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The Linux Users` Guide

1. know which alternative you are using 7 5 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 start 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 the
2. 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 el or elc extension indicating the name of the file to search for in the load 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 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 happens 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 cmuscheme 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
3. So we ve invented a new and not so efficent 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 Ctrl 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 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 listing and fox 5 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 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 comma
4. etc re 27 28 39 amp 39 LINUX kernel running messages 17 starting messages 15 account 13 AT amp T 7 8 background 38 bash 20 31 34 bg 36 38 BIOS 11 12 Bourne Steve R 19 Boyle Brian 3 BSD 7 8 cat 20 36 44 cd 24 cmp 47 Codogno Maurizio ili command line editing see shell editing cp 27 28 diff 47 directory creating 26 27 current 24 25 home 25 parent 25 present 24 root 22 working 24 DOS 5 12 14 16 110 end of file 21 error bad 386 387 coupling 17 fg 36 37 file 27 file system 22 filters 36 Fogel Karl iii foreground 37 fork 13 FPU 17 Free Software Foundation 4 8 20 General Electric 7 General Public License 8 9 getty 13 GNU Emacs 3 33 GNU Project 4 8 47 gnuchess 97 Gods Unix 27 Greenfield Larry account names for 13 grep 45 head 36 45 IEEE 8 init 12 13 input redirection 35 Intel 3 8 11 ispell 46 job control see shell job control jobs see shell jobs Johnson Michael K 5 Joy Bill 20 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 111 Kernighan Brian 7 kill 37 less 36 Library General Public License 9 LILO 12 login 11 18 ls 22 34 Lu H J 9 Macintosh 4 11 man 21 Massachusetts Institute of Technology 7 8 master boot record 12 MicroSoft Windows 9 mkdir 26 27 more 36 44 Motif 9 mount 17 MS DOS 11 19 command com 19 Mult
5. 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 self insert command which does nothing but insert that letter into the buffer Combinations that use the Control 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 scroll 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
6. ll just get a tab character and if you re lucky it ll turn out that you can use completion 7 8 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 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 buffer for example but can t remember what key sequence invokes it then use C h w for where is 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 Tab 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
7. If there isn t a floppy disk in the drive the BIOS looks for a master 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 in that distribution Another good reference is the LILO documentation 1 3 1 2 Linux Takes Over After the BIOS passes control to LILO LILO passes control to Linux This is under normal circumstances It is also possible for LILO to call DOS or some other PC operating system The first thing that LINUX does once it starts executing is changes to protected mode The 803862 CPU that controls your computer has two modes for our purposes called real mode and protected mode DOS runs in real mode as does the BIOS However for more advances operating systems it is necessary to run in protected mode Therefore when LINUX boots it discardes the BIOS 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 network 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
8. Key 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 danger or caution Read paragraphs marked this way carefully Acknowledgements 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 Chapter 7 and Chapter 8 Maurizio Codogno wrote much of Chapter 9 The fortune program for supplying me with many of the wonderful quotes that start each chap ter They cheer me up if no one else il ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Contents 1 Introduction 3 1 1 Who Should Read This Book 2 0 0 200200 200000002000 0 0 3 1 1 1 What You Should Have Done Before Reading This Book 2 3 1 2 How to Avoid Reading This Book 0 000 200 000000 4 1 3 How to Read This Book 2 2 0 00200 000000000002 ee ee 4 1 4 Linux Documentation 2 0 002000 0000000 2 5 1 4 1 Other Linux Books 0 00 200200000000 0000000008 5 1 4 2 What s the Linux Documentation Project aoaaa 5 1 5 Operating Systems 2 a 5 2 What s Unix anyway 7 2 1 Unix History 2 2 0200200002 7 2 2 Linux History 20 20
9. echo HOMEfoo prompt gt because there is no environment variable named HOMEfoo set The file etc 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 Therefore it might be best to put this in your bash_profile export PATH PATH HOME bin bin usr bin usr local bin usr bin X11 usr TeX bin so as not to lose any of the PATH directories defined in etc profile The reasons you didn t see me doing that in my own bash_profile before are not worth going into here 99 of the time you ll want the PATH defined in etc profile to be part of your own PATH so you d best be careful to include it 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 bash_profile export PS1i PWD gt Whew 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 Directory or Path to Working Directory But the evaluation of PWD takes place inside single quotes The single quotes serve to evaluate the expression
10. 00 00 2 8 2 2 1 Linux Now aooaa aaa a 9 2 2 2 Trivial Linux Matters a aaa a 9 2 2 3 Commercial Software in LINUX oaaae 9 3 Getting Started 11 3 1 Starting to Use Your Computer 0 0 11 3 1 1 Power tothe Computer 0 0 00 000000002 ee 11 3 1 2 Linux Takes Over 2 2 0 22 e 12 3 1 3 The User Acts 2 2 2 2 0 00200 00 000022 ee 13 3 2 Leaving the Computer 0 0 14 3 2 1 Turning the Computer Off 2 en 14 3 3 Kernel Messages 2 2 aaa 15 vi 4 5 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 3 3 1 Starting Messages oaoa a 15 3 3 2 Running Messages ooa 17 The Unix Shell 19 4 1 Unix Commands oa aaa a 19 4 1 1 A Typical Unix Command aaa 0 0 0 0 00000004 20 4 2 Helping Yourself aaa aaa a 21 4 3 Storing Information 0 0 000 2 22 4 3 1 Looking at Directories with ls 1 0 0 00 00 0 0 000000 22 4 3 2 The Current Directory and ecd 2 200200 0 0 0 00 000000 24 4 3 3 Using mkdir to Create Your Own Directories 2 0 02 0 0020 26 4 4 Moving Information 0 0 0 0 e 27 4 4 1 cpLikeaMonk 0 00000000000 000000008 27 4 4 2 Pruning Back with rm 2 ee 28 4 4 3 lt A Forklift Can Be Very Handy 0 29 Working with Unix 31 5 1 Wildcards 2 31 5 1 1 What Really Happens aoaaa aaa a 32 5 1 2 The Question Mark 0 20020 2000000000000 a 33 5 2 Time Saving with bash aaa aaa 33 5 2 1 Command L
11. 102 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 Pro gram 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 derivative works These actions are prohibited by law if you do not accept this License Therefore by modifying or distributing the Program or any work based on the Program you indicate your acceptance of this License to do so and all its terms and conditions for copying distributing or modifying the Progra
12. A better way of doing that task is to type home larry report ls F 1993 1 1994 1 datai data5 1993 2 data new data2 home larry report mkdir backup home larry report cp data backup home larry report ls F backup data new data1 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 5 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 datai data2 data5 backup before it gets run To illustrate this let me introduce anew 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 home larry cd report home larry report ls F 1993 1 1994 1 datai data5 1993 2 data new data2 home larry report echo 199 1993 1 1993 2 1994 1 home larry report echo 4 1994 1 home 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
13. CORRECT kkkkkkkk The command shutdown now prepares the system to be reset or turned off After it displays a message saying it is safe to do either You must go through this procedure however You risk losing work that you ve done if you don t 3 3 Kernel Messages The messages printed by the kernel vary from machine to machine and from kernel version to version The version of LINUX that is discussed in this section is 0 99 10 Please note that this is a big book and LINUX develops quickly Versions in other sections might be different Usually this distinction is unimportant 3 3 1 Starting Messages When LINUX first starts up it writes many messages to the screen which you might not be able to see LINUX maintains a special file called proc kmsg which stores all these messages for later viewing and I ve included a sample startup sequence here e 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 colour EGA 80x25 8 virtual consoles Serial driver version 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 evidentally learned the wrong version of English e Linux has
14. Here s one quick and dirty way to do it since Emacs gives completion on function names just type C h f which is describe function remember and then hit Tab 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 list 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 Completions 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 example 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 eventu ally 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 62 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 a
15. In X Windows system defaults are controlled 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 Windows 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 Windows 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 Windows xinitre A script run by X Windows when it starts up twmre Read by an X Windows window manager twm fvwmrc Read by an X Windows window manager fvwm All of these files should be located in your home directory if they exist at all The xinitre is a simple shell script that gets run when X Windows 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 Windows programs and setting window system parameters The last command in the xinitrc is usually the name of a window manager to run for example usr bin X11 twm short for the Twm Window Manager
16. 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 There is absolutely no need to be this fancy with the PATH it s just for showboating aliases alias ls 1s 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 1s 1 alias la 1s a alias rr rm r alias md mkdir alias ed2 emacs d floss 0 fg grey95 bg grey50 function gco gcc o 1 1 c g 75 76 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 8 2 X Windows Init Files Most people prefer to do their work inside a graphical environment and for Unix machines that usually means using X Windows 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 a Mac or MS 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
17. Traditionally Bourne shells have been used for compatibility and C shells have been used for interactive use LINUX comes with a Bourne shell called bash written by the Free Software Foundation bash stands for Bourne Again Shell one of the many bad puns in Unix It is an advanced Bourne shell with many features commonly found in C shells and is the default When you first login the prompt is displayed by bash and you are running your first Unix program the bash shell 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 named 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 y uu uucat 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 For all you hopefuls no it is not a game cat is a useful utility
18. 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 very beneficial Thus the best way to learn Unix and LINUX is by using them Use them for everything you can Experiment Don t be afraid it s always possible to mess things up but you can always reinstall For better or for worse though Unix isn t as intuitively obvious as some other operating systems Thus you will probably end up reading at least the first couple of chapters in this book 1 3 How to Read This Book The suggested way of learning Unix is to read a little then to play a little I suggest the first X chapters after them the rest of the book can be read in almost any order 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 After a while you should feel confident enough to start using commands without knowing 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 In practice this is a fine way of looking at things but you should be aware that Unix really consists of many mor
19. asking you these questions it is asking the hardware The part of LINUX asking these questions is the kernel During boot up the LINUX kernel will print variations on several messages You can read about the messages in Section 3 3 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 that font are usually the names of programs files directories or other computer related items After the kernel starts init it never starts another program The kernel becomes a manager and a provider not a active program So to see what the computer is doing after the kernel boots up we ll have to examine init init goes through a complicated startup sequence that isn t the same for all computers For LINUX there are many versions of init and each does things its own way It also matters whether your computer is on a network or 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 you might ask A file system is the layout of files on the hard disk It let s Unix know which parts of the disk are already used and which aren t 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 actua
20. 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 Return 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 This leads to one of the more Zen like quotes in Emacs lore in which an unimpressed user asks an Emacs fanatic Who cares Why would I ever want to have two hundred buffers open simultaneously To which the fanatic replies But isn t it nice to know that you can 52 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Notice that you get the same sort of completion you got w
21. cbs bytes skip blocks seek blocks count blocks conv f ascii ebcdic ibm block unblock 1lcase ucase swab noerror notrunc sync so all 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 e if filein and of fileout instruct dd to respectively read from filein and write to fileout In the latter case the output file is truncated to the value given to seek or if the keyword is not present to 0 that is deleted before performing the operation But look below at option notrunc e 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 resul
22. configure and use a network connection 1 4 2 What s the Linux Documentation Project Like almost everything associated with Linux the Linux Documentation Project is a collection 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 we ve suceeded or what we should improve on 1 5 Operating Systems An operating system s primary purpose is to support programs that actually do the work An operating system is not the tool that does the work it s the tool that supports the work It s tempting to just want to modify the operating system for its own sake and if you feel this way often I suggest you find a copy of The LINUX Kernel Hackers Guide Operating systems OS for short 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 then early operating systems it doesn t try to do everything like some other operating systems The original design philosophy for Unix was to distribute functionality into small parts the programs That way you can relatively easily achieve new functionality and new features by com bining the small parts programs in new ways And i
23. do anything that requires writing to the screen Under LINUX TERM s value is sometimes console which means I believe a vt100 like terminal with some extra features Larry or someone please correct if that is not accurate Often simple terminal problems like garbage characters can be fixed by issuing this command prompt gt export TERM vt100 There is another variable named simply PATH whose value is crucial to the proper functioning of the shell Here s mine prompt gt echo PATH home kfogel bin bin usr bin usr local bin usr bin X11 usr TeX bin prompt gt Your PATH is a colon separated list of the directories the shell should search for programs 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 kfogel bin a directory I made for storing programs 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 it in home kfogel bin Bash looks next in bin 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 72 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION prompt gt usr bin 1s The PATH variable exists so that we don t have to type in
24. 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 re toad where frog and re exist and toad isn t a directory Try it and see One last thing in this section how can you show the parameters that cp takes After all the parameters can mean two different things When that happens we ll have two different lines cp source destination name cp filel file2 fileN destination directory 4 4 2 Pruning Back with rm 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION rm filel file2 fileN For example home larry 1s F frog re re_version home larry rm frog toad rc rm toad No such file or directory home larry 1s F rc_version home larry 29 As you can see rm is extremely unfriendly Not only does it not ask you for confirmation but it will also delete things even if the whole command line wasn t correct This could actually be dangerous Consider the differ
25. if any to sign a copyright disclaimer for the program if necessary Here is a sample alter the names ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 105 Yoyodyne Inc hereby disclaims all copyright interest in the program Gnomovision 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 proprietary pro grams 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 106 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Appendix B The GNU Library General Public License 107 108 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 ATpX A Document Preparation System Reading Massachusetts Addison Wesley Publishing Company 1986 4 Stallman Richard M GNU Emacs Manual eight edition Cambridge Massachusetts Free Soft ware Foundation 1993 109 Index bash_profile 67 etc issue 13 etc motd 14
26. in case anyone ever asks you What sort of thing might you want to put in a xinitre 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 Windows for example xclock Here is some of my xinitrc yours will almost certainly look different so this is meant only as 6 The server just means the main X Windows 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 77 an example bin sh The first line tells the operating system which shell to use in interpreting this script The script itself ought to be marked as executable you can make it so with chmod x xinitrce 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 your system I don t even guarantee that they mean anything on mine xmodmap e clear Lock xmodmap e keyco
27. inside them which itself evaluates the variable PWD If you just did export PS1 PWD 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 There s a lot more to configuring your bash_profile and not enough room to explain it here You can read the Bash man page for more and also the Info pages on it if you have them installed and ask questions of experienced Bash users Here is a complete bash_profile for you to study it s 74 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION fairly standard and probably can t get you into any trouble but don t be intimidated if you don t ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION understand everything in it some random stuff ulimit c unlimited export history_control ignoredups export PS1 PWD gt umask 022 application specific paths export MANPATH usr local man usr man export INFOPATH usr local info export PGPPATH 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
28. invoke Emacs on the file prompt gt emacs some_file txt 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 If you invoke it from X Windows 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 You should see the contents of the file filling most of the screen or as much of the file as fits on the screen if it s a lot of text Then one line from the bottom of the screen appears in reverse video This line is called the mode line in Emacs It should say something like Emacs some_file txt Fundamental Top The word Top might be All instead and there might be other minor differences The one blank line in regular video 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 49 50 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION input from you when necessary Ignore 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 sh
29. 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 kfogel floss life uiuc edu ls Insert a listing of my directory on floss here This will work if user kfogel 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 kfogel s rhosts file on floss Note that 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 in a 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 rhosts file is readable by you and no one else ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 83 8 3 4 Mail Forwarding You can also have a forward file which is not strictly speaking an init file If it c
30. man page if you need more help While there are versions of this for several other European languages the copy on your LINUX machine is most likely for American English and only American English Sorry ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION AT 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 file 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 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 I also like the lion it s really neat home larry cp frog toad home larry diff frog toad home larry cat dog Animals are very nteresting creatures One of my favorite animals is the tiger a fearsome beast with large teeth I also like the lion it
31. 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 contributions 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 103 10 This section is intended to make thoroughly clear what is believed to be a consequence 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 this License The Free Software Foundation may publish revised and or new versions of the General Public License from time to time Such new versions will be similar in spirit to the present version but may differ in d
32. now switched to protected mode and 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 t 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 16 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Serial driver version 3 95 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 8 serial ports A serial port is the equivalent of DOS COM ports and is a device normally used with modems and mice Actually when the serial driver first starts up it only finds out how many ports there are the other information are defaults What it is trying to say is that serial port 0 COM1 has an electronic 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 The differences are beyond the scope of this book 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 1p sta
33. on Emacs 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 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 7 13 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 online help facilities cannot be emphasized 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 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
34. on them A partition is a logical seperation on a drive that is used to keep operating systems from interfering with each other In this example the computer had one hard disk hda with four partitions Partition check hda hda1 hda2 hda3 hda4 e Finally LINUX mounts the root partition The root partition is the disk partition where the LINUX operating system lives When LINUX mounts this partition it is making the partition available for use by the user VFS Mounted root ext filesystem 3 3 2 Running Messages The Linux kernel occasionally sends messages to your screen The following is a list of some of these messages and what they mean Frequently these messages indicate something is wrong Some of these messages are critical which means the operating system and all your programs stops working When these messages occur you should write them down and what you where doing at the time and send them to Linus You should see Section 10 2 2 Luckily some of these messages are merely informational hopefully you ll see them more often 18 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Adding Swap 10556k swap space lp0 on fire kkkk OBVIOUSLY INCOMPLETE Chapter 4 The Unix Shell 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 4 1 Unix Commands When you first log into a Unix syst
35. options known by GNU version of find Remember that they always return true ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 87 e daystart measures elapsed time not from 24 hours ago but from last midnight A true hacker probably won t understand the 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 form 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 subdirectories than their hard link count If the world were perfect all directories would be referenced with their name on the father directory as on itself thus the value two above possible exceptions a non UNIX NFS mounted filesystem and symbolic links Life is hard sometimes e maxdepth levels mindepth levels where levels is a non negative integer respectively say that at most or at least levels levels of directories should be searched A couple of exam ples is mandatory maxdepth 0 indicates that it the command should be performed just on the arguments in the command line i e without recursively going down the directory tree mindepth 1 inhi
36. permissions tell Unix whether or not the file can be read from written to or executed as a program du df 6 3 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 5 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 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 file1 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 Ctrl L as a new page character more will start on a specified linenumber Since more is an interactive command I ve summarized the major interactive commands below Spacebar Moves to the next screen of text ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 45 a This will scroll the screen by 11 lines or abo
37. s really neat home larry diff frog dog 1c1 2 lt Animals are very interesting creatures One of my favorite animals 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 1 1 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 compare different line numbers it is much more efficent then listing out every single line if there is an extra return early in one file 48 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Chapter 7 Editing files with Emacs FUNNY SOMETHING OR OTHER 7 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 one of the most popular editors around partly because it s very easy for a complete beginner to get actual work done with it To learn it 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
38. spelling of your file you can start it and scan a much smaller list of files 5 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 do is 1s usr bin some of the files scroll off the top of the screen How can we see all of the files 5 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 the user without using standard input or output but very rare all of the commands we have covered so far 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 r
39. you have access to a Unix system More importantly this Unix system should be an Intel PC running LINUX This requirement isn t necessary but when versions of Unix differ PII be doing what LINUX expects nothing else LINUX is available in many forms called distributions It is hoped that you ve found a complete distribution such as SoftLanding Linux Systems or the MCC Interim release and have installed it There are differences between the various distributions of LINUX but for the most part they re small and unimportant Occasionally in this book you ll find places that seem a little off If you do it s probably because you re using a different distribution than I am The author is interested in all such cases 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 3 4 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION you aren t the superuser you should have obtained an account from the superuser Also you should have some time and patience Learning LINUX isn t easy most people find learning the Macintosh Operating System is easier However many people feel that LINUX is more powerful Also 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
40. you 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 3 and any other documentation to make sure they aren t normal informational messages For instance messages like disk full or lp0 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 1A discussion group in Usenet which talks about administring Unix computers ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 97 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 10 2 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 preferre
41. 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 prompt gt echo PGPPATH PGPPATH prompt gt 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 commands from a file like bash_profile it can be said to be interpreting the commands There are four variables defined automatically when you log in meaning that you don t have to set them in your bash_profile because they have already been set by the time Bash gets around to reading its init file HOME TERM SHELL and USER Let s check their values prompt gt echo HOME home kfogel prompt gt echo TERM vt100 prompt gt echo SHELL bin sh prompt gt echo USER kfogel ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 71 In order these values are the location of your home directory your terminal type the program that is running as your shell bin sh or maybe bin bash in Linux they are the same thing anyway and finally your username Of these the only one whose purpose should be a mystery to you is the TERM variable A brief history lesson is in order though it means a digression The operating system you see needs to k
42. 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 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 99 100 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 certain 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 redistribu
43. 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 maintanence late at night Does you directory structure look a little messy at 1 32am Let it stay a little mess never hurt 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 10 2 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 10 2 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
44. 2 in object code or executable form under the terms of Sections 1 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 corresponding 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 modifications to it For an executable work 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 com pilation 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
45. Being Even More Efficient aoaaa aa 59 7 12 Customizing Emacs aoaaa 60 7 13 Finding Out More 2 2 64 8 I Gotta Be Me 67 8 1 Shell Customization 2 67 8 1 1 Aliasing aoaaa a 68 8 1 2 Environment Variables o aaa a 69 8 2 X Windows Init Files aaa aaa 76 8 3 Other Init Files 2 80 8 3 1 The Emacs Init File 2 0 0 0 0 000 0000 0000000 80 8 3 2 FTP Defaults 0 0 0 0 00000000 2 le 81 vill 8 3 3 Allowing Easy Remote Access to Your Account 8 3 4 Mail Forwarding 8 4 Seeing Some Examples 9 Funny Commands 9 1 find the file searcher 9 1 1 Generalities 2 2 e 9 1 2 Expressions 2 0 0 20 00 0000 eee 9 1 3 Options 0 20000000202 914 Tests 0 0 0 2 00 0000000000000 00000 91 5 Actions 2 0 000 0000 000000000 9 1 6 Operators 0 2 0 020 000 0000004 9 1 7 Examples 0 0 202000 91 8 Alastword 0 0 0 0000 040 9 2 tar the tape archiver 9 2 1 Introduction 0 2 0 00 000 9 2 2 Main options 0 20 0 00 9 2 3 Modifiers 20 0 00 02 0040 924 Examples 0 0 2 02 000 9 3 dd the data duplicator 2 2 2 0 0 0 e 9 3 1 Options 9 3 2 Examples 9 4 sort the datasorter 02 020 00 9 4 1 Introduction 9 4 2 Options 9 4 3 Examples 10 Errors Mistakes Bugs and Other Unpleasantries 10 1 Avoiding Errors 2 aaa a 10 2 Not Yo
46. CE OF THE PROGRAM IS WITH YOU SHOULD THE PROGRAM PROVE DE FECTIVE YOU ASSUME THE COST OF ALL NECESSARY SERVICING REPAIR OR CORRECTION IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRIT ING WILL ANY COPYRIGHT HOLDER OR ANY OTHER PARTY WHO MAY MODIFY AND OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE BE LIABLE TO YOU FOR DAMAGES INCLUDING ANY GENERAL SPECIAL INCIDENTAL OR CON SEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES 104 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 public 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 copyright 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 prog
47. ND DIE ALPHA VERSION developed by software companies and derive from one of the two groupings Recently the versions of Unix that are actually used incorporate features from both of them USL is a company that was spun off from AT amp T and has taken over the maintenance of UNIX since it stopped being a research item Unix now is much more commericial than it once was and the licenses cost much more Please note the difference between Unix and UNIX When I say Unix Iam talking about Unix versions in generally whether or not USL is involved in them UNIX is the current version of Unix from USL The distinction is because UNIX is a trademark of Unix System Laboratories Current versions of UNIX for Intel PCs cost between 500 and 2000 2 2 LINUX History LINUX was written by Linus Torvalds and has been improved by countless numbers of people around the world It is a clone written entirely from scratch of the Unix operating system Neither USL nor the University of California Berkeley was involved in writing LINUX One of the more interesting facts about LINUX is that development simulataneously occurs around the world People from Austrialia to Finland contributed to LINUX and hopefully will continue to contribute 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 c
48. ST THIS AND DIE ALPHA VERSION 55 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 if you want to replace it Just hit y or n at each instance for Yes or No until it finishes If this doesn t make sense as you read it then try it out 7 7 What s Really Going On Here Actually all these keybindings you have been learning are shortcuts to Emacs functions For exam ple 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 line 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
49. The LINUX Users Guide Copyright 1993 1994 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 meant for the beginning Unix user although it may be useful for more experienced users for reference purposes ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 1 UNIX is a trademark of Unix System Labratories MS DOS and MicroSoft Windows are trademarks of MicroSoft Corporation OS 2 and Operating System 2 are trademarks of IBM LINUX is not a trademark and has no connection to UNIX or to Unix System Labratories Please bring all unacknowledged trademarks to the attention of the author Copyright 1993 Larry Greenfield 427 Harrison Avenue Highland Park NJ 08904 greenfie gauss rutgers edu The LINUX Users Guide may be reproduced and distributed in whole or in part subject to the following conditions 0 The copyright notice above and this permission notice must be preserved complete on all complete or partial copies 1 Any translation or derivative work of The LINUX Users Guide must be approved by the author in writing before distribution 2 If you distribute The LINUX Users Guide in part instructions for obtaining the complete version of The LINUX Users Guide must be included and a means for obtaining a complete version provided 3 Small portions may be reproduced as
50. Unix needs a user to identify him or herself by a process called logging in You see when you first turn on the computer several things happen Since this guide is geared towards Linux Pll tell you what happens during the LINUX boot up sequence Please note that 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 Sections 3 1 1 and 3 1 2 Some parts of Section 3 1 2 will pertain 3 1 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 normally For our purposes the BIOS can never be changed 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 1Discrimination Perhaps You decide 2 From here on in this book I shall be using the mascaline 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 11 12 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Non system disk or disk error Removing the disk and pressing a key will cause the boot process to continue
51. VERSION Figure 4 1 A typical abridged Unix directory tree bin dev ete home larry sam lib __ proc tmp usr X386 bin emacs ete g include t include lib local bin emacs ete lib man spool sre linux tmp 23 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 ls bin etc install mnt root user var dev home lib proc tmp usr vmlinux home larry In the above command ls the directory is a parameter The first word of the command is the command name and anything after it is a parameter Some commands have special parameters called options or switches To see this try home larry ls F bin etc install mnt root user var dev home lib proc tmp usr vmlinux home larry 24 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION The 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 s
52. ages for the command footnoteOr system call subroutine file format etc you spesify For example 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 al1 help version file DESCRIPTION This manual page documents the GNU version of cat There s about one full page of information about cat Try it Don t expect to understand it though It assumes quite some Unix knowledge When you ve read the page there s probably a little black block at the bottom of your screen reading more Line 1 or something similar This is the more prompt 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 Space and you ll advance a page If you want to exit quit the manual page you are reading just press fai ow ll be back at the shell prompt and it ll be waiting for you to enter a new command There s also a keyword function in man If you for example type man k signal you ll get a listing of all commands system calls and other documented parts of Unix that have the word signal in their 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
53. al to think of it as your environment and to direct customization efforts at it The commands in bash_profile are read by bash when it starts up and whatever it found there will be in effect for the rest of your login session Ex MS DOS users can think of 1 Also known variously as init files rc files for run contro or even dot files because the filenames often begin with so that the files aren t displayed in a normal 1s In fact due to some confusing Unix lossage there are times when bash will look for a bash_profile and times when it will look for a bashrc To avoid inconsistency just make bashrc always be an exact copy of bash_profile You can do this through repeated use of the cp command or you can make a link with the command ln bash_profile bashrc Larry am I leading them astray by doing this Having looked over the Bash man page I don t see any reason to initiate them into the mysteries of login vs interactive shells but I am not an expert in this area Tn fact if you were using the C Shell instead of Bash the init file would be cshre Sigh one of the cutest facts about this is that the two shells use slightly different command languages so that users who use both on different systems say are constantly tripping themselves up You needn t worry however the default shell in LINUXis bash and if you know enough to be changing your default shell to C She
54. allel port at Ox3bc IRQ 5 plipi using parallel port at 0x378 IRQ 7 plip2 using parallel port at 0x278 IRQ 2 8390 c v0 99 10 5 28 93 for 0 99 6 Donald Becker becker super org gt This may change in latter versions of this book ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 17 WD80x3 ethercard probe at 0x280 FF FF FF FF FF FF not found 0x7f8 3c503 probe at 0x280 not found 8390 ethercard probe at 0x280 failed HP LAN ethercard probe at 0x280 not found nothing there No ethernet device found dl0 D Link pocket adapter probe failed at 0x378 e The next message you normally won t see as the machine boots up 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 That is to say the machine stops functioning If this happens you ll see You have a bad 386 387 coupling Otherwise you ll see Math coprocessor using exception 16 error reporting if you re using a 486DX If you are using a 386 with a 387 you ll see Math coprocessor using irqi3 error reporting If you don t have any type of math coprocessor at all you ll see What will they see e The kernel also scans for any hard disks you might have If it finds any and it should it ll look at what partitions you have
55. ams 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 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 from 1s you could use 1s usr bin head 5 4 Multitasking 5 4 1 The Basics 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 back ground To find out how they work use the command yes at a prompt more 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 Its name less of course 5more also allows the command more etc rc ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 37 home lar
56. 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 newline 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 Icase 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 9 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 o
57. ance caches the disk This means it temporarily stores part of the permanent storage in RAM The idea of what LINUX thinks the disk should be and what the disk actually contains is syncronized 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 the key marked Enter or Return Until you hit enter nothing will happen and you can delete what you ve done and start over home larry logout Welcome to the mousehouse Please have some cheese mousehouse login Now another user can login 3 2 1 Turning the Computer Off If this is a single user system 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 15 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 default root password Login as root mousehouse login root Password Linux version 0 99p110 shutdown now kkkkkkkkkk GET THE SHUTDOWN MESSAGE
58. are no files that meet the wildcard specification Try echo rc fr og and see what happens The shell will pass the wildcard specification verbatim to the program ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 33 5 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 ete directory 5 2 Time Saving with bash 5 2 1 Command Line Editing Occasionally you ve typed a long command to bash and 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 C t flips two adjacent characters You ll be able to find most of the commands in the chapter on Emacs Chapter 7 5 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 home larry 1s F this is a long file home larry cp this is a long file shorter home lar
59. aults to the one with amp When an amp is added to the end of the command line it tells the command to run in the background automatically This job is then subject to all the usual methods of job control detailed here bg This is a shell builtin 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 41 with the One way to think of bg is that it s really just fg amp Parameters job number optional defaults to the one with kill This is a shell builtin 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 a Parameters job number preceded by or PID no necessary jobs This shell command just lists information about the jobs currently running or sus pending Sometimes it also tells you about ones that have just exited or been terminated ctrl c This is the generic interrupt character Usually if you type it while a program 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 5 4 2 What Is Really Going On Here It is important to understand that job control is done by the shell There is no program on the system called fg
60. bits 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 1 e changing filesystem It is very useful when you have to search for something in the root filesystem in many machines it is a rather small partition but a find would otherwise search the whole structure 9 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 system 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 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 nn and nn which means a value strictly less than nn This is rather silly in the case of UIDs but it will turn han
61. 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 groups 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 find 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 9 1 3 Options Here there is the list of all
62. ched ok command 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 9 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 meaningful for the shell too expr not expr change the truth value of expression that is if expr is true it becomes false The exclamation mark needn t be escaped because it is followed by a white space expr expr2 expr a expr2 expri and expr2 90 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 exprl or expr2 correspond to the logical OR operation expr is not evaluated if expr is true exprl expr2 is the list statement both erprf and expr2 are evaluated together with all side effects of course and the final value of the expression is that of ezpr2 9 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 e
63. 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 prompt gt 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 prompt gt echo PATH home kfogel bin bin usr bin usr local bin usr bin X11 usr TeX bin prompt gt 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 quite 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 p
64. created beifang bmp with the program bitmap Here I tell twm to use it as the default highlight pattern on windows title bars Pixmaps TitleHighlight home kfogel 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 1s808859 1 MenuF ont 6x13 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 xbiff xeyes oclock yoid 79 80 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION that some decent example twmrc files came with your X Windows Take a look in the directory usr 1ib X11 twm or usr X11 1ib X11 twm and 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 Windows just freezes when you run certain commands chances are that this is the cause Break out of X with Control H Alt H Backspace edit your twmrc and try again If you are using fvwm the directory usr lib X11 fvwm or usr X11 lib 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
65. d left out somewhere earlier in the line don t use Backspace or Delete 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 60 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 completion finish the job by hitting Tab or Space 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 ill 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 When something awful happens and Emacs seems to be behaving weirdly because you hit some keys by accident and don t know what they did the solution is not to go hitting more keys randomly Just use C g which quits out of whatever you re in and lets out a noise if your terminal is capable of that to inform you that something was interrupted Whatever you do don t pan
66. d method of sending bug reports in the LINUX world is via electronic mail If you don t have access to electronic mail you might want to contact whoever you got LINUX from eventually you re bound to encounter someone who either has electronic mail or sells LINUX com mercially 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 e A description of what you think is incorrect For instance I get 5 when I compute 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 lib 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 use greenfie when he logs in
67. d to another computer architechure because it was written only with the 80386 in mind Of course Torvalds isn t the only big name in LINUX s development The following people also deserve to be recognized 3 The instructions that people write as distinct from zeros and ones ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 9 H J Lu has maintained gcc and the LINUX C Library two items needed for programming Of course I must have missed people in the above list Sincere thanks and apologies go out to anyone not mentioned here there must be dozens if not hundreds of you 2 2 1 Linux Now Currently LINUX is not yet at version 1 0 but as of this writing is on version 0 99p10 That s from July 3rd 1993 However it is evolving fast and people expect version 1 0 before the nert ice age That s a real good sign and many people in the LINUX community are looking forward to it The items changing the fastest in LINUX right now are TCP IP support and bug fixes 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 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 p
68. de 176 Control_R xmodmap e add control Control_R xmodmap e clear Mod2 xmodmap e add Modi Alt_L Al1t_R xset is a program for setting some other parameters of the X server xset m 3 2 amp mouse parameters xset s 600 5 amp screen saver prefs xset s noblank amp ditto xset fp home kfogel x fonts for cxterm To find out more do xset help Tell the X server to superimpose fish cursor over fish mask and use the resulting pattern as my mouse cursor xsetroot cursor home lab kfogel x fish cursor home lab kfogel x fish mask amp a pleasing background pattern and color xsetroot bitmap home lab kfogel 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 amp Maybe you d like to know 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 running on any other host a host being a remote machine to display here but this is a security hole those clients might be run by someone else and watch y
69. 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 8 3 Other Init Files Some other initialization files of note are emacs Read by the Emacs text editor when it starts up netrc Gives default login names and passwords for ftp rhosts Makes your account remotely accessible forward For automatic mail forwarding 8 3 1 The Emacs Init File If you use emacs as your primary editor then the emacs file is quite important It is dealt with at length in Chapter 7 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 81 8 3 2 FTP Defaults Your netre file allows you to have certain ftp defaults set before you run ftp Here is a small sample netre machine floss life uiuc edu login kfogel password fishSticks machine darwin life uiuc edu login kfogel password fishSticks machine geta life uiuc edu login kfogel password fishSticks machine phylo life uiuc edu login kfogel password fishSticks machine ninja life uiuc edu login kfogel password fishSticks machine indy life uiuc edu login kfogel 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
70. directory it s its own parent The file chapter 1 would be the file called chapter 1 in the current directory Occasion ally 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 1s F archives bin emacs etc ka9q lib tc1 usr local ls F src cweb linux xmris usr local In this example I changed to the parent directory using cd and I listed the directory usr src from usr local using sre Note that if I was in home larry typing 1s F sre wouldn t do me any good One other shortcut for lazy users the directory is your home directory usr local ls F usr local You can see at a glance that there isn t anything in your home directory Actually will become more useful as we learn more about how to manipulate files 26 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 4 3 3 Using mkdir to Create Your Own Directories Creating your own directories is extremely simple under Unix and can be a useful organizational tool To create a new directory use the command mkdir Of course mkdir stands for make directory mkdir directory Let s do a small example to see how this works home larry ls F home larry mkdir report 1993 home larry ls F report 1993 home larry cd report 1993 home larry rep
71. dy with other tests Another useful option is type c which returns true if the file is of type e The mnemonics for the possible choices are the same found in 1s so we have b when the file is a block special c when the 88 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION file is character special d for directories p for named pipes 1 for symbolic 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 then the permission bits of the file must exactly match them A lead
72. e name foo won t return what you want and you should either write name foo or name foot 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 9 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 89 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 ls 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 something Th
73. e filesystem Note the use of xdev as we are interested in just one filesystem it is not necessary to descend other filesystems mounted under home ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 91 9 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 NFS 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 0 name BAK a exec bin rm 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
74. e jobs command home larry jobs 1 Stopped yes gt dev null 3 Stopped yes uniq 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 home larry bg 1 yes gt dev null amp home larry jobs 1 Running yes gt dev null 3 Stopped yes uniq gt dev null Notice that now it is running and the other job has moved back up in line and has the Well enough of that Kill them all so you can get your machine back home larry kill 1 home larry kill 3 You should see various messages about termination of jobs nothing dies quietly it seems To summarize what you should know about job control now ctrl z DOS equiv Hah DOS doesn t have real job control 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 Parameters none it s not really a command just a signal fg DOS equiv none whatsoever Maybe someday This is a shell builtin 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 job number optional def
75. e section about input and output redirection you know that this is sending the output of yes into the special file dev null dev null1 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 nul1 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 home larry yes gt dev null yes is running and if we type ctrl z right now we 11 suspend it and get the prompt back Imagine that I just did that 1 Stopped yes gt dev null home larry Hmm is there any way to get it to actually run in the background while still leaving us the prompt for interactive work Of course there is otherwise I wouldn t have asked 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 piping a steady stream of single letters out the back of the machine does take some work after all Other than that however
76. e things or much less Depending on how you look at it This book tells you about how to use the shell programs that Unix usually comes with and some programs Unix doesn t always come with 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 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 5 1 4 Linux Documentation This book The LINUX Users Guide is intended for the Unix beginner Luckily the Linux Docu mentation 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
77. ecially made for twm believe it or not The main thing people like to play with in their twmrc is window style colors T This 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION and such and making cool menus so here s an example twmrc 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 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
78. edirection and pipes 5 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 home larry 1s listing home larry ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 35 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 useless 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 newfile The output of the command cat listing is the file listing
79. eir 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 tesh 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 it untou
80. em you are presented with something that looks like the following home larry This 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 Thus valid Unix commands include mail cat and CMU_is_Number 5 Some characters aren t allowed that s covered 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 The prompt is displayed by a special program called the shell The MS DOS shell is called COMMAND COM and is very simple compared to most Unix shells Shells accept commands 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 There are many implementations of this shell and all those specific shell programs are called Bourne shells Another class of shells C shells originally imple 19 20 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION mented by Bill Joy are also common
81. ence between these two commands home larry 1s 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 1s F frog home larry As you can see the difference of one character made a world of difference in the 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 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 Thus it s a lot like using cp and rm together Let s take a look at what we can do home larry cp etc re home larry 1s F re home larry mv rc frog home larry 1s F frog home larry mkdir report home larry mv frog report home larry 1s F 30 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION report home larry ls F report frog 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 mv old name new name mv file file2 fileN new directory You should be very careful with mv it doesn t check to see if the file already exists and will remove any old file in its way For instance if I had a file named frog already in my directory re
82. er to deal with treeware 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 66 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Chapter 8 I Gotta Be Me If God had known we d need foresight she would have given it to us 8 1 Shell 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 The most important configuration files are the ones used by the shell Linux s default shell is bash and that s the shell this manual will cover The most important configuration file for ordinary users is bash_profile Each user has their own bash_profile it lives in your home directory and it is used to customize your shell The shell remember is the go between that allows you to communicate with the operating system itself so it s quite natur
83. etail 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 distribution 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 WAR RANTY FOR THE PROGRAM TO THE EXTENT PERMITTED BY APPLICABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE PROGRAM AS IS WITHOUT WARRANTY OF ANY KIND EITHER EXPRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE THE ENTIRE RISK AS TO THE QUALITY AND PERFOR MAN
84. f new utilities appear and they do you can integrate them into your old toolbox Unfortunately programs grow larger and more feature packed on Unix as well these days but some of the flexibility interoperability is there to stay When I write this document for example I m using these programs actively fvwm to manage my windows emacs to edit the text IAT X to format it xdvi to preview it dvips to prepare it for printing and 1 Apologies to DOS OS 2 and VMS users I ve used all three and each have their good points Was mostly determined by the type of hardware Unix was to run on By sheer accident the resulting operating system turned out to be very useful on other hardware 6 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION then lpr to print it If I got a new better dvi previewer tommorow I could use it instead of xdvi without changing the rest of my setup The key part of an operating system is called the kernel In many operating systems like Unix OS 2 or VMS 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 etc One school of thought says that kernels should be very small and not supply a lot of resources depending on programs to pick up the work This allows the kernel to be small and fast but may make programs bigger Kernels designed like this are called micro kernels Ano
85. ficient 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 b is backward 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 following 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 f 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 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 wor
86. following buffer I was growing afraid that we would run out of gasoline when my passenger exclaimed Gadzooks There s a gadfly in here 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 s That puts you in isearch mode Now start typing the word you are searching for gadfly But as soon as 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 Return 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 we
87. g Session When you are done with your work in Emacs make sure that all buffers are saved that 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 5 This is more efficient suspend Emacs You can return to it with the shell command fg later than stopping and starting Emacs multiple times especially if you have edit the same files again later 7 4 The Meta Key You ve already learned about one modifier key in Emacs the Control 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 Alt key You can tell if a buffer has unsaved changes by looking at the beginning of the mode line If you see two asterisks in a row right near the left edge of the mode line then the buffer has been modified since it was last saved Tf you are not the root user on the machine you shouldn t be able to hurt t
88. gov login fogel password doorm machine juju mcs anl gov login fogel password doorm machine sunsite unc edu login anonymous password kfogel 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 ftp 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 netrc file if you ftp to one of the machines listed in the file You can tell ftp to ignore your netre and not attempt auto login by invoking it with the n option ftp n You must make sure that your netre 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 netre file will actually refuse to work if the read permissions on the file are bad There s more to the netre file than what I ve said when you get a chance do man netre or man ftp 8 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 bu
89. h f At the prompt in the minibuffer enter 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 all the function names that begin with insert and insert file is one of them 12 By 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 65 So you complete the function name and read about how it works and then use M x insert file If you re wondering whether it s also bound to a key you type C h w insert file Return and 3 find out The more you know about Emacs 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 manual 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 easi
90. he system anyway but be careful just the same 5Tf you are running Emacs under a windowing system like X Windows then just iconify the window This is analogous to suspending it though not quite the same ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 53 The way to test this is to hold down a key that you think 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 Escape 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 Escape 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 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 Escape key I will simply write M x since I don t
91. hen finding a file hitting Tab completes as much of a buffer 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 completion 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 2 Just type yes and hit Return if 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 7 3 Ending an Editin
92. ic Emacs will not reward it 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 undo more and more until Emacs can no longer remember what changes were made 7 12 Customizing Emacs Emacs is so big and so complex that it actually has its own programming language Pm 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 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 li brary s location depends on how Emacs was installed on your system common locations 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 inter
93. ich 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 directories 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 you try 1s as a command you ll see home 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 There may or may not be a limit to how deep the file system can go You can easily have directories 10 levels down ALPHA VERSION TRUST THIS AND DIE ALPHA
94. ics 7 mv 27 29 30 Novell 7 OS 2 5 6 11 19 output redirection 34 35 parallel ports 16 partition disk 17 root 17 password 13 14 Peanuts 9 PID 39 pipes 36 POSIX 8 process 13 forking 13 pwd 24 Ritchie Dennis 7 rm 27 29 rmdir 26 serial ports 15 shell 4 19 completion 33 34 editing 33 globbing see shell wildcards job control 36 concepts 41 summary 40 job number 37 jobs 37 programming 19 prompt 14 19 script 19 wildcards 31 33 sort 21 36 spell 46 standard error 34 standard input 34 35 standard output 34 35 superuser 3 suspended 37 System V 8 tail 36 45 TCP IP 9 termination 37 Thompson Ken 7 Torvalds Linus iu 3 8 9 English usage 15 University of California Berkeley 7 8 Unix System Laboratories 7 8 VC see virtual consoles virtual consoles 41 VMS 5 6 w 97 we 46 Welsh Matt 5 wildcards see shell wildcards Windows NT 19 Wirzenius Lars 5 X Window System 8 9 yes 36
95. if the left side of the subexpression evaluates to true So if for example the file considered at the 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 9 2 tar the tape archiver 9 2 1 Introduction 9 2 2 Main options 9 2 3 Modifiers 9 2 4 Examples 9 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 92 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 9 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
96. illustrations for reviews or quotes in other works without this permission notice if proper citation is given 4 The GNU General Public License referenced below may be reproduced under the conditions given within it Exceptions to these rules may be granted for various purposes Write to Larry Greenfield at the above address or email greenfie gauss rutgers edu and ask These restrictions are here to protect us as authors not to restrict you as computer users ii ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION These conventions should be obvious but we ll include them here for the pedantic Bold Used to mark new concepts WARNINGS and keywords in a language italics Used for emphasis in text and occasionally for quotes or introductions at the be ginning of a section Also used to indicate commands for the user to type when showing screen interaction see below slanted Used to mark meta variables in the text especially in representations of the command line For example ls 1 foo where foo would stand for a filename such as bin cp Typewriter Used to represent screen interaction as in ls 1 bin cp rwxr xr x 1 root wheel 12104 Sep 25 15 53 bin cp Also used for code examples whether it is C code a shell script or something else and to display general files such as configuration files When necessary for clarity s sake these examples or figures will be enclosed in thin boxes
97. in edu alias tjo talk jimb cs oberlin edu alias tji talk jimb totoro bio indiana edu alias mroe more alias moer more alias email emacs f vm alias ed2 emacs d floss 0 fg grey95 bg grey50 You might have noticed a few odd things about them First of all I leave off the quotes in a few of the aliases for example rd Strictly speaking quotes aren t always necessary If you re just aliasing a single long command to give it a name that s easier to type you can do without the quotes alias rf refrobnicate ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 69 However 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 backslash grey95 backslash bg backslash grey50 backslash As you probably 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 com mand I meant to type more Aliases do not interfere with your passing arguments to a program prompt gt mroe hurd txt does invoke the more program
98. ine Editing ooa a 33 5 2 2 Command and File Completion oaoa a a 33 5 3 The Standard Input and The Standard Output aaaea e 34 5 3 1 Unix Concepts oaaae 34 5 3 2 Output Redirection aoaaa aa a 34 5 3 3 Input Redirection oaa aa e 35 5 3 4 Solution The Pipe aoaaa aa aa 020 0000 0000000200084 36 5 4 Multitasking 2 0 0 00 00 0000 00000 0002 2 eee 36 5 4 1 The Basics 2 2 2 aaa 36 5 4 2 What Is Really Going On Here 2 2 ee en 41 5 5 Virtual Consoles Being in Many Places at Once oaaao aaae 41 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION vii 6 Powerful Little Programs 43 6 1 The Power of Unix ooa aaa a 43 6 2 Operating on Files oaaae 43 6 3 What s in the File o aaa aaa en 44 6 4 Commands to Operate on File Attributes oaaae 45 6 5 Commands to Operate of File Contents oaa aaa a 45 7 Editing files with Emacs 49 7 1 What s emacs aoaaa aaa 000000000002 ee 49 7 2 Editing Many Files at Once 2 aa 51 7 3 Ending an Editing Session 2 52 74 The Meta Key 0 0 00 e 52 7 5 Cutting Pasting Killing and Yanking aoaaa aaa o 53 7 6 Searching and Replacing oaoa aaa e 54 7 7 What s Really Going On Here 2 a 55 7 8 Asking Emacs for Help oaa aaa a 56 7 9 Specializing Buffers Modes 2 0 00 00000000 0000000000 56 7 10 Programming Modes aoaaa aaa 57 7 10 1 C Mode onau aaa a 57 7 10 2 Scheme Mode oaaae en 58 7 10 3 Mail Mode aaa a 59 7 11
99. ing 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 if 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 shell and those lovely metacharacters are expanded So a test lik
100. ing 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 in a 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 in which this happens is Emacs 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 notice how the expression can be broken across two lines Lisp ignores whitespace generally autoload run scheme cmuscheme Run an inferior Scheme the way I like it t 64 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION The function autoload takes the name of a function quoted with
101. ing 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 however 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 gave the system the name UNIX Later Dennis Ritchie invented the C programming language In 1973 UNIX was rewritten in C which would have a major impact later on In 1977 UNIX was moved to a new machine away from the PDP machines it had run on previously This was aided by the fact UNIX was written in C Unix was slow to catch on outside of academic institutions but soon was popular with businesses as well The Unix of today is different from the Unix of 1970 It has two major versions System V from Unix System Laboratories USL a subsiderary of Novell and BSD Berkeley Software Distribution The USL version is now up to its forth release or SVR4 while BSD s latest version is 4 4 However there are many different versions of Unix besides these two Most versions of Unix are 1Tt was recently sold to Novell Previously USL was owned by AT amp T 2 System five revision four 8 ALPHA VERSION TRUST THIS A
102. ingle 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 Alt key and press F2 that is the function key number 42 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 2 8 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 Alt and pressing F1 Or you can move on to a third VC in the obvious way Alt H 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 Administrator 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 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
103. keep a shell up on VC 2 just in case I want to run something else without tying up VC 1 6 Make sure you are doing this from text consoles if you are running X windows or some other graphical application it probably won t work although rumor has it that X Windows will soon allow virtual console switching under Linux Chapter 6 Powerful Little Programs 6 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 these names mean right now Let s cover what each of these utilities do seperately and then Ill give some examples of how to use them together 6 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 wa
104. ld harm the system So two copies of etc re exist on my system now both named rc but one is in the directory etc and one is in home larry 28 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Then I created a third copy of etc re when I typed cp re frog the three copies are now etc re home larry re and home larry frog The contents of these three files are the same even if the names aren t The above example illustrates two uses of the command cp Are there any others Let s take a look e cp can copy files between directories if the first parameter is a file and the second parameter is a directory e 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 re etc passwd cp would normally create a new file with the contents identical to re and name it passwd However if etc passwd already existed cp would destroy the old file without giving you a chance to save it e Let s look at another example of cp home larry 1s F frog rc home larry mkdir rc_version home larry cp frog rc rc_version home larry 1s F frog re re_version home larry ls F rc_version frog rc home larry How did I just use cp Evidentally cp can take more than two parameters What the above command did is copied all the files listed frog and rc and placed them in the re_version directory In fact cp can take any number of parameters and interprets the
105. ll then you know enough not to be reading this section 67 68 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION the bash_profile as a sort of individualized AUTOEXEC BAT since it only affects one user not everyone on the system 8 1 1 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 bash profile alias 11 ls 1 That command defined a shell alias called 11 that expands to the normal shell command 1s 1 when invoked by the user So assuming that Bash has read that command in from your bash profile you can just type 11 to get the effect of ls 1 in only half the keystrokes What happens is that when you type 11 and hit Return Bash intercepts it because it s watching for aliases replaces it with ls l and runs that instead There is no actual program called 11 on the system no binary file waiting to be executed that is but the shell translated the alias into a valid program Clear Good Here are a zillion aliases from my own bash_profile alias ls 1s CF alias 11 1s 1 alias la 1s a alias rr rm r alias ro rm rm alias rd rmdir alias md mkdir alias pu pushd alias po popd alias ds dirs alias b b alias to telnet cs oberlin edu alias ta telnet altair mcs anl gov alias tg telnet wombat gnu ai mit edu alias tko talk kold cs oberl
106. lly layout of the rest of the disk are in conflict A special program called fsck can find these situations and hopefully correct them 3When I refer to the 80386 I am also talking about the 80486 unless I specifically say so Also I ll be abbreviating 80386 as 386 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 13 e Special routing programs for networks are run e 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 GMT and your CMOS clock a battery powered clock in your computer is probably set on local time 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 simple a running program since any one program can be running more than once there can be two or more processes for any particular program Processes can also be sub programs but that isn t important right now There are as many processes operating as there are programs In Unix a process an instance of a program is created by a system call a service provided by the kernel called fork 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 will be covered in 3 1 3 The User Acts getty perfor
107. lowing 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 fg 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 that was typed on the command line to start the program Before we go on let s kill this job and start it again in a different way The command is named kill and can be used in the following way home larry kill 1 1 Stopped yes 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 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 38 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION a job and typing jobs shows nothing then you know the kill was successful Usually it will tell you the job was terminated Now start yes running again like this home larry yes gt dev null If you read th
108. m 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 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
109. mbedded in the name probably it is more sensitive to write something like foo rather than foo find usr include xtype f exec 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 null 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 C find atime 1 fstype ext2 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 home xdev size 500k ls gt piggies is useful to see who has those files who clog th
110. mmands 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 have 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 find which lets the user search in the directory tree for specified groups of files tar 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 9 1 find the file searcher 9 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 R and rm R Good find is the recursive command Whenever you are thinking Well I have to do so and so
111. ms a fairly simple function It merely has to prompt the user to log in This process knowing as logging in 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 Started or The LINUX System Adminstrator s Guide When getty first starts up it displays a message of greeting or some such idea It is up to the system adminstrator what message if any it displays You should see after all the boot up procedures are done something like the following Welcome to the mousehouse Please have some cheese mousehouse login 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 when yo
112. n elc instead of el 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 and 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 e1 to load Usually it s located in a directory in load path called site lisp or local elisp or something see the example load 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 If a person s emacs contains any errors Emacs will not attempt to load default el but 2 instead will just stop flash
113. n machine alpha and that on machine beta there is the tape unit dev rst0O 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 the tar file In this case we could write rsh beta dd if dev rstO 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 94 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 9 4 sort the data sorter 9 4 1 Introduction 9 4 2 Options 9 4 3 Examples Chapter 10 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 10 1 Avoiding Errors Many users report frustration with the Unix operating system at one time or another frequently because of their own doing A feature of the Unix operating system that many
114. n change our current directory using cd For instance try home larry cd home home 1s F larry sam shutdown steve user1 home t 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 be used for stylistic purposes ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 25 A generic template looks like cd directory If you omit the 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 bint As you can see cd allows you to give either absolute or relative pathnames An absolute 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 local is a directory under usr and bin is a directory under local co 9D The directory a There are two directories used only for relative pathnames and refers to the current directory and is the parent directory These are 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
115. nally 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 lisp interpreter get its value There is a special mode for evaluating Lisp expressions in Emacs called lisp interaction mode Usually there is a buffer called scratch that is already 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 j at the end of it In lisp interaction mode C j is bound to eval print last sexp 11 Sometimes unofficially called Elisp ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 61 An sexp is an s expression which means a balanced group of parentheses including 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 load path should get you something like this load path C j 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
116. nds also let you specify a file to operate on so lt isn t used as much in day to day operations as other techniques For 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 36 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 5 3 4 Solution The Pipe Many Unix commands produce a large amount of information For instance it is not uncommon 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 1s usr bin it s necessary to 4 more will pause once every screenful of information For use another Unix command called more instance move lt etc re will display the file etc re just like cat etc re would except that more will let you read it 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 home larry rm temp ls However Unix supplies a much cleaner way of doing that You can just use the command 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 progr
117. nds for Line Printer although it could be a laser printer lp_init 1p0 exists 0 using polling driver That message says it has found one parallel port and is using the standard driver for it The Linux kernel also tells you a little about memory usage Memory 7296k 8192k available 384k kernel code 384k reserved 128k data This said that the machine had 8 megabytes of memory Some of this memory was reserved for the kernel just the operating system The rest of it could be used by programs Please note that the 8 megabytes the kernel talks about here is very fast memory called RAM for random access memory This memory is lost once you turn your machine off The other type of memory is general called a hard disk It s like a large floppy disk perme nantly in your computer the contents stay around even when the power is off The kernel now moves onto looking at your floppy drives In this example the machine has two drives In DOS 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 fdt Floppy drive s fd0 is 1 2M fdi is 1 44M floppy FDC version 0x90 Now LINUX moves onto less needed things such as network cards The following should be described in The Linux Networking Guide and is beyond the scope of this document SLIP version 0 7 5 4 channels OK plip c v0 04 Mar 19 1993 Donald Becker becker super org plip0 using par
118. nly match whole lines Remember if you don t specify any files grep will examine stdin we clw file file fileN we 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 we which of the three to count Thus we cw will count the number of characters and words but not the number of lines we defaults to counting everything words lines and characters One nice use of we is to find how many files are in the present directory 1s we w If you wanted to see how many files that ended with c there were try 1s c we w spell filel file2 fileN spell is a very simple Unix spelling program usually for American English spell is 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 spell 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 ispe11 should be fairly obvious consult the
119. now certain facts about your console 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 these nice features represented a problem to programmers how were they to know what the system s terminal could support and what it couldn t if it was changing from day to day What eventually happened was that the Digital Equipment Corporation s VT 100 terminal became a sort of lowest common denominator standard It supports all standard characters some basic cursor movement commands reverse video and a few other things Programs counted on being able to find a vt100 terminal and terminal manufacturers were expected to support a vt100 compatibility mode even if their terminal had features above and beyond the standard vt100 This standard is still used today even though most terminals can support much more and anyway most users do their work in a graphical windowing system The lesson portability is more important than fancy features Budding programmers take note So this is what the TERM variable is used for programs check its value to make sure that they have a vt100 or something close to it before they
120. ny 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 of 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 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 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 is the search will match up
121. oblem the parent 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 Respectively they stand for copy move and remove 4 4 1 cp Like a Monk 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 Error saving disk full cp can also overwrite existing files I ll talk more about that danger later The first parameter to cp is the file to copy the last is where to copy it You can copy to either a different filename or a different directory Let s try some examples home larry ls F etc re etc re home larry cp etc re home larry 1s F re home larry cp rc frog home larry 1s F frog rc home larry The first cp command I ran took the file etc re which contains commands that the Unix system runs on boot up and copied it to my home directory cp doesn t delete the source file so I didn t do anything that cou
122. ommands that will alter a file perform a certain operation on the file or display statistics on the file grep nvwx number expression file1 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 46 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION home larry cat animals Animals are very interesting creatures One of my favorite animals is the tiger a fearsome beast with large teeth I also like the lion it s really neat home larry grep iger animals the tiger a fearsome beast 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 try a 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 o
123. on all those kind of files in my own partition you have better think about using find In a certain sense the fact that find finds files is just a side effect its real occupation is to evaluate The basic structure of the command is as follows find path expression 85 86 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 9 1 2 Expressions The expression part
124. on the file hurd txt In fact knowing how to make your own aliases is probably at least half of all the shell customiza tion you ll ever do Experiment a little find out what long commands you find yourself typing frequently and make aliases for them and then don t forget to use the aliases You ll find that it makes working at a shell prompt a much more pleasant experience 8 1 2 Environment Variables The other major thing one does in a bash_profile 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 if the environment variable FRUGGLEPATH is set to a different filename it will look there instead Hmmm what did that mean Well every program executes in an environment and that 4 The environment could be said to environment is defined by the shell that called the program exist within the shell Programmers have a special routine for querying the environment and the fruggle program 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 had bet
125. ontains 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 8 4 Seeing Some Examples The ultimate example I can give you is a running Linux system So if you have Internet access feel free to telnet to floss life uiuc edu Log in as guest password 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 anything 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 84 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Chapter 9 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 co
126. opyrighted 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 giving a copy away you can t prevent the person you sold it to from giving it away for free It also means that the source code must also be available This is useful for programmers The license also says that anyone who modifies the program must also make his version freely redistributable LINUX supports most of the popular Unix software including The X Window System This is a rather large program from MIT allowing computers to create graphical windows and is used on many different Unix platforms LINUX is mostly System V mostly BSD compatible and mostly POSIX 1 a document trying to standardize operating systems compliant LINUX probably complies with much of POSIX 2 another document from the IEEE to standardize operating systems It s a mix of all three standards BSD System V and POSIX Many of the utilities included with LINUX distributions are from the Free Software Foundation and are part of GNU Project The GNU Project is an effort to write a portable advanced 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 LINUX is not easily ported move
127. or if it even exists Hold down the key labeled Ctrl and press d then let go 22 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 folder 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 directories 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 home 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 First we are in the root directory This signifies the directory called home It is inside the root directory This is the directory larry wh
128. ort 1993 mkdir can actually take more than one parameter and 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 chap1 report 1993 chap2 home larry report 1993 ls F chap1 chap2 home larry report 1993 Finally there is the opposite of mkdir rmdir for remove directory rmdir works exactly as you think it should work rmdir directory An example of rmdir is home larry report 1993 rmdir chapi chap3 rmdir chap3 No such file or directory home larry report 1993 ls F chap2 home larry report 1993 cd home larry rmdir report 1993 rmdir report 1993 Directory not empty home larry 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 27 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 In fact this isn t even a pr
129. ould 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 Control 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 it moves smoothly on to the next line C b for backward does the opposite And while we re at it C n and C p take you to the next and previous lines respectively Hold down C b until you ve been taken all the way back to the upper left corner and then keep it held a little longer You should hear an annoying bell sound and see the message Beginning of buffer appear in the minibuffer At this point you might wonder But what is a buffer Well here s how it works 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
130. our 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 78 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION It seems to work fine either way I m wondering if there s any point recommending an amp or not Kar Notice that some commands are run in the background i e they are followed with a amp while others aren t The distinction is that some programs will start when you start X Windows and keep going until you exit these get put in the background Others execute once and then exit immediately xsetroot 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 Pll deal with only those two since they re the window managers you ll be most likely to encounter with Linux The twmrc is not a shell script it s actually written in a language sp
131. ove 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 C 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 Backspace Delete preceding character the one you just typed 7 2 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 2 The command to Emacs can contain is the actual amount of memory available on the machine 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 etc You also get filename completion meaning that if you ve typed enough of a filename at the prompt to identify the file uniquely you can just hit Tab 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 Tab but PII let you experiment to find out how the two differ Once you have the full filename in the minibuffer hit Return and Emacs will
132. over the network e And remember be polite Most people work on free software for the fun of it and because they have big hearts Don t ruin it for them the LINUX community has already disillusioned too many developers and it s still early in LINUX s life 2 Especially this one 98 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Appendix A 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 to most of the Free Software Foundation s software and to any other program whose authors commit to using it Some other Free Software Foundation 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
133. ovided 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 2 You may modify your copy or copies of the Program or any portion of it thus forming 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 the terms of this License ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 101 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
134. per 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 66 d The comment character in Lisp is Emacs ignores anything following one unless it appears inside a literal string like so 3 these two lines are ignored by the Lisp interpreter but the 33 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 functions 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 functions and variables instead of just functions The default extension for Emacs Lisp files is e1 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 63 i
135. port 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 The i option 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 Chapter 5 Working with Unix 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 Unix is a powerful system for those who know how to harness its power In this chapter Ill try to describe various ways to use Unix s shell bash more efficently 5 1 Wildcards In the previous chapter you learned about the file maintence commands cp mv and rm Occasionally you 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 31 32 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION
136. ram 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 Software 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 MERCHANTABILITY or FIT NESS 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 something other than show w and 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
137. rather fg bg amp jobs and kill are all shell builtins actually sometimes kill 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 they are logged into the same machine 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 program 5 5 Virtual Consoles Being in Many Places at Once Linux supports virtual consoles These are a way of making your s
138. re 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 fact 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 6 Sometimes on a few machines C SPC doesn t work For these machines you must use C 54 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 7 6 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 gadfly in the
139. re 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 true 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 Tab to finish it Say you ALPHA VERSION TRU
140. robably 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 bash_profile export 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 bash_profile by using its value in setting my PATH The curly braces are a further level of quoting they delimit the extent of what the is to evaluate so that the shell doesn t get 5 Remember that you can always execute programs in the current directory by being explicit about it i e foo ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 73 confused by the text immediately following it bin in this case Here is another example of the effect they have prompt gt echo HOME foo home kfogelfoo prompt gt Without the curly braces I would get nothing prompt gt
141. roblem might arise that all the characters are some type of gibberish is it a bug or a feature Surprisingly this is a feature the gibberish is caused by certain control sequences that somehow appeared footnoteHowever because you have all the source code you can easily disable this particular escape sequence and recompile the kernel Hopefully this book will help you to tell the different situations apart 2 2 2 Trivial Linux Matters 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 mIn Imal 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 2 2 3 Commercial Software in LINUX For better or for worse there is now commercial software available for LINUX Although it isn t a fancy word processing application Motif is a package that must be payed for and the source isn t given out Motif is a user interface for The X Window System that vaguely resembles MicroSoft Windows 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 A covers the LINUX kernel the GNU That s a form of ne
142. ry 1s F shorter this is a long file 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 rc 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 in 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 1 C t means hold down the key labeled Ctrl then press the t key Then release the Ctrl key cp etc rc this is a long file 34 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION and hit Tab bash beeps at me That s because three files usr bin ld usr bin ldd and usr bin 1d86 start usr bin 1d on my system If you try a completion and bash beeps you can immediately hit Tab again to get a list of all the files your start matches so far That way if you aren t sure of the exact
143. ry 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 There are good reasons for this strange command to exist but we won t go into them now To get them to stop you d normally type ctrl C to kill it but instead you should type ctrl Z this time It appears to have stopped but there will be a message before your prompt looking more or less like this i 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 before 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 And you can type ctrl C to kill it for good once you ve seen enough Let s pick apart that message we got from the shell i 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 fol
144. s 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 1 Older filesystems in LINUX only stored one date since they were derived from Minix If you have one of these filesystems some of the information will merely be unavailable operation will be mostly unchanged 43 44 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION e The permissions Every file has permissions associated with it which tell Unix who can access what file or change it or in the case of programs execute it Each of these permissions can be toggled seperately for the owner the group and all other users touch file 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 Rcfv mode file file2 fileN The command used to change the permissions on a file is called chmod 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
145. 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 7 9 Specializing Buffers Modes Emacs buffers have modes associated with them The reason for this is that your needs when writing a mail message are very different from your needs when say writing a program Rather than try to come up with an editor that would meet every single need all the time which would be To make matters worse there are Major Modes and Minor Modes but you don t need to know about that ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 57 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 bu
146. t 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 ic ic 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 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 Tab anywhere on a line of code correc
147. t not only in longer time to perform the command but even in timeout errors so be careful e bs nn both reads and writes nn bytes at a time It overrides ibs and obs keywords e 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 e skip nbl and seek nl tell the program to skip nbl blocks respectively at the beginning of input and at the beginning of output Of course the latter case makes sense if conversion notrunce 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 skipping 512x512 bytes that is 256KB It was not precisely what you wanted wasn t it ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 93 e count nbl 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 converston convert the file as specified by its argument Possible conver sions are ascil which converts from EBCDIC to ASCII ebcdic and ibm which both perform
148. t there can be other differences as well 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 previously 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 All 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 commands 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 Meta and the Shift 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 usef
149. t with a correctly configured rhosts file on floss life uiuc edu you could run a program on floss life uiuc edu and have the output go to cs oberlin edu without ever having to log in or type a password 82 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 floss life uiuc edu That would mean that I could run programs on floss with output going to any of the machines listed as long 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 uluc 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
150. ter be the name of a file that fruggle can use instead of the default frugglerc Enough yakking here s how you can change your environment in Bash 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 It could get tiresome really fast 70 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION prompt gt export PGPPATH home kfogel secrets pgp You may think of the 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 ones containing encryption keys ahem 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 kfogel secrets pgp instead I had to read the pgp manual to find out the exact name of the variable and what it does but in fact it s a common convention to use the name of the program in capital letters prepended to the suffix PATR How can you check the value of an environment variable Like this prompt gt echo PGPPATH home kfogel pgp prompt gt Notice the
151. 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 collective 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 distribution medium does not bring the other work under the scope of this License 3 You may copy and distribute the Program or a work based on it under Section
152. 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 the user types 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 1The indicates that the user typed a space ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 21 To end many Unix commands type Ctrl d P Ctrl d lis the end of file character or EOF for short Alternatively it stands for end of text depending on what book you read 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 d it will output those lines in a sorted order By the way these types of programs are called filters because they take in text filter it and output the text slightly differently Well cat is a very basic filter and doesn t change the input We will talk more about filters later 4 2 Helping Yourself The man command displays reference p
153. ther group of people believe that bigger kernels are better and make more efficent operating systems Some versions of Unix are designed like this including LINUX One ironic thing to note here is that micro kernels aren t necessarily smaller then macro kernels it s the philosophy that separates the two 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 Hopefully you already know how to use the correct tools that way you won t use the hammer to try and tighten a screw The moral of the story Don t change the way you work to suit the operating system but be aware of the operating system Don t wish for a tool that isn t in your box use the tools in your box to make a new one 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 work
154. 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 kill 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 terminate it home larry ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 39 There it s gone Now start up a few jobs running in simultaneously like this home larry yes gt dev null amp 1 1024 home larry yes sort gt dev null amp 2 1026 home larry yes uniq gt dev null and here type ctrl Z to suspend it please 3 Stopped yes uniq gt dev null 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 ctrl Z and then type bg So we started those two commands running in the background The third is suspended and inactive at the moment You should notice that the machine has definitely become slower now as the two running ones require significant amoun
155. tly indents that line If yow 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 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 59 rotate and have already applied it to arguments in the process buffer like so gt rotate a b c d 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 yov 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 7 10 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 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 7 11 Being Even More Ef
156. 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 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 line The key is described using a string The special syntax C lt char gt means the Control key held down while the key lt char gt is pressed Likewise M lt char gt indicates the Meta 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 online help facilities come in Once you have decided what kind of func tion you are looking for you can use Emacs to track down its exact name
157. tors 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 is addressed as you Activities other than copying distribution and modification are not covered by this 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 1 You may copy and distribute verbatim copies of the Program s source code as you receive it in any medium pr
158. ts of CPU time Each one told you it s job number The first two also showed you their Process IDentification 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 home larry fg 2 and then hit ctrl C to kill it As this demonstrates fg takes parameters beginning with as well In fact you could just have typed this home larry 2 and then hit ctrl C to kill it 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 home larry jobs 1 Running yes gt dev null amp 3 Stopped yes uniq gt dev null That pretty much says it all The means that job number 1 is second in line to be put in the foreground if you just type fg without giving it any parameters However you can get to it by naming it if you wish home larry fg 1 yes gt dev null now type ctr1 Z to suspend it 40 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 1 Stopped yes gt dev null Having changed to job number 1 and then suspending it has also changed the priorities of all your jobs You can see this with th
159. tworking More on that later 10 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION Library General Public License reproduced in Appendix B covers most of the computer code applications depend on 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 Also copyright notices are enforced by lawsuits by the copyright holders either the Free Software Foundation or Linus Torvalds In general this means you can t go wrong if you obey the spirit of what they re asking they probably won t sue you and all will be well Unless the rights get sold It s also a good idea not to think up schemes to get around these two copyrights it s almost definitely possible but merely causes grief to all parties involved Chapter 3 Getting Started This login session 13 99 but for you 11 88 3 1 Starting to Use Your Computer You may have previous experience with MS DOS or other single user operating systems 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
160. u installed LINUX you were prompted for some very witty name It isn t very important but whenever it comes up I ll be using mousehouse or rarely Lionsden 14 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION After entering larry 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 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 like this home larry You ll be seeing a lot of this Commands will be introduced in the next chapter 3 2 Leaving the Computer Do not just turn off the computer You risk 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 perform
161. uggest 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 Occasionally the line between the two isn t so clear 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 That s a command template and you ll see it whenever a new command is introduced Anything contained in brackets P and is optional it doesn t have to be there Anything slanted should usually be changed before trying the command You ll rarely have a directory named directory 4 3 2 The Current Directory and cd 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 Ifit doesn t try the command pwd for present working directory mousehouse gt pwd home larry mous ehouse gt As you can see pwd tells you your current directory a very simple command Most commands act by default on the current directory such as 1s We ca
162. ul 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 7 10 Programming Modes 7 10 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 Tab is bound to c indent command This means that hitting the Tab key does not actually insert a tab character Instead if you hit Tab anywhere on a line Emacs automatically indents that line correctly for its 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 10 Well there s no reason not to use his name He is Richard Stallman also sometimes referred to as rms because that s his login name 58 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION In order to do this it assumes that the previous line s 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
163. ur Fault 10 2 1 When Is There a Bug 10 2 2 Reporting a bug A The GNU General Public License ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 85 Le 85 Le 85 re 86 Le 86 re 87 re 88 ee 89 re 90 ee 91 re 91 Co 91 Lo 91 ee 91 re 91 Co 91 Le 92 re 93 re 94 Co 94 Le 94 re 94 95 Lo ee 95 Lo ee 96 Lo ee 96 Lo ee 97 99 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 1 B The GNU Library General Public License 107 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 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 This Book Are you someone who should read this book Do you want to learn Unix Have you just gotten Linux from somewhere installed it and want to know what to do next 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 ll 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 relies on a few things that the author can t control First of all this book as do most Unix books assumes that
164. users love when they re working well and hate after a late night session is how very few commands ask for confirma tion When a user is awake and functioning they rarely think about this and it is an assest since it let s them work smoother However 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 adminstrators should make regular backups of their system Once a week is good enough to salvage many files See the The LINUX System Adminstrator s Guidefor 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 95 96 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION home larry report cp report
165. ut half a normal 25 line screen L 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 a This will also search for the next occurence of your regular expression If you specified more than one file on the command line this will move to the next file a p This will move the the previous file Exits from more 2 head lines filel file2 fileN head will display the first ten lines in the listed files or the first 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 6 4 Commands to Operate on File Attributes A file attribute is for example who owns the file or whether or not a file is an executable 6 5 Commands to Operate of File Contents This section discusses the c
166. 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 x Fmacs some_file txt Fundamental Top These two asterisks are displayed as soon as you modify the buffer and remain 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 Control 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 1fn case you hadn t noticed yet many of Emacs movement commands consist of combining Control with a single mnemonic letter ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION 51 C f Move forward one character C b M
167. you you can have Emacs do anything for you the command to do so is called auto fill 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 line and previous line but that would be very inefficient since they are already bound to C n and C p et T We call C q a key even though it is produced by holding down Control and pressing q because it is a single ASCII character You might expect this to be called wrap mode or auto wrap mode but you d be wrong Sorry 56 ALPHA VERSION TRUST THIS AND DIE ALPHA VERSION By the way if you look at your mode line after invoking auto fill mode you will notice 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
168. 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 7 10 2 Scheme Mode This is a major mode that won t do you any good unless you have a compiler or an interpreter 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 PII 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 because 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 IIl talk about how 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 promp

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