATH It is also useful to be able to query the environment hnome larry echo SPGPPATH hnome larry pgp home larry Notice the you prefix an environment variable with a dollar sign in order to extract the variable s value Had you typed it without the dollar sign echo would have simply echoed its argument s home larry echo PGPPATH PGPPATH home larry The is used to evaluate environment variables but it only does so in the context of the shell that is when the shell is interpreting When is the shell interpreting Well when you are typing commands at the prompt or when bash is reading co
126. hen X is invoked It can do anything any other shell script can do but of course it makes the most sense to use it for starting up various X programs and setting window system parameters The last com mand in the xinitrc is usually the name of a window manager to run for example usr bin X11 twm What sort of thing might you want to put ina xinitrc file Perhaps some calls to the xsetroot program to make your root background window and mouse cursor look the way you want them to look Calls to xmodmap which tells the server how to interpret the signals from your keyboard Any other programs you want started every time you run X for example xclock Here is some of my xinitrc yours will almost certainly look different so this is meant only as an example bin sh The first line tells the operating system which shell to use executable you can make it so with chmod x xinitrc in interpreting this script The script itself ought to be marked as xmodmap is a program for telling the X server how to interpret your keyboard s signals It is definitely worth learning about You can do man xmodmap xmodmap help xmodmap grammar and more I don t guarantee that the expressions below will mean anything on mine xmodmap e clear Lock xmodmap keycode 176 Control_R xmodmap e add control Control_R xmodmap e clear Mod2 xmodmap e add Modl Alt_L Alt_R xset
127. hink might be a Meta key and type x If you see a little prompt appear in the minibuffer like this M x then you ve found it To get rid of the prompt and go back to your Emacs buffer type C g If you didn t get a prompt then there is still one solution You can use the key as a Meta key But instead of holding it down while you type the next letter you have to tap it and release it quickly and then type the letter This method will work whether or not you have a real Meta key so it s the safest way to go Try tapping and then typing x now You should get that tiny prompt again Just use C g to make it go away C g is the general way in Emacs to quit out of something you don t mean to be in It usually beeps annoyingly at you to let you know that you have interrupted something but that s fine since that s what you intended to do if you typed C g 4 66 The notation M x is analogous to C x substitute any character for x If you have found a real Meta key use that otherwise just use the key I will simply write M x and you ll have to use your own Meta key 4Occasionally even one C g isn t enough to persuade Emacs that you really wanted to interrupt what you re doing Just keep at it and Emacs will usually return to a saner mode 8 6 Cutting Pasting Killing and Yanking Emacs like any good editor allows you to cut and paste blocks of text In order to do this you need a way to define the s
128. home larry cd report home larry report ls F 1993 1 1994 1 datal data5 1993 2 data new data2 hnome larry report echo 199 1993 1 1993 2 1994 1 nome larry report echo 4 1994 1 hnome larry report echo 2 1993 2 data2 home larry report As you can see the shell expands the wildcard and passes all of the files to the program you tell it to run This raises an interesting question what happens if there are no files that meet the wildcard specification Try echo rc fr og and bash passes the wildcard specification verbatim to the program Other shells like tcsh will instead of just passing the wildcard verbatim will reply No match Here s the same command run under tcsh mousehouse gt echo rc fr og echo No match mousehouse gt The last question you might want to know is what if I wanted to have data echoed back at me instead of the list of file names Well under both bash and t csh just include the string in quotes hnome larry report echo data mousehouse gt echo data data OR data home larry report mousehouse gt 6 1 2 The Question Mark In addition to the asterix the shell also interprets a question mark as a special character A question mark will match one and only one character For instance 1s etc will display all two letter files in the the et c directory 6 2 Time Saving with bash 6 2 1 Command Line Editing Occasionally you ve typed a long command to bash an
129. ice that the word Fill has been added to the right side As long as it s there Emacs will fill wrap text automatically You can turn it off by typing M x auto fill mode again it s a toggle command The inconvenience of typing long function names in the minibuffer is lessened because Emacs does completion on function names the same way it does on file names Therefore you should rarely find yourself typing in the whole function name letter by letter If you re not sure whether or not you can use completion just hit Tab It can t hurt the worst thing that will happen is that you ll just get a tab character and if you re lucky it ll turn out that you can use completion 8 9 Asking Emacs for Help Emacs has extensive help facilities so extensive in fact that we can only touch on them here The most basic help features are accessed by typing C h and then a single letter For example C h k gets help on a key it prompts you to type a key then tells you what that We call C q a key even though it is produced by holding down and pressing q because it is a single ASCII character key does C h t brings up a short Emacs tutorial Most importantly C h C h C h gets you help on help to tell you what s available once you have typed C h the first time If you know the name of an Emacs function save buf fer for example but can t remember what key sequence invokes it then use C h w for where is
130. ils You should have received a copy of the GNU Library General Public License along with this library if not write to the Free Software Foundation Inc 675 Mass Ave Cambridge MA 02139 USA Also add information on how to contact you by electronic and paper mail You should also get your employer if you work as a programmer or your school if any to sign a copyright disclaimer for the library if necessary Here is a sample alter the names Yoyodyne Inc hereby disclaims all copyright interest in the library Frob a library for tweaking knobs written by James Random Hacker signature of Ty Coon 1 April 1990 Ty Coon President of Vice That s all there is to it Bibliography 1 Almesberger Werner LILO Generic Boot Loader for Linux Available electronically tsx 11 mit edu July 3 1993 2 Bach Maurice J The Design of the UNIX Operating System Englewood Cliffs New Jersey Prentice Hall Inc 1986 3 Lamport Leslie BIEX A Document Preparation System Reading Massachusetts Addison Wesley Publishing Company 1986 4 Stallman Richard M GNU Emacs Manual eight edition Cambridge Massachusetts Free Software Foundation 1993 199
131. in that everyone understands that there is no warranty for this free software If the software is modified by someone else and passed on we want its recipients to know that what they have is not the original so that any problems introduced by others will not reflect on the original authors reputations Finally any free program is threatened constantly by software patents We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses in effect making the program proprietary To prevent this we have made it clear that any patent must be licensed for everyone s free use or not licensed at all The precise terms and conditions for copying distribution and modification follow Terms and Conditions 0 This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License The Program below refers to any such program or work and a work based on the Program means either the Program or any derivative work under copyright law that is to say a work containing the Program or a portion of it either verbatim or with modifications and or translated into another language Hereinafter translation is included without limitation in the term modification Each licensee 1s addressed as you Activities other than copying distribution and modification are not covered by thi
132. ing Their syntax is a little odd and they are used widely so please look at them exec command the command is executed and the action returns true if its final status is 0 that is regular execution of it The reason for the is rather logical find does not know where the command ends and the trick to put the exec action at the end of the command is not applicable Well the best way to signal the end of the command is to use the character used to do this by the shell itself that is but of course a semicolon all alone on the command line would be eaten by the shell and never sent to find so it has to be escaped The second thing to remember is how to specify the name of the current file within command as probably you did all the trouble to build the expression to do something and not just to print date This is done by means of the string Some old versions of find require that it must be embedded in white space not very handy if you needed for example the whole path and not just the file name but with GNU find could be anywhere in the string composing command And shouldn t it be escaped or quoted you surely are asking Amazingly I never had to do this neither under tcsh nor under bash sh does not consider and as special characters so it is not much of a problem My idea is that the shells know that is not an option making sense so they do not try to expand them luckily for find which can obtain
133. interpreting each parameter as another directory to create You can specify either the full pathname or a relative pathname report 1993 in the above example is a relative pathname home larry report 1993 mkdir home larry report 1993 chapl1 report 1993 chap2 home larry report 1993 ls F chap1 chap2 home larry report 1993 rmdir directory directory2 directoryNl The opposite of mkdir is rmdir remove directory rmdir works exactly like mkdir An example of rmdir is nome 1 rmdir nome 1 chap2 nome 1 home 1 rmdir home 1 arry report 1993 rmdir chapl chap3 chap3 No such file or directory arry report 1993 ls F arry report 1993 cd arry rmdir report 1993 report 1993 Directory not empty arry As you can see rmdir will refuse to remove a non existant directory as well as a directory that has anything in it Remember report 1993 has a subdirectory chap2 in it There is one more interesting thing to think about rmdir what happens if you try to remove your current directory Let s find out home larry cd report 1993 home larry report 1993 ls F chap2 home larry report 1993 rmdir chap2 home larry report 1993 rmdir rmdir Operation not permitted home larry report 1993 Another situation you might want to consider is what happens if you try to remove the parent of your current directory This turns out not to be a problem since the pare
134. introduce any command from now on The first word is the command in this case 1s Following the command are all the parameters Optional parameters are contained in brackets and Meta variables are slanted they re words that take the place of actual parameters For example above you see directory which should be replaced by the name of a real directory Options are a special case They re enclosed by brackets but you can take any one of them without using all of them For instance with just the three options given for 1s you have eight different ways of running the command with or without each of the options Contrast ls Rwithls F 4 3 2 The Current Directory and cd pwd Using directories would be cumbersome if you had to type the full path each time you wanted to access a directory Instead Unix shells have a feature called the current or present or working directory Your setup most likely displays your directory in your prompt home larry If it doesn t try the command pwd for present working directory Sometimes the prompt will display the machine name This is only really useful in a networked environment with lots of different machines mousehouse gt pwd home larry mousehouse gt cd directory As you can see pwd tells you your current directory a very simple command Most commands act by default on the current directory For instance 1s without any para
135. is Book Are you someone who should read this book Let s answer by asking some other questions Have you just gotten Linux from somewhere installed it and want to know what to do next Or are you a non Unix computer user who is considering Linux but wants to find out what it can do for you If you have this book the answer to these questions is probably yes Anyone who has Linux the free Unix clone written by Linus Torvalds on their PC but doesn t know what to do next should read this book In this book we 11 cover most of the basic Unix commands as well as some of the more advanced ones We ll also talk about GNU Emacs a powerful editor and several other large Unix applications 1 1 1 What You Should Have Done Before Reading This Book This book assumes that you have access to a Unix system It s a bit hard to learn without getting wet This Unix system is assumed to be an Intel PC running Linux This require 3 ment isn t necessary but when versions of Unix differ I ll be talking about how Linux acts nothing else Linux is available in many forms called distributions It is hoped that you ve found a complete distribution such as the Slackware Redhat or the MCC Interim versions and have installed it There are differences between the various distributions of Linux but for the most part they re small and unimportant You may find differneces in the examples in this book For the most part these should be
136. is a program for setting some other parameters of the X xset m3 2 amp mouse parameters xset s 600 5 amp screen saver prefs xset s noblank amp ditto xset fp home larry x fonts for cxterm To find out more do xset help Tell the X server to superimpose fish cursor over fish mask the resulting pattern as my mouse cursor 3The server just means the main X process on your machine the one with which all other X programs must communicate in order to use the display These other programs are known as clients and the whole deal is called a client server system your system I don t even guarantee that they mean anything on server and use xsetroot cursor home lab larry x fish cursor home lab larry x fish mask amp a pleasing background pattern and color xsetroot bitmap home lab larry x pyramid xbm bg tan todo xrdb here What about Xdefaults file You should do man xsetroot or xsetroot help for more information on the program used above A client program the imposing circular color clock by Jim Blandy usr local bin circles Maybe you d like to have a clock on your screen at all times usr bin X11 xclock digital amp Allow client X programs running at occs cs oberlin edu to display themselves here do the same thing for juju mcs anl gov xhost occs cs oberlin edu xhost juju mcs anl gov You could simply tell the X server to allow clients runni
137. k losing valuable data Unlike most versions of DOS it s a bad thing to just hit the power switch when you re done using the computer It is also bad to reboot the machine with the reset button without first taking proper precautions Linux in order to improve performance has a disk cache This means it temporarily stores part of the computer s permanent storage in RAM The idea of what Linux thinks the disk should be and what the disk actually contains is syn cronized every 30 seconds In order to turn off or reboot the computer you ll have to go through a procedure telling it to stop caching disk information If you re done with the computer but are logged in you ve entered a username and password first you must logout To do so enter the command logout All commands are sent by pressing return Until you hit return nothing will happen and you can delete what you ve done and start over hnome larry logout Welcome to the mousehouse Please have some chees mousehouse login 3The difference between RAM and a hard disk is like the difference between short term memory and long term memory Shutting off the power is like giving the computer a knock on the head it ll forget everything in short term memory But things saved in long term memory the hard disk will be okay The disk is thousands of times slower than RAM Now another user can login 3 3 3 Turning the Computer Off If this is a single user sy
138. l mode names have a command called lt modename gt mode which puts the current buffer into that mode Then to find out more information about that major mode I typed C h m which gets you help on the current major mode of the buffer you re in There s a slightly more useful mode called text mode which has the special com mands M S for center paragraph and M s which invokes center line M S by the way means exactly what you think it does hold down both the and the key and press S Don t just take my word for this go make a new buffer put it into text mode and type C h m You may not understand everything Emacs tells you when you do that but you should be able to get some useful information out of it Here is an introduction to some of the more commonly used modes If you use them make sure that you type C h m sometime in each one to find out more about each mode 8 11 Programming Modes 8 11 1 C Mode If you use Emacs for programming in the C language you can get it to do all the indentation for you automatically Files whose names end in c or h are automatically brought up in c mode This means that certain special editing commands useful for writing C programs are available In C mode is bound to c indent command This means that hitting the key does not actually insert a tab character Instead if you hit anywhere on a line Emacs automatically indents that line correctly for i
139. l options are of the form option value No space is allowed either before or after the equal sign this used to be annoying because the shell did not expand a filename in this situation but the version of bash present in Linux is rather smart so you don t have to worry about that It is important also to remember that all numbered values bytes and blocks above can be followed by a multiplier The possible choices are b for block which multiplies by 512 k for kilobytes 1024 w for word 2 and xm multiplies by m The meaning of options if explained below if filein and of fileout instruct dd to respectively read from filein and write to file out In the latter case the output file is truncated to the value given to seek or if the keyword is not present to O that is deleted before performing the operation But look below at option not runc ibs nn and obs nn specify how much bytes should be read or write at a time I think that the default is 1 block i e 512 bytes but I am not very sure about it certainly it works that way with plain files These parameters are very important when using special devices as input or output for example reading from the net should set ibs at 10k while a high density 3 5 floppy has as its natural block size 18k Failing to set these values could result not only in longer time to perform the command but even in timeout errors so be careful bs nn both reads and writes nn bytes at a time
140. l output those lines in a sorted order These types of programs are called filters because they take in text filter it and output the text slightly differently Both cat and sort are unusual filters cat is unusual because it reads in text and performs no changes on it sort is unusual because it reads in lines and doesn t output anything until after it s seen the EOF character Many filters run on a line by line basis they will read in a line perform some computations and output a different line 2The _ indicates that the user typed a space 3Hold down the key labeled Ctrl and press d then let go of both 4 2 Helping Yourself The man command displays reference pages for the command you specify For example home larryf man cat cat 1 cat 1 NAME cat Concatenates or displays files SYNOPSIS cat benstuvAET number number nonblank squeeze blank show nonprinting show ends show tabs show all help version file DESCRIPTION This manual page documents the GNU version of cat There s about one full page of information about cat Try running man now Don t expect to understand the manpage given Manpages usually assume quite a bit of Unix knowledge knowledge that you might not have yet When you ve read the page there s probably a little black block at the bottom of your screen similar to more or Line 1 This is the more promp
141. lder it contains pieces of paper or files A large folder can even hold other folders directories can be inside directories In Unix the collection of direc tories and files is called the file system Initially the file system consists of one directory called the root directory Inside this directory there are more directories and inside those directories are files and yet more directories Each file and each directory has a name It has both a short name which can be the same as another file or directory somewhere else on the system and a long name which is unique A short name for a file could be joe while it s full name would be hnome larry joe The full name is usually called the path The path can be decode into a sequence of directories For example here is how home larry joe is read home larry joe The initial slash indicates the root directory This signifies the directory called home It is inside the root directory This is the directory larry which is inside home joe is inside Larry A path could refer to either a directory or a filename so joe could be either All the items before the short name must be directories An easy way of visualizing this is a tree diagram To see a diagram of a typical Linux system look at Figure 4 1 Please note that this diagram isn t complete a full Linux system has over 8000 files and shows only some of the standard directories Thus there may be some directo
142. le o o e 000 136 10 3 1 The fingercommand e 136 10 3 2 Plans and Projects o o e e e 137 10 4 Using Systems by Remote o o 137 10 5 Exchanging Piles e uote A a HOR E AR Pr 138 10 6 Travelling the Web o o e B 139 11 Funny Commands 141 11 1 find the file searcher 142 11 1 1 Generalities jc e be a e 142 11 1 2 Expressions s M iguana SA A Re eo A a OSA WO 142 1113 HOPONS ww aes ashe A Gere ee tee A ah ae 143 IETA Tests bod back hee bb eh ode a ee Bape 144 FES ACHONS s 2 2 kad verted det a AO 146 17 1 6 Operators o ne it ee ele Ae ed eee eS 147 14137 Examples ui 2 gets a an Gale BORE me Bae eae 148 111 8 Alast word wc ao pb Rade A ee A 149 11 2 tar the tape archiver 5 66 Stk eee eR EER a Eee ee 150 V2 1 Introduchon veta Bas a eS oe SR Pe A Bodo 150 11 22 Main Options esca Sat ee ee eS A AA fat HGS 150 11 2 3 Modifiers ez ais ak Se ad A ow 150 11 2 4 Examples tia wea Sak ba RAR ee es eS 150 11 3 dd the data duplicator o oo a ee 150 11 3 1 Options 850 aia a A ee ERs 150 12 11 32 Examples er ait los a ea a Aa a i oa eg y 152 11 4 sort thedatasorter lt a a ea a a a ee 153 11 4 1 Introduction e 153 WA Opuons 400 A a Bree ed 153 1143 Examples on ci e oe ee oss 153 Errors Mistakes Bugs and Other Unpleasantries 155 12 1 Av
143. m eters displays the contents of the current directory We can change our current directory using cd For instance try home larry cd home homet ls F larry sam shutdown steve userl home If you omit the optional parameter directory you re returned to your home or original directory Otherwise cd will change you to the specified directory For instance home cd home larry cd cd home home cd usr usr cd local bin usr local bin As you can see cd allows you to give either absolute or relative pathnames An ab solute path starts with and specifies all the directories before the one you wanted A relative path is in relation to your current directory In the above example when I was in usr I made a relative move to local bin 1local is a directory under usr and bin is a directory under local cd home was also a relative directory change and The 1s the parent directory These are There are two directories used only for relative pathnames oD directory refers to the current directory and shortcut directories They exist in every directory but don t really fit the folder in a folder concept Even the root directory has a parent directory it s its own parent You ll see all the terms in this book present working directory current directory or working directory I prefer current directory although at times the other forms will
144. m You 1 find that it makes working at a Shell prompt a much more pleasant experience 9 1 4 Environment Variables Another major thing one does in a bashrc is set environment variables And what are environment variables Let s go at it from the other direction suppose you are reading the documentation for the program fruggle and you run across these sentences Fruggle normally looks for its configuration file frugglerc in the user s home directory However 1f the environment variable FRUGGLEPATH is set to a different filename it will look there instead Every program executes in an environment and that environment is defined by the shell that called the program The environment could be said to exist within the shell Now you see why shells are so important Imagine if you had to pass a whole environment by hand every time you called a program Programmers have a special routine for querying the environment and the fruggle pro gram makes use of this routine It checks the value of the environment variable FRUGGLEPATH If that variable turns out to be undefined then it will just use the file frugglerc in your home directory If it is defined however fruggle will use the variable s value which should be the name of a file that fruggle can use instead of the default frugglerc Here s how you can change your environment in bash nome larry export PGPPATH home larry secrets pgp You may think of t
145. make personal customizations to Emacs you should put them in emacs The most common customizations are keybindings so here s how to do them global set key C cl goto line global set key is a function of two arguments the key to be bound and the function to bind it to The word global means that this keybinding will be in effect in all major modes there is another function local set key that binds a key in a single buffer Above I have bound C c 1 to the function goto 1ine The key is described using a string The special syntax AC lt char gt means the key held down while the key lt char gt is pressed Likewise AM lt char gt indicates the key All very well but how did I know that the function s name was goto line I may know that I want to bind C c 1 to some function that prompts for a line number and then moves the cursor to that line but how did I find out that function s name This is where Emacs s online help facilities come in Once you have decided what kind of function you are looking for you can use Emacs to track down its exact name Here s one quick and dirty way to doit since Emacs gives completion on function names just type C h f whichis describe funct ion remember and then hit without typing anything This asks Emacs to do completion on the empty string in other words the completion will match every single function It may take a moment to build the completion lis
146. manager s configuration file see Section 9 2 1 for t wm or Section 9 2 2 for vwm 2 You can have more then one copy of xt erm running at the same time 3Many PCs have only two button mice If this is the case for you you should be able to emulate a middle button by using the left and right buttons simultaneously 5 4 4 Depth Since windows are allowed to overlap in X there is a concept of depth Even though the windows and the screen are both two dimensional one window can be in front of another partially or completely obscuring the rear window There are several operations that deal with depth e Raising the window or bringing a window to the front This is usually accomplished by clicking on a window s title bar with one of the buttons Depending on how the window manager is configured it could be any one of the buttons It is also possible that more then one button will do the job e Lowering the window or pushing the window to the back This can generally be accomplished by a different click in the title bar It is also possible to configure some window managers so that one click will bring the window foward if there is anything over it while that same click will lower it when it is in the front e Cycling through windows is another operation many window managers allow This brings each window to the front in an orderly cycle 5 4 5 Iconization There are several other operations that can obscure windows or hide them co
147. mary editor then the emacs file is quite important It is dealt with at length in Chapter 8 9 3 2 FTP Defaults Your netrc file allows you to have certain ftp defaults set before you run ftp Here is a small sample net rc machine floss life uiuc edu login larry password fishSticks machine darwin life uiuc edu login larry password fishSticks machine geta life uiuc edu login larry password fishSticks machine phylo life uiuc edu login larry password fishSticks machine ninja life uiuc edu login larry password fishSticks machine indy life uiuc edu login larry password fishSticks machine clone mcs anl gov login fogel password doorm machine osprey mcs anl gov login fogel password doorm machine tern mcs anl gov login fogel password doorm machine altair mcs anl gov login fogel password doorm machine dalek mcs anl gov login fogel password doorm machine juju mcs anl gov login fogel password doorm machine sunsite unc edu login anonymous password larry cs oberlin edu Each line of your netrc specifies a machine name a login name to use by default for that machine and a password This is a great convenience if you do a lot of ft p ing and are tired of constantly typing in your username and password at various sites The ftp program will try to log you in automatically using the information found in your net rc file if you ftp to one of the machines listed in the file You can tell ftp to ignore your netrc an
148. mmands from a file like bashrc it can be said to be interpreting the commands Figure 9 2 Some important environment variables HOME Your home directory home larry TE Your terminal type xterm vt100 or console SHE The path to your shell bin bash A list to search for programs bin usr bin usr local bin usr bin X11 There s another command that s very useful for querying the environment env env will merely list all the environment variables It s possible especially if you re using X that the list will scroll off the screen If that happens just pipe env through more env more A few of these variables can be fairly useful so P Il cover them Look at Figure 9 1 4 Those four variables are defined automatically when you login you don t set them in your bashrcor bash_login Let s take a closer look at the TERM variable To understand that one let s look back into the history of Unix The operating system needs to know certain facts about your con sole in order to perform basic functions like writing a character to the screen moving the cursor to the next line etc In the early days of computing manufacturers were constantly adding new features to their terminals first reverse video then maybe European character sets eventually even primitive drawing functions remember these were the days before windowing systems and mice However all of these new functions represented a pro
149. mming language In 1973 Unix was 9 rewritten in C instead of the original assembly language In 1977 Unix was moved to a new machine through a process called porting away from the PDP machines it had run on previously This was aided by the fact Unix was written in C since much of the code could simply be recompiled and didn t have to be rewritten In the late 1970 s AT amp T was forbidden from competing in the computing industry so it licensed Unix to various colleges and universities very cheaply It was slow to catch on outside of academic institutions but was eventually popular with businesses as well The Unix of today is different from the Unix of 1970 It has two major variations System V from Unix System Laboratories USL a subsiderary of Novell and the Berkeley Software Distribution BSD The USL version is now up to its forth release or SVR43 while BSD s latest version is 4 4 However there are many different versions of Unix besides these two Most commercial versions of Unix derive from one of the two groupings The versions of Unix that are actually used usually incorporate features from both variations Current commercial versions of Unix for Intel PCs cost between 500 and 2000 2 2 Linux History The primary author of Linux is Linus Torvalds Since his original versions it has been improved by countless numbers of people around the world It is a clone written entirely from scratch of the Unix operating
150. modifying or adding to a program and simply using it Linking a program with a library without changing the library is in some sense simply using the library and is analogous to running a utility program or application program However in a textual and legal sense the linked executable is a combined work a derivative of the original library and the ordinary General Public License treats it as such Because of this blurred distinction using the ordinary General Public License for li braries did not effectively promote software sharing because most developers did not use the libraries We concluded that weaker conditions might promote sharing better However unrestricted linking of non free programs would deprive the users of those programs of all benefit from the free status of the libraries themselves This Library General Public License is intended to permit developers of non free programs to use free libraries while preserving your freedom as a user of such programs to change the free libraries that are incorporated in them We have not seen how to achieve this as regards changes in header files but we have achieved it as regards changes in the actual functions of the Library The hope is that this will lead to faster development of free libraries The precise terms and conditions for copying distribution and modification follow Pay close attention to the difference between a work based on the library and a work that uses the
151. mplementations of his shell and all those specific shell pro grams are called Bourne shells Another class of shells C shells originally implemented by Bill Joy are also common Traditionally Bourne shells have been used for shell scripts and compatibility with the original sh while C shells have been used for interactive use C shells have had the advantages of having better interactive features but somewhat harder programming features Linux comes with a Bourne shell called bash written by the Free Software Foun dation bash stands for Bourne Again Shell one of the many bad puns in Unix It is an advanced Bourne shell it contains the standard programming features found in all Bourne shells with many interactive features commonly found in C shells bash is the default shell to use running Linux When you first login the prompt is displayed by bash and you are running your first Unix program the bash shell As long as you are logged in the bash shell will constantly be running 4 1 1 A Typical Unix Command The first command to know is cat To use it type cat and then return home larry cat If you now have a cursor on a line by itself you ve done the correct thing There are several variances you could have typed some would work some wouldn t e If you misspelled cat you would have seen home larry ct ct command not found home larry Thus the shell informs you that it couldn t find a program n
152. mpletely First is the idea of iconization Depending on the window manager this can be done in many different ways In twm many people configure an icon manager This is a special window that contains a list of all the other windows on the screen If you click on a name depending on the setup it could be with any of the buttons the window disappears it is iconified The window is still active but you can t see it Another click in the icon manager restores the window to the screen This is quite useful For instance you could have remote xterms to many different computers that you occasionally use However since you rarely use all of them at a given time you can keep most of the xterm windows iconified while you work with a small subset The only problem with this is it becomes easy to lose windows This causes you to create new windows that duplicate the functionality of iconified windows Other window managers might create actual icons across the bottom of the screen or might just leave icons on the root window 5 4 6 Resizing There are several different methods to resize windows under X Again it is dependent on your window manager and exactly how your window manager is configured The method many Microsoft Windows users are familiar with is to click on and drag the border of a window If your window manager creates large borders that change how the mouse cursor looks when it is moved over them that is probably the m
153. munications Corporation net scape only runs under X net scape tries to be as easy to use as possible and uses the Motif widget set to display avery Microsoft Windows like appearance The basic strategy for using net scape is that underlined blue words are links as are many pictures You can tell which pictures are links by clicking on them By clicking on these words with your left mouse button you ll be presented with a new page Linux supports many other browsers including the original web browser lynx lynx is a text browser it won t display any of the pictures that the Web is currently associated with but it will work without X lynx url It s somewhat harder to learn how to use lynx but generally playing with the arrow keys will let you get the hand of it The up and down arrow keys move between links on a given page which the right arrow key follows the current highlighted link The left arrow key will reload the previous page To quit lynx type q lynx has many other key commands consult the manpage for more Chapter 11 Funny Commands Well most people who had to do with the UNIX commands exposed in this chapter will not agree with this title What the heck You have just shown me that the Linux interface is very standard and now we have a bunch of commands each one working in a completely different way I will never remember all those options and you are saying that they are funny Yes you hav
154. n shorter Unfortunately bash cannot read your thoughts and you ll have to type all of shorter When you type Tab bash looks at what you ve typed and looks for a file that starts like that For instance if I type usr bin ema and then hit Tab bash will find usr bin emacs since that s the only file that begins usr bin ema on my system However if I type usr bin 1d and hit Tab bash beeps at me That s be cause three files usr bin 1d usr bin 1dd and usr bin 1d86 all start with usr bin 1ld on my system If you try a completion and bash beeps you can immediately hit again to get a list of all the files your start matches so far That way if you aren t sure of the exact spelling of your file you can start it and scan a much smaller list of files 6 3 The Standard Input and The Standard Output Let s try to tackle a simple problem getting a listing of the usr bin directory If all we dois ls usr bin some of the files scroll off the top of the screen How can we see all 2cp etc passwd this is a long file of the files 6 3 1 Unix Concepts The Unix operating system makes it very easy for programs to use the terminal When a program writes something to your screen it is using something called standard output Standard output abbreviated as stdout is how the program writes things to a user The name for what you tell a program is standard input stdin It s possible for a program to communicate with th
155. n lt Enter gt While these again have greater still lt Enter gt and greater still and so on lt Enter gt lt Esc gt Note that you press the key to end insertion and return to command mode A 3 2 Cursor movement commands h move the cursor one space to the left j move the cursor one space down k move the cursor one space up 1 move the cursor one space to the right These commands may be repeated by holding the key down Try moving around in your text now If you attempt an impossible movement e g pressing the letter k when the cursor is on the top line the screen will flash or the terminal will beep Don t worry it won t bite and your file will not be harmed A 3 3 Deleting text Xx delete the character at the cursor dd delete a line Move the cursor to the second line and position it so that it is underneath the apostrophe in em Press the letter x and the will disappear Now press the letter li to move into insert mode and type the letters th Press when you are finished A 3 4 File saving W save write to disk q exit Make sure you are in command mode by pressing the key Now type w This will save your work by writing it to a disk file The command for quitting vi is a If you wish to combine saving and quitting just type wq There is also a convenient abbreviation for wq ZZ Since much of your programming work will consist of running a program encountering a problem
156. n easily achieve new functionality and new features by combining the small parts programs in new ways And if new utilities appear and they do you can integrate them into your old toolbox When I write this document for example This was actually determined by the hardware Unix original ran on For some strange reason the resulting operating system was very useful on other hardware The basic design is good enough to still be used twenty five years later I m using these programs actively fvwm to manage my windows emacs to edit the text EXTFX to format it xdvi to preview it dvips to prepare it for printing and then lpr to print it If there was a different dvi previewer available I could use that instead of xdvi without changing my other programs At the current time my system is running thirty eight programs simultaneously Most of these are system programs that sleep until they have some specific work to do When you re using an operating system you want to minimize the amount of work you put into getting your job done Unix supplies many tools that can help you but only if you know what these tools do Spending an hour trying to get something to work and then finally giving up isn t very productive This book will teach you what tools to use in what situations and how to tie these various tools together The key part of an operating system is called the kernel In many operating systems like Unix OS 2 or VM
157. n of patent infringement or for any other reason not limited to patent issues conditions are imposed on you whether by court order agreement or otherwise that contradict the conditions of this License they do not excuse you from the conditions of this License If you cannot distribute so as to satisfy simultaneously your obligations under this License 12 13 and any other pertinent obligations then as a consequence you may not distribute the Library at all For example if a patent license would not permit royalty free redistribution of the Library by all those who receive copies directly or indirectly through you then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Library If any portion of this section is held invalid or unenforceable under any particular circumstance the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims this section has the sole purpose of protecting the integrity of the free software distribution system which is implemented by public license practices Many people have made generous con tributions to the wide range of software distributed through that system in reliance on consistent application of that system it is up to the author donor
158. n visible until you save the buffer You can save the buffer multiple times during an editing session the command to do so is just C x C s hold down and hit x and s while it s down okay so you probably already figured that out It s deliberately easy to type because saving your buffers is something best done early and often I m going to list a few more commands now along with the ones you ve learned already and you can practice them however you like Pd suggest becoming familiar with them before going any further Caf Move forward one character C b Move backward one character C n Go to next line C p Go to previous line C a Go to beginning of line C e Go to end of line C v Go to next page screenful of text G 1 Redraw the screen with current line in center C d Delete this character practice this one C k Delete text from here to end of line C x C s Save the buffer in its corresponding file Delete preceding character the one you just typed 8 2 Getting Started Quickly in X If all you re interesting in is editing a few files quickly an X user doesn t have to go much further beyond the menus at the top of the screen Buffers Files Tools Edit Search Help These menus are not available in text mode When you first start Emacs there will be four menus at the top of the screen Buffers File Edit and Help To use a menu simply move the mouse pointer over the name like File
159. nd show c they could even be mouse clicks or menu items whatever suits your program You should also get your employer if you work as a programmer or your school if any to sign a copyright disclaimer for the program if necessary Here is a sample alter the names Yoyodyne Inc hereby disclaims all copyright interest in the program Gnomo vision which makes passes at compilers written by James Hacker signature of Ty Coon 1 April 1989 Ty Coon President of Vice This General Public License does not permit incorporating your program into propri etary programs If your program is a subroutine library you may consider it more useful to permit linking proprietary applications with the library If this is what you want to do use the GNU Library General Public License instead of this License Appendix C The GNU Library General Public License GNU LIBRARY GENERAL PUBLIC LICENSE Version 2 June 1991 Copyright 1991 Free Software Foundation Inc 675 Mass Ave Cambridge MA 02139 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed This is the first released version of the library GPL It is numbered 2 because it goes with version 2 of the ordinary GPL Preamble The licenses for most software are designed to take away your freedom to share and change it By contrast the GNU General Public Licenses are intended to guarantee your
160. nd try to find it somewhere in the load path If it fails it tries it with the el extension failing that it uses the literal string as passed to load You can byte compile a file with the command M x byte compile file but if you modify the file often it s probably not worth it You should never byte compile your emacs though nor even give it a e1 extension After your emacs has been loaded Emacs searches for a file named default el to load Usually it s located in a directory in load path called site lisporlocal elisp or something see the example 1oad path I gave a while ago People who maintain Emacs on multi user systems use default el to make changes that will affect everyone s Emacs since everybody s Emacs loads it after their personal emacs Default el should not be byte compiled either since it tends to be modified fairly often Ifa person s emacs contains any errors Emacs will not attempt to load default el but instead will just stop flashing a message saying Error in init file or something If you see this message there s probably something wrong with your emacs There is one more kind of expression that often goes ina emacs The Emacs Lisp library sometimes offers multiple packages for doing the same thing in different ways This means that you have to specify which one you want to use or you ll get the default package which is not always the best one for all purposes One area
161. nding with atime hes hes barn born burn hes VerD VerE VerF hes Ver followed by any non digit hes their therr there theie hes any word vi uses ex command mode to perform search and replace operations All commands which start with a colon are requests in ex mode The search and replace command allows regular expression to be used over a range of lines and replace the matching string The user can ask for confirmation before the substitution is performed It may be well worth a review of line number representation in the ed tutorial lt start gt lt finish gt s lt find gt lt replace gt g General command 1 s the The g s the The tr DS E13 s the The sss saes g gc Search th ntire file and replace the with The o means the complete file Same as above Delete the contents from the current to 5th line Replace the with The but ask before substituting Delete the first four characters on each line The search command is very powerfull when combined with the regular expression search strings If the directive is not included then the change is performed only on the first occurance of a match on each line Sometimes you may want to use the original search string in the replacement result You could retype the command on the line but vi allows the replacement string to contain some special characters 1 5s help amp ing g Replaces help with helping on the fir
162. nds are get and put get will transfer a file from the remote system locally and put will take a file on the local system and put in on the remote one Both commands work on the directory in which you started ftp locally and your current directory which you could have changed through cd remotely One common problem with ftp is the distinction between text and binary files ftp is a very old protocol and there use to be advantages to assuming that files being transferred are text files Some versions of ftp default to this behavior which means any programs that get sent or received will get corrupted For safety use the binary command before using get or put To exit ftp use the bye command 10 6 Travelling the Web World Wide Web or WWW is a popular use of the Internet It consists of pages each associated with its own URL uniform resource locator URLs are the funny sequence of in the form http www rutgers edu Pages are generally written in HTML hypertext markup language HTML allows the writer of a document to link certain words or phrases or pictures to other documents anywhere else in the Web When a user is reading one document she can quickly move to another by clicking on a key word or a button and been presented with another document possibly from thousands of miles away netscape url The most popular web browser on Linux is net scape which is a commercial browser sold and given away by Netscape Com
163. ng o Plan home larry finger Login ame Tty Idle Login Time Office larry Larry Greenfield il 3 51 Dec 25 12 50 larry Larry Greenfield po Dec 25 12 51 home larry The s option tells finger to always display the short form what you normally get when you finger a machine and the 1 option tells it to always use the long form even when you finger a machine The p option tells finger that you don t want to see forward plan or project files and m tells finger that if you asked for information about a user only give information about an account name don t try to match the name with a real name 10 3 2 Plans and Projects Now what s a plan and a project anyway They re files stored in a user s home directory that are displayed whenever they re fingered You can create your own plan and project files the only restriction is that only the first line of a project file is displayed Also everybody must have execute privileges in your home directory chmod a x and everybody has to be able to read the plan and project files chmod a r plan project 10 4 Using Systems by Remote telnet remote system The principal way of using a remote Unix system is through telnet telnet is usually a fairly simple program to use Office Phone home larry telnet lionsden Trying 128 2 36 41 Connected to lionsden Escape character is 7 lionsden login As you can see after I issue
164. ng on any other host a host being a remote machine to display here but this is a security hol those clients might be run by someone else and watch your keystrokes as you type your password or something However if you wanted to do it anyway you could use a to stand for all possible hostnames instead of a specific hostname like this xhost And finally run the window manager usr bin X11 twm Some people prefer other window managers I use twm but fvwm is often distributed with Linux too usr bin X11 fvwm Notice that some commands are run in the background i e they are followed with a 82 while others aren t The distinction is that some programs will start when you start X and keep going until you exit these get put in the background Others execute once and then exit immediately xset root is one such it just sets the root window or cursor or whatever and then exits Once the window manager has started it will read its own init file which controls things like how your menus are set up which positions windows are brought up at icon control and other earth shakingly important issues If you use twm then this file is twmrc in your home directory If you use fvwm then it s fvwmrc etc PI deal with only those two since they re the window managers you ll be most likely to encounter with Linux 9 2 1 Twm Configuration The twmrc is not a shell script it s actually written in a l
165. niquely you can just hit to complete it or to show possible completions if there are more than one Space also has a role in filename completion in the minibuffer similar to but P 11 let you experiment to find out how the two differ Once you have the full file name in the minibuffer hit Return and Emacs will bring up a buffer displaying that file In Emacs this process is known as finding a file Go ahead and find some other unimportant text file now and bring it into Emacs do this from our original buffer some_file txt Now you have a new buffer I ll pretend it s called another_file txt since I can t see your mode line Your original buffer seems to have disappeared you re probably wondering where it went It s still inside Emacs and you can switch back to it with C x b When you type this you will see that the minibuffer prompts you for a buffer to switch to and it names a default The default is the buffer you d get if you just hit at the prompt without typing a buffer name The default buffer to switch to is always the one most recently left so that when you are doing a lot of work between two buffers C x b always defaults to the other buffer which saves you from having to type the buffer name Even if the default buffer is the one you want however you should try typing in its name anyway Notice that you get the same sort of completion you got when finding a file hitting completes as much of a b
166. nore it for now we won t be making much use of the minibuffer for a while Before you actually change any of the text in the file you need to learn how to move around The cursor should be at the beginning of the file in the upper left corner of the screen To move forward type C f that is hold down the key while you press f for forward It will move you forward a character at a time and if you hold both keys down your system s automatic key repeat should take effect in a half second or so Notice how when you get to the end of the line the cursor automatically moves to the next line C b for backward has the opposite behavior And while we re at it C n and C p take you to the next and previous lines respectively Using the control keys is usually the quickest way of moving around when you re edit ing The goal of Emacs is to keep your hands over the alpha numeric keys of the keyboard where most of your work gets done However if you want to the arrow keys should also work In fact when you re using X you should be able to position the mouse pointer and click with the left button to move the cursor where you want However this is very slow you have to move your hand all the way to your mouse Most people who use Emacs primarily use the keyboard for getting around Use C p and C b to get all the way back to the upper left corner Now keep C b held a little longer You should hear an anno
167. nsole switching under Linux many things done at once For example I typically run Emacs on VC 1 and do most of my work there while having a communications program up on VC 3 so I can be downloading or uploading files by modem while I work or running jobs on remote machines and keep a shell up on VC 2 just in case I want to run something else without tying up VC 1 Figure 6 1 A summary of commands and keys used in job control fg job bg job kill job PID jobs This is a shell command that returns a job to the foreground To find out which one this is by default type jobs and look for the one with the Parameters Optional job number The default is the process identified with When an s is added to the end of the command line it tells the command to run in the background automatically This process is then subject to all the usual methods of job control detailed here This is a shell command that causes a suspended job to run in the back ground To find out which one this is by default type jobs and look for the one with the Parameters Optional job number The default is the process identified with This is a shell command that causes a background job either suspended or running to terminate You should always specify the job number or PID and if you are using job numbers remember to precede them with as Parameters Either the job number preceded by or PID no is nec essary More than one pr
168. nt of your current directory isn t empty so it can t be removed 4 4 Moving Information All of these fancy directories are very nice but they really don t help unless you have some place to store you data The Unix Gods saw this problem and they fixed it by giving the users files We will learn more about creating and editing files in the next few chapters The primary commands for manipulating files under Unix are cp mv and rm They stand for copy move and remove respectively 4 4 1 cp Like a Monk cp i source destination cp i filel file2 fileN destination directory cp is a very useful utility under Unix and extremely powerful It enables one person to copy more information in a second than a fourteenth century monk could do in a year Be careful with cp if you don t have a lot of disk space No one wants to see a Disk full message when working on important files cp can also overwrite existing files without warning P 11 talk more about that danger later We ll first talk about the first line in the command template The first parameter to cp is the file to copy the second is where to copy it You can copy to either a different filename or a different directory Let s try some examples 7 cp has two lines in its template because the meaning of the second parameter can be different depending on the number of parameters home larry ls F etc passwd etc passwd home larry cp etc pas
169. nted to see how many files that ended with c there are try ls c we ZW spell filel file2 fileN nimals are very interesting creatures One of my favorite animals is spel is a very simple Unix spelling program usually for American English spe11 1s a filter like most of the other programs we ve talked about which sucks in an ASCII text file and outputs all the words it considers misspellings spe11 operates on the files listed in the command line or if there weren t any there stdin A more sophisticated spelling program ispell is probably also available on your machine ispell will offer possible correct spellings and a fancy menu interface if a filename is specified on the command line or will run as a filter like program if no files are specified While operation of ispel 1 should be fairly obvious consult the man page if you need more help cmp file file2 cmp compares two files The first must be listed on the command line while the second is either listed as the second parameter or is read in from standard input cmp is very simple and merely tells you where the two files first differ diff filel file2 One of the most complicated standard Unix commands is called diff The GNU version of diff has over twenty command line options It is a much more powerful version of cmp and shows you what the differences are instead of merely telling you where the first one is Since talking about even a
170. nted to send mail to a user named sam home larry mail sam Subject The user documentation Just testing out the mail system EOT home larry The mail program is very simple Like cat it accepts input from standard input one line at a time until it gets the end of text character on a line by itself Ctrl d So to send my message off I had to hit return and then Ctrl d mail is the quickest way to send mail and is quite useful when used with pipes and redirection For instance if I wanted to mail the file report1 to Sam I could mail sam lt report1 orIcouldhaveevenrun sort reportl mail sam However the downside of using mail to send mail means a very crude editor You can t change a line once you ve hit return So I recommend you send mail when not using a pipe or redirection is with Emacs s mail mode It s covered in Section 8 10 10 1 2 Reading Mail mail user The mail program offers a clumsy way of reading mail If you type mail without any parameters you ll see the following home larry mail No mail for larry home larry I m going to send myself some mail so I can play around with the mailreader home larry mail larry Subject Frogs and toads EOT home larry echo snakes mail larry home larry mail ail version 5 5 6 1 90 Type for help usr spool mail larry 2 messages 2 new gt N 1 larry Tue Aug 30 18 11 10 211 Frogs N 2 larry Tue Aug 30
171. nteraction mode Usually there is a buffer called scratch that is al ready in this mode If you can t find one create a new buffer of any name and type M x lisp interaction mode inside it Now you have a workspace for interacting with the Emacs Lisp interpreter Type this load path and then press C 3 at the end of it In lisp interaction mode C 4 is bound to eval print last sexp An sexp is an s expression which means a balanced group of parentheses including Sometimes unofficially called Elisp none Well that s simplifying it a little but you ll get a feel for what they are as you work with Emacs Lisp Anyway evaluating 1oad path should get you something like this load path C i usr lib emacs site lisp vm 5 35 home kfogel elithp usr lib emacs site lisp usr lib emacs 19 19 lisp It won t look the same on every system of course since it is dependant on how Emacs was installed The above example comes from my 386 PC running Linux As the above indicates load path is a list of strings Each string names a directory that might contain Emacs Lisp files When Emacs needs to load a file of Lisp code it goes looking for it in each of these directories in order If a directory is named but does not actually exist on the filesystem Emacs just ignores it When Emacs starts up it automatically tries to load the file emacs in your home directory Therefore if you want to
172. o goMIPS A MIP stands for a million instructions per second and a BogoMIP 1s a bogus MIP how many times the computer can do absolutely nothing in one second Since this loop doesn t actually do anything the number is not actually a measure of how fast the system is Linux uses this number when it needs to wait for a hardware device Calibrating delay loop ok 33 28 BogoMIPS 3 The Linux kernel also tells you a little about memory usage Memory 23180k 24576k available 544k kernel code 384k reserved 468k data This said that the machine had 24 megabytes of memory Some of this memory was reserved for the kernel The rest of it can be used by programs This is the temporary 5 Compiled is the process by which a computer program that a human writes gets translated into something the computer understands A feature that has been compiled in has been included in the program RAM that is used only for short term storage Your computer also has a permanent memory called a hard disk The hard disk s contents stay around even when power is turned off Throughout the bootup procedure Linux tests different parts of the hardware and prints messages about these tests This processor honours the WP bit even when in supervisor mode Good Now Linux moves onto the network configuration The following should be de scribed in The Linux Networking Guide and is beyond the scope of this document Swan
173. o more and more until Emacs can no longer remember what changes were made 8 13 Customizing Emacs Emacs is so big and so complex that it actually has its own programming language I m not kidding to really customize Emacs to suit your needs you have to write programs in this language It s called Emacs Lisp and it s a dialect of Lisp so if you have previous experience in Lisp it will seem quite friendly If not don t worry I m not going to go into a great deal of depth because it s definitely best learned by doing To really learn about programming Emacs you should consult the Info pages on Emacs Lisp and read a lot of Emacs Lisp source code Most of Emacs s functionality is defined in files of Emacs Lisp code Most of these files are distributed with Emacs and collectively are known as the Emacs Lisp library This library s location depends on how Emacs was installed on your system common lo cations are usr lib emacs lisp usr lib emacs 19 19 lisp etc The 19 19 is the version number of Emacs and might be different on your system You don t need to poke around your filesystem looking for the lisp library because Emacs has the information stored internally in a variable called load path To find out the value of this variable it is necessary to evaluate it that is to have Emacs s lisp in terpreter get its value There is a special mode for evaluating Lisp expressions in Emacs called lisp i
174. o vi and helps explain where its command set originates A 3 Quick Vi Tutorial The aim of this tutorial is to get you started using the vi editor This tutorial assumes no vi experience so you will be exposed to the ten most basic vi commands These fundamental commands are enough to perform the bulk of your editing needs and you can expand your vi vocabulary as needed It is recommended you have a machine to practice with as you proceed through the tutorial A 3 1 Invoking vi To invoke vi simply type the letters vi followed by the name of the file you wish to create You will see a screen with a column of tildes along the left side vi is now in command mode Anything you type will be understood as a command not as text to be input In order to input text you must type a command The two basic input commands are the following insert text to the left of the cursor a append text to the right of the cursor Since you are at the beginning of an empty file it doesn t matter which of these you type Type one of them and then type in the following text a poem by Augustus DeMorgan found in The Unix Programming Environment by B W Kernighan and R Pike Great fleas have little fleas lt Enter gt upon their backs to bite em lt Enter gt And little fleas have lesser fleas lt Enter gt and so ad infinitum lt Enter gt And the great fleas themselves in turn lt Enter gt have greater fleas to go o
175. ocess or job can be specified on one line This shell command just lists information about the jobs currently run ning or suspending Sometimes it also tells you about ones that have just exited or been terminated This is the generic interrupt character Usually 1f you type it while a pro gram is running in the foreground it will kill the program sometimes it takes a few tries However not all programs will respond to this method of termination This key combination usually causes a program to suspend although a few programs ignore it Once suspended the job can be run in the background or killed Chapter 7 Powerful Little Programs better pout cry better watchout lpr why santa claus lt north pole gt town cat etc passwd gt list ncheck list ncheck list cat list grep naughty gt nogiftlist cat list grep nice gt giftlist santa claus lt north pole gt town who grep sleeping who grep awake who egrep bad good for goodness sake be good 73 7 1 The Power of Unix The power of Unix is hidden in small commands that don t seem too useful when used alone but when combined with other commands either directly or indirectly produce a system that s much more powerful and flexible than most other operating systems The commands I m going to talk about in this chapter include sort grep more cat wc spell diff head and tail Unfortunately it isn t totally intuitive what
176. oiding ElTOTS 0 iii GA be we Be Ce be ae eS 155 12 2 What to do When Something Goes Wrong 157 12 3 Not Your Fault oa vacate PAP Ra AA oo le y 157 12 3 1 When Is ThereaBug o 157 12 3 2 ReportingaBug o 158 Introduction to Vi 159 A 1 A Quick History of Vi o o e o 159 A 2 Quick Ed Tutorial e 160 Ad Ay Create ale ts A A its a 160 A 2 2 editing aexistingfile o o 161 A 2 3 Line numbers in detail o 162 A 3 Quick Vi Tutorial 22 0866 Aa ee ee Be a eB ed 164 ASA INVOKING Vi eg le Aa Sed ced Bude Rae eee Ada SS 164 A 3 2 Cursor movementcommands 005 165 A 3 3 Deleting text 8 oe ha See ea le Be eed 165 ASA File saving cogot ank a Hake dogs eek sata Ge meee Bo 165 ALT What s Mex ca o Bet ee Sk Bo he Wk ee Bee a 166 AA Advanced Vi Tutorial o o e e e 166 A 4 1 Moving around 2 002000000 166 AcAD Modifing Textura tt a Pe Re ei de A ay 168 A 4 3 Copying and Moving sections of text 171 A 4 4 Searching and replacing text o 173 B The GNU General Public License 177 C The GNU Library General Public License 187 Chapter 1 Introduction How much does it cost to entice a dope smoking Unix system guru to Dayton Brian Boyle Unix World s First Annual Salary Survey 1 1 Who Should Read Th
177. only half the keystrokes What happens is that when you type 11 and hit Return Bash intercepts it Figure 9 1 Some sample aliases for bash alias ls l1s F give characters at the end of listing alias 11 1s 1 special ls alias la ls a alias ro rm rm this removes backup files created by Emacs alias rd rmdir saves typing alias md mkdir alias pu pushd pushd popd and dirs weren t covered in this alias po popd manual you might want to look them up alias ds dirs in the bash manpage these all are just keyboard shortcuts alias to telnet cs oberlin edu alias ta telnet altair mcs anl gov alias tg telnet wombat gnu ai mit edu alias tko tpalk kold cs oberlin edu alias tjo talk jimb cs oberlin edu alias mroe more spelling correction alias moer more alias email emacs f rmail my mail reader alias ed2 emacs d floss 0 fg grey95 bg grey50 one way of invoking emacs because it s watching for aliases replaces it with Is 1 and runs that instead There is no actual program called 11 on the system but the shell automatically translated the alias into a valid program Some sample aliases are in Figure 9 1 3 You could put them in your own bashrc One especially interesting alias is the first one With that alias whenever someone types ls they automatically have a F flag tacked on The alias doesn t try to expand itself again This is
178. ons are prohibited by law if you do not accept this License Therefore by modifying or distributing the Program or any work based on the Pro gram you indicate your acceptance of this License to do so and all its terms and conditions for copying distributing or modifying the Program or works based on it Each time you redistribute the Program or any work based on the Program the recipient automatically receives a license from the original licensor to copy distribute or modify the Program subject to these terms and conditions You may not impose any further restrictions on the recipients exercise of the rights granted herein You are not responsible for enforcing compliance by third parties to this License If as a consequence of a court judgment or allegation of patent infringement or for any other reason not limited to patent issues conditions are imposed on you whether by court order agreement or otherwise that contradict the conditions of this License they do not excuse you from the conditions of this License If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations then as a consequence you may not distribute the Program at all For example if a patent license would not permit royalty free redistribution of the Program by all those who receive copies directly or indirectly through you then the only way you could satisfy both it and this License would be
179. operate differently To scroll upwards that is display ma terial above what is currently visible you can click the rightmost mouse button anywhere in the scroll bar To scroll downwards click the left mouse button anywhere in the scroll bar You can also jump to a particular location in the displayed material by clicking the middle mouse button anywhere in the scroll bar This causes the window to display material starting at that point in the document Motif scroll bars A Motif scroll bar acts much more like a Microsoft Windows or Macintosh scroll bar An example of one is on the right in Figure 5 4 Notice that in addition to the bar it has arrows above and below it These are used for fine tuning clicking either the left or middle buttons on them will scroll a small amount such as one line the right button does nothing The behavior of clicking inside the scroll bar is widely different for Motif scroll bars than Athena scroll bars The right button has no effect Clicking the left button above the current position scrolls upward Similarly clicking below the current position scrolls downward Clicking and holding the left button on the current position allows one to move the bar at will Releasing the left button positions the window Clicking the middle button anywhere on the bar will immediately jump to that location similar to the behavior of the Athena middle button However instead of starting to display the data at the position
180. ory you want a list for Some commands have special parameters called options or switches To see this try home larryHf ls F bin etc install mnt root user var dev home lib proc tmp usr vmlinux home larry The F is an option An option is a special kind of parameter that starts with a dash and modifies how the program runs but not what the program runs on For 1s F is an option that lets you see which ones are directories which ones are special files which are programs and which are normal files Anything with a slash is a directory We ll talk more about 1s s features later It s a surprisingly complex program Now there are two lessons to be learned here First you should learn what 1s does Try a few other directories that are shown in Figure 4 1 and see what they contain Naturally some will be empty and some will have many many files in them I suggest you try 1s both with and without the F option For example 1s usr local looks like home larry ls usr local archives bin emacs etc ka9q lib tcl home larry The second lesson is more general Many Unix commands are like 1s They have options which are generally one character after a dash and they have parameters Unlike 1s some commands require certain parameters and or options To show what commands generally look like we ll use the following form 1s aRF directory I ll generally use command templates like that before I
181. ou want to deal with more than one file at once in fact you might want to deal with many files at once For instance you might want to copy all the files beginning with data into a directory called backup You could do this by either running many cp commands or you could list every file on one command line Both of these methods would take a long time however and you have a large chance of making an error A better way of doing that task is to type home larry report ls F 1993 1 1994 1 datal data5 57 1993 2 data new data2 home larry report mkdir backup hnome larry report cp data backup home larry report ls F backup data new datal data2 data5 home larry report As you can see the asterix told cp to take all of the files beginning with data and copy them to backup Can you guess what cp d w backup would have done 6 1 1 What Really Happens Good question Actually there are a couple of special characters intercepted by the shell bash The character an asterix says replace this word with all the files that will fit this specification So the command cp data backup like the one above gets changed to cp data new datal data2 data5 backup before it gets run To illustrate this let me introduce a new command echo echo is an extremely simple command it echoes back or prints out any parameters Thus home larry echo Hello Hello home larry echo How are you How are you
182. ough News 10 3 Searching for People 10 3 1 The finger command The finger command allows you to get information on other users on your system and across the world Undoubtably the finger command was named based on the AT amp T advertisements exhorting people to reach out and touch someone Since Unix has its roots in AT amp T this was probably amusing to the author finger slpm user machine The optional parameters to finger may be a little confusing Actually it isn t that bad You can ask for information on a local user sam information on another machine Olionsden information on a remote user samOlionsden and just information on the local machine nothing Another nice feature is if you ask for information about a user and there isn t an account name that is exactly what you asked for it will try and match the real name with what you specified That would mean that if Iran finger Greenfield I would be told that the account sam exists for Sam Greenfield home larry finger sam Login sam Name Sam Greenfield Directory home sam Shell bin tcsh Last login Sun Dec 25 14 47 EST on tty2 No Plan home larry finger greenfie gauss rutgers edu gauss rutgers edu Login name greenfie In real life Greenfi Directory gauss ul greenfie Shell bin tcsh On since Dec 25 15 19 41 on ttyp0 from tiptop slip 6439 13 minutes Idle Time o unread mail Project You must be joki
183. ow there can be two different Scheme modes and what to do about it For now don t worry about it if things in your Emacs don t quite match up to what I say here A customizable editor means an unpredictable editor and there s no way around that You can run an interactive Scheme process in Emacs with the command M x run scheme This creates a buffer named scheme which has the usual Scheme prompt in it You can type in Scheme expressions at the prompt hit Return and Scheme will evaluate them and display the answer Thus in order to interact with the Scheme process you could just type all your function definitions and applications in at the prompt Chances are you have previously written Scheme source code in a file somewhere and it would be easier to do your work in that file and send the definitions over to the Scheme process buffer as necessary If that source file ends in ss or scm it will automatically be brought up in Scheme mode when you find it with C x C f If for some reason it doesn t come up in Scheme mode you can do it by hand with M x scheme mode This scheme mode is not the same thing as the buffer running the Scheme process rather the source code buffer s being in scheme mode means that it has special commands for communicating with the process buffer If you put yourself inside a function definition in the Scheme source code buffer and type C c C e then that definition will be
184. p usr bin X11 xtetris usr bin X11 xhextris usr bin X11 xroach usr bin X11 xclock analog usr bin X11 xclock digital This is the one I bound to the middle mouse button menu stuff Chores f title Sync bin sync Who who xmessag fil columns 80 lines 24 amp Xhost usr bin X11 xhost amp Rootclear home larry bin rootclear amp X functions that ar menu x X Stuff Xhost Refresh Source twmrc De Iconify Move Window Resize Window Destroy Window Window Ops wn Kill twm This is a submenu menu windowops Window Ops Show Icon Mgr sometimes convenient f title xhost f refresh Ewmrc iconify move resize destroy menu windowops nop Hh oh bh th Ph Ph Ph bh quit from above f title f showiconmgr Hide Icon Mgr Refresh Refresh Window twm version Focus on Root Source twmrc Cut File De Iconify DeIconify Move Window ForceMove Window Resize Window Raise Window Lower Window Raise or Lower Focus on Window Raise n Focus Destroy Window Kill twm Hh ohh h Ph Ph Ph Ph Ph Ph th Ph Ph Ph th th Ph Ph Ph th hideiconmgr refresh winrefresh version unfocus twmrc cutfile iconify deiconify move forcemove resize raise lower raiselower focus function raise n focus d
185. ps is shown below options affect the overall operation of find rather than the processing of a single file An example is follow which instructs find to follow symbolic links instead of just stating the inode They always return true tests are real tests for example empty checks whether the file is empty and can return true or false actions have also a side effect the name of the considered file They can return true or false too operators do not really return a value they can conventionally be considered as true and are used to build compress expression An example is or which takes the logical OR of the two subexpressions on its side Notice that when juxtaposing expression a and is implied Note that f ind relies upon the shell to have the command line parsed it means that all keyword must be embedded in white space and especially that a lot of nice characters have to be escaped otherwise they would be mangled by the shell itself Each escaping way backslash single and double quotes is OK in the examples the single character keywords will be usually quoted with backslash because it is the simplest way at least in my opinion But it s me who is writing these notes 11 1 3 Options Here there is the list of all options known by GNU version of find Remember that they always return true e daystart measures elapsed time not from 24 hours ago but from last midnight A true hacker probably won t understand the
186. puter on and off once a day is probably the best compromise between energy and wear amp tear on the system 3 4 Kernel Messages When you first start your computer a series of messages flash across the screen describing the hardware that is attached to your computer These messages are printed by the Linux kernel In this section I ll attempt to describe and explain those messages Naturally these messages differ from machine to machine I ll describe the messages I get for my machine The following example contains all of the standard messages and some specific ones In general the machine I m taking this from is a minimally configured one you won t see a lot of device specific configuration This was made with Linux version 1 3 55 one of the most recent as of this writing 1 The first thing Linux does is decides what type of video card and screen you have so it can pick a good font size The smaller the font the more that can fit on the screen on any one time Linux may ask you if you want a special font or it might have had a choice compiled in Console 16 point font 400 scans Console colour VGA 80x25 1 virtual console max 63 In this example the machine owner decided he wanted the standard large font at compile time Also note the misspelling of the word color Linus evidently learned the wrong version of English 2 The next thing the kernel will report is how fast your system is as measured by B
187. r free programs whose distri bution conditions are incompatible with these write to the author to ask for permis sion For software which is copyrighted by the Free Software Foundation write to the Free Software Foundation we sometimes make exceptions for this Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally NO WARRANTY 11 BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE THERE IS NO WARRANTY FOR THE LIBRARY TO THE EXTENT PERMITTED BY AP PLICABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE LIBRARY AS IS WITHOUT WARRANTY OF ANY KIND EITHER EXPRESSED OR IM PLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH YOU SHOULD THE LIBRARY PROVE DEFECTIVE YOU ASSUME THE COST OF ALL NECESSARY SERVICING REPAIR OR CORRECTION INNO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER OR ANY OTHER PARTY WHO MAY MODIFY AND OR REDISTRIBUTE THE LIBRARY AS PERMIT TED ABOVE BE LIABLE TO YOU FOR DAMAGES INCLUDING ANY GEN ERAL SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE LIBRARY INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
188. ral string like so 7 these two lines are ignored by the Lisp interpreter but the 7 s expression following them will be evaluated in full setq some literal string An awkward pause for no purpose It s a good idea to comment your changes to Lisp files because six months later you will have no memory of what you were thinking when you modified them If the comment appears on a line by itself precede it with two semicolons This aids Emacs in indenting Lisp files correctly You can find out about internal Emacs variables the same ways you find out about func tions Use C h v describe variable to make a completion list or use C h C a apropos Apropos differs from C h a command apropos in that it shows func tions and variables instead of just functions The default extension for Emacs Lisp files is e 1 as in c mode el However to make Lisp code run faster Emacs allows it to be byte compiled and these files of compiled Lisp code end in elc instead of e1 The exception to this is your emacs file which does not need the e1 extension because Emacs knows to search for it on startup To load a file of Lisp code interactively use the command M x load file It will prompt you for the name of the file To load Lisp files from inside other Lisp files do this load c mode force Emacs to load the stuff in c mode el or elc Emacs will first add the elc extension to the filename a
189. ries in that diagram that aren t on your system and your system almost certainly has directories not listed there 4 3 1 Looking at Directories with 1s Now that you know that files and directories exist there must be some way of manipulating them Indeed there is The command 1s is one of the more important ones It lists files If 5There may or may not be a limit to how deep the file system can go I ve never reached it one can easily have directories 10 levels deep you try 1s as a command you ll see hnome larry 1s home larry That s right you ll see nothing Unix is intensionally terse it gives you nothing not even no files if there aren t any files Thus the lack of output was 1s s way of saying it didn t find any files But I just said there could be 8000 or more files lying around where are they You ve run into the concept of a current directory You can see in your prompt that your current directory is home larry where you don t have any files If you want a list of files of a more active directory try the root directory home larry 1s bin etc install mnt root user var dev home lib proc tmp usr vmlinux home larry In the above command 1s the directory is a parameter The first word of the command is the command name and anything after 1t is a parameter Parameters generally modify what the program is acting on for 1s the parameters say what direct
190. right line and a pointer to where the full notice is found one line to give the program s name and an idea of what it does Copyright 19yy name of author This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Soft ware Foundation either version 2 of the License or at your option any later version This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABIL ITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details You should have received a copy of the GNU General Public License along with this program if not write to the Free Software Foundation Inc 675 Mass Ave Cambridge MA 02139 Also add information on how to contact you by electronic and paper mail If the program is interactive make it output a short notice like this when it starts in an interactive mode Gnomovision version 69 Copyright 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY for details type show w This is free software and you are welcome to redistribute it under certain conditions type show c for details The hypothetical commands show w and show c should show the appropriate parts of the General Public License Of course the commands you use may be called some thing other than show w a
191. rk complete source code means all the source code for all modules it contains plus any associated interface definition files plus the scripts used to control compilation and installation of the executable However as a special exception the source code distributed need not include anything that is normally distributed in either source or binary form with the major components compiler kernel and so on of the operating system on which the executable runs unless that component itself accompanies the executable If distribution of executable or object code is made by offering access to copy from a designated place then offering equivalent access to copy the source code from the same place counts as distribution of the source code even though third parties are not compelled to copy the source along with the object code You may not copy modify sublicense or distribute the Program except as expressly provided under this License Any attempt otherwise to copy modify sublicense or distribute the Program is void and will automatically terminate your rights under this License However parties who have received copies or rights from you under this License will not have their licenses terminated so long as such parties remain in full compliance You are not required to accept this License since you have not signed it However nothing else grants you permission to modify or distribute the Program or its deriva tive works These acti
192. rlin edu emacs d floss life uiuc edu 0 amp gnu rsh gate 1 gnu ai mit edu emacs d floss life uiuc edu 0 amp This allows me to invoke xterms on several different machines See the section on rhosts files for more information about how this works menu logins Logins f title here usr bin X11 xterm ls T hostname n hostname phylo rsh phylo xterm ls display floss 0 T phylo amp geta I rsh geta xterm ls display floss 0 T geta 4 darwin rsh darwin xterm ls display floss 0 T darwin amp ninja rsh ninja xterm ls display floss 0 T ninja amp indy rsh indy xterm ls display floss 0 T indy The xlock screensaver called with various options each of which gives a different pretty picture menu xlock Hop xlock mode hop amp Oix xlock mode qix amp Flame xlock mode flame amp Worm xlock mode worm amp Swarm xlock mode swarm amp Hop NL xlock mode hop nolock amp oix NEYT xlock mode qix nolock a Flame NL xlock mode flame nolock amp Worm NL xlock mode worm nolock amp Swarm NL xlock mode swarm nolock amp Miscellaneous programs I run occasionally menu misc Xload usr bin X11 xload XV 1 usr bin X11 xv amp Bitmap Tetris Hextris XRoach Analog Clock Digital Clock usr bin X11 bitma
193. rogram 6 5 Virtual Consoles Being in Many Places at Once Linux supports virtual consoles These are a way of making your single machine seem like multiple terminals all connected to one Linux kernel Thankfully using virtual consoles is one of the simplest things about Linux there are hot keys for switching among the consoles quickly To try it log in to your Linux system hold down the left key and press that is the function key number 2 5 You should find yourself at another login prompt Don t panic you are now on virtual console VC number 2 Log in here and do some things a few 1s s or whatever to confirm that this is a real login shell Now you can return to VC number 1 by holding down the left and pressing F1 Or you can move on to a third VC in the obvious way Att F3 Linux systems generally come with four VC s enabled by default You can increase this all the way to eight this should be covered in The Linux System Adminstrator s Guide It involves editing a file in etc or two However four should be enough for most people Once you get used to them VC s will probably become an indispensable tool for getting 7In general it s easier to just kill the job number instead of using PIDs 8Make sure you are doing this from text consoles if you are running X windows or some other graphical ap plication it probably won t work although rumor has it that X Windows will soon allow virtual co
194. rry Hmm is there any way to get it to actually run in the background while still leaving us the prompt for interactive work The command to do that is bg home larry bg 1 yes gt dev null amp home larry Now you ll have to trust me on this one after you typed bg yes gt dev null began to run again but this time in the background In fact if you do things at the prompt like 1s and stuff you might notice that your machine has been slowed down a little bit endlessly generating and discarding a steady stream of y s does take some work after all Other than that however there are no effects You can do anything you want at the prompt and yes will happily continue to sending its output into the black hole There are now two different ways you can kill it with the ki11 command you just learned or by putting the job in the foreground again and hitting it with an interrupt ctrl c Let s try the second way just to understand the relationship between fg and bg a little better home larry fg yes gt dev null now it s in the foreground again Imagine that I hit ctrl c to terminat home larry it There it s gone Now start up a few jobs running in simultaneously like this nome larry yes gt dev null amp 1 1024 home larry yes sort gt dev null 2 1026 home larry yes uniq gt dev null and here type ctrl z to suspend it please 3 Stopped yes uniq g
195. s License they are outside its scope The act of running the Program is not restricted and the output from the Program is covered only if its contents constitute a work based on the Program independent of having been made by running the Program Whether that is true depends on what the Program does You may copy and distribute verbatim copies of the Program s source code as you receive it in any medium provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty keep intact all the notices that refer to this License and to the absence of any warranty and give any other recipients of the Program a copy of this License along with the Program You may charge a fee for the physical act of transferring a copy and you may at your option offer warranty protection in exchange for a fee You may modify your copy or copies of the Program or any portion of it thus form ing a work based on the Program and copy and distribute such modifications or work under the terms of Section 1 above provided that you also meet all of these conditions a You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change b You must cause any work that you distribute or publish that in whole or in part contains or is derived from the Program or any part thereof to be licensed as a whole at no charge to all third parties under
196. s the processing of the command for the arguments in the command line while all other files down are considered e version just prints the current version of the program e xdev which is a misleading name instructs find not to cross device i e changing filesystem It is very useful when you have to search for something in the root filesys tem in many machines it is a rather small partition buta find would otherwise search the whole structure 11 1 4 Tests The first two tests are very simple to understand false always return false while true always return true Other tests which do not need the specification of a value are empty which returns true whether the file is empty and the couple nouser nogroup which return true in the case that no entry in etc passwd or etc group match the user group id of the file owner This is a common thing which happens in a multiuser sys tem a user is deleted but files owned by her remain in the strangest part of the filesystems and due to Murphy s laws take a lot of space Distributed filesystems allow files to appear like their local to a machine when they are actually located somewhere else Of course it is possible to search for a specific user or group The tests are uid nn and gid nn Unfortunately it is not possibile to give directly the user name but it is necessary to use the numeric id nn allowed to use the forms nn which means a value strictly greater than
197. scrol1 up which scrolls the buffer up by one screenful meaning that your position in the buffer moves down of course If you ever actually wanted to insert a Control character into the buffer then how would you do it After all the Control characters are ASCII characters although rarely used and you might want them in a file There is a way to prevent Control characters from being interpreted as commands by Emacs The key C q is bound to a special function named quoted insert All quoted insert does is read the next key and insert it literally into the buffer without trying to interpret it as a command This is how you can put Control characters into your files using Emacs Naturally the way to insert a C q is to press C q twice Emacs also has many functions that are not bound to any key For example if you re typing a long message you don t want to have to hit return at the end of every line You can have Emacs do it for you you can have Emacs do anything for you the command to do so is called auto fi11 mode but it s not bound to any keys by default In order to invoke this command you would type M x auto fill mode M x is the key used to call functions by name You could even use it to call functions like next 1line and previous 1line but that would be very inefficient since they are already bound to C n and C p By the way if you look at your mode line after invoking auto fi11 mode you will not
198. sea University Computer Society NET3 033 for Linux 1 3 50 IP Protocols ICMP UDP TCP Linux supports a FPU a floating point unit This is a special chip or part of a chip in the case of a 80486DX CPU that performs arithmetic dealing with non whole numbers Some of these chips are bad and when Linux tries to identify these chips the machine crashes The machine stops functioning If this happens you ll see Checking 386 387 coupling Otherwise you ll see Checking 386 387 coupling Ok fpu using exception 16 error reporting if you re using a 486DX If you are using a 386 with a 387 you ll see Checking 386 387 coupling Ok fpu using irql3 error reporting It now runs another test on the halt instruction Checking nlt instruction Ok After that initial configuration Linux prints a line identifying itself It says what version it is what version of the GNU C Compiler compiled it and when it was compiled Linux version 1 3 55 root mousehouse gcc version 2 7 0 1 Sun Jan 7 14 56 26 EST 199 The serial driver has started to ask questions about the hardware A driver is a part of the kernel that controls a device usually a peripheral It is responsible for the details of how the CPU communicates with the device This allows people who write user applications to concentrate on the application they don t have to worry about exactly how the computer works 10 11 12 13 Serial
199. st 5 lines 5s amp amp g Double the number of spaces between the words Using the complete match string has its limits hence vi uses the escaped parentheses and to select the range of the substitution Using an escaped digit which identifies the range in the order of the definition the replacement can be build sf Vet LENA ig Delete everything after and including the colon ESZ NATAN ENGANA N2179 Swap the words either side of the colon You will most likely read the last series of gems again vi offers powerfull commands that many more modern editors do not or can not offer The cost for this power is also the main argument against vi The commands can be difficult to learn and read Though most good things can be a little awkward at first With a little practice and time the vi command set will become second nature Appendix B The GNU General Public License GNU GENERAL PUBLIC LICENSE Version 2 June 1991 Copyright 1989 1991 Free Software Foundation Inc 675 Mass Ave Cambridge MA 02139 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed Preamble The licenses for most software are designed to take away your freedom to share and change it By contrast the GNU General Public License is intended to guarantee your freedom to share and change free software to make sure the software is free for all its users This General Public License applies
200. stem you might want to turn the computer off when you re done with it To do so you ll have to log into a special account called root The root account is the system adminstrator s account and can access any file on the system If you re going to turn the computer off get the password from the system adminstrator In a single user system that s you Make sure you know the root password Login as root mousehouse login root Password Linux version 1 3 55 root mousehouse 1 Sun Jan 7 14 56 26 EST 1996 shutdown now Why end of the day URGENT message from the sysadmin System going down NOW end of the day Now you can turn off the power The command shutdown now prepares the system to be reset or turned off Wait for a message saying it is safe to and then reset or turn off the system When the system asks you Why it is merely asking for a reason to tell other users Since no one is using the system when you shut it down you can tell it anything you want or nothing at all A quick message to the lazy an alternative to the logout login approach is to use the command su As a normal user from your prompt type su and press return It should prompt you for the root password and then give you root privileges Now you can shut down the system with the shutdown now command 4To avoid possibly weakening some hardware components only turn off the computer when you re done for the day Turning the com
201. stems is the message of the day telling users to clean up their files System V 2 administrator s guide 4 1 Unix Commands When you first log into a Unix system you are presented with something that looks like the following home larry That something is called a prompt As its name would suggest it is prompting you to enter a command Every Unix command is a sequence of letters numbers and characters There are no spaces however Some valid Unix commands are mail cat and CMU_is_Number 5 Some characters aren t allowed we ll go into that later Unix is also case sensitive This means that cat and Cat are different commands Case sensitivity is a very personal thing Some operating systems such as OS 2 or Windows NT are case preserving but not case sensitive In practice Unix rarely uses the different cases It is unusual to have a situation where cat and Cat are different commands 27 The prompt is displayed by a special program called the shell Shells accept com mands and run those commands They can also be programmed in their own language and programs written in that language are called shell scripts There are two major types of shells in Unix Bourne shells and C shells Bourne shells are named after their inventor Steven Bourne Steven Bourne wrote the original Unix shell sh and most shells since then end in the letters sh to indicate they are extentions on the original idea There are many i
202. swd home larry ls F passwd home larry cp passwd frog home larry ls F frog passwd home larry The first cp command I ran took the file etc passwd which contains the names of all the users on the Unix system and their encrypted passwords and copied it to my home directory cp doesn t delete the source file so I didn t do anything that could harm the system So two copies of etc passwd exist on my system now both named passwd but one is in the directory etc and one is in home larry Then I created a third copy of etc passwd when Ityped cp passwd frog the three copies are now etc passwd home larry passwdand home larry frog The contents of these three files are the same even if the names aren t cp can copy files between directories if the first parameter is a file and the second parameter is a directory In this case the short name of the file stays the same It can copy a file and change it s name if both parameters are file names Here is one danger of cp If I typed cp etc passwd etc group cp would normally create a new file with the contents identical to passwd and name it group However if etc group already existed cp would destroy the old file without giving you a chance to save it It won t even print out a message reminding you that you re destroying a file by copying over it Let s look at another example of cp home larry ls F home larry mkdir passwd_version home l
203. system Neither USL nor the University of California Berkeley were involved in writing Linux One of the more interesting facts about Linux is that development occurs simulataneously around the world People from Austrialia to Finland contributed to Linuxand will hopefully continue to do so Linux began with a project to explore the 386 chip One of Linus s earlier projects was a program that would switch between printing AAAA and BBBB This later evolved to Linux Linux has been copyrighted under the terms of the GNU General Public License GPL This is a license written by the Free Software Foundation FSF that is designed to prevent people from restricting the distribution of software In brief it says that although you can charge as much as you d like for a copy you can t prevent the person you sold it to Assembly language is a very basic computer language that is tied to a particular type of computer It is usually considered a challenge to program in 2It was recently sold to Novell Previously USL was owned by AT amp T 3A cryptic way of saying system five release four from giving it away for free It also means that the source code must also be available This is useful for programmers Anybody can modify Linux and even distributed his her modifications provided that they keep the code under the same copyright Linux supports most of popular Unix software including the X Window System The X Window System w
204. system has been almost fully utilized but nowhere near overtaxed High load averages are the result of several programs being run simultaneously Amazingly upt ime is one of the few Unix programs that have no options who who displays the current users of the system and when they logged in If given the parameters am i asin who am i it displays the current user w f username The w program displays the current users of the system and what they re doing It basically combines the functionality of upt ime and who The header of w is exactly the same as upt ime and each line shows a user when the logged on and how long they ve been idle JCPU is the total amount of CPU time used by that user while PCPU the the total amount of CPU time used by their present task If w is given the option f it shows the remote system they logged in from if any The optional parameter restricts w to showing only the named user 7 4 What s in the File There are two major commands used in Unix for listing files cat and more I ve talked about both of them in Chapter 6 cat nA filel file2 fileN cat is not a user friendly command it doesn t wait for you to read the file and is mostly used in conjuction with pipes However cat does have some useful command line options For instance n will number all the lines in the file and A will show control characters as normal characters instead of possibly doing strange
205. t and you ll learn to love it Instead of just letting the text scroll away man stops at the end of each page waiting for you to decide what to do now If you just want to go on press and you ll advance a page If you want to exit quit the manual page you are reading just press a You 1l be back at the shell prompt and it 11 be waiting for you to enter a new command There s also a keyword function in man For example say you re interested in any commands that deal with Postscript the printer control language from Adobe Type man k psorman k Postscript you ll get a listing of all commands system calls and other documented parts of Unix that have the word ps or Postscript in their name or short description This can be very useful when you re looking for a tool to do something but you don t know it s name or if it even exists 4man will also display information on a system call a subroutine a file format and more In the original version of Unix it showed the exact same information the printed documentation would For now you re probably only interested in getting help on commands 4 3 Storing Information Filters are very useful once you are an experienced user but they have one small problem How do you store the information Surely you aren t expected to type everything in each time you are going to use the program Of course not Unix provides files and directories A directory is like a fo
206. t dev null home larry The first thing you might notice about those commands is the trailing amp at the end of the first two Putting an amp after a command tells the shell to start in running in the background right from the very beginning It s just a way to avoid having to start the program type and then type bg So we started those two commands running in the background The third is suspended and inactive at the moment You may notice that the machine has become slower now as the two running ones require some amount of CPU time Each one told you it s job number The first two also showed you their process identifi cation numbers or PID s immediately following the job number The PID s are normally not something you need to know but occasionally come in handy Let s kill the second one since I think it s making your machine slow You could just type kill 2 but that would be too easy Instead do this nome larry fg 2 yes sort gt dev null type ctrl c to kill it home larry As this demonstrates fg takes parameters beginning with as well In fact you could just have typed this home larry 2 yes sort gt dev null type ctrl c to kill it home larry This works because the shell automatically interprets a job number as a request to put that job in the foreground It can tell job numbers from other numbers by the preceding Now type jobs to see which jobs are left running
207. t it has been saved in the same way as if you had used M w You can yank it back out with C y as always The place Emacs saves all this text is known as the kill ring Some editors call it the clipboard or the paste buffer There s another way to do cutting and pasting whenever you use C k to kill to the end of a line the killed text is saved in the kill ring If you kill more than one line in a row they are all saved in the kill ring together so that the next yank will paste in all the lines at once Because of this feature it is often faster to use repeated C k s to kill some text than it is to explicitly set mark and point and use C w However either way will work It s really a matter of personal preference how you do it 5On some terminals C SPC doesn t work For these machines you must use C Q 8 7 Searching and Replacing There are several ways to search for text in Emacs Many of them are rather complex and not worth going into here The easiest and most entertaining way is to use isearch Isearch stands for incremental search Suppose you want to search for the string gad fly in the following buffer I was growing afraid that we would run out of gasoline when my passenger exclaimed Gadzooks There s a gadfly in heret You would move to the beginning of the buffer or at least to some point that you know is before the first occurence of the goal word gadfly and type C
208. t should be saved and exit Emacs with C x C c Sometimes C x C c will ask you a question or two in the minibuffer before it lets you leave don t be alarmed just answer them in the obvious ways If you think that you might be returning to Emacs later don t use C x C c at all use C z which will suspend Emacs You can return to it with the 3If you are not the root user on the machine you shouldn t be able to hurt the system anyway but be careful just the same shell command fg later This is more efficient than stopping and starting Emacs multiple times especially if you have edit the same files again later Under X hitting C z will merely iconize the window See the section on iconization in Chapter 5 This gives you two ways of iconizing Emacs the normal way your window manager offers and C z Remember when you iconize a simply fg won t bring the window back you ll have to use your window manager 8 5 The Meta Key You ve already learned about one modifier key in Emacs the key There is a second one called the Meta key which is used almost as frequently However not all keyboards have their Meta key in the same place and some don t have one at all The first thing you need to do is find where your Meta key is located Chances are your keyboard s Alt keys are also Meta keys if you are using an IBM PC or other another keyboard that has an key The way to test this is to hold down a key that you t
209. t since Emacs has so many internal functions but it will display as much of it as fits on the screen when it s ready At that point hit C g to quit out of describe function There will be a buffer called Complet ions which contains the completion list you just generated Switch to that buffer Now you can use C s isearch to search for likely functions For exam ple it s a safe assumption that a function which prompts for a line number and then goes to that line will contain the string line in its name Therefore just start searching for the string line and you ll find what you re looking for eventually If you want another method you can use C h a command apropos to show all functions whose names match the given string The output of command apropos is a little harder to sort through than just searching a completion list in my opinion but you may find that you feel differently Try both methods and see what you think There is always the possibility that Emacs does not have any predefined function to do what you re looking for In this situation you have to write the function yourself I m not going to talk about how to do that you should look at the Emacs Lisp library for examples of function definitions and read the Info pages on Emacs Lisp If you happen to know a local Emacs guru ask her how to do it Defining your own Emacs functions is not a big deal to give you an idea I have written 131 o
210. t a selected line from the command line vi 10 myfile tex This command opens the file called myfile tex and places the cursor 10 lines down from the start of the file Try out some of the commands in this section Very few people can remember all of them in one session Most users use only a subset of the above commands You can move around so how do you change the text A 4 2 Modifing Text The aim is to change the contents of the file and vi offers a very large set of commands to help in this process This section will focus on adding text changing the existing text and deleting the text At the end of this section you will have the knowledge to create any text file desired The remaining sections focus on more desireable and convenient commands When entering text multiple lines can be entered by using the key If a typing mistake needs to be corrected and you are on the entering text on the line in question You can use the key to move the cursor over the text The different implemen tations of vi behave differently Some just move the cursor back and the text can still be viewed and accepted Others will remove the text as you backspace Some clones even allow the arrow keys to be used to move the cursor when in input mode This is not nor mal vi behaviour If the text is visable and you use the key when on the line you have backspaced on the text after the cursor will be cleared Use your editor to become accustomed to its b
211. t finishes If this doesn t make sense as you read it then try it out 8 8 What s Really Going On Here Actually all these keybindings you have been learning are shortcuts to Emacs functions For example C p is a short way of telling Emacs to execute the internal function previous line However all these internal functions can be called by name using M x If you forgot that previous line is bound to C p you could just type M x previous lin Return and it would move you up one line Try this now to understand how M x previous line and C p are really the same thing The designer of Emacs started from the ground up first defining a whole lot of internal functions and then giving keybindings to the most commonly used ones Sometimes it s easier just to call a function explicitly with M x than to remember what key it s bound to The function query replace for example is bound to M in some versions of Emacs But who can remember such an odd keybinding Unless you use query replace extremely often it s easier just to call it with M x Most of the keys you type are letters meant to be inserted into the text of the buffer So each of those keys is bound to the function sel f insert command which does nothing but insert that letter into the buffer Combinations that use the key with a letter are generally bound to functions that do other things like moving you around For example C v is bound to a function called
212. t uses the Library must include any data and utility programs needed for reproducing the executable from it How ever as a special exception the source code distributed need not include anything that is normally distributed in either source or binary form with the major compo nents compiler kernel and so on of the operating system on which the executable runs unless that component itself accompanies the executable It may happen that this requirement contradicts the license restrictions of other pro prietary libraries that do not normally accompany the operating system Such a con tradiction means you cannot use both them and the Library together in an executable that you distribute 10 11 You may place library facilities that are a work based on the Library side by side in a single library together with other library facilities not covered by this License and distribute such a combined library provided that the separate distribution of the work based on the Library and of the other library facilities is otherwise permitted and provided that you do these two things a Accompany the combined library with a copy of the same work based on the Library uncombined with any other library facilities This must be distributed under the terms of the Sections above b Give prominent notice with the combined library of the fact that part of it is a work based on the Library and explaining where to find the accompanying uncombined
213. tart and end of the block In Emacs you do this by setting two locations in the buffer known as mark and point To set the mark go to the place you want your block to begin and type C SPC SPC means Space of course You should see the message Mark set appear in the minibuffer The mark has now been set at that place There will be no special highlighting indicating that fact but you know where you put it and that s all that matters What about point Well it turns out that you ve been setting point every time you move the cursor because point just refers to your current location in the buffer In formal terms point is the spot where text would be inserted if you were to type something By setting the mark and then moving to the end of the block of text you have actually defined a block of text This block is known as the region The region always means the area between mark and point Merely defining the region does not make it available for pasting You have to tell Emacs to copy it in order to be able to paste it To copy the region make sure that mark and point are set correctly and type M w It has now been recorded by Emacs In order to paste it somewhere else just go there and type C y This is known as yanking the text into the buffer If you want to actually move the text of the region to somewhere else type C w instead of M w This will kill the region all the text inside it will disappear In fac
214. tarted or The Linux System Adminstrator s Guide You should see after all the boot up procedures are done something like the following the first line is merely a greeting message it might be a disclaimer or anything else Welcome to the mousehouse Please have some chees mousehouse login However it s possible that what the system presents you with does not look like this Instead of a boring text mode screen it is graphical However it will still ask you to login and will function mostly the same way If this is the case on your system you are going to be using The X Window System This means that you will be presented with a windowing system Chapter 5 will discuss some of the differences that you ll be facing Logging in will be similar as will the basics to much of Unix If you are using X look for a giant X is the margin This is of course your invitation to login Throughout this manual we ll be using the fictional or not so fictional depending on your machine user Larry Whenever you see larry you should be substituting your own account name Account names are usually based on real names bigger more serious Unix systems will have accounts using the user s last name or some combination of first and last name or even some numbers Possible accounts for Larry Greenfield might be larry greenfie lgreenfi 1g19 mousehouse is by the way the name of the machine I m working on It is possible that
215. ted under the terms of a permission notice identical to this one Permission is granted to copy and distribute translations of this manual into another lan guage under the conditions for modified versions The GNU General Public License and The GNU Library General Public License may be included in a translation approved by the Free Software Foundation instead of in the original English At your option you may distribute verbatim and modified versions of this document under the terms of the GNU General Public License excepting the clearly marked sections held under seperate copyright Exceptions to these rules may be granted for various purposes Write to Larry Green field at the above address or email leg andrew cmu edu and ask It is requested but not required that you notify the author whenever commercially or large scale printing this document Royalties and donations are accepted and will encourage further editions These are some of the typographical conventions used in this book Bold italics slanted Typewriter Key Used to mark new concepts WARNINGS and keywords in a language Used for emphasis in text Used to mark meta variables in the text especially in representations of the command line For example 1s 1 foo where foo would stand for a filename such as bin cp Used to represent screen interaction Also used for code examples whether it is C code a shell script or some
216. tely following it bin in this case Here is another example of the effect they have home larry echo HOME foo home larryfoo home larry Without the curly braces I would get nothing since there is no environment variables named HOMEfoo home larry echo SHOMEfoo home larry Let me clear one other thing up in that path the meaning of SPATH What that does is includes the value of any PATH variable previously set in my new PATH Where would the Remember that you can always execute programs in the current directory by being explicit about it i e EDO old variable be set The file et c profile serves as a kind of global bash_profile that is common to all users Having one centralized file like that makes it easier for the system administrator to add a new directory to everyone s PATH or something without them all having to do it individually If you include the old path in your new path you won t lose any directories that the system already setup for you You can also control what your prompt looks like This is done by setting the value of the environment variable PS1 Personally I want a prompt that shows me the path to the current working directory here s how I do it in my bashrc export PS1 SPWD As you can see there are actually two variables being used here The one being set is PS1 and it is being set to the value of PWD which can be thought of as either Print Working
217. terested in just one filesystem it is not necessary to descend other filesystems mounted under home 11 1 8 A last word Keep in mind that find is a very time consuming command as it has to access each and every inode of the system in order to perform its operation It is therefore wise to combine how many operations you need in a unique invocation of find especially in the housekeeping jobs usually ran via a crontab job A enlightening example is the following let s suppose that we want to delete files ending in BAK and change the protection of all directories to 771 and that of all files ending in sh to 755 And maybe we are mounting NES filesystems on a dial up link and we d like not to check for files there Why writing three different commands The most effective way to accomplish the task is this find fstype nfs prune o type d a exec chmod 771 o name BAK a exec bin rm Xp MN o name sh a exec chmod 755 It seems ugly and with much abuse of backslashes but looking closely at it reveals that the underlying logic is rather straightforward Remember that what is really performed is a true false evaluation the embedded command is just a side effect But this means that it is performed only if find must evaluate the exec part of the expression that is only if the left side of the subexpression evaluates to true So if for example the file considered at th
218. th is a little long some random stuff ulimit c unlimited export history_control ignoredups export PS1 SPWD gt umask 022 application specific paths export MANPATH usr local man usr man export INFOPATH usr local info export PGPPATH S HOME pgp make the main PATH homepath HOME bin stdpath bin usr bin usr local bin usr ucb etc usr etc usr games pubpath usr public bin usr gnusoft bin usr local contribs bin softpath usr bin X11 usr local bin X11 usr TeX bin export PATH homepath stdpath pubpath softpath Technically the curly braces were not necessary because the colons were valid delimiters nevertheless the curly braces are a good habit to get into and they can t hurt aliases alias ls l1s CF alias fgl fg 1 alias fg2 fg 2 alias tba talk sussman tern mcs anl gov alias tko talk kold cs oberlin edu alias tji talk jimb totoro bio indiana edu alias mroe more alias moer more alias email emacs f vm alias pu pushd alias po popd alias b b alias ds dirs alias ro rm rm alias rd rmdir alias 11 ls 1 alias la ls a alias rr rm r alias md mkdir alias ed2 emacs d floss 0 fg grey95 bg grey50 function gco gcc o 1 l c g 9 2 The X Window System Init Files Most people prefer to do their work inside a graphical environment and for Unix ma chines that us
219. the mail s headers which tell it where to send the mail from the actual contents of the message You can type whatever you want below the separator line When you are ready to send the message just type C c C c and Emacs will send it and then make the mail buffer go away 8 12 Being Even More Efficient Experienced Emacs users are fanatical about efficiency In fact they will often end up wasting a lot of time searching for ways to be more efficient While I don t want that to happen to you there are some easy things you can do to become a better Emacs user Sometimes experienced users make novices feel silly for not knowing all these tricks for some reason people become religious about using Emacs correctly Pd condemn that sort of elitism more if I weren t about to be guilty of it myself Here we go When you re moving around use the fastest means available You know that C f is forward char can you guess that M f is forward word C bisbackward char Guess what M b does That s not all though you can move forward a sentence at a time with M e as long as you write your sentences so that there are always two spaces follow ing the final period otherwise Emacs can t tell where one sentence ends and the next one begins M a is backward sentence If you find yourself using repeated C s to get to the end of the line be ashamed and make sure that you use C e instead and C a to go to the beginning of the line
220. the terms of this License c If the modified program normally reads commands interactively when run you must cause it when started running for such interactive use in the most ordinary way to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty or else saying that you provide a warranty and that users may redistribute the program under these conditions and telling the user how to view a copy of this License Exception if the Program itself is interactive but does not normally print such an announcement your work based on the Program is not required to print an announcement These requirements apply to the modified work as a whole If identifiable sections of that work are not derived from the Program and can be reasonably considered independent and separate works in themselves then this License and its terms do not apply to those sections when you distribute them as separate works But when you distribute the same sections as part of a whole which is a work based on the Program the distribution of the whole must be on the terms of this License whose permissions for other licensees extend to the entire whole and thus to each and every part regardless of who wrote it Thus it is not the intent of this section to claim rights or contest your rights to work written entirely by you rather the intent is to exercise the right to control the distribution of derivative or coll
221. them The reason for this is that your needs when writing a mail message are very different from your needs when say writing a pro gram Rather than try to come up with an editor that would meet every single need all the time which would be impossible the designer of Emacs chose to have Emacs behave differently depending on what you are doing in each individual buffer Thus buffers have modes each one designed for some specific activity The main features that distinguish one mode from another are the keybindings but there can be other differences as well 7To make matters worse there are Major Modes and Minor Modes but you don t need to know about that right now 8Richard Stallman also sometimes referred to as rms because that s his login name The most basic mode is fundamental mode which doesn t really have any special commands at all In fact here s what Emacs has to say about Fundamental Mode Fundamental Mode Major mode not specialized for anything in particular Other major modes are defined by comparison with this one I got that information like this I typed C x b which is switch to buffer and entered foo when it prompted me for a buffer name to switch to Since there was pre viously no buffer named foo Emacs created one and switched me to it It was in fundamental mode by default but it it hadn t been I could have typed M x fundamental mode to make it so Al
222. ther cause of this uneven interface is the fact that X applications are built using things called widget sets Included with the standard X distribution are Athena wid gets developed at MIT These are commonly used in free applications They have the disadvantage that they are not particularly good looking and are somewhat harder to use than other widgets The other popular widget set is called Motif Motif is a commercial widget set sim ilar to the user interface used in Microsoft Windows Many commercial applications use Motif widgets as well as some free applications The popular World Wide Web Browser netscape uses Motif Let s try to go through some of the more usually things you ll encounter 5 6 1 Buttons Buttons are generally the easiest thing to use A button is invoked by positioning the mouse cursor over it and clicking pressing and immediately releasing the mouse button the left button Athena and Motif buttons are functionally the same although they have cosmetic differences 5 6 2 Menu Bars A menu bar is a collection of commands accessible using the mouse For instance emacs s menu bar is shown in Figure 5 3 Each word is a category heading of commands File deals with commands that bring up new files and save files By convention this is also the category that contains the command to exit the program To access a command move the mouse cursor over a particular category such as File and press an
223. thing else and to display general files such as configuration files When necessary for clarity s sake these examples or figures will be en closed in thin boxes Represents a key to press You will often see it in this form Press return to continue A diamond in the margin like a black diamond on a ski hill marks dan ger or caution Read paragraphs marked this way carefully This X in the margin indicates special instructions for users of the X Window System This indicates a paragraph that contains special information that should be read carefully Acknowledgments The author would like to thank the following people for their invaluable help either with Linux itself or in writing The Linux Users Guide Linus Torvalds for providing something to write this manual about Karl Fogel has given me much help with writing my Linux documentation and wrote most of Chapter 8 and Chapter 9 I cannot give him enough credit Maurizio Codogno wrote much of Chapter 11 David Channon wrote the appendix on vi Appendix A Yggdrasil Computing Inc for their generous and voluntary support of this manual Red Hat Software for their more recent and still voluntary support The fortune program for supplying me with many of the wonderful quotes that start each chapter They cheer me up if no one else 111 Contents 1 Introduction 3 1 1 Who Should Read This Book e 3 1 1 1 What You
224. this License The Free Software Foundation may publish revised and or new versions of the Gen eral Public License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns Each version is given a distinguishing version number If the Program specifies a version number of this License which applies to it and any later version you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation If the Program does not specify a version number of this License you may choose any version ever published by the Free Software Foundation If you wish to incorporate parts of the Program into other free programs whose distri bution conditions are different write to the author to ask for permission For software which is copyrighted by the Free Software Foundation write to the Free Software Foundation we sometimes make exceptions for this Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally NO WARRANTY 11 12 BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE THERE IS NO WARRANTY FOR THE PROGRAM TO THE EXTENT PERMITTED BY AP PLICABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE PROGRAM AS IS
225. this autoloadable function can be called interactively that is by using M x This is very important in this case because one should be able to type M x run scheme to start a scheme process running under Emacs Now that run scheme has been defined as an autoloadable function what hap pens when I type M x run scheme Emacs looks at the function run scheme sees that it s set to be autoloaded and loads the file named by the autoload in this case cmuscheme The byte compiled file cnuscheme elc exists so Emacs will load that That file must define the function run scheme or there will be an autoload error Luckily it does define run scheme so everything goes smoothly and I get my preferred Scheme interface An autoload is a like a promise to Emacs that when the time comes it can find the specified function in the file you tell it to look in In return you get some control over what gets loaded Also autoloads help cut down on Emacs s size in memory by not loading certain features until they are asked for Many commands are not really defined as functions when Emacs starts up Rather they are simply set to autoload from a certain file If you never invoke the command it never gets loaded This space saving is actually vital to the functioning of Emacs if it loaded every available file in the Lisp library Emacs would take twenty minutes just to start up and once it was done it might occupy most of the
226. tribute the Library or a portion or derivative of it under Sec tion 2 in object code or executable form under the terms of Sections 1 and 2 above provided that you accompany it with the complete corresponding machine readable source code which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange If distribution of object code is made by offering access to copy from a designated place then offering equivalent access to copy the source code from the same place satisfies the requirement to distribute the source code even though third parties are not compelled to copy the source along with the object code 5 A program that contains no derivative of any portion of the Library but is designed to work with the Library by being compiled or linked with it is called a work that uses the Library Such a work in isolation is not a derivative work of the Library and therefore falls outside the scope of this License However linking a work that uses the Library with the Library creates an exe cutable that is a derivative of the Library because it contains portions of the Library rather than a work that uses the library The executable is therefore covered by this License Section 6 states terms for distribution of such executables When a work that uses the Library uses material from a header file that is part of the Library the object code for the work may b
227. ts another program The kernel becomes a manager and a provider not an active program So to see what the computer is doing after the kernel boots up we ll have to exam ine init init goes through a complicated startup sequence that isn t the same for all computers Linux has many different versions of init and each does things its own way It also matters whether your computer is on a network and what distribution you used to install Linux Some things that might happen once init is started e The file systems might be checked What is a file system A file system is the layout of files on the hard disk It let s Linux know which parts of the disk are already used and which aren t It s like an index to a rather large filing system or a card catalog to a library Unfortunately due to various factors such as power losses what the file system information thinks is going on in the rest of the disk and the actually layout of the rest of the disk are occasionally in conflict A special program called fsck can find these situations and hopefully correct them e Special routing programs for networks are run These programs tell your computer how it s suppose to contact other computers Temporary files left by some programs may be deleted e The system clock can be correctly updated This is trickier then one might think since Unix by default wants the time in UCT Universal Coordinated Time also known as Greenwich Mean Time
228. ts location in the program This implies that Emacs knows something about C syntax which it does although nothing about semantics it cannot insure that your program has no errors In order to do this it assumes that the previous lines are indented correctly That means that if the preceding line is missing a parenthesis semicolon curly brace or whatever Emacs will indent the current line in a funny way When you see it do that you will know to look for a punctuation mistake on the line above You can use this feature to check that you have punctuated your programs correctly instead of reading through the entire program looking for problems just start indenting lines from the top down with Tab and when something indents oddly check the lines just before it In other words let Emacs do the work for you 8 11 2 Scheme Mode This is a major mode that won t do you any good unless you have a compiler or an inter preter for the Scheme programming language on your system Having one is not as normal as having say a C compiler but it s becoming more and more common so I ll cover it too Much of what is true for Scheme mode is true for Lisp mode as well if you prefer to write in Lisp Well to make matters painful Emacs comes with two different Scheme modes be cause people couldn t decide how they wanted it to work The one I m describing is called cmuscheme and later on in the section on customizing Emacs Pl talk about h
229. u must make sure that you didn t tell it to take a long time doing whatever you wanted it to do Ask for assistance if you didn t know what the command did Some messages will alert you of bugs Some messages are not bugs Check Section 3 4 and any other documentation to make sure they aren t normal informational messages For instance messages like disk full or Ip0 on fire aren t software problems but something wrong with your hardware not enough disk space or a bad printer If you can t find anything about a program it is a bug in the documentation and you should contact the author of that program and offer to write it yourself If something is incorrect in existing documentation it is a bug with that manual If something appears incomplete or unclear in the manual that is a bug If you can t beat gnuchess at chess it is a flaw with your chess algorithm but not necessarily a bug with your brain Especially this one 12 3 2 Reporting a Bug After you are sure you found a bug it is important to make sure that your information gets to the right place Try to find what program is causing the bug if you can t find it perhaps you could ask for help in comp os linux help or comp unix misc Once you find the program try to read the manual page to see who wrote it The preferred method of sending bug reports in the Linux world is via electronic mail If you don t have access to electronic mail you might
230. ually means using X If you re accustomed to the Macintosh or to Microsoft Windows the X Window System may take a little getting used to especially in how it is customized With the Macintosh or Microsoft Windows you customize the environment from within the environment if you want to change your background for example you do by clicking on the new color in some special graphical setup program In X system defaults are con trolled by text files which you edit directly in other words you d type the actual color name into a file in order to set your background to that color There is no denying that this method just isn t as slick as some commercial windowing systems I think this tendency to remain text based even in a graphical environment has to do with the fact that X was created by a bunch of programmers who simply weren t trying to write software that their grandparents could use This tendency may change in future versions of X at least I hope it will but for now you just have to learn to deal with more text files It does at least give you very flexible and precise control over your configuration Here are the most important files for configuring X xinitrc A script run by X when it starts up twmrc Read by an X window manager t wm vwmrc Read by an X window manager fvwm All of these files should be located in your home directory if they exist at all The xinitrc is a simple shell script that gets run w
231. uffer name as it can and so on Whenever you are being prompted for something in the minibuffer it s a good idea to see if Emacs is doing comple tion Taking advantage of completion whenever it s offered will save you a lot of typing Emacs usually does completion when you are choosing one item out of some predefined list Everything you learned about moving around and editing text in the first buffer applies to the new one Go ahead and change some text in the new buffer but don t save it i e don t type C x C s Let s assume that you want to discard your changes without saving them in the file The command for that is C x k which kills the buffer Type it now First you will be asked which buffer to kill but the default is the current buffer and that s almost always the one you want to kill so just hit Return Then you will be asked if you really want to kill the buffer Emacs always checks before killing a buffer that has unsaved changes in it Just type yes and hit Return 1f you want to kill it Go ahead and practice loading in files modifying them saving them and killing their buffers Make sure you don t modify any important system files in a way that will cause trouble of course but do try to have at least five buffers open at once so you can get the hang of switching between them 8 4 Ending an Editing Session When you are done with your work in Emacs make sure that all buffers are saved tha
232. umentation Project is also writing books for the more experienced users 1 4 1 Other Linux Books The other books include Installation and Getting Started a guide on how to aquire and install Linux The Linux System Adminstrator s Guide how to organize and maintain a Linux system and The Linux Kernel Hackers Guide a book about how to modify Linux The Linux Network Administration Guide talks about how to install configure and use a network connection 1 4 2 HOWTOs In additon to the books the Linux Documentation Project has made a series of short docu ments describing how to setup a particular aspect of Linux For instance the SCS I HOWTO describes some of the complications of using SCS I a standard way of talking to devices with Linux These HOWTOs are available in several forms in a bound book such as The Linux Bible or Dr Linux in the newsgroup comp os linux answers or on various sites on the World Wide Web A central site for Linux information is http www linux org 1 4 3 What s the Linux Documentation Project Like almost everything associated with Linux the Linux Documentation Project is a col lection of people working across the globe Originally organized by Lars Wirzenius the Project is now coordinated by Matt Welsh with help from Michael K Johnson It is hoped that the Linux Documentation Project will supply books that will meet all the needs of documenting Linux at some point in time Please tell us if
233. use the files modified to carry prominent notices stating that you changed the files and the date of any change c You must cause the whole of the work to be licensed at no charge to all third parties under the terms of this License d If a facility in the modified Library refers to a function or a table of data to be supplied by an application program that uses the facility other than as an argument passed when the facility is invoked then you must make a good faith effort to ensure that in the event an application does not supply such function or table the facility still operates and performs whatever part of its purpose remains meaningful For example a function in a library to compute square roots has a purpose that is entirely well defined independent of the application Therefore Subsection 2d requires that any application supplied function or table used by this function must be optional if the application does not supply it the square root function must still compute square roots These requirements apply to the modified work as a whole If identifiable sections of that work are not derived from the Library and can be reasonably considered independent and separate works in themselves then this License and its terms do not apply to those sections when you distribute them as separate works But when you distribute the same sections as part of a whole which is a work based on the Library the distribution of the whole must be
234. utility of such an option but a worker who programs from eight to five does appreciate it e depth processes each directory s contents before the directory itself To say the truth I don t know many uses of this apart for an emulation of rm F command of course you cannot delete a directory before all files in it are deleted too e follow deferences that is follows symbolic links It implies option noleaf see below e noleaf turns off an optimization which says A directory contains two fewer subdi rectories than their hard link count If the world were perfect all directories would be referenced by each of their subdirectories because of the option as inside itself and by it s real name from its parent directory That means that every directory must be referenced at least twice once by itself once by its parent and any additional references are by subdirectories In practice however symbolic links and distributed filesystems can disrupt this This option makes find run slightly slower but may give expected results e maxdepth levels mindepth levels where levels is a non negative integer respec tively say that at most or at least levels levels of directories should be searched A couple of examples is mandatory maxdepth 0 indicates that it the command should be performed just on the arguments in the command line i e without re cursively going down the directory tree mindepth 1 inhibit
235. ve to write something like foo rather than foo find usr includ xtype f xec grep foobar dev null is a grep executed recursively starting from directory usr include In this case we are interested both in regular file and in symbolic links which point to regular files hence the xtype test Many times it is simpler to avoid specyfing it especially if we are rather sure no binary file contains the wanted string And why the dev null in the command It s a trick to force grep to write the file name where a match has been found The command grep is applied to each file in a different invocation and so it doesn t think it is necessary to output the file name But now there are two files i e the current one and dev nul1 Another possibility should be to pipe the command to xargs and let it perform the grep I just tried it and completely smashed my filesystem together with these notes which I am tring to recover by hand find atime 1 fstyp xt2 name core exec rm is a classical job for crontab It deletes all file named core in filesystems of type ext2 which have not been accessed in the last 24 hours It is possible that someone wants to use the core file to perform a post mortem dump but nobody could remember what he was doing after 24 hours find hom xdev size 500k ls gt piggies is useful to see who has those files who clog the filesystem Note the use of xdev as we are in
236. will display instead of kilobytes 1024 characters the total in bytes One byte is the equivalent of one letter in a text document And the s flag will just display the directories mentioned on the command line and not their subdirectories af af is short for disk filling 1t summarizes the amount of disk space in use For each filesystem remember different filesystems are either on different drives or partitions it shows the total amount of disk space the amount used the amount available and the total capacity of the filesystem that s used One odd thing you might encounter is that it s possible for the capacity to go over 100 or the used plus the available not to equal the total This is because Unix reserves some space on each filesystem for root That way if a user accidentally fills the disk the system will still have a little room to keep on operating For most people df doesn t have any useful options uptime The upt ime program does exactly what one would suspect It prints the amount of time the system has been up the amount of time from the last Unix boot uptime also gives the current time and the load average The load average is the average number of jobs waiting to run in a certain time period uptime displays the load average for the last minute five minutes and ten minutes A load average near zero indicates the system has been relatively idle A load average near one indicates that the
237. wline terminated records to the size of cbs replacing newline with trailing spaces unblock which performs the opposite eliminates trailing spaces and replaces them with newline lcase and ucase to convert test to lowercase and uppercase swab which swaps every pair of input bytes for example to use a file containing short integers written on a 680x0 machine in an Intel based machine you need such a conversion noerror to continue processing after read errors sync which pads input block to the size of ibs with trailing NULs 11 3 2 Examples The canonical example is the one you have probably bumped at when you tried to create the first Linux diskette how to write to a floppy without a MS DOS filesystem The solution is simple dd if disk img of dev fd0 obs 18k count 80 I decided not to use ibs because I don t know which is the better block size for a hard disk but in this case no harm would have been if instead of obs I use bs it could even be a trifle quicker Notice the explicitation of the number of sectors to write 18KB is the occupation of a sector so count is set to 80 and the use of the low level name of the floppy device Another useful application of dd is related to the network backup Let s suppose that we are on machine alpha and that on machine beta there is the tape unit dev rst0 with a tar file we are interested in getting We have the same rights on both machines but there is no space on beta to dump
238. word the contents of the named buffer b Move the next 3 words to named buffer b Use the P command to paste the contents of the cut buffer to the edit buffer p Paste from the unnamed buffer to the RIG HT of the cursor P Paste from the unnamed buffer to the LEFT of the cursor nP Paste n copies of the unnamed buffer to ap Paste from the named buffer a RIGHT of t b3P Paste 3 copies from the named buffer b Ll When using vi within an xterm you have one more option for copying text Highlight the section of text you wish to copy by draging the mouse cursor over text Holding down the left mouse button and draging the mouse from the start to the finish will invert the text This automatically places the text into a buffer reserved by the X server To paste the text press the middle button Remmember the put vi into insert mode as the input could be interpreted as commands and the result will be unknown Using the same techinque a single word can be copied by double clicking the left mouse button over the word Just the single word will be copied Pasting is the same as above The buffer contents will only change when a new highlighted area is created Moving the text has three steps 1 Delete text to a named or unnamed buffer 2 Moving the cursor the to destination location 3 Pasting the named or unnamed buffer The process is the same as copying with the change on step one to delete When the command is performed the line is
239. xample home larry ed firstone txt a This is a new line of text If you check the file with cat you ll see that a new line was inserted between the original first and second lines How did ed know where to place the new line of text When ed reads in the file it keeps track of the current line The command a will add the text after the current line ed can also place the text before the current line with the key command i The effect will be the insertion of the text before the current line Now it is easy to see that ed operates on the text line by line All commands can be applied to a chosen line To add a line of text at the end of a file home larry ed firstone txt Sa The last line of text WwW q The command modifier tells ed to add the line after the last line To add the line after the first line the modifier would be 1 The power is now available to select the line to either add a line of text after the line number or insert a line before the line number How do we know what is on the current line The command key P will display the contents of the current line If you want to change the current line to line 2 and see the contents of that line then do the following home larry ed firstone txt 2p q A 2 3 Line numbers in detail You have seen how to display the contents of the current line by the use of the lP com mand We also know there are line number modifiers for the commands To print the
240. y obvious as some other operating systems Thus you will prob ably end up reading at least Chapters 4 5 and 6 The number one way to avoid using this book is to use the on line documentation that s available Learn how to use the man command it s described in Section 4 2 1 3 How to Read This Book The suggested way of learning Unix is to read a little then to play a little Keep playing until you re comfortable with the concepts and then start skipping around in the book You ll find a variety of topics are covered some of which you might find interesting and some of which you ll find boring After a while you should feel confident enough to start using commands without knowing exactly what they should do This is a good thing What most people regard as Unix is the Unix shell a special program that interprets commands It is the program that controls the obvious look and feel of Unix In practice this is a fine way of looking at things but you should be aware that Unix really consists of many more things or much less This book tells you about how to use the shell as well as some programs that Unix usually comes with and some programs Unix doesn t always come with but Linux usually does The current chapter is a meta chapter it discusses this book and how to apply this book to getting work done The other chapters contain Chapter 2 discusses where Unix and Linux came from and where they might be going It also
241. y processes doing nothing hnome larry kill 1 3 3 Terminated yes uniq gt dev null home larry jobs 1 Terminated yes gt dev null home larry You should see various messages about termination of jobs nothing dies quietly it seems Figure 6 1 on page 72 shows a quick summary of what you should know for job control 6 4 2 The Theory of Job Control It is important to understand that job control is done by the shell There is no program on the system called fg rather fg bg jobs and kill are all shell builtins actually sometimes ki11 is an independent program but the bash shell used by Linux has it built in This is a logical way to do it since each user wants their own job control space and each user already has their own shell it is easiest to just have the shell keep track of the user s jobs Therefore each user s job numbers are meaningful only to that user my job number 1 and your job number 1 are probably two totally different processes In fact if you are logged in more than once each of your shells will have unique job control data so you as a user might have two different jobs with the same number running in two different shells The way to tell for sure is to use the Process ID numbers PID s These are system wide each process has its own unique PID number Two different users can refer to a process by its PID and know that they are talking about the same process assuming that
242. ying bell sound and see the message Beginning of buffer appear in the minibuffer At this point you might wonder But what is a buffer When Emacs works on a file it doesn t actually work on the file itself Instead it copies the contents of the file into a special Emacs work area called a buffer where you can modify it to your heart s content When you are done working you tell Emacs to save the buffer in other words to write the buffer s contents into the corresponding file Until you do this the file remains unchanged and the buffer s contents exist only inside of Emacs With that in mind prepare to insert your first character into the buffer Until now everything we have done has been non destructive so this is a big moment You can choose any character you like but if you want to do this in style I suggest using a nice solid capital X As you type it take a look at the beginning of the mode line at the bottom of the screen When you change the buffer so that its contents are no longer the same as those of the file on disk Emacs displays two asterisks at the beginning of the mode line to let you know that the buffer has been modified 2In case you hadn t noticed yet many of Emacs s movement commands consist of combining Control with a single mnemonic letter Fmacs some_file txt Fundamental Top These two asterisks are displayed as soon as you modify the buffer and remai

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