ksh93(1)

Name | Synopsis | Description | Usage | Exit Status | Files | Authors | Attributes | See Also | Notes

Name

ksh93, rksh93– Korn Shell, a standard and restricted command and programming language

Synopsis

ksh93 [±abcefhikmnoprstuvxBCD] [-R file] [ ±o option] ...
       [-] [arg ...]

rksh93 [±abcefhikmnoprstuvxBCD] [-R file] [±o option] ...
       [-] [arg ...]

Description

ksh93 is a command and programming language that executes commands read from a terminal or a file. rksh93 is a restricted version of the command interpreter ksh93. rksh93 is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell.

See Invocation for the meaning of arguments to the shell.

Definitions

A metacharacter is defined as one of the following characters:

; & ( ) | < > NEWLINE SPACE TAB

A blank is a TAB or a SPACE.

An identifier is a sequence of letters, digits, or underscores starting with a letter or underscore. Identifiers are used as components of variable names.

A vname is a sequence of one or more identifiers separated by a period (.) and optionally preceded by a period (.). vnames are used as function and variable names.

A word is a sequence of characters from the character set defined by the current locale, excluding non-quoted metacharacters.

A 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 in this manual page. Built-ins that cause side effects in the shell environment and built-ins that are found before performing a path search (see Execution) are documented in this manual page. For historical reasons, some of these built-ins behave differently than other built-ins and are called special built-ins.

Commands

A simple-command is a list of variable assignments (see Variable Assignments) or a sequence of blank-separated words which can be preceded by a list of variable assignments. See the Environment section of this manual page.

The first word specifies the name of the command to be executed. Except as specified in this section, the remaining words are passed as arguments to the invoked command. The command name is passed as argument 0. See exec(2). The value of a simple-command is its exit status. If it terminates normally, its value is 0-255. If it terminates abnormally, its value is 256+signum. The name of the signal corresponding to the exit status can be obtained by way of the -l option of the kill built-in utility.

A pipeline is a sequence of one or more commands separated by |. The standard output of each command but the last is connected by a 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 unless the pipefail option is enabled. Each pipeline can be preceded by the reserved word!. This causes the exit status of the pipeline to become 0 if the exit status of the last command is non-zero, and 1 if the exit status of the last command is 0.

A list is a sequence of one or more pipelines separated by ;, &, |&, &&, or |, and optionally terminated by ;, &, or |&. Of these five symbols, ;, &, and |& have equal precedence, which is lower than that of && and ||. The symbols && and || also have equal precedence.

A semicolon (;) causes sequential execution of the preceding pipeline. An ampersand (&) causes asynchronous execution of the preceding pipeline, that is, the shell does not wait for that pipeline to finish. The symbol |& 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 <& and >& with arg p to commands and by using -p option of the built-in commands read and print. The symbol && (||) causes the list following it to be executed only if the preceding pipeline returns a zero (non-zero) value. One or more NEWLINEs can appear in a list instead of a semicolon, to delimit a command. The first item of the first pipeline of a list that is a simple command not beginning with a redirection, and not occurring within a while, until, or if list , can be preceded by a semicolon. This semicolon is ignored unless the showme option is enabled as described with the set built-in.

A command is either a simple-command or one of commands in the following list. Unless otherwise stated, the value returned by a command is that of the last simple-command executed in the command.

for vname [ in word ... ] ;do list ;done

Each time a for command is executed, vname is set to the next word taken from the in word list. If in word ... is omitted, the for command executes the do list once for each positional parameter that is set starting from 1. Execution ends when there are no more words in the list. See Parameter Expansion.

(( [expr1] ; [expr2] ; [expr3] )) ;do list ;done

The arithmetic expression expr1 is evaluated first. The arithmetic expression expr2 is repeatedly evaluated until it evaluates to zero and when non-zero, list is executed and the arithmetic expression expr3 evaluated. If any expression is omitted, then it behaves as if it evaluated to 1. See Arithmetic Evaluation.

select vname [ in word ... ] ;do list ;done

A select command prints on standard error (file descriptor 2) the set of words, each preceded by a number. If in word... is omitted, the positional parameters starting from 1 are used instead. See Parameter Expansion. The 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 words, then the value of the variable vname is set to the word corresponding to this number. If this line is empty, the selection list is printed again. Otherwise the value of the variable vname is set to null. The contents of the line read from standard input is saved in the variable REPLY. The list is executed for each selection until a break or EOF is encountered. If the REPLY variable is set to null by the execution of list, the selection list is printed before displaying the PS3 prompt for the next selection.

case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac

A case command executes the list associated with the first pattern that matches word. The form of the patterns is the same as that used for file name generation. See File Name Generation.

The ;; operator causes execution of case to terminate. If ;& is used in place of ;; the next subsequent list, if any, is executed.

if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi

The list following if is executed and, if it returns a zero exit status, the list following the first then is executed. Otherwise, the list following elif is executed, and, if its value is zero, the list following the next then is executed. Failing each successive elif list, the else list is executed. If the if list has non-zero exit status and there is no else list, then the if command returns a zero exit status.

while list ;do list ;done
until list ;do list ;done

A while command repeatedly executes the while list and, if the exit status of the last command in the list is zero, executes the do list, otherwise the loop terminates. If no commands in the do list are executed, then the while command returns a zero exit status, until can be used in place of while to negate the loop termination test.

((expression))

The expression is evaluated using the rules for arithmetic evaluation described in this manual page. If the value of the arithmetic expression is non-zero, the exit status is 0. Otherwise the exit status is 1.

(list;)

Execute list in a separate environment. If two adjacent open parentheses are needed for nesting, a SPACE must be inserted to avoid evaluation as an arithmetic command as described in this section.

list is simply executed. Unlike the metacharacters, ( and ), { and } are reserved words and must occur at the beginning of a line or after a ; to be recognized.

[[ expression ]]

Evaluates expression and returns a zero exit status when expression is true. See Conditional Expressions for a description of expression.

function varname { list ;}
varname () { list ;}

Define a function which is referenced by varname. A function whose varname contains a . is called a discipline function and the portion of the varname preceding the last . must refer to an existing variable.

The body of the function is the list of commands between { and }. A function defined with the function varname syntax can also be used as an argument to the . special built-in command to get the equivalent behavior as if the varname() syntax were used to define it. See Functions.

time [ pipeline ]

If pipeline is omitted, the user and system time for the current shell and completed child processes is printed on standard error. Otherwise, pipeline is executed and the elapsed time as well as the user and system time are printed on standard error. The TIMEFORMAT variable can be set to a format string that specifies how the timing information should be displayed. See Shell Variables for a description of the TIMEFORMAT variable.

The following reserved words are recognized as reserved only when they are the first word of a command and are not quoted:

case

do

done

else

elif

esac

for

fi

function

if

select

then

time

until

while

{ }

[[ ]]

!

Variable Assignments

One or more variable assignments can start a simple command or can be arguments to the typeset, export, or readonly special built-in commands. The syntax for an assignment is of the form:

varname=word
varname[word]=word

No space is permitted between varname and the = or between = and word.

varname=(assignlist)

No space is permitted between varname and the =. An assignlist can be one of the following:

word ...

Indexed array assignment.

[word]=word ...

Associative array assignment. If prefixed by typeset -a, creates an indexed array instead.

assignment ...

Compound variable assignment. This creates a compound variable varname with sub-variables of the form varname.name, where name is the name portion of assignment. The value of varname contains all the assignment elements. Additional assignments made to sub-variables of varname are also displayed as part of the value of varname. If no assignments are specified, varname is a compound variable allowing subsequence child elements to be defined.

typeset [options] assignment ...

Nested variable assignment. Multiple assignments can be specified by separating each of them with a ;. The previous value is unset before the assignment.

In addition, a += can be used in place of the = to signify adding to or appending to the previous value. When += is applied to an arithmetic type, word is evaluated as an arithmetic expression and added to the current value. When applied to a string variable, the value defined by word is appended to the value. For compound assignments, the previous value is not unset and the new values are appended to the current ones provided that the types are compatible.

Comments

A word beginning with # causes that word and all the following characters up to a NEWLINE to be commented, or ignored.

Aliasing

The first word of each command is replaced by the text of an alias if an alias for this word has been defined. An alias name consists of any number of characters excluding metacharacters, quoting characters, file expansion characters, parameter expansion characters, command substitution characters, and =. The replacement string can contain any valid shell script including the metacharacters listed in the Commands section. The first word of each command in the replaced text, other than any that are in the process of being replaced, are tested for aliases. If the last character of the alias value is a BLANK then the word following the alias is also checked for alias substitution.

Aliases can be used to redefine built-in commands but cannot be used to redefine the reserved words listed in the Commands section. Aliases can be created and listed with the alias command and can be removed with the unalias command.

Aliasing is performed when scripts are read, not while they are executed. For an alias to take effect, the alias definition command has to be executed before the command which references the alias is read. The following aliases are compiled into the shell but can be unset or redefined:

autoload='typeset -fu' command='command ' fc=hist float='typeset -lE' functions='typeset -f' hash='alias -t --' history='hist -l' integer='typeset -li' nameref='typeset -n' nohup='nohup ' r='hist -s' redirect='command exec' source='command .' stop='kill -s STOP' suspend='kill -s STOP $$' times='{ { time;} 2>&1;}' type='whence -v'

Tilde Substitution

After alias substitution is performed, each word is checked to see if it begins with an unquoted tilde (~). For tilde substitution, word also refers to the word portion of parameter expansion. See Parameter Expansion.

If it does, the word up to a / is checked to see if it matches a user name in the password database. If a match is found, the ~ 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 ~ by itself, or in front of a /, is replaced by $HOME. A ~ followed by a + or - is replaced by the value of $PWD and $OLDPWD respectively.

In addition, when expanding a variable assignment, tilde substitution is attempted when the value of the assignment begins with a ~, and when a ~ appears after a colon (:). The : also terminates a ~ login name.

Command Substitution

The standard output from a command enclosed in parentheses preceded by a dollar sign ($) or a pair of grave accents (‘‘) can be used as part or all of a word. Trailing NEWLINEs are removed. In the second (obsolete) form, the string between the quotes is processed for special quoting characters before the command is executed. See Quoting.

The command substitution $(cat file) can be replaced by the equivalent but faster $(<file). The command substitution $(n<#) expands to the current byte offset for file descriptor n.

Arithmetic Substitution

An arithmetic expression enclosed in double parentheses preceded by a dollar sign ( $((arithmetic_expression))) is replaced by the value of the arithmetic expression within the double parentheses.

Process Substitution

Process substitution is only available on versions of the UNIX operating system that support the /dev/fd directory for naming open files.

Each command argument of the form <(list) or >(list) runs process list asynchronously connected to some file in /dev/fd. The name of this file becomes the argument to the command. If the form with > is selected then writing on this file provides input for list. If < is used, then the file passed as an argument contains the output of the list process.

For example,

paste <(cut -f1 file1) <(cut -f3 file2) | tee \ >(process1) >(process2)

cuts fields 1 and 3 from the files file1 and file2 respectively, pastes the results together, and sends it to the processes process1 and process2. It also displays the results to the standard output. The file, which is passed as an argument to the command, is a UNIX pipe(2). Programs that expect to lseek(2) on the file do not work.

Parameter Expansion

A parameter is a variable, one or more digits, or any of the characters *, @, #, ?, -, $, and !. A variable is denoted by a vname. To create a variable whose vname contains a ., a variable whose vname consists of everything before the last . must already exist. A variable has a value and zero or more attributes. Variables can be assigned values and attributes by using the typeset special built-in command. The attributes supported by the shell are described later with the typeset special built-in command. Exported variables pass values and attributes to the environment.

The shell supports both indexed and associative arrays. An element of an array variable is referenced by a subscript. A subscript for an indexed array is denoted by an arithmetic expression, (see Arithmetic Evaluation), between a [ and a ]. Use set -A vname value ... to assign values to an indexed array. The value of all subscripts must be in the range of 0 through 1,048,575. Indexed arrays do not need to be declared. Any reference to a variable with a valid subscript is legal and an array is created if necessary.

An associative array is created with the -A option to typeset. A subscript for an associative array is denoted by a string enclosed between [ and ].

Referencing any array without a subscript is equivalent to referencing the array with subscript 0.

The value of a variable can be assigned by:

vname=value [vname=value] ...

or

vname[subscript]=value [vname[subscript]=value] ...

No space is allowed before or after the =. A nameref is a variable that is a reference to another variable. A nameref is created with the -n attribute of typeset. The value of the variable at the time of the typeset command becomes the variable that is referenced whenever the nameref variable is used. The name of a nameref cannot contain a dot (.). When a variable or function name contains a ., and the portion of the name up to the first . 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. If a nameref is used as the index of a for loop, a name reference is established for each item in the list. 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

typeset -n var=$1

inside the function causes references and assignments to var to be references and assignments to the variable whose name has been passed to the function. If either of the floating point attributes, -E, or -F, or the integer attribute, -i, is set for vname, then the value is subject to arithmetic evaluation as described in this manual page. Positional parameters, parameters denoted by a number, can be assigned values with the set special built-in command. Parameter $0 is set from argument zero when the shell is invoked. The character $ is used to introduce substitutable parameters.

${parameter}

The shell reads all the characters from ${ to the matching } 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 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 ., or when a variable is subscripted. If 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 parameter is * or @, then all the positional parameters, starting with $1, are substituted and separated by a field separator character. If an array vname with subscript * or @ is used, then the value for each of the elements is substituted, separated by the first character of the value of IFS.

${#parameter}

If parameter is * or @, the number of positional parameters is substituted. Otherwise, the length of the value of the parameter is substituted.

${#vname[*]}
${#vname[@]}

The number of elements in the array vname is substituted.

${!vname}

Expands to the name of the variable referred to by vname. This is vname except when vname is a name reference.

${!vname[subscript]}

Expands to name of the subscript unless subscript is * or @. When subscript is *, the list of array subscripts for vname is generated. For a variable that is not an array, the value is 0 if the variable is set. Otherwise it is null. When subscript is @, it is the same as $ {vname[*]}, except that when used in double quotes, each array subscript yields a separate argument.

${!prefix*}

Expands to the names of the variables whose names begin with prefix.

${parameter:-word}

If parameter is set and is non-null then substitute its value. Otherwise substitute word.

word is not evaluated unless it is to be used as the substituted string.

In the following example, pwd is executed only if d is not set or is NULL:

print ${d:-$(pwd)}

If the colon (: ) is omitted from the expression, the shell only checks whether parameter is set or not.

${parameter:=word}

If parameter is not set or is null, set it to word. The value of the parameter is then substituted. Positional parameters cannot be assigned to in this way.

word is not evaluated unless it is to be used as the substituted string.

In the following example, pwd is executed only if d is not set or is NULL:

print ${d:-$(pwd)}

If the colon (:) is omitted from the expression, the shell only checks whether parameter is set or not.

${parameter:?word}

If parameter is set and is non-null, substitute its value. Otherwise, print word and exit from the shell , if the shell is not interactive. If word is omitted then a standard message is printed.

word is not evaluated unless it is to be used as the substituted string.

In the following example, pwd is executed only if d is not set or is NULL:

print ${d:-$(pwd)}

If the colon (: ) is omitted from the expression, the shell only checks whether parameter is set or not.

${parameter:+word}

If parameter is set and is non-null, substitute word. Otherwise substitute nothing.

word is not evaluated unless it is to be used as the substituted string.

In the following example, pwd is executed only if d is not set or is NULL:

print ${d:-$(pwd)}

If the colon (:) is omitted from the expression, the shell only checks whether parameter is set or not.

${parameter:offset:length}
${parameter:offset}

Expands to the portion of the value of parameter starting at the character (counting from 0) determined by expanding offset as an arithmetic expression and consisting of the number of characters determined by the arithmetic expression defined by length.

In the second form, the remainder of the value is used. A negative offset counts backwards from the end of parameter.

One or more BLANKs is required in front of a minus sign to prevent the shell from interpreting the operator as :-. If parameter is * or @, or is an array name indexed by * or @, then offset and length refer to the array index and number of elements respectively. A negative offset is taken relative to one greater than the highest subscript for indexed arrays. The order for associative arrays is unspecified.

${parameter#pattern}
${parameter##pattern}

If the shell pattern matches the beginning of the value of parameter, then the value of this expansion is the value of the parameter with the matched portion deleted. Otherwise the value of this 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 parameter is @, *, or an array variable with subscript @ or *, the substring operation is applied to each element in turn.

${parameter%pattern}
${parameter%%pattern}

If the shell pattern matches the end of the value of parameter, then the value of this expansion is the value of the parameter with the matched part deleted. Otherwise substitute the value of parameter. In the first form the smallest matching pattern is deleted, and in the second form the largest matching pattern is deleted. When parameter is @, *, or an array variable with subscript @ or *, the substring operation is applied to each element in turn.

${parameter/pattern/string}
${parameter//pattern/string}
${parameter/#pattern/string}
${parameter/%pattern/string}

Expands parameter and replaces the longest match of pattern with the specified string. Each occurrence of \n in string is replaced by the portion of parameter that matches the nth sub-pattern.

When string is null, the pattern is deleted and the / in front of string can be omitted. When parameter is @, *, or an array variable with subscript @ or *, the substitution operation is applied to each element in turn. In this case, the string portion of word is re-evaluated for each element.

In the first form, only the first occurrence of pattern is replaced.

In the second form, each match for pattern is replaced by the specified string.

The third form restricts the pattern match to the beginning of the string.

The fourth form restricts the pattern match to the end of the string.

The following parameters are automatically set by the shell:

#

The number of positional parameters in decimal.

-

Options supplied to the shell on invocation or by the set command.

?

The decimal value returned by the last executed command.

$

The process number of this shell.

_

Initially, the value of _ is the absolute pathname of the shell or script being executed as passed in the environment. It is subsequently 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 MAIL file when checking for mail.

!

The process number of the last background command invoked or the most recent job put in the background with the bg built-in command.

.sh.command

When processing a DEBUG trap, this variable contains the current command line that is about to run.

.sh.edchar

This variable contains the value of the keyboard character (or sequence of characters if the first character is an ESC, ASCII 033) that has been entered when processing a 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. See the Key Bindings section of this manual page.

.sh.edcol

The character position of the cursor at the time of the most recent KEYBD trap.

.sh.edmode

The value is set to ESC when processing a KEYBD trap while in vi insert mode. Otherwise, .sh.edmode is null when processing a KEYBD trap. See the vi Editing Mode section of this manual page.

.sh.edtext

The characters in the input buffer at the time of the most recent KEYBD trap. The value is null when not processing a KEYBD trap.

.sh.file

The pathname of the file than contains the current command.

.sh.fun

The name of the current function that is being executed.

.sh.match

An indexed array which stores the most recent match and sub-pattern matches after conditional pattern matches that match and after variables expansions using the operators #, %, or /. The 0th element stores the complete match and the ith element stores the ith sub-match. The .sh.match variable is unset when the variable that has expanded is assigned a new value.

.sh.name

Set to the name of the variable at the time that a discipline function is invoked.

.sh.subscript

Set to the name subscript of the variable at the time that a discipline function is invoked.

.sh.subshell

The current depth for sub-shells and command substitution.

.sh.value

Set to the value of the variable at the time that the set or append discipline function is invoked.

.sh.version

Set to a value that identifies the version of this shell.

LINENO

The current line number within the script or function being executed.

OLDPWD

The previous working directory set by the cd command.

OPTARG

The value of the last option argument processed by the getopts built-in command.

OPTIND

The index of the last option argument processed by the getopts built-in command.

PPID

The process number of the parent of the shell.

PWD

The present working directory set by the cd command.

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 RANDOM.

REPLY

This variable is set by the select statement and by the read built-in command when no arguments are supplied.

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 is the value that was assigned plus the number of seconds since the assignment.

The following variables are used by the shell:

CDPATH

Defines the search path for the cd command.

COLUMNS

Defines the width of the edit window for the shell edit modes and for printing select lists.

EDITOR

If the VISUAL variable is not set, the value of this variable is checked for the patterns as described with VISUAL and the corresponding editing option is turned on.

See the set command in the Special Command section of this manual page.

ENV

Performs parameter expansion, command substitution, and arithmetic substitution on the value to generate the pathname of the script that is executed when the shell is invoked. This file is typically used for alias and function definitions. The default value is $HOME/.kshrc.

See the Invocation section of this manual page.

ENV is not set by the shell.

FCEDIT

Obsolete name for the default editor name for the hist command. FCEDIT is not used when HISTEDIT is set.

The shell specifies a default value to FCEDIT.

FIGNORE

A pattern that defines the set of file names that is ignored when performing file name matching.

FPATH

The search path for function definitions. The directories in this path are searched for a file with the same name as the function or command when a function with the -u attribute is referenced and when a command is not found. If an executable file with the name of that command is found, then it is read and executed in the current environment. Unlike PATH, the current directory must be represented explicitly by dot (.) rather than by adjacent colon (:) characters or a beginning or ending colon (:).

HISTCMD

The number of the current command in the history file.

HISTEDIT

The name for the default editor name for the hist command.

HISTFILE

If this variable is set when the shell is invoked, the value is the pathname of the file that is used to store the command history. See the Command Re-entry section of this manual page.

HISTSIZE

If this variable is set when the shell is invoked, then the number of previously entered commands that are accessible by this shell is greater than or equal to this number. The default is 512.

HOME

The default argument (home directory) for the cd command.

HOME is not set by the shell. HOME is set by login(1).

IFS

Internal field separators, normally SPACE, TAB, and NEWLINE that are used to separate the results of command substitution or parameter expansion and to separate fields with the built-in command read. The first character of the IFS variable is used to separate arguments for the "$*" substitution. See the Quoting section of this manual page.

Each single occurrence of an IFS character in the string to be split, that is not in the issspace character class, and any adjacent characters in IFS that are in the issspace character class, delimit a field. One or more characters in IFS that belong to the issspace character class, delimit a field. In addition, if the same issspace character appears consecutively inside IFS, this character is treated as if it were not in the issspace class, so that if IFS consists of two tab characters, then two adjacent tab characters delimit a null field.

The shell specifies a default value to IFS.

LANG

This variable determines the locale category for any category not specifically selected with a variable starting with LC_ or LANG.

LC_ALL

This variable overrides the value of the LANG variable and any other LC_ variable.

LC_COLLATE

This variable determines the locale category for character collation information.

LC_CTYPE

This variable determines the locale category for character handling functions. It determines the character classes for pattern matching. See the File Name Generation section of this manual page.

LC_NUMERIC

This variable determines the locale category for the decimal point character.

LINES

If this variable is set, the value is used to determine the column length for printing select lists. Select lists prints vertically until about two-thirds of LINES lines are filled.

MAIL

If this variable is set to the name of a mail file and the MAILPATH variable is not set, then the shell informs the user of arrival of mail in the specified file.

MAIL is not set by the shell. On some systems, MAIL is set by login(1).

MAILCHECK

Specifies how often in seconds the shell checks for changes in the modification time of any of the files specified by the MAILPATH or MAIL variables. The default value is 600 seconds. When the time has elapsed the shell checks before issuing the next prompt.

The shell specifies a default value to MAILCHECK.

MAILPATH

A colon ( : ) 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 MAILCHECK seconds. Each file name can be followed by a ? and a message that is printed. The message undergoes parameter expansion, command substitution, and arithmetic substitution with the variable $_ defined as the name of the file that has changed. The default message is you have mail in $_.

PATH

The search path for commands. Except in .profile, users cannot change PATH if executing under rksh93. See the Execution section of this manual page.

The shell specifies a default value to PATH.

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 $. The character ! in the primary prompt string is replaced by the command number. Two successive occurrences of ! produces a single ! when the prompt string is printed. See the Command Re-entry section of this manual page.

The shell specifies a default value to PS1.

PS2

Secondary prompt string, by default, >.

The shell specifies a default value to PS2.

PS3

Selection prompt string used within a select loop, by default #?.

The shell specifies a default value to PS3.

PS4

The value of this variable is expanded for parameter evaluation, command substitution, and arithmetic substitution and precedes each line of an execution trace. By default, PS4 is +. When PS4 is unset, the execution trace prompt is also + .

The shell specifies a default value to PS4.

SHELL

The pathname of the shell is kept in the environment. At invocation, if the basename of this variable is rsh, rksh, rksh93, or krsh, the shell becomes restricted.

SHELL is not set by the shell. On some systems, SHELL is set by login(1).

TIMEFORMAT

The value of this parameter is used as a format string specifying how the timing information for pipelines prefixed with the time reserved word should be displayed. The % character introduces a format sequence that is expanded to a time value or other information.

The format sequences and their meanings are as follows.

%%

A literal %.

%[p][l]R

The elapsed time in seconds.

%[p][l]U

The number of CPU seconds spent in user mode.

%[p][l]S

The number of CPU seconds spent in system mode.

%P

The CPU percentage, computed as (U + S) / R.

The braces denote optional portions. The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point can be displayed. Values of p greater than 3 are treated as 3. If p is not specified, the value 3 is used.

The optional l specifies a longer format, including hours if greater than zero, minutes, and seconds of the form HHhMMmSS.FFs. The value of p determines whether or not the fraction is included.

All other characters are output without change and a trailing NEWLINE is added. If unset, the default value, $'\ real\\t%2lR\ user\\t%2lU\ sys%2lS', is used. If the value is null, no timing information is displayed.

TMOUT

If set to a value greater than zero, TMOUT is the default time-out value for the read built-in command. The select compound command terminates after TMOUT seconds when input is from a terminal. Otherwise, the shell terminates if a line is not entered within the prescribed number of seconds while reading from a terminal. The shell can be compiled with a maximum bound for this value which cannot be exceeded.

The shell specifies a default value to TMOUT.

VISUAL

If the value of this variable matches the pattern *[Vv][Ii]*, then the vi option is turned on. See Special Commands. If the value matches the pattern *gmacs* , the gmacs option is turned on. If the value matches the pattern *macs*, then the emacs option is turned on. The value of VISUAL overrides the value of EDITOR.

Field Splitting

After parameter expansion and command substitution, the results of substitutions are scanned for the field separator characters (those found in IFS) and split into distinct fields where such characters are found. Explicit null fields ("" or '') are retained. Implicit null fields, those resulting from parameters that have no values or command substitutions with no output, are removed.

If the braceexpand (-B) option is set, each of the fields resulting from IFS are checked to see if they contain one or more of the brace patterns. Valid brace patterns: {*,*}, {l1..l2} , {n1..n2}, {n1..n2%fmt} {n1..n2 ..n3}, or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are letters and n1,n2,n3 are signed numbers and fmt is a format specified as used by printf. In each case, fields are created by prepending the characters before the { and appending the characters after the } to each of the strings generated by the characters between the { and }. The resulting fields are checked to see if they have any brace patterns.

In the first form, a field is created for each string between { and ,, between , and ,, and between , and }. The string represented by * can contain embedded matching { and } without quoting. Otherwise, each { and } with * must be quoted.

In the second form, l1 and l2 must both be either upper case or both be lower case characters in the C locale. In this case a field is created for each character from l1 through l2.

In the remaining forms, a field is created for each number starting at n1. This continues until it reaches n2 and increments n1 by n3. The cases where n3 is not specified behave as if n3 were 1 if n1<=n2, and -1 otherwise. In forms which specify %fmt, any format flags, widths and precisions can be specified and fmt can end in any of the specifiers cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8 fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx, and z4cx.

File Name Generation

Following splitting, each field is scanned for the characters *, ?, (, and [, unless the -f option has been set. If one of these characters appears, then the word is regarded as a 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 file name is left unchanged unless the pattern is prefixed with ~(N) in which case it is removed. If FIGNORE is set, then each file name component that matches the pattern defined by the value of FIGNORE is ignored when generating the matching file names. The names . and .. are also ignored. If FIGNORE is not set, the character . at the start of each file name component is ignored unless the first character of the pattern corresponding to this component is the character . itself. For other uses of pattern matching the / and . are not specially treated.

*

Match any string, including the null string. When used for file name expansion, if the globstar option is on, two adjacent *s by themselves match all files and zero or more directories and subdirectories. If the two adjacent *s are followed by a /, only directories and subdirectories match.

?

Matches any single character.

[...]

Match any one of the enclosed characters. A pair of characters separated by - matches any character lexically between the pair, inclusive. If the first character following the opening [ is a !, any character not enclosed is matched. A - can be included in the character set by putting it as the first or last character. Within [ and ], character classes can be specified with the syntax [:class:] where class is one of the following classes defined in the ANSI-C standard:

alnum alpha blank cntrl digit graph lower print punct space upper word xdigit

word is equivalent to alnum plus the character _. Within [ and ], an equivalence class can be specified with the syntax [=c=] which matches all characters with the same primary collation weight (as defined by the current locale) as the character c. Within [ and ], [.symbol.] matches the collating symbol symbol.

A pattern-list is a list of one or more patterns separated from each other with an & or |. An & signifies that all patterns must be matched whereas | requires that only one pattern be matched. Composite patterns can be formed with one or more of the following sub-patterns:

?(pattern-list)

Optionally matches any one of the specified patterns.

*(pattern-list)

Matches zero or more occurrences of the specified patterns.

+(pattern-list)

Matches one or more occurrences of the specified patterns.

{n(pattern-list)

Matches n occurrences of the specified patterns.

{m,n(pattern-list)

Matches from m to n occurrences of the specified patterns. If m is omitted, 0 is used. If n is omitted at least m occurrences are matched.

@(pattern-list)

Matches exactly one of the specified patterns.

!(pattern-list)

Matches anything except one of the specified patterns.

By default, each pattern, or sub-pattern matches the longest string possible consistent with generating the longest overall match. If more than one match is possible, the one starting closest to the beginning of the string is chosen. However, for each of the compound patterns a - can be inserted in front of the ( to cause the shortest match to the specified pattern-list to be used.

When pattern-list is contained within parentheses, the backslash character \ is treated specially even when inside a character class. All ANSI-C character escapes are recognized and match the specified character. In addition the following escape sequences are recognized:

\d

Matches any character in the digit class.

\D

Matches any character not in the digit class.

\s

Matches any character in the space class.

\S

Matches any character not in the space class.

\w

Matches any character in the word class.

\W

Matches any character not in the word class.

A pattern of the form %(pattern-pairs) is a sub-pattern that can be used to match nested character expressions. Each pattern-pair is a two character sequence which cannot contain & or |. The first pattern-pair specifies the starting and ending characters for the match. Each subsequent pattern-pair represents the beginning and ending characters of a nested group that is skipped over when counting starting and ending character matches. The behavior is unspecified when the first character of a pattern-pair is alphanumeric except for the following:

D

Causes the ending character to terminate the search for this pattern without finding a match.

E

Causes the ending character to be interpreted as an escape character.

L

Causes the ending character to be interpreted as a quote character causing all characters to be ignored when looking for a match.

Q

Causes the ending character to be interpreted as a quote character causing all characters other than any escape character to be ignored when looking for a match.

%({}Q"E\), matches characters starting at { until the matching } is found not counting any { or } that is inside a double quoted string or preceded by the escape character \. Without the {} this pattern matches any C language string.

Each sub-pattern in a composite pattern is numbered, starting at 1, by the location of the ( within the pattern. The sequence \n, where n is a single digit and \n comes after the nth. sub-pattern, matches the same string as the sub-pattern itself.

A pattern can contain sub-patterns of the form ~(options:pattern-list), where either options or :pattern-list can be omitted. Unlike the other compound patterns, these sub-patterns are not counted in the numbered sub-patterns. If options is present, it can consist of one or more of the following:

+

Enable the following options. This is the default.

-

Disable the following options.

E

The remainder of the pattern uses extended regular expression syntax like the egrep(1) command.

F

The remainder of the pattern uses fgrep(1) expression syntax.

g

File the longest match (greedy).

This is the default.

G

The remainder of the pattern uses basic regular expression syntax like the grep(1) command.

i

Treat the match as case insensitive.

K

The remainder of the pattern uses shell pattern syntax.

This is the default.

l

Left anchor the pattern.

This is the default for K style patterns.

N

This is ignored. However, when it is the first letter and is used with file name generation, and no matches occur, the file pattern expands to the empty string.

r

Right anchor the pattern.

This is the default for K style patterns.

If both options and :pattern-list are specified, then the options apply only to pattern-list. Otherwise, these options remain in effect until they are disabled by a subsequent ~(...) or at the end of the sub-pattern containing ~(...).

Quoting

Each of the metacharacters listed in the Definitions has a special meaning to the shell.

g

File the longest match (greedy). This is the default.

i

Treat the match as case insensitive.

If both options and :pattern-list are specified, then the options apply only to pattern-list. Otherwise, the options remain in effect until they are disabled by a subsequent ~(...) or at the end of the sub-pattern containing ~(...).

Each of the metacharacters listed in the Definitions section of this manual page has a special meaning to the shell and causes termination of a word unless quoted. A character can be quoted, that is, made to stand for itself, by preceding it with a backslash (\). The pair \NEWLINE is removed. All characters enclosed between a pair of single quote marks ('') that is not preceded by a $ are quoted. A single quote cannot appear within the single quotes. A single quoted string preceded by an unquoted $ is processed as an ANSI-C string except for the following:

\0

Causes the remainder of the string to be ignored.

\cx

Expands to the character CTRL-x.

\C[.name.]

Expands to the collating element name.

\e

Equivalent to the escape character (ASCII 033),

\E

Equivalent to the escape character (ASCII 033),

Inside double quote marks (""), parameter and command substitution occur and \ quotes the characters \, ‘, ", and $. A $ in front of a double quoted string is ignored in the C or POSIX locale, and might cause the string to be replaced by a locale specific string otherwise. The meaning of $* and $@ is identical when not quoted or when used as a variable assignment value or as a file name. However, when used as a command argument, "$*" is equivalent to "$1d$2d...", where d is the first character of the IFS variable, whereas "$@" is equivalent to "$1" "$2" .... Inside grave quote marks (‘‘), \\ quotes the characters \, ‘, and $. If the grave quotes occur within double quotes, then \ also quotes the character ".

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 cannot be altered by quoting them.

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 shift and let. Arithmetic evaluation is also performed on argument operands of the built-in command printf that correspond to numeric format specifiers in the format operand. See printf(1). Evaluations are performed using double precision floating point arithmetic or long double precision floating point for systems that provide this data type. Floating point constants follow the ANSI-C programming language floating point conventions. Integer constants follow the ANSI-C programming language integer constant conventions although only single byte character constants are recognized and character casts are not recognized. Constants can be of the form [base#]n where base is a decimal number between two and sixty-four representing the arithmetic base and n is a number in that base. The digits greater than 9 are represented by the lower case letters, the upper case letters, @, and _ respectively. For bases less than or equal to 36, upper and lower case characters can be used interchangeably.

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, the operator ** can be used for exponentiation. It has higher precedence than multiplication and is left associative. When the value of an arithmetic variable or subexpression 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.

Any of the following math library functions that are in the C math library can be used within an arithmetic expression:

abs acos acosh asin asinh atan atan2 atanh cbrt copysign cos cosh erf erfc exp exp2 expm1 fabs fdim finite floor fma fmax fmod hypot ilogb int isinf isnan lgamma log log2 logb nearbyint nextafter nexttoward pow remainder rint round sin sinh sqrt tan tanh tgamma trunc

An internal representation of a variable as a double precision floating point can be specified with the -E [n] or -F [n] option of the typeset special built-in command. The -E option causes the expansion of the value to be represented using scientific notation when it is expanded. The optional option argument n defines the number of significant figures. The -F option causes the expansion to be represented as a floating decimal number when it is expanded. The optional option argument n defines the number of places after the decimal point in this case.

An internal integer representation of a variable can be specified with the -i [n] option of the typeset special built-in command. The optional option argument n specifies an arithmetic base to be used when expanding the variable. If you do not specify an arithmetic base, base 10 is used.

Arithmetic evaluation is performed on the value of each assignment to a variable with the -E, -F, or -i option. Assigning a floating point number to a variable whose type is an integer causes the fractional part to be truncated.

Prompting

When used interactively, the shell prompts with the value of PS1 after expanding it for parameter expansion, command substitution, and arithmetic substitution, before reading a command. In addition, each single ! in the prompt is replaced by the command number. A !! is required to place ! in the prompt. If at any time a NEWLINE is typed and further input is needed to complete a command, then the secondary prompt, that is, the value of PS2, is issued.

Conditional Expressions

A conditional expression is used with the [[ compound command to test attributes of files and to compare strings. Field splitting and file name generation are not performed on the words between [[ and ]].

Each expression can be constructed from one or more of the following unary or binary expressions:

-a file

True, if file exists.

This option is the same as -e. This option is obsolete.

-b file

True, if file exists and is a block special file.

-c file

True, if file exists and is a character special file.

-d file

True, if file exists and is a directory.

-e file

True, if file exists.

-f file

True, if file exists and is an ordinary file.

-g file

True, if file exists and it has its setgid bit set.

-G file

True, if file exists and its group matches the effective group id of this process.

-h file

True, if file exists and is a symbolic link.

-k file

True, if file exists and it has its sticky bit set.

-L file

True, if file exists and is a symbolic link.

-n string

True, if length of string is non-zero.

-N file

True, if file exists and the modification time is greater than the last access time.

-o option

True, if option named option is on.

-o ?option

True, if option named option is a valid option name.

-O file

True, if file exists and is owned by the effective user id of this process.

-p file

True, if file exists and is a FIFO special file or a pipe.

-r file

True, if file exists and is readable by current process.

-s file

True, if file exists and has size greater than zero.

-S file

True, if file exists and is a socket.

-t fildes

True, if file descriptor number fildes is open and associated with a terminal device.

-u file

True, if file exists and it has its setuid bit set.

-w file

True, if file exists and is writable by current process.

-x file

True, if file exists and is executable by current process. If file exists and is a directory, then true if the current process has permission to search in the directory.

-z string

True, if length of string is zero.

file1 -ef file2

True, if file1 and file2 exist and refer to the same file.

file1 -nt file2

True, if file1 exists and file2 does not, or file1 is newer than file2.

file1 -ot file2

True, if file2 exists and file1 does not, or file1 is older than file2.

string

True, if string is not null.

string == pattern

True, if string matches pattern. Any part of pattern can be quoted to cause it to be matched as a string. With a successful match to pattern, the .sh.match array variable contains the match and sub-pattern matches.

string = pattern

Same as ==, but is obsolete.

string != pattern

True, if string does not match pattern. When the string matches the pattern the .sh.match array variable contains the match and sub-pattern matches.

string =~ ere

True if string matches the pattern ~(E)ere where ere is an extended regular expression.

string1 < string2

True, if string1 comes before string2 based on ASCII value of their characters.

string1 > string2

True, if string1 comes after string2 based on ASCII value of their characters.

In each of the following expressions, if file is of the form /dev/fd/n, where n is an integer, the test is applied to the open file whose descriptor number is n. The following obsolete arithmetic comparisons are supported:

exp1 -eq exp2

True, if exp1 is equal to exp2.

exp1 -ge exp2

True, if exp1 is greater than or equal to exp2.

exp1 -gt exp2

True, if exp1 is greater than exp2.

exp1 -le exp2

True, if exp1 is less than or equal to exp2.

exp1 -lt exp2

True, if exp1 is less than exp2.

exp1 -ne exp2

True, if exp1 is not equal to exp2.

A compound expression can be constructed from these primitives by using any of the following, listed in decreasing order of precedence:

(expression)

True, if expression is true. Used to group expressions.

! expression

True, if expression is false.

expression1 && expression2

True, if expression1 and expression2 are both true.

expression1 || expression2

True, if either expression1 or expression2 is true.

Input and Output

Before a command is executed, its input and output can be redirected using a special notation interpreted by the shell. The following can appear anywhere in a simple command or can precede or follow a command and are not passed on to the invoked command. Command substitution, parameter expansion, and arithmetic substitution occur before word or digit is used except as noted in this section. File name generation occurs only if the shell is interactive and the pattern matches a single file. Field splitting is not performed.

In each of the following redirections, if file is of the form /dev/sctp/host/port, /dev/tcp/host/port, or /dev/udp/host/port, where host is a hostname or host address, and port is a service specified by name or an integer port number, then the redirection attempts to make a tcp, sctp or udp connection to the corresponding socket.

No intervening space is allowed between the characters of redirection operators.

<word

Use file word as standard input (file descriptor 0).

>word

Use file word as standard output (file descriptor 1). If the file does not exist then it is created. If the file exists, and the noclobber option is on, this causes an error. Otherwise, it is truncated to zero length.

>|word

Same as >, except that it overrides the noclobber option.

>>word

Use file 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.

<>word

Open file word for reading and writing as standard input.

<<[-]word

The shell input is read up to a line that is the same as word after any quoting has been removed, or to an end-of-file. No parameter substitution, command substitution, arithmetic substitution or file name generation is performed on word. The resulting document, called a here-document, becomes the standard input. If any character of word is quoted, then no interpretation is placed upon the characters of the document. Otherwise, parameter expansion, command substitution, and arithmetic substitution occur, \NEWLINE is ignored, and \ must be used to quote the characters \, $, ‘. If - is appended to <<, then all leading tabs are stripped from word and from the document. If # is appended to <<, then leading SPACEs and TABs are stripped off the first line of the document and up to an equivalent indentation is stripped from the remaining lines and from word. A tab stop is assumed to occur at every 8 columns for the purposes of determining the indentation.

<<<word

A short form of here document in which word becomes the contents of the here-document after any parameter expansion, command substitution, and arithmetic substitution occur.

<&digit

The standard input is duplicated from file descriptor digit, and similarly for the standard output using >&digit. See dup(2).

<&digit-

The file descriptor specified by digit is moved to standard input. Similarly for the standard output using >&digit-.

<&-

The standard input is closed. Similarly for the standard output using >&-.

<&p

The input from the co-process is moved to standard input.

>&p

The output to the co-process is moved to standard output.

<#((expr))

Evaluate arithmetic expression expr and position file descriptor 0 to the resulting value bytes from the start of the file. The variables CUR and EOF evaluate to the current offset and end-of-file offset respectively when evaluating expr.

>#((expr))

The same as <# except applies to file descriptor 1.

<#pattern

Seek forward to the beginning of the next line containing pattern.

<##pattern

The same as <#, except that the portion of the file that is skipped is copied to standard output.

If one of the redirection operators is preceded by a digit, with no intervening space, then the file descriptor number referred to is that specified by the digit (instead of the default 0 or 1). If one of the redirection operators other than >&- and the ># and <# forms, is preceded by {varname} with no intervening space, then a file descriptor number > 10 is selected by the shell and stored in the variable varname. If >&- or the any of the ># and <# forms is preceded by {varname} the value of varname defines the file descriptor to close or position. For example:

... 2>&1

means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and

exec [n]<file

means open file for reading and store the file descriptor number in variable n. The order in which redirections are specified is significant. The shell evaluates each redirection in terms of the (file_descriptor, file) association at the time of evaluation. For example:

... 1>fname 2>&1

first associates file descriptor 1 with file fname. It then associates file descriptor 2 with the file associated with file descriptor 1, that is, 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 fname. If a command is followed by & and job control is not active, the default standard input for the command is the empty file /dev/null. Otherwise, the environment for the execution of a command contains the file descriptors of the invoking shell as modified by input and output specifications.

Environment

The environment is a list of name-value pairs that is passed to an executed program in the same way as a normal argument list. See environ(5).

The names must be 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 export. Executed commands inherit the environment. If the user modifies the values of these variables or creates new ones, using the export or 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 can be modified by the current shell, plus any additions which must be noted in export or typeset -x commands. The environment for any simple-command or function can be augmented by prefixing it with one or more variable assignments. A variable assignment argument is a word of the form identifier=value. Thus:

TERM=450 cmd args

and

(export TERM; TERM=450; cmd args)

are equivalent (as far as the execution of cmd is concerned except for special built-in commands listed in the Built-Ins section, those that are preceded with a dagger. If the obsolete -k option is set, all variable assignment arguments are placed in the environment, even if they occur after the command name.

The following example first prints a=b c and then c:

echo a=b c set -k echo a=b c

This feature is intended for use with scripts written for early versions of the shell and its use in new scripts is strongly discouraged.

Functions

For historical reasons, there are two ways to define functions, the name() syntax and the function name syntax. These are described in the Commands section of this manual page.

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 the Execution section of this manual page for details.

Functions defined by the function 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 EXIT set inside a function is executed in the environment of the caller after the function completes. Ordinarily, variables are shared between the calling program and the function. However, the typeset special built-in command used within a function defines local variables whose scope includes the current function. They can be passed to functions that they call in the variable assignment list that precedes the call or as arguments passed as name references. Errors within functions return control to the caller.

Functions defined with the name() syntax and functions defined with the function name syntax that are invoked with the . 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.

The special built-in command return is used to return from function calls.

Function names can be listed with the -f or +f option of the typeset special built-in command. The text of functions, when available, is also listed with -f. Functions can be undefined with the -f option of the unset special built-in command.

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 FPATH variable should contain the name of this directory. They can also be specified in the ENV file.

Discipline Functions

Each variable can have zero or more discipline functions associated with it. The shell initially understands the discipline names get, set, append, and unset but on most systems others can be added at run time via the C programming interface extension provided by the builtin built-in utility. If the get discipline is defined for a variable, it is invoked whenever the specified variable is referenced. If the variable .sh.value is assigned a value inside the discipline function, the referenced variable is evaluated to this value instead. If the set discipline is defined for a variable, it is invoked whenever the specified variable is assigned a value. If the append discipline is defined for a variable, it is invoked whenever a value is appended to the specified variable. The variable .sh.value is specified the value of the variable before invoking the discipline, and the variable is assigned the value of .sh.value after the discipline completes. If .sh.value is unset inside the discipline, then that value is unchanged. If the unset discipline is defined for a variable, it is invoked whenever the specified variable is unset. The variable is not unset unless it is unset explicitly from within this discipline function.

The variable .sh.name contains the name of the variable for which the discipline function is called, .sh.subscript is the subscript of the variable, and .sh.value contains the value being assigned inside the set discipline function. For the set discipline, changing .sh.value changes the value that gets assigned.

Jobs

If the monitor option of the set command is turned on, an interactive shell associates a job with each pipeline. It keeps a table of current jobs, printed by the jobs command, and assigns them small integer numbers. When a job is started asynchronously with &, the shell prints a line which looks like:

[1] 1234

indicating that the job which was started asynchronously was job number 1 and had one (top-level) process, whose process id was 1234.

If you are running a job and wish to stop it, CTRL-z sends a STOP signal to the current job. The shell normally displays a message that the job has been stopped, and displays another prompt. You can then manipulate the state of this job, putting it in the background with the bg command, or run some other commands and then eventually bring the job back into the foreground with the foreground command fg. A CTRL-z takes effect immediately and is like an interrupt in that pending output and unread input are discarded when it is typed.

A job being run in the background stops 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 sttytostop. If you set this tty option, then background jobs stop when they try to produce output like they do when they try to read input.

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:

%number

The job with the specified number.

%string

Any job whose command line begins with string.

%?string

Any job whose command line contains string.

%%

Current job.

%+

Equivalent to %%.

%-

Previous job.

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 notify option of the set command causes the shell to print these job change messages as soon as they occur.

When the monitor option is on, each background job that completes triggers any trap set for CHLD.

When you try to leave the shell while jobs are running or stopped, you are warned that You have stopped(running) jobs. You can use the jobs command to see what they are. If you immediately try to exit again, the shell does not warn you a second time, and the stopped jobs are terminated. When a login shell receives a HUP signal, it sends a HUP signal to each job that has not been disowned with the disown built-in command.

Signals

The INT and QUIT signals for an invoked command are ignored if the command is followed by & and the monitor option is not active. Otherwise, signals have the values inherited by the shell from its parent. See the trap built-in command.

Execution

Each time a command is read, the substitutions are carried out. If the command name matches one of the ones in the Special Built-in Commands section of this manual page, 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 function call. A function is also executed in the current shell process. When the function completes or issues a return, the positional parameter list is restored. For functions defined with the function name syntax, any trap set on EXIT within the function is executed. The exit value of a function is the value of the last command executed. If a command name is not a special built-in command or a user defined function, but it is one of the built-in commands, it is executed in the current shell process.

The shell variable PATH defines the search path for the directory containing the command. Alternative directory names are separated by a colon (:). The default path is /bin:/usr/bin:, specifying /bin, /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 slash (/), the search path is not used. Otherwise, each directory in the path is searched for an executable file of the specified name that is not a directory. If found, and if the shell determines that there is a built-in version of a command corresponding to a specified pathname, this built-in is invoked in the current process. If found, and this directory is also contained in the value of the FPATH variable, then this file is loaded into the current shell environment as if it were the argument to the . command except that only preset aliases are expanded, and a function of the specified name is executed as described in this manual page. If not found, and the file .paths is found, and this file contains a line of the form FPATH=path where path is an existing directory, and this directory contains a file of the specified name, then this file is loaded into the current shell environment as if it were the argument to the . special built-in command and a function of the specified name is executed. Otherwise, if found, a process is created and an attempt is made to execute the command using exec(2).

When an executable is found, the directory where it is found in is searched for a file named .paths. If this file is found and it contains a line of the form BUILTIN_LIB=value, the library named by value is searched for as if it were an option argument to builtin -f, and if it contains a built-in of the specified name this is executed instead of a command by this name. Otherwise, if this file is found and it contains a line of the form name=value in the first or second line, then the environment variable name is modified by prepending the directory specified by value to the directory list. If value is not an absolute directory, then it specifies a directory relative to the directory that the executable was found. If the environment variable name does not already exist it is added to the environment list for the specified command.

If the file has execute permission but is not an 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, and/or if the setuid and 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.

Command Re-entry

The text of the last HISTSIZE (default 512) commands entered from a terminal device is saved in a history file. The file $HOME/.sh_history is used if the HISTFILE variable is not set or if the file it names is not writable. A shell can access the commands of all interactive shells which use the same named HISTFILE. The built-in command 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 hist then the value of the variable HISTEDIT is used. If HISTEDIT is unset, the obsolete variable FCEDIT is used. If FCEDIT is not defined, then /bin/ed is used. The edited commands are printed and executed again upon leaving the editor unless you quit without writing. The -s option (and in obsolete versions, the editor name -) is used to skip the editing phase and to re-execute the command. In this case a substitution parameter of the form old=newcan be used to modify the command before execution. For example, with the preset alias r, which is aliased to 'hist -s', typing `r bad=good c' re-executes the most recent command which starts with the letter c, replacing the first occurrence of the string bad with the string good.

Inline Editing Options

Normally, each command line entered from a terminal device is simply typed followed by a NEWLINE (RETURN or LINE FEED). If either the emacs, gmacs, or vi option is active, the user can edit the command line. To be in either of these edit modes set the corresponding option. An editing option is automatically selected each time the VISUAL or EDITOR variable is assigned a value ending in either of these option names.

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.

Unless the multiline option is on, 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 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 is centered about the cursor. The mark is a > (<, *) if the line extends on the right , left, or both sides of the window.

The search commands in each edit mode provide access to the history file. Only strings are matched, not patterns, although a leading ^ in the string restricts the match to begin at the first character in the line.

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 ;, |, &, or (, and the word does not begin with ~ or contain a /, the list of aliases, functions, and executable commands defined by the PATH variable that could match the partial word is displayed. Otherwise, the list of files that match the specified word is displayed. If the partially entered word does not contain any file expansion characters, a * 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 / 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 / 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. When using a TAB for completion that does not yield a unique match, a subsequent TAB provides a numbered list of matching alternatives. A specific selection can be made by entering the selection number followed by a TAB.

Key Bindings

The 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 ESC) is entered while reading from a terminal.

The variable .sh.edchar contains the character or character sequence which generated the trap. Changing the value of .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. The variable .sh.edcol is set to the input column number of the cursor at the time of the input. The variable .sh.edmode is set to ESC when in vi insert mode and is null otherwise. By prepending ${.sh.editmode} to a value assigned to .sh.edchar it causes the shell to change to control mode if it is not already in this mode.

This trap is not invoked for characters entered as arguments to editing directives, or while reading input for a character search.

emacs Editing Mode

This mode is entered by enabling either the emacs or gmacs option. The only difference between these two modes is the way they handle ^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 (^) followed by the character.

For example, ^F is the notation for CTRL/F. This is entered by depressing f while holding down the CTRL (control) key. The SHIFT key is not depressed. (The notation ^? indicates the DEL (delete) key.)

The notation for escape sequences is M- followed by a character. For example, M-f (pronounced Meta f) is entered by depressing ESC (ASCII 033) followed by f. M-F is the notation for ESC followed by F.

All edit commands operate from any place on the line, not just at the beginning. The RETURN or the LINE FEED key is not entered after edit commands except when noted.

^F

Move the cursor forward (right) one character.

M-[C

Move the cursor forward (right) one character.

M-f

Move the cursor forward one word. The emacs editor's idea of a word is a string of characters consisting of only letters, digits and underscores.

^B

Move the cursor backward (left) one character.

M-[D

Move the cursor backward (left) one character.

M-b

Move the cursor backward one word.

^A

Move the cursor to the beginning of the line.

M-[H

Move the cursor to the beginning of the line.

^E

Move the cursor to the end of the line.

M-[Y

Move the cursor to the end of line.

^]char

Move the cursor forward to the character char on the current line.

M-^]char

Move the cursor backwards to the character char on the current line.

^X^X

Interchange the cursor and the mark.

erase

Delete the previous character. The user-defined erase character is defined by the stty(1) command, and is usually ^H or #.

lnext

Removes the next character's editing features. The user-defined literal next character is defined by the stty(1) command, or is ^V if not defined.

^D

Delete the current character.

M-d

Delete the current word.

M-^H

MetaBACKSPACE. Delete the previous word.

M-h

Delete the previous word.

M-^?

MetaDEL. Delete the previous word. If your interrupt character is ^? (DEL, the default), this command does not work.

^T

Transpose the current character with the previous character, and advance the cursor in emacs mode. Transpose two previous characters in gmacs mode.

^C

Capitalize the current character.

M-c

Capitalize the current word.

M-l

Change the current word to lower case.

^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, delete from specified 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 specified cursor position.

^W

Kill from the cursor to the mark.

M-p

Push the region from the cursor to the mark on the stack.

kill

Kill the entire current line. The user-defined kill character is defined by the stty(1) command, usually a ^G or @. If two kill characters are entered in succession, all kill characters from then on cause a line feed. This is useful when using paper terminals.

^Y

Restore the last item removed from line. Yank the item back to the line.

^L

Line feed and print the current line.

M-^L

Clear the screen.

^@

Null character. Set mark.

M-space

MetaSPACE. Set the mark.

^J

New line. Execute the current line.

^M

Return. Execute the current line.

EOF

End-of-file character, normally ^D, is processed as an end-of-file only if the current line is null.

^P

Fetch the previous command. Each time ^P is entered the previous command back in time is accessed. Moves back one line when it is not on the first line of a multi-line command.

M-[A

Equivalent to ^P.

M-<

Fetch the least recent (oldest) history line.

M->

Fetch the most recent (youngest) history line.

^N

Fetch the next command line. Each time ^N is entered the next command line forward in time is accessed.

M-[B

Equivalent to ^N.

^Rstring

Reverse search history for a previous command line containing string. If a parameter of zero is specified, the search is forward. string is terminated by a RETURN or NEWLINE. If string is preceded by a ^, the matched line must begin with string. If string is omitted, then the next command line containing the most recent string is accessed. In this case a parameter of zero reverses the direction of the search.

^O

Operate. Execute the current line and fetch the next line relative to current line from the history file.

M-digits

Escape. Define numeric parameter. The digits are taken as a parameter to the next command. The commands that accept a parameter are: ^F, ^B, ERASE, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-., M-, M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l, and M-^H.

M-letter

Soft-key. Search the alias list for an alias by the name letter. If an alias of letter is defined, insert its value on the input queue. letter must not be one of the metafunctions in this section.

M-[letter

Soft key. Search the alias list for an alias by the name letter. If an alias of this name is defined, insert its value on the input queue. This can be used to program function keys on many terminals.

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.

M-_

Same as M-..

M-*

Attempt filename generation on the current word. As asterisk is appended if the word does not match any file or contain any special pattern characters.

M-ESC

Command or file name completion as described in this manual page.

^ITAB

Attempts command or file name completion as described in this manual page. If a partial completion occurs, repeating this behaves as if M-= were entered. If no match is found or entered after SPACE, a TAB is inserted.

M-=

If not preceded by a numeric parameter, generates the list of matching commands or file names as described in this manual page. Otherwise, the word under the cursor is replaced by the item corresponding to the value of the numeric parameter from the most recently generated command or file list. If the cursor is not on a word, the word is inserted instead.

^U

Multiply parameter of next command by 4.

\

Escape the next character. Editing characters, the user's erase, kill and interrupt (normally ^?) characters can be entered in a command line or in a search string if preceded by a \. The \ removes the next character's editing features, if any.

M-^V

Display the version of the shell.

M-#

If the line does not begin with a #, a # is inserted at the beginning of the line and after each NEWLINE, and the line is entered. This causes a comment to be inserted in the history file. If the line begins with a #, the # is deleted and one # after each NEWLINE is also deleted.

vi Editing Mode

There are two typing modes. Initially, when you enter a command you are in the input mode. To edit, the user enters control mode by typing ESC (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 count prior to the command.

When in vi mode on most systems, canonical processing is initially enabled and the command is 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.

If the option viraw is also set, the terminal is always have canonical processing disabled. This mode is implicit for systems that do not support two alternate end of line delimiters, and might be helpful for certain terminals.

Input Edit Commands

By default the editor is in input mode.

The following input edit commands are supported:

ERASE

User defined erase character as defined by the stty command, usually ^H or #. Delete previous character.

^W

Delete the previous blank separated word. On some systems the viraw option might be required for this to work.

EOF

As the first character of the line causes the shell to terminate unless the ignoreeof option is set. Otherwise this character is ignored.

lnext

User defined literal next character as defined by the stty(1) or ^V if not defined. Removes the next character's editing features, if any. On some systems the viraw option might be required for this to work.

\

Escape the next ERASE or KILL character.

^I TAB

Attempts command or file name completion as described in this manual page and returns to input mode. If a partial completion occurs, repeating this behaves as if = were entered from control mode. If no match is found or entered after SPACE, a TAB is inserted.

Motion Edit Commands

The motion edit commands move the cursor.

The following motion edit commands are supported:

[count]l

Move the cursor forward (right) one character.

[count][C

Move the cursor forward (right) one character.

[count]w

Move the cursor forward one alphanumeric word.

[count]W

Move the cursor to the beginning of the next word that follows a blank.

[count]e

Move the cursor to the end of the word.

[count]E

Move the cursor to the end of the current blank delimited word.

[count]h

Move the cursor backward (left) one character.

[count][D

Move the cursor backward (left) one character.

[count]b

Move the cursor backward one word.

[count]B

Move the cursor to the preceding blank separated word.

[count]|

Move the cursor to column count.

[count]fc

Find the next character c in the current line.

[count]Fc

Find the previous character c in the current line.

[count]tC

Equivalent to f followed by h.

[count]Tc

Equivalent to F followed by l.

[count];

Repeat count times the last single character find command: f, F, t, or T.

[count],

Reverse the last single character find command count times.

0

Move the cursor to the start of line.

^

Move the cursor to start of line.

[H

Move the cursor to the first non-blank character in the line.

$

Move the cursor to the end of the line.

[Y

Move the cursor to the end of the line.

%

Moves to balancing (, ), {, }, [, or ]. If cursor is not on one of the characters described in this section, the remainder of the line is searched for the first occurrence of one of the characters first.

Search Edit Commands

The search edit commands access your command history.

The following search edit commands are supported:

[count]k

Fetch the previous command. Each time k is entered, the previous command back in time is accessed.

[count]-

Fetch the previous command. Each time k is entered, the previous command back in time is accessed.

Equivalent to k.

[count][A

Fetch the previous command. Each time k is entered, the previous command back in time is accessed.

Equivalent to k.

[count]j

Fetch the next command. Each time j is entered, the next command forward in time is accessed.

[count]+

Fetch the next command. Each time j is entered, the next command forward in time is accessed.

Equivalent to j.

[count][B

Fetch the next command. Each time j is entered, the next command forward in time is accessed.

Equivalent to j.

[count]G

Fetch command number count. The default is the least recent history command.

/string

Search backward through history for a previous command containing string. string is terminated by a RETURN or NEWLINE. If string is preceded by a ^, the matched line must begin with string. If string is null, the previous string is used.

?string

Search forward through history for a previous command containing string. string is terminated by a RETURN or NEWLINE. If string is preceded by a ^, the matched line must begin with string. If string is null, the previous string is used.

Same as / except that search is in the forward direction.

n

Search in the backwards direction for the next match of the last pattern to / or ? commands.

N

Search in the forward direction for next match of the last pattern to / or ?.

Text Modification Edit Commands

The following commands modify the line:

a

Enter input mode and enter text after the current character.

A

Append text to the end of the line. Equivalent to $a.

[count]cmotion
c[count]motion

Delete current character through the character that motion would move the cursor to and enter input mode. If motion is c, the entire line is deleted and input mode entered.

C

Delete the current character through the end of line and enter input mode. Equivalent to c$.

S

Equivalent to cc.

[count]s

Replace characters under the cursor in input mode.

D[count]dmotion

Delete the current character through the end of line. Equivalent to d$.

d[count]motion

Delete current character through the character that motion would move to. If motion is d , the entire line is deleted.

i

Enter input mode and insert text before the current character.

I

Insert text before the beginning of the line. Equivalent to 0i.

[count]P

Place the previous text modification before the cursor.

[count]p

Place the previous text modification after the cursor.

R

Enter input mode and replace characters on the screen with characters you type overlay fashion.

[count]rc

Replace the count characters starting at the current cursor position with c, and advance the cursor.

[count]x

Delete current character.

[count]X

Delete preceding character.

[count].

Repeat the previous text modification command.

[count]~

Invert the case of the count characters starting at the current cursor position and advance the cursor.

[count]_

Causes the count word of the previous command to be appended and input mode entered. The last word is used if count is omitted.

*

Causes an * 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.

\

Command or file name completion as described in this manual page.

Other Edit Commands

The following miscellaneous edit commands are supported:

[count]ymotion
y[count]motion

Yank the current character through the character to which motion would move the cursor. Put the yanked characters in the delete buffer. The text and cursor position are unchanged.

yy

Yank the current line.

Y

Yank the current line from the current cursor location to the end of the line. Equivalent to y$.

u

Undo the last text modifying command.

U

Undo all the text modifying commands performed on current line.

[count]V

Return the command :

hist -e ${VISUAL:-${EDITOR:-vi}} count

in the input buffer. If count is omitted, the current line is used.

^L

Line feed and print the current line. This command only works in control mode.

^J

New line. Execute the current line, regardless of mode.

^M

Return. Execute the current line, regardless of mode.

#

If the first character of the command is a # , delete this # and each # that follows a NEWLINE.

Otherwise, send the line after inserting a # in front of each line in the command.

This is command is useful for causing the current line to be inserted in the history as a comment and un-commenting previously commented commands in the history file.

[count]=

If count is not specified, generate the list of matching commands or file names as described in this manual page.

Otherwise, replace the word at the current cursor location with the count item from the most recently generated command or file list. If the cursor is not on a word, it is inserted after the current cursor location.

@letter

Search your alias list for an alias by the name letter. If an alias of this name is defined, insert its value on the input queue for processing.

^V

Display version of the shell.

Built-in Commands

The following simple-commands are executed in the shell process. Input and 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 0. Except for :, true, false, echo, newgrp, and login, all built-in commands accept -- to indicate the end of options. They also interpret the option --man as a request to display the manual page onto standard error and -? as a help request which prints a usage message on standard error.

Commands that are preceded by one or two ++ symbols are special built-in commands and are treated specially in the following ways:

1. Variable assignment lists preceding the command remain in effect when the command completes.

2. I/O redirections are processed after variable assignments.

3. Errors cause a script that contains them to abort.

4. They are not valid function names.

5. Words following a command preceded by ++ 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 = sign and field splitting and file name generation are not performed.

+ : [arg ...]

The command only expands parameters.

+ . name [arg ...]

If name is a function defined with the function name reserved word syntax, the function is executed in the current environment (as if it had been defined with the name() syntax.) Otherwise if 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 PATH is used to find the directory containing the file. If any arguments arg are specified, they become the positional parameters while processing the . command and the original positional parameters are restored upon completion. Otherwise the positional parameters are unchanged. The exit status is the exit status of the last command executed.

++ alias [-ptx] [name[ =value]] ...

alias with no arguments prints the list of aliases in the form name=value on standard output. The -p option causes the word alias to be inserted before each one. When one or more arguments are specified, an alias is defined for each name whose value is specified. A trailing space in value causes the next word to be checked for alias substitution. The obsolete -t option is used to set and list tracked aliases. The value of a tracked alias is the full pathname corresponding to the specified name. The value becomes undefined when the value of PATH is reset but the alias remains tracked. Without the -t option, for each name in the argument list for which no value is specified, the name and value of the alias is printed. The obsolete -x option has no effect. The exit status is non-zero if a name is specified, but no value, and no alias has been defined for the name.

bg [ job...]

This command is only on systems that support job control. Puts each specified job into the background. The current job is put in the background if job is not specified. See the Jobs section of this manual page for a description of the format of job.

+ break [n]

Exit from the enclosing for, while, until, or select loop, if any. If n is specified, then break n levels.

builtin [-ds ] [-f file] [name ...]

If name is not specified, and no -f option is specified, the built-ins are printed on standard output. The -s option prints only the special built-ins. Otherwise, each name represents the pathname whose basename is the name of the built-in. The entry point function name is determined by prepending b to the built-in name. The ISO C/C++ prototype is bmycommand(int argc, char *argv[], void *context) for the built-in command mycommand where argv is an array of argc elements and context is an optional pointer to a Shell_t structure as described in <ast/shell.h> Special built-ins cannot be bound to a pathname or deleted. The -d option deletes each of the specified built-ins. On systems that support dynamic loading, the -f option names a shared library containing the code for built-ins. The shared library prefix and/or suffix, which depend on the system, can be omitted. Once a library is loaded, its symbols become available for subsequent invocations of builtin. Multiple libraries can be specified with separate invocations of the builtin command. Libraries are searched in the reverse order in which they are specified. When a library is loaded, it looks for a function in the library whose name is lib_init() and invokes this function with an argument of 0.

cd [-LP] [arg]
cd [-LP] old new

This command has two forms.

In the first form it changes the current directory to arg. If arg is a -, the directory is changed to the previous directory. The shell variable HOME is the default arg. The variable PWD is set to the current directory. The shell variable CDPATH defines the search path for the directory containing arg. Alternative directory names are separated by a colon (:). The default path is NULL (specifying the current directory). 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 arg begins with a /, the search path is not used. Otherwise, each directory in the path is searched for arg.

The second form of cd substitutes the string new for the string old in the current directory name, PWD, and tries to change to this new directory. By default, symbolic link names are treated literally when finding the directory name. This is equivalent to the -L option. The -P option causes symbolic links to be resolved when determining the directory. The last instance of -L or -P on the command line determines which method is used. The cd command cannot be executed by rksh93.

command [-pvVx] name [arg ...]

Without the -v or -V options, executes name with the arguments specified by arg.

The -p option causes a default path to be searched rather than the one defined by the value of PATH. Functions are not searched when finding name. In addition, if name refers to a special built-in, none of the special properties associated with the leading daggers are honored. For example, the predefined alias redirect='command exec' prevents a script from terminating when an invalid redirection is specified.

With the -x option, if command execution would result in a failure because there are too many arguments, errno E2BIG, the shell invokes command name multiple times with a subset of the arguments on each invocation. Arguments that occur prior to the first word that expands to multiple arguments and after the last word that expands to multiple arguments are passed on each invocation. The exit status is the maximum invocation exit status.

With the -v option, command is equivalent to the built-in whence command described in this section. The -V option causes command to act like whence -v.

+continue [n]

Resumes the next iteration of the enclosing for, while, until, or select loop. If n is specified, then resume at the nth enclosing loop.

disown [job...]

Causes the shell not to send a HUP signal to each specified job, or all active jobs if job is omitted, when a login shell terminates.

echo [arg ...]

When the first arg does not begin with a -, and none of the arguments contain a backslash (\), prints each of its arguments separated by a SPACE and terminated by a NEWLINE. Otherwise, the behavior of echo is system dependent and print or printf described in this section should be used. See echo(1) for usage and description.

+eval [arg ...]

The arguments are read as input to the shell and the resulting commands are executed.

+exec [-c] [-a name ...] [arg ...]

If arg is specified, the command specified by the arguments is executed in place of this shell without creating a new process. The -c option causes the environment to be cleared before applying variable assignments associated with the exec invocation. The -a option causes name rather than the first arg, to become argv[0] for the new process. Input and output arguments can appear and affect the current process. If arg is not specified, 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.

+exit [n]

Causes the shell to exit with the exit status specified by n. The value is the least significant 8 bits of the specified status. If n is omitted, then the exit status is that of the last command executed. An end-of-file also causes the shell to exit except for a shell which has the ignoreeof option turned on. See set.

++export [-p] [name[=value]] ...

If name is not specified, 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-entered. The -p option causes the word export to be inserted before each one. Otherwise, the specified names are marked for automatic export to the environment of subsequently-executed commands.

false

Does nothing, and exits 1. Used with until for infinite loops.

fg [job ...]

This command is only on systems that support job control. Each job specified is brought to the foreground and waited for in the specified order. Otherwise, the current job is brought into the foreground. See Jobs for a description of the format of job.

getconf [name [pathname]]

Prints the current value of the configuration parameter specified by name. The configuration parameters are defined by the IEEE POSIX 1003.1 and IEEE POSIX 1003.2 standards. See pathconf(2) and sysconf(3C).

The pathname argument is required for parameters whose value depends on the location in the file system. If no arguments are specified, getconf prints the names and values of the current configuration parameters. The pathname / is used for each of the parameters that requires pathname.

getopts [ -a name] optstring vname [arg ...]

Checks arg for legal options. If arg is omitted, the positional parameters are used. An option argument begins with a + or a -. An option that does not begin with + or - or the argument -- ends the options. Options beginning with + are only recognized when optstring begins with a +. optstring contains the letters that getopts recognizes. If a letter is followed by a :, that option is expected to have an argument. The options can be separated from the argument by blanks. The option -?causes getopts to generate a usage message on standard error. The -a option can be used to specify the name to use for the usage message, which defaults to $0. getopts places the next option letter it finds inside variable vname each time it is invoked. The option letter is prepended with a + when arg begins with a +. The index of the next arg is stored in OPTIND. The option argument, if any, gets stored in OPTARG. A leading : in optstring causes getopts to store the letter of an invalid option in OPTARG, and to set vname to ? for an unknown option and to: when a required option argument is missing. Otherwise, getopts prints an error message. The exit status is non-zero when there are no more options. There is no way to specify any of the options :, +, -, ?, [, and ]. The option # can only be specified as the first option.

hist [ -e ename][-nlr] [ first[last ] ]

hist -s [ old=new ] [ command]

In the first form, a range of commands from first to last is selected from the last HISTSIZE commands that were typed at the terminal. The arguments first and last can be specified as a number or as a string. A string is used to locate the most recent command starting with the specified string. A negative number is used as an offset to the current command number. If the -l option is selected, the commands are listed on standard output. Otherwise, the editor program ename is invoked on a file containing these keyboard commands. If ename is not supplied, then the value of the variable HISTEDIT is used. If HISTEDIT is not set, then FCEDIT (default /bin/ed) is used as the editor. When editing is complete, the edited command(s) is executed if the changes have been saved. If last is not specified, then it is set to first. If first is not specified, the default is the previous command for editing and -16 for listing. The option -r reverses the order of the commands and the option -n suppresses command numbers when listing. In the second form, command is interpreted as first described in this section and defaults to the last command executed. The resulting command is executed after the optional substitution old=new is performed.

jobs -lnp [job ...]

Lists information about each specified job, or all active jobs if job is omitted. The -l option lists process ids in addition to the normal information. The -n option only displays jobs that have stopped or exited since last notified. The -p option causes only the process group to be listed. See Jobs for a description of the format of job.

kill [-s signame] job ...
kill [-n signum] job ...
kill -l [sig ...]

Sends either the TERM (terminate) signal or the specified signal to the specified jobs or processes. Signals are either specified by number with the -n option or by name with the -s option (as specified in <signal.h>, stripped of the prefix `SIG with the exception that SIGCLD is named CHLD). For backward compatibility, the n and s can be omitted and the number or name placed immediately after the -. If the signal being sent is TERM (terminate) or HUP (hang up), then the job or process is sent a CONT (continue) signal if it is stopped. The argument job can be the process id of a process that is not a member of one of the active jobs. See Jobs for a description of the format of job. In the third form, kill -l, if sig is not specified, the signal names are listed. Otherwise, for each sig that is a name, the corresponding signal number is listed. For each sig that is a number, the signal name corresponding to the least significant 8 bits of sig is listed.

let [arg ...]

Each arg is a separate arithmetic expression to be evaluated. See the Arithmetic Evaluation section of this manual page for a description of arithmetic expression evaluation. The exit status is 0 if the value of the last expression is non-zero, and 1 otherwise.

+newgrp [arg ...]

Equivalent to exec /bin/newgrp arg ...

print [-Renprs] [ -u unit] [ -f format ] [ arg ...]

With no options or with option - or --, each arg is printed on standard output. The -f option causes the arguments to be printed as described by printf. In this case, any e, n, r, or R options are ignored. Otherwise, unless the -R or -r, are specified, the following escape conventions are applied:

\a

Alert character (ASCII 07)

\b

Backspace character (ASCII 010)

\c

Causes print to end without processing more arguments and not adding a NEWLINE

\f

Form-feed character (ASCII 014)

\n

NEWLINE character (ASCII 012)

\r

RETURN character (ASCII 015)

\t

TAB character (ASCII 011)

\v

Vertical TAB character (ASCII 013)

\E

Escape character (ASCII 033)

\\

Backslash character \

\0x

Character defined by the 1, 2, or 3-digit octal string specified by x

The -R option prints all subsequent arguments and options other than -n. The -e causes the escape conventions to be applied This is the default behavior. It reverses the effect of an earlier -r. The -p option causes the arguments to be written onto the pipe of the process spawned with |& instead of standard output. The -s option causes the arguments to be written onto the history file instead of standard output. The -u option can be used to specify a one digit file descriptor unit number unit on which the output is placed. The default is 1. If the option -n is used, no NEWLINE is added to the output.

printf format[arg ...]

The arguments arg are printed on standard output in accordance with the ANSI-C formatting rules associated with the format string format. If the number of arguments exceeds the number of format specifications, the format string is reused to format remaining arguments. The following extensions can also be used: A %b format can be used instead of %s to cause escape sequences in the corresponding arg to be expanded as described in print. A %B option causes each of the arguments to be treated as variable names and the binary value of the variables is printed. This is most useful for variables with an attribute of b. A %H format can be used instead of %s to cause characters in arg that are special in HTML and XML to be output as their entity name. A %P format can be used instead of %s to cause arg to be interpreted as an extended regular expression and be printed as a shell pattern. A %R format can be used instead of %s to cause arg to be interpreted as a shell pattern and to be printed as an extended regular expression. A %q format can be used instead of %s to cause the resulting string to be quoted in a manner than can be input again to the shell. A %(date-format)T format can be use to treat an argument as a date/time string and to format the date/time according to the date-format as defined for the date(1) command. A %Z format outputs a byte whose value is 0. The precision field of the %d format can be followed by a . and the output base. In this case, the # flag character causes base# to be prepended. The # flag when used with the d specifier without an output base, causes the output to be displayed in thousands units with one of the suffixes k M G T P E to indicate the unit. The # flag when used with the i specifier causes the output to be displayed in 1024 with one of the suffixes Ki Mi Gi Ti Pi Ei to indicate the unit. The = flag has been added to center the output within the specified field width.

pwd [-LP]

Outputs the value of the current working directory. The -L option is the default. It prints the logical name of the current directory. If the -P option is specified, all symbolic links are resolved from the name. The last instance of -L or -P on the command line determines which method is used.

read [-Aprs] [-d delim] [ -n n] [[ -N n] [[-t timeout] [-u unit] [vname?prompt] [ vname ... ]

The shell input mechanism. One line is read and is broken up into fields using the characters in IFS as separators. The escape character, \, is used to remove any special meaning for the next character and for line continuation. The -d option causes the read to continue to the first character of delim rather than NEWLINE. The -n option causes at most n bytes to read rather a full line but returns when reading from a slow device as soon as any characters have been read. The -N option causes exactly n to be read unless an end-of-file has been encountered or the read times out because of the -t option. In raw mode, -r, the \ character is not treated specially. The first field is assigned to the first vname, the second field to the second vname, etc., with leftover fields assigned to the last vname. When vname has the binary attribute and -n or -N is specified, the bytes that are read are stored directly into the variable. If the -v is specified, then the value of the first vname is used as a default value when reading from a terminal device. The -A option causes the variable vname to be unset and each field that is read to be stored in successive elements of the indexed array vname. The -p option causes the input line to be taken from the input pipe of a process spawned by the shell using |&. If the -s option is present, the input is saved as a command in the history file. The option -u can be used to specify a one digit file descriptor unit unit to read from. The file descriptor can be opened with the exec special built-in command. The default value of unit n is 0. The option -t is used to specify a time out in seconds when reading from a terminal or pipe. If vname is omitted, then REPLY is used as the default vname. An end-of-file with the -p option causes cleanup for this process so that another can be spawned. If the first argument contains a ?, the remainder of this word is used as a 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.

++readonly [-p] [ vname[=value]] ...

If vname is not specified, the names and values of each variable with the read-only attribute is printed with the values quoted in a manner that allows them to be input again. The -p option causes the word readonly to be inserted before each one. Otherwise, the specified vnames are marked readonly and these names cannot be changed by subsequent assignment.

+return [n]

Causes a shell function or script to return to the invoking script with the exit status specified by n. The value is the least significant 8 bits of the specified status. If n is omitted, then the return status is that of the last command executed. If return is invoked while not in a function or a script, then it behaves the same as exit.

+set [ ±BCGabefhkmnoprstuvx] [±o [ option ] ] ... [ ±A vname] [arg...]

The set command supports the following options:

-a

All subsequent variables that are defined are automatically exported.

-A

Array assignment. Unset the variable vname and assign values sequentially from the arg list. If +A is used, the variable vname is not unset first.

-b

Prints job completion messages as soon as a background job changes state rather than waiting for the next prompt.

-B

Enable brace pattern field generation. This is the default behavior.

-C

Prevents redirection (>) from truncating existing files. Files that are created are opened with the O_EXCL mode. Requires >| to truncate a file when turned on.

-e

If a command has a non-zero exit status, execute the ERR trap, if set, and exit. This mode is disabled while reading profiles.

-f

Disables file name generation.

-G

Causes the pattern ** by itself to match files and zero or more directories and subdirectories when used for file name generation. If followed by a / only directories and subdirectories are matched.

-h

Each command becomes a tracked alias when first encountered.

-k

Obsolete. All variable assignment arguments are placed in the environment for a command, not just those that precede the command name.

-m

Background jobs run in a separate process group and a line prints 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.

-n

Read commands and check them for syntax errors, but do not execute them. Ignored for interactive shells.

-o

If no option name is supplied, the list of options and their current settings are written to standard output. When invoked with a +, the options are written in a format that can be input again to the shell to restore the settings. This option can be repeated to enable or disable multiple options.

The following argument can be one of the following option names:

allexport

Same as -a.

bgnice

All background jobs are run at a lower priority. This is the default mode.

braceexpand

Same as -B.

emacs

Puts you in an emacs style inline editor for command entry.

errexit

Same as -e.

globstar

Same as -G.

gmacs

Puts you in a gmacs style inline editor for command entry.

ignoreeof

The shell does not exit on end-of-file. The command exit must be used.

keyword

Same as -k.

markdirs

All directory names resulting from file name generation have a trailing / appended.

monitor

Same as -m.

multiline

The built-in editors use multiple lines on the screen for lines that are longer than the width of the screen. This might not work for all terminals.

noclobber

Same as -C.

noexec

Same as -n.

noglob

Same as -f.

nolog

Do not save function definitions in the history file.

notify

Same as -b.

nounset

Same as -u.

pipefail

A pipeline does not complete until all components of the pipeline have completed, and the return value is the value of the last non-zero command to fail or zero if no command has failed.

privileged

Same as -p.

showme

When enabled, simple commands or pipelines preceded by a a semicolon (;) is displayed as if the xtrace option were enabled but is not executed. Otherwise, the leading ; is ignored.

trackall

Same as -h.

verbose

Same as -v.

vi

Puts you in insert mode of a vi style inline editor until you hit the escape character 033. This puts you in control mode. A return sends the line.

viraw

Each character is processed as it is typed in vi mode.

xtrace

Same as -x.

If no option name is supplied, the current options settings are printed.

-p

Disables processing of the $HOME/.profile file and uses the file /etc/suid_profile instead of the 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.

-r

Enables the restricted shell. This option cannot be unset once set.

-s

Sort the positional parameters lexicographically.

-t

Obsolete. Exit after reading and executing one command.

-u

Treat unset parameters as an error when substituting.

-v

Print shell input lines as they are read.

-x

Print commands and their arguments as they are executed.

--

Do not change any of the options. This is useful in setting $1 to a value beginning with -. If no arguments follow this option then the positional parameters are unset.

As an obsolete feature, if the first arg is - then the -x and -v options are turned off and the next arg is treated as the first argument. Using + rather than - causes these options to be turned off. These options can also be used upon invocation of the shell. The current set of options can be found in $-. Unless -A is specified, the remaining arguments are positional parameters and are assigned, in order, to $1 $2 .... If no arguments are specified, then the names and values of all variables are printed on the standard output.

+shift [n]

The positional parameters from $n+1 ... are renamed $1 ..., the default n is 1. The parameter n can be any arithmetic expression that evaluates to a non-negative number less than or equal to $#.

sleep seconds

Suspends execution for the number of decimal seconds or fractions of a second specified by seconds.

+trap -p [action] [sig] ...

The -p option causes the trap action associated with each trap as specified by the arguments to be printed with appropriate quoting. Otherwise, action is processed as if it were an argument to eval when the shell receives signal(s) sig. Each sig can be specified 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 action is omitted and the first sig is a number, or if action is -, then the trap(s) for each sig are reset to their original values. If action is the null string then this signal is ignored by the shell and by the commands it invokes. If sig is ERR then action is executed whenever a command has a non-zero exit status. If sig is DEBUG then action is executed before each command. The variable .sh.command contains the contents of the current command line when action is running. If sig is 0 or EXIT and the trap statement is executed inside the body of a function defined with the function name syntax, then the command action is executed after the function completes. If sig is 0 or EXIT for a trap set outside any function then the command action is executed on exit from the shell. If sig is KEYBD, then action is executed whenever a key is read while in emacs, gmacs, or vi mode. The trap command with no arguments prints a list of commands associated with each signal number.

true

Does nothing, and exits 0. Used with while for infinite loops.

++typeset [±AHflabnprtux ] [ ±EFLRZi[n] ] [ vname[=value ] ]

Sets attributes and values for shell variables and functions. When invoked inside a function defined with the function name syntax, a new instance of the variable vname is created, and the variable's value and type are restored when the function completes.

Using + rather than - causes these options to be turned off. If no vname arguments are specified, a list of vnames (and optionally the values) of the variables is printed. Using + rather than - keeps the values from being printed.) The -p option causes typeset followed by the option letters to be printed before each name rather than the names of the options. If any option other than -p is specified, only those variables which have all of the specified options are printed. Otherwise, the vnames and attributes of all variables that have attributes are printed.

The following list of attributes can be specified:

-a

Declares vname to be an indexed array. This is optional unless except for compound variable assignments.

-A

Declares vname to be an associative array. Sub-scripts are strings rather than arithmetic expressions.

-b

The variable can hold any number of bytes of data. The data can be text or binary. The value is represented by the base64 encoding of the data. If -Z is also specified, the size in bytes of the data in the buffer is determined by the size associated with the -Z. If the base64 string assigned results in more data, it is truncated. Otherwise, it is filled with bytes whose value is zero. The printf format %B can be used to output the actual data in this buffer instead of the base64 encoding of the data.

-E

Declares vname to be a double precision floating point number. If n is non-zero, it defines the number of significant figures that are used when expanding vname. Otherwise, ten significant figures is used.

-f

The names refer to function names rather than variable names. No assignments can be made and the only other valid options are -t, -u, and -x. The -t option turns on execution tracing for this function. The -u option causes this function to be marked undefined. The FPATH variable is searched to find the function definition when the function is referenced. If no options other than -f is specified, then the function definition is displayed on standard output. If +f is specified, then a line containing the function name followed by a shell comment containing the line number and path name of the file where this function was defined, if any, is displayed.

The -i attribute cannot be specified with -f.

-F

Declares vname to be a double precision floating point number. If n is non-zero, it defines the number of places after the decimal point that are used when expanding vname. Otherwise ten places after the decimal point is used.

-H

This option provides UNIX to hostname file mapping on non-UNIX machines.

-i

Declares 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 n is non-zero, it defines the output arithmetic base, otherwise the output base is ten.

The -i attribute cannot be specified along with -R, -L, -Z, or -f.

-l

All uppercase characters are converted to lowercase. The uppercase option, -u, is turned off.

-L

Left justify and remove leading blanks from value. If 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 -R option is turned off.

The -i attribute cannot be specified with -L.

-n

Declares vname to be a reference to the variable whose name is defined by the value of variable vname. This is usually used to reference a variable inside a function whose name has been passed as an argument.

-R

Right justify and fill with leading blanks. If 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 -L option is turned off.

The -i attribute cannot be specified with -R.

-r

The specified vnames are marked read-only and these names cannot be changed by subsequent assignment.

-t

Tags the variables. Tags are user definable and have no special meaning to the shell.

-u

All lowercase characters are converted to uppercase. The lowercase option, -l, is turned off.

-x

The specified vnames are marked for automatic export to the environment of subsequently-executed commands. Variables whose names contain a . cannot be exported.

-Z

Right justify and fill with leading zeros if the first non-blank character is a digit and the -L option has not been set. Remove leading zeros if the -L option is also set. If 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 -i attribute cannot be specified with -Z.

ulimit [-HSacdfmnpstv] [ limit]

Set or display a resource limit. Many systems do not support one or more of these limits. The limit for a specified resource is set when limit is specified. The value of limit can be a number in the unit specified with each resource, or the value unlimited. When more than one resource is specified, then the limit name and unit is printed before the value.

If no option is specified, -f is assumed.

The following are the available resource limits:

-a

Lists all of the current resource limits.

-c

The number of 512-byte blocks on the size of core dumps.

-d

The number of Kbytes on the size of the data area.

-f

The number of 512-byte blocks on files that can be written by the current process or by child processes (files of any size can be read).

-H

Specifies a hard limit for the specified resource.

A hard limit cannot be increased once it is set.

If neither the -H nor -S option is specified, the limit applies to both. The current resource limit is printed when limit is omitted. In this case, the soft limit is printed unless -H is specified.

-m

The number of Kbytes on the size of physical memory.

-n

The number of file descriptors plus 1.

-p

The number of 512-byte blocks for pipe buffering.

-s

The number of Kbytes on the size of the stack area.

-S

Specifies a soft limit for the specified resource.

A soft limit can be increased up to the value of the hard limit.

If neither the -H nor -S option is specified, the limit applies to both. The current resource limit is printed when limit is omitted. In this case, the soft limit is printed unless -H is specified.

-t

The number of CPU seconds to be used by each process.

-v

The number of Kbytes for virtual memory.

umask [-S][mask]

The user file-creation mask is set to mask. mask can either be an octal number or a symbolic value as described in chmod(1).

If a symbolic value is specified, the new umask value is the complement of the result of applying mask to the complement of the previous umask value. If mask is omitted, the current value of the mask is printed. The -S option causes the mode to be printed as a symbolic value. Otherwise, the mask is printed in octal.

See umask(2)

+unalias [-a] name

The aliases specified by the list of names are removed from the alias list. The -a option causes all the aliases to be unset.

+unset [-fnv] vname

The variables specified by the list of vnames are unassigned, i.e., their values and attributes are erased. Read-only variables cannot be unset. If the -f option is set, then the names refer to function names. If the -v option is set, then the names refer to variable names. The -f option overrides -v. If -n is set and name is a name reference, then name is unset rather than the variable that it references. The default is equivalent to -v. Unsetting LINENO, MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their special meaning even if they are subsequently assigned to.

wait [job]

Wait for the specified job and report its termination status. If job is not specified, then all currently active child processes are waited for. The exit status from this command is that of the last process waited for if job is specified; otherwise it is zero. See Jobs for a description of the format of job.

whence [-afpv] name ...

For each name, indicate how it would be interpreted if used as a command name. The -v option produces a more verbose report. The -f option skips the search for functions. The -p option does a path search for name even if name is an alias, a function, or a reserved word. The -a option is similar to the -v option but causes all interpretations of the specified name to be reported.

Invocation

If the shell is invoked by exec(2), and the first character of argument zero ($0) is -, then the shell is assumed to be a login shell and commands are read from /etc/profile and then from either .profile in the current directory or $HOME/.profile, if either file exists. Next, for interactive shells, commands are read first from /etc/ksh.kshrc, and then from the file named by performing parameter expansion, command substitution, and arithmetic substitution on the value of the environment variable ENV if the file exists. If the -s option is not present and arg and a file by the name of arg exists, then it reads and executes this script. Otherwise, if the first arg does not contain a /, a path search is performed on the first arg to determine the name of the script to execute. The script arg must have execute permission and any setuid and setgid settings are ignored. If the script is not found on the path, arg is processed as if it named a built-in command or function.

Commands are then read as described, and the following options are interpreted by the shell when it is invoked:

-c

If the -c option is present, then commands are read from the first arg. Any remaining arguments become positional parameters starting at 0.

-D

A list of all double quoted strings that are preceded by a $ is printed on standard output and the shell exits. This set of strings is subject to language translation when the locale is not C or POSIX. No commands are executed.

-i

If the -i option is present or if the shell input and output are attached to a terminal (as told by tcgetattr(3C), this shell is interactive. In this case TERM is ignored (so that kill 0 does not kill an interactive shell) and INTR is caught and ignored (so that wait is interruptible). In all cases, QUIT is ignored by the shell.

-R filename

The -R 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.

-r

If the -r option is present, the shell is a restricted shell.

-s

If the -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 Special Commands listed, is written to file descriptor 2.

The remaining options and arguments are described under the set command. An optional - as the first argument is ignored.

rksh93 Only

rksh93 is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell.

The actions of rksh93 are identical to those of ksh93, except that the following are disallowed:

• Unsetting the restricted option

• Changing directory. See cd(1).

• Setting or unsetting the value or attributes of SHELL, ENV, FPATH, or PATH

• Specifying path or command names containing /,

• Redirecting output (>, >|, <>, and >>).

• Adding or deleting built-in commands.

• Using command -p to invoke a command.

These restrictions are enforced after .profile and the ENV files are interpreted.

When a command to be executed is found to be a shell procedure, rksh93 invokes ksh93 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. The net effect of these rules is that the writer of the .profile has complete control over user actions, by performing guaranteed setup actions and leaving the user in an appropriate directory (probably not the login directory). The system administrator often sets up a directory of commands, for example, /usr/rbin, that can be safely invoked by rksh.

Usage

See largefile(5) for the description of the behavior of ksh93 and rksh93 when encountering files greater than or equal to 2 Gbyte ( 2³¹ bytes).

Exit Status

The following exit values are returned:

non-zero

Returns non-zero when errors, such as syntax errors, are detected by the shell.

If the shell is being used non-interactively, then execution of the shell file is abandoned unless the error occurs inside a sub-shell in which case the sub-shell is abandoned.

exit status of last command executed

Returns the exit status of the last command executed.

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 ([]) after the command or function name.

See the ksh93 exit command for additional details.

Files

/etc/profile

The system initialization file, executed for login shells.

/etc/ksh.kshrc

The system wide startup file, executed for interactive shells.

$HOME/.profile

The personal initialization file, executed for login shells after /etc/profile.

$HOME/.kshrc

Default personal initialization file, executed after /etc/ksh.kshrc, for interactive shells when ENV is not set.

/etc/suid-profile

Alternative initialization file, executed instead of the personal initialization file when the real and effective user or group id do not match.

/dev/null

NULL device.

Authors

David Korn, dgk@research.att.com

Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Availability	SUNWcsu
Interface Stability	See below.

The scripting interface is Uncommitted. The environment variables, .paths feature, and editing modes are Volatile.

See Also

cat(1), cd(1), chmod(1), cut(1), date(1), egrep(1), echo(1), egrep(1), env(1), fgrep(1), grep(1), login(1), newgrp(1), paste(1), printf(1), stty(1), test(1), umask(1), vi(1), dup(2), exec(2), fork(2), ioctl(2), lseek(2), pathconf(2), pipe(2), sysconf(3C), ulimit(2), umask(2), rand(3C)tcgetattr(3C), wait(3C), a.out(4), profile(4), attributes(5), environ(5), largefile(5), standards(5)

Bolsky, Morris I. and Korn, David G., The New KornShell Command and Programming Language, Prentice Hall, 1995.

POSIX-Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.

Notes

ksh93 scripts should choose shell function names outside the namespace used by reserved keywords of the ISO C99, C++ and JAVA languages to avoid collisions with future enhancements to ksh93.

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 continues to exec the original command. Use the -t option of the alias command to correct this situation.

Some very old shell scripts contain a caret (^) as a synonym for the pipe character (|).

Using the hist built-in command within a compound command causes the whole command to disappear from the history file.

The built-in command . file reads the whole file before any commands are executed. alias and unalias commands in the file do not apply to any commands defined in the file.

Traps are not processed while a job is waiting for a foreground process. Thus, a trap on CHLD is not executed until the foreground job terminates.

It is a good idea to leave a space after the comma operator in arithmetic expressions to prevent the comma from being interpreted as the decimal point character in certain locales.

There might be some restrictions on creating a .paths file which is portable across other operating systems.

If the system supports the 64-bit instruction set, /bin/ksh93 executes the 64-bit version of ksh93.

SunOS 5.11  Last Revised 11 Aug sam2009

Name | Synopsis | Description | Usage | Exit Status | Files | Authors | Attributes | See Also | Notes