From 818272eaa3207a24064aaeb409c6ea32c95e9acd Mon Sep 17 00:00:00 2001 From: mycroft Date: Tue, 20 Sep 1994 05:28:59 +0000 Subject: [PATCH] Import original 4.4-Lite version. --- bin/csh/USD.doc/Makefile | 7 + bin/csh/USD.doc/csh.1 | 1012 ++++++++++++++++++++++ bin/csh/USD.doc/csh.2 | 1305 +++++++++++++++++++++++++++++ bin/csh/USD.doc/csh.3 | 650 ++++++++++++++ bin/csh/USD.doc/csh.4 | 178 ++++ bin/csh/USD.doc/csh.g | 1721 ++++++++++++++++++++++++++++++++++++++ bin/csh/USD.doc/tabs | 34 + 7 files changed, 4907 insertions(+) create mode 100644 bin/csh/USD.doc/Makefile create mode 100644 bin/csh/USD.doc/csh.1 create mode 100644 bin/csh/USD.doc/csh.2 create mode 100644 bin/csh/USD.doc/csh.3 create mode 100644 bin/csh/USD.doc/csh.4 create mode 100644 bin/csh/USD.doc/csh.g create mode 100644 bin/csh/USD.doc/tabs diff --git a/bin/csh/USD.doc/Makefile b/bin/csh/USD.doc/Makefile new file mode 100644 index 000000000000..e73be633d116 --- /dev/null +++ b/bin/csh/USD.doc/Makefile @@ -0,0 +1,7 @@ +# @(#)Makefile 8.1 (Berkeley) 8/14/93 + +DIR= usd/04.csh +SRCS= tabs csh.1 csh.2 csh.3 csh.4 csh.a csh.g +MACROS= -ms + +.include diff --git a/bin/csh/USD.doc/csh.1 b/bin/csh/USD.doc/csh.1 new file mode 100644 index 000000000000..9b8e39491e21 --- /dev/null +++ b/bin/csh/USD.doc/csh.1 @@ -0,0 +1,1012 @@ +.\" 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. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 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 +.\" +.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 as 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 an 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 new file mode 100644 index 000000000000..610105c829fa --- /dev/null +++ b/bin/csh/USD.doc/csh.2 @@ -0,0 +1,1305 @@ +.\" 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. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 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 +.\" +.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 backgound 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 backgound. 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 backgound 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 backgound 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 backgound 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 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 new file mode 100644 index 000000000000..cf8af73b0cc4 --- /dev/null +++ b/bin/csh/USD.doc/csh.3 @@ -0,0 +1,650 @@ +.\" 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. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 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 +.\" +.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 new file mode 100644 index 000000000000..ee862df07b93 --- /dev/null +++ b/bin/csh/USD.doc/csh.4 @@ -0,0 +1,178 @@ +.\" 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. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 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 +.\" +.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.g b/bin/csh/USD.doc/csh.g new file mode 100644 index 000000000000..0641769047a0 --- /dev/null +++ b/bin/csh/USD.doc/csh.g @@ -0,0 +1,1721 @@ +.\" 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. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 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 +.\" +.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 an 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 an 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 filesystem. +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 new file mode 100644 index 000000000000..9d274a14caf8 --- /dev/null +++ b/bin/csh/USD.doc/tabs @@ -0,0 +1,34 @@ +.\" 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. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 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 +.\" +.ta 5n 10n 15n 20n 25n 30n 35n 40n 45n 50n 55n 60n 65n 70n 75n 80n