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author | uqs <uqs@FreeBSD.org> | 2010-12-04 10:11:20 +0000 |
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committer | uqs <uqs@FreeBSD.org> | 2010-12-04 10:11:20 +0000 |
commit | 9242c645f81d22058934688725f1fff0bc88cb64 (patch) | |
tree | a39140e4d881fbba4f04ac77974bfbb05df9d360 /bin/csh | |
parent | 06cd6f2bc1f94f941b57ef92ed6445529822669b (diff) | |
download | FreeBSD-src-9242c645f81d22058934688725f1fff0bc88cb64.zip FreeBSD-src-9242c645f81d22058934688725f1fff0bc88cb64.tar.gz |
Move most of the remaining USD/PSD/SMM papers into share/doc
Diffstat (limited to 'bin/csh')
-rw-r--r-- | bin/csh/USD.doc/csh.1 | 1012 | ||||
-rw-r--r-- | bin/csh/USD.doc/csh.2 | 1304 | ||||
-rw-r--r-- | bin/csh/USD.doc/csh.3 | 649 | ||||
-rw-r--r-- | bin/csh/USD.doc/csh.4 | 176 | ||||
-rw-r--r-- | bin/csh/USD.doc/csh.a | 93 | ||||
-rw-r--r-- | bin/csh/USD.doc/csh.g | 1719 | ||||
-rw-r--r-- | bin/csh/USD.doc/tabs | 32 |
7 files changed, 0 insertions, 4985 deletions
diff --git a/bin/csh/USD.doc/csh.1 b/bin/csh/USD.doc/csh.1 deleted file mode 100644 index 915cb23..0000000 --- a/bin/csh/USD.doc/csh.1 +++ /dev/null @@ -1,1012 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)csh.1 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.EH 'USD:4-%''An Introduction to the C shell' -.OH 'An Introduction to the C shell''USD:4-%' -.\".RP -.TL -An Introduction to the C shell -.AU -William Joy -(revised for 4.3BSD by Mark Seiden) -.AI -Computer Science Division -.br -Department of Electrical Engineering and Computer Science -.br -University of California, Berkeley -.br -Berkeley, California 94720 -.AB -.I Csh -is a new command language interpreter for -.UX -systems. -It incorporates good features of other shells and a -.I history -mechanism similar to the -.I redo -of \s-2INTERLISP\s0. -While incorporating many features of other shells which make -writing shell programs (shell scripts) easier, -most of the features unique to -.I csh -are designed more for the interactive \s-2UNIX\s0 user. -.PP -\s-2UNIX\s0 -users who have read a general introduction to the system -will find a valuable basic explanation of the shell here. -Simple terminal interaction with -.I csh -is possible after reading just the first section of this document. -The second section describes the shell's capabilities which you can -explore after you have begun to become acquainted with the shell. -Later sections introduce features which are useful, but not necessary -for all users of the shell. -.PP -Additional information includes an appendix listing special characters of the shell -and a glossary of terms and commands introduced in this manual. -.AE -.SH -.if n .ND -Introduction -.PP -A -.I shell -is a command language interpreter. -.I Csh -is the name of one particular command interpreter on -\s-2UNIX\s0. -The primary purpose of -.I csh -is to translate command lines typed at a terminal into -system actions, such as invocation of other programs. -.I Csh -is a user program just like any you might write. -Hopefully, -.I csh -will be a very useful program for you -in interacting with the \s-2UNIX\s0 system. -.PP -In addition to this document, you will want to refer to a copy -of the \s-2UNIX\s0 User Reference Manual. -The -.I csh -documentation in section 1 of the manual provides a full description of all -features of the shell and is the definitive reference for questions -about the shell. -.PP -Many words in this document are shown in -.I italics. -These are important words; -names of commands, and words which have special meaning in discussing -the shell and \s-2UNIX\s0. -Many of the words are defined in a glossary at the end of this document. -If you don't know what is meant by a word, you should look -for it in the glossary. -.SH -Acknowledgements -.PP -Numerous people have provided good input about previous versions -of -.I csh -and aided in its debugging and in the debugging of its documentation. -I would especially like to thank Michael Ubell -who made the crucial observation that history commands could be -done well over the word structure of input text, and implemented -a prototype history mechanism in an older version of the shell. -Eric Allman has also provided a large number of useful comments on the -shell, helping to unify those concepts which are present and to identify -and eliminate useless and marginally useful features. -Mike O'Brien suggested the pathname hashing -mechanism which speeds command execution. -Jim Kulp added the job control and directory stack primitives and -added their documentation to this introduction. -.br -.bp -.NH -Terminal usage of the shell -.NH 2 -The basic notion of commands -.PP -A -.I shell -in -\s-2UNIX\s0 -acts mostly as a medium through which other -.I programs -are invoked. -While it has a set of -.I builtin -functions which it performs directly, -most commands cause execution of programs that are, in fact, -external to the shell. -The shell is thus distinguished from the command interpreters of other -systems both by the fact that it is just a user program, and by the fact -that it is used almost exclusively as a mechanism for invoking other programs. -.PP -.I Commands -in the \s-2UNIX\s0 system consist of a list of strings or -.I words -interpreted as a -.I "command name" -followed by -.I arguments. -Thus the command -.DS -mail bill -.DE -consists of two words. -The first word -.I mail -names the command to be executed, in this case the -mail program which sends messages to other users. -The shell uses the name of the command in attempting to execute it for you. -It will look in a number of -.I directories -for a file with the name -.I mail -which is expected to contain the mail program. -.PP -The rest of the words of the command are given as -.I arguments -to the command itself when it is executed. -In this case we specified also the argument -.I bill -which is interpreted by the -.I mail -program to be the name of a user to whom mail is to be sent. -In normal terminal usage we might use the -.I mail -command as follows. -.DS -% mail bill -I have a question about the csh documentation. -My document seems to be missing page 5. -Does a page five exist? - Bill -EOT -% -.DE -.PP -Here we typed a message to send to -.I bill -and ended this message with a ^D which sent an end-of-file to -the mail program. -(Here and throughout this document, the notation ``^\fIx\fR'' -is to be read ``control-\fIx\fR'' and represents the striking of the \fIx\fR -key while the control key is held down.) -The mail program -then echoed the characters `EOT' and transmitted our message. -The characters `% ' were printed before and after the mail command -by the shell to indicate that input was needed. -.PP -After typing the `% ' prompt the shell was reading command input from -our terminal. -We typed a complete command `mail bill'. -The shell then executed the -.I mail -program with argument -.I bill -and went dormant waiting for it to complete. -The mail program then read input from our terminal until we signalled -an end-of-file via typing a ^D after which the shell noticed -that mail had completed -and signaled us that it was ready to read from the terminal again by -printing another `% ' prompt. -.PP -This is the essential pattern of all interaction with \s-2UNIX\s0 -through the shell. -A complete command is typed at the terminal, the shell executes -the command and when this execution completes, it prompts for a new command. -If you run the editor for an hour, the shell will patiently wait for -you to finish editing and obediently prompt you again whenever you finish -editing. -.PP -An example of a useful command you can execute now is the -.I tset -command, which sets the default -.I erase -and -.I kill -characters on your terminal \- the erase character erases the last -character you typed and the kill character erases the entire line you -have entered so far. -By default, the erase character is the delete key (equivalent to `^?') -and the kill character is `^U'. Some people prefer to make the erase character -the backspace key (equivalent to `^H'). -You can make this be true by typing -.DS -tset \-e -.DE -which tells the program -.I tset -to set the erase character to tset's default setting for this character -(a backspace). -.NH 2 -Flag arguments -.PP -A useful notion in \s-2UNIX\s0 is that of a -.I flag -argument. -While many arguments to commands specify file names or user names, -some arguments rather specify an optional capability of the command -which you wish to invoke. -By convention, such arguments begin with the character `\-' (hyphen). -Thus the command -.DS -ls -.DE -will produce a list of the files in the current -.I "working directory" . -The option -.I \-s -is the size option, and -.DS -ls \-s -.DE -causes -.I ls -to also give, for each file the size of the file in blocks of 512 -characters. -The manual section for each command in the \s-2UNIX\s0 reference manual -gives the available options for each command. -The -.I ls -command has a large number of useful and interesting options. -Most other commands have either no options or only one or two options. -It is hard to remember options of commands which are not used very -frequently, so most \s-2UNIX\s0 utilities perform only one or two functions -rather than having a large number of hard to remember options. -.NH 2 -Output to files -.PP -Commands that normally read input or write output on the terminal -can also be executed with this input and/or output done to -a file. -.PP -Thus suppose we wish to save the current date in a file called `now'. -The command -.DS -date -.DE -will print the current date on our terminal. -This is because our terminal is the default -.I "standard output" -for the date command and the date command prints the date on its -standard output. -The shell lets us -.I redirect -the -.I "standard output" -of a command through a -notation using the -.I metacharacter -`>' and the name of the file where output is to be placed. -Thus the command -.DS -date > now -.DE -runs the -.I date -command such that its standard output is -the file `now' rather than the terminal. -Thus this command places the current date and time into the file `now'. -It is important to know that the -.I date -command was unaware that its output was going to a file rather than -to the terminal. -The shell performed this -.I redirection -before the command began executing. -.PP -One other thing to note here is that the file `now' -need not have existed before the -.I date -command was executed; the shell would have created the file if it did -not exist. -And if the file did exist? -If it had existed previously these previous contents would have been discarded! -A shell option -.I noclobber -exists to prevent this from happening accidentally; -it is discussed in section 2.2. -.PP -The system normally keeps files which you create with `>' and all other files. -Thus the default is for files to be permanent. If you wish to create a file -which will be removed automatically, you can begin its name with a `#' -character, this `scratch' character denotes the fact that the file will -be a scratch file.* -.FS -*Note that if your erase character is a `#', you will have to precede the -`#' with a `\e'. The fact that the `#' character is the old (pre-\s-2CRT\s0) -standard erase character means that it seldom appears in a file name, and -allows this convention to be used for scratch files. If you are using a -\s-2CRT\s0, your erase character should be a ^H, as we demonstrated -in section 1.1 how this could be set up. -.FE -The system will remove such files after a couple of days, -or sooner if file space becomes very tight. -Thus, in running the -.I date -command above, we don't really want to save the output forever, so we -would more likely do -.DS -date > #now -.DE -.NH 2 -Metacharacters in the shell -.PP -The shell has a large number of -special characters (like `>') -which indicate special functions. -We say that these notations have -.I syntactic -and -.I semantic -meaning to the shell. -In general, most characters which are neither letters nor digits -have special meaning to the shell. -We shall shortly learn a means of -.I quotation -which allows us to use -.I metacharacters -without the shell treating them in any special way. -.PP -Metacharacters normally have effect only when the shell is reading -our input. -We need not worry about placing shell metacharacters in a letter -we are sending via -.I mail, -or when we are typing in text or data to some other program. -Note that the shell is only reading input when it has prompted with -`% ' (although we can type our input even before it prompts). -.NH 2 -Input from files; pipelines -.PP -We learned above how to -.I redirect -the -.I "standard output" -of a command -to a file. -It is also possible to redirect the -.I "standard input" -of a command from a file. -This is not often necessary since most commands will read from -a file whose name is given as an argument. -We can give the command -.DS -sort < data -.DE -to run the -.I sort -command with standard input, where the command normally -reads its input, from the file -`data'. -We would more likely say -.DS -sort data -.DE -letting the -.I sort -command open the file -`data' -for input itself since this is less to type. -.PP -We should note that if we just typed -.DS -sort -.DE -then the sort program would sort lines from its -.I "standard input." -Since we did not -.I redirect -the standard input, it would sort lines as we typed them on the terminal -until we typed a ^D to indicate an end-of-file. -.PP -A most useful capability is the ability to combine the standard output -of one command with the standard input of another, i.e. to run the -commands in a sequence known as a -.I pipeline. -For instance the command -.DS -ls \-s -.DE -normally produces a list of the files in our directory with the size -of each in blocks of 512 characters. -If we are interested in learning which of our files is largest we -may wish to have this sorted by size rather than by name, which is -the default way in which -.I ls -sorts. -We could look at the many options of -.I ls -to see if there was an option to do this but would eventually discover -that there is not. -Instead we can use a couple of simple options of the -.I sort -command, combining it with -.I ls -to get what we want. -.PP -The -.I \-n -option of sort specifies a numeric sort rather than an alphabetic sort. -Thus -.DS -ls \-s | sort \-n -.DE -specifies that the output of the -.I ls -command run with the option -.I \-s -is to be -.I piped -to the command -.I sort -run with the numeric sort option. -This would give us a sorted list of our files by size, but with the -smallest first. -We could then use the -.I \-r -reverse sort option and the -.I head -command in combination with the previous command doing -.DS -ls \-s | sort \-n \-r | head \-5 -.DE -Here we have taken a list of our files sorted alphabetically, -each with the size in blocks. -We have run this to the standard input of the -.I sort -command asking it to sort numerically in reverse order (largest first). -This output has then been run into the command -.I head -which gives us the first few lines. -In this case we have asked -.I head -for the first 5 lines. -Thus this command gives us the names and sizes of our 5 largest files. -.PP -The notation introduced above is called the -.I pipe -mechanism. -Commands separated by `\||\|' characters are connected together by the -shell and the standard output of each is run into the standard input of the -next. -The leftmost command in a pipeline will normally take its standard -input from the terminal and the rightmost will place its standard -output on the terminal. -Other examples of pipelines will be given later when we discuss the -history mechanism; -one important use of pipes which is illustrated there is in the -routing of information to the line printer. -.NH 2 -Filenames -.PP -Many commands to be executed will need the names of files as arguments. -\s-2UNIX\s0 -.I pathnames -consist of a number of -.I components -separated by `/'. -Each component except the last names a directory in which the next -component resides, in effect specifying the -.I path -of directories to follow to reach the file. -Thus the pathname -.DS -/etc/motd -.DE -specifies a file in the directory -`etc' -which is a subdirectory of the -.I root -directory `/'. -Within this directory the file named is `motd' which stands -for `message of the day'. -A -.I pathname -that begins with a slash is said to be an -.I absolute -pathname since it is specified from the absolute top of the entire -directory hierarchy of the system (the -.I root ). -.I Pathnames -which do not begin with `/' are interpreted as starting in the current -.I "working directory" , -which is, by default, your -.I home -directory and can be changed dynamically by the -.I cd -change directory command. -Such pathnames are said to be -.I relative -to the working directory since they are found by starting -in the working directory and descending to lower levels of directories -for each -.I component -of the pathname. If the pathname contains no slashes at all then the -file is contained in the working directory itself and the pathname is merely -the name of the file in this directory. -Absolute pathnames have no relation -to the working directory. -.PP -Most filenames consist of a number of alphanumeric characters and -`.'s (periods). -In fact, all printing characters except `/' (slash) may appear in filenames. -It is inconvenient to have most non-alphabetic characters in filenames -because many of these have special meaning to the shell. -The character `.' (period) is not a shell-metacharacter and is often used -to separate the -.I extension -of a file name from the base of the name. -Thus -.DS -prog.c prog.o prog.errs prog.output -.DE -are four related files. -They share a -.I base -portion of a name -(a base portion being that part of the name that is left when a trailing -`.' and following characters which are not `.' are stripped off). -The file -`prog.c' -might be the source for a C program, -the file `prog.o' the corresponding object file, -the file -`prog.errs' the errors resulting from a compilation of the program -and the file -`prog.output' the output of a run of the program. -.PP -If we wished to refer to all four of these files in a command, we could -use the notation -.DS -prog.* -.DE -This expression is expanded by the shell, before the command to which it is -an argument is executed, into a list of names which begin with `prog.'. -The character `*' here matches any sequence (including the empty sequence) -of characters in a file name. -The names which match are alphabetically sorted and placed in the -.I "argument list" -of the command. -Thus the command -.DS -echo prog.* -.DE -will echo the names -.DS -prog.c prog.errs prog.o prog.output -.DE -Note that the names are in sorted order here, and a different -order than we listed them above. -The -.I echo -command receives four words as arguments, even though we only typed -one word as an argument directly. -The four words were generated by -.I "filename expansion" -of the one input word. -.PP -Other notations for -.I "filename expansion" -are also available. -The character `?' matches any single character in a filename. -Thus -.DS -echo ? \|?? \|??? -.DE -will echo a line of filenames; first those with one character names, -then those with two character names, and finally those with three -character names. -The names of each length will be independently sorted. -.PP -Another mechanism consists of a sequence of characters between `[' and `]'. -This metasequence matches any single character from the enclosed set. -Thus -.DS -prog.[co] -.DE -will match -.DS -prog.c prog.o -.DE -in the example above. -We can also place two characters around a `\-' in this notation to denote -a range. -Thus -.DS -chap.[1\-5] -.DE -might match files -.DS -chap.1 chap.2 chap.3 chap.4 chap.5 -.DE -if they existed. -This is shorthand for -.DS -chap.[12345] -.DE -and otherwise equivalent. -.PP -An important point to note is that if a list of argument words to -a command (an -.I "argument list)" -contains filename expansion syntax, and if this filename expansion syntax -fails to match any existing file names, then the shell considers this -to be an error and prints a diagnostic -.DS -No match. -.DE -and does not execute the command. -.PP -Another very important point is that files with the character `.' at the -beginning are treated specially. -Neither `*' or `?' or the `[' `]' mechanism will match it. -This prevents accidental matching of the filenames `.' and `..' -in the working directory which have special meaning to the system, -as well as other files such as -.I \&.cshrc -which are not normally -visible. -We will discuss the special role of the file -.I \&.cshrc -later. -.PP -Another filename expansion mechanism gives access to the pathname of -the -.I home -directory of other users. -This notation consists of the character `~' (tilde) followed by another user's -login name. -For instance the word `~bill' would map to the pathname `/usr/bill' -if the home directory for `bill' was `/usr/bill'. -Since, on large systems, users may have login directories scattered over -many different disk volumes with different prefix directory names, -this notation provides a convenient way of accessing the files -of other users. -.PP -A special case of this notation consists of a `~' alone, e.g. `~/mbox'. -This notation is expanded by the shell into the file `mbox' in your -.I home -directory, i.e. into `/usr/bill/mbox' for me on Ernie Co-vax, the UCB -Computer Science Department VAX machine, where this document was prepared. -This can be very useful if you have used -.I cd -to change to another directory and have found a file you wish to -copy using -.I cp. -If I give the command -.DS -cp thatfile ~ -.DE -the shell will expand this command to -.DS -cp thatfile /usr/bill -.DE -since my home directory is /usr/bill. -.PP -There also exists a mechanism using the characters `{' and `}' for -abbreviating a set of words which have common parts but cannot -be abbreviated by the above mechanisms because they are not files, -are the names of files which do not yet exist, -are not thus conveniently described. -This mechanism will be described much later, -in section 4.2, -as it is used less frequently. -.NH 2 -Quotation -.PP -We have already seen a number of metacharacters used by the shell. -These metacharacters pose a problem in that we cannot use them directly -as parts of words. -Thus the command -.DS -echo * -.DE -will not echo the character `*'. -It will either echo a sorted list of filenames in the -current -.I "working directory," -or print the message `No match' if there are -no files in the working directory. -.PP -The recommended mechanism for placing characters which are neither numbers, -digits, `/', `.' or `\-' in an argument word to a command is to enclose -it with single quotation characters `\'', i.e. -.DS -echo \'*\' -.DE -There is one special character `!' which is used by the -.I history -mechanism of the shell and which cannot be -.I escaped -by placing it within `\'' characters. -It and the character `\'' itself can be preceded by a single `\e' -to prevent their special meaning. -Thus -.DS -echo \e\'\e! -.DE -prints -.DS -\'! -.DE -These two mechanisms suffice to place any printing character into a word -which is an argument to a shell command. They can be combined, as in -.DS -echo \e\'\'*\' -.DE -which prints -.DS -\'* -.DE -since the first `\e' escaped the first `\'' and the `*' was enclosed -between `\'' characters. -.NH 2 -Terminating commands -.PP -When you are executing a command and the shell is -waiting for it to complete there are several ways -to force it to stop. -For instance if you type the command -.DS -cat /etc/passwd -.DE -the system will print a copy of a list of all users of the system -on your terminal. -This is likely to continue for several minutes unless you stop it. -You can send an -\s-2INTERRUPT\s0 -.I signal -to the -.I cat -command by typing ^C on your terminal.* -.FS -*On some older Unix systems the \s-2DEL\s0 or \s-2RUBOUT\s0 key -has the same effect. "stty all" will tell you the INTR key value. -.FE -Since -.I cat -does not take any precautions to avoid or otherwise handle this signal -the -\s-2INTERRUPT\s0 -will cause it to terminate. -The shell notices that -.I cat -has terminated and prompts you again with `% '. -If you hit \s-2INTERRUPT\s0 again, the shell will just -repeat its prompt since it handles \s-2INTERRUPT\s0 signals -and chooses to continue to execute commands rather than terminating -like -.I cat -did, which would have the effect of logging you out. -.PP -Another way in which many programs terminate is when they get an end-of-file -from their standard input. -Thus the -.I mail -program in the first example above was terminated when we typed a ^D -which generates an end-of-file from the standard input. -The shell also terminates when it gets an end-of-file printing `logout'; -\s-2UNIX\s0 then logs you off the system. -Since this means that typing too many ^D's can accidentally log us off, -the shell has a mechanism for preventing this. -This -.I ignoreeof -option will be discussed in section 2.2. -.PP -If a command has its standard input redirected from a file, then it will -normally terminate when it reaches the end of this file. -Thus if we execute -.DS -mail bill < prepared.text -.DE -the mail command will terminate without our typing a ^D. -This is because it read to the end-of-file of our file -`prepared.text' in which we placed a message for `bill' with an editor program. -We could also have done -.DS -cat prepared.text \||\| mail bill -.DE -since the -.I cat -command would then have written the text through the pipe to the -standard input of the mail command. -When the -.I cat -command completed it would have terminated, -closing down the pipeline -and the -.I mail -command would have received an end-of-file from it and terminated. -Using a pipe here is more complicated than redirecting input -so we would more likely use the first form. -These commands could also have been stopped by sending an \s-2INTERRUPT\s0. -.PP -Another possibility for stopping a command is to suspend its execution -temporarily, with the possibility of continuing execution later. This is -done by sending a \s-2STOP\s0 signal via typing a ^Z. -This signal causes all commands running on the terminal -(usually one but more if a pipeline is executing) to become suspended. -The shell notices that the command(s) have been suspended, types -`Stopped' and then prompts for a new command. -The previously executing command has been suspended, but otherwise -unaffected by the \s-2STOP\s0 signal. Any other commands can be executed -while the original command remains suspended. The suspended command can -be continued using the -.I fg -command with no arguments. The shell will then retype the command -to remind you which command is being continued, and cause the command -to resume execution. Unless any input files in use by the suspended -command have been changed in the meantime, the suspension has no effect -whatsoever on the execution of the command. This feature can be very useful -during editing, when you need to look at another file before continuing. -An -example of command suspension follows. -.DS -% mail harold -Someone just copied a big file into my directory and its name is -^Z -Stopped -% ls -funnyfile -prog.c -prog.o -% jobs -.ta 1.75i -[1] + Stopped mail harold -% fg -mail harold -funnyfile. Do you know who did it? -EOT -% -.so tabs -.DE -In this example someone was sending a message to Harold and forgot the -name of the file he wanted to mention. The mail command was suspended -by typing ^Z. When the shell noticed that the mail program was -suspended, it typed `Stopped' and prompted for a new command. Then the -.I ls -command was typed to find out the name of the file. The -.I jobs -command was run to find out which command was suspended. -At this time the -.I fg -command was typed to continue execution of the mail program. Input -to the mail program was then continued and ended with a ^D -which indicated the end of the message at which time the mail -program typed EOT. The -.I jobs -command will show which commands are suspended. -The ^Z should only be typed at the beginning of a line since -everything typed on the current line is discarded when a signal is sent -from the keyboard. This also happens on \s-2INTERRUPT\s0, and \s-2QUIT\s0 -signals. More information on -suspending jobs and controlling them is given in -section 2.6. -.PP -If you write or run programs which are not fully debugged then it may -be necessary to stop them somewhat ungracefully. -This can be done by sending them a \s-2QUIT\s0 -signal, sent by typing a ^\e. -This will usually provoke the shell to produce a message like: -.DS -Quit (Core dumped) -.DE -indicating that a file -`core' has been created containing information about the running program's -state when it terminated due to the \s-2QUIT\s0 signal. -You can examine this file yourself, or forward information to the -maintainer of the program telling him/her where the -.I "core file" -is. -.PP -If you run background commands (as explained in section 2.6) then these -commands will ignore \s-2INTERRUPT\s0 and \s-2QUIT\s0 signals at the -terminal. To stop them you must use the -.I kill -command. See section 2.6 for an example. -.PP -If you want to examine the output of a command without having it move -off the screen as the output of the -.DS -cat /etc/passwd -.DE -command will, you can use the command -.DS -more /etc/passwd -.DE -The -.I more -program pauses after each complete screenful and types `\-\-More\-\-' -at which point you can hit a space to get another screenful, a return -to get another line, a `?' to get some help on other commands, or a `q' to end the -.I more -program. You can also use more as a filter, i.e. -.DS -cat /etc/passwd | more -.DE -works just like the more simple more command above. -.PP -For stopping output of commands not involving -.I more -you can use the -^S key to stop the typeout. The typeout will resume when you -hit ^Q or any other key, but ^Q is normally used because -it only restarts the output and does not become input to the program -which is running. This works well on low-speed terminals, but at 9600 -baud it is hard to type ^S and ^Q fast enough to paginate -the output nicely, and a program like -.I more -is usually used. -.PP -An additional possibility is to use the ^O flush output -character; when this character is typed, all output from the current -command is thrown away (quickly) until the next input read occurs -or until the next shell prompt. This can be used to allow a command -to complete without having to suffer through the output on a slow -terminal; ^O is a toggle, so flushing can be turned off by -typing ^O again while output is being flushed. -.NH 2 -What now? -.PP -We have so far seen a number of mechanisms of the shell and learned a lot -about the way in which it operates. -The remaining sections will go yet further into the internals of the -shell, but you will surely want to try using the -shell before you go any further. -To try it you can log in to \s-2UNIX\s0 and type the following -command to the system: -.DS -chsh myname /bin/csh -.DE -Here `myname' should be replaced by the name you typed to -the system prompt of `login:' to get onto the system. -Thus I would use `chsh bill /bin/csh'. -.B -You only have to do this once; it takes effect at next login. -.R -You are now ready to try using -.I csh. -.PP -Before you do the `chsh' command, the shell you are using when -you log into the system is `/bin/sh'. -In fact, much of the above discussion is applicable to `/bin/sh'. -The next section will introduce many features particular to -.I csh -so you should change your shell to -.I csh -before you begin reading it. -.bp diff --git a/bin/csh/USD.doc/csh.2 b/bin/csh/USD.doc/csh.2 deleted file mode 100644 index 5fbf43c..0000000 --- a/bin/csh/USD.doc/csh.2 +++ /dev/null @@ -1,1304 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)csh.2 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.nr H1 1 -.NH -Details on the shell for terminal users -.NH 2 -Shell startup and termination -.PP -When you login, the shell is started by the system in your -.I home -directory and begins by reading commands from a file -.I \&.cshrc -in this directory. -All shells which you may start during your terminal session will -read from this file. -We will later see what kinds of commands are usefully placed there. -For now we need not have this file and the shell does not complain about -its absence. -.PP -A -.I "login shell" , -executed after you login to the system, -will, after it reads commands from -.I \&.cshrc, -read commands from a file -.I \&.login -also in your home directory. -This file contains commands which you wish to do each time you login -to the \s-2UNIX\s0 system. -My -.I \&.login -file looks something like: -.DS -set ignoreeof -set mail=(/usr/spool/mail/bill) -echo "${prompt}users" ; users -alias ts \e - \'set noglob ; eval \`tset \-s \-m dialup:c100rv4pna \-m plugboard:?hp2621nl \!*\`\'; -ts; stty intr ^C kill ^U crt -set time=15 history=10 -msgs \-f -if (\-e $mail) then - echo "${prompt}mail" - mail -endif -.DE -.PP -This file contains several commands to be executed by \s-2UNIX\s0 -each time I login. -The first is a -.I set -command which is interpreted directly by the shell. It sets the shell -variable -.I ignoreeof -which causes the shell to not log me off if I hit ^D. Rather, -I use the -.I logout -command to log off of the system. -By setting the -.I mail -variable, I ask the shell to watch for incoming mail to me. Every 5 minutes -the shell looks for this file and tells me if more mail has arrived there. -An alternative to this is to put the command -.DS -biff y -.DE -in place of this -.I set; -this will cause me to be notified immediately when mail arrives, and to -be shown the first few lines of the new message. -.PP -Next I set the shell variable `time' to `15' causing the shell to automatically -print out statistics lines for commands which execute for at least 15 seconds -of \s-2CPU\s+2 time. The variable `history' is set to 10 indicating that -I want the shell to remember the last 10 commands I type in its -.I "history list" , -(described later). -.PP -I create an -.I alias -``ts'' which executes a -\fItset\fR\|(1) command setting up the modes of the terminal. -The parameters to -.I tset -indicate the kinds of terminal which I usually use when not on a hardwired -port. I then execute ``ts'' and also use the -.I stty -command to change the interrupt character to ^C and the line kill -character to ^U. -.PP -I then run the `msgs' program, which provides me with any -system messages which I have not seen before; the `\-f' option here prevents -it from telling me anything if there are no new messages. -Finally, if my mailbox file exists, then I run the `mail' program to -process my mail. -.PP -When the `mail' and `msgs' programs finish, the shell will finish -processing my -.I \&.login -file and begin reading commands from the terminal, prompting for each with -`% '. -When I log off (by giving the -.I logout -command) the shell -will print `logout' and execute commands from the file `.logout' -if it exists in my home directory. -After that the shell will terminate and \s-2UNIX\s0 will log -me off the system. -If the system is not going down, I will receive a new login message. -In any case, after the `logout' message the shell is committed to terminating -and will take no further input from my terminal. -.NH 2 -Shell variables -.PP -The shell maintains a set of -.I variables. -We saw above the variables -.I history -and -.I time -which had values `10' and `15'. -In fact, each shell variable has as value an array of -zero or more -.I strings. -Shell variables may be assigned values by the set command. It has -several forms, the most useful of which was given above and is -.DS -set name=value -.DE -.PP -Shell variables may be used to store values which are to -be used in commands later through a substitution mechanism. -The shell variables most commonly referenced are, however, those which the -shell itself refers to. -By changing the values of these variables one can directly affect the -behavior of the shell. -.PP -One of the most important variables is the variable -.I path. -This variable contains a sequence of directory names where the shell -searches for commands. -The -.I set -command with no arguments -shows the value of all variables currently defined (we usually say -.I set) -in the shell. -The default value for path will be shown by -.I set -to be -.DS -% set -.ta .75i -argv () -cwd /usr/bill -home /usr/bill -path (. /usr/ucb /bin /usr/bin) -prompt % -shell /bin/csh -status 0 -term c100rv4pna -user bill -% -.so tabs -.DE -This output indicates that the variable path points to the current -directory `.' and then `/usr/ucb', `/bin' and `/usr/bin'. -Commands which you may write might be in `.' (usually one of -your directories). -Commands developed at Berkeley, live in `/usr/ucb' -while commands developed at Bell Laboratories live in `/bin' and `/usr/bin'. -.PP -A number of locally developed programs on the system live in the directory -`/usr/local'. -If we wish that all shells which we invoke to have -access to these new programs we can place the command -.DS -set path=(. /usr/ucb /bin /usr/bin /usr/local) -.DE -in our file -.I \&.cshrc -in our home directory. -Try doing this and then logging out and back in and do -.DS -set -.DE -again to see that the value assigned to -.I path -has changed. -.FS \(dg -Another directory that might interest you is /usr/new, which contains -many useful user-contributed programs provided with Berkeley Unix. -.FE -.PP -One thing you should be aware of is that the shell examines each directory -which you insert into your path and determines which commands are contained -there. Except for the current directory `.', which the shell treats specially, -this means that if commands are added to a directory in your search path after -you have started the shell, they will not necessarily be found by the shell. -If you wish to use a command which has been added in this way, you should -give the command -.DS -rehash -.DE -to the shell, which will cause it to recompute its internal table of command -locations, so that it will find the newly added command. -Since the shell has to look in the current directory `.' on each command, -placing it at the end of the path specification usually works equivalently -and reduces overhead. -.PP -Other useful built in variables are the variable -.I home -which shows your home directory, -.I cwd -which contains your current working directory, -the variable -.I ignoreeof -which can be set in your -.I \&.login -file to tell the shell not to exit when it receives an end-of-file from -a terminal (as described above). -The variable `ignoreeof' -is one of several variables which the shell does not care about the -value of, only whether they are -.I set -or -.I unset. -Thus to set this variable you simply do -.DS -set ignoreeof -.DE -and to unset it do -.DS -unset ignoreeof -.DE -These give the variable `ignoreeof' no value, but none is desired or required. -.PP -Finally, some other built-in shell variables of use are the -variables -.I noclobber -and -.I mail. -The metasyntax -.DS -> filename -.DE -which redirects the standard output of a command -will overwrite and destroy the previous contents of the named file. -In this way you may accidentally overwrite a file which is valuable. -If you would prefer that the shell not overwrite files in this -way you can -.DS -set noclobber -.DE -in your -.I \&.login -file. -Then trying to do -.DS -date > now -.DE -would cause a diagnostic if `now' existed already. -You could type -.DS -date >! now -.DE -if you really wanted to overwrite the contents of `now'. -The `>!' is a special metasyntax indicating that clobbering the -file is ok.\(dg -.FS -\(dgThe space between the `!' and the word `now' is critical here, as `!now' -would be an invocation of the -.I history -mechanism, and have a totally different effect. -.FE -.NH 2 -The shell's history list -.PP -The shell can maintain a -.I "history list" -into which it places the words -of previous commands. -It is possible to use a notation to reuse commands or words -from commands in forming new commands. -This mechanism can be used to repeat previous commands or to -correct minor typing mistakes in commands. -.PP -The following figure gives a sample session involving typical usage of the -history mechanism of the shell. -.KF -.DS -% cat bug.c -main() - -{ - printf("hello); -} -% cc !$ -cc bug.c -"bug.c", line 4: newline in string or char constant -"bug.c", line 5: syntax error -% ed !$ -ed bug.c -29 -4s/);/"&/p - printf("hello"); -w -30 -q -% !c -cc bug.c -% a.out -hello% !e -ed bug.c -30 -4s/lo/lo\e\en/p - printf("hello\en"); -w -32 -q -% !c \-o bug -cc bug.c \-o bug -% size a.out bug -a.out: 2784+364+1028 = 4176b = 0x1050b -bug: 2784+364+1028 = 4176b = 0x1050b -% ls \-l !* -ls \-l a.out bug -\(mirwxr\(mixr\(mix 1 bill 3932 Dec 19 09:41 a.out -\(mirwxr\(mixr\(mix 1 bill 3932 Dec 19 09:42 bug -% bug -hello -% num bug.c | spp -spp: Command not found. -% ^spp^ssp -num bug.c | ssp - 1 main() - 3 { - 4 printf("hello\en"); - 5 } -% !! | lpr -num bug.c | ssp | lpr -% -.DE -.KE -In this example we have a very simple C program which has a bug (or two) -in it in the file `bug.c', which we `cat' out on our terminal. We then -try to run the C compiler on it, referring to the file again as `!$', -meaning the last argument to the previous command. Here the `!' is the -history mechanism invocation metacharacter, and the `$' stands for the last -argument, by analogy to `$' in the editor which stands for the end of the line. -The shell echoed the command, as it would have been typed without use of -the history mechanism, and then executed it. -The compilation yielded error diagnostics so we now run the editor on the -file we were trying to compile, fix the bug, and run the C compiler again, -this time referring to this command simply as `!c', which repeats the last -command which started with the letter `c'. If there were other -commands starting with `c' done recently we could have said `!cc' or even -`!cc:p' which would have printed the last command starting with `cc' -without executing it. -.PP -After this recompilation, we ran the resulting `a.out' file, and then -noting that there still was a bug, ran the editor again. After fixing -the program we ran the C compiler again, but tacked onto the command -an extra `\-o bug' telling the compiler to place the resultant binary in -the file `bug' rather than `a.out'. In general, the history mechanisms -may be used anywhere in the formation of new commands and other characters -may be placed before and after the substituted commands. -.PP -We then ran the `size' command to see how large the binary program images -we have created were, and then an `ls \-l' command with the same argument -list, denoting the argument list `\!*'. -Finally we ran the program `bug' to see that its output is indeed correct. -.PP -To make a numbered listing of the program we ran the `num' command on the file `bug.c'. -In order to compress out blank lines in the output of `num' we ran the -output through the filter `ssp', but misspelled it as spp. To correct this -we used a shell substitute, placing the old text and new text between `^' -characters. This is similar to the substitute command in the editor. -Finally, we repeated the same command with `!!', but sent its output to the -line printer. -.PP -There are other mechanisms available for repeating commands. The -.I history -command prints out a number of previous commands with numbers by which -they can be referenced. There is a way to refer to a previous command -by searching for a string which appeared in it, and there are other, -less useful, ways to select arguments to include in a new command. -A complete description of all these mechanisms -is given in the C shell manual pages in the \s-2UNIX\s0 Programmer's Manual. -.NH 2 -Aliases -.PP -The shell has an -.I alias -mechanism which can be used to make transformations on input commands. -This mechanism can be used to simplify the commands you type, -to supply default arguments to commands, -or to perform transformations on commands and their arguments. -The alias facility is similar to a macro facility. -Some of the features obtained by aliasing can be obtained also -using shell command files, but these take place in another instance -of the shell and cannot directly affect the current shells environment -or involve commands such as -.I cd -which must be done in the current shell. -.PP -As an example, suppose that there is a new version of the mail program -on the system called `newmail' -you wish to use, rather than the standard mail program which is called -`mail'. -If you place the shell command -.DS -alias mail newmail -.DE -in your -.I \&.cshrc -file, the shell will transform an input line of the form -.DS -mail bill -.DE -into a call on `newmail'. -More generally, suppose we wish the command `ls' to always show -sizes of files, that is to always do `\-s'. -We can do -.DS -alias ls ls \-s -.DE -or even -.DS -alias dir ls \-s -.DE -creating a new command syntax `dir' -which does an `ls \-s'. -If we say -.DS -dir ~bill -.DE -then the shell will translate this to -.DS -ls \-s /mnt/bill -.DE -.PP -Thus the -.I alias -mechanism can be used to provide short names for commands, -to provide default arguments, -and to define new short commands in terms of other commands. -It is also possible to define aliases which contain multiple -commands or pipelines, showing where the arguments to the original -command are to be substituted using the facilities of the -history mechanism. -Thus the definition -.DS -alias cd \'cd \e!* ; ls \' -.DE -would do an -.I ls -command after each change directory -.I cd -command. -We enclosed the entire alias definition in `\'' characters to prevent -most substitutions from occurring and the character `;' from being -recognized as a metacharacter. -The `!' here is escaped with a `\e' to prevent it from being interpreted -when the alias command is typed in. -The `\e!*' here substitutes the entire argument list to the pre-aliasing -.I cd -command, without giving an error if there were no arguments. -The `;' separating commands is used here -to indicate that one command is to be done and then the next. -Similarly the definition -.DS -alias whois \'grep \e!^ /etc/passwd\' -.DE -defines a command which looks up its first argument in the password file. -.PP -.B Warning: -The shell currently reads the -.I \&.cshrc -file each time it starts up. If you place a large number of commands -there, shells will tend to start slowly. A mechanism for saving the shell -environment after reading the \fI\&.cshrc\fR file and quickly restoring it is -under development, but for now you should try to limit the number of -aliases you have to a reasonable number... 10 or 15 is reasonable, -50 or 60 will cause a noticeable delay in starting up shells, and make -the system seem sluggish when you execute commands from within the editor -and other programs. -.NH 2 -More redirection; >> and >& -.PP -There are a few more notations useful to the terminal user -which have not been introduced yet. -.PP -In addition to the standard output, commands also have a -.I "diagnostic output" -which is normally directed to the terminal even when the standard output -is redirected to a file or a pipe. -It is occasionally desirable to direct the diagnostic output along with -the standard output. -For instance if you want to redirect the output of a long running command -into a file and wish to have a record of any error diagnostic it produces -you can do -.DS -command >& file -.DE -The `>&' here tells the shell to route both the diagnostic output and the -standard output into `file'. -Similarly you can give the command -.DS -command |\|& lpr -.DE -to route both standard and diagnostic output through the pipe -to the line printer daemon -.I lpr.\(dd -.FS -\(dd A command of the form -.br -.ti +5 -command >&! file -.br -exists, and is used when -.I noclobber -is set and -.I file -already exists. -.FE -.PP -Finally, it is possible to use the form -.DS -command >> file -.DE -to place output at the end of an existing file.\(dg -.FS -\(dg If -.I noclobber -is set, then an error will result if -.I file -does not exist, otherwise the shell will create -.I file -if it doesn't exist. -A form -.br -.ti +5 -command >>! file -.br -makes it not be an error for file to not exist when -.I noclobber -is set. -.FE -.NH 2 -Jobs; Background, Foreground, or Suspended -.PP -When one or more commands -are typed together as a pipeline or as a sequence of commands separated by -semicolons, a single -.I job -is created by the shell consisting of these commands together as a unit. -Single commands without pipes or semicolons create the simplest jobs. -Usually, every line typed to the shell creates a job. -Some lines that create jobs (one per line) are -.DS -sort < data -ls \-s | sort \-n | head \-5 -mail harold -.DE -.PP -If the metacharacter `&' is typed -at the end of the commands, then the job is started as a -.I background -job. This means that the shell does not wait for it to complete but -immediately prompts and is ready for another command. The job runs -.I "in the background" -at the same time that normal jobs, called -.I foreground -jobs, continue to be read and executed by the shell one at a time. -Thus -.DS -du > usage & -.DE -would run the -.I du -program, which reports on the disk usage of your working directory (as well as -any directories below it), put the output into the file `usage' and return -immediately with a prompt for the next command without out waiting for -.I du -to finish. The -.I du -program would continue executing in the background -until it finished, even though you can type and execute more commands in the -mean time. -When a background -job terminates, a message is typed by the shell just before the next prompt -telling you that the job has completed. -In the following example the -.I du -job finishes sometime during the -execution of the -.I mail -command and its completion is reported just before -the prompt after the -.I mail -job is finished. -.DS -% du > usage & -[1] 503 -% mail bill -How do you know when a background job is finished? -EOT -.ta 1.75i -[1] \- Done du > usage -% -.so tabs -.DE -If the job did not terminate normally the `Done' message might say -something else like `Killed'. -If you want the -terminations of background jobs to be reported at the time they occur -(possibly interrupting the output of other foreground jobs), you can set -the -.I notify -variable. In the previous example this would mean that the -`Done' message might have come right in the middle of the message to -Bill. -Background jobs are unaffected by any signals from the keyboard like -the \s-2STOP\s0, \s-2INTERRUPT\s0, or \s-2QUIT\s0 signals mentioned earlier. -.PP -Jobs are recorded in a table inside the shell until they terminate. -In this table, the shell remembers the command names, arguments and the -.I "process numbers" -of all commands in the job as well as the working directory where the job was -started. -Each job in the table is either running -.I "in the foreground" -with the shell waiting for it to terminate, running -.I "in the background," -or -.I suspended. -Only one job can be running in the foreground at one time, but several -jobs can be suspended or running in the background at once. As each job -is started, it is assigned a small identifying -number called the -.I "job number" -which can be used later to refer to the job in the commands described below. -Job numbers remain -the same until the job terminates and then are re-used. -.PP -When a job is started in the background using `&', its number, as well -as the process numbers of all its (top level) commands, is typed by the shell -before prompting you for another command. -For example, -.DS -% ls \-s | sort \-n > usage & -[2] 2034 2035 -% -.DE -runs the `ls' program with the `\-s' options, pipes this output into -the `sort' program with the `\-n' option which puts its output into the -file `usage'. -Since the `&' was at the end of the line, these two programs were started -together as a background job. After starting the job, the shell prints -the job number in brackets (2 in this case) followed by the process number -of each program started in the job. Then the shell immediates prompts for -a new command, leaving the job running simultaneously. -.PP -As mentioned in section 1.8, foreground jobs become -.I suspended -by typing ^Z -which sends a \s-2STOP\s0 signal to the currently running -foreground job. A background job can become suspended by using the -.I stop -command described below. When jobs are suspended they merely stop -any further progress until started again, either in the foreground -or the background. The shell notices when a job becomes stopped and -reports this fact, much like it reports the termination of background jobs. -For foreground jobs this looks like -.DS -% du > usage -^Z -Stopped -% -.DE -`Stopped' message is typed by the shell when it notices that the -.I du -program stopped. -For background jobs, using the -.I stop -command, it is -.DS -% sort usage & -[1] 2345 -% stop %1 -.ta 1.75i -[1] + Stopped (signal) sort usage -% -.so tabs -.DE -Suspending foreground jobs can be very useful when you need to temporarily -change what you are doing (execute other commands) and then return to -the suspended job. Also, foreground jobs can be suspended and then -continued as background jobs using the -.I bg -command, allowing you to continue other work and -stop waiting for the foreground job to finish. Thus -.DS -% du > usage -^Z -Stopped -% bg -[1] du > usage & -% -.DE -starts `du' in the foreground, stops it before it finishes, then continues -it in the background allowing more foreground commands to be executed. -This is especially helpful -when a foreground job ends up taking longer than you expected and you -wish you had started it in the background in the beginning. -.PP -All -.I "job control" -commands can take an argument that identifies a particular -job. -All job name arguments begin with the character `%', since some of the -job control commands also accept process numbers (printed by the -.I ps -command.) -The default job (when no argument is given) is called the -.I current -job and is identified by a `+' in the output of the -.I jobs -command, which shows you which jobs you have. -When only one job is stopped or running in the background (the usual case) -it is always the current job thus no argument is needed. -If a job is stopped while running in the foreground it becomes the -.I current -job and the existing current job becomes the -.I previous -job \- identified by a `\-' in the output of -.I jobs. -When the current job terminates, the previous job becomes the current job. -When given, the argument is either `%\-' (indicating -the previous job); `%#', where # is the job number; -`%pref' where pref is some unique prefix of the command name -and arguments of one of the jobs; or `%?' followed by some string found -in only one of the jobs. -.PP -The -.I jobs -command types the table of jobs, giving the job number, -commands and status (`Stopped' or `Running') of each background or -suspended job. With the `\-l' option the process numbers are also -typed. -.DS -% du > usage & -[1] 3398 -% ls \-s | sort \-n > myfile & -[2] 3405 -% mail bill -^Z -Stopped -% jobs -.ta 1.75i -[1] \(mi Running du > usage -[2] Running ls \-s | sort \-n > myfile -[3] \(pl Stopped mail bill -% fg %ls -ls \-s | sort \-n > myfile -% more myfile -.so tabs -.DE -.PP -The -.I fg -command runs a suspended or background job in the foreground. It is -used to restart a previously suspended job or change a background job -to run in the foreground (allowing signals or input from the terminal). -In the above example we used -.I fg -to change the `ls' job from the -background to the foreground since we wanted to wait for it to -finish before looking at its output file. -The -.I bg -command runs a suspended job in the background. It is usually used -after stopping the currently running foreground job with the -\s-2STOP\s0 signal. The combination of the \s-2STOP\s0 signal and the -.I bg -command changes a foreground job into a background job. -The -.I stop -command suspends a background job. -.PP -The -.I kill -command terminates a background or suspended job immediately. -In addition to jobs, it may be given process numbers as arguments, -as printed by -.I ps. -Thus, in the example above, the running -.I du -command could have been terminated by the command -.DS -% kill %1 -.ta 1.75i -[1] Terminated du > usage -% -.so tabs -.DE -.PP -The -.I notify -command (not the variable mentioned earlier) indicates that the termination -of a specific job should be -reported at the time it finishes instead of waiting for the next prompt. -.PP -If a job running in the background tries to read input from the terminal -it is automatically stopped. When such a job is then run in the -foreground, input can be given to the job. If desired, the job can -be run in the background again until it requests input again. -This is illustrated in the following sequence where the `s' command in the -text editor might take a long time. -.ID -.nf -% ed bigfile -120000 -1,$s/thisword/thatword/ -^Z -Stopped -% bg -[1] ed bigfile & -% - . . . some foreground commands -.ta 1.75i -[1] Stopped (tty input) ed bigfile -% fg -ed bigfile -w -120000 -q -% -.so tabs -.DE -So after the `s' command was issued, the `ed' job was stopped with ^Z -and then put in the background using -.I bg. -Some time later when the `s' command was finished, -.I ed -tried to read another command and was stopped because jobs -in the background cannot read from the terminal. The -.I fg -command returned the `ed' job to the foreground where it could once again -accept commands from the terminal. -.PP -The command -.DS -stty tostop -.DE -causes all background jobs run on your terminal to stop -when they are about to -write output to the terminal. This prevents messages from background -jobs from interrupting foreground job output and allows you to run -a job in the background without losing terminal output. It also -can be used for interactive programs that sometimes have long -periods without interaction. Thus each time it outputs a prompt for more -input it will stop before the prompt. It can then be run in the -foreground using -.I fg, -more input can be given and, if necessary stopped and returned to -the background. This -.I stty -command might be a good thing to put in your -.I \&.login -file if you do not like output from background jobs interrupting -your work. It also can reduce the need for redirecting the output -of background jobs if the output is not very big: -.DS -% stty tostop -% wc hugefile & -[1] 10387 -% ed text -\&. . . some time later -q -.ta 1.75i -[1] Stopped (tty output) wc hugefile -% fg wc -wc hugefile - 13371 30123 302577 -% stty \-tostop -.so tabs -.DE -Thus after some time the `wc' command, which counts the lines, words -and characters in a file, had one line of output. When it tried to -write this to the terminal it stopped. By restarting it in the -foreground we allowed it to write on the terminal exactly when we were -ready to look at its output. -Programs which attempt to change the mode of the terminal will also -block, whether or not -.I tostop -is set, when they are not in the foreground, as -it would be very unpleasant to have a background job change the state -of the terminal. -.PP -Since the -.I jobs -command only prints jobs started in the currently executing shell, -it knows nothing about background jobs started in other login sessions -or within shell files. The -.I ps -can be used in this case to find out about background jobs not started -in the current shell. -.NH 2 -Working Directories -.PP -As mentioned in section 1.6, the shell is always in a particular -.I "working directory." -The `change directory' command -.I chdir -(its -short form -.I cd -may also be used) -changes the working directory of the shell, -that is, changes the directory you -are located in. -.PP -It is useful to make a directory for each project you wish to work on -and to place all files related to that project in that directory. -The `make directory' command, -.I mkdir, -creates a new directory. -The -.I pwd -(`print working directory') command -reports the absolute pathname of the working directory of the shell, -that is, the directory you are -located in. -Thus in the example below: -.DS -% pwd -/usr/bill -% mkdir newpaper -% chdir newpaper -% pwd -/usr/bill/newpaper -% -.DE -the user has created and moved to the -directory -.I newpaper. -where, for example, he might -place a group of related files. -.PP -No matter where you have moved to in a directory hierarchy, -you can return to your `home' login directory by doing just -.DS -cd -.DE -with no arguments. -The name `..' always means the directory above the current one in -the hierarchy, thus -.DS -cd .. -.DE -changes the shell's working directory to the one directly above the -current one. -The name `..' can be used in any -pathname, thus, -.DS -cd ../programs -.DE -means -change to the directory `programs' contained in the directory -above the current one. -If you have several directories for different -projects under, say, your home directory, -this shorthand notation -permits you to switch easily between them. -.PP -The shell always remembers the pathname of its current working directory in -the variable -.I cwd. -The shell can also be requested to remember the previous directory when -you change to a new working directory. If the `push directory' command -.I pushd -is used in place of the -.I cd -command, the shell saves the name of the current working directory -on a -.I "directory stack" -before changing to the new one. -You can see this list at any time by typing the `directories' -command -.I dirs. -.ID -.nf -% pushd newpaper/references -~/newpaper/references ~ -% pushd /usr/lib/tmac -/usr/lib/tmac ~/newpaper/references ~ -% dirs -/usr/lib/tmac ~/newpaper/references ~ -% popd -~/newpaper/references ~ -% popd -~ -% -.DE -The list is printed in a horizontal line, reading left to right, -with a tilde (~) as -shorthand for your home directory\(emin this case `/usr/bill'. -The directory stack is printed whenever there is more than one -entry on it and it changes. -It is also printed by a -.I dirs -command. -.I Dirs -is usually faster and more informative than -.I pwd -since it shows the current working directory as well as any -other directories remembered in the stack. -.PP -The -.I pushd -command with no argument -alternates the current directory with the first directory in the -list. -The `pop directory' -.I popd -command without an argument returns you to the directory you were in prior to -the current one, discarding the previous current directory from the -stack (forgetting it). -Typing -.I popd -several times in a series takes you backward through the directories -you had been in (changed to) by -.I pushd -command. -There are other options to -.I pushd -and -.I popd -to manipulate the contents of the directory stack and to change -to directories not at the top of the stack; see the -.I csh -manual page for details. -.PP -Since the shell remembers the working directory in which each job -was started, it warns you when you might be confused by restarting -a job in the foreground which has a different working directory than the -current working directory of the shell. Thus if you start a background -job, then change the shell's working directory and then cause the -background job to run in the foreground, the shell warns you that the -working directory of the currently running foreground job is different -from that of the shell. -.DS -% dirs \-l -/mnt/bill -% cd myproject -% dirs -~/myproject -% ed prog.c -1143 -^Z -Stopped -% cd .. -% ls -myproject -textfile -% fg -ed prog.c (wd: ~/myproject) -.DE -This way the shell warns you when there -is an implied change of working directory, even though no cd command was -issued. In the above example the `ed' job was still in `/mnt/bill/project' -even though the shell had changed to `/mnt/bill'. -A similar warning is given when such a foreground job -terminates or is suspended (using the \s-2STOP\s0 signal) since -the return to the shell again implies a change of working directory. -.DS -% fg -ed prog.c (wd: ~/myproject) - . . . after some editing -q -(wd now: ~) -% -.DE -These messages are sometimes confusing if you use programs that change -their own working directories, since the shell only remembers which -directory a job is started in, and assumes it stays there. -The `\-l' option of -.I jobs -will type the working directory -of suspended or background jobs when it is different -from the current working directory of the shell. -.NH 2 -Useful built-in commands -.PP -We now give a few of the useful built-in commands of the shell describing -how they are used. -.PP -The -.I alias -command described above is used to assign new aliases and to show the -existing aliases. -With no arguments it prints the current aliases. -It may also be given only one argument such as -.DS -alias ls -.DE -to show the current alias for, e.g., `ls'. -.PP -The -.I echo -command prints its arguments. -It is often used in -.I "shell scripts" -or as an interactive command -to see what filename expansions will produce. -.PP -The -.I history -command will show the contents of the history list. -The numbers given with the history events can be used to reference -previous events which are difficult to reference using the -contextual mechanisms introduced above. -There is also a shell variable called -.I prompt. -By placing a `!' character in its value the shell will there substitute -the number of the current command in the history list. -You can use this number to refer to this command in a history substitution. -Thus you could -.DS -set prompt=\'\e! % \' -.DE -Note that the `!' character had to be -.I escaped -here even within `\'' characters. -.PP -The -.I limit -command is used to restrict use of resources. -With no arguments it prints the current limitations: -.DS -.ta 1i -cputime unlimited -filesize unlimited -datasize 5616 kbytes -stacksize 512 kbytes -coredumpsize unlimited -.so tabs -.DE -Limits can be set, e.g.: -.DS -limit coredumpsize 128k -.DE -Most reasonable units abbreviations will work; see the -.I csh -manual page for more details. -.PP -The -.I logout -command can be used to terminate a login shell which has -.I ignoreeof -set. -.PP -The -.I rehash -command causes the shell to recompute a table of where commands are -located. This is necessary if you add a command to a directory -in the current shell's search path and wish the shell to find it, -since otherwise the hashing algorithm may tell the shell that the -command wasn't in that directory when the hash table was computed. -.PP -The -.I repeat -command can be used to repeat a command several times. -Thus to make 5 copies of the file -.I one -in the file -.I five -you could do -.DS -repeat 5 cat one >> five -.DE -.PP -The -.I setenv -command can be used -to set variables in the environment. -Thus -.DS -setenv TERM adm3a -.DE -will set the value of the environment variable \s-2TERM\s0 -to -`adm3a'. -A user program -.I printenv -exists which will print out the environment. -It might then show: -.DS -% printenv -HOME=/usr/bill -SHELL=/bin/csh -PATH=:/usr/ucb:/bin:/usr/bin:/usr/local -TERM=adm3a -USER=bill -% -.DE -.PP -The -.I source -command can be used to force the current shell to read commands from -a file. -Thus -.DS -source .cshrc -.DE -can be used after editing in a change to the -.I \&.cshrc -file which you wish to take effect right away. -.PP -The -.I time -command can be used to cause a command to be timed no matter how much -\s-2CPU\s0 time it takes. -Thus -.DS -% time cp /etc/rc /usr/bill/rc -0.0u 0.1s 0:01 8% 2+1k 3+2io 1pf+0w -% time wc /etc/rc /usr/bill/rc - 52 178 1347 /etc/rc - 52 178 1347 /usr/bill/rc - 104 356 2694 total -0.1u 0.1s 0:00 13% 3+3k 5+3io 7pf+0w -% -.DE -indicates that the -.I cp -command used a negligible amount of user time (u) -and about 1/10th of a system time (s); the elapsed time was 1 second (0:01), -there was an average memory usage of 2k bytes of program space and 1k -bytes of data space over the cpu time involved (2+1k); the program -did three disk reads and two disk writes (3+2io), and took one page fault -and was not swapped (1pf+0w). -The word count command -.I wc -on the other hand used 0.1 seconds of user time and 0.1 seconds of system -time in less than a second of elapsed time. -The percentage `13%' indicates that over the period when it was active -the command `wc' used an average of 13 percent of the available \s-2CPU\s0 -cycles of the machine. -.PP -The -.I unalias -and -.I unset -commands can be used -to remove aliases and variable definitions from the shell, and -.I unsetenv -removes variables from the environment. -.NH 2 -What else? -.PP -This concludes the basic discussion of the shell for terminal users. -There are more features of the shell to be discussed here, and all -features of the shell are discussed in its manual pages. -One useful feature which is discussed later is the -.I foreach -built-in command which can be used to run the same command -sequence with a number of different arguments. -.PP -If you intend to use \s-2UNIX\s0 a lot you should look through -the rest of this document and the csh manual pages (section1) to become familiar -with the other facilities which are available to you. -.bp diff --git a/bin/csh/USD.doc/csh.3 b/bin/csh/USD.doc/csh.3 deleted file mode 100644 index 76ee1eb..0000000 --- a/bin/csh/USD.doc/csh.3 +++ /dev/null @@ -1,649 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)csh.3 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.nr H1 2 -.NH -Shell control structures and command scripts -.NH 2 -Introduction -.PP -It is possible to place commands in files and to cause shells to be -invoked to read and execute commands from these files, -which are called -.I "shell scripts." -We here detail those features of the shell useful to the writers of such -scripts. -.NH 2 -Make -.PP -It is important to first note what shell scripts are -.I not -useful for. -There is a program called -.I make -which is very useful for maintaining a group of related files -or performing sets of operations on related files. -For instance a large program consisting of one or more files -can have its dependencies described in a -.I makefile -which contains definitions of the commands used to create these -different files when changes occur. -Definitions of the means for printing listings, cleaning up the directory -in which the files reside, and installing the resultant programs -are easily, and most appropriately placed in this -.I makefile. -This format is superior and preferable to maintaining a group of shell -procedures to maintain these files. -.PP -Similarly when working on a document a -.I makefile -may be created which defines how different versions of the document -are to be created and which options of -.I nroff -or -.I troff -are appropriate. -.NH 2 -Invocation and the argv variable -.PP -A -.I csh -command script may be interpreted by saying -.DS -% csh script ... -.DE -where -.I script -is the name of the file containing a group of -.I csh -commands and -`\&...' is replaced by a sequence of arguments. -The shell places these arguments in the variable -.I argv -and then begins to read commands from the script. -These parameters are then available through the same mechanisms -which are used to reference any other shell variables. -.PP -If you make the file -`script' -executable by doing -.DS -chmod 755 script -.DE -and place a shell comment at the beginning of the shell script -(i.e. begin the file with a `#' character) -then a `/bin/csh' will automatically be invoked to execute `script' when -you type -.DS -script -.DE -If the file does not begin with a `#' then the standard shell -`/bin/sh' will be used to execute it. -This allows you to convert your older shell scripts to use -.I csh -at your convenience. -.NH 2 -Variable substitution -.PP -After each input line is broken into words and history substitutions -are done on it, the input line is parsed into distinct commands. -Before each command is executed a mechanism know as -.I "variable substitution" -is done on these words. -Keyed by the character `$' this substitution replaces the names -of variables by their values. -Thus -.DS -echo $argv -.DE -when placed in a command script would cause the current value of the -variable -.I argv -to be echoed to the output of the shell script. -It is an error for -.I argv -to be unset at this point. -.PP -A number of notations are provided for accessing components and attributes -of variables. -The notation -.DS -$?name -.DE -expands to `1' if name is -.I set -or to `0' -if name is not -.I set. -It is the fundamental mechanism used for checking whether particular -variables have been assigned values. -All other forms of reference to undefined variables cause errors. -.PP -The notation -.DS -$#name -.DE -expands to the number of elements in the variable -.I name. -Thus -.DS -% set argv=(a b c) -% echo $?argv -1 -% echo $#argv -3 -% unset argv -% echo $?argv -0 -% echo $argv -Undefined variable: argv. -% -.DE -.PP -It is also possible to access the components of a variable -which has several values. -Thus -.DS -$argv[1] -.DE -gives the first component of -.I argv -or in the example above `a'. -Similarly -.DS -$argv[$#argv] -.DE -would give `c', -and -.DS -$argv[1\-2] -.DE -would give `a b'. Other notations useful in shell scripts are -.DS -$\fIn\fR -.DE -where -.I n -is an integer as a shorthand for -.DS -$argv[\fIn\fR\|] -.DE -the -.I n\|th -parameter and -.DS -$* -.DE -which is a shorthand for -.DS -$argv -.DE -The form -.DS -$$ -.DE -expands to the process number of the current shell. -Since this process number is unique in the system it can -be used in generation of unique temporary file names. -The form -.DS -$< -.DE -is quite special and is replaced by the next line of input read from -the shell's standard input (not the script it is reading). This is -useful for writing shell scripts that are interactive, reading -commands from the terminal, or even writing a shell script that -acts as a filter, reading lines from its input file. -Thus the sequence -.DS -echo 'yes or no?\ec' -set a=($<) -.DE -would write out the prompt `yes or no?' without a newline and then -read the answer into the variable `a'. In this case `$#a' would be -`0' if either a blank line or end-of-file (^D) was typed. -.PP -One minor difference between `$\fIn\fR\|' and `$argv[\fIn\fR\|]' -should be noted here. -The form -`$argv[\fIn\fR\|]' -will yield an error if -.I n -is not in the range -`1\-$#argv' -while `$n' -will never yield an out of range subscript error. -This is for compatibility with the way older shells handled parameters. -.PP -Another important point is that it is never an error to give a subrange -of the form `n\-'; if there are less than -.I n -components of the given variable then no words are substituted. -A range of the form `m\-n' likewise returns an empty vector without giving -an error when \fIm\fR exceeds the number of elements of the given variable, -provided the subscript \fIn\fR is in range. -.NH 2 -Expressions -.PP -In order for interesting shell scripts to be constructed it -must be possible to evaluate expressions in the shell based on the -values of variables. -In fact, all the arithmetic operations of the language C are available -in the shell -with the same precedence that they have in C. -In particular, the operations `==' and `!=' compare strings -and the operators `&&' and `|\|\||' implement the boolean and/or operations. -The special operators `=~' and `!~' are similar to `==' and `!=' except -that the string on the right side can have pattern matching characters -(like *, ? or []) and the test is whether the string on the left matches -the pattern on the right. -.PP -The shell also allows file enquiries of the form -.DS -\-? filename -.DE -where `?' is replace by a number of single characters. -For instance the expression primitive -.DS -\-e filename -.DE -tell whether the file -`filename' -exists. -Other primitives test for read, write and execute access to the file, -whether it is a directory, or has non-zero length. -.PP -It is possible to test whether a command terminates normally, -by a primitive of the -form `{ command }' which returns true, i.e. `1' if the command -succeeds exiting normally with exit status 0, or `0' if the command -terminates abnormally or with exit status non-zero. -If more detailed information about the execution status of a command -is required, it can be executed and the variable `$status' examined -in the next command. -Since `$status' is set by every command, it is very transient. -It can be saved if it is inconvenient to use it only in the single -immediately following command. -.PP -For a full list of expression components available see the manual -section for the shell. -.NH 2 -Sample shell script -.PP -A sample shell script which makes use of the expression mechanism -of the shell and some of its control structure follows: -.DS -% cat copyc -# -# Copyc copies those C programs in the specified list -# to the directory ~/backup if they differ from the files -# already in ~/backup -# -set noglob -foreach i ($argv) - - if ($i !~ *.c) continue # not a .c file so do nothing - - if (! \-r ~/backup/$i:t) then - echo $i:t not in backup... not cp\e\'ed - continue - endif - - cmp \-s $i ~/backup/$i:t # to set $status - - if ($status != 0) then - echo new backup of $i - cp $i ~/backup/$i:t - endif -end -.DE -.PP -This script makes use of the -.I foreach -command, which causes the shell to execute the commands between the -.I foreach -and the matching -.I end -for each of the values given between `(' and `)' with the named -variable, in this case `i' set to successive values in the list. -Within this loop we may use the command -.I break -to stop executing the loop -and -.I continue -to prematurely terminate one iteration -and begin the next. -After the -.I foreach -loop the iteration variable -(\fIi\fR in this case) -has the value at the last iteration. -.PP -We set the variable -.I noglob -here to prevent filename expansion of the members of -.I argv. -This is a good idea, in general, if the arguments to a shell script -are filenames which have already been expanded or if the arguments -may contain filename expansion metacharacters. -It is also possible to quote each use of a `$' variable expansion, -but this is harder and less reliable. -.PP -The other control construct used here is a statement of the form -.DS -\fBif\fR ( expression ) \fBthen\fR - command - ... -\fBendif\fR -.DE -The placement of the keywords here is -.B not -flexible due to the current implementation of the shell.\(dg -.FS -\(dgThe following two formats are not currently acceptable to the shell: -.sp -.in +5 -.nf -\fBif\fR ( expression ) # \fBWon't work!\fR -\fBthen\fR - command - ... -\fBendif\fR -.fi -.in -5 -.sp -and -.sp -.in +5 -.nf -\fBif\fR ( expression ) \fBthen\fR command \fBendif\fR # \fBWon't work\fR -.in -5 -.fi -.FE -.PP -The shell does have another form of the if statement of the form -.DS -\fBif\fR ( expression ) \fBcommand\fR -.DE -which can be written -.DS -\fBif\fR ( expression ) \e - command -.DE -Here we have escaped the newline for the sake of appearance. -The command must not involve `\||\|', `&' or `;' -and must not be another control command. -The second form requires the final `\e' to -.B immediately -precede the end-of-line. -.PP -The more general -.I if -statements above also admit a sequence of -.I else\-if -pairs followed by a single -.I else -and an -.I endif, -e.g.: -.DS -\fBif\fR ( expression ) \fBthen\fR - commands -\fBelse\fR \fBif\fR (expression ) \fBthen\fR - commands -\&... - -\fBelse\fR - commands -\fBendif\fR -.DE -.PP -Another important mechanism used in shell scripts is the `:' modifier. -We can use the modifier `:r' here to extract a root of a filename or -`:e' to extract the -.I extension. -Thus if the variable -.I i -has the value -`/mnt/foo.bar' -then -.sp -.in +5 -.nf -% echo $i $i:r $i:e -/mnt/foo.bar /mnt/foo bar -% -.sp -.in -5 -.fi -shows how the `:r' modifier strips off the trailing `.bar' and the -the `:e' modifier leaves only the `bar'. -Other modifiers will take off the last component of a pathname leaving -the head `:h' or all but the last component of a pathname leaving the -tail `:t'. -These modifiers are fully described in the -.I csh -manual pages in the User's Reference Manual. -It is also possible to use the -.I "command substitution" -mechanism described in the next major section to perform modifications -on strings to then reenter the shell's environment. -Since each usage of this mechanism involves the creation of a new process, -it is much more expensive to use than the `:' modification mechanism.\(dd -.FS -\(dd It is also important to note that -the current implementation of the shell limits the number of `:' modifiers -on a `$' substitution to 1. -Thus -.sp -.nf -.in +5 -% echo $i $i:h:t -/a/b/c /a/b:t -% -.in -5 -.fi -.sp -does not do what one would expect. -.FE -Finally, we note that the character `#' lexically introduces a shell -comment in shell scripts (but not from the terminal). -All subsequent characters on the input line after a `#' are discarded -by the shell. -This character can be quoted using `\'' or `\e' to place it in -an argument word. -.NH 2 -Other control structures -.PP -The shell also has control structures -.I while -and -.I switch -similar to those of C. -These take the forms -.DS -\fBwhile\fR ( expression ) - commands -\fBend\fR -.DE -and -.DS -\fBswitch\fR ( word ) - -\fBcase\fR str1: - commands - \fBbreaksw\fR - -\& ... - -\fBcase\fR strn: - commands - \fBbreaksw\fR - -\fBdefault:\fR - commands - \fBbreaksw\fR - -\fBendsw\fR -.DE -For details see the manual section for -.I csh. -C programmers should note that we use -.I breaksw -to exit from a -.I switch -while -.I break -exits a -.I while -or -.I foreach -loop. -A common mistake to make in -.I csh -scripts is to use -.I break -rather than -.I breaksw -in switches. -.PP -Finally, -.I csh -allows a -.I goto -statement, with labels looking like they do in C, i.e.: -.DS -loop: - commands - \fBgoto\fR loop -.DE -.NH 2 -Supplying input to commands -.PP -Commands run from shell scripts receive by default the standard -input of the shell which is running the script. -This is different from previous shells running -under \s-2UNIX\s0. It allows shell scripts to fully participate -in pipelines, but mandates extra notation for commands which are to take -inline data. -.PP -Thus we need a metanotation for supplying inline data to commands in -shell scripts. -As an example, consider this script which runs the editor to -delete leading blanks from the lines in each argument file: -.DS -% cat deblank -# deblank \-\- remove leading blanks -foreach i ($argv) -ed \- $i << \'EOF\' -1,$s/^[ ]*// -w -q -\&\'EOF\' -end -% -.DE -The notation `<< \'EOF\'' -means that the standard input for the -.I ed -command is to come from the text in the shell script file -up to the next line consisting of exactly `\'EOF\''. -The fact that the `EOF' is enclosed in `\'' characters, i.e. quoted, -causes the shell to not perform variable substitution on the -intervening lines. -In general, if any part of the word following the `<<' which the -shell uses to terminate the text to be given to the command is quoted -then these substitutions will not be performed. -In this case since we used the form `1,$' in our editor script -we needed to insure that this `$' was not variable substituted. -We could also have insured this by preceding the `$' here with a `\e', -i.e.: -.DS -1,\e$s/^[ ]*// -.DE -but quoting the `EOF' terminator is a more reliable way of achieving the -same thing. -.NH 2 -Catching interrupts -.PP -If our shell script creates temporary files, we may wish to catch -interruptions of the shell script so that we can clean up -these files. -We can then do -.DS -onintr label -.DE -where -.I label -is a label in our program. -If an interrupt is received the shell will do a -`goto label' -and we can remove the temporary files and then do an -.I exit -command (which is built in to the shell) -to exit from the shell script. -If we wish to exit with a non-zero status we can do -.DS -exit(1) -.DE -e.g. to exit with status `1'. -.NH 2 -What else? -.PP -There are other features of the shell useful to writers of shell -procedures. -The -.I verbose -and -.I echo -options and the related -.I \-v -and -.I \-x -command line options can be used to help trace the actions of the shell. -The -.I \-n -option causes the shell only to read commands and not to execute -them and may sometimes be of use. -.PP -One other thing to note is that -.I csh -will not execute shell scripts which do not begin with the -character `#', that is shell scripts that do not begin with a comment. -Similarly, the `/bin/sh' on your system may well defer to `csh' -to interpret shell scripts which begin with `#'. -This allows shell scripts for both shells to live in harmony. -.PP -There is also another quotation mechanism using `"' which allows -only some of the expansion mechanisms we have so far discussed to occur -on the quoted string and serves to make this string into a single word -as `\'' does. -.bp diff --git a/bin/csh/USD.doc/csh.4 b/bin/csh/USD.doc/csh.4 deleted file mode 100644 index 7ef24dc..0000000 --- a/bin/csh/USD.doc/csh.4 +++ /dev/null @@ -1,176 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)csh.4 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.nr H1 3 -.NH -Other, less commonly used, shell features -.NH 2 -Loops at the terminal; variables as vectors -.PP -It is occasionally useful to use the -.I foreach -control structure at the terminal to aid in performing a number -of similar commands. -For instance, there were at one point three shells in use on the Cory \s-2UNIX\s0 -system at Cory Hall, -`/bin/sh', -`/bin/nsh', -and -`/bin/csh'. -To count the number of persons using each shell one could have issued -the commands -.DS -% grep \-c csh$ /etc/passwd -27 -% grep \-c nsh$ /etc/passwd -128 -% grep \-c \-v sh$ /etc/passwd -430 -% -.DE -Since these commands are very similar we can use -.I foreach -to do this more easily. -.DS -% foreach i (\'sh$\' \'csh$\' \'\-v sh$\') -? grep \-c $i /etc/passwd -? end -27 -128 -430 -% -.DE -Note here that the shell prompts for -input with `? ' when reading the body of the loop. -.PP -Very useful with loops are variables which contain lists of filenames -or other words. -You can, for example, do -.DS -% set a=(\`ls\`) -% echo $a -csh.n csh.rm -% ls -csh.n -csh.rm -% echo $#a -2 -% -.DE -The -.I set -command here gave the variable -.I a -a list of all the filenames in the current directory as value. -We can then iterate over these names to perform any chosen function. -.PP -The output of a command within `\`' characters is converted by -the shell to a list of words. -You can also place the `\`' quoted string within `"' characters -to take each (non-empty) line as a component of the variable; -preventing the lines from being split into words at blanks and tabs. -A modifier `:x' exists which can be used later to expand each component -of the variable into another variable splitting it into separate words -at embedded blanks and tabs. -.NH 2 -Braces { ... } in argument expansion -.PP -Another form of filename expansion, alluded -to before involves the characters `{' and `}'. -These characters specify that the contained strings, separated by `,' -are to be consecutively substituted into the containing characters -and the results expanded left to right. -Thus -.DS -A{str1,str2,...strn}B -.DE -expands to -.DS -Astr1B Astr2B ... AstrnB -.DE -This expansion occurs before the other filename expansions, and may -be applied recursively (i.e. nested). -The results of each expanded string are sorted separately, left -to right order being preserved. -The resulting filenames are not required to exist if no other expansion -mechanisms are used. -This means that this mechanism can be used to generate arguments which are -not filenames, but which have common parts. -.PP -A typical use of this would be -.DS -mkdir ~/{hdrs,retrofit,csh} -.DE -to make subdirectories `hdrs', `retrofit' and `csh' -in your home directory. -This mechanism is most useful when the common prefix is longer -than in this example, i.e. -.DS -chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}} -.DE -.NH 2 -Command substitution -.PP -A command enclosed in `\`' characters is replaced, just before -filenames are expanded, by the output from that command. -Thus it is possible to do -.DS -set pwd=\`pwd\` -.DE -to save the current directory in the variable -.I pwd -or to do -.DS -ex \`grep \-l TRACE *.c\` -.DE -to run the editor -.I ex -supplying as arguments those files whose names end in `.c' -which have the string `TRACE' in them.* -.FS -*Command expansion also occurs in input redirected with `<<' -and within `"' quotations. -Refer to the shell manual section for full details. -.FE -.NH 2 -Other details not covered here -.PP -In particular circumstances it may be necessary to know the exact -nature and order of different substitutions performed by the shell. -The exact meaning of certain combinations of quotations is also -occasionally important. -These are detailed fully in its manual section. -.PP -The shell has a number of command line option flags mostly of use -in writing \s-2UNIX\s0 programs, -and debugging shell scripts. -See the csh(1) manual section for a list of these options. -.bp diff --git a/bin/csh/USD.doc/csh.a b/bin/csh/USD.doc/csh.a deleted file mode 100644 index 22c8f76..0000000 --- a/bin/csh/USD.doc/csh.a +++ /dev/null @@ -1,93 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)csh.a 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.SH -Appendix \- Special characters -.LP -The following table lists the special characters of -.I csh -and the \s-2UNIX\s0 system, giving for each the section(s) in which it -is discussed. -A number of these characters also have special meaning in expressions. -See the -.I csh -manual section -for a complete list. -.ta .75i 1.5i 2.25i -.LP -Syntactic metacharacters -.DS -; 2.4 separates commands to be executed sequentially -| 1.5 separates commands in a pipeline -( ) 2.2,3.6 brackets expressions and variable values -& 2.5 follows commands to be executed without waiting for completion -.DE -.LP -Filename metacharacters -.DS -/ 1.6 separates components of a file's pathname -\&. 1.6 separates root parts of a file name from extensions -? 1.6 expansion character matching any single character -* 1.6 expansion character matching any sequence of characters -[ ] 1.6 expansion sequence matching any single character from a set -~ 1.6 used at the beginning of a filename to indicate home directories -{ } 4.2 used to specify groups of arguments with common parts -.DE -.LP -Quotation metacharacters -.DS -\e 1.7 prevents meta-meaning of following single character -\' 1.7 prevents meta-meaning of a group of characters -" 4.3 like \', but allows variable and command expansion -.DE -.LP -Input/output metacharacters -.DS -< 1.5 indicates redirected input -> 1.3 indicates redirected output -.DE -.LP -Expansion/substitution metacharacters -.DS -$ 3.4 indicates variable substitution -! 2.3 indicates history substitution -: 3.6 precedes substitution modifiers -^ 2.3 used in special forms of history substitution -\` 4.3 indicates command substitution -.DE -.LP -Other metacharacters -.DS -# 1.3,3.6 begins scratch file names; indicates shell comments -\- 1.2 prefixes option (flag) arguments to commands -% 2.6 prefixes job name specifications -.DE -.bp diff --git a/bin/csh/USD.doc/csh.g b/bin/csh/USD.doc/csh.g deleted file mode 100644 index ba1b161..0000000 --- a/bin/csh/USD.doc/csh.g +++ /dev/null @@ -1,1719 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)csh.g 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.SH -Glossary -.PP -This glossary lists the most important terms introduced in the -introduction to the -shell and gives references to sections of the shell -document for further information about them. -References of the form -`pr (1)' -indicate that the command -.I pr -is in the \s-2UNIX\s0 User Reference manual in section 1. -You can look at an online copy of its manual page by doing -.DS -man 1 pr -.DE -References of the form (2.5) -indicate that more information can be found in section 2.5 of this -manual. -.IP \&\fB.\fR 15n -Your current directory has the name `.' as well as the name printed -by the command -.I pwd; -see also -.I dirs. -The current directory `.' is usually the first -.I component -of the search path contained in the variable -.I path , -thus commands which are in `.' are found first (2.2). -The character `.' is also used in separating -.I components -of filenames -(1.6). -The character `.' at the beginning of a -.I component -of a -.I pathname -is treated specially and not matched by the -.I "filename expansion" -metacharacters `?', `*', and `[' `]' pairs (1.6). -.IP \&\fB..\fR -Each directory has a file `..' in it which is a reference to its -parent directory. -After changing into the directory with -.I chdir , -i.e. -.DS -chdir paper -.DE -you can return to the parent directory by doing -.DS -chdir .. -.DE -The current directory is printed by -.I pwd -(2.7). -.IP a.out -Compilers which create executable images create them, by default, in the -file -.I a.out. -for historical reasons (2.3). -.IP "absolute pathname" -.br -A -.I pathname -which begins with a `/' is -.I absolute -since it specifies the -.I path -of directories from the beginning -of the entire directory system \- called the -.I root -directory. -.I Pathname s -which are not -.I absolute -are called -.I relative -(see definition of -.I "relative pathname" ) -(1.6). -.IP alias -An -.I alias -specifies a shorter or different name for a \s-2UNIX\s0 -command, or a transformation on a command to be performed in -the shell. -The shell has a command -.I alias -which establishes -.I aliases -and can print their current values. -The command -.I unalias -is used to remove -.I aliases -(2.4). -.IP argument -Commands in \s-2UNIX\s0 receive a list of -.I argument -words. -Thus the command -.DS -echo a b c -.DE -consists of the -.I "command name" -`echo' and three -.I argument -words `a', `b' and `c'. -The set of -.I arguments -after the -.I "command name" -is said to be the -.I "argument list" -of the command (1.1). -.IP argv -The list of arguments to a command written in the shell language -(a shell script or shell procedure) is stored in a variable called -.I argv -within the shell. -This name is taken from the conventional name in the -C programming language (3.4). -.IP background -Commands started without waiting for them to complete are called -.I background -commands (2.6). -.IP base -A filename is sometimes thought of as consisting of a -.I base -part, before any `.' character, and an -.I extension -\- the part after -the `.'. See -.I filename -and -.I extension -(1.6) and basename (1). -.IP bg -The -.I bg -command causes a -.I suspended -job to continue execution in the -.I background -(2.6). -.IP bin -A directory containing binaries of programs and shell scripts to be -executed is typically called a -.I bin -directory. -The standard system -.I bin -directories are `/bin' containing the most -heavily used commands and `/usr/bin' which contains most other user -programs. -Programs developed at UC Berkeley live in `/usr/ucb', while locally -written programs live in `/usr/local'. Games are kept in the directory -`/usr/games'. -You can place binaries in any directory. -If you wish to execute them often, the name of the directories -should be a -.I component -of the variable -.I path . -.IP break -.I Break -is a builtin command used to exit from loops within the control -structure of the shell (3.7). -.IP breaksw -The -.I breaksw -builtin command is used to exit from a -.I switch -control structure, like a -.I break -exits from loops (3.7). -.IP builtin -A command executed directly by the shell is called a -.I builtin -command. -Most commands in \s-2UNIX\s0 are not built into the shell, -but rather exist as files in -.I bin -directories. -These commands are accessible because the directories in which -they reside are named in the -.I path -variable. -.IP case -A -.I case -command is used as a label in a -.I switch -statement in the shell's control structure, similar to that of the -language C. -Details are given in the shell documentation `csh (1)' (3.7). -.IP cat -The -.I cat -program catenates a list of specified files on the -.I "standard output" . -It is usually used to look at the contents of a single file on the terminal, -to `cat a file' (1.8, 2.3). -.IP cd -The -.I cd -command is used to change the -.I "working directory" . -With no arguments, -.I cd -changes your -.I "working directory" -to be your -.I home -directory (2.4, 2.7). -.IP chdir -The -.I chdir -command is a synonym for -.I cd . -.I Cd -is usually used because it is easier to type. -.IP chsh -The -.I chsh -command is used to change the shell which you use on \s-2UNIX\s0. -By default, you use a different version of the shell -which resides in `/bin/sh'. -You can change your shell to `/bin/csh' by doing -.DS -chsh your-login-name /bin/csh -.DE -Thus I would do -.DS -chsh bill /bin/csh -.DE -It is only necessary to do this once. -The next time you log in to \s-2UNIX\s0 after doing this command, -you will be using -.I csh -rather than the shell in `/bin/sh' (1.9). -.IP cmp -.I Cmp -is a program which compares files. -It is usually used on binary files, or to see if two files are identical (3.6). -For comparing text files the program -.I diff , -described in `diff (1)' is used. -.IP command -A function performed by the system, either by the shell -(a builtin -.I command ) -or by a program residing in a file in -a directory within the \s-2UNIX\s0 system, is called a -.I command -(1.1). -.IP "command name" -.br -When a command is issued, it consists of a -.I "command name" , -which is the first word of the command, -followed by arguments. -The convention on \s-2UNIX\s0 is that the first word of a -command names the function to be performed (1.1). -.IP "command substitution" -.br -The replacement of a command enclosed in `\`' characters -by the text output by that command -is called -.I "command substitution" -(4.3). -.IP component -A part of a -.I pathname -between `/' characters is called a -.I component -of that -.I pathname . -A variable -which has multiple strings as value is said to have -several -.I component s; -each string is a -.I component -of the variable. -.IP continue -A builtin command which causes execution of the enclosing -.I foreach -or -.I while -loop to cycle prematurely. -Similar to the -.I continue -command in the programming language C (3.6). -.IP control- -Certain special characters, called -.I control -characters, are produced by holding down the \s-2CONTROL\s0 key -on your terminal and simultaneously pressing another character, much like -the \s-2SHIFT\s0 key is used to produce upper case characters. Thus -.I control- c -is produced by holding down the \s-2CONTROL\s0 key while pressing the -`c' key. Usually \s-2UNIX\s0 prints a caret (^) followed by the -corresponding letter when you type a -.I control -character (e.g. `^C' for -.I control- c -(1.8). -.IP "core\ dump" -When a program terminates abnormally, the system places an image -of its current state in a file named `core'. -This -.I "core dump" -can be examined with the system debugger `adb (1)' -or `sdb (1)' in order to determine what went wrong with the program (1.8). -If the shell produces a message of the form -.DS -Illegal instruction (core dumped) -.DE -(where `Illegal instruction' is only one of several possible -messages), you should report this to the author of the program -or a system administrator, -saving the `core' file. -.IP cp -The -.I cp -(copy) program is used to copy the contents of one file into another -file. -It is one of the most commonly used \s-2UNIX\s0 commands (1.6). -.IP csh -The name of the shell -program that this document describes. -.IP \&.cshrc -The file -.I \&.cshrc -in your -.I home -directory is read by each shell as it begins execution. -It is usually used to change the setting of the variable -.I path -and to set -.I alias -parameters which are to take effect globally (2.1). -.IP cwd -The -.I cwd -variable in the shell holds the -.I "absolute pathname" -of the current -.I "working directory" \&. -It is changed by the shell whenever your current -.I "working directory" -changes and should not be changed otherwise (2.2). -.IP date -The -.I date -command prints the current date and time (1.3). -.IP debugging -.I Debugging -is the process of correcting mistakes in programs and shell scripts. -The shell has several options and variables which may be used -to aid in shell -.I debugging -(4.4). -.IP default: -The label -.I default: -is used within shell -.I switch -statements, as it is in the C language -to label the code to be executed if none of the -.I case -labels matches the value switched on (3.7). -.IP \s-2DELETE\s0 -The -\s-2DELETE\s0 -or -\s-2RUBOUT\s0 -key on the terminal normally causes an interrupt to be sent to the current job. -Many users change the interrupt character to be ^C. -.IP detached -A command that continues running in the -.I background -after you logout is said to be -.I detached . -.IP diagnostic -An error message produced by a program is often referred to as a -.I diagnostic . -Most error messages are not written to the -.I "standard output" , -since that is often directed away from the terminal (1.3, 1.5). -Error messsages are instead written to the -.I "diagnostic output" -which may be directed away from the terminal, but usually is not. -Thus -.I diagnostics -will usually appear on the terminal (2.5). -.IP directory -A structure which contains files. -At any time you are in one particular -.I directory -whose names can be printed by the command -.I pwd . -The -.I chdir -command will change you to another -.I directory , -and make the files -in that -.I directory -visible. The -.I directory -in which you are when you first login is your -.I home -directory (1.1, 2.7). -.IP "directory\ stack" -The shell saves the names of previous -.I "working directories" -in the -.I "directory stack" -when you change your current -.I "working directory" -via the -.I pushd -command. The -.I "directory stack" -can be printed by using the -.I dirs -command, which includes your current -.I "working directory" -as the first directory name on the left (2.7). -.IP dirs -The -.I dirs -command prints the shell's -.I "directory stack" -(2.7). -.IP du -The -.I du -command is a program (described in `du (1)') which -prints the number of disk blocks is all directories below -and including your current -.I "working directory" -(2.6). -.IP echo -The -.I echo -command prints its arguments (1.6, 3.6). -.IP else -The -.I else -command is part of the `if-then-else-endif' control -command construct (3.6). -.IP endif -If an -.I if -statement is ended with the word -.I then , -all lines following the -.I if -up to a line starting with the word -.I endif -or -.I else -are executed if the condition between parentheses after the -.I if -is true (3.6). -.IP \s-2EOF\s0 -An -.I "end\f1-\fPof\f1-\fPfile" -is generated by the terminal by a control-d, -and whenever a command reads to the end of a file which -it has been given as input. -Commands receiving input from a -.I pipe -receive an -.I "end\f1-\fPof\f1-\fPfile" -when the command sending them input completes. -Most commands terminate when they receive an -.I "end\f1-\fPof\f1-\fPfile" . -The shell has an option to ignore -.I "end\f1-\fPof\f1-\fPfile" -from a terminal -input which may help you keep from logging out accidentally -by typing too many control-d's (1.1, 1.8, 3.8). -.IP escape -A character `\e' used to prevent the special meaning of a metacharacter -is said to -.I escape -the character from its special meaning. -Thus -.DS -echo \e* -.DE -will echo the character `*' while just -.DS -echo * -.DE -will echo the names of the file in the current directory. -In this example, \e -.I escape s -`*' (1.7). -There is also a non-printing character called -.I escape , -usually labelled -\s-2ESC\s0 -or -\s-2ALTMODE\s0 -on terminal keyboards. -Some older \s-2UNIX\s0 systems use this character to indicate that -output is to be -.I suspended . -Most systems use control-s to stop the output and control-q to start it. -.IP /etc/passwd -This file contains information about the accounts currently on the -system. -It consists of a line for each account with fields separated by -`:' characters (1.8). -You can look at this file by saying -.DS -cat /etc/passwd -.DE -The commands -.I finger -and -.I grep -are often used to search for information in this file. -See `finger (1)', `passwd(5)', and `grep (1)' for more details. -.IP exit -The -.I exit -command is used to force termination of a shell script, -and is built into the shell (3.9). -.IP "exit\ status" -A command which discovers a problem may reflect this back to the command -(such as a shell) which invoked (executed) it. -It does this by returning a non-zero number as its -.I "exit status" , -a status of zero being considered -`normal termination'. -The -.I exit -command can be used to force a shell command script to give a non-zero -.I "exit status" -(3.6). -.IP expansion -The replacement of strings in the shell input which contain metacharacters -by other strings is referred to as the process of -.I expansion . -Thus the replacement of the word `*' by a sorted list of files -in the current directory is a `filename expansion'. -Similarly the replacement of the characters `!!' by the text of -the last command is a `history expansion'. -.I Expansions -are also referred to as -.I substitutions -(1.6, 3.4, 4.2). -.IP expressions -.I Expressions -are used in the shell -to control the conditional structures used in the writing of shell -scripts and in calculating values for these scripts. -The operators available in shell -.I expressions -are those of the language -C (3.5). -.IP extension -Filenames often consist of a -.I base -name and an -.I extension -separated by the character `.'. -By convention, groups of related files often share the same -.I root -name. -Thus if `prog.c' were a C program, then the object file for this -program would be stored in `prog.o'. -Similarly a paper written with the -`\-me' -nroff macro package might be stored in -`paper.me' -while a formatted version of this paper might be kept in -`paper.out' and a list of spelling errors in -`paper.errs' (1.6). -.IP fg -The -.I "job control" -command -.I fg -is used to run a -.I background -or -.I suspended -job in the -.I foreground -(1.8, 2.6). -.IP filename -Each file in \s-2UNIX\s0 has a name consisting of up to 14 characters -and not including the character `/' which is used in -.I pathname -building. Most -.I filenames -do not begin with the character `.', and contain -only letters and digits with perhaps a `.' separating the -.I base -portion of the -.I filename -from an -.I extension -(1.6). -.IP "filename expansion" -.br -.I "Filename expansion" -uses the metacharacters `*', `?' and `[' and `]' -to provide a convenient mechanism for naming files. -Using -.I "filename expansion" -it is easy to name all the files in -the current directory, or all files which have a common -.I root -name. Other -.I "filename expansion" -mechanisms use the metacharacter `~' and allow -files in other users' directories to be named easily (1.6, 4.2). -.IP flag -Many \s-2UNIX\s0 commands accept arguments which are not the names -of files or other users but are used to modify the action of the commands. -These are referred to as -.I flag -options, and by convention consist of one or more letters preceded by -the character `\-' (1.2). -Thus the -.I ls -(list files) command has an option -`\-s' to list the sizes of files. -This is specified -.DS -ls \-s -.DE -.IP foreach -The -.I foreach -command is used in shell scripts and at the terminal to specify -repetition of a sequence of commands while the value of a certain -shell variable ranges through a specified list (3.6, 4.1). -.IP foreground -When commands are executing in the normal way such that the -shell is waiting for them to finish before prompting for another -command they are said to be -.I "foreground jobs" -or -.I "running in the foreground" \&. -This is as opposed to -.I background . -.I Foreground -jobs can be stopped by signals -from the terminal caused by typing different -control characters at the keyboard (1.8, 2.6). -.IP goto -The shell has a command -.I goto -used in shell scripts to transfer control to a given label (3.7). -.IP grep -The -.I grep -command searches through a list of argument files for a specified string. -Thus -.DS -grep bill /etc/passwd -.DE -will print each line in the file -.I "/etc/passwd" -which contains the string `bill'. -Actually, -.I grep -scans for -.I "regular expressions" -in the sense of the editors -`ed (1)' and `ex (1)'. -.I Grep -stands for -`globally find -.I "regular expression" -and print' (2.4). -.IP head -The -.I head -command prints the first few lines of one or more files. -If you have a bunch of files containing text which you are wondering -about it is sometimes useful to run -.I head -with these files as arguments. -This will usually show enough of what is in these files to let you decide -which you are interested in (1.5). -.br -.I Head -is also used to describe the part of a -.I pathname -before and including the last `/' character. The -.I tail -of a -.I pathname -is the part after the last `/'. The `:h' and `:t' modifiers allow the -.I head -or -.I tail -of a -.I pathname -stored in a shell variable to be used (3.6). -.IP history -The -.I history -mechanism of the shell allows previous commands to be repeated, -possibly after modification to correct typing mistakes or to change -the meaning of the command. -The shell has a -.I "history list" -where these commands are kept, and a -.I history -variable which controls how large this list is (2.3). -.IP "home\ directory" -.br -Each user has a -.I "home directory" , -which is given in your entry -in the password file, -.I /etc/passwd . -This is the directory which you are placed in when you first login. -The -.I cd -or -.I chdir -command with no arguments takes you back to this directory, whose -name is recorded in the shell variable -.I home . -You can also access the -.I "home directories" -of other users in forming -filenames using a -.I "filename expansion" -notation and the character `~' (1.6). -.IP if -A conditional command within the shell, the -.I if -command is used in shell command scripts to make decisions -about what course of action to take next (3.6). -.IP ignoreeof -Normally, your shell will exit, printing -`logout' -if you type a control-d at a prompt of `% '. -This is the way you usually log off the system. -You can -.I set -the -.I ignoreeof -variable if you wish in your -.I \&.login -file and then use the command -.I logout -to logout. -This is useful if you sometimes accidentally type too many control-d -characters, logging yourself off -(2.2). -.IP input -Many commands on \s-2UNIX\s0 take information from the terminal or from -files which they then act on. -This information is called -.I input . -Commands normally read for -.I input -from their -.I "standard input" -which is, by default, the terminal. -This -.I "standard input" -can be redirected from a file using a shell metanotation -with the character `<'. -Many commands will also read from a file specified as argument. -Commands placed in -.I pipelines -will read from the output of the previous -command in the -.I pipeline . -The leftmost command in a -.I pipeline -reads from the terminal if -you neither redirect its -.I input -nor give it a filename to use as -.I "standard input" . -Special mechanisms exist for supplying input to commands in shell -scripts (1.5, 3.8). -.IP interrupt -An -.I interrupt -is a signal to a program that is generated by typing ^C. (On older versions -of UNIX the \s-2RUBOUT\s0 or \s-2DELETE\s0 key were used for this purpose.) -It causes most programs to stop execution. -Certain programs, such as the shell and the editors, -handle an -.I interrupt -in special ways, usually by stopping what they -are doing and prompting for another command. -While the shell is executing another command and waiting for it -to finish, the shell does not listen to -.I interrupts. -The shell often wakes up when you hit -.I interrupt -because many commands -die when they receive an -.I interrupt -(1.8, 3.9). -.IP job -One or more commands -typed on the same input line separated by `|' or `;' characters -are run together and are called a -.I job \&. -Simple commands run by themselves without any `|' or `;' characters -are the simplest -.I jobs. -.I Jobs -are classified as -.I foreground , -.I background , -or -.I suspended -(2.6). -.IP "job\ control" -The builtin functions that control the execution of -jobs are called -.I "job control" -commands. These are -.I "bg, fg, stop, kill" -(2.6). -.IP "job\ number" -When each job -is started it is assigned a small number called a -.I "job number" -which is printed next to the job in the output of the -.I jobs -command. This number, preceded by a `%' character, can be used as an argument -to -.I "job control" -commands to indicate -a specific job (2.6). -.IP jobs -The -.I jobs -command prints a table showing -jobs that are either running in the -.I background -or are -.I suspended -(2.6). -.IP kill -A command which sends a -signal -to a job causing it to terminate (2.6). -.IP \&.login -The file -.I \&.login -in your -.I home -directory is read by the shell each time you login to \s-2UNIX\s0 -and the commands there are executed. -There are a number of commands which are usefully placed here, -especially -.I set -commands to the shell itself (2.1). -.IP "login\ shell" -The shell that is started on your terminal when you login is called -your -.I "login shell" . -It is different from other shells which you may run (e.g. on -shell scripts) -in that it reads the -.I \&.login -file before reading commands from the terminal and it reads the -.I \&.logout -file after you logout -(2.1). -.IP logout -The -.I logout -command causes a login shell to exit. -Normally, a login shell will exit when you hit control-d -generating an -.I end\f1-\fPof\f1-\fPfile, -but if you have set -.I ignoreeof -in you -.I \&.login -file then this will not work and you must use -.I logout -to log off the \s-2UNIX\s0 system (2.8). -.IP \&.logout -When you log off of \s-2UNIX\s0 the shell will execute commands from -the file -.I \&.logout -in your -.I home -directory after it prints `logout'. -.IP lpr -The command -.I lpr -is the line printer daemon. -The standard input of -.I lpr -spooled and printed on the \s-2UNIX\s0 line printer. -You can also give -.I lpr -a list of filenames as arguments to be printed. -It is most common to use -.I lpr -as the last component of a -.I pipeline -(2.3). -.IP ls -The -.I ls -(list files) command is one of the most commonly used \s-2UNIX\s0 -commands. -With no argument filenames it prints the names of the files in the -current directory. -It has a number of useful -.I flag -arguments, and can also be given the names of directories -as arguments, in which case it lists the names of the files in these -directories (1.2). -.IP mail -The -.I mail -program is used to send and receive messages from other \s-2UNIX\s0 -users (1.1, 2.1), whether they are logged on or not. -.IP make -The -.I make -command is used to maintain one or more related files and to -organize functions to be performed on these files. -In many ways -.I make -is easier to use, and more helpful than -shell command scripts (3.2). -.IP makefile -The file containing commands for -.I make -is called -.I makefile -or -.I Makefile -(3.2). -.IP manual -The -.I manual -often referred to is the -`\s-2UNIX\s0 manual'. -It contains 8 numbered sections with a description of each \s-2UNIX\s0 -program (section 1), system call (section 2), subroutine (section 3), -device (section 4), special data structure (section 5), game (section 6), -miscellaneous item (section 7) and system administration program (section 8). -There are also supplementary documents (tutorials and reference guides) -for individual programs which require explanation in more detail. -An online version of the -.I manual -is accessible through the -.I man -command. -Its documentation can be obtained online via -.DS -man man -.DE -If you can't decide what manual page to look in, try the -.I apropos (1) -command. -The supplementary documents are in subdirectories of /usr/doc. -.IP metacharacter -.br -Many characters which are neither letters nor digits have special meaning -either to the shell or to \s-2UNIX\s0. -These characters are called -.I metacharacters . -If it is necessary to place these characters in arguments to commands -without them having their special meaning then they must be -.I quoted . -An example of a -.I metacharacter -is the character `>' which is used -to indicate placement of output into a file. -For the purposes of the -.I history -mechanism, -most unquoted -.I metacharacters -form separate words (1.4). -The appendix to this user's manual lists the -.I metacharacters -in groups by their function. -.IP mkdir -The -.I mkdir -command is used to create a new directory. -.IP modifier -Substitutions with the -.I history -mechanism, keyed by the character `!' -or of variables using the metacharacter `$', are often subjected -to modifications, indicated by placing the character `:' after the -substitution and following this with the -.I modifier -itself. -The -.I "command substitution" -mechanism can also be used to perform modification in a similar way, -but this notation is less clear (3.6). -.IP more -The program -.I more -writes a file on your terminal allowing you to control how much text -is displayed at a time. -.I More -can move through the file screenful by screenful, line by line, -search forward for a string, or start again at the beginning of the file. -It is generally the easiest way of viewing a file (1.8). -.IP noclobber -The shell has a variable -.I noclobber -which may be set in the file -.I \&.login -to prevent accidental destruction of files by the `>' output redirection -metasyntax of the shell (2.2, 2.5). -.IP noglob -The shell variable -.I noglob -is set to suppress the -.I "filename expansion" -of arguments containing the metacharacters `~', `*', `?', `[' and `]' (3.6). -.IP notify -The -.I notify -command tells the shell to report on the termination of a specific -.I "background job" -at the exact time it occurs as opposed to waiting -until just before the next prompt to report the termination. -The -.I notify -variable, if set, causes the shell to always report the termination -of -.I background -jobs exactly when they occur (2.6). -.IP onintr -The -.I onintr -command is built into the shell and is used to control the action -of a shell command script when an -.I interrupt -signal is received (3.9). -.IP output -Many commands in \s-2UNIX\s0 result in some lines of text which are -called their -.I output. -This -.I output -is usually placed on what is known as the -.I "standard output" -which is normally connected to the user's terminal. -The shell has a syntax using the metacharacter `>' for redirecting -the -.I "standard output" -of a command to a file (1.3). -Using the -.I pipe -mechanism and the metacharacter `|' it is also possible for -the -.I "standard output" -of one command to become the -.I "standard input" -of another command (1.5). -Certain commands such as the line printer daemon -.I p -do not place their results on the -.I "standard output" -but rather in more -useful places such as on the line printer (2.3). -Similarly the -.I write -command places its output on another user's terminal rather than its -.I "standard output" -(2.3). -Commands also have a -.I "diagnostic output" -where they write their error messages. -Normally these go to the terminal even if the -.I "standard output" -has been sent to a file or another command, but it is possible -to direct error diagnostics along with -.I "standard output" -using a special metanotation (2.5). -.IP path -The shell has a variable -.I path -which gives the names of the directories in which it searches for -the commands which it is given. -It always checks first to see if the command it is given is -built into the shell. -If it is, then it need not search for the command as it can do it internally. -If the command is not builtin, then the shell searches for a file -with the name given in each of the directories in the -.I path -variable, left to right. -Since the normal definition of the -.I path -variable is -.DS -path (. /usr/ucb /bin /usr/bin) -.DE -the shell normally looks in the current directory, and then in -the standard system directories `/usr/ucb', `/bin' and `/usr/bin' for the named -command (2.2). -If the command cannot be found the shell will print an error diagnostic. -Scripts of shell commands will be executed using another shell to interpret -them if they have `execute' permission set. -This is normally true because a command of the form -.DS -chmod 755 script -.DE -was executed to turn this execute permission on (3.3). -If you add new commands to a directory in the -.I path , -you should issue -the command -.I rehash -(2.2). -.IP pathname -A list of names, separated by `/' characters, forms a -.I pathname. -Each -.I component, -between successive `/' characters, names a directory -in which the next -.I component -file resides. -.I Pathnames -which begin with the character `/' are interpreted relative -to the -.I root -directory in the file system. -Other -.I pathnames -are interpreted relative to the current directory -as reported by -.I pwd. -The last component of a -.I pathname -may name a directory, but -usually names a file. -.IP pipeline -A group of commands which are connected together, the -.I "standard output" -of each connected to the -.I "standard input" -of the next, -is called a -.I pipeline. -The -.I pipe -mechanism used to connect these commands is indicated by -the shell metacharacter `|' (1.5, 2.3). -.IP popd -The -.I popd -command changes the shell's -.I "working directory" -to the directory you most recently left using the -.I pushd -command. It returns to the directory without having to type its name, -forgetting the name of the current -.I "working directory" -before doing so (2.7). -.IP port -The part of a computer system to which each terminal is -connected is called a -.I port . -Usually the system has a fixed number of -.I ports , -some of which are connected to telephone lines -for dial-up access, and some of which are permanently -wired directly to specific terminals. -.IP pr -The -.I pr -command is used to prepare listings of the contents of files -with headers giving the name of the file and the date and -time at which the file was last modified (2.3). -.IP printenv -The -.I printenv -command is used -to print the current setting of variables in the environment -(2.8). -.IP process -An instance of a running program is called a -.I process -(2.6). -\s-2UNIX\s0 assigns each -.I process -a unique number when it is -started \- called the -.I "process number" . -.I "Process numbers" -can be used to stop individual -.I processes -using the -.I kill -or -.I stop -commands when the -.I processes -are part of a detached -.I background -job. -.IP program -Usually synonymous with -.I command ; -a binary file or shell command script -which performs a useful function is often -called a -.I program . -.IP prompt -Many programs will print a -.I prompt -on the terminal when they expect input. -Thus the editor -`ex (1)' will print a `:' when it expects input. -The shell -.I prompts -for input with `% ' and occasionally with `? ' when -reading commands from the terminal (1.1). -The shell has a variable -.I prompt -which may be set to a different value to change the shell's main -.I prompt . -This is mostly used when debugging the shell (2.8). -.IP pushd -The -.I pushd -command, which means `push directory', changes the shell's -.I "working directory" -and also remembers the current -.I "working directory" -before the change is made, allowing you to return to the same -directory via the -.I popd -command later without retyping its name (2.7). -.IP ps -The -.I ps -command is used to show the processes you are currently running. -Each process is shown with its unique process number, -an indication of the terminal name it is attached to, -an indication of the state of the process (whether it is running, -stopped, awaiting some event (sleeping), and whether it is swapped out), -and the amount of \s-2CPU\s0 time it has used so far. -The command is identified by printing some of the words used -when it was invoked (2.6). -Shells, such as the -.I csh -you use to run the -.I ps -command, are not normally shown in the output. -.IP pwd -The -.I pwd -command prints the full -.I pathname -of the current -.I "working directory" \&. -The -.I dirs -builtin command is usually a better and faster choice. -.IP quit -The -.I quit -signal, generated by a control-\e, -is used to terminate programs which are behaving unreasonably. -It normally produces a core image file (1.8). -.IP quotation -The process by which metacharacters are prevented their special -meaning, usually by using the character `\' in pairs, or by -using the character `\e', is referred to as -.I quotation -(1.7). -.IP redirection -The routing of input or output from or to a file is known -as -.I redirection -of input or output (1.3). -.IP rehash -The -.I rehash -command tells the shell to rebuild its internal table of which commands -are found in which directories in your -.I path . -This is necessary when a new program is installed in one of these -directories (2.8). -.IP "relative pathname" -.br -A -.I pathname -which does not begin with a `/' is called a -.I "relative pathname" -since it is interpreted -.I relative -to the current -.I "working directory" . -The first -.I component -of such a -.I pathname -refers to some file or directory in the -.I "working directory" , -and subsequent -.I components -between `/' characters refer to directories below the -.I "working directory" . -.I Pathnames -that are not -.I relative -are called -.I "absolute pathnames" -(1.6). -.IP repeat -The -.I repeat -command iterates another command a specified number of times. -.IP root -The directory -that is at the top of the entire directory structure is called the -.I root -directory since it is the `root' of the entire tree structure of -directories. The name used in -.I pathnames -to indicate the -.I root -is `/'. -.I Pathnames -starting with `/' are said to be -.I absolute -since they start at the -.I root -directory. -.I Root -is also used as the part of a -.I pathname -that is left after removing -the -.I extension . -See -.I filename -for a further explanation (1.6). -.IP \s-2RUBOUT\s0 -The \s-2RUBOUT\s0 or \s-2DELETE\s0 -key is often used to erase the previously typed character; some users -prefer the \s-2BACKSPACE\s0 for this purpose. On older versions of \s-2UNIX\s0 -this key served as the \s-2INTR\s0 character. -.IP "scratch file" -Files whose names begin with a `#' are referred to as -.I "scratch files" , -since they are automatically removed by the system after a couple of -days of non-use, or more frequently if disk space becomes tight (1.3). -.IP script -Sequences of shell commands placed in a file are called shell command -.I scripts . -It is often possible to perform simple tasks using these -.I scripts -without writing a program in a language such as C, by -using the shell to selectively run other programs (3.3, 3.10). -.IP set -The builtin -.I set -command is used to assign new values to shell variables -and to show the values of the current variables. -Many shell variables have special meaning to the shell itself. -Thus by using the -.I set -command the behavior of the shell can be affected (2.1). -.IP setenv -Variables in the environment `environ (5)' -can be changed by using the -.I setenv -builtin command (2.8). -The -.I printenv -command can be used to print the value of the variables in the environment. -.IP shell -A -.I shell -is a command language interpreter. -It is possible to write and run your own -.I shell , -as -.I shells -are no different than any other programs as far as the -system is concerned. -This manual deals with the details of one particular -.I shell , -called -.I csh. -.IP "shell script" -See -.I script -(3.3, 3.10). -.IP signal -A -.I signal -in \s-2UNIX\s0 is a short message that is sent to a running program -which causes something to happen to that process. -.I Signals -are sent either by typing special -.I control -characters on the keyboard or by using the -.I kill -or -.I stop -commands (1.8, 2.6). -.IP sort -The -.I sort -program sorts a sequence of lines in ways that can be controlled -by argument -.I flags -(1.5). -.IP source -The -.I source -command causes the shell to read commands from a specified file. -It is most useful for reading files such as -.I \&.cshrc -after changing them (2.8). -.IP "special character" -.br -See -.I metacharacters -and the -appendix to this manual. -.IP standard -We refer often to the -.I "standard input" -and -.I "standard output" -of commands. -See -.I input -and -.I output -(1.3, 3.8). -.IP status -A command normally returns a -.I status -when it finishes. -By convention a -.I status -of zero indicates that the command succeeded. -Commands may return non-zero -.I status -to indicate that some abnormal event has occurred. -The shell variable -.I status -is set to the -.I status -returned by the last command. -It is most useful in shell commmand scripts (3.6). -.IP stop -The -.I stop -command causes a -.I background -job to become -.I suspended -(2.6). -.IP string -A sequential group of characters taken together is called a -.I string \&. -.I Strings -can contain any printable characters (2.2). -.IP stty -The -.I stty -program changes certain parameters inside \s-2UNIX\s0 which determine -how your terminal is handled. See `stty (1)' for a complete description (2.6). -.IP substitution -The shell implements a number of -.I substitutions -where sequences indicated by metacharacters are replaced by other sequences. -Notable examples of this are history -.I substitution -keyed by the -metacharacter `!' and variable -.I substitution -indicated by `$'. -We also refer to -.I substitutions -as -.I expansions -(3.4). -.IP suspended -A job becomes -.I suspended -after a \s-2STOP\s0 signal is sent to it, either by typing a -.I control -z -at the terminal (for -.I foreground -jobs) or by using the -.I stop -command (for -.I background -jobs). When -.I suspended , -a job temporarily stops running until it is restarted by either the -.I fg -or -.I bg -command (2.6). -.IP switch -The -.I switch -command of the shell allows the shell -to select one of a number of sequences of commands based on an -argument string. -It is similar to the -.I switch -statement in the language C (3.7). -.IP termination -When a command which is being executed finishes we say it undergoes -.I termination -or -.I terminates. -Commands normally terminate when they read an -.I end\f1-\fPof\f1-\fPfile -from their -.I "standard input" . -It is also possible to terminate commands by sending them -an -.I interrupt -or -.I quit -signal (1.8). -The -.I kill -program terminates specified jobs (2.6). -.IP then -The -.I then -command is part of the shell's -`if-then-else-endif' control construct used in command scripts (3.6). -.IP time -The -.I time -command can be used to measure the amount of \s-2CPU\s0 -and real time consumed by a specified command as well -as the amount of disk i/o, memory utilized, and number -of page faults and swaps taken by the command (2.1, 2.8). -.IP tset -The -.I tset -program is used to set standard erase and kill characters -and to tell the system what kind of terminal you are using. -It is often invoked in a -.I \&.login -file (2.1). -.IP tty -The word -.I tty -is a historical abbreviation for `teletype' which is frequently used -in \s-2UNIX\s0 to indicate the -.I port -to which a given terminal is connected. The -.I tty -command will print the name of the -.I tty -or -.I port -to which your terminal is presently connected. -.IP unalias -The -.I unalias -command removes aliases (2.8). -.IP \s-2UNIX\s0 -\s-2UNIX\s0 is an operating system on which -.I csh -runs. -\s-2UNIX\s0 provides facilities which allow -.I csh -to invoke other programs such as editors and text formatters which -you may wish to use. -.IP unset -The -.I unset -command removes the definitions of shell variables (2.2, 2.8). -.IP "variable expansion" -.br -See -.I variables -and -.I expansion -(2.2, 3.4). -.IP variables -.I Variables -in -.I csh -hold one or more strings as value. -The most common use of -.I variables -is in controlling the behavior -of the shell. -See -.I path , -.I noclobber , -and -.I ignoreeof -for examples. -.I Variables -such as -.I argv -are also used in writing shell programs (shell command scripts) -(2.2). -.IP verbose -The -.I verbose -shell variable can be set to cause commands to be echoed -after they are history expanded. -This is often useful in debugging shell scripts. -The -.I verbose -variable is set by the shell's -.I \-v -command line option (3.10). -.IP wc -The -.I wc -program calculates the number of characters, words, and lines in the -files whose names are given as arguments (2.6). -.IP while -The -.I while -builtin control construct is used in shell command scripts (3.7). -.IP word -A sequence of characters which forms an argument to a command is called -a -.I word . -Many characters which are neither letters, digits, `\-', `.' nor `/' -form -.I words -all by themselves even if they are not surrounded -by blanks. -Any sequence of characters may be made into a -.I word -by surrounding it -with `\'' characters -except for the characters `\'' and `!' which require special treatment -(1.1). -This process of placing special characters in -.I words -without their special meaning is called -.I quoting . -.IP "working directory" -.br -At any given time you are in one particular directory, called -your -.I "working directory" . -This directory's name is printed by the -.I pwd -command and the files listed by -.I ls -are the ones in this directory. -You can change -.I "working directories" -using -.I chdir . -.IP write -The -.I write -command is an obsolete way of communicating with other users who are logged in to -\s-2UNIX\s0 (you have to take turns typing). If you are both using display -terminals, use \fItalk\fP(1), which is much more pleasant. diff --git a/bin/csh/USD.doc/tabs b/bin/csh/USD.doc/tabs deleted file mode 100644 index 196d437..0000000 --- a/bin/csh/USD.doc/tabs +++ /dev/null @@ -1,32 +0,0 @@ -.\"- -.\" Copyright (c) 1980, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)tabs 8.1 (Berkeley) 6/8/93 -.\" $FreeBSD$ -.\" -.ta 5n 10n 15n 20n 25n 30n 35n 40n 45n 50n 55n 60n 65n 70n 75n 80n |