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diff --git a/share/doc/usd/04.csh/csh.g b/share/doc/usd/04.csh/csh.g new file mode 100644 index 0000000..ba1b161 --- /dev/null +++ b/share/doc/usd/04.csh/csh.g @@ -0,0 +1,1719 @@ +.\"- +.\" Copyright (c) 1980, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)csh.g 8.1 (Berkeley) 6/8/93 +.\" $FreeBSD$ +.\" +.SH +Glossary +.PP +This glossary lists the most important terms introduced in the +introduction to the +shell and gives references to sections of the shell +document for further information about them. +References of the form +`pr (1)' +indicate that the command +.I pr +is in the \s-2UNIX\s0 User Reference manual in section 1. +You can look at an online copy of its manual page by doing +.DS +man 1 pr +.DE +References of the form (2.5) +indicate that more information can be found in section 2.5 of this +manual. +.IP \&\fB.\fR 15n +Your current directory has the name `.' as well as the name printed +by the command +.I pwd; +see also +.I dirs. +The current directory `.' is usually the first +.I component +of the search path contained in the variable +.I path , +thus commands which are in `.' are found first (2.2). +The character `.' is also used in separating +.I components +of filenames +(1.6). +The character `.' at the beginning of a +.I component +of a +.I pathname +is treated specially and not matched by the +.I "filename expansion" +metacharacters `?', `*', and `[' `]' pairs (1.6). +.IP \&\fB..\fR +Each directory has a file `..' in it which is a reference to its +parent directory. +After changing into the directory with +.I chdir , +i.e. +.DS +chdir paper +.DE +you can return to the parent directory by doing +.DS +chdir .. +.DE +The current directory is printed by +.I pwd +(2.7). +.IP a.out +Compilers which create executable images create them, by default, in the +file +.I a.out. +for historical reasons (2.3). +.IP "absolute pathname" +.br +A +.I pathname +which begins with a `/' is +.I absolute +since it specifies the +.I path +of directories from the beginning +of the entire directory system \- called the +.I root +directory. +.I Pathname s +which are not +.I absolute +are called +.I relative +(see definition of +.I "relative pathname" ) +(1.6). +.IP alias +An +.I alias +specifies a shorter or different name for a \s-2UNIX\s0 +command, or a transformation on a command to be performed in +the shell. +The shell has a command +.I alias +which establishes +.I aliases +and can print their current values. +The command +.I unalias +is used to remove +.I aliases +(2.4). +.IP argument +Commands in \s-2UNIX\s0 receive a list of +.I argument +words. +Thus the command +.DS +echo a b c +.DE +consists of the +.I "command name" +`echo' and three +.I argument +words `a', `b' and `c'. +The set of +.I arguments +after the +.I "command name" +is said to be the +.I "argument list" +of the command (1.1). +.IP argv +The list of arguments to a command written in the shell language +(a shell script or shell procedure) is stored in a variable called +.I argv +within the shell. +This name is taken from the conventional name in the +C programming language (3.4). +.IP background +Commands started without waiting for them to complete are called +.I background +commands (2.6). +.IP base +A filename is sometimes thought of as consisting of a +.I base +part, before any `.' character, and an +.I extension +\- the part after +the `.'. See +.I filename +and +.I extension +(1.6) and basename (1). +.IP bg +The +.I bg +command causes a +.I suspended +job to continue execution in the +.I background +(2.6). +.IP bin +A directory containing binaries of programs and shell scripts to be +executed is typically called a +.I bin +directory. +The standard system +.I bin +directories are `/bin' containing the most +heavily used commands and `/usr/bin' which contains most other user +programs. +Programs developed at UC Berkeley live in `/usr/ucb', while locally +written programs live in `/usr/local'. Games are kept in the directory +`/usr/games'. +You can place binaries in any directory. +If you wish to execute them often, the name of the directories +should be a +.I component +of the variable +.I path . +.IP break +.I Break +is a builtin command used to exit from loops within the control +structure of the shell (3.7). +.IP breaksw +The +.I breaksw +builtin command is used to exit from a +.I switch +control structure, like a +.I break +exits from loops (3.7). +.IP builtin +A command executed directly by the shell is called a +.I builtin +command. +Most commands in \s-2UNIX\s0 are not built into the shell, +but rather exist as files in +.I bin +directories. +These commands are accessible because the directories in which +they reside are named in the +.I path +variable. +.IP case +A +.I case +command is used as a label in a +.I switch +statement in the shell's control structure, similar to that of the +language C. +Details are given in the shell documentation `csh (1)' (3.7). +.IP cat +The +.I cat +program catenates a list of specified files on the +.I "standard output" . +It is usually used to look at the contents of a single file on the terminal, +to `cat a file' (1.8, 2.3). +.IP cd +The +.I cd +command is used to change the +.I "working directory" . +With no arguments, +.I cd +changes your +.I "working directory" +to be your +.I home +directory (2.4, 2.7). +.IP chdir +The +.I chdir +command is a synonym for +.I cd . +.I Cd +is usually used because it is easier to type. +.IP chsh +The +.I chsh +command is used to change the shell which you use on \s-2UNIX\s0. +By default, you use a different version of the shell +which resides in `/bin/sh'. +You can change your shell to `/bin/csh' by doing +.DS +chsh your-login-name /bin/csh +.DE +Thus I would do +.DS +chsh bill /bin/csh +.DE +It is only necessary to do this once. +The next time you log in to \s-2UNIX\s0 after doing this command, +you will be using +.I csh +rather than the shell in `/bin/sh' (1.9). +.IP cmp +.I Cmp +is a program which compares files. +It is usually used on binary files, or to see if two files are identical (3.6). +For comparing text files the program +.I diff , +described in `diff (1)' is used. +.IP command +A function performed by the system, either by the shell +(a builtin +.I command ) +or by a program residing in a file in +a directory within the \s-2UNIX\s0 system, is called a +.I command +(1.1). +.IP "command name" +.br +When a command is issued, it consists of a +.I "command name" , +which is the first word of the command, +followed by arguments. +The convention on \s-2UNIX\s0 is that the first word of a +command names the function to be performed (1.1). +.IP "command substitution" +.br +The replacement of a command enclosed in `\`' characters +by the text output by that command +is called +.I "command substitution" +(4.3). +.IP component +A part of a +.I pathname +between `/' characters is called a +.I component +of that +.I pathname . +A variable +which has multiple strings as value is said to have +several +.I component s; +each string is a +.I component +of the variable. +.IP continue +A builtin command which causes execution of the enclosing +.I foreach +or +.I while +loop to cycle prematurely. +Similar to the +.I continue +command in the programming language C (3.6). +.IP control- +Certain special characters, called +.I control +characters, are produced by holding down the \s-2CONTROL\s0 key +on your terminal and simultaneously pressing another character, much like +the \s-2SHIFT\s0 key is used to produce upper case characters. Thus +.I control- c +is produced by holding down the \s-2CONTROL\s0 key while pressing the +`c' key. Usually \s-2UNIX\s0 prints a caret (^) followed by the +corresponding letter when you type a +.I control +character (e.g. `^C' for +.I control- c +(1.8). +.IP "core\ dump" +When a program terminates abnormally, the system places an image +of its current state in a file named `core'. +This +.I "core dump" +can be examined with the system debugger `adb (1)' +or `sdb (1)' in order to determine what went wrong with the program (1.8). +If the shell produces a message of the form +.DS +Illegal instruction (core dumped) +.DE +(where `Illegal instruction' is only one of several possible +messages), you should report this to the author of the program +or a system administrator, +saving the `core' file. +.IP cp +The +.I cp +(copy) program is used to copy the contents of one file into another +file. +It is one of the most commonly used \s-2UNIX\s0 commands (1.6). +.IP csh +The name of the shell +program that this document describes. +.IP \&.cshrc +The file +.I \&.cshrc +in your +.I home +directory is read by each shell as it begins execution. +It is usually used to change the setting of the variable +.I path +and to set +.I alias +parameters which are to take effect globally (2.1). +.IP cwd +The +.I cwd +variable in the shell holds the +.I "absolute pathname" +of the current +.I "working directory" \&. +It is changed by the shell whenever your current +.I "working directory" +changes and should not be changed otherwise (2.2). +.IP date +The +.I date +command prints the current date and time (1.3). +.IP debugging +.I Debugging +is the process of correcting mistakes in programs and shell scripts. +The shell has several options and variables which may be used +to aid in shell +.I debugging +(4.4). +.IP default: +The label +.I default: +is used within shell +.I switch +statements, as it is in the C language +to label the code to be executed if none of the +.I case +labels matches the value switched on (3.7). +.IP \s-2DELETE\s0 +The +\s-2DELETE\s0 +or +\s-2RUBOUT\s0 +key on the terminal normally causes an interrupt to be sent to the current job. +Many users change the interrupt character to be ^C. +.IP detached +A command that continues running in the +.I background +after you logout is said to be +.I detached . +.IP diagnostic +An error message produced by a program is often referred to as a +.I diagnostic . +Most error messages are not written to the +.I "standard output" , +since that is often directed away from the terminal (1.3, 1.5). +Error messsages are instead written to the +.I "diagnostic output" +which may be directed away from the terminal, but usually is not. +Thus +.I diagnostics +will usually appear on the terminal (2.5). +.IP directory +A structure which contains files. +At any time you are in one particular +.I directory +whose names can be printed by the command +.I pwd . +The +.I chdir +command will change you to another +.I directory , +and make the files +in that +.I directory +visible. The +.I directory +in which you are when you first login is your +.I home +directory (1.1, 2.7). +.IP "directory\ stack" +The shell saves the names of previous +.I "working directories" +in the +.I "directory stack" +when you change your current +.I "working directory" +via the +.I pushd +command. The +.I "directory stack" +can be printed by using the +.I dirs +command, which includes your current +.I "working directory" +as the first directory name on the left (2.7). +.IP dirs +The +.I dirs +command prints the shell's +.I "directory stack" +(2.7). +.IP du +The +.I du +command is a program (described in `du (1)') which +prints the number of disk blocks is all directories below +and including your current +.I "working directory" +(2.6). +.IP echo +The +.I echo +command prints its arguments (1.6, 3.6). +.IP else +The +.I else +command is part of the `if-then-else-endif' control +command construct (3.6). +.IP endif +If an +.I if +statement is ended with the word +.I then , +all lines following the +.I if +up to a line starting with the word +.I endif +or +.I else +are executed if the condition between parentheses after the +.I if +is true (3.6). +.IP \s-2EOF\s0 +An +.I "end\f1-\fPof\f1-\fPfile" +is generated by the terminal by a control-d, +and whenever a command reads to the end of a file which +it has been given as input. +Commands receiving input from a +.I pipe +receive an +.I "end\f1-\fPof\f1-\fPfile" +when the command sending them input completes. +Most commands terminate when they receive an +.I "end\f1-\fPof\f1-\fPfile" . +The shell has an option to ignore +.I "end\f1-\fPof\f1-\fPfile" +from a terminal +input which may help you keep from logging out accidentally +by typing too many control-d's (1.1, 1.8, 3.8). +.IP escape +A character `\e' used to prevent the special meaning of a metacharacter +is said to +.I escape +the character from its special meaning. +Thus +.DS +echo \e* +.DE +will echo the character `*' while just +.DS +echo * +.DE +will echo the names of the file in the current directory. +In this example, \e +.I escape s +`*' (1.7). +There is also a non-printing character called +.I escape , +usually labelled +\s-2ESC\s0 +or +\s-2ALTMODE\s0 +on terminal keyboards. +Some older \s-2UNIX\s0 systems use this character to indicate that +output is to be +.I suspended . +Most systems use control-s to stop the output and control-q to start it. +.IP /etc/passwd +This file contains information about the accounts currently on the +system. +It consists of a line for each account with fields separated by +`:' characters (1.8). +You can look at this file by saying +.DS +cat /etc/passwd +.DE +The commands +.I finger +and +.I grep +are often used to search for information in this file. +See `finger (1)', `passwd(5)', and `grep (1)' for more details. +.IP exit +The +.I exit +command is used to force termination of a shell script, +and is built into the shell (3.9). +.IP "exit\ status" +A command which discovers a problem may reflect this back to the command +(such as a shell) which invoked (executed) it. +It does this by returning a non-zero number as its +.I "exit status" , +a status of zero being considered +`normal termination'. +The +.I exit +command can be used to force a shell command script to give a non-zero +.I "exit status" +(3.6). +.IP expansion +The replacement of strings in the shell input which contain metacharacters +by other strings is referred to as the process of +.I expansion . +Thus the replacement of the word `*' by a sorted list of files +in the current directory is a `filename expansion'. +Similarly the replacement of the characters `!!' by the text of +the last command is a `history expansion'. +.I Expansions +are also referred to as +.I substitutions +(1.6, 3.4, 4.2). +.IP expressions +.I Expressions +are used in the shell +to control the conditional structures used in the writing of shell +scripts and in calculating values for these scripts. +The operators available in shell +.I expressions +are those of the language +C (3.5). +.IP extension +Filenames often consist of a +.I base +name and an +.I extension +separated by the character `.'. +By convention, groups of related files often share the same +.I root +name. +Thus if `prog.c' were a C program, then the object file for this +program would be stored in `prog.o'. +Similarly a paper written with the +`\-me' +nroff macro package might be stored in +`paper.me' +while a formatted version of this paper might be kept in +`paper.out' and a list of spelling errors in +`paper.errs' (1.6). +.IP fg +The +.I "job control" +command +.I fg +is used to run a +.I background +or +.I suspended +job in the +.I foreground +(1.8, 2.6). +.IP filename +Each file in \s-2UNIX\s0 has a name consisting of up to 14 characters +and not including the character `/' which is used in +.I pathname +building. Most +.I filenames +do not begin with the character `.', and contain +only letters and digits with perhaps a `.' separating the +.I base +portion of the +.I filename +from an +.I extension +(1.6). +.IP "filename expansion" +.br +.I "Filename expansion" +uses the metacharacters `*', `?' and `[' and `]' +to provide a convenient mechanism for naming files. +Using +.I "filename expansion" +it is easy to name all the files in +the current directory, or all files which have a common +.I root +name. Other +.I "filename expansion" +mechanisms use the metacharacter `~' and allow +files in other users' directories to be named easily (1.6, 4.2). +.IP flag +Many \s-2UNIX\s0 commands accept arguments which are not the names +of files or other users but are used to modify the action of the commands. +These are referred to as +.I flag +options, and by convention consist of one or more letters preceded by +the character `\-' (1.2). +Thus the +.I ls +(list files) command has an option +`\-s' to list the sizes of files. +This is specified +.DS +ls \-s +.DE +.IP foreach +The +.I foreach +command is used in shell scripts and at the terminal to specify +repetition of a sequence of commands while the value of a certain +shell variable ranges through a specified list (3.6, 4.1). +.IP foreground +When commands are executing in the normal way such that the +shell is waiting for them to finish before prompting for another +command they are said to be +.I "foreground jobs" +or +.I "running in the foreground" \&. +This is as opposed to +.I background . +.I Foreground +jobs can be stopped by signals +from the terminal caused by typing different +control characters at the keyboard (1.8, 2.6). +.IP goto +The shell has a command +.I goto +used in shell scripts to transfer control to a given label (3.7). +.IP grep +The +.I grep +command searches through a list of argument files for a specified string. +Thus +.DS +grep bill /etc/passwd +.DE +will print each line in the file +.I "/etc/passwd" +which contains the string `bill'. +Actually, +.I grep +scans for +.I "regular expressions" +in the sense of the editors +`ed (1)' and `ex (1)'. +.I Grep +stands for +`globally find +.I "regular expression" +and print' (2.4). +.IP head +The +.I head +command prints the first few lines of one or more files. +If you have a bunch of files containing text which you are wondering +about it is sometimes useful to run +.I head +with these files as arguments. +This will usually show enough of what is in these files to let you decide +which you are interested in (1.5). +.br +.I Head +is also used to describe the part of a +.I pathname +before and including the last `/' character. The +.I tail +of a +.I pathname +is the part after the last `/'. The `:h' and `:t' modifiers allow the +.I head +or +.I tail +of a +.I pathname +stored in a shell variable to be used (3.6). +.IP history +The +.I history +mechanism of the shell allows previous commands to be repeated, +possibly after modification to correct typing mistakes or to change +the meaning of the command. +The shell has a +.I "history list" +where these commands are kept, and a +.I history +variable which controls how large this list is (2.3). +.IP "home\ directory" +.br +Each user has a +.I "home directory" , +which is given in your entry +in the password file, +.I /etc/passwd . +This is the directory which you are placed in when you first login. +The +.I cd +or +.I chdir +command with no arguments takes you back to this directory, whose +name is recorded in the shell variable +.I home . +You can also access the +.I "home directories" +of other users in forming +filenames using a +.I "filename expansion" +notation and the character `~' (1.6). +.IP if +A conditional command within the shell, the +.I if +command is used in shell command scripts to make decisions +about what course of action to take next (3.6). +.IP ignoreeof +Normally, your shell will exit, printing +`logout' +if you type a control-d at a prompt of `% '. +This is the way you usually log off the system. +You can +.I set +the +.I ignoreeof +variable if you wish in your +.I \&.login +file and then use the command +.I logout +to logout. +This is useful if you sometimes accidentally type too many control-d +characters, logging yourself off +(2.2). +.IP input +Many commands on \s-2UNIX\s0 take information from the terminal or from +files which they then act on. +This information is called +.I input . +Commands normally read for +.I input +from their +.I "standard input" +which is, by default, the terminal. +This +.I "standard input" +can be redirected from a file using a shell metanotation +with the character `<'. +Many commands will also read from a file specified as argument. +Commands placed in +.I pipelines +will read from the output of the previous +command in the +.I pipeline . +The leftmost command in a +.I pipeline +reads from the terminal if +you neither redirect its +.I input +nor give it a filename to use as +.I "standard input" . +Special mechanisms exist for supplying input to commands in shell +scripts (1.5, 3.8). +.IP interrupt +An +.I interrupt +is a signal to a program that is generated by typing ^C. (On older versions +of UNIX the \s-2RUBOUT\s0 or \s-2DELETE\s0 key were used for this purpose.) +It causes most programs to stop execution. +Certain programs, such as the shell and the editors, +handle an +.I interrupt +in special ways, usually by stopping what they +are doing and prompting for another command. +While the shell is executing another command and waiting for it +to finish, the shell does not listen to +.I interrupts. +The shell often wakes up when you hit +.I interrupt +because many commands +die when they receive an +.I interrupt +(1.8, 3.9). +.IP job +One or more commands +typed on the same input line separated by `|' or `;' characters +are run together and are called a +.I job \&. +Simple commands run by themselves without any `|' or `;' characters +are the simplest +.I jobs. +.I Jobs +are classified as +.I foreground , +.I background , +or +.I suspended +(2.6). +.IP "job\ control" +The builtin functions that control the execution of +jobs are called +.I "job control" +commands. These are +.I "bg, fg, stop, kill" +(2.6). +.IP "job\ number" +When each job +is started it is assigned a small number called a +.I "job number" +which is printed next to the job in the output of the +.I jobs +command. This number, preceded by a `%' character, can be used as an argument +to +.I "job control" +commands to indicate +a specific job (2.6). +.IP jobs +The +.I jobs +command prints a table showing +jobs that are either running in the +.I background +or are +.I suspended +(2.6). +.IP kill +A command which sends a +signal +to a job causing it to terminate (2.6). +.IP \&.login +The file +.I \&.login +in your +.I home +directory is read by the shell each time you login to \s-2UNIX\s0 +and the commands there are executed. +There are a number of commands which are usefully placed here, +especially +.I set +commands to the shell itself (2.1). +.IP "login\ shell" +The shell that is started on your terminal when you login is called +your +.I "login shell" . +It is different from other shells which you may run (e.g. on +shell scripts) +in that it reads the +.I \&.login +file before reading commands from the terminal and it reads the +.I \&.logout +file after you logout +(2.1). +.IP logout +The +.I logout +command causes a login shell to exit. +Normally, a login shell will exit when you hit control-d +generating an +.I end\f1-\fPof\f1-\fPfile, +but if you have set +.I ignoreeof +in you +.I \&.login +file then this will not work and you must use +.I logout +to log off the \s-2UNIX\s0 system (2.8). +.IP \&.logout +When you log off of \s-2UNIX\s0 the shell will execute commands from +the file +.I \&.logout +in your +.I home +directory after it prints `logout'. +.IP lpr +The command +.I lpr +is the line printer daemon. +The standard input of +.I lpr +spooled and printed on the \s-2UNIX\s0 line printer. +You can also give +.I lpr +a list of filenames as arguments to be printed. +It is most common to use +.I lpr +as the last component of a +.I pipeline +(2.3). +.IP ls +The +.I ls +(list files) command is one of the most commonly used \s-2UNIX\s0 +commands. +With no argument filenames it prints the names of the files in the +current directory. +It has a number of useful +.I flag +arguments, and can also be given the names of directories +as arguments, in which case it lists the names of the files in these +directories (1.2). +.IP mail +The +.I mail +program is used to send and receive messages from other \s-2UNIX\s0 +users (1.1, 2.1), whether they are logged on or not. +.IP make +The +.I make +command is used to maintain one or more related files and to +organize functions to be performed on these files. +In many ways +.I make +is easier to use, and more helpful than +shell command scripts (3.2). +.IP makefile +The file containing commands for +.I make +is called +.I makefile +or +.I Makefile +(3.2). +.IP manual +The +.I manual +often referred to is the +`\s-2UNIX\s0 manual'. +It contains 8 numbered sections with a description of each \s-2UNIX\s0 +program (section 1), system call (section 2), subroutine (section 3), +device (section 4), special data structure (section 5), game (section 6), +miscellaneous item (section 7) and system administration program (section 8). +There are also supplementary documents (tutorials and reference guides) +for individual programs which require explanation in more detail. +An online version of the +.I manual +is accessible through the +.I man +command. +Its documentation can be obtained online via +.DS +man man +.DE +If you can't decide what manual page to look in, try the +.I apropos (1) +command. +The supplementary documents are in subdirectories of /usr/doc. +.IP metacharacter +.br +Many characters which are neither letters nor digits have special meaning +either to the shell or to \s-2UNIX\s0. +These characters are called +.I metacharacters . +If it is necessary to place these characters in arguments to commands +without them having their special meaning then they must be +.I quoted . +An example of a +.I metacharacter +is the character `>' which is used +to indicate placement of output into a file. +For the purposes of the +.I history +mechanism, +most unquoted +.I metacharacters +form separate words (1.4). +The appendix to this user's manual lists the +.I metacharacters +in groups by their function. +.IP mkdir +The +.I mkdir +command is used to create a new directory. +.IP modifier +Substitutions with the +.I history +mechanism, keyed by the character `!' +or of variables using the metacharacter `$', are often subjected +to modifications, indicated by placing the character `:' after the +substitution and following this with the +.I modifier +itself. +The +.I "command substitution" +mechanism can also be used to perform modification in a similar way, +but this notation is less clear (3.6). +.IP more +The program +.I more +writes a file on your terminal allowing you to control how much text +is displayed at a time. +.I More +can move through the file screenful by screenful, line by line, +search forward for a string, or start again at the beginning of the file. +It is generally the easiest way of viewing a file (1.8). +.IP noclobber +The shell has a variable +.I noclobber +which may be set in the file +.I \&.login +to prevent accidental destruction of files by the `>' output redirection +metasyntax of the shell (2.2, 2.5). +.IP noglob +The shell variable +.I noglob +is set to suppress the +.I "filename expansion" +of arguments containing the metacharacters `~', `*', `?', `[' and `]' (3.6). +.IP notify +The +.I notify +command tells the shell to report on the termination of a specific +.I "background job" +at the exact time it occurs as opposed to waiting +until just before the next prompt to report the termination. +The +.I notify +variable, if set, causes the shell to always report the termination +of +.I background +jobs exactly when they occur (2.6). +.IP onintr +The +.I onintr +command is built into the shell and is used to control the action +of a shell command script when an +.I interrupt +signal is received (3.9). +.IP output +Many commands in \s-2UNIX\s0 result in some lines of text which are +called their +.I output. +This +.I output +is usually placed on what is known as the +.I "standard output" +which is normally connected to the user's terminal. +The shell has a syntax using the metacharacter `>' for redirecting +the +.I "standard output" +of a command to a file (1.3). +Using the +.I pipe +mechanism and the metacharacter `|' it is also possible for +the +.I "standard output" +of one command to become the +.I "standard input" +of another command (1.5). +Certain commands such as the line printer daemon +.I p +do not place their results on the +.I "standard output" +but rather in more +useful places such as on the line printer (2.3). +Similarly the +.I write +command places its output on another user's terminal rather than its +.I "standard output" +(2.3). +Commands also have a +.I "diagnostic output" +where they write their error messages. +Normally these go to the terminal even if the +.I "standard output" +has been sent to a file or another command, but it is possible +to direct error diagnostics along with +.I "standard output" +using a special metanotation (2.5). +.IP path +The shell has a variable +.I path +which gives the names of the directories in which it searches for +the commands which it is given. +It always checks first to see if the command it is given is +built into the shell. +If it is, then it need not search for the command as it can do it internally. +If the command is not builtin, then the shell searches for a file +with the name given in each of the directories in the +.I path +variable, left to right. +Since the normal definition of the +.I path +variable is +.DS +path (. /usr/ucb /bin /usr/bin) +.DE +the shell normally looks in the current directory, and then in +the standard system directories `/usr/ucb', `/bin' and `/usr/bin' for the named +command (2.2). +If the command cannot be found the shell will print an error diagnostic. +Scripts of shell commands will be executed using another shell to interpret +them if they have `execute' permission set. +This is normally true because a command of the form +.DS +chmod 755 script +.DE +was executed to turn this execute permission on (3.3). +If you add new commands to a directory in the +.I path , +you should issue +the command +.I rehash +(2.2). +.IP pathname +A list of names, separated by `/' characters, forms a +.I pathname. +Each +.I component, +between successive `/' characters, names a directory +in which the next +.I component +file resides. +.I Pathnames +which begin with the character `/' are interpreted relative +to the +.I root +directory in the file system. +Other +.I pathnames +are interpreted relative to the current directory +as reported by +.I pwd. +The last component of a +.I pathname +may name a directory, but +usually names a file. +.IP pipeline +A group of commands which are connected together, the +.I "standard output" +of each connected to the +.I "standard input" +of the next, +is called a +.I pipeline. +The +.I pipe +mechanism used to connect these commands is indicated by +the shell metacharacter `|' (1.5, 2.3). +.IP popd +The +.I popd +command changes the shell's +.I "working directory" +to the directory you most recently left using the +.I pushd +command. It returns to the directory without having to type its name, +forgetting the name of the current +.I "working directory" +before doing so (2.7). +.IP port +The part of a computer system to which each terminal is +connected is called a +.I port . +Usually the system has a fixed number of +.I ports , +some of which are connected to telephone lines +for dial-up access, and some of which are permanently +wired directly to specific terminals. +.IP pr +The +.I pr +command is used to prepare listings of the contents of files +with headers giving the name of the file and the date and +time at which the file was last modified (2.3). +.IP printenv +The +.I printenv +command is used +to print the current setting of variables in the environment +(2.8). +.IP process +An instance of a running program is called a +.I process +(2.6). +\s-2UNIX\s0 assigns each +.I process +a unique number when it is +started \- called the +.I "process number" . +.I "Process numbers" +can be used to stop individual +.I processes +using the +.I kill +or +.I stop +commands when the +.I processes +are part of a detached +.I background +job. +.IP program +Usually synonymous with +.I command ; +a binary file or shell command script +which performs a useful function is often +called a +.I program . +.IP prompt +Many programs will print a +.I prompt +on the terminal when they expect input. +Thus the editor +`ex (1)' will print a `:' when it expects input. +The shell +.I prompts +for input with `% ' and occasionally with `? ' when +reading commands from the terminal (1.1). +The shell has a variable +.I prompt +which may be set to a different value to change the shell's main +.I prompt . +This is mostly used when debugging the shell (2.8). +.IP pushd +The +.I pushd +command, which means `push directory', changes the shell's +.I "working directory" +and also remembers the current +.I "working directory" +before the change is made, allowing you to return to the same +directory via the +.I popd +command later without retyping its name (2.7). +.IP ps +The +.I ps +command is used to show the processes you are currently running. +Each process is shown with its unique process number, +an indication of the terminal name it is attached to, +an indication of the state of the process (whether it is running, +stopped, awaiting some event (sleeping), and whether it is swapped out), +and the amount of \s-2CPU\s0 time it has used so far. +The command is identified by printing some of the words used +when it was invoked (2.6). +Shells, such as the +.I csh +you use to run the +.I ps +command, are not normally shown in the output. +.IP pwd +The +.I pwd +command prints the full +.I pathname +of the current +.I "working directory" \&. +The +.I dirs +builtin command is usually a better and faster choice. +.IP quit +The +.I quit +signal, generated by a control-\e, +is used to terminate programs which are behaving unreasonably. +It normally produces a core image file (1.8). +.IP quotation +The process by which metacharacters are prevented their special +meaning, usually by using the character `\' in pairs, or by +using the character `\e', is referred to as +.I quotation +(1.7). +.IP redirection +The routing of input or output from or to a file is known +as +.I redirection +of input or output (1.3). +.IP rehash +The +.I rehash +command tells the shell to rebuild its internal table of which commands +are found in which directories in your +.I path . +This is necessary when a new program is installed in one of these +directories (2.8). +.IP "relative pathname" +.br +A +.I pathname +which does not begin with a `/' is called a +.I "relative pathname" +since it is interpreted +.I relative +to the current +.I "working directory" . +The first +.I component +of such a +.I pathname +refers to some file or directory in the +.I "working directory" , +and subsequent +.I components +between `/' characters refer to directories below the +.I "working directory" . +.I Pathnames +that are not +.I relative +are called +.I "absolute pathnames" +(1.6). +.IP repeat +The +.I repeat +command iterates another command a specified number of times. +.IP root +The directory +that is at the top of the entire directory structure is called the +.I root +directory since it is the `root' of the entire tree structure of +directories. The name used in +.I pathnames +to indicate the +.I root +is `/'. +.I Pathnames +starting with `/' are said to be +.I absolute +since they start at the +.I root +directory. +.I Root +is also used as the part of a +.I pathname +that is left after removing +the +.I extension . +See +.I filename +for a further explanation (1.6). +.IP \s-2RUBOUT\s0 +The \s-2RUBOUT\s0 or \s-2DELETE\s0 +key is often used to erase the previously typed character; some users +prefer the \s-2BACKSPACE\s0 for this purpose. On older versions of \s-2UNIX\s0 +this key served as the \s-2INTR\s0 character. +.IP "scratch file" +Files whose names begin with a `#' are referred to as +.I "scratch files" , +since they are automatically removed by the system after a couple of +days of non-use, or more frequently if disk space becomes tight (1.3). +.IP script +Sequences of shell commands placed in a file are called shell command +.I scripts . +It is often possible to perform simple tasks using these +.I scripts +without writing a program in a language such as C, by +using the shell to selectively run other programs (3.3, 3.10). +.IP set +The builtin +.I set +command is used to assign new values to shell variables +and to show the values of the current variables. +Many shell variables have special meaning to the shell itself. +Thus by using the +.I set +command the behavior of the shell can be affected (2.1). +.IP setenv +Variables in the environment `environ (5)' +can be changed by using the +.I setenv +builtin command (2.8). +The +.I printenv +command can be used to print the value of the variables in the environment. +.IP shell +A +.I shell +is a command language interpreter. +It is possible to write and run your own +.I shell , +as +.I shells +are no different than any other programs as far as the +system is concerned. +This manual deals with the details of one particular +.I shell , +called +.I csh. +.IP "shell script" +See +.I script +(3.3, 3.10). +.IP signal +A +.I signal +in \s-2UNIX\s0 is a short message that is sent to a running program +which causes something to happen to that process. +.I Signals +are sent either by typing special +.I control +characters on the keyboard or by using the +.I kill +or +.I stop +commands (1.8, 2.6). +.IP sort +The +.I sort +program sorts a sequence of lines in ways that can be controlled +by argument +.I flags +(1.5). +.IP source +The +.I source +command causes the shell to read commands from a specified file. +It is most useful for reading files such as +.I \&.cshrc +after changing them (2.8). +.IP "special character" +.br +See +.I metacharacters +and the +appendix to this manual. +.IP standard +We refer often to the +.I "standard input" +and +.I "standard output" +of commands. +See +.I input +and +.I output +(1.3, 3.8). +.IP status +A command normally returns a +.I status +when it finishes. +By convention a +.I status +of zero indicates that the command succeeded. +Commands may return non-zero +.I status +to indicate that some abnormal event has occurred. +The shell variable +.I status +is set to the +.I status +returned by the last command. +It is most useful in shell commmand scripts (3.6). +.IP stop +The +.I stop +command causes a +.I background +job to become +.I suspended +(2.6). +.IP string +A sequential group of characters taken together is called a +.I string \&. +.I Strings +can contain any printable characters (2.2). +.IP stty +The +.I stty +program changes certain parameters inside \s-2UNIX\s0 which determine +how your terminal is handled. See `stty (1)' for a complete description (2.6). +.IP substitution +The shell implements a number of +.I substitutions +where sequences indicated by metacharacters are replaced by other sequences. +Notable examples of this are history +.I substitution +keyed by the +metacharacter `!' and variable +.I substitution +indicated by `$'. +We also refer to +.I substitutions +as +.I expansions +(3.4). +.IP suspended +A job becomes +.I suspended +after a \s-2STOP\s0 signal is sent to it, either by typing a +.I control -z +at the terminal (for +.I foreground +jobs) or by using the +.I stop +command (for +.I background +jobs). When +.I suspended , +a job temporarily stops running until it is restarted by either the +.I fg +or +.I bg +command (2.6). +.IP switch +The +.I switch +command of the shell allows the shell +to select one of a number of sequences of commands based on an +argument string. +It is similar to the +.I switch +statement in the language C (3.7). +.IP termination +When a command which is being executed finishes we say it undergoes +.I termination +or +.I terminates. +Commands normally terminate when they read an +.I end\f1-\fPof\f1-\fPfile +from their +.I "standard input" . +It is also possible to terminate commands by sending them +an +.I interrupt +or +.I quit +signal (1.8). +The +.I kill +program terminates specified jobs (2.6). +.IP then +The +.I then +command is part of the shell's +`if-then-else-endif' control construct used in command scripts (3.6). +.IP time +The +.I time +command can be used to measure the amount of \s-2CPU\s0 +and real time consumed by a specified command as well +as the amount of disk i/o, memory utilized, and number +of page faults and swaps taken by the command (2.1, 2.8). +.IP tset +The +.I tset +program is used to set standard erase and kill characters +and to tell the system what kind of terminal you are using. +It is often invoked in a +.I \&.login +file (2.1). +.IP tty +The word +.I tty +is a historical abbreviation for `teletype' which is frequently used +in \s-2UNIX\s0 to indicate the +.I port +to which a given terminal is connected. The +.I tty +command will print the name of the +.I tty +or +.I port +to which your terminal is presently connected. +.IP unalias +The +.I unalias +command removes aliases (2.8). +.IP \s-2UNIX\s0 +\s-2UNIX\s0 is an operating system on which +.I csh +runs. +\s-2UNIX\s0 provides facilities which allow +.I csh +to invoke other programs such as editors and text formatters which +you may wish to use. +.IP unset +The +.I unset +command removes the definitions of shell variables (2.2, 2.8). +.IP "variable expansion" +.br +See +.I variables +and +.I expansion +(2.2, 3.4). +.IP variables +.I Variables +in +.I csh +hold one or more strings as value. +The most common use of +.I variables +is in controlling the behavior +of the shell. +See +.I path , +.I noclobber , +and +.I ignoreeof +for examples. +.I Variables +such as +.I argv +are also used in writing shell programs (shell command scripts) +(2.2). +.IP verbose +The +.I verbose +shell variable can be set to cause commands to be echoed +after they are history expanded. +This is often useful in debugging shell scripts. +The +.I verbose +variable is set by the shell's +.I \-v +command line option (3.10). +.IP wc +The +.I wc +program calculates the number of characters, words, and lines in the +files whose names are given as arguments (2.6). +.IP while +The +.I while +builtin control construct is used in shell command scripts (3.7). +.IP word +A sequence of characters which forms an argument to a command is called +a +.I word . +Many characters which are neither letters, digits, `\-', `.' nor `/' +form +.I words +all by themselves even if they are not surrounded +by blanks. +Any sequence of characters may be made into a +.I word +by surrounding it +with `\'' characters +except for the characters `\'' and `!' which require special treatment +(1.1). +This process of placing special characters in +.I words +without their special meaning is called +.I quoting . +.IP "working directory" +.br +At any given time you are in one particular directory, called +your +.I "working directory" . +This directory's name is printed by the +.I pwd +command and the files listed by +.I ls +are the ones in this directory. +You can change +.I "working directories" +using +.I chdir . +.IP write +The +.I write +command is an obsolete way of communicating with other users who are logged in to +\s-2UNIX\s0 (you have to take turns typing). If you are both using display +terminals, use \fItalk\fP(1), which is much more pleasant. |
