UNIX For Beginners
Contents
1. Of these niceties is probably the most use ful and you should get used to it The others are frills but worth knowing If you should ever have to turn off the special meaning of etc enclose the entire argu ment in quotes single or double as in Is 9 What s in a Filename Continued When you first made that file called junk how did UNIX know that there wasn t another junk somewhere else especially since the person in the next office is also reading this tutorial The reason is that generally each user of UNIX has his own directory which contains only the files that belong to him When you create a new file unless you take special action the new file is made in your own directory and is unrelated to any other file of the same name that might exist in someone else s directory The set of all files that UNIX knows about are organized into a usually big tree with your files located several branches up into the tree It is pos sible for you to walk around this tree and to find any file in the system by starting at the root of the tree and walking along the right set of branches To begin type Is is the name of the root of the tree a convention used by UNIX You will get a response something like this bin dev etc lib tmp usr This is a collection of the basic directories of files that UNIX knows about On2. Mistakes in Typing If you make a typing mistake and see it before the carriage return has been typed there are two ways to recover The sharp character erases the last character typed in fact successive uses of erase characters back to the beginning of the line but not beyond So if you type badly you can correct as you go dd atte e is the same as date The at sign erases all of the characters typed so far on the current input line so if the line is irretrievably fouled up type an and start over on the same line What if you must enter a sharp or at sign as part of the text If you precede either or by a backslash it loses its erase meaning This implies that to erase a backslash you have to type two sharps or two at signs The backslash is used extensively in UNIX to indicate that the following character is in some way special Readahead UNIX has full readahead which means that you can type as fast as you want whenever you want even when some command is typing at you If you type during output your input characters will appear intermixed with the output characters but they will be stored away by UNIX and interpreted in the correct order So you can type two commands one after another without waiting for the first to fin ish or even begin Stopping a Program You can stop most programs by typing the character
3. DEL perhaps called delete or rubout on your terminal There are exceptions like the text editor where DEL stops whatever the program is doing but leaves you in that program You can also just hang up the phone The inter rupt or break key found on most terminals has no effect Logging Out The easiest way to log out is to hang up the phone You can also type login name of new user and let someone else use the terminal you were on It is not sufficient just to turn off the terminal UNIX has no time out mechanism so youw ll be there forever unless you hang up Mail When you log in you may sometimes get the message You have mail UNIX provides a postal system so you can send and receive letters from other users of the system To read your mail issue the command mail Your mail will be printed and then you will be asked Save If you do want to save the mail type y for yes any other response means no How do you send mail to someone else Sup pose it is to go to joe assuming joe is some one s login name The easiest way is this mail joe now type in the text of the letter on as many lines as you like after the last line of the letter type the character control d that is hold down control and type a letter d And that s it The control d sequence usually called EOT
4. is used throughout UNIX to mark the end of input from a terminal so you might as well get used to it There are other ways to send mail _ you can send a previously prepared letter and you can mail to a number of people all at once For more details see The notation means the command in section I of the UNIX Programmer s Manual Writing to other users At some point in your UNIX career out of the blue will come a message like Message from joe accompanied by a startling beep It means that Joe wants to talk to you but unless you take explicit action you won t be able to talk back To respond type the command write joe This establishes a two way communication path Now whatever Joe types on his terminal will appear on yours and vice versa The path is slow rather like talking to the moon If you are in the middle of something you have to get to a state where you can type a command Normally whatever program you are running has to terminate or be terminated If you re editing you can escape temporarily from the editor _ read the manual A protocol is needed to keep what you type from getting garbled up with what Joe types Typi cally it s like this Joe types write smith and waits Smith types write joe and waits Joe now types his message as many lines as he likes When he s ready for a reply he signals it by typing 0 which stands for ov
5. text editor Since is thoroughly docu mented in and explained in A Tutorial Introduction to the UNIX Text Editor we won t spend any time here describing how to use it All we want it for right now is to make some files A file is just a collection of information stored in the machine a simplistic but adequate definition To create a file with some text in it do the fol lowing ed invokes the text editor a command to ed to add text now type in whatever text you want g signals the end of adding text At this point we could do various editing operations on the text we typed in such as correcting spelling mistakes rearranging paragraphs and the like Finally we write the information we have typed into a file with the editor command w w junk will respond with the number of characters it wrote into the file called junk Suppose we now add a few more lines with a terminate them with and write the whole thing out as temp using w temp We should now have two files a smaller one called junk and a bigger one bigger by the extra lines ZPE called temp Type a q to quit the editor What files are out there The for list command lists the names not contents of any of the files that UNIX knows about If we type ls the response will be junk temp which are indeed our two files They are so
6. It The beauty of this scheme is that now if you change your mind about what a paragraph should look like you can change the formatted output merely by changing the definition of PP and re running the formatter As a rule of thumb for all but the most trivial jobs you should type a document in terms of a set of macros like PP and then define them appro priately As long as you have entered the text in some systematic way it can always be cleaned up and re formatted by a judicious combination of editing and macro definitions The packages of for matting commands that we mentioned earlier are simply collections of macros designed for particu lar formatting tasks One of the main differences between and the other formatters is that macros in can only be lines of text and formatting commands In and macros may have arguments so they can have different effects depending on how they are called in exactly the same way that the sp command has an argument the number of spaces you want Miscellany In addition to the basic formatters UNIX pro vides a host of supporting programs and let you integrate mathematics into the text of a document in a language that closely resembles the way you would speak it aloud and detect possible spelling mistakes in a document looks for lines containing a particular text pattern rather like the editor s con text search does but on a whole series of
7. alter that fact If you forget what directory you re in type pwd print working directory to find out It is often convenient to arrange one s files so that all the files related to one thing are in a direc tory separate from other projects For example when you write your book you might want to keep all the text in a directory called book So make one with mkdir book then go to it with chdir book then start typing chapters The book is now found in presumably asr your name book To delete a directory see You can go up one level in the tree of files by saying chdir is the name of the parent of whatever directory you are currently in For completeness is an alternate name for the directory you are in Using Files instead of the Terminal Most of the commands we have seen so far pro duce output on the terminal some like the editor also take their input from the terminal It is univer sal in UNIX that the terminal can be replaced by a file for either or both of input and output As one example you could say Is to get a list of files But you can also say ls gt filelist to get a list of your files in the file filelist filelist will be created if it doesn t already exist or overwritten if it does The symbol gt is used throughout UNIX to mean put the output on the following file
8. and would prob ably even make mistakes Fortunately there is a shortcut You can say pr chap The means anything at all so this translates into print all files whose names begin with chap listed in alphabetical order This shorthand nota tion is not a property of the command by the way It is system wide a service of the program that interprets commands the shell Using that fact you can see how to list the files of the book ls chap produces chap1 1 chap1 2 chap1 3 The is not limited to the last position in a file name _ it can be anywhere Thus rm junk removes all files that contain junk as any part of their name As a special case by itself matches every filename so pr prints all the files alphabetical order and rm removes all files You had better be sure that s what you wanted to say The is not the only pattern matching fea ture available Suppose you want to print only chapters 1 through 4 and 9 of the book Then you can say pr chap 12349 The means to match any of the characters inside the brackets You can also do this with pr chap 1 49 Ta z matches any character in the range a through z There is also a character which matches any single character so pr will print all files which have single character names
9. document prepara tion There are three major formatting programs that is programs which produce a text with justified right margins automatic page numbering and titling automatic hyphenation and the like The simplest of these formatters is which in fact is sim ple enough that if you type almost any text into a file and roff it you will get plausibly formatted output You can do better with a little knowledge but basically it s easy to learn and use We ll get back to shortly is similar to but does much less for you auto matically It will do a great deal more once you know how to use it Both and are designed to produce output on ter minals line printers and the like The third for matter pronounced tee roff instead drives a Graphic Systems phototypesetter which produces very high quality output on photographic paper This paper was printed on the phototypesetter by Because and are relatively hard to learn to use effectively several packages of canned format ting requests are available which let you do things like paragraphs running titles multi column out put and so on with little effort Regrettably details vary from system to system ROFF The basic idea of and of and for that matter is that the text to be formatted contains within it for matting commands that indicate in detail how the formatted text is to look For example there might be commands that speci
10. files For example grep ing chap will find all lines ending in the letters ing in the series of files chap It is almost always a good practice to put quotes around the pattern you re searching for in case it contains characters that have a special meaning for the shell counts the words and optionally lines in a set of files translates characters into other characters for example it will convert upper to lower case and vice versa This translates upper into lower tr A Z a z prints a list of the differences between two files so you can compare two versions of something automatically which certainly beats proofreading by hand sorts files in a variety of ways makes cross references makes a permuted index keyword in context listing Most of these programs are either indepen dently documented like and or are sufficiently sim ple that the description in the UNIX Programmer s Manual is adequate explanation IV PROGRAMMING UNIX is a marvelously pleasant and productive system for writing programs productivity seems to be an order of magnitude higher than on other inter active systems There will be no attempt made to teach any of the programming languages available on UNIX but a few words of advice are in order First UNIX is written in C as is most of the applications code If you are undertaking anything substantial C is the only reasonable choice More
11. in the file After you learn how to use the editor you can be selec tive about the parts you print There are times when it s not feasible to use the editor for printing For example there is a limit on how big a file can handle about 65 000 characters or 4000 lines Secondly it will only print one file at a time and sometimes you want to print several one after another So here are a couple of alterna tives First is the simplest of all the printing pro grams simply copies all the files in a list onto the terminal So you can say cat junk or to print two files cat junk temp The two files are simply concatenated hence the name cat onto the terminal produces formatted printouts of files As with prints all the files in a list The difference is that it produces headings with date time page number and file name at the top of each page and extra lines to skip over the fold in the paper Thus pr junk temp will list junk neatly then skip to the top of a new page and list temp neatly will also produce multi column output pr 3 junk prints junk in 3 column format You can use any reasonable number in place of 3 and will do its best It should be noted that is not a formatting pro gram in the sense of shuffling lines around and jus tifying margins The true formatters are and which we will get to in the section on document prepar
12. most systems usr is a directory that contains all the normal users of the system like you Now try ls usr This should list a long series of names among which is your own login name Finally try ls usr your name You should get what you get from a plain ls Now try cat usr your name junk if junk is still around The name asr your name junk is called the pathname of the file that you nor mally think of as junk Pathname has an obvious meaning it represents the full name of the path you have to follow through the tree of directo ries to get to a particular file It is a universal rule in UNIX that anywhere you can use an ordinary file name you can use a pathname Here is a picture which may make this clearer root bin etc usr dev tmp PIN TIN TIN TIN TIN adam eve mary juk junk temp Notice that Mary s junk is unrelated to Eve s This isn t too exciting if all the files of interest are in your own directory but if you work with someone else or on several projects concurrently it becomes handy indeed For example your friends can print your book by saying pr_ usr your name chap Similarly you can find out what files your neighbor has by saying Is usr neighbor name or make your own copy of one of his files by cp usr your neighbor his file
13. move files 5 nroff 9 on line manual 3 opr offline print 5 pathname 6 pattern match in filenames 5 pipes 8 pr print files 4 prof run time monitor 13 protection 7 ptx permuted index 11 pwd working directory 7 quotes 6 ratfor decent Fortran 13 readahead 2 reading list 13 redirect I O lt gt 7 RETURN key 1 rm remove files 5 rmdir remove directory 7 roff text formatting 9 root of file system 6 shell command interpreter 8 shell arguments 12 shell programming 12 shift shell arguments 12 sleep 12 sort 11 spell find spelling mistakes stopping a program 2 stty set terminal options 2 tabs set tab stops 2 terminal types 1 time time programs 13 tr translate characters 11 troff typesetting 9 typo find spelling mistakes 11 wc word count 11 who who is looged in 2 write to a user 3 yacc compiler compiler 13
14. rather than on the terminal Noth ing is produced on the terminal As another exam ple you could concatenate several files into one by capturing the output of in a file cat fl f2 f3 gt temp Similarly the symbol lt means to take the input for a program from the following file instead of from the terminal Thus you could make up a script of commonly used editing commands and put them into a file called script Then you can run the script on a file by saying ed file lt script Pipes One of the novel contributions of UNIX is the idea of a pipe A pipe is simply a way to connect the output of one program to the input of another program so the two run as a sequence of processes _ a pipe line For example prfgh will print the files f g and h beginning each on a new page Suppose you want them run together instead You could say cat f g h gt temp pr temprm temp but this is more work than necessary Clearly what we want is to take the output of and connect it to the input of So let us use a pipe cat f gh pr The vertical bar means to take the output from which would normally have gone to the terminal and put it into which formats it neatly Any program that reads from the terminal can read from a pipe instead any program that writes on the terminal can drive a pipe You can have as many elements in a pipelin
15. value by that much Now revert 11 10 in 10 Notice that 1 10 adds ten characters to the line length while 11 10 makes the line ten characters long The ti command indents in either direction just like in except for only one line Thus to make a new paragraph with a 10 character indent ou would say sp ti 10 New paragraph You can put running titles on both top and bot tom of each page like this he left top center top right top fo left bot tom center bottom right bottom The header or footer is divided into three parts which are marked off by any character you like We used a double quote If there s nothing between the markers that part of the title will be blank If you use a percent sign anywhere in he or fo the current page number will be inserted So to get centered page numbers with dashes around them at the top use he You can skip to the top of a new page at any time with the bp command if bp is followed by a number that will be the new page number The foregoing is probably enough about for you to go off and format most everyday documents Read for more details Hints for Preparing Documents Most documents go through several versions always more than you expected before they are finally finished Accordingly you should do what ever possi
16. UNIX For Beginners Brian W Kernighan ABSTRACT This paper is meant to help new users get started on UNIX It covers e basics needed for day to day use of the system _ typing commands correcting typing mistakes logging in and out mail inter console communication the file system printing files redirecting I O pipes and the shell e document preparation _ a brief tutorial on the ROFF formatter for beginners hints on preparing documents and capsule descriptions of some supporting software e UNIX programming _ using the editor programming the shell programming in C other languages There is also an annotated UNIX bibliography UNIX For Beginners Brian W Kernighan UNIX for Beginners Brian W Kernighan Bell Laboratories Murray Hill N J In many ways UNIX is the state of the art in computer operating systems From the user s point of view it is easy to learn and use and presents few of the usual impediments to getting the job done It is hard however for the beginner to know where to start and how to make the best use of the facilities available The purpose of this introduc tion is to point out high spots for new users so they can get used to the main ideas of UNIX and start making good use of it quickly This paper is not an attempt to re write the UNIX Programmer s Manual often the discussion of something is simply read section x in the man ual This implies that you will need a copy o
17. a tion There are also programs that print files on a high speed printer Look in your manual under and Which to use depends on the hardware configura tion of your machine Shuffling Files About Now that you have some files in the file system and some experience in printing them you can try bigger things For example you can move a file from one place to another which amounts to giving a file a new name like this mv junk precious This means that what used to be junk is now precious If you do an command now you will get precious temp Beware that if you move a file to another one that already exists the already existing contents are lost forever If you want to make a copy of a file that is to have two versions of something you can use the command cp precious temp1 makes a duplicate copy of precious in temp1 Finally when you get tired of creating and moving files there is a command to remove files from the file system called rm temp temp will remove all of the files named You will get a warning message if one of the named files wasn t there Filename What s in a So far we have used filenames without ever saying what s a legal name so it s time for a couple of rules First filenames are limited to 14 charac ters which is enough to be descriptive Second although you can use almost any character in a file name
18. ble to make the job of changing them easy First when you do the purely mechanical oper ations of typing type so subsequent editing will be easy Start each sentence on a new line Make lines short and break lines at natural places such as after commas and semicolons rather than ran domly Since most people change documents by rewriting phrases and adding deleting and rear ranging sentences these precautions simplify any editing you have to do later The second aspect of making change easy is not to commit yourself to formatting details too early For example if you decide that each para graph is to have a space and an indent of 10 charac ters you might type before each sp ti 10 But what happens when later you decide that it would have been better to have no space and an indent of only 5 characters It s tedious indeed to go back and patch this up Fortunately all of the formatters let you delay decisions until the actual moment of running The secret is to define a new operation called a macro for each formatting operation you want to do like making a new paragraph You can say in all three formatters de PP sp ti 10 This defines PP as a new or or operation whose meaning is exactly sp ti 10 The marks the end of the definition When ever PP is encountered in the text it is as if you had typed the two lines of the definition in place of
19. common sense says you should stick to ones that are visible and that you should probably avoid characters that might be used with other meanings We already saw for example that in the command Is t meant to list in time order So if you had a file whose name was t you would have a tough time listing it by name There are a number of other characters which have special meaning either to UNIX as a whole or to numerous commands To avoid pitfalls you would probably do well to use only letters numbers and the period Don t use the period as the first character of a filename for reasons too complicated to go into On to some more positive suggestions Sup pose you re typing a large document like a book Logically this divides into many small pieces like chapters and perhaps sections Physically it must be divided too for will not handle big files Thus you should type the document as a number of files You might have a separate file for each chapter called chap1 chap etc Or if each chapter were broken into several files ou might have chap1 1 chap1 2 chap1 3 chap2 1 chap2 2 You can now tell at a glance where a particular file fits into the whole There are advantages to a systematic naming convention which are not obvious to the novice UNIX user What if you wanted to print the whole book You could say pr chap1 1 chap1 2 chap1 3 but you would get tired pretty fast
20. e suppose you want to add to your login sequence something to print your mail if you have some Thus knowing that mail is stored in a file called mailbox you could say if r mailbox mail This says if the file mailbox is readable execute the command As another example you could arrange that the count procedure count every hour by default but allow an optional argument to specify a different time Simply replace the sleep 1 line by if 1x x sleep 3600 if 1x x sleep 1 The construction if lx x tests whether 1 the first argument was present or absent More complicated conditions can be tested you can find out the status of an executed command and you can combine conditions with and or not and parentheses _ see You should also read which describes how to manipulate arguments to shell command files Programming in C As we said C is the language of choice every thing in UNIX is tuned to it It is also a remarkably easy language to use once you get started Sections II and III of the manual describe the system inter faces that is how you do T O and similar functions You can write quite significant C programs with the level of I O and system interface described in Programming in C A Tutorial if you use existing programs and pipes to help For example rather than learning how to open and close files you can at least temporar
21. e Lesk Bell Laboratories internal memorandum A macro package to isolate the novice from the vagaries of the formatting programs If this specific package isn t available on your system something similar probably is This one works with both and Programming Programming in C A Tutorial Brian Kernighan Bell Laboratories internal memorandum The easi est way to start learning C but it s no help at all with the interface to the system beyond the simplest IO Should be read in conjunction with C Reference Manual Dennis Ritchie Bell Labo ratories internal memorandum An excellent refer ence but a bit heavy going for the beginner espe cially one who has never used a language like C Others D M Ritchie UNIX Assembler Reference Man ual B W Kernighan and L L Cherry A System for Typesetting Mathematics Computing Science Tech Rep 17 M E Lesk and B A Barres The GCOS C Library Bell Laboratories internal memorandum K Thompson and D M Ritchie Setting Up UNIX M D Mcllroy UNIX Summary D M Ritchie The UNIX I O System A D Hall The M6 Macro Processor Computing Science Tech Rep 2 J F Ossanna NROFF User s Manual _ Second Edition Bell Laboratories internal memorandum D M Ritchie and K Thompson Regenerating Sys tem Software B W Kernighan Ratfor_A Rational Fortran Bell Laboratories internal memorandum M D Mcllroy Synthetic English Speech by Rule Computin
22. e as you wish Many UNIX programs are written so that they will take their input from one or more files if file arguments are given if no arguments are given they will read from the terminal and thus can be used in pipelines The Shell We have already mentioned once or twice the mysterious shell which is in fact The shell is the program that interprets what you type as commands and arguments It also looks after translating etc into lists of filenames The shell has other capabilities too For exam ple you can start two programs with one command line by separating the commands with a semicolon the shell recognizes the semicolon and breaks the line into two commands Thus date who does both commands before returning with a You can also have more than one program run ning simultaneously if you wish For example if you are doing something time consuming like the editor script of an earlier section and you don t want to wait around for the results before starting something else you can say ed file lt script amp The ampersand at the end of a command line says start this command running then take further commands from the terminal immediately Thus the script will begin but you can do something else at the same time Of course to keep the output from interfering with what you re doing on the ter minal it would be better to have said ed file lt script gt line
23. er Now Smith types a reply also terminated by 0 This cycle repeats until someone gets tired he then signals his intent to quit with o 0 for over and out To terminate the conversation each side must type a control d character alone on a line Delete also works When the other person types his control d you will get the message EOT on your terminal If you write to someone who isn t logged in or who doesn t want to be disturbed you ll be told If the target is logged in but doesn t answer after a decent interval simply type control d On line Manual The UNIX Programmer s Manual is typically kept on line If you get stuck on something and can t find an expert to assist you you can print on your terminal some manual section that might help It s also useful for getting the most up to date information on a command To print a manual sec tion type man section name Thus to read up on the command type man who If the section in question isn t in part I of the man ual you have to give the section number as well as in man 6 chess Of course you re out of luck if you can t remember the section name II DAY TO DAY USE Creating Files _ The Editor If we have to type a paper or a letter or a pro gram how do we get the information stored in the machine Most of these tasks are done with the UNIX
24. ermore supporting software like etc are all virtually useless with Fortran programs If you want to use assembly language all heav ens forfend try the implementation language LIL which gives you many of the advantages of a high level language like decent control flow structures but still lets you get close to the machine if you really want to If your application requires you to translate a language into a set of actions or another language you are in effect building a compiler though proba bly a small one In that case you should be using the compiler compiler which helps you develop a compiler quickly V UNIX READING LIST General UNIX Programmer s Manual Ken Thompson Den nis Ritchie and a cast of thousands Lists com mands system routines and interfaces file formats and some of the maintenance procedures You can t live without this although you will probably only read section I The UNIX Time sharing System Ken Thompson Dennis Ritchie CACM July 1974 An overview of the system for people interested in operating systems Worth reading by anyone who programs Contains a remarkable number of one sentence observations on how to do things right Document Preparation A Tutorial Introduction to the UNIX Text Editor Brian Kernighan Bell Laboratories internal memorandum Weak on the more esoteric uses of the editor but still probably the easiest way to learn Typing Documents on UNIX Mik
25. f the UNIX Programmer s Manual Rather it suggests in what order to read the manual and it collects together things that are stated only indirectly in the manual There are five sections Getting Started How to log in to a UNIX how to type what to do about mistakes in typing how to log out Some of this is dependent on which UNIX you log into phone numbers for example and what terminal you use so this section must necessarily be supplemented by local information Day to day Use Things you need every day to use UNIX effectively generally useful com mands the file system Document Preparation Preparing manuscripts is one of the most common uses for UNIX This section contains advice but not extensive instructions on any of the formatting programs Writing Programs UNIX is an excellent vehicle for developing programs This section talks about some of the tools but again is not a tuto rial in any of the programming languages that UNIX provides A UNIX Reading List An annotated bibliogra phy of documents worth reading by new users I GETTING STARTED Logging In Most of the details about logging in are in the manual section called How to Get Started pages iv v in the 5th Edition Here are a couple of extra warnings You must have a UNIX login name which you can get from whoever administers your system You also need to know the phone number UNIX is capable of dealing with a variety of termina
26. fy how long lines are whether to use single or double spacing and what running titles to use on each page In general you don t have to spell out all of the possible formatting details Most of them have default values which you will get if you say nothing at all For example unless you take special precautions you ll get sin gle spaced output 65 character lines justified right margins and 58 text lines per page when you a file This is the reason that is so simple _ most of the decisions have already been made for you Some things do have to be done however If you want a document broken into paragraphs you have to tell where to add the extra blank lines This is done with the sp command this is the end of one paragraph sp This begins the next paragraph In and in and formatting commands consist of a period followed by two letters and they must appear at the beginning of a line all by themselves The sp command tells to finish printing any of the previous line that might be still unprinted then print a blank line before continuing You can have more space if you wish sp 2 asks for 2 spaces and so on If you simply want to ensure that subsequent text appears on a fresh output line you can use the command br for break instead of sp Most of the other commonly used commands are equally simple For example you can center o
27. g Science Tech Rep 14 M D McIlroy Bell Laboratories internal memo randum J F Ossanna TROFF Users Manual Bell Labora tories internal memorandum B W Kernighan TROFF Made Trivial Bell Labo ratories internal memorandum R H Morris and L L Cherry Computer Detection of Typographical Errors Computing Science Tech Rep 18 S C Johnson YACC Yet Another Compiler Com piler Bell Laboratories internal memorandum P J Plauger Programming in LIL A Tutorial Bell Laboratories internal memorandum Index amp asynchronous process 8 multiple processes 8 pattern match 5 pattern match 6 pattern match 6 lt gt redirect I O 7 gt gt file append 12 backslash 2 cat concatenate files 4 cdb C debugger 12 chdir change directory 7 chmod change protection 7 command arguments 4 command files 8 cp copy files 5 cref cross reference 11 date 2 db assembly debugger 13 delete DEL 2 diff file comparison 11 directories 7 document formatting 9 ed editor 3 editor programming 11 EOT end of file 3 eqn mathematics 11 erase character 2 file system structure 6 filenames 5 file protection 7 goto 12 grep pattern matching 11 if condition test 12 index 14 killa program 8 kill a character 2 lil high level assembler 13 login 1 logout 2 Is list file names 4 macro for formatting 10 mail 2 multi columns printing pr 5 mv
28. ily write a program that reads from its standard input and use to concatentate sev eral files into it This may not be adequate for the long run but for the early stages it s just right There are a number of supporting programs that go with C The C debugger is marginally useful for digging through the dead bodies of C programs the assembly language debugger is actually more useful most of the time but you have to know more about the machine and system to use it well The most effective debugging tool is still careful thought coupled with judiciously placed print statements You can instrument C programs and thus find out where they spend their time and what parts are worth optimising Compile the routines with the p option after the test run use to print an execu tion profile The command will give you the gross run time statistics of a program but it s not super accurate or reproducible C programs that don t depend too much on spe cial features of UNIX can be moved to the Honey well 6070 and IBM 370 systems with modest effort Read The GCOS C Library by M E Lesk and B A Barres for details Miscellany If you have to use Fortran you might consider which gives you the decent control structures and free form input that characterize C yet lets you write code that is still portable to other environ ments Bear in mind that UNIX Fortran tends to produce large and relatively slow running pro grams Furth
29. ls Ter minet 300 s Execuport TI and similar portables video terminals GSI s and even the venerable Teletype in its various forms But note UNIX will not handle IBM 2741 terminals and their deriv atives e g some Anderson Jacobsons Novar Furthermore UNIX is strongly oriented towards devices with lower case If your terminal produces only upper case e g model 33 Teletype life will be so difficult that you should look for another ter minal Be sure to set the switches appropriately on your device speed if it s variable to 30 characters per second lower case full duplex even parity and any others that local wisdom advises Establish a connection using whatever magic is needed for your terminal UNIX should type login at you If it types garbage you may be at the wrong speed push the break or interrupt key once If that fails to produce a login message consult a guru gt When you get a login message type your login name in lower case Follow it by a RETURN if the terminal has one If a password is required you will be asked for it and if possible printing will be turned off while you type it again followed by a RETURN On M37 Teletypes always use NEWLINE or LINEFEED in place of RETURN The culmination of your login efforts is a per cent sign The percent sign means that UNIX is ready to accept commands from the terminal You may also get a message of the day jus
30. ne or more lines with the ce command ce Title of Paper sp 2 causes the title to be centered then followed by two blank lines As with sp ce can be followed by a number in that case that many input lines are centered ul underlines lines and can also be followed by a number ce 2 ul 2 An Earth shaking Paper sp John Q Scientist will center and underline the two text lines Notice that the sp between them is not part of the line count You can get multiple line spacing instead of the default single spacing with the ls command Is 2 causes double spacing If you re typing things like tables you will not want the automatic filling up and justification of output lines that is done by default You can turn this off with the command nf no fill and then back on again with fi fill Thus this section is filled by default nf here lines will appear just as you typed them _ no extra spaces no moving of words fi Now go back to filling up output lines You can change the line length with Il and the left margin the indent by in These are often used together to make offset blocks of text 11 10 in 10 this text will be moved 10 spaces to the right and the lines will also be shortened 10 characters from the right The and mean to change the previous
31. nlikely example suppose you want to count the number of users on the machine every hour You could type date who wc 1 every hour and write down the numbers but that is rather primitive The next step is probably to say date who we l gt gt users which uses gt gt to append to the end of the file users We haven t mentioned gt gt before _ it s another service of the shell Now all you have to do is to put a loop around this and ensure that it s done every hour Thus place the following commands into a file say count loop date who we l gt gt users sleep 3600 goto loop The command is followed by a space and a label which you can then Notice that it s quite legal to branch backwards Now if you issue the command sh count amp the users will be counted every hour and you can go on with other things You will have to use to stop counting If you would like every hour to be a parame ter you can arrange for that too loop date who we 1 gt gt users sleep 1 goto loop 1 means the first argument when this procedure is invoked If you say sh count 60 it will count every minute A shell program can have up to nine arguments 1 through 9 The other aspect of programming is conditional testing The command can test conditions and execute commands accordingly As a simple exam pl
32. on that in a moment But remember that there are quite a few programs already written some of which have substantial power The editor can be made to do things that would normally require special programs on other sys tems For example to list the first and last lines of each of a set of files say a book you could labori ously type ede chap1 1 1p p e chap1 2 1p p etc But instead you can do the job once and for all Type ls chap gt temp to get the list of filenames into a file Then edit this file to make the necessary series of editing com mands using the global commands of and write it into script Now the command ed lt script will produce the same output as the laborious hand typing The pipe mechanism lets you fabricate quite complicated operations out of spare parts already built For example the first draft of the program was roughly cat collect the files ltr put each word on a new line delete punctuation etc sort into dictionary order uniq strip out duplicates comm list words found in text but not in dictionary Programming the Shell An option often overlooked by newcomers is that the shell is itself a programming language and since UNIX already has a host of building block programs you can sometimes avoid writing a spe cial purpose program merely by piecing together some of the building blocks with shell command files As an u
33. rted into alphabetical order automatically but other variations are possible For example if we add the optional argument t Is t lists them in the order in which they were last changed most recent first The l option gives a long listing Is 1 will produce something like rw rw rw 1 bwk 41 Sep 22 12 56 junk rw rw rw bwk 78 Sep 22 12 57 temp The date and time are of the last change to the file The 41 and 78 are the number of characters you got the same thing from bwk is the owner of the file _ the person who created it The rw rw rw tells who has permission to read and write the file in this case everyone Options can be combined Is lt would give the same thing but sorted into time order You can also name the files you re interested in and will list the information about them only More details can be found in It is generally true of UNIX programs that flag arguments like t precede filename argu ments Printing Files Now that you ve got a file of text how do you print it so people can look at it There are a host of programs that do that probably more than are needed One simple thing is to use the editor since printing is often done just before making changes anyway You can say ed junk 1 p will reply with the count of the characters in junk and then print all the lines
34. s amp which would save the output lines in a file called lines When you initiate a command with amp UNIX replies with a number called the process number which identifies the command in case you later want to stop it If you do you can say kill process number You might also read You can say command 1 command 2 command 3 amp to start these commands in the background or you can start a background pipeline with command 1 command 2 amp Just as you can tell the editor or some similar program to take its input from a file instead of from the terminal you can tell the shell to read a file to get commands Why not The shell after all is just a program albeit a clever one For instance sup pose you want to set tabs on your terminal and find out the date and who s on the system every time you log in Then you can put the three necessary commands into a file let s call it xxx and then run it with either sh Xxx or sh lt xxx This says to run the shell with the file xxx as input The effect is as if you had typed the contents of xxx on the terminal If this is to be a regular thing you can eliminate the need to type sh see and The shell has quite a few other capabilities as well some of which we ll get to in the section on programming HI DOCUMENT PREPARATION UNIX is extensively used for
35. t before the percent sign or a notification that you have mail Typing Commands Once you ve seen the percent sign you can type commands which are requests that UNIX do something Try typing date followed by RETURN You should get back some thing like Sun Sep 22 10 52 29 EDT 1974 Don t forget the RETURN after the command or nothing will happen If you think you re being ignored type a RETURN something should happen We won t show the carriage returns but they have to be there Another command you might try is which tells you everyone who is currently logged in who gives something like pip ttyf Sep 22 09 40 bwk ttyg Sep 22 09 48 mel ttyh Sep 22 09 58 The time is when the user logged in If you make a mistake typing the command name UNIX will tell you For example if you type whom you will be told whom not found Strange Terminal Behavior Sometimes you can get into a state where your terminal acts strangely For example each letter may be typed twice or the RETURN may not cause a line feed You can often fix this by logging out and logging back in Or you can read the descrip tion of the command in section I of the manual This will also tell you how to get intelligent treat ment of tab characters which are much used in UNIX if your terminal doesn t have tabs If it does have computer settable tabs the command will set the stops correctly for you
36. yourfile If your neighbor doesn t want you poking around in his files or vice versa privacy can be arranged Each file and directory can have read write execute permissions for the owner a group and everyone else to control access See and for details As a matter of observed fact most users most of the time find openness of more benefit than privacy As a final experiment with pathnames try ls bin usr bin Do some of the names look familiar When you run a program by typing its name after a the system simply looks for a file of that name It looks first in your directory where it typically doesn t find it then in bin and finally in usr bin There is nothing magic about com mands like or except that they have been collected into two places to be easy to find and administer What if you work regularly with someone else on common information in his directory You could just log in as your friend each time you want to but you can also say I want to work on his files instead of my own This is done by changing the directory that you are currently in chdir usr your friend Now when you use a filename in something like or it refers to the file in your friend s directory Changing directories doesn t affect any permissions associated with a file _ if you couldn t access a file from your own directory changing to another direc tory won t
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