+.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 programmer's manual in section 1.
+You can get 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)
+.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 up-arrow (\(ua) followed by the
+corresponding letter when you type a
+.I control
+character (e.g. `\(uaC' 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 \(uaC.
+.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 hitting the
+\s-2RUBOUT\s0 or \s-2DELETE\s0 key (although users
+can and often do change the interrupt character, usually to \(uaC).
+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).
+.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
+(3.2).
+.IP manual
+The
+.I manual
+often referred to is the
+`\s-2UNIX\s0 programmer's manual'.
+It contains a number of sections and a description of each \s-2UNIX\s0
+program.
+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
+.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 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 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 "programmer's manual"
+.br
+Also referred to as the
+.I manual .
+See the glossary entry for `manual'.
+.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 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 sends an interrupt to the current job.
+Most interactive commands return to their command level upon
+receipt of an interrupt, while non-interactive commands usually
+terminate, returning control to the shell.
+Users often change interrupt to be generated by \(uaC rather than \s-2DELETE\s0
+by using the
+.I stty
+command.
+.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 used to communicate with other users who are logged in to
+\s-2UNIX\s0.
projects / unix-history / commitdiff