+++ /dev/null
-.\" $XConsortium: sh.1 /main/2 1995/07/17 14:27:13 drk $
-.\"
-.\" David Korn
-.\" AT&T Bell Laboratories
-.\"
-.\" @(#)sh.1 (ulysses!dgk) 01/14/93-beta15
-.\"
-.nr Z 0 \" set to 1 when command name is ksh rather than sh
-.nr Y 0 \" set to 1 for R&D UNIX
-.if \nY=1 .nr Z 1
-.ds OK [\|
-.ds CK \|]
-.ds ' \s+4\v@.3m@\'\v@-.3m@\s-4
-.ds ` \s+4\v@.3m@\`\v@-.3m@\s-4
-.de P
-.br
-..
-.if \nZ=0 .TH SH 1
-.if \nZ=1 .TH KSH 1 "User Environment Utilities" "RDS Standard"
-.SH NAME
-.if \nZ=0 sh, rsh \- shell, the
-.if \nZ=1 ksh, rksh \- KornShell, a
-standard/restricted command and programming language
-.SH SYNOPSIS
-.if \nZ=0 .B sh
-.if \nZ=1 .B ksh
-[
-.B \(+-abcefhikmnoprstuvxCP
-] [
-.B \-I
-file ] [
-.B \(+-o
-option ] .\|.\|. [
-.B \-
-] [ arg .\|.\|. ]
-.br
-.if \nZ=0 .B rsh
-.if \nZ=1 .B rksh
-[
-.B \(+-abcefhikmnoprstuvxCP
-] [
-.B \-I
-file ] [
-.B \(+-o
-option ] .\|.\|. [
-.B \-
-] [ arg .\|.\|. ]
-.SH DESCRIPTION
-.if \nZ=0 .I Sh\^
-.if \nZ=1 .I Ksh\^
-is a command and programming language
-that executes commands read from a terminal
-or a file.
-.if \nZ=0 .I Rsh\^
-.if \nZ=1 .I Rksh\^
-is a restricted version of the
-.if \nZ=0 standard
-command interpreter
-.if \nZ=0 .IR sh ;
-.if \nZ=1 .IR ksh ;
-it is used to set up login names and execution environments whose
-capabilities are more controlled than those of the standard shell.
-See
-.I Invocation\^
-below
-for the meaning of arguments to the shell.
-.SS Definitions.
-A
-.I metacharacter\^
-is one of the following characters:
-.RS
-.PP
-\f3; & ( ) \(bv < > new-line space tab\fP
-.RE
-.PP
-A
-.I blank\^
-is a
-.B tab
-or a
-.BR space .
-An
-.I identifier\^
-is a sequence of letters, digits, or underscores
-starting with a letter or underscore.
-Identifiers are used as components of
-.I variable\^
-names.
-A
-.I vname\^
-is a sequence of one or more identifiers
-separated by a \fB\s+2.\s-2\fP and optionally preceded
-by a \fB\s+2.\s-2\fP.
-Vnames are used as function and variable names.
-A
-.I word\^
-is a sequence of
-.I characters\^
-excluding non-quoted
-.IR metacharacters .
-.P
-A
-.I command\^
-is a sequence of characters in the syntax
-of the shell language.
-The shell reads each command and
-carries out the desired action either directly or by invoking
-separate utilities.
-A built-in command is a command that is carried out by the
-shell itself without creating a separate process.
-Some commands are built-in purely for convenience
-and are not documented here.
-Built-ins that cause
-side effects in the shell environment and
-built-ins that are found before performing a
-path search (see
-.I Execution\^
-below)
-are documented here.
-For historical reasons, some of
-these built-ins behave differently than
-other built-ins and are called
-.IR "special built-ins" .
-.SS Commands.
-A
-.I simple-command\^
-is a list of variable assignments
-(see
-.I Variable Assignments\^
-below)
-or a sequence of
-.I blank\^
-separated words
-which may be preceded by a list of variable assignments
-(see
-.I Environment\^
-below).
-The first word specifies the name of the command to
-be executed.
-Except as specified below,
-the remaining words are passed as arguments
-to the invoked command.
-The command name is passed as argument 0
-(see
-.IR exec (2)).
-The
-.I value\^
-of a simple-command is its exit status; 0-255
-if it terminates normally; 256+\f2signum\^\fP if
-it terminates abnormally (the name of the signal corresponding
-to the exit status can be
-obtained via the
-.B "\-l $?"
-option of the
-.B kill\^
-built-in utility).
-.PP
-An
-.I "arithmetic command"
-begins with a
-.BR (( ,
-and consists of an arithmetic expression formed by
-all the characters until a matching
-.BR )) .
-(See
-.I "Arithmetic evaluation"
-below.)
-The exit status of an arithmetic command is 0 when the
-arithmetic expression evaluates to a non-zero value and
-is 1 when the arithmetic expression evaluates to 0.
-.PP
-A
-.I pipeline\^
-is a sequence of one or more
-.I commands\^
-separated by
-.BR \(bv .
-The standard output of each command but the last
-is connected by a
-.IR pipe (2)
-to the standard input of the next command.
-Each command,
-except possibly the last,
-is run as a separate process;
-the shell waits for the last command to terminate.
-The exit status of a pipeline is the exit
-status of the last command.
-Each pipeline can be preceded by the
-.I "reserved word"
-.B !
-which negates the exit status of the pipeline.
-.PP
-A
-.I list\^
-is a sequence of one or more
-pipelines
-separated by
-.BR ; ,
-.BR & ,
-.BR \(bv& ,
-.BR && ,
-or
-.BR \(bv\|\(bv ,
-and optionally terminated by
-.BR ; ,
-.BR & ,
-or
-.BR \(bv& .
-Of these five symbols,
-.BR ; ,
-.BR & ,
-and
-.B \(bv&
-have equal precedence,
-which is lower than that of
-.B &&
-and
-.BR \(bv\|\(bv .
-The symbols
-.B &&
-and
-.B \(bv\|\(bv
-also have equal precedence.
-A semicolon
-.RB ( ; )
-causes sequential execution of the preceding pipeline; an ampersand
-.RB ( & )
-causes asynchronous execution of the preceding pipeline (i.e., the shell does
-.I not\^
-wait for that pipeline to finish).
-The symbol
-.B \(bv&
-causes asynchronous execution of the preceding pipeline
-with a two-way pipe established to the parent shell;
-the standard input and output of the spawned pipeline
-can be written to and read from by the parent shell
-by applying
-the redirection operators
-.B <&
-and
-.B >&
-with arg
-.B p
-to commands and by using
-.B \-p
-option of
-the built-in commands
-.B read
-and
-.B print
-described later.
-The symbol
-.B &&
-.RB (\| \(bv\|\(bv \^)
-causes the
-.I list\^
-following it to be executed only if the preceding
-pipeline
-returns a zero (non-zero) value.
-An arbitrary number of new-lines may appear in a
-.I list\^
-instead of a semicolon,
-to delimit a command.
-.PP
-A
-.I command\^
-is either a simple-command
-or one of the following.
-Unless otherwise stated,
-the value returned by a command is that of the
-last simple-command executed in the command.
-.TP
-\f3for\fP \f2vname\^\fP \*(OK \f3in\fP \f2word\^\fP .\|.\|. \*(CK \f3;do\fP \f2list\^\fP \f3;done\fP
-Each time a
-.B for
-command is executed,
-.I name\^
-is set to the next
-.I word\^
-taken from the
-.B in
-.I word\^
-list.
-If
-.BI in " word\^"
-\&.\|.\|.
-is omitted, then
-the
-.B for
-command executes the \f3do\fP \f2list\^\fP once for each positional parameter
-that is set
-(see
-.I "Parameter Expansion\^"
-below).
-Execution ends when there are no more words in the list.
-.TP
-\f3for ((\fP \*(OK\f2expr1\^\fP\*(CK \f3;\fP \*(OK\f2expr2\^\fP\*(CK \f3;\fP \*(OK\f2expr3\^\fP\*(CK \f3))\fP \f3;do\fP \f2list\^\fP \f3;done\fP
-The arithmetic expression
-.I expr1
-is evaluated first.
-(See
-.I "Arithmetic evaluation"
-below.)
-The arithmetic expression
-.I expr2
-is repeatedly evaluated until it evalues to zero and when non-zero,
-.I list
-is executed and the arithmetic expression
-.I expr3
-evaluated.
-If any expression
-is omitted, then it behaves as if it evaluated to 1.
-.TP
-\f3select\fP \f2vname\^\fP \*(OK \f3in\fP \f2word\^\fP .\|.\|. \*(CK \f3;do\fP \f2list\^\fP \f3;done\fP
-A
-.B select
-command prints on standard error (file descriptor 2) the set of
-.IR word s,
-each preceded by a number.
-If
-.BI in " word\^"
-\&.\|.\|.
-is omitted, then
-the
-positional parameters
-are used instead
-(see
-.I "Parameter Expansion\^"
-below).
-The
-.SM
-.B PS3
-prompt is printed
-and a line is read from the standard input.
-If this line consists of the number
-of one of the listed
-.IR word s,
-then the value of the variable
-.I vname\^
-is set to the
-.I word\^
-corresponding to this number.
-If this line is empty the selection list is
-printed again.
-Otherwise the value of the variable
-.I vname\^
-is set to
-.IR null .
-The contents of the line read from standard input is
-saved in
-the variable
-.SM
-.BR REPLY .
-The
-.I list\^
-is executed for each selection until a
-.B break\^
-or
-.I end-of-file\^
-is encountered.
-If the
-.SM
-.B REPLY
-variable is set to
-.I null\^
-by the execution of
-.IR list ,
-then the selection list is printed before
-displaying the
-.SM
-.B PS3
-prompt for the next selection.
-.TP
-\f3case\fP \f2word\^\fP \f3in\fP \*(OK \*(OK\f3(\fP\*(CK\f2pattern\^\fP \*(OK \(bv \f2pattern\^\fP \*(CK .\|.\|. \f3)\fP \f2list\^\fP \f3;;\fP \*(CK .\|.\|. \f3esac\fP
-A
-.B case
-command executes the
-.I list\^
-associated with the first
-.I pattern\^
-that matches
-.IR word .
-The form of the patterns is
-the same as that used for
-file-name generation (see
-.I "File Name Generation\^"
-below).
-The
-.B ;;
-operator causes execution of
-.B case
-to terminate.
-If
-.B ;&
-is used in place of
-.B ;;
-the next subsequent list, if any, is executed.
-.ll +3
-.TP
-\f3if\fP \f2list\^\fP \f3;then\fP \f2list\^\fP \*(OK \
-\f3elif\fP \f2list\^\fP \f3;then\fP \f2list\^\fP \*(CK .\|.\|. \
-\*(OK \f3;else\fP \f2list\^\fP \*(CK \f3;f\&i\fP
-.ll -3
-The
-.I list\^
-following \f3if\fP is executed and,
-if it
-returns a zero exit status, the
-.I list\^
-following
-the first
-.B then
-is executed.
-Otherwise, the
-.I list\^
-following \f3elif\fP
-is executed and, if its value is zero,
-the
-.I list\^
-following
-the next
-.B then
-is executed.
-Failing that, the
-.B else
-.I list\^
-is executed.
-If the
-.B if
-.I list\^
-has non-zero exit status
-and there is no
-.B else
-.IR list ,
-then the
-.B if
-command returns a zero exit status.
-.TP
-.PD 0
-\f3while\fP \f2list\^\fP \f3;do\fP \f2list\^\fP \f3;done\fP
-.TP
-\f3until\fP \f2list\^\fP \f3;do\fP \f2list\^\fP \f3;done\fP
-.PD
-A
-.B while
-command repeatedly executes the
-.B while
-.I list\^
-and, if the exit status of the last command in the list is zero, executes
-the
-.B do
-.IR list ;
-otherwise the loop terminates.
-If no commands in the
-.B do
-.I list\^
-are executed, then the
-.B while
-command returns a zero exit status;
-.B until
-may be used in place of
-.B while
-to negate
-the loop termination test.
-.TP
-\f3(\fP\f2list\^\fP\f3)\fP
-.br
-Execute
-.I list\^
-in a separate environment.
-Note, that if two adjacent open parentheses are
-needed for nesting, a space must be inserted to avoid
-evaluation as an arithmetic command as described above.
-.TP
-\f3{ \fP\f2list\^\fP\f3;}\fP
-.br
-.I list\^
-is simply executed.
-Note that unlike the metacharacters
-.B (
-and
-.BR ) ,
-.B {
-and
-.B }
-are
-.IR "reserved word" s
-and must occur
-at the beginning of a line or after a
-.B ;
-in order to be recognized.
-.TP
-\f3[[\fP\f2 expression \^\fP\f3]]\fP
-.br
-Evaluates
-.I expression\^
-and returns a zero exit status when
-.I expression\^
-is true.
-See
-.I "Conditional Expressions\^"
-below, for a description of
-.IR expression .
-.TP
-.PD 0
-\f3function\fP \f2varname\^\fP \f3{\fP \f2list\^\fP \f3;}\fP
-.TP
-\f2varname\^\fP \f3() {\fP \f2list\^\fP \f3;}\fP
-.PD
-Define a function which is referenced by
-.IR varname .
-A function whose
-.I varname\^
-contains a
-.B \s+2.\s-2
-is called a discipline function and the portion
-of the
-.I varname\^
-preceding the last
-.B \s+2.\s-2
-must refer to an existing variable.
-The body of the function is the
-.I list\^
-of commands between
-.B {
-and
-.BR } .
-A function defined with the \f3function\fP \f2varname\^\fP
-syntax can also be used as an argument to the \f3.\fP
-special built-in command to get the equivalent behavior
-as if the \f2varname\^\fP\f3()\fP syntax were used to define it.
-(See
-.I Functions\^
-below.)
-.TP
-\f3time\fP \*(OK \f2pipeline\^\fP \*(CK
-.br
-If \f2pipeline\^\fP is omitted the user and system time for
-the current shell and completed child processes is printed
-on standard error.
-Otherwise,
-.I pipeline\^
-is executed and the elapsed time as well as
-the user and system time are printed on standard error.
-.PP
-The following reserved words
-are only recognized as such when they are the first word of a command
-and are not quoted:
-.if t .RS
-.PP
-.B
-.if n if then else elif fi case esac for while until do done { } function select time [[ ]] !
-.if t if then else elif fi case esac for while until do done { } function select time [[ ]] !
-.if t .RE
-.SS Variable Assignments.
-One or more variable assignments can start a simple command
-or can be an arguments to the
-.BR typeset ,
-.BR export ,
-or
-.B readonly
-special built-in commands.
-The syntax for an \f2assignment\^\fP is of the form:
-.TP
-.PD 0
-\f2varname\^\fP\f3=\fP\f2word\^\fP
-.TP
-\f2varname\^\fP\f3[\fP\f2word\^\fP\f3]\fP=\fP\f2word\^\fP
-.PD
-No space is permitted between \f2varname\^\fP and the \f3=\fP or
-between \f3=\fP and \fIword\^\fP.
-.TP
-\f2varname\^\fP\f3=(\fP\f2assign_list\^\fP\f3)\fP
-No space is permitted between \f2varname\^\fP and the \f3=\fP.
-An \f2assign_list\^\fP can be one of the following:
-.RS 15
-.PD 0
-.TP
-\f2word\^\fP ...
-Indexed array assignment.
-.TP
-\f3[\fP\f2word\^\fP\f3]=\fP\f2word\^\fP .\|.\|.
-Associative array assignment.
-.TP
-\f2assignment\^\fP .\|.\|.
-Nested variable assignment.
-.TP
-\f3typeset\fP \*(OK\f2options\fP\*(CK \f2assignment\^\fP .\|.\|.
-Nested variable assignment. Multiple assignments
-can be specified by separating each of them with a \f3;\fP.
-.PD
-.RE
-.SS Comments.
-.PD 0
-A word beginning with
-.B #
-causes that word and all the following characters up to a new-line
-to be ignored.
-.SS Aliasing.
-The first word of each command is replaced by the text of an
-.B alias
-if an
-.B alias
-for this word has been defined.
-An
-.B alias
-name consists of any number of characters excluding metacharacters,
-quoting characters,
-file expansion characters,
-parameter expansion and command substitution
-characters,
-and
-.BR = .
-The replacement string can contain any
-valid shell script
-including the metacharacters listed above.
-The first word of each command in the
-replaced text,
-other than
-any that are in the process of being replaced,
-will be tested for aliases.
-If the last character of the alias value is a
-.I blank\^
-then the word following the alias will also be checked for alias
-substitution.
-Aliases can be used to redefine
-built-in commands but cannot be used to redefine
-the reserved words listed above.
-Aliases can be created and listed with the
-.B alias
-command and can be removed with the
-.B unalias
-command.
-.PP
-.I Aliasing\^
-is performed when
-scripts are read,
-not while they are executed.
-Therefore,
-for an alias to take effect
-the
-.B
-alias
-definition command has to be executed before
-the command which references the alias is read.
-.PP
-The following
-.I exported aliases
-are compiled into the shell
-but can be unset or redefined:
-.RS 20
-.PD 0
-.TP
-.B "autoload=\(fmtypeset \-fu\(fm"
-.TP
-.B "command=\(fmcommand \(fm"
-.TP
-.B "fc=hist"
-.TP
-.B "float=\(fmtypeset \-E\(fm"
-.TP
-.B "functions=\(fmtypeset \-f\(fm"
-.TP
-.B "hash=\(fmalias \-t \-\-\(fm"
-.TP
-.B "history=\(fmhist \-l\(fm"
-.TP
-.B "integer=\(fmtypeset \-i\(fm"
-.TP
-.B "nameref=\(fmtypeset \-n\(fm"
-.TP
-.B "nohup=\(fmnohup \(fm"
-.TP
-.B "r=\(fmhist \-s\(fm"
-.TP
-.B "redirect=\(fmcommand exec\(fm"
-.TP
-.B "stop=\(fmkill \-s \s-1STOP\s+1\(fm"
-.TP
-.B "times=\(fm{ {time;} 2>&1;}\(fm"
-.TP
-.B "type=\(fmwhence \-v\(fm"
-.PD
-.RE
-.SS Tilde Substitution.
-After alias substitution is performed, each word
-is checked to see if it begins with an unquoted
-.BR \(ap .
-For tilde substitution,
-.I word\^
-also refers to the
-.I word\^
-portion of parameter expansion
-( see
-.I "Parameter Expansion\^"
-below.)
-If it does, then the word up to a
-.B /
-is checked to see if it matches a user name in the
-password database (
-often the
-.B /etc/passwd
-file).
-If a match is found, the
-.B \(ap
-and the matched login name are replaced by the
-login directory of the matched user.
-If no match is found, the original text is left unchanged.
-A
-.B \(ap
-by itself, or in front of a
-.BR / ,
-is replaced by
-.SM
-.BR $HOME .
-A
-.B \(ap
-followed by a
-.B +
-or
-.B \-
-is replaced by the value of
-.B
-.SM $PWD
-and
-.B
-.SM $OLDPWD
-respectively.
-.PP
-In addition,
-when expanding a
-.IR "variable assignment" ,
-.I tilde
-substitution is attempted when
-the value of the assignment
-begins with a
-.BR \(ap ,
-and when a
-.B \(ap
-appears after a
-.BR : .
-The
-.B :
-also terminates a
-.B \(ap
-login name.
-.if \nY=1 \{.PP
-On R&D UNIX Systems with RFS, an additional capability,
-.BR \(aphost!user ,
-has been added to
-.IR ksh .
-See
-.IR logdir (1)
-for a complete description of the capability.\}
-.SS Command Substitution.
-The standard output from a command enclosed in
-parentheses preceded by a dollar sign (
-.B $(\|)
-)
-or a pair of grave accents (\^\f3\*`\^\*`\fP\^)
-may be used as part or all
-of a word;
-trailing new-lines are removed.
-In the second (obsolete) form, the string between the quotes is processed
-for special quoting characters before the command is executed (see
-.I Quoting\^
-below).
-The command substitution
-\^\f3$(\^cat file\^)\fP\^
-can be replaced by the equivalent but faster
-\^\f3$(\^<file\^)\fP\^.
-.SS Arithmetic Substitution.
-An arithmetic expression enclosed in double
-parentheses preceded by a dollar sign (
-.B $((\|))
-)
-is replaced by the value of the arithmetic expression
-within the double parentheses.
-.SS Process Substitution.
-This feature is only available on
-versions of the UNIX operating system that support the
-.B /dev/fd
-directory for naming open files.
-Each command argument of the form
-\f3<(\fP\f2list\^\fP\f3)\fP
-or
-\f3>(\fP\f2list\^\fP\f3)\fP
-will run process
-.I list
-asynchronously connected to some file in
-.BR /dev/fd .
-The name of this file will become the argument to the command.
-If the form with
-.B >
-is selected then writing on this file will provide input for
-.IR list .
-If
-.B <
-is used,
-then the file passed as an argument will contain the output of the
-.I list
-process.
-For example,
-.RS
-.PP
-\f3paste <(cut \-f1\fP \f2file1\fP\f3) <(cut \-f3\fP \f2file2\f3) | tee >(\fP\f2process1\fP\f3) >(\fP\f2process2\fP\f3)\fP
-.RE
-.PP
-.I cuts
-fields 1 and 3 from
-the files
-.I file1
-and
-.I file2
-respectively,
-.I pastes
-the results together, and
-sends it
-to the processes
-.I process1
-and
-.IR process2 ,
-as well as putting it onto the standard output.
-Note that the file, which is passed as an argument to the command,
-is a UNIX
-.IR pipe (2)
-so programs that expect to
-.IR lseek (2)
-on the file will not work.
-.SS Parameter Expansion.
-A
-.I parameter\^
-is an
-.IR variable ,
-one or more digits,
-or any of the characters
-.BR \(** ,
-.BR @ ,
-.BR # ,
-.BR ? ,
-.BR \- ,
-.BR $ ,
-and
-.BR !\\^ .
-A
-.I variable\^
-is denoted by a \f2vname\fP.
-To create a variable whose
-.I vname\^
-contains a \f3\s+2.\s-2\fP,
-a variable whose
-.I vname\^
-consists of everything before the last \f3\s+2.\s-2\fP must already exist.
-A
-.I variable\^
-has a
-.I value\^
-and zero or more
-.IR attributes .
-.I Variables\^
-can be assigned
-.I values\^
-and
-.I attributes
-by using the
-.B typeset\^
-special built-in command.
-The attributes supported by the shell are described
-later with the
-.B typeset\^
-special built-in command.
-Exported variables pass values and attributes to
-the environment.
-.PP
-The shell supports both indexed and associative arrays.
-An element of an array variable is referenced by a
-.IR subscript .
-A
-.I subscript\^
-for an indexed array is denoted by
-an
-.I arithmetic expression\^
-(see
-.I "Arithmetic evaluation"
-below)
-between a
-.B [
-and a
-.BR ] .
-To assign values to an indexed array, use
-\f3set \-A\fP \f2vname\fP \f2value\fP .\|.\|. .
-The value of all
-subscripts must be in the
-range of
-0 through 4095.
-Indexed arrays need not be declared.
-Any reference to a variable
-with a valid subscript is
-legal and an array will be created if necessary.
-.PP
-An associative array is created with the
-.B \-A
-option to
-.BR typeset.
-A
-.I subscript\^
-for an associative array is denoted by
-a string enclosed between
-.B [
-and
-.BR ] .
-.PP
-Referencing any array without a subscript
-is equivalent to referencing the array with subscript 0.
-.PP
-The
-.I value\^
-of a
-.I variable\^
-may be assigned by writing:
-.RS
-.PP
-.IB vname = value\^\|
-\*(OK
-.IB vname = value\^
-\*(CK .\|.\|.
-.RE
-.PP
-.PD 0
-or
-.RS
-.PP
-.IB vname [ subscript ]= value\^\|
-\*(OK
-.IB vname [ subscript ]= value\^
-\*(CK .\|.\|.
-.RE
-Note that no space is allowed before or after the
-.BR = .
-.PP
-.PD 0
-A
-.I nameref\^
-is a variable that is a reference to another variable.
-A nameref is created with the
-.B \-n
-attribute of
-.B typeset .
-The value of the variable at the time of the
-.B typeset
-command becomes the variable that will be referenced whenever
-the nameref variable is used.
-The name of a nameref variable cannot contain a \fB\s+2.\s-2\fP.
-When a variable or function name contains a \fB\s+2.\s-2\fP, and the portion
-of the name up to the first \fB\s+2.\s-2\fP matches the
-name of a nameref, the variable referred to is obtained by
-replacing the nameref portion with the name of the variable
-referenced by the nameref.
-A nameref provides a convenient way to refer to the variable
-inside a function whose name is passed as an argument to a function.
-For example, if the name of a variable is passed as the first
-argument to a function, the command
-.RS
-.PP
-typeset \-n var=$1
-.RE
-.PP
-inside the function causes references and assignments to
-.B var
-to be references and assignments to the variable whose
-name has been passed to the function.
-.PP
-If either of the floating point attributes,
-.BR \-E ,
-or
-.BR \-F ,
-or the integer attribute,
-.BR \-i ,
-is set for
-.IR vname ,
-then the
-.I value\^
-is subject to arithmetic evaluation as described below.
-.PP
-Positional parameters,
-parameters denoted by a number,
-may be assigned values with the
-.B set\^
-special built-in command.
-Parameter
-.B $0
-is set from argument zero when the shell
-is invoked.
-.PP
-The character
-.B $
-is used to introduce substitutable
-.IR parameters .
-.TP
-\f3${\fP\f2parameter\^\fP\f3}\fP
-The shell
-reads all the characters from
-.B ${
-to the matching
-.B }
-as part of the same word even if it contains
-braces or metacharacters.
-The value, if any, of the parameter is substituted.
-The braces are required when
-.I parameter\^
-is followed by a letter, digit, or underscore
-that is not to be interpreted as part of its name,
-when the variable name contains a \fB\s+2.\s-2\fP,
-or when a variable is subscripted.
-If
-.I parameter\^
-is one or more digits then it is a positional parameter.
-A positional parameter of more than one digit must be
-enclosed in braces.
-If
-.I parameter\^
-is
-.B \(**
-or
-.BR @ ,
-then all the positional
-parameters, starting with
-.BR $1 ,
-are substituted
-(separated by a field separator character).
-If an array
-.I vname\^
-with subscript
-.B \(**
-or
-.B @
-is used,
-then the value
-for each of the
-elements
-is substituted
-(separated by a field separator character).
-.TP
-\f3${#\fP\f2parameter\^\fP\f3}\fP
-If
-.I parameter\^
-is
-.B \(**
-or
-.BR @ ,
-the number of positional parameters is substituted.
-Otherwise, the length of the value of the
-.I parameter\^
-is substituted.
-.TP
-\f3${#\fP\f2vname\fP\f3[*]}\fP
-The number of elements in the array
-.I vname\^
-is substituted.
-.TP
-\f3${!\fP\f2vname\^\fP\f3}\fP
-Expands to the name of the variable referred to by
-.IR vname .
-This will be
-.I vname\^
-except when
-.I vname\^
-is a name reference.
-.TP
-\f3${!\fP\f2vname\^\fP\f3[\f2subscript\^\f3]}\fP
-Expands to name of the subscript unless
-.I subscript\^
-is
-.BR * ,
-or
-.BR @ .
-When
-.I subscript\^
-is
-.BR * ,
-the list of array subscripts for \f2vname\^\fP
-is generated.
-For a variable that is not an array, the value is 0 if the variable
-is set. Otherwise it is null.
-When
-.I subscript\^
-is
-.BR @ ,
-same as above, except that when used in double quotes,
-each array subscript yields a separate
-argument.
-.TP
-\f3${!\fP\f2prefix\^\fP\f3*}\fP
-Expands to the names of the variables whose names begin with
-.IR prefix .
-.TP
-\f3${\fP\f2parameter\^\fP\f3:\-\fP\f2word\^\fP\f3}\fP
-If
-.I parameter\^
-is set and is non-null then substitute its value;
-otherwise substitute
-.IR word .
-.TP
-\f3${\fP\f2parameter\^\fP\f3:=\fP\f2word\^\fP\f3}\fP
-If
-.I parameter\^
-is not set or is null then set it to
-.IR word ;
-the value of the parameter is then substituted.
-Positional parameters may not be assigned to
-in this way.
-.TP
-\f3${\fP\f2parameter\^\fP\f3:?\fP\f2word\^\fP\f3}\fP
-If
-.I parameter\^
-is set and is non-null then substitute its value;
-otherwise, print
-.I word\^
-and exit from the shell.
-If
-.I word\^
-is omitted then a standard message is printed.
-.TP
-\f3${\fP\f2parameter\^\fP\f3:+\fP\f2word\^\fP\f3}\fP
-If
-.I parameter\^
-is set and is non-null then substitute
-.IR word ;
-otherwise substitute nothing.
-.TP
-.PD 0
-\f3${\fP\f2parameter\^\fP\f3:\fP\f2offset\^\fP\f3:\fP\f2length\^\fP\f3}\fP
-.TP
-\f3${\fP\f2parameter\^\fP\f3:\fP\f2offset\^\fP\f3}\fP
-Expands to the portion of the value of
-.I parameter\^
-starting at the character determined by expanding
-.I offset\^
-as an arithmetic expression and consisting of the
-number of characters determined by the arithmetic expression
-defined by
-.IR length.
-In the second form, the remainder of the value is used.
-If
-.I parameter\^
-is
-.B \(**
-or
-.BR @ ,
-or is an array name indexed by
-.B \(**
-or
-.BR @ ,
-then
-.I offset\^
-and
-.I length\^
-refer to the array index and number
-of elements respectively.
-.TP
-.PD 0
-\f3${\fP\f2parameter\^\fP\f3#\fP\f2pattern\^\fP\f3}\fP
-.TP
-\f3${\fP\f2parameter\^\fP\f3##\fP\f2pattern\^\fP\f3}\fP
-.PD
-If
-the shell
-.I pattern\^
-matches the beginning of the value of
-.IR parameter ,
-then the value of
-this expansion is the value of the
-.I parameter\^
-with the matched portion deleted;
-otherwise the value of this
-.I parameter\^
-is substituted.
-In the first form the smallest matching pattern is deleted and in the
-second form the largest matching pattern is deleted.
-When
-.I parameter\^
-is
-.BR @ ,
-.BR * ,
-or an array variable with subscript
-.BR @ ,
-or
-.BR * ,
-the substring operation is applied to each element in turn.
-.TP
-.PD 0
-\f3${\fP\f2parameter\^\fP\f3%\fP\f2pattern\^\fP\f3}\fP
-.TP
-\f3${\fP\f2parameter\^\fP\f3%%\fP\f2pattern\^\fP\f3}\fP
-.PD
-If
-the shell
-.I pattern\^
-matches the end of the value of
-.IR parameter ,
-then the value of
-this expansion is the value of the
-.I parameter\^
-with the matched part deleted;
-otherwise substitute the value of
-.IR parameter .
-In the first form the smallest matching pattern is deleted and in the
-second form the largest matching pattern is deleted.
-When
-.I parameter\^
-is
-.BR @ ,
-.BR * ,
-or an array variable with subscript
-.BR @ ,
-or
-.BR * ,
-the substring operation is applied to each element in turn.
-.TP
-.PD 0
-\f3${\fP\f2parameter\^\fP\f3/\fP\f2pattern\^\fP\f3/\f2string\^\fP\f3}\fP
-.TP
-\f3${\fP\f2parameter\^\fP\f3//\fP\f2pattern\^\fP\f3/\f2string\^\fP\f3}\fP
-.PD
-Expands
-.I parameter\^
-and replaces
-.I pattern\^
-with the given
-.IR string.
-In the first form,
-only the first occurrence of
-.I pattern\^
-is replaced.
-In the second form,
-each match for
-.I pattern\^
-is replaced by the given
-.IR string.
-When
-.I string\^
-is null, the
-.I pattern\^
-will be deleted and the
-.B /
-in front of
-.I string\^
-may be omitted.
-When
-.I parameter\^
-is
-.BR @ ,
-.BR * ,
-or an array variable with subscript
-.BR @ ,
-or
-.BR * ,
-the substitution operation is applied to each element in turn.
-.PP
-In the above,
-.I word\^
-is not evaluated unless it is
-to be used as the substituted string,
-so that, in the following example,
-.B pwd\^
-is executed only if
-.B d\^
-is not set or is null:
-.RS
-.PP
-print \|${d:\-\^$(\^pwd\^)\^}
-.RE
-.PP
-If the colon (
-.B : )
-is omitted from the above expressions,
-then the shell only checks whether
-.I parameter\^
-is set or not.
-.PP
-The following
-parameters
-are automatically set by the shell:
-.RS
-.PD 0
-.TP
-.B #
-The number of positional parameters in decimal.
-.TP
-.B \-
-Options supplied to the shell on invocation or by
-the
-.B set
-command.
-.TP
-.B ?
-The decimal value returned by the last executed command.
-.TP
-.B $
-The process number of this shell.
-.TP
-.B _
-Initially, the value of
-.B _
-is an absolute pathname of the shell or script being executed
-as passed in the
-.IR environment .
-Subsequently it is assigned the last argument of the previous command.
-This parameter is not set for commands which are asynchronous.
-This parameter is also used to hold the name of the matching
-.B
-.SM MAIL
-file when checking for mail.
-.TP
-.B !
-The process number of the last background command invoked.
-.TP
-.B .sh.edchar
-This variable contains the value of the keyboard character
-(or sequence of characters if the first character is an ESC, ascii
-.B 033 )
-that has
-been entered when processing a
-.B
-.SM KEYBD
-trap.
-If the value is changed as part of the trap action, then the new
-value replaces the key (or key sequence) that caused the trap.
-.TP
-.B .sh.edcol
-The character position of the cursor at the time of the most recent
-.B
-.SM KEYBD
-trap.
-.TP
-.B .sh.edmode
-The value is set to ESC when processing a
-.B
-.SM KEYBD
-trap while in
-.B vi
-insert mode. (See
-.I "Vi Editing Mode"\^
-below.)
-Otherwise,
-.B .sh.edmode
-is null when processing a
-.B
-.SM KEYBD
-trap.
-.TP
-.B .sh.edtext
-The characters in the input buffer at the time of the most recent
-.B
-.SM KEYBD
-trap.
-The value is null when not processing a
-.B
-.SM KEYBD
-trap.
-.TP
-.B .sh.name
-Set to the name of the variable at the time of a
-.B set
-or
-.B get
-discipline is invoked.
-.TP
-.B .sh.subscript
-Set to the name subscript of the variable at the time of a
-.B set
-or
-.B get
-discipline is invoked.
-.TP
-.B .sh.value
-Set to the value of the variable at the time of a
-.B set
-discipline.
-.TP
-.B .sh.version
-Set to a value that identifies the version of this shell.
-.TP
-.B
-.SM LINENO
-The line number of the current line within the script or
-function being executed.
-.TP
-.B
-.SM OLDPWD
-The previous working directory set by the
-.B cd
-command.
-.TP
-.B
-.SM OPTARG
-The value of the last option argument processed by the
-.B getopts
-built-in command.
-.TP
-.B
-.SM OPTIND
-The index of the last option argument processed by the
-.B getopts
-built-in command.
-.TP
-.B
-.SM PPID
-The process number of the parent of the shell.
-.TP
-.B
-.SM PWD
-The present working directory set by the
-.B cd
-command.
-.TP
-.B
-.SM RANDOM
-Each time this variable is referenced, a random integer,
-uniformly distributed between 0 and 32767, is generated.
-The sequence of random numbers can be initialized by assigning
-a numeric value to
-.SM
-.BR RANDOM .
-.TP
-.B
-.SM REPLY
-This variable is set by the
-.B select
-statement and by
-the
-.B read
-built-in command when no arguments are supplied.
-.TP
-.B
-.SM SECONDS
-Each time this variable is referenced, the number of
-seconds since shell invocation is returned.
-If this variable is
-assigned a value, then the value returned upon reference will
-be the value that was assigned plus the number of seconds since the assignment.
-.PD
-.RE
-.PP
-The following
-variables
-are used by the shell:
-.RS
-.PD 0
-.TP
-.B
-.SM CDPATH
-The search path for the
-.B cd
-command.
-.TP
-.B
-.SM COLUMNS
-If this variable is set,
-the value is used to define the width of the edit window
-for the shell edit modes and for printing
-.B select
-lists.
-.TP
-.B
-.SM EDITOR
-If the value of this variable ends in
-.IR emacs ,
-.IR gmacs ,
-or
-.I vi
-and the
-.B
-.SM VISUAL
-variable is not set,
-then the corresponding option
-(see Special Command
-.B set
-below)
-will be turned on.
-.TP
-.SM
-.B ENV
-If this variable is set, then
-parameter expansion, command substitution, and arithmetic substitution,
-are performed on
-the value to generate
-the pathname of the script that will be
-executed when the shell
-is invoked.
-(See
-.I Invocation\^
-below.)
-This file is typically used for
-.I alias
-and
-.I function
-definitions.
-.TP
-.B
-.SM FCEDIT
-Obsolete name for
-the default editor name for the
-.B hist
-command.
-.B
-.SM FCEDIT
-is not used when
-.B
-.SM HISTEDIT
-is set.
-.TP
-.SM
-.B FIGNORE
-A pattern that defines the set of filenames that will be
-ignored when performing filename matching.
-.TP
-.SM
-.B FPATH
-The search path for function definitions.
-This path is searched when a function with the
-.B \-u
-attribute is referenced and when a command is not found.
-If an executable file is found, then it is read and executed
-in the current environment.
-.TP
-.SM
-.B IFS
-Internal field separators,
-normally
-.BR space ,
-.BR tab ,
-and
-.B new-line
-that are used to separate the results of
-command substitution or parameter expansion
-and to separate fields with the built-in command
-.BR read .
-The first character of the
-.SM
-.B IFS
-variable is used to separate arguments for the
-.B
-"$\(**"
-substitution. (See
-.I Quoting
-below.)
-Each single occurrence of
-an
-.SM
-.B IFS
-character in the string to be split,
-except
-.BR space ,
-.BR tab ,
-and
-.BR new-line ,
-separates a field.
-One or more
-.BR space ,
-.BR tab ,
-or
-.B new-line
-characters separate a field.
-.TP
-.B
-.SM HISTEDIT
-Name for
-the default editor name for the
-.B hist
-command.
-.TP
-.SM
-.B HISTFILE
-If this variable is set when the shell is invoked, then
-the value is the pathname of the file that will be
-used to store the command history.
-(See
-.I "Command re-entry\^"
-below.)
-.TP
-.SM
-.B HISTSIZE
-If this variable is set when the shell is invoked, then
-the number of previously entered commands that
-are accessible by this shell
-will be greater than or equal to this number.
-The default is 128.
-.TP
-.B
-.SM HOME
-The default argument (home directory) for the
-.B cd
-command.
-.TP
-.B
-.SM LINES
-If this variable is set,
-the value is used to determine the column length for printing
-.B select
-lists.
-Select lists will print vertically until about two-thirds of
-.B
-.SM LINES
-lines are filled.
-.TP
-.B
-.SM MAIL
-If this variable is set to the name of a mail file
-.I and\^
-the
-.B
-.SM MAILPATH
-variable is not set,
-then the shell informs the user of arrival of mail
-in the specified file.
-.TP
-.B
-.SM MAILCHECK
-This variable specifies how often (in seconds) the
-shell will check for changes in the modification time
-of any of the files specified by the
-.B
-.SM MAILPATH
-or
-.B
-.SM MAIL
-variables.
-The default value is 600 seconds.
-When the time has elapsed
-the shell will check before issuing the next prompt.
-.TP
-.B
-.SM MAILPATH
-A colon (
-.B :
-)
-separated list of file names.
-If this variable is set
-then the shell informs the user of
-any modifications to the specified files
-that have occurred within the last
-.B
-.SM MAILCHECK
-seconds.
-Each file name can be followed by a
-.B ?
-and a message that will be printed.
-The message will undergo parameter expansion, command substitution,
-and arithmetic substitution
-with the variable
-.B $_
-defined as the name of the file that has changed.
-The default message is
-.I you have mail in $_\^.
-.TP
-.B
-.SM PATH
-The search path for commands (see
-.I Execution\^
-below).
-The user may not change
-.B \s-1PATH\s+1
-if executing under
-.if \nZ=0 .B rsh
-.if \nZ=1 .B rksh
-(except in
-.BR .profile\^).
-.TP
-.SM
-.B PS1
-The value of this variable is expanded for parameter
-expansion, command substitution, and arithmetic substitution to define the
-primary prompt string which by default is
-.RB `` "$\|\|\|" ''.
-The character
-.B !
-in the primary prompt string is replaced by the
-.I command\^
-number (see
-.I "Command Re-entry"\^
-below).
-Two successive occurrences of
-.B !
-will produce a single
-.B !
-when the prompt string is printed.
-.TP
-.SM
-.B PS2
-Secondary prompt string, by default
-.RB `` "> \|" ''.
-.TP
-.SM
-.B PS3
-Selection prompt string
-used within a
-.B select
-loop, by default
-.RB `` "#? \|" ''.
-.TP
-.SM
-.B PS4
-The value of this variable is expanded for parameter evaluation,
-command substitution, and arithmetic substitution
-and precedes each line of an execution trace.
-If omitted, the execution trace prompt is
-.RB `` "+ \|" ''.
-.TP
-.SM
-.B SHELL
-The pathname of the
-.I shell\^
-is kept in the environment.
-At invocation, if the basename of this variable is
-.BR rsh ,
-.BR rksh ,
-or
-.BR krsh ,
-then the shell becomes restricted.
-.TP
-.B
-.SM TMOUT
-If set to a value greater than zero,
-the
-.B read
-built-in command terminates after
-.B
-.SM TMOUT
-seconds when input is from a terminal.
-Otherwise,
-the shell will terminate if a line is not entered within
-the prescribed number of seconds while reading from a terminal.
-(Note that the shell can be compiled with a maximum bound
-for this value which cannot be exceeded.)
-.TP
-.B
-.SM VISUAL
-If the value of this variable ends in
-.IR emacs ,
-.IR gmacs ,
-or
-.I vi
-then the corresponding option
-(see Special Command
-.B set
-below)
-will be turned on.
-.PD
-.RE
-.PP
-The shell gives default values to
-\f3\s-1PATH\s+1\fP, \f3\s-1PS1\s+1\fP, \f3\s-1PS2\s+1\fP,
-\f3\s-1PS3\s+1\fP, \f3\s-1PS4\s+1\fP, \f3\s-1MAILCHECK\s+1\fP, \f3\s-1HISTEDIT\s+1\fP,
-\f3\s-1TMOUT\s+1\fP and \f3\s-1IFS\s+1\fP,
-while
-.SM
-.BR HOME ,
-.SM
-.BR SHELL ,
-.SM
-.BR ENV ,
-and
-.SM
-.B MAIL
-are
-not set at all by the shell (although
-.SM
-.B HOME
-.I is\^
-set by
-.IR login (1)).
-On some systems
-.SM
-.B MAIL
-and
-.SM
-.B SHELL
-are also
-set by
-.IR login (1).
-.SS Field Splitting
-After parameter expansion and command substitution,
-the results of substitutions are scanned for the field separator
-characters (those found in
-.SM
-.B IFS\^\c
-)
-and split into distinct fields where such characters are found.
-Explicit null fields (\^\f3"\^"\fP or \f3\*\(fm\^\*\(fm\fP\^) are retained.
-Implicit null fields
-(those resulting from
-.I parameters\^
-that have no values or command substitutions with no output) are removed.
-.SS File Name Generation.
-Following splitting, each field is scanned for the characters
-.BR \(** ,
-.BR ? ,
-.BR ( ,
-and
-.B \*(OK\^
-unless the
-.B \-f
-option has been set.
-If one of these characters appears
-then the word is regarded as a
-.IR pattern .
-Each file name component that contains any pattern character
-is replaced with a lexicographically sorted set of names
-that matches the pattern
-from
-that directory.
-If no file name is found that matches the pattern, then
-that component of the filename is left unchanged.
-If
-.SM
-.B FIGNORE
-is set,
-then each file name component
-that matches the pattern defined by the value of
-.SM
-.B FIGNORE
-is ignored when generating the matching filenames.
-The names
-.B .
-and
-.B ..
-are also ignored.
-If
-.SM
-.B FIGNORE
-is not set,
-the character
-.B .
-at the start of each file name component
-will be ignored unless the first character of the pattern
-corresponding to this component is the character
-.BR .
-itself.
-Note, that for other
-uses of pattern matching the
-.B /
-and
-.B .
-are not treated specially.
-.PP
-.PD 0
-.RS
-.TP
-.B \(**
-Matches any string, including the null string.
-.TP
-.B ?
-Matches any single character.
-.TP
-.BR \*(OK \^.\|.\|.\^ \*(CK
-Matches any one of the enclosed characters.
-A pair of characters separated by
-.B \-
-matches any
-character lexically between the pair, inclusive.
-If the first character following the opening
-.B \*(OK\^
-is a
-.B !
-then any character not enclosed is matched.
-A
-.B \-
-can be included in the character set by putting it as the
-first or last character.
-.br
-Within
-.B \*(OK\^
-and
-.B \*(CK\^
-character classes can be specified with the syntax
-\f3[:\fP\f2class\fP\f3:]\fP
-where class is one of the following:
-.if t .RS
-.PP
-.B
-.if n alnum alpha cntrl digit graph lower print punct space upper xdigit
-.if t alnum alpha cntrl digit graph lower print punct space upper xdigit
-.if t .RE
-.PD
-.RE
-A
-.I pattern-list
-is a list of one or more patterns separated from each other
-with a
-.BR \(bv .
-Composite patterns can be formed with one or more of the following:
-.PD 0
-.RS
-.TP
-\f3?(\fP\f2pattern-list\^\fP\f3)\fP
-Optionally matches any one of the given patterns.
-.TP
-\f3*(\fP\f2pattern-list\^\fP\f3)\fP
-Matches zero or more occurrences of the given patterns.
-.TP
-\f3+(\fP\f2pattern-list\^\fP\f3)\fP
-Matches one or more occurrences of the given patterns.
-.TP
-\f3\&@\&(\fP\f2pattern-list\^\fP\f3)\fP
-Matches exactly one of the given patterns.
-.br
-.TP
-\f3!(\fP\f2pattern-list\^\fP\f3)\fP
-Matches anything except one of the given patterns.
-.PD
-.RE
-.SS Quoting.
-Each of the
-.I metacharacters\^
-listed earlier (see
-.I Definitions\^
-above)
-has a special meaning to the shell
-and causes termination of a word unless quoted.
-A character may be
-.I quoted\^
-(i.e., made to stand for itself)
-by preceding
-it with a
-.BR \e .
-The pair
-.B \enew-line
-is removed.
-All characters enclosed between a pair of single quote marks
-(\^\f3\(fm\^\(fm\fP\^)
-that is not preceded by a
-.B $
-are quoted.
-A single quote cannot appear within the single quotes.
-A single quoted string preceded an unquoted
-.B $
-is processed as an ANSI-C string
-except that
-.B \e0
-within the string causes the remainder of the
-string to be ignored and
-.B \eE
-is equivalent to the escape characer
-(ascii
-.BR 033 ).
-Inside double quote marks
-(\f3"\^"\fP),
-parameter and command substitution occur and
-.B \e
-quotes the characters
-.BR \e ,
-.BR \*` ,
-\f3"\fP,
-and
-.BR $ .
-The meaning of
-.B "$\(**"
-and
-.B "$@"
-is identical when not quoted or when used as a variable assignment value
-or as a file name.
-However, when used as a command argument,
-.B
-"$\(**"
-is equivalent to
-\f3"$1\fP\f2d\fP\f3\|$2\fP\f2d\fP\|.\|.\|.\f3"\fP,
-where
-.I d
-is the first character of the
-.SM
-.B IFS
-variable, whereas
-.B
-"$@"
-is equivalent to
-.B
-"$1"\|
-.B
-"$2"\|
-\&.\|.\|.\^.
-Inside grave quote marks
-(\f3\*`\^\*`\fP),
-.B \e
-quotes the characters
-.BR \e ,
-.BR \*` ,
-and
-.BR $ .
-If the grave quotes occur within double quotes then
-.B \e
-also quotes the character
-\f3"\fP.
-.PP
-The special meaning of reserved words or aliases can be removed by quoting any
-character of the reserved word.
-The recognition of function names or built-in command names listed below
-cannot be altered by quoting them.
-.SS Arithmetic Evaluation.
-The shell performs arithmetic evaluation for
-arithmetic substitution, to evaluate an arithmetic command,
-to evaluate an indexed array subscript,
-and to evaluate arguments to
-the built-in commands
-.B shift\^
-and
-.BR let .
-Evaluations are performed using
-double precision floating point
-arithmetic.
-Floating point constants follow the ANSI-C programming language
-conventions.
-Integer constants are of the form
-\*(OK\f2base\f3#\^\f1\*(CK\f2n\^\fP
-where
-.I base\^
-is a decimal number between two and sixty-four
-representing the arithmetic base
-and
-.I n\^
-is a number in that base.
-The digits above 9 are represented
-by the lower case characters, the upper case characters,
-.BR @ ,
-and
-.B _
-respectively.
-For bases less than 36, upper and lower case
-character can be used interchangeably.
-If
-.I base\^
-is omitted
-then base 10 is used.
-.PP
-An arithmetic expression uses the same syntax, precedence, and
-associativity of
-expression as the C language.
-All the C language operators
-that apply to floating point quantities can be used.
-In addition, when the value of an arithmetic variable
-or sub-expression can be represented as a long integer,
-all C language integer arithmetic operations can be performed.
-Variables can be referenced by name within an arithmetic expression
-without using the parameter expansion syntax.
-When a variable is referenced, its value is evaluated as
-an arithmetic expression.
-The following math library functions can be used with an arithmetic
-expression:
-.if t .RS
-.PP
-.B
-.if n abs acos asin atan cos cosh exp int log sin sinh sqrt tan tanh
-.if t abs acos asin atan cos cosh exp int log sin sinh sqrt tan tanh
-.if t .RE
-.PP
-An internal representation of a
-.I variable\^
-as a double precision floating point can be specified with the
-\f3\-E\fP \*(OK\f2n\^\fP\*(CK
-or
-\f3\-F\fP \*(OK\f2n\^\fP\*(CK
-option of the
-.B typeset
-special built-in command.
-The
-.B \-E
-option causes the expansion of the value to be represented using
-scientific notation when it is expanded.
-The optional option argument
-.I n
-defines the number of significant figures.
-The
-.B \-F
-option causes the expansion to be represented as a floating decimal number
-when it is expanded.
-The optional option argument
-.I n
-defines the number of places after the decimal point in this case.
-.PP
-An internal integer representation of a
-.I variable\^
-can be specified with the
-\f3\-i\fP \*(OK\f2n\^\fP\*(CK
-option of the
-.B typeset
-special built-in command.
-The optional option argument
-.I n
-specifies an arithmetic base to be used when expanding the variable.
-If you do not specify an arithmetic base,
-the first assignment to the
-variable determines the arithmetic base.
-.PP
-Arithmetic evaluation is performed on the value of each
-assignment to a variable with the
-.BR \-E ,
-.BR \-F ,
-or
-.B \-i
-attribute.
-Assigning a floating point number to a
-variable whose type is an integer causes the fractional
-part to be truncated.
-.PP
-.SS Prompting.
-When used interactively,
-the shell prompts with the value of
-.SM
-.B PS1
-after expanding it for parameter expansion, command substitution, and
-arithmetic substitution,
-before reading a command.
-In addition, each single
-.B !
-in the prompt is replaced by the command number.
-A
-.B !!
-is required to place
-.B !
-in the prompt.
-If at any time a new-line is typed and further input is needed
-to complete a command, then the secondary prompt
-(i.e., the value of
-.BR \s-1PS2\s+1 )
-is issued.
-.SS Conditional Expressions.
-A
-.I "conditional expression"
-is used with the
-.B [[
-compound command to test attributes of files and to compare
-strings.
-Field splitting and file name generation are
-not performed on the words between
-.B [[
-and
-.BR ]] .
-Each expression can be constructed from one or more
-of the following unary or binary expressions:
-.PD 0
-.TP
-\f2string\fP
-True, if
-.I string
-is not null.
-.TP
-\f3\-a\fP \f2file\fP
-Same is \f3\-e\fP below.
-This is obsolete.
-.TP
-\f3\-b\fP \f2file\fP
-True, if
-.I file
-exists and is a block special file.
-.TP
-\f3\-c\fP \f2file\fP
-True, if
-.I file
-exists and is a character special file.
-.TP
-\f3\-d\fP \f2file\fP
-True, if
-.I file
-exists and is a directory.
-.TP
-\f3\-e\fP \f2file\fP
-True, if
-.I file
-exists.
-.TP
-\f3\-f\fP \f2file\fP
-True, if
-.I file
-exists and is an ordinary file.
-.TP
-\f3\-g\fP \f2file\fP
-True, if
-.I file
-exists and is has its setgid bit set.
-.TP
-\f3\-k\fP \f2file\fP
-True, if
-.I file
-exists and is has its sticky bit set.
-.TP
-\f3\-n\fP \f2string\fP
-True, if length of
-.I string
-is non-zero.
-.TP
-\f3\-o\fP \f2option\fP
-True, if option named
-.I option
-is on.
-.TP
-\f3\-p\fP \f2file\fP
-True, if
-.I file
-exists and is a fifo special file or a pipe.
-.TP
-\f3\-r\fP \f2file\fP
-True, if
-.I file
-exists and is readable by current process.
-.TP
-\f3\-s\fP \f2file\fP
-True, if
-.I file
-exists and has size greater than zero.
-.TP
-\f3\-t\fP \f2fildes\fP
-True, if file descriptor number
-.I fildes
-is open and associated with a terminal device.
-.TP
-\f3\-u\fP \f2file\fP
-True, if
-.I file
-exists and is has its setuid bit set.
-.TP
-\f3\-w\fP \f2file\fP
-True, if
-.I file
-exists and is writable by current process.
-.TP
-\f3\-x\fP \f2file\fP
-True, if
-.I file
-exists and is executable by current process.
-If
-.I file
-exists and is a directory, then true if the current process
-has permission to search in the directory.
-.TP
-\f3\-z\fP \f2string\fP
-True, if length of
-.I string
-is zero.
-.TP
-\f3\-L\fP \f2file\fP
-True, if
-.I file
-exists and is a symbolic link.
-.TP
-\f3\-O\fP \f2file\fP
-True, if
-.I file
-exists and is owned by the effective user id of this process.
-.TP
-\f3\-G\fP \f2file\fP
-True, if
-.I file
-exists and its group matches the effective group id of this process.
-.TP
-\f3\-S\fP \f2file\fP
-True, if
-.I file
-exists and is a socket.
-.TP
-\f2file1\fP \f3\-nt\fP \f2file2\fP
-True, if
-.I file1
-exists and is newer than
-.IR file2 .
-.TP
-\f2file1\fP \f3\-ot\fP \f2file2\fP
-True, if
-.I file1
-exists and is older than
-.IR file2 .
-.TP
-\f2file1\fP \f3\-ef\fP \f2file2\fP
-True, if
-.I file1
-and
-.I file2
-exist and refer to the same file.
-.TP
-\f2string\fP \f3==\fP \f2pattern\fP
-True, if
-.I string
-matches
-.IR pattern .
-Any part of
-.I pattern\^
-can be quoted to cause it to be matched as a string.
-.TP
-\f2string\fP \f3=\fP \f2pattern\fP
-Same as \f3==\fP above, but is obsolete.
-.TP
-\f2string\fP \f3!=\fP \f2pattern\fP
-True, if
-.I string
-does not match
-.IR pattern .
-.TP
-\f2string1\fP \f3<\fP \f2string2\fP
-True, if
-.I string1
-comes before
-.I string2
-based on ASCII value of their characters.
-.TP
-\f2string1\fP \f3>\fP \f2string2\fP
-True, if
-.I string1
-comes after
-.I string2
-based on ASCII value of their characters.
-.PP
-The following obsolete arithmetic comparisons are also permitted:
-.PD 0
-.TP
-\f2exp1\fP \f3\-eq\fP \f2exp2\fP
-True, if
-.I exp1
-is equal to
-.IR exp2 .
-.TP
-\f2exp1\fP \f3\-ne\fP \f2exp2\fP
-True, if
-.I exp1
-is not equal to
-.IR exp2 .
-.TP
-\f2exp1\fP \f3\-lt\fP \f2exp2\fP
-True, if
-.I exp1
-is less than
-.IR exp2 .
-.TP
-\f2exp1\fP \f3\-gt\fP \f2exp2\fP
-True, if
-.I exp1
-is greater than
-.IR exp2 .
-.TP
-\f2exp1\fP \f3\-le\fP \f2exp2\fP
-True, if
-.I exp1
-is less than or equal to
-.IR exp2 .
-.TP
-\f2exp1\fP \f3\-ge\fP \f2exp2\fP
-True, if
-.I exp1
-is greater than or equal to
-.IR exp2 .
-.PD
-.PP
-In each of the above expressions, if
-.I file
-is of the form
-\f3/dev/fd/\fP\f2n\fP,
-where
-.I n
-is an integer,
-then the test is applied to the open file whose
-descriptor number is
-.IR n .
-.PP
-A compound expression can be constructed from these primitives by
-using any of the following, listed in decreasing order of precedence.
-.PD 0
-.TP
-\f3(\fP\f2expression\fP\f3)\fP
-True, if
-.I expression
-is true.
-Used to group expressions.
-.TP
-\f3!\fP \f2expression\fP
-True if
-.I expression
-is false.
-.TP
-\f2expression1\fP \f3&&\fP \f2expression2\fP
-True, if
-.I expression1
-and
-.I expression2
-are both true.
-.TP
-\f2expression1\fP \f3\(bv\(bv\fP \f2expression2\fP
-True, if either
-.I expression1
-or
-.I expression2
-is true.
-.PD
-.SS Input/Output.
-Before a command is executed, its input and output
-may be redirected using a special notation interpreted by the shell.
-The following may appear anywhere in a simple-command
-or may precede or follow a
-.I command\^
-and are
-.I not\^
-passed on to the invoked command.
-Command substitution, parameter expansion,
-and arithmetic substitution occur before
-.I word\^
-or
-.I digit\^
-is used except as noted below.
-File name generation
-occurs only if the shell is interactive and
-the pattern matches a single file,
-Field splitting is not performed.
-.TP 14
-.BI < word
-Use file
-.I word\^
-as standard input (file descriptor 0).
-.TP
-.BI > word
-Use file
-.I word\^
-as standard output (file descriptor 1).
-If the file does not exist then it is created.
-If the file exists, and the
-.B noclobber
-option is on,
-this causes an error;
-otherwise, it is truncated to zero length.
-.TP
-.BI >| word
-Sames as
-.BR > ,
-except that it overrides the
-.B noclobber
-option.
-.TP
-.BI >> word
-Use file
-.I word\^
-as standard output.
-If the file exists then output is appended to it (by first seeking to the end-of-file);
-otherwise, the file is created.
-.TP
-.BI <> word
-Open file
-.I word\^
-for reading and writing
-as standard input.
-.TP
-\f3<<\fP\*(OK\f3\-\fP\*(CK\f2word\fP
-The shell input is read up to a line that is the same as
-.IR word
-after any quoting has been removed remove,
-or to an end-of-file.
-No parameter substitution, command substitution, arithmetic substitution or
-file name generation is performed on
-.IR word .
-The resulting document,
-called a
-.IR here-document ,
-becomes
-the standard input.
-If any character of
-.I word\^
-is quoted, then no interpretation
-is placed upon the characters of the document;
-otherwise, parameter expansion, command substitution, and arithmetic
-substitution occur,
-.B \enew-line
-is ignored,
-and
-.B \e
-must be used to quote the characters
-.BR \e ,
-.BR $ ,
-.BR \*` .
-If
-.B \-
-is appended to
-.BR << ,
-then all leading tabs are stripped from
-.I word\^
-and from the document.
-.TP
-.BI <& digit
-The standard input is duplicated from file descriptor
-.I digit
-(see
-.IR dup (2)).
-Similarly for the standard output using
-\f3>&\^\f2digit\fR.
-.TP
-.B <&\-
-The standard input is closed.
-Similarly for the standard output using
-.BR >&\- .
-.TP
-.B <&p
-The input from the co-process is moved to standard input.
-.TP
-.B >&p
-The output to the co-process is moved to standard output.
-.PP
-If one of the above is preceded by a digit,
-then the
-file descriptor number referred to is that specified
-by the digit
-(instead of the default 0 or 1).
-For example:
-.RS
-.PP
-\&.\|.\|. \|2>&1
-.RE
-.PP
-means file descriptor 2 is to be opened
-for writing as a duplicate
-of file descriptor 1.
-.PP
-The order in which redirections are specified is significant.
-The shell evaluates each redirection in terms of the
-.RI ( "file descriptor" ", " file )
-association at the time of evaluation.
-For example:
-.RS
-.PP
-\&.\|.\|. \|1>\f2fname\^\fP 2>&1
-.RE
-.PP
-first associates file descriptor 1 with file
-.IR fname\^ .
-It then associates file descriptor 2 with the file associated with file
-descriptor 1 (i.e.
-.IR fname\^ ).
-If the order of redirections were reversed, file descriptor 2 would be associated
-with the terminal (assuming file descriptor 1 had been) and then file descriptor
-1 would be associated with file
-.IR fname\^ .
-.PP
-If a command is followed by
-.B &
-and job control is not active,
-then the default standard input
-for the command
-is the empty file
-.BR /dev/null .
-Otherwise, the environment for the execution of a command contains the
-file descriptors of the invoking shell as modified by
-input/output specifications.
-.SS Environment.
-The
-.I environment\^
-(see
-.IR environ (7))
-is a list of name-value pairs that is passed to
-an executed program in the same way as a normal argument list.
-The names must be
-.I identifiers\^
-and the values are character strings.
-The shell interacts with the environment in several ways.
-On invocation, the shell scans the environment
-and creates a
-variable
-for each name found,
-giving it the corresponding value and attributes and marking it
-.IR export .
-Executed commands inherit the environment.
-If the user modifies the values of these
-variables
-or creates new ones,
-using the
-.B export
-or
-.B typeset \-x
-commands they become part of the
-environment.
-The environment seen by any executed command is thus composed
-of any name-value pairs originally inherited by the shell,
-whose values may be modified by the current shell,
-plus any additions
-which must be noted in
-.B export
-or
-.B typeset \-x
-commands.
-.PP
-The environment for any
-.I simple-command\^
-or function
-may be augmented by prefixing it with one or more variable assignments.
-A variable assignment argument is a word of the form
-.IR identifier=value .
-Thus:
-.RS
-.PP
-\s-1TERM\s+1=450 \|cmd \|args and
-.br
-(export \|\s-1TERM\s+1; \|\s-1TERM\s+1=450; \|cmd \|args)
-.RE
-.PP
-are equivalent (as far as the above execution of
-.I cmd\^
-is concerned except for special built-in commands listed below \-
-those that are
-preceded with a dagger).
-.PP
-If the obsolete
-.B \-k
-option is set,
-.I all\^
-variable assignment arguments are placed in the environment,
-even if they occur after the command name.
-The following
-first prints
-.B "a=b c"
-and then
-.BR c :
-.PP
-.RS
-.nf
-echo \|a=b \|c
-set \|\-k
-echo \|a=b \|c
-.fi
-.RE
-This feature is intended for use with scripts written
-for early versions of the shell and its use in new scripts
-is strongly discouraged.
-It is likely to disappear someday.
-.SS Functions.
-.PP
-For historical reasons, there are two
-ways to define functions,
-the
-.IB name (\^)
-syntax and
-the
-.B function
-.I name\^
-syntax, described in the
-.I Commands
-section above.
-Shell functions are read in and stored internally.
-Alias names are resolved when the function is read.
-Functions are executed like commands with the arguments
-passed as positional parameters.
-(See
-.I Execution
-below.)
-.PP
-Functions defined by the
-.B function
-.I name
-syntax and called by name execute in the same process as the caller and
-share all files
-and present working directory with the
-caller.
-Traps caught by the caller are reset to their default action
-inside the function.
-A trap condition that is not caught or ignored by the
-function causes the function to terminate and the condition
-to be passed on to the caller.
-A trap on
-.SM
-.B EXIT
-set inside a function
-is executed after the function completes in the environment
-of the caller.
-Ordinarily,
-variables are shared between the calling program
-and the function.
-However,
-the
-.B typeset
-special built-in command used within a function
-defines local variables whose scope includes
-the current function and
-all functions it calls.
-Errors within functions return control to the caller.
-.PP
-Functions defined with the
-.IB name (\^)
-syntax and functions defined with the
-.B function
-.I name
-syntax that are invoked with the \f3\s+2.\s-2\fP
-special built-in
-are executed in the caller's
-environment and share all variables
-and traps with the caller.
-Errors within these function executions cause the script that contains
-them to abort.
-.PP
-The special built-in command
-.B return
-is used to return
-from function calls.
-.PP
-Function names
-can be listed with the
-.B \-f
-or
-.B +f
-option of the
-.B typeset
-special built-in command.
-The text of functions, when available, will also
-be listed with
-.BR \-f .
-Functions can be undefined with the
-.B \-f
-option of the
-.B unset
-special built-in command.
-.PP
-Ordinarily, functions are unset when the shell executes a shell script.
-Functions that need to be defined across separate
-invocations of the shell should
-be placed in a directory and the
-.B
-.SM
-FPATH
-variable should contains the name of this directory.
-They may also
-be specified in the
-.B
-.SM
-ENV
-file.
-.SS Jobs.
-.PP
-If the
-.B monitor
-option of the
-.B set
-command is turned on,
-an interactive shell associates a \fIjob\fR with each pipeline.
-It keeps
-a table of current jobs, printed by the
-.B jobs
-command, and assigns them small integer numbers.
-When a job is started asynchronously with
-.BR & ,
-the shell prints a line which looks
-like:
-.PP
-.DT
- [1] 1234
-.PP
-indicating that the job which was started asynchronously was job number
-1 and had one (top-level) process, whose process id was 1234.
-.PP
-This paragraph and the next require features that are
-not in all versions of UNIX and may not apply.
-If you are running a job and wish to do something else you may hit the key
-\fB^Z\fR (control-Z) which sends a STOP signal to the current job.
-The shell will then normally indicate that the job has been `Stopped',
-and print another prompt.
-You can then manipulate the state of this job,
-putting it in the background with the
-.B bg
-command, or run some other
-commands and then eventually bring the job back into the foreground with
-the foreground command
-.BR fg .
-A \fB^Z\fR takes effect immediately and
-is like an interrupt in that pending output and unread input are discarded
-when it is typed.
-.PP
-A job being run in the background will stop if it tries to read
-from the terminal.
-Background jobs are normally allowed to produce output,
-but this can be disabled by giving the command ``stty tostop''.
-If you set this
-tty option, then background jobs will stop when they try to produce
-output like they do when they try to read input.
-.PP
-There are several ways to refer to jobs in the shell.
-A job can be referred to by the process id of any process of the job
-or by one of the following:
-.PD 0
-.TP
-.BI % number
-The job with the given number.
-.TP
-.BI % string
-Any job whose command line begins with
-.IR string .
-.TP
-.BI %? string
-Any job whose command line contains
-.IR string .
-.TP
-.BI %%
-Current job.
-.TP
-.BI %+
-Equivalent to
-.BR %% .
-.TP
-.BI %\-
-Previous job.
-.PD
-.PP
-The shell learns immediately whenever a process changes state.
-It normally informs you whenever a job becomes blocked so that
-no further progress is possible, but only just before it prints
-a prompt.
-This is done so that it does not otherwise disturb your work.
-The
-.B notify
-option causes
-the shell to print these job change messages
-as soon as they occur.
-.PP
-When the
-.B monitor
-option is on, each background job that completes
-triggers any trap set for
-.BR CHLD .
-.PP
-When you try to leave the shell while jobs are running or stopped, you will
-be warned that `You have stopped(running) jobs.'
-You may use the
-.B jobs
-command to see what they are.
-If you immediately try to
-exit again, the shell will not warn you a second time, and the stopped
-jobs will be terminated.
-When a login shell receives a HUP signal, it sends
-a HUP signal to each job that has not been disowned witha the
-.B disown
-built-in command described below.
-.SS Signals.
-The \s-1INT\s+1 and \s-1QUIT\s+1 signals for an invoked
-command are ignored if the command is followed by
-.B &
-and the
-.B monitor
-option is not active.
-Otherwise, signals have the values
-inherited by the shell from its parent
-(but see also
-the
-.B trap
-built-in command below).
-.SS Execution.
-Each time a command is read, the above substitutions
-are carried out.
-If the command name matches one
-of the
-.I "Special built-in Commands\^"
-listed below,
-it is executed within the
-current shell process.
-Next, the command name is checked to see if
-it matches a user defined function.
-If it does,
-the positional parameters are saved
-and then reset to the arguments of the
-.I function\^
-call.
-When the
-.I function\^
-completes or issues a
-.BR return ,
-the positional parameter list is restored.
-For functions defined with the
-.B function
-.I name\^
-syntax,
-any trap set on
-.SM
-.B EXIT
-within the function is executed.
-The value of a
-.I function\^
-is the value of the last command executed.
-A function is also executed in the
-current shell process.
-If a command name is not a
-.I "special built-in command\^"
-or a user defined
-.IR function ,
-but it is one of the built-in commands listed below
-it is executed in the current shell process.
-.PP
-The shell variable
-.B
-.SM PATH
-defines the search path for
-the directory containing the command.
-Alternative directory names are separated by
-a colon
-.RB ( : ).
-The default path is
-.B /bin:/usr/bin:
-(specifying
-.BR /bin ,
-.BR /usr/bin ,
-and the current directory
-in that order).
-The current directory can be specified by
-two or more adjacent colons, or by a colon
-at the beginning or end of the path list.
-If the command name contains a \f3/\fP then the search path
-is not used.
-Otherwise, each directory in the path is
-searched for an executable file that is not a directory.
-If the shell
-determines that there is a built-in version
-of a command corresponding to a given pathname,
-this built-in is invoked in the current process.
-A process is created and
-an attempt is made to execute the command via
-.IR exec (2).
-If the file has execute permission but is not an
-.B a.out
-file,
-it is assumed to be a file containing shell commands.
-A separate shell is spawned to read it.
-All non-exported variables are removed in this case.
-If the shell command
-file doesn't have read permission,
-or if the
-.I setuid
-and/or
-.I setgid
-bits are set on the file,
-then the shell executes an agent whose job it is to
-set up the permissions and execute the shell with the
-shell command file passed down as an open file.
-A parenthesized command is executed in
-a sub-shell without removing non-exported variables.
-.SS Command Re-entry.
-The text of the last
-.B
-.SM
-HISTSIZE
-(default 128)
-commands entered from a terminal device
-is saved in a
-.I history
-file.
-The file
-.B \s-1$HOME\s+1/.sh_history
-is used if the
-.B
-.SM
-HISTFILE
-variable is not set
-or if the file it names is not writable.
-A shell can access the commands of
-all
-.I interactive
-shells which use the same named
-.SM
-.BR HISTFILE .
-The built-in command
-.B hist\^
-is used to list or
-edit a portion of this file.
-The portion of the file to be edited or listed can be selected by
-number or by giving the first character or
-characters of the command.
-A single command or range of commands can be specified.
-If you do not specify an editor program as
-an argument to
-.B hist\^
-then the value of the variable
-.SM
-.B HISTEDIT
-is used.
-If
-.SM
-.B HISTEDIT
-is unset, the obsolete variable
-.SM
-.B FCEDIT
-is used.
-If
-.SM
-.B FCEDIT
-is not defined then
-.B /bin/ed
-is used.
-The edited command(s) is printed and re-executed upon
-leaving the editor unless you quit without writing.
-The
-.B \-s
-option
-(
-an in obsolete versions, the editor name
-.B \-
-)
-is used to skip the editing phase and
-to re-execute the command.
-In this case a substitution parameter of the form
-\f2old\fP\f3=\fP\f2new\fP
-can be used to modify the command before execution.
-For example, with the preset alias
-.BR r ,
-which is aliased to
-.BR "\(fmhist \-s\(fm" ,
-typing
-`\f3r bad=good c\fP'
-will re-execute the most recent command which starts with the letter
-.BR c ,
-replacing the first occurrence of the string
-.B bad
-with the string
-.BR good .
-.SS In-line Editing Options
-Normally, each command line entered from a terminal device is simply
-typed followed by a \f3new-line\fP (`RETURN' or `LINE\ FEED').
-If either the
-.BR emacs ,
-.BR gmacs ,
-or
-.B vi
-option is active, the user can edit the command line.
-To be in either of these edit modes
-.B set
-the corresponding
-option.
-An editing option is automatically selected each time the
-.SM
-.B VISUAL
-or
-.SM
-.B EDITOR
-variable is assigned a value ending in either of these
-option names.
-.PP
-The editing features require that the user's terminal
-accept `RETURN' as carriage return without line feed
-and that a space (`\ ') must overwrite the current character on
-the screen.
-.PP
-The editing modes implement a concept where the user is looking through a
-window at the current line.
-The window width is the value of
-.SM
-.B COLUMNS
-if it is defined, otherwise 80.
-If the window width is too small to display the prompt and leave
-at least 8 columns to enter input, the prompt is truncated from the
-left.
-If the line is longer than the window width minus two, a mark is
-displayed at the end of the window to notify the user.
-As the cursor moves and reaches the window boundaries the window will be
-centered about the cursor.
-The mark is a
-.BR > " (<" ,
-.BR * )
-if the line extends on the
-right (left, both) side(s) of the window.
-.PP
-The search commands in each edit mode provide access to the history file.
-Only strings are matched, not patterns, although a leading
-.B ^
-in the string restricts the match
-to begin at the first character in the line.
-.PP
-Each of the edit modes has an operation to list the files
-or commands that match a partially entered word.
-When applied to the first word on the line,
-or the first word after a
-.BR ; ,
-.BR \(bv ,
-.BR & ,
-or
-.BR ( ,
-and the word does not begin with
-.B \(ap
-or contain a
-.BR / ,
-the list of aliases, functions, and executable commands
-defined by the
-.B
-.SM PATH
-variable that could match the partial word is displayed.
-Otherwise, the list of files that match the given
-word is displayed.
-If the partially entered word does not contain any
-file expansion characters, a
-.B *
-is appended before generating these lists.
-After displaying the generated list, the input line
-is redrawn.
-These operations are called command name listing and file name listing,
-respectively.
-There are additional operations, referred to as command name
-completion and file name completion, which compute the list
-of matching commands or files, but instead of printing the list,
-replace
-the current word with a complete or partial match.
-For file name completion,
-if the match is unique, a
-.B /
-is appended if the file is a directory and a space is
-appended if the file is not a directory.
-Otherwise, the longest common prefix for all the matching
-files replaces the word.
-For command name completion, only the portion of the file names
-after the last
-.B /
-are used to find the longest command prefix.
-If only a single name matches this prefix, then the
-word is replaced with the command name followed by a space.
-.SS Key Bindings.
-The
-.B
-.SM KEYBD
-trap can be used to intercept keys as they are typed
-and change the characters that are actually seen by
-the shell.
-This trap is executed after each character
-( or sequence of characters when the first character is
-.B ESC
-) is entered while reading from a terminal.
-The variable
-.B .sh.edchar
-contains the character or character sequence which
-generated the trap.
-Changing the value of
-.B .sh.edchar
-in the trap action causes the shell to behave as if the
-new value were entered from the keyboard rather than
-the original value.
-.PP
-The variable
-.B .sh.edcol
-is set to the input column number of the cursor at the time
-of the input.
-The variable
-.B .sh.edmode
-is set to
-.B ESC
-when in vi insert mode (see below) and is null otherwise.
-By prepending
-.B ${.sh.editmode}
-to a value assigned to
-.B .sh.edchar
-it will cause the shell
-to change to control mode if it is not already in this mode.
-.PP
-This trap is not invoked for characters entered as arguments to
-editing directives, or while reading input for a character search.
-.SS Emacs Editing Mode.
-This mode is entered by enabling either the
-.I emacs
-or
-.I gmacs
-option.
-The only difference between these two modes is the way
-they handle
-.BR ^T .
-To edit, the user
-moves the cursor to the point needing correction and
-then inserts or deletes characters or words as needed.
-All the editing commands are control characters or escape
-sequences.
-The notation for control characters is caret (
-.B ^
-) followed
-by the character.
-For example,
-.B ^F
-is the notation for control
-.BR F .
-This is entered by depressing `f' while holding down the
-`CTRL' (control) key.
-The `SHIFT' key is
-.I not
-depressed.
-(The notation
-.B ^?
-indicates the DEL (delete) key.)
-.PP
-The notation for escape sequences is
-.B M-
-followed by a
-character.
-For example,
-.B M-f
-(pronounced Meta f)
-is entered by depressing ESC
-(ascii
-.BR 033 )
-followed by `f'.
-.RB ( M-F
-would be the notation for ESC followed by `SHIFT' (capital) `F'.)
-.PP
-All edit commands
-operate from any place on the line
-(not just at the beginning).
-Neither the "RETURN" nor the "LINE FEED" key is
-entered after edit commands except when noted.
-.PP
-.PD 0
-.TP 10
-.BI ^F
-Move cursor forward (right) one character.
-.PP
-.TP 10
-.BI M-f
-Move cursor forward one word.
-(The
-.B emacs
-editor's idea of a word is a string of characters
-consisting of only letters, digits and underscores.)
-.PP
-.TP 10
-.BI ^B
-Move cursor backward (left) one character.
-.PP
-.TP 10
-.BI M-b
-Move cursor backward one word.
-.PP
-.TP 10
-.BI ^A
-Move cursor to start of line.
-.PP
-.TP 10
-.BI ^E
-Move cursor to end of line.
-.PP
-.TP 10
-.BI ^] char
-Move cursor forward to character
-.I char
-on current line.
-.PP
-.TP 10
-.BI M-^] char
-Move cursor backward to character
-.I char
-on current line.
-.PP
-.TP 10
-.BI ^X^X
-Interchange the cursor and mark.
-.PP
-.TP 10
-.I erase
-(User defined erase character as defined
-by the
-.IR stty (1)
-command, usually
-.B ^H
-or
-.BR # .)
-Delete previous character.
-.PP
-.TP 10
-.BI ^D
-Delete current character.
-.PP
-.TP 10
-.BI M-d
-Delete current word.
-.PP
-.TP 10
-.BI M-^H
-(Meta-backspace) Delete previous word.
-.PP
-.TP 10
-.BI M-h
-Delete previous word.
-.PP
-.TP 10
-.BI M-^?
-(Meta-DEL) Delete previous word (if your interrupt character is
-.B ^?
-(DEL, the default) then this command will not work).
-.PP
-.TP 10
-.BI ^T
-Transpose current character with next character in
-.I emacs
-mode.
-Transpose two previous characters in
-.I gmacs
-mode.
-.PP
-.TP 10
-.BI ^C
-Capitalize current character.
-.PP
-.TP 10
-.BI M-c
-Capitalize current word.
-.PP
-.TP 10
-.BI M-l
-Change the current word to lower case.
-.PP
-.TP 10
-.BI ^K
-Delete from the cursor to the end of the line.
-If preceded by a numerical parameter whose value is less than the
-current cursor position, then delete from given position
-up to the cursor.
-If preceded by a numerical parameter whose value is greater than the
-current cursor position, then delete from cursor up to
-given cursor position.
-.PP
-.TP 10
-.BI ^W
-Kill from the cursor to the mark.
-.PP
-.TP 10
-.BI M-p
-Push the region from the cursor to the mark on the stack.
-.PP
-.TP 10
-.I kill
-(User defined kill character as defined
-by the stty command, usually
-.B ^G
-or
-.BR @ .)
-Kill the entire current line.
-If two
-.I kill
-characters are entered in succession, all
-kill characters from then on cause a line feed
-(useful when using paper terminals).
-.PP
-.TP 10
-.BI ^Y
-Restore last item removed from line. (Yank item back to the line.)
-.PP
-.TP 10
-.BI ^L
-Line feed and print current line.
-.PP
-.TP 10
-.BI ^@
-(Null character) Set mark.
-.PP
-.TP 10
-.BI M- space
-(Meta space) Set mark.
-.PP
-.TP 10
-.BI ^J
-(New\ line) Execute the current line.
-.PP
-.TP 10
-.BI ^M
-(Return) Execute the current line.
-.PP
-.TP 10
-.I eof
-End-of-file character,
-normally
-.BR ^D ,
-is processed as an End-of-file only
-if the current line is null.
-.PP
-.TP 10
-.BI ^P
-Fetch previous command.
-Each time
-.B ^P
-is entered
-the previous command back in time is accessed.
-Moves back one line when not on the first line of a multi-line command.
-.PP
-.TP 10
-.BI M-<
-Fetch the least recent (oldest) history line.
-.PP
-.TP 10
-.BI M->
-Fetch the most recent (youngest) history line.
-.PP
-.TP 10
-.BI ^N
-Fetch next command line.
-Each time
-.B ^N
-is entered
-the next command line forward in time is accessed.
-.PP
-.TP 10
-.BI ^R string
-Reverse search history for a previous command line containing
-.IR string .
-If a parameter of zero is given, the search is forward.
-.I String
-is terminated by a "RETURN" or "NEW\ LINE".
-If string is preceded by a
-.BR ^ ,
-the matched line must begin with
-.IR string .
-If
-.I string
-is omitted,
-then the next command line containing the most recent
-.I string
-is accessed.
-In this case a parameter of zero
-reverses the direction of the search.
-.PP
-.TP 10
-.B ^O
-Operate \- Execute the current line and fetch
-the next line relative to current line from the
-history file.
-.PP
-.TP 10
-.BI M- digits
-(Escape) Define numeric parameter, the digits
-are taken as a parameter to the next command.
-The commands that accept a parameter are
-.BR ^F ,
-.BR ^B ,
-.IR erase ,
-.BR ^C ,
-.BR ^D ,
-.BR ^K ,
-.BR ^R ,
-.BR ^P ,
-.BR ^N ,
-.BR ^] ,
-.BR M-. ,
-.BR M-^] ,
-.BR M-_ ,
-.BR M-b ,
-.BR M-c ,
-.BR M-d ,
-.BR M-f ,
-.BR M-h ,
-.B M-l
-and
-.BR M-^H .
-.PP
-.TP 10
-.BI M- letter
-Soft-key \- Your alias list is searched for an
-alias by the name
-.BI _ letter
-and if an alias of this name is defined, its
-value will be inserted on the input queue.
-The
-.I letter
-must not be one of the above meta-functions.
-.PP
-.TP 10
-.BI M-[ letter
-Soft-key \- Your alias list is searched for an
-alias by the name
-.BI _\&_ letter
-and if an alias of this name is defined, its
-value will be inserted on the input queue.
-The can be used to program functions keys on many terminals.
-.PP
-.TP 10
-.B M-.
-The last word of the previous command is inserted
-on the line.
-If preceded by a numeric parameter, the value
-of this parameter determines which word to insert rather than
-the last word.
-.PP
-.TP 10
-.B M-_
-Same as
-.BR M-. .
-.PP
-.TP 10
-.B M-*
-Attempt file name generation on the current word.
-An asterisk is appended if the word doesn't match any file
-or contain any special
-pattern characters.
-.PP
-.TP 10
-Command or file name completion as described above.
-.PP
-.TP 10
-.B M-=
-Command or file name listing as described above.
-.PP
-.TP 10
-.BI ^U
-Multiply parameter of next command by 4.
-.PP
-.TP 10
-.BI \e
-Escape next character.
-Editing characters, the user's erase, kill and
-interrupt (normally
-.BR ^? )
-characters
-may be entered
-in a command line or in a search string if preceded by a
-.BR \e .
-The
-.B \e
-removes the next character's
-editing features (if any).
-.PP
-.TP 10
-.BI ^V
-Display version of the shell.
-.PP
-.TP 10
-.BI M-\#
-If the line does not begin with a
-.BR \# ,
-a
-.B \#
-is inserted
-at the beginning of the line
-and after each new-line,
-and the line is entered.
-This causes a comment to be inserted in the history file.
-If the line begins with a
-.BR \# ,
-the
-.B \#
-is deleted and one
-.B \#
-after each new-line is also deleted.
-.PD
-.SS Vi Editing Mode.
-There are two typing modes.
-Initially, when you enter a command you are in the
-.I input\^
-mode.
-To edit, the user enters
-.I control\^
-mode by typing ESC
-.RB ( 033 )
-and moves the cursor to the point needing correction and
-then inserts or deletes characters or words as needed.
-Most control commands accept an optional repeat
-.I count
-prior to the command.
-.P
-When in
-.B vi
-mode on most systems,
-canonical processing is initially enabled and the
-command will be echoed again if the speed is 1200 baud or greater and it
-contains any control characters or less than one second has elapsed
-since the prompt was printed.
-The ESC character terminates canonical processing for the remainder of the command
-and the user can then modify the command line.
-This scheme has the advantages of canonical processing with the type-ahead
-echoing of raw mode.
-.P
-If the option
-.B viraw\^
-is also set, the terminal will always have canonical processing
-disabled.
-This mode is implicit for systems that do not support two
-alternate end of line delimiters,
-and may be helpful for certain terminals.
-.SS "\ \ \ \ \ Input Edit Commands"
-.PP
-.RS
-By default the editor is in input mode.
-.PD 0
-.TP 10
-.I erase
-(User defined erase character as defined
-by the stty command, usually
-.B ^H
-or
-.BR # .)
-Delete previous character.
-.TP 10
-.BI ^W
-Delete the previous blank separated word.
-One some systems the \f3viraw\fP option
-may be required for this to work.
-.TP 10
-.I eof
-As the first character of the line causes
-the shell to terminate unless the \f3ignoreeof\fP
-option is set.
-Otherwise this character is ignored.
-.TP 10
-.BI ^V
-Escape next character.
-Editing characters and the user's erase or kill
-characters may be entered
-in a command line or in a search string if preceded by a
-.BR ^V .
-The
-.B ^V
-removes the next character's
-editing features (if any).
-One some systems the \f3viraw\fP option
-may be required for this to work.
-.TP 10
-.BI \e
-Escape the next
-.I erase
-or
-.I kill
-character.
-.P
-.RE
-.SS "\ \ \ \ \ Motion Edit Commands"
-.RS
-These commands will move the cursor.
-.TP 10
-[\f2count\fP]\f3l\fP
-Cursor forward (right) one character.
-.TP 10
-[\f2count\fP]\f3w\fP
-Cursor forward one alpha-numeric word.
-.TP 10
-[\f2count\fP]\f3W\fP
-Cursor to the beginning of the next word that follows a blank.
-.TP 10
-[\f2count\fP]\f3e\fP
-Cursor to end of word.
-.TP 10
-[\f2count\fP]\f3E\fP
-Cursor to end of the current blank delimited word.
-.TP 10
-[\f2count\fP]\f3h\fP
-Cursor backward (left) one character.
-.TP 10
-[\f2count\fP]\f3b\fP
-Cursor backward one word.
-.TP 10
-[\f2count\fP]\f3B\fP
-Cursor to preceding blank separated word.
-.TP 10
-[\f2count\fP]\f3\(bv\fP
-Cursor to column
-.IR count .
-.TP 10
-[\f2count\fP]\f3f\fP\f2c\fP
-Find the next character \fIc\fP in the current line.
-.TP 10
-[\f2count\fP]\f3F\fP\f2c\fP
-Find the previous character \fIc\fP in the current line.
-.TP 10
-[\f2count\fP]\f3t\fP\f2c\fP
-Equivalent to
-.B f
-followed by
-.BR h .
-.TP 10
-[\f2count\fP]\f3T\fP\f2c\fP
-Equivalent to
-.B F
-followed by
-.BR l .
-.TP 10
-[\f2count\fP]\f3;\fP
-Repeats
-.I count
-times,
-the last single character find command,
-.BR f ,
-.BR F ,
-.BR t ,
-or
-.BR T .
-.TP 10
-[\f2count\fP]\f3,\fP
-Reverses the last single character find command
-.I count
-times.
-.TP 10
-.B 0
-Cursor to start of line.
-.TP 10
-.B ^
-Cursor to first non-blank character in line.
-.TP 10
-.B $
-Cursor to end of line.
-.TP 10
-.B %
-Moves to balancing
-.BR ( ,
-.BR ) ,
-.BR { ,
-.BR } ,
-.BR [ ,
-or
-.BR ] .
-If cursor is not on one of the above characters,
-the remainder of the line is searched for the first
-occurrence of one of the above characters first.
-.RE
-.SS "\ \ \ \ \ Search Edit Commands"
-.RS
-These commands access your command history.
-.TP 10
-[\f2count\fP]\f3k\fP
-Fetch previous command.
-Each time
-.B k
-is entered
-the previous command back in time is accessed.
-.TP 10
-[\f2count\fP]\f3\-\fP
-Equivalent to
-.BR k .
-.TP 10
-[\f2count\fP]\f3j\fP
-Fetch next command.
-Each time
-.B j
-is entered
-the next command forward in time is accessed.
-.TP 10
-[\f2count\fP]\f3+\fP
-Equivalent to
-.BR j .
-.TP 10
-[\f2count\fP]\f3G\fP
-The command number
-.I count
-is fetched.
-The default is the least recent history command.
-.TP 10
-.BI / string
-Search backward through history for a previous command containing
-.IR string .
-.I String
-is terminated by a "RETURN" or "NEW\ LINE".
-If string is preceded by a
-.BR ^ ,
-the matched line must begin with
-.IR string .
-If \fIstring\fP is null the previous string will be used.
-.TP 10
-.BI ? string
-Same as
-.B /
-except that search will be in the forward direction.
-.TP 10
-.B n
-Search for next match of the last pattern to
-.B /
-or
-.B ?
-commands.
-.TP 10
-.B N
-Search for next match of the last pattern to
-.B /
-or
-.BR ? ,
-but in reverse direction.
-.RE
-.SS "\ \ \ \ \ Text Modification Edit Commands"
-.RS
-These commands will modify the line.
-.TP 10
-.B a
-Enter input mode and enter text after the current character.
-.TP 10
-.B A
-Append text to the end of the line.
-Equivalent to
-.BR $a .
-.TP 10
-[\f2count\fP]\f3c\fP\f2motion\fP
-.TP 10
-\f3c\fP[\f2count\fP]\f2motion\fP
-Delete current character through the character that
-.I motion
-would move the cursor to and enter input mode.
-If \fImotion\fP is
-.BR c ,
-the entire line will be deleted and
-input mode entered.
-.TP 10
-.B C
-Delete the current character through the end of line and enter input mode.
-Equivalent to
-.BR c$ .
-.TP 10
-.B S
-Equivalent to
-.BR cc .
-.TP 10
-.B D
-Delete the current character through the end of line.
-Equivalent to
-.BR d$ .
-.TP 10
-[\f2count\fP]\f3d\fP\f2motion\fP
-.TP 10
-\f3d\fP[\f2count\fP]\f2motion\fP
-Delete current character through the character that
-.I motion
-would move to.
-If \fImotion\fP is
-.B d ,
-the entire line will be deleted.
-.TP 10
-.B i
-Enter input mode and insert text before the current character.
-.TP 10
-.B I
-Insert text before the beginning of the line.
-Equivalent to
-.BR 0i .
-.TP 10
-[\f2count\fP]\f3P\fP
-Place the previous text modification before the cursor.
-.TP 10
-[\f2count\fP]\f3p\fP
-Place the previous text modification after the cursor.
-.TP 10
-.B R
-Enter input mode and
-replace characters on the screen with characters you type overlay fashion.
-.TP 10
-[\f2count\fP]\f3r\fP\f2c\fP
-Replace the
-.I count
-character(s) starting at the current cursor position with
-.IR c ,
-and advance the cursor.
-.TP 10
-[\f2count\fP]\f3x\fP
-Delete current character.
-.TP 10
-[\f2count\fP]\f3X\fP
-Delete preceding character.
-.TP 10
-[\f2count\fP]\f3.\fP
-Repeat the previous text modification command.
-.TP 10
-[\f2count\fP]\f3\(ap\fP
-Invert the case of the
-.I count
-character(s) starting at the current cursor position and advance the cursor.
-.TP 10
-[\f2count\fP]\f3_\fP
-Causes the
-.I count\^
-word of the previous command to be appended and
-input mode entered.
-The last word is used
-if
-.I count\^
-is omitted.
-.TP 10
-.B *
-Causes an
-.B *
-to be appended to the current word and file name generation attempted.
-If no match is found,
-it rings the bell.
-Otherwise, the word is replaced
-by the matching pattern and input mode is entered.
-.TP 10
-.B \e
-Command or file name completion as described above.
-.RE
-.SS "\ \ \ \ \ Other Edit Commands"
-.RS
-Miscellaneous commands.
-.TP 10
-[\f2count\fP]\f3y\fP\f2motion\fP
-.TP 10
-\f3y\fP[\f2count\fP]\f2motion\fP
-Yank current character through character that
-.I motion
-would move the cursor to and puts them into the delete buffer.
-The text and cursor are unchanged.
-.TP 10
-.B Y
-Yanks from current position to end of line.
-Equivalent to
-.BR y$ .
-.TP 10
-.B u
-Undo the last text modifying command.
-.TP 10
-.B U
-Undo all the text modifying commands performed on the line.
-.TP 10
-[\f2count\fP]\f3v\fP
-Returns the command
-.BI "hist \-e ${\s-1VISUAL\s+1:\-${\s-1EDITOR\s+1:\-vi}}" " count"
-in the input buffer.
-If
-.I count\^
-is omitted, then the current line is used.
-.TP 10
-.BI ^L
-Line feed and print current line.
-Has effect only in control mode.
-.TP 10
-.BI ^J
-(New\ line) Execute the current line, regardless of mode.
-.TP 10
-.BI ^M
-(Return) Execute the current line, regardless of mode.
-.TP 10
-.B \#
-If the first character of the command is a
-.BR \# ,
-then this command deletes this
-.B \#
-and each
-.B \#
-that follows a newline.
-Otherwise,
-sends the line after
-inserting a
-.B \#
-in front of each line in the command.
-Useful for causing the current line to be
-inserted in the history as a comment and
-uncommenting previously commented commands
-in the history file.
-.TP 10
-.B =
-Command or file name listing as described above.
-.TP 10
-.BI @ letter
-Your alias list is searched for an
-alias by the name
-.BI _ letter
-and if an alias of this name is defined, its
-value will be inserted on the input queue for processing.
-.RE
-.PD
-.SS Built-in Commands.
-The following simple-commands are executed in the shell process.
-Input/Output redirection is permitted.
-Unless otherwise indicated, the output is written on file descriptor 1
-and the exit status, when there is no syntax error, is zero.
-Except for
-.BR : ,
-.BR true ,
-.BR false ,
-.BR echo ,
-.BR command ,
-.BR newgrp ,
-and
-.BR login ,
-all built-in commands accept
-.B \-\-
-to indicate end of options.
-They also interpret the option
-.B \-?
-as a help request and print a
-.I usage\^
-message
-on standard error.
-Commands that are preceded by one or two \(dg
-are special built-in commands and
-are treated specially in the following ways:
-.PD 0
-.TP
-1.
-Variable assignment lists preceding the command
-remain in effect when the command completes.
-.TP
-2.
-I/O redirections are processed after variable assignments.
-.TP
-3.
-Errors
-cause a script
-that contains them to abort.
-.TP
-4.
-They are not valid function names.
-.TP
-5.
-Words,
-following a command preceded by \(dg\(dg
-that are in the format of a variable assignment,
-are expanded with the same rules as a variable assignment.
-This means that
-tilde substitution is performed after the
-.B =
-sign and field splitting and file name generation are not
-performed.
-.PD
-.TP
-\(dg \f3:\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-The command only expands parameters.
-.br
-.ne 2
-.TP
-\(dg \f3\|. \f2name\^\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-If
-.I name\^
-is a function defined with the
-.B function
-.I name\^
-reserved word syntax,
-the function is executed in the current environment
-( as if it had been defined with the
-.IB name ()
-syntax.)
-Otherwise if
-.I name\^
-refers to a file, the
-file is read in its entirety and the commands are
-executed in the current shell environment.
-The search path
-specified by
-.B
-.SM PATH
-is used to find the directory containing file.
-If any arguments
-.I arg\^
-are given,
-they become the positional parameters while processing
-the
-.B .
-command and are restored upon completion.
-Otherwise the positional parameters are unchanged.
-The exit status is the exit status of the last command executed.
-.TP
-\(dg\(dg \f3alias\fP \*(OK \f3\-ptx\fP \*(CK \*(OK \f2name\fP\*(OK \f3=\fP\f2value\^\fP \*(CK \*(CK .\|.\|.
-.B alias\^
-with no arguments prints the list of aliases
-in the form
-.I name=value\^
-on standard output.
-The
-.B \-p
-option
-causes the word
-.B alias
-to be inserted before each one.
-When one or more arguments are given
-an
-.I alias\^
-is defined
-for each
-.I name\^
-whose
-.I value\^
-is given.
-A trailing space in
-.I value\^
-causes the next word to be checked for
-alias substitution.
-The obsolete
-.B \-t
-option is used to set and list tracked aliases.
-The value of a tracked alias is the full pathname
-corresponding to the given
-.IR name .
-The value becomes undefined when the value of
-.SM
-.B PATH
-is reset but the alias remains tracked.
-Without the
-.B \-t
-option,
-for each
-.I name\^
-in the argument list
-for which no
-.I value\^
-is given, the name
-and value of the alias is printed.
-The obsolete
-.B \-x
-option has no effect.
-The exit status is non-zero if a
-.I name\^
-is given, but no value, and no alias has been defined for the
-.IR name\^ .
-.TP
-\f3bg\fP \*(OK \f2job\^\fP.\|.\|. \*(CK
-This command is only on systems that support job control.
-Puts each specified
-.I job\^
-into the background.
-The current job is put in the background
-if
-.I job\^
-is not specified.
-See
-.I Jobs
-for a description of the format of
-.IR job .
-.TP
-\(dg \f3break\fP \*(OK \f2n\^\fP \*(CK
-Exit from the enclosing
-.BR for\^ ,
-.BR while\^ ,
-.BR until\^ ,
-or
-.B select\^
-loop, if any.
-If
-.I n\^
-is specified then break
-.I n\^
-levels.
-.TP
-\f3builtin\fP \*(OK \f3\-ds\fP \*(CK \*(OK \f3\-f\fP \f2file\^\fP \*(CK \*(OK \f2name\^\fP .\|.\|. \*(CK
-If
-.I name\^
-is not specified, the built-ins are printed on standard output.
-The
-.B \-s
-option prints only the special built-ins.
-Otherwise, each
-.I name\^
-represents the pathname whose basename is the name of the built-in.
-The entry point function name is determined by prepending
-.B b_
-to the built-in name.
-Special built-ins cannot be bound to a pathname or deleted.
-The
-.B \-d
-option deletes each of the given built-ins.
-On systems that support dynamic loading, the
-.B \-f
-option names a shared library containing the code for built-ins.
-Once a library is loaded, its symbols become available
-for subsequent invocations of
-.BR builtin .
-Multiple libraries can be specified with separate invocations
-of the
-.B builtin
-command.
-Libraries are searched in the reverse order in which they are specified.
-.TP
-.PD 0
-\f3cd\fP \*(OK \f3\-LP\fP \*(CK \*(OK \f2arg\^\fP \*(CK
-.TP
-\f3cd\fP \*(OK \f3\-LP\fP \*(CK \f2old\^\fP \f2new\^\fP
-.PD
-This command can be in either of two forms.
-In the first form it
-changes the current directory to
-.IR arg .
-If
-.I arg\^
-is
-.B \-
-the directory is changed to the previous
-directory.
-The shell
-variable
-.B
-.SM HOME
-is the default
-.IR arg .
-The variable
-.SM
-.B PWD
-is set to the current directory.
-The shell variable
-.B
-.SM CDPATH
-defines the search path for
-the directory containing
-.IR arg .
-Alternative directory names are separated by
-a colon
-.RB ( : ).
-The default path is
-.B <null>
-(specifying the current directory).
-Note that the current directory is specified by a null path name,
-which can appear immediately after the equal sign
-or between the colon delimiters anywhere else in the path list.
-If
-.I arg
-begins with a \f3/\fP then the search path
-is not used.
-Otherwise, each directory in the path is
-searched for
-.IR arg .
-.P
-The obsolete second form of
-.B cd
-substitutes the string
-.I new
-for the string
-.I old
-in the current directory name,
-.SM
-.B PWD
-and tries to change to this new directory.
-.P
-By default, symbolic links are not followed when
-finding the directory name.
-This is equivalent to the
-.B \-L
-option.
-The
-.B \-P
-option causes
-symbolic links to be followed when determining the directory.
-The last instance of
-.B \-L
-or
-.B \-P
-determines which method is used.
-.P
-The
-.B cd\^
-command may not be executed by
-.if \nZ=0 .B rsh\^.
-.if \nZ=1 .B rksh\^.
-.TP
-\f3command\fP \*(OK \f3\-pvV\fP \*(CK \f2name\^\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-Without the
-.B \-v
-or
-.B \-V
-options,
-.B command
-executes
-.I name\^
-with the arguments given by
-.IR arg .
-The
-.B \-p
-option causes
-a default path to be searched
-rather than the one defined by the value of
-.SM
-.BR PATH .
-Functions will not be searched for when finding
-.IR name .
-In addition, if
-.I name\^
-refers to a special built-in,
-none of the special properties associated with the leading
-daggers will be honored.
-(
-For example, the predefined alias
-.B "redirect=\(fmcommand exec\(fm"
-prevents a script from terminating when an invalid
-redirection is given.)
-With the
-.B \-v
-option,
-.B command
-is equivalent to the built-in
-.B whence
-command described below.
-The
-.B \-V
-options, causes
-.B command
-to
-.BR "whence \-v" .
-.TP
-\(dg \f3continue\fP \*(OK \f2n\^\fP \*(CK
-Resume the next iteration of the enclosing
-.BR for\^ ,
-.BR while\^ ,
-.BR until\^ ,
-or
-.B select\^
-loop.
-If
-.I n\^
-is specified then resume at the
-.IR n -th
-enclosing loop.
-.TP
-\f3disown\fP \*(OK \f2job\^\fP.\|.\|. \*(CK
-Causes the shell not to send a HUP signal to
-each given
-.IR job ,
-or all active jobs if
-.I job
-is omitted,
-when a login shell terminates.
-.TP
-\f3echo\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-When the first
-.I arg\^
-does not begin with a \-, and
-none of the arguments contain a \e,
-then
-.B echo
-prints each of its arguments separated by a space
-and terminated by a new-line.
-Otherwise, the behavior of
-.B echo
-is system dependent
-and
-.B print
-or
-.B printf
-described below should be used.
-See
-.IR echo (1)
-for usage and description.
-.TP
-\(dg \f3eval\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-The arguments are read as input
-to the shell
-and the resulting command(s) executed.
-.TP
-\(dg \f3exec\fP \*(OK \f3\-c\fP \*(CK \*(OK \f3\-a\fP \f2name\^\fP \*(CK \*(OK \f2arg\^\fP .\|.\|. \*(CK
-If
-.I arg\^
-is given,
-the command specified by
-the arguments is executed in place of this shell
-without creating a new process.
-The
-.B \-c
-option causes the environment to be cleared before applying
-variable assignments associated with the
-.B exec
-invocation.
-The
-.B \-a
-option
-causes
-.I name\^
-rather than the first
-.IR arg ,
-to become
-.B argv[0]
-for the new process.
-Input/output arguments may appear and
-affect the current process.
-If
-.I arg\^
-is not given
-the effect of this command is to
-modify file descriptors
-as prescribed by the input/output redirection list.
-In this case,
-any file descriptor numbers greater than 2 that are
-opened with this mechanism are closed when invoking
-another program.
-.TP
-\(dg \f3exit\fP \*(OK \f2n\^\fP \*(CK
-Causes the shell to exit
-with the exit status specified by
-.IR n .
-The value will be the least significant 8 bits of the specified status.
-If
-.I n\^
-is omitted then the exit status is that of the last command executed.
-An end-of-file will also cause the shell to exit
-except for a
-shell which has the
-.I ignoreeof
-option (see
-.B set
-below) turned on.
-.TP
-\(dg\(dg \f3export\fP \*(OK \f3\-p\fP \*(CK \*(OK \f2name\^\fP\*(OK\f3=\fP\f2value\^\fP\*(CK \*(CK .\|.\|.
-If
-.I name\^
-is not given,
-the names and values of each variable with
-the export attribute are printed with the values
-quoted in a manner that allows them to be re-inputed.
-The
-.B \-p
-option
-causes the word
-.B export
-to be inserted before each one.
-Otherwise, the given
-.IR name s
-are marked for automatic
-export to the
-.I environment\^
-of subsequently-executed commands.
-.TP
-\f3fg\fP \*(OK \f2job\^\fP.\|.\|. \*(CK
-This command is only on systems that support job control.
-Each
-.I job\^
-specified is brought to the foreground and waited for in
-the specified order.
-Otherwise, the current job is
-brought into the foreground.
-See
-.I Jobs
-for a description of the format of
-.IR job .
-.TP
-\f3getconf\fP \f2name\^\fP \*(OK \f2pathname\^\fP \*(CK
-Prints the current value of the configuration parameter given by
-.IR name .
-.TP
-\f3getopts\fP \f2optstring vname\^\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-Checks
-.I arg
-for legal options.
-If
-.I arg
-is omitted,
-the positional parameters are used.
-An option argument begins with a
-.B +
-or a
-.BR \- .
-An option not beginning with
-.B +
-or
-.B \-
-or the argument
-.B \-\|\-
-ends the options.
-.I optstring
-contains the letters that
-.I getopts
-recognizes.
-If a letter is followed by a
-.BR : ,
-that option is expected to have an argument.
-The options can be separated from the argument by blanks.
-.P
-.B
-getopts
-places the next option letter it finds inside variable
-.I vname\^
-each time it is invoked with a
-.B +
-prepended when
-.I arg
-begins with a
-.BR + .
-The index of the next
-.I arg
-is stored in
-.SM
-.BR OPTIND .
-The option argument,
-if any,
-gets stored in
-.SM
-.BR OPTARG .
-.P
-A leading
-.B :
-in
-.I optstring
-causes
-.B getopts
-to store the letter of an invalid
-option in
-.SM
-.BR OPTARG ,
-and to set
-.I vname
-to
-.B ?
-for an unknown option and to
-.B :
-when a required option is missing.
-Otherwise,
-.B getopts
-prints an error message.
-The exit status is non-zero when there are no more options.
-.P
-There is no way to specify any of the options
-.BR : ,
-.BR + ,
-.BR \- ,
-.BR ? ,
-.BR [ ,
-and
-.BR ] .
-The option
-.B #
-can only be specified as the first option.
-.TP
-.PD 0
-\f3hist\fP \*(OK \f3\-e\fP \f2ename\^\fP \ \*(CK \*(OK \f3\-nlr\^\fP \*(CK \*(OK \f2first\^\fP \*(OK \f2last\^\fP \*(CK \*(CK
-.TP
-\f3hist \-s \fP \*(OK \f2old\fP\f3\=\fP\f2new\^\fP \*(CK \*(OK \f2command\^\fP \*(CK
-.PD
-In the first form,
-a range of commands from
-.I first\^
-to
-.I last\^
-is selected from the last
-.SM
-.B HISTSIZE
-commands that were typed at the terminal.
-The arguments
-.I first\^
-and
-.I last\^
-may be specified as a number or as a string.
-A string is used to locate the most recent command starting with
-the given string.
-A negative number is used as an offset to the current command number.
-If the
-.B \-l
-option
-is selected,
-the commands are listed on standard output.
-Otherwise, the editor program
-.I ename\^
-is invoked on a file containing these
-keyboard commands.
-If
-.I ename\^
-is not supplied, then the value of the variable
-.SM
-.B HISTEDIT
-is used.
-If
-.SM
-.B HISTEDIT
-is not set then
-.SM
-.B FCEDIT
-(default
-.BR /bin/ed\^ )
-is used as the editor.
-When editing is complete, the edited command(s)
-is executed if the changes have been saved.
-If
-.I last\^
-is not specified
-then it will be set to
-.IR first .
-If
-.I first\^
-is not specified
-the default is the previous command
-for editing and \-16 for listing.
-The option
-.B \-r
-reverses the order of the commands and
-the option
-.B \-n
-suppresses command numbers when listing.
-In the second form the
-.I command\^
-is re-executed after the substitution
-\f2old\^\fP\f3=\fP\f2new\^\fP
-is performed.
-.TP
-\f3jobs\fP \*(OK \f3\-lnp\^\fP \*(CK \*(OK \f2job\^\fP \.\|.\|. \*(CK
-Lists information about each given job; or all active jobs if
-.I job
-is omitted.
-The
-.B \-l
-option lists process ids in addition to the normal information.
-The
-.B \-n
-option only displays jobs that have stopped or exited since last
-notified.
-The
-.B \-p
-option causes only the process group to be listed.
-See
-.I Jobs
-for a description of the format of
-.IR job .
-.TP
-.PD 0
-\f3kill\fP \*(OK \f3\-s\fP \f2signame\^\fP \*(CK \f2job\^\fP .\|.\|.
-.TP
-.PD 0
-\f3kill\fP \*(OK \f3\-n\fP \f2signum\^\fP \*(CK \f2job\^\fP .\|.\|.
-.TP
-\f3kill\fP \f3\-l\fP \*(OK \f2sig\^\fP .\|.\|. \*(CK
-.PD
-Sends either the TERM (terminate) signal or the
-specified signal to the specified jobs or processes.
-Signals are either given by number with the
-.B \-n
-option or by name with the
-.B \-s
-option
-(as given in
-.BR <signal.h> ,
-stripped of the prefix ``SIG'' with
-the exception that SIGCLD is named CHLD).
-For backward compatibility, the
-.B n
-and
-.B s
-can be omitted and the number or name placed immediately
-after the
-.BR \- .
-If the signal being sent is TERM (terminate) or HUP (hangup),
-then the job or process will be sent a CONT (continue) signal
-if it is stopped.
-The argument
-.I job\^
-can be the process id of a process that is not a member of one of the
-active jobs.
-See
-.I Jobs
-for a description of the format of
-.IR job .
-In the third form,
-.BR "kill \-l" ,
-if
-.I sig\^
-is not specified,
-the signal names are listed.
-Otherwise, for each
-.I sig\^
-that is a name, the corresponding signal number is listed.
-For each
-.I sig\^
-that is a number, the signal name corresponding to the
-least significant 8 bits of
-.I sig\^
-is listed.
-.TP
-\f3let\fP \f2arg\^\fP .\|.\|.
-Each
-.I arg
-is a separate
-.I "arithmetic expression"
-to be evaluated.
-See
-.I "Arithmetic Evaluation"
-above, for a description of arithmetic expression evaluation.
-.P
-The exit status is
-0 if the value of the last expression
-is non-zero, and 1 otherwise.
-.TP
-\(dg \f3newgrp\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-Equivalent to
-.BI "exec /bin/newgrp" " arg\^"
-\&.\|.\|.\^.
-.TP
-\f3print\fP \*(OK \f3\-Rnprs\^\fP \*(CK \*(OK \f3\-u\fP \f2unit\^\fP\*(CK \*(OK \f3\-f\fP \f2format\^\fP \*(CK \*(OK \f2arg\^\fP .\|.\|. \*(CK
-With no options or with option
-.B \-
-or
-.BR \-\|\- ,
-Each
-.I arg
-is printed
-on standard output.
-The
-.B \-f
-option causes the arguments to be printed as
-described by
-.BR printf .
-In this case any
-.BR n ,
-.BR r ,
-.B R
-options are ignored.
-Otherwise,
-unless the
-.B \-R
-or
-.BR \-r ,
-are specified, the following
-escape conventions will be applied:
-.RS
-.PD 0
-.TP
-.B \ea
-The alert character (ascii
-.BR 07 ).
-.TP
-.B \eb
-The backspace character (ascii
-.BR 010 ).
-.TP
-.B \ec
-Causes
-.B print
-to end without processing more arguments and
-not adding a new-line.
-.TP
-.B \ef
-The formfeed character (ascii
-.BR 014 ).
-.TP
-.B \en
-The new-line character (ascii
-.BR 012 ).
-.TP
-.B \er
-The carriage return character (ascii
-.BR 015 ).
-.TP
-.B \et
-The tab character (ascii
-.BR 011 ).
-.TP
-.B \ev
-The vertical tab character (ascii
-.BR 013 ).
-.TP
-.B \eE
-The escape character (ascii
-.BR 033 ).
-.TP
-.B \e\e
-The backslash character \e.
-.PD
-.PP
-The
-.B \-R
-option will print all subsequent arguments and options
-other than
-.BR \-n .
-The
-.B \-p
-option causes the
-arguments to be written onto the pipe
-of the process spawned with
-.B \(bv&
-instead of standard output.
-The
-.B \-s
-option causes the
-arguments to be written onto the history file
-instead of standard output.
-The
-.B \-u
-option can be used to specify a one digit
-file descriptor unit number
-.I unit\^
-on which the
-output will be placed.
-The default is 1.
-If the option
-.B \-n
-is used, no
-.B new-line\^
-is added to the output.
-.RE
-.TP
-\f3printf\fP \f2format\^\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK
-The arguments
-.I arg\^
-are printed on standard output
-in accordance with the ANSI-C
-formatting rules associated with the format string
-.IR format .
-The following extensions can also be used:
-.BL
-.LI
-A
-.B %b
-format can be used instead of
-.B %s
-to cause escape sequences in the corresponding
-.I arg\^
-to be expanded as described in
-.BR print.
-.LI
-A
-.B %P
-format can be used instead of
-.B %s
-to cause
-.I arg\^
-to be interpreted as an extended regular
-expression and be printed as a shell pattern.
-.LI
-A
-.B %q
-format can be used instead of
-.B %s
-to cause the resulting string to be quoted in a manner than can
-be reinput to the shell.
-.LI
-The precision field of the
-.B %d
-format can be followed by a
-.B .
-and the output base.
-.LE
-.TP
-\f3pwd\fP \*(OK \f3\-LP\fP \*(CK
-Outputs the value of the current working
-directory.
-If the
-.B \-P
-option is given,
-all symbolic links are resolved from the name.
-.TP
-\f3read\fP \*(OK \f3\-Aprs\^\fP \*(CK \*(OK \f3\-d\fP \f2delim\^\fP\*(CK \*(OK \f3\-t\fP \f2timeout\^\fP\*(CK \*(OK \f3\-u\fP \f2unit\^\fP\*(CK \*(OK \f2vname\f3?\f2prompt\^\f1 \*(CK \*(OK \f2vname\^\fP .\|.\|. \*(CK
-The shell input mechanism.
-One line is read and
-is broken up into fields using the characters in
-.B
-.SM IFS
-as separators.
-The escape character,
-.BR \e ,
-is used to remove any special meaning for the next
-character and for line continuation.
-The
-.B \-d
-option
-causes the read to continue to the first character of
-.I delim\^
-rather than new-line.
-In raw mode,
-.B \-r,
-the
-.B \e
-character is not treated specially.
-The first
-field is assigned to the first
-.IR vname ,
-the second field
-to the second
-.IR vname ,
-etc., with leftover fields assigned to the last
-.IR vname .
-The
-.B \-A
-option causes the variable
-.I vname\^
-to be unset and each field that is read to be stored in
-successive elements of the indexed array
-.IR vname.
-The
-.B \-p
-option causes the input line
-to be taken from the input pipe
-of a process spawned by the shell
-using
-.BR \(bv& .
-If the
-.B \-s
-option is present,
-the input will be saved as a command in the history file.
-The option
-.B \-u
-can be used to specify a one digit file
-descriptor unit
-.I unit\^
-to read from.
-The file descriptor can be opened with the
-.B exec\^
-special built-in command.
-The default value of unit
-.I n\^
-is 0.
-The option
-.B \-t
-is used to specify a timeout in decimal
-seconds when reading from a terminal or pipe.
-If
-.I vname\^
-is omitted then
-.SM
-.B REPLY
-is used as the default
-.IR vname .
-An end-of-file with the
-.B \-p
-option causes cleanup for this process
-so that another can be spawned.
-If the first argument contains a
-.BR ? ,
-the remainder of this word is used as a
-.I prompt\^
-on standard error
-when the shell is interactive.
-The exit status is 0 unless an end-of-file is encountered
-or read has timed out.
-.TP
-\(dg\(dg \f3readonly\fP \*(OK \f3\-p\fP \*(CK \*(OK \f2vname\fP\*(OK\f3=\fP\f2value\^\fP\*(CK \*(CK .\|.\|.
-If
-.I vname\^
-is not given
-the names and values of each variable with
-the readonly attribute is printed with the values
-quoted in a manner that allows them to be re-inputed.
-The
-.B \-p
-option
-causes the word
-.B readonly
-to be inserted before each one.
-Otherwise, the given
-.IR vname s
-are marked
-readonly and these
-names cannot be changed
-by subsequent assignment.
-.TP
-\(dg \f3return\fP \*(OK \f2n\^\fP \*(CK
-Causes a shell
-.I function
-or
-\f3\|.\fP
-script to return
-to the invoking script
-with the return status specified by
-.IR n .
-The value will be the least significant 8 bits of the specified status.
-If
-.I n\^
-is omitted then the return status is that of the last command executed.
-If
-.B return
-is invoked while not in a
-.I function
-or a
-\f3\|.\fP
-script,
-then it behaves the same as
-.BR exit .
-.TP
-\(dg \f3set\fP \*(OK \f3\(+-CPabefhkmnopstuvx\fP \*(CK \*(OK \f3\(+-o\fP \f2option\^\fP \*(CK.\|.\|. \*(OK \f3\(+-A\fP \f2vname\^\fP \*(CK \*(OK \f2arg\^\fP .\|.\|. \*(CK
-The options for this command have meaning as follows:
-.RS
-.PD 0
-.TP 8
-.B \-A
-Array assignment.
-Unset the variable
-.I vname
-and assign values sequentially from the
-list
-.IR arg .
-If
-.B +A
-is used, the variable
-.I vname
-is not unset first.
-.TP 8
-.B \-C
-Prevents redirection
-.B >
-from truncating existing files.
-Files that are created are opened with the O_EXCL mode.
-Require
-.B >\(bv
-to truncate a file when turned on.
-.TP 8
-.B \-P
-Causes the
-.B cd
-and
-.B pwd
-built-in commands to default to physical mode.
-.TP 8
-.B \-a
-All subsequent variables that are defined are automatically exported.
-.TP 8
-.B \-b
-Prints job completion messages as soon as a background job changes
-state rather than waiting for the next prompt.
-.TP 8
-.B \-e
-If a command has a non-zero exit status,
-execute the
-.SM
-.B ERR
-trap, if set,
-and exit.
-This mode is disabled while reading profiles.
-.TP 8
-.B \-f
-Disables file name generation.
-.TP 8
-.B \-h
-Each command
-becomes a tracked alias when first encountered.
-.TP 8
-.B \-k
-(Obsolete). All variable assignment arguments are placed in the environment for a command,
-not just those that precede the command name.
-.TP 8
-.B \-m
-Background jobs will run in a separate process group
-and a line will print upon completion.
-The exit status of background jobs is reported in a completion message.
-On systems with job control,
-this option is turned on automatically for
-interactive shells.
-.TP 8
-.B \-n
-Read commands and check them for syntax errors, but do not execute them.
-Ignored for interactive shells.
-.TP 8
-.B \-o
-The following argument can be one of the following option names:
-.RS
-.TP 8
-.B allexport
-Same as
-.BR \-a .
-.TP 8
-.B errexit
-Same as
-.BR \-e .
-.TP 8
-.B bgnice
-All background jobs are run at a lower priority.
-This is the default mode.
-.TP 8
-.B emacs
-Puts you in an
-.I emacs
-style in-line editor for command entry.
-.TP 8
-.B gmacs
-Puts you in a
-.I gmacs
-style in-line editor for command entry.
-.TP 8
-.B ignoreeof
-The shell will not exit on end-of-file.
-The command
-.B exit
-must be used.
-.TP 8
-.B keyword
-Same as
-.BR \-k .
-.TP 8
-.B markdirs
-All directory names resulting from file name generation have a trailing
-.B /
-appended.
-.TP 8
-.B monitor
-Same as
-.BR \-m .
-.TP 8
-.B noclobber
-Same as
-.BR \-C .
-.TP 8
-.B noexec
-Same as
-.BR \-n .
-.TP 8
-.B noglob
-Same as
-.BR \-f .
-.TP 8
-.B nolog
-Do not save function definitions in history file.
-.TP 8
-.B notify
-Same as
-.BR \-b .
-.TP 8
-.B nounset
-Same as
-.BR \-u .
-.TP 8
-.B physical
-Same as
-.BR \-P .
-.TP 8
-.B privileged
-Same as
-.BR \-p .
-.TP 8
-.B verbose
-Same as
-.BR \-v .
-.TP 8
-.B trackall
-Same as
-.BR \-h .
-.TP 8
-.B vi
-Puts you in insert mode of a
-.I vi\^
-style in-line editor
-until you hit escape character
-.BR 033 .
-This puts you in control mode.
-A return sends the line.
-.TP 8
-.B viraw
-Each character is processed as it is typed
-in
-.I vi\^
-mode.
-.TP 8
-.B xtrace
-Same as
-.BR \-x .
-.TP 8
-If no option name is supplied then the current option settings are printed.
-.RE
-.TP 8
-.B \-p
-Disables processing of the
-.B \s-1$HOME\s+1/.profile
-file and uses the file
-.B /etc/suid_profile
-instead of the
-.SM
-.B ENV
-file.
-This mode is on whenever the effective uid (gid)
-is not equal to the real uid (gid).
-Turning this off causes the effective uid and gid to be
-set to the real uid and gid.
-.TP 8
-.B \-s
-Sort the positional parameters lexicographically.
-.TP 8
-.B \-t
-(Obsolete). Exit after reading and executing one command.
-.TP 8
-.B \-u
-Treat unset parameters as an error when substituting.
-.TP 8
-.B \-v
-Print shell input lines as they are read.
-.TP 8
-.B \-x
-Print commands and their arguments as they are executed.
-.TP 8
-.B \-\|\-
-Do not change any of the options; useful in setting
-.B $1
-to a value beginning with
-.BR \- .
-If no arguments follow this option then the positional parameters are unset.
-.PD
-.PP
-As an obsolete feature,
-if the first
-.I arg\^
-is
-.B \-
-then the
-.B \-x
-and
-.B \-v
-options are turned off and the next
-.I arg
-is treated as the first argument.
-Using
-.B \+
-rather than
-.B \-
-causes these options to be turned off.
-These options can also be used upon invocation of the shell.
-The current set of options may be found in
-.BR $\- .
-Unless
-.B \-A
-is specified,
-the remaining arguments are positional
-parameters and are assigned, in order, to
-.B $1
-.B $2
-\&.\|.\|.\^.
-If no arguments are given then the names and values
-of all variables are printed on the standard output.
-.RE
-.TP
-\(dg \f3shift\fP \*(OK \f2n\^\fP \*(CK
-.br
-The positional parameters from
-\f3$\fP\f2n\fP\f3+1\fP
-\&.\|.\|.
-are renamed
-.B $1
-\&.\|.\|.\^
-, default
-.I n\^
-is 1.
-The parameter
-.I n\^
-can be any arithmetic expression that evaluates to a non-negative
-number less than or equal to
-.BR $# .
-.TP
-\f3sleep\fP \f2seconds\^\fP
-Suspends execution for the number of decimal seconds or fractions of a
-second given by
-.IR seconds .
-.TP
-\(dg \f3trap\fP \*(OK \f3\-p\fP \*(CK \*(OK \f2action\^\fP \*(CK \*(OK \f2sig\^\fP \*(CK .\|.\|.
-The \-p
-option causes the trap
-action associated with each trap as specified by the arguments
-to be printed with appropriate quoting.
-Otherwise,
-.I action\^
-will be processed as if it were an argument to
-.B eval
-when the shell
-receives signal(s)
-.IR sig .
-Each
-.I sig\^
-can be given as a number or as the name of the signal.
-Trap commands are executed in order of signal number.
-Any attempt to set a trap on a signal that
-was ignored on entry to the current shell
-is ineffective.
-If
-.I action\^
-is omitted and the first
-.I sig\^
-is a number, or if
-.I action\^
-is
-.BR \- ,
-then the trap(s) for each
-.I sig\^
-are reset
-to their original values.
-If
-.I action\^
-is the null
-string then this signal is ignored by the shell and by the commands
-it invokes.
-If
-.I sig\^
-is
-.SM
-.B ERR
-then
-.I action\^
-will be executed whenever a command has a non-zero exit status.
-If
-.I sig\^
-is
-.SM
-.B DEBUG
-then
-.I action\^
-will be executed before each command.
-If
-.I sig\^
-is
-.B 0
-or
-.SM
-.B EXIT
-and the
-.B trap
-statement is executed inside the body of a function,
-then the command
-.I action\^
-is executed
-after the function completes.
-If
-.I sig\^
-is
-.B 0
-or
-.SM
-.B EXIT
-for a
-.B trap
-set outside any function
-then the command
-.I action\^
-is executed
-on exit from the shell.
-If
-.I sig\^
-is
-.SM
-.B KEYBD
-then
-.I action\^
-will be executed whenever a key is read
-while in
-.BR emacs ,
-.BR gmacs ,
-or
-.B vi\^
-mode.
-The
-.B trap
-command
-with no arguments prints a list
-of commands associated with each signal number.
-.TP
-\(dg\(dg \f3typeset\fP \*(OK \f3\(+-AHflnprtux\^\fP \*(CK \*(OK \f3\(+-EFLRZi\*(OK\f2n\^\fP\*(CK \*(CK \*(OK \f2vname\^\fP\*(OK\f3=\fP\f2value\^\fP \*(CK \^ \*(CK .\|.\|.
-Sets attributes and values for shell variables and functions.
-When invoked inside a function,
-a new instance of the variables
-.I vname\^
-is created.
-The variables' value and type are restored
-when the function completes.
-The following list of attributes may be specified:
-.RS
-.PD 0
-.TP
-.B \-A
-Declares
-.I vname\^
-to be an associate array.
-Subscripts are strings rather than arithmetic
-expressions.
-.TP
-.B \-E
-Declares
-.I vname\^
-to be a double precision floating point number.
-If
-.I n\^
-is non-zero it defines the number of significant figures
-that are used when expanding
-.IR vname .
-Otherwise ten significant figures will be used.
-.TP
-.B \-F
-Declares
-.I vname\^
-to be a double precision floating point number.
-If
-.I n\^
-is non-zero it defines the number of places after the
-decimal point that are used when expanding
-.IR vname .
-Otherwise ten places after the decimal point will be used.
-.TP
-.B \-H
-This option provides UNIX to host-name file mapping on non-UNIX
-machines.
-.TP
-.B \-L
-Left justify and remove leading blanks from
-.IR value .
-If
-.I n\^
-is non-zero it defines the width
-of the field,
-otherwise it is determined by the width of the value of
-first assignment.
-When the variable is assigned to, it is
-filled on the right with blanks or truncated, if necessary, to
-fit into the field.
-The
-.B \-R
-option is turned off.
-.TP
-.B \-R
-Right justify and fill with leading blanks.
-If
-.I n\^
-is non-zero it defines the width
-of the field,
-otherwise it is determined by the width of the value of
-first assignment.
-The field is left filled with blanks or
-truncated from the end if the
-variable is reassigned.
-The
-.B \-L
-option is turned off.
-.TP
-.B \-Z
-Right justify and fill with leading zeros if
-the first non-blank character is a digit and the
-.B \-L
-option has not been set.
-Remove leading zeros if the
-.B \-L
-option is also set.
-If
-.I n\^
-is non-zero it defines the width
-of the field,
-otherwise it is determined by the width of the value of
-first assignment.
-.TP
-.B \-f
-The names refer to function names rather than
-variable names.
-No assignments can be made and the only other
-valid options are
-.BR \-t ,
-.B \-u
-and
-.BR \-x .
-The option
-.B \-t
-turns on execution tracing for this function.
-The option
-.B \-u
-causes this function to be marked undefined.
-The
-.SM
-.B FPATH
-variable will be searched to find the function definition
-when the function is referenced.
-.TP
-.B \-i
-Declares
-.I vname\^
-to be represented internally as integer.
-The right hand side of an assignment is evaluated as an
-arithmetic expression when assigning to an integer.
-If
-.I n\^
-is non-zero it defines the output arithmetic base,
-otherwise the the output base will be ten.
-.TP
-.B \-l
-All upper-case characters are
-converted to lower-case.
-The upper-case option,
-.B \-u
-is turned off.
-.TP
-.B \-n
-Declares
-.I vname\^
-to be a reference to the variable whose name is
-defined by the value of variable
-.IR vname .
-This is usually used to reference a variable inside
-a function whose name has been passed as an argument.
-.TP
-.B \-r
-The given
-.IR vname s
-are marked
-readonly and these
-names cannot be changed
-by subsequent assignment.
-.TP
-.B \-t
-Tags the variables.
-Tags are user definable and have no special
-meaning to the shell.
-.TP
-.B \-u
-All lower-case characters are converted
-to upper-case characters.
-The lower-case option,
-.BR \-l ,
-is turned off.
-.TP
-.B \-x
-The given
-.IR vname s
-are marked for automatic
-export to the
-.I environment\^
-of subsequently-executed commands.
-Variables whose names contain a \fB\s+2.\s-2\fP
-can not be exported.
-.PD
-.PP
-The
-.B \-i
-attribute can not be specified along with
-.BR \-R ,
-.BR \-L ,
-.BR \-Z ,
-or
-.BR \-f .
-.PP
-Using
-.B \+
-rather than
-.B \-
-causes these options to be turned off.
-If no
-.I vname\^
-arguments are given
-a list of
-.I vnames\^
-(and optionally the
-.IR values\^ )
-of the
-.I variables\^
-is printed.
-(Using
-.B \+
-rather than
-.B \-
-keeps the
-values from being printed.)
-The
-.B \-p
-option causes
-.B typeset
-followed by the the option letters
-to be printed before each name
-rather than the names of the options.
-If any option other than
-.B \-p
-is given,
-only those variables
-which have all of the given
-options are printed.
-Otherwise, the
-.IR vname s
-and
-.I attributes\^
-of all
-.I variables\^
-are printed.
-.RE
-.TP
-\f3ulimit\fP \*(OK \f3\-HSacdfmnpstv\fP \*(CK \*(OK \f2limit\^\fP \*(CK
-Set or display a resource limit.
-The available resources limits are listed below.
-Many systems do not contain one or more of these limits.
-The limit for a specified resource is set when
-.I limit\^
-is specified.
-The value of
-.I limit\^
-can be a number in the unit specified below with each resource,
-or the value
-.BR unlimited .
-The
-.B \-H
-and
-.B \-S
-options specify whether the hard limit or the
-soft limit for the given resource is set.
-A hard limit cannot be increased once it is set. A soft
-limit can be increased up to the value of the hard limit.
-If neither the
-.B H
-or
-.B S
-options is specified, the limit applies to both.
-The current resource limit is printed when
-.I limit\^
-is omitted.
-In this case the soft limit is printed unless
-.B H
-is specified.
-When more that one resource is specified, then the limit
-name and unit is printed before the value.
-.RS
-.PD 0
-.TP
-.B \-a
-Lists all of the current resource limits.
-.TP
-.B \-c
-The number of 512-byte blocks on the size of core dumps.
-.TP
-.B \-d
-The number of K-bytes on the size of the data area.
-.TP
-.B \-f
-The number of 512-byte blocks on files that can be written the
-current process or by child processes (files of any size may be read).
-.TP
-.B \-m
-The number of K-bytes on the size of physical memory.
-.TP
-.B \-n
-The number of file descriptors plus 1.
-.TP
-.B \-p
-The number of 512-byte blocks for pipe buffering.
-.TP
-.B \-s
-The number of K-bytes on the size of the stack area.
-.TP
-.B \-t
-The number of seconds to be used by each process.
-.TP
-.B \-v
-The number of K-bytes for virtual memory.
-.PD
-.PP
-If no option is given,
-.B \-f
-is assumed.
-.RE
-.TP
-\f3umask\fP \*(OK \f3\-S\fP \*(CK \*(OK \f2mask\^\fP \*(CK
-The user file-creation mask is set to
-.I mask\^
-(see
-.IR umask (2)).
-.I mask
-can either be an octal number or
-a symbolic value as described in
-.IR chmod (1).
-If a symbolic value is given,
-the new
-umask value is the complement of the result of
-applying
-.I mask\^
-to the complement of the previous umask value.
-If
-.I mask\^
-is omitted, the current value of the mask is printed.
-The
-.B \-S
-option causes the mode to be printed as a symbolic
-value. Otherwise, the
-mask is printed in octal.
-.TP
-\(dg \f3unalias\fP \*(OK \f3\-a\fP \*(CK \f2name\^\fP .\|.\|.
-The
-.I aliases\^
-given by the list of
-.IR name s
-are removed from the
-.I alias\^
-list.
-The
-.B \-a
-option causes all the
-aliases to be unset.
-.TP
-\(dg\f3unset\fP \*(OK \f3\-fv\fP \*(CK \f2vname\^\fP .\|.\|.
-The variables given by the list of
-.IR vname s
-are unassigned,
-i.e.,
-their values and attributes are erased.
-Readonly variables cannot be unset.
-If the
-.B \-f
-option
-is set, then the names refer to
-.I function\^
-names.
-If the
-.B \-v
-option is set, then the names refer to
-.I variable\^
-names.
-The default is equivalent to
-.BR \-v .
-Unsetting
-.SM
-.BR ERRNO ,
-.SM
-.BR LINENO ,
-.SM
-.BR MAILCHECK ,
-.SM
-.BR OPTARG ,
-.SM
-.BR OPTIND ,
-.SM
-.BR RANDOM ,
-.SM
-.BR SECONDS ,
-.SM
-.BR TMOUT ,
-and
-.SM
-.B _
-removes their special meaning even if they are
-subsequently assigned to.
-.TP
-\f3wait\fP \*(OK \f2job\^\fP .\|.\|. \*(CK
-Wait for the specified
-.I job
-and
-report its termination status.
-If
-.I job\^
-is not given then all currently active child processes are waited for.
-The exit status from this command is that of
-the last process waited for.
-See
-.I Jobs
-for a description of the format of
-.IR job .
-.TP
-\f3whence\fP \*(OK \f3\-apv\fP \*(CK \f2name\^\fP .\|.\|.
-For each
-.IR name ,
-indicate how it
-would be interpreted if used as a command name.
-.P
-The
-.B \-v
-option
-produces a more verbose report.
-.P
-The
-.B \-p
-option
-does a path search for
-.I name\^
-even if name is an alias, a function, or a reserved word.
-The
-.B \-a
-is similar to the
-.B \-v
-option but causes
-all interpretations of the given name to be reported.
-.SS Invocation.
-If the shell is invoked by
-.IR exec (2),
-and the first character of argument zero
-.RB ( $0 )
-is
-.BR \- ,
-then the shell is assumed to be a
-.I login
-shell and
-commands are read from
-.B /etc/profile
-and then from either
-.B .profile
-in the current directory or
-.BR \s-1$HOME\s+1/.profile ,
-if either file exists.
-Next, commands are read from
-the file named by
-performing parameter expansion, command substitution,
-and arithmetic substitution on
-the value of the environment variable
-.SM
-.B ENV
-if the file exists.
-If the
-.B \-s
-option is not present and
-.I arg\^
-is, then a path search is performed on the first
-.I arg\^
-to determine the name of the script to execute.
-The script
-.I arg\^
-must have read permission and any
-.I setuid
-and
-.I getgid
-settings will be ignored.
-If the script is not found on the path,
-.I arg\^
-is processed as if it named a built-in command or function.
-Commands are then read as described below;
-the following option are interpreted by the shell
-when it is invoked:
-.PP
-.PD 0
-.TP 10
-.BI \-c
-If the
-.B \-c
-option is present then
-commands are read from the first
-.IR arg .
-Any remaining arguments become
-position parameters starting at
-.B 0 .
-.TP
-.B \-s
-If the
-.B \-s
-option is present or if no
-arguments remain
-then commands are read from the standard input.
-Shell output,
-except for the output of the
-.I Special Commands\^
-listed above,
-is written to
-file descriptor 2.
-.TP
-.B \-i
-If the
-.B \-i
-option is present or
-if the shell input and output are attached to a terminal (as told by
-.IR ioctl (2))
-then this shell is
-.IR interactive .
-In this case \s-1TERM\s+1 is ignored (so that \f3kill 0\fP
-does not kill an interactive shell) and \s-1INTR\s+1 is caught and ignored
-(so that
-.B wait
-is interruptible).
-In all cases, \s-1QUIT\s+1 is ignored by the shell.
-.TP
-.B \-r
-If the
-.B \-r
-option is present the shell is a restricted shell.
-.PD
-.PP
-The
-.B \-I
-.I filename\^
-option is used
-to generate a cross reference database
-that can be used by a separate utility
-to find definitions and references for variables and commands.
-.PP
-The remaining options and arguments are described under the
-.B set
-command above.
-An optional
-.B \-
-as the first argument is ignored.
-.if \nZ=0 \{.SS Rsh Only.
-.I Rsh\}
-.if \nZ=1 \{.SS Rksh Only.
-.I Rksh\}
-is used to set up login names and execution environments whose
-capabilities are more controlled than those of the standard shell.
-The actions of
-.if \nZ=0 .B rsh\^
-.if \nZ=1 .B rksh\^
-are identical to those of
-.if \nZ=0 .BR sh\^ ,
-.if \nZ=1 .BR ksh\^ ,
-except that the following are disallowed:
-.RS
-.PD 0
-.PP
-changing directory (see
-.IR cd (1)),
-.br
-setting or unsetting the value or attributes of
-.SM
-.BR SHELL ,
-.SM
-.BR ENV ,
-or
-.SM
-.BR PATH\*S,
-.br
-specifying path or
-command names containing
-.BR / ,
-.br
-redirecting output
-.RB ( > ,
-.BR >| ,
-.BR <> ,
-and
-.BR >> ).
-.PD
-.RE
-.PP
-The restrictions above are enforced
-after \f3.profile\fP and the
-.SM
-.B ENV
-files are interpreted.
-.PP
-When a command to be executed is found to be a shell procedure,
-.if \nZ=0 \{.B rsh\^
-invokes
-.I sh\^\}
-.if \nZ=1 \{.B rksh\^
-invokes
-.I ksh\^\}
-to execute it.
-Thus, it is possible to provide to the end-user shell procedures
-that have access to the full power of
-the standard shell,
-while imposing a limited menu of commands;
-this scheme assumes that the end-user does not have write and
-execute permissions in the same directory.
-.PP
-The net effect of these rules is that the writer of the
-.B .profile
-has complete control over user actions,
-by performing guaranteed setup actions
-and leaving the user in an appropriate directory
-(probably
-.I not\^
-the login directory).
-.PP
-The system administrator often sets up a directory
-of commands
-(i.e.,
-.BR /usr/rbin )
-that can be safely invoked by
-.if \nZ=0 .BR rsh .
-.if \nZ=1 .BR rksh .
-.SH EXIT STATUS
-Errors detected by the shell, such as syntax errors,
-cause the shell
-to return a non-zero exit status.
-Otherwise, the shell returns the exit status of
-the last command executed (see also the
-.B exit
-command above).
-If the shell is being used non-interactively
-then execution of the shell file is abandoned.
-Run time errors detected by the shell are reported by
-printing the command or function name and the error condition.
-If the line number that the error occurred on is greater than one,
-then the line number is also printed in square brackets
-.RB ( "[]" )
-after the command or function name.
-.SH FILES
-/etc/passwd
-.br
-/etc/profile
-.br
-/etc/suid_profile
-.br
-\s-1$HOME\s+1/\f3.\fPprofile
-.br
-/tmp/sh\(**
-.br
-/dev/null
-.SH SEE ALSO
-cat(1),
-cd(1),
-chmod(1),
-cut(1),
-echo(1),
-emacs(1),
-env(1),
-gmacs(1),
-newgrp(1),
-stty(1),
-test(1),
-umask(1),
-vi(1),
-dup(2),
-exec(2),
-fork(2),
-ioctl(2),
-lseek(2),
-paste(1),
-pipe(2),
-umask(2),
-ulimit(2),
-wait(2),
-rand(3),
-a.out(5),
-profile(5),
-environ(7).
-.PP
-Morris I. Bolsky and David G. Korn,
-.IR "The KornShell Command and Programming Language" ,
-Prentice Hall, 1989, ISBN 0-13-516972-0.
-.SH CAVEATS
-.PP
-If a command
-is executed, and then a command with the same name is
-installed in a directory in the search path before the directory where the
-original command was found, the shell will continue to
-.I exec\^
-the original command.
-Use the
-.B \-t
-option of the
-.B alias\^
-command to correct this situation.
-.PP
-Some very old shell scripts contain a
-.B ^
-as a synonym for the pipe character
-.BR \(bv .
-.PP
-Using the
-.B hist\^
-built-in command within a compound command will cause the whole
-command to disappear from the history file.
-.PP
-The built-in command \f3\|.\fP \f2file\^\fP
-reads the whole file before any commands are executed.
-Therefore,
-.B alias
-and
-.B unalias
-commands in the file
-will not apply to any commands defined in the file.
-.PP
-Traps are not processed while a job is waiting for a foreground process.
-Thus, a trap on
-.B CHLD
-won't be executed until the foreground job terminates.
-
projects / oweals / cde.git / commitdiff