Ksh93 (1) Linux Manual Page

NAME

ksh, rksh, pfksh – KornShell, a standard/restricted command and programming language

SYNOPSIS

ksh [ ±abcefhiknoprstuvxBCDP ] [ -R file ] [ ±o option ] … [ – ] [ arg … ]

DESCRIPTION

Ksh is a command and programming language that executes commands read from a terminal or a file. Rksh is a restricted version of the command interpreter ksh; it is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell. Rpfksh is a profile shell version of the command interpreter ksh; it is used to to execute commands with the attributes specified by the user’s profiles (see pfexec(1)). See Invocation below for the meaning of arguments to the shell.

Definitions.

A metacharacter is one of the following characters:

: ; & ( ) | < > new-line 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 . and optionally preceded by a .. 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 here. Built-ins that cause side effects in the shell environment and built-ins that are found before performing a path search (see Execution below) are documented here. 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 below) or a sequence of blank separated words which may be preceded by a list of variable assignments (see Environment below). The first word specifies the name of the command to be executed. Except as specified below, the remaining words are passed as arguments to the invoked command. The command name is passed as argument 0 (see exec(2)). The value of a simple-command is its exit status; 0-255 if it terminates normally; 256+signum if it terminates abnormally (the name of the signal corresponding to the exit status can be obtained via 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 ! which 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 (i.e., 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 described later. The symbol && (||) causes the list following it to be executed only if the preceding pipeline returns a zero (non-zero) value. One or more new-lines may 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 below.

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

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, then the for command executes the do list once for each positional parameter that is set starting from 1 (see Parameter Expansion below). Execution ends when there are no more words in the list.
for (( expr1] ; expr2] ; expr3] )) ;do list ;done: The arithmetic expression expr1 is evaluated first (see Arithmetic evaluation below). 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.
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, then the positional parameters starting from 1 are used instead (see Parameter Expansion below). 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 end-of-file is encountered. If the REPLY variable is set to null by the execution of list, then 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 below). 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 may be used in place of while to negate the loop termination test.
((expression)): The expression is evaluated using the rules for arithmetic evaluation described below. 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. Note, that if two adjacent open parentheses are needed for nesting, a space must be inserted to avoid evaluation as an arithmetic command as described above.
{ list;}: list is simply executed. Note that unlike the metacharacters ( and ), { and } are reserved words and must occur at the beginning of a line or after a ; in order to be recognized.
[[ expression ]]: Evaluates expression and returns a zero exit status when expression is true. See Conditional Expressions below, 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 below.)
namespace identifier { list ;}: Defines or uses the name space identifier and runs the commands in list in this name space. (See Name Spaces below.)
& name arg… ] ]: Causes subsequent list commands terminated by & to be placed in the background job pool name. If name is omitted a default unnamed pool is used. Commands in a named background pool may be executed remotely.
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 may be set to a format string that specifies how the timing information should be displayed. See Shell Variables below 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:

if then else elif fi case esac for while until do done { } function select time [[ ]] !

Variable Assignments.

One or more variable assignments can start a simple command or can be arguments to the typeset, enum, export, or readonly special built-in commands as well as to other declaration commands created as types. 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=(assign_list)

No space is permitted between varname and the =. The variable varname is unset before the assignment. An assign_list can be one of the following:

word …: Indexed array assignment.
[word]=word …: Associative array assignment. If preceded by typeset -a this will create 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 will contain all the assignment elements. Additional assignments made to sub-variables of varname will also be displayed as part of the value of varname. If no assignments are specified, varname will be 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. Other declaration commands such as readonly, enum, and other declaration commands can be used in place of typeset.
. filename: Include the assignment commands contained in filename.

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.

The right hand side of a variable assignment undergoes all the expansion listed below except word splitting, brace expansion, and file name generation. When the left hand side is an assignment is a compound variable and the right hand is the name of a compound variable, the compound variable on the right will be copied or appended to the compound variable on the left.

Comments.

A word beginning with # causes that word and all the following characters up to a new-line to be 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 and command substitution characters, the characters / and =. The replacement string can contain any valid shell script including the metacharacters listed above. The first word of each command in the replaced text, other than any that are in the process of being replaced, will be tested for aliases. If the last character of the alias value is a blank then the word following the alias will also be checked for alias substitution. Aliases can be used to redefine built-in commands but cannot be used to redefine the reserved words listed above. Aliases can be created and listed with the alias command and can be removed with the unalias command.

Aliasing is performed when scripts are read, not while they are executed. Therefore, 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 ´
compound=´typeset -C´
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 ≈. For tilde substitution, word also refers to the word portion of parameter expansion (see Parameter Expansion below). If it does, then the word up to a / is checked to see if it matches a user name in the password database (See getpwname(3).) 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 :. The : also terminates a ≈ login name.

Command Substitution.

The standard output from a command list enclosed in parentheses preceded by a dollar sign ( $(list) ), or in a brace group preceded by a dollar sign ( ${ list;} ), or in a pair of grave accents (``) may be used as part or all of a word; trailing new-lines are removed. In the second case, the { and } are treated as a reserved words so that { must be followed by a blank and } must appear at the beginning of the line or follow a ;. In the third (obsolete) form, the string between the quotes is processed for special quoting characters before the command is executed (see Quoting below). The command substitution $(cat file) can be replaced by the equivalent but faster $(<file). The command substitution $(n<#) will expand to the current byte offset for file descriptor n. Except for the second form, the command list is run in a subshell so that no side effects are possible. For the second form, the final } will be recognized as a reserved word after any token.

Arithmetic Substitution.

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

Process Substitution.

Each command argument of the form <(list) or >(list) will run process list asynchronously connected to some file in /dev/fd if this directory exists, or else a fifo a temporary directory. The name of this file will become the argument to the command. If the form with > is selected then writing on this file will provide input for list. If < is used, then the file passed as an argument will contain 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, as well as putting it onto the standard output. Note that the file, which is passed as an argument to the command, is a UNIX pipe(2) so programs that expect to lseek(2) on the file will not work.

Process substitution of the form <(list) can also be used with the < redirection operator which causes the output of list to be standard input or the input for whatever file descriptor is specified.

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 below) between a [ and a ]. To assign values to an indexed array, use vname=(value …) or set -A vname value … . The value of all non-negative subscripts must be in the range of 0 through 4,194,303. A negative subscript is treated as an offset from the maximum current index +1 so that -1 refers to the last element. Indexed arrays can be declared with the -a option to typeset. Indexed arrays need not be declared. Any reference to a variable with a valid subscript is legal and an array will be created if necessary.

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 may be assigned by writing:

: vname=value vname=value ] …

: vname[subscript]=value vname[subscript]=value ] …

Note that no space is allowed before or after the =.

Attributes assigned by the typeset special built-in command apply to all elements of the array. An array element can be a simple variable, a compound variable or an array variable. An element of an indexed array can be either an indexed array or an associative array. An element of an associative array can also be either. To refer to an array element that is part of an array element, concatenate the subscript in brackets. For example, to refer to the foobar element of an associative array that is defined as the third element of the indexed array, use ${vname[3][foobar]}

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 will be referenced whenever the nameref variable is used. The name of a nameref cannot contain a .. 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 any of the floating point attributes, -E, -F, or -X, or the integer attribute, -i, is set for vname, then the value is subject to arithmetic evaluation as described below.

Positional parameters, parameters denoted by a number, may 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 .. The braces are also required when a variable is subscripted unless it is part of an Arithmetic Expression or a Conditional Expression. 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 (separated by a field separator character). If an array vname with last subscript * @, or for index arrays of the form sub1 .. sub2. is used, then the value for each of the elements between sub1 and sub2 inclusive (or all elements for * and @) 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 type name (See Type Variables below) or attributes of the variable referred to by vname.
${!vname}: Expands to the name of the variable referred to by vname. This will be vname except when vname is a name reference.
${!vname[subscript]}: Expands to name of the subscript unless subscript is *, @. or of the form sub1 .. sub2. 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 @, same as above, except that when used in double quotes, each array subscript yields a separate argument. When subscript is of the form sub1 .. sub2 it expands to the list of subscripts between sub1 and sub2 inclusive using the same quoting rules as @.
${!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.
${parameter:=word}: If parameter is not set or is null then set it to word; the value of the parameter is then substituted. Positional parameters may not be assigned to in this way.
${parameter:?word}: If parameter is set and is non-null then substitute its value; otherwise, print word and exit from the shell (if not interactive). If word is omitted then a standard message is printed.
${parameter:+word}: If parameter is set and is non-null then substitute word; otherwise substitute nothing.

In the above, word is not evaluated unless it is to be used as the substituted string, so that, 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 above expressions, then 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. If A negative offset counts backwards from the end of parameter. Note that 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 associate 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 given string. Each occurrence of \n in string is replaced by the portion of parameter that matches the n-th sub-pattern. In the first form, only the first occurrence of pattern is replaced. In the second form, each match for pattern is replaced by the given string. The third form restricts the pattern match to the beginning of the string while the fourth form restricts the pattern match to the end of the string. When string is null, the pattern will be deleted and the / in front of string may 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 will be re-evaluated for each element.

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 an absolute pathname of the shell or script being executed as passed in the environment. Subsequently it is assigned the last argument of the previous command. This parameter is not set for commands which are asynchronous. This parameter is also used to hold the name of the matching MAIL file when checking for mail. While defining a compound variable or a type, _ is initialized as a reference to the compound variable or type. When a discipline function is invoked, _ is initialized as a reference to the variable associated with the call to this function. Finally when _ is used as the name of the first variable of a type definition, the new type is derived from the type of the first variable (See Type Variables below.).
!: The process id or the pool name and job number of the last background command invoked or the most recent job put in the background with the bg built-in command. Background jobs started in a named pool will be in the form pool.number where pool is the pool name and number is the job number within that pool.
.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 (see Key Bindings below). 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.
.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. (See Vi Editing Mode below.) Otherwise, .sh.edmode is null when processing a KEYBD trap.
.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.level: Set to the current function depth. This can be changed inside a DEBUG trap and will set the context to the specified level.
.sh.lineno: Set during a DEBUG trap to the line number for the caller of each function.
.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 0-th element stores the complete match and the i-th. element stores the i-th submatch. The .sh.match variable becomes unset when the variable that has expanded is assigned a new value.
.sh.math: Used for defining arithmetic functions (see Arithmetic evaluation below). and stores the list of user defined arithmetic functions.
.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 subshells and command substitution.
.sh.value: Set to the value of the variable at the time that the set or append discipline function is invoked. When a user defined arithmetic function is invoked, the value of .sh.value is saved and .sh.value is set to long double precision floating point. .sh.value is restored when the function returns.
.sh.version: Set to a value that identifies the version of this shell.
KSH_VERSION: A name reference to .sh.version.
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 will be the value that was assigned plus the number of seconds since the assignment.
SHLVL: An integer variable the is incremented each time the shell is invoked and is exported. If SHLVL is not in the environment when the shell is invoked, it is set to 1.

The following variables are used by the shell:

CDPATH

The search path for the cd command.

COLUMNS

If this variable is set, the value is used to define the width of the edit window for the shell edit modes and for printing select lists.

EDITOR

If the VISUAL variable is not set, the value of this variable will be checked for the patterns as described with VISUAL below and the corresponding editing option (see Special Command set below) will be turned on.

ENV

If this variable is set, then parameter expansion, command substitution, and arithmetic substitution are performed on the value to generate the pathname of the script that will be executed when the shell is invoked interactively (see Invocation below). This file is typically used for alias and function definitions. The default value is $HOME/.kshrc. On systems that support a system wide /etc/ksh.kshrc initialization file, if the filename generated by the expansion of ENV begins with /./ or ././ the system wide initialization file will not be executed.

FCEDIT

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

FIGNORE

A pattern that defines the set of filenames that will be ignored when performing filename 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 . rather than by adjacent : characters or a beginning or ending :.

HISTCMD

Number of the current command in the history file.

HISTEDIT

Name for the default editor name for the hist command.

HISTFILE

If this variable is set when the shell is invoked, then the value is the pathname of the file that will be used to store the command history (see Command Re-entry below).

HISTSIZE

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

HOME

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

IFS

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

JOBMAX

This variable defines the maximum number running background jobs that can run at a time. When this limit is reached, the shell will wait for a job to complete before staring a new job.

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 File Name Generation below).

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 will print 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.

MAILCHECK

This variable specifies how often (in seconds) the shell will check for changes in the modification time of any of the files specified by the MAILPATH or MAIL variables. The default value is 600 seconds. When the time has elapsed the shell will check before issuing the next prompt.

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 will be printed. The message will undergo 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 (see Execution below). The user may not change PATH if executing under rksh (except in .profile).

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 (see Command Re-entry below). Two successive occurrences of ! will produce a single ! when the prompt string is printed.

PS2

Secondary prompt string, by default “> ”.

PS3

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

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 “+ ”. In addition when PS4 is unset, the execution trace prompt is also “+ ”.

SHELL

The pathname of the shell is kept in the environment. At invocation, if the basename of this variable is rsh, rksh, or krsh, then the shell becomes restricted. If it is pfsh or pfksh, then the shell becomes a profile shell (see pfexec(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 brackets 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	%2lR

user	%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 will be the default timeout value for the read built-in command. The select compound command terminates after TMOUT seconds when input is from a terminal. Otherwise, the shell will terminate if a line is not entered within the prescribed number of seconds while reading from a terminal. (Note that the shell can be compiled with a maximum bound for this value which cannot be exceeded.)

VISUAL

If the value of this variable matches the pattern *[Vv][Ii]*, then the vi option (see Special Command set below) is turned on. If the value matches the pattern *gmacs* , the gmacs option is turned on. If the value matches the pattern *macs*, then the emacs option will be turned on. The value of VISUAL overrides the value of EDITOR.

The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK, FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set at all by the shell (although HOME is set by login(1)). On some systems MAIL and SHELL are also set by login(1).

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 then each of the fields resulting from IFS are checked to see if they contain one or more of the 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 seconds 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 thru l2.

In the remaining forms, a field is created for each number starting at n1 and continuing until it reaches n2 incrementing n1 by n3. The cases where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 otherwise. If 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 filename is left unchanged unless the pattern is prefixed with ≈(N) in which case it is removed as described below. 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 filenames. The names . and .. are also ignored. If FIGNORE is not set, the character . at the start of each file name component will be ignored unless the first character of the pattern corresponding to this component is the character . itself. Note, that for other uses of pattern matching the / and . are not treated specially.

*: Matches any string, including the null string. When used for filename expansion, if the globstar option is on, two adjacent *‘s by itself will match all files and zero or more directories and subdirectories. If followed by a / then only directories and subdirectories will match.
?: Matches any single character.
…]: Matches 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 ! or ^ then 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: (Note that word is equivalent to alnum plus the character _.)
alnum alpha blank cntrl digit graph lower print punct space upper word xdigit
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 a & or |. A & 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 given patterns.
*(pattern-list): Matches zero or more occurrences of the given patterns.
+(pattern-list): Matches one or more occurrences of the given patterns.
{n}(pattern-list): Matches n occurrences of the given patterns.
{m,n}(pattern-list): Matches from m to n occurrences of the given patterns. If m is omitted, 0 will be used. If n is omitted at least m occurrences will be matched.
@(pattern-list): Matches exactly one of the given patterns.
!(pattern-list): Matches anything except one of the given patterns.

By default, each pattern, or sub-pattern will match 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 will be chosen. However, for each of the above 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-pair(s)) 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 will be skipped over when counting starting and ending character matches. The behavior is unspecified when the first character of a pattern-pair is alpha-numeric 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.

Thus, %({}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 n-th. sub-pattern, matches the same string as the sub-pattern itself.

Finally 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. :pattern-list must be omitted for options F, G, N , and V below. 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: The remainder of the pattern uses basic regular expression syntax like the grep(1) command.
K: The remainder of the pattern uses shell pattern syntax. This is the default.
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.
X: The remainder of the pattern uses augmented regular expression syntax like the xgrep(1) command.
P: The remainder of the pattern uses perl(1) regular expression syntax. Not all perl regular expression syntax is currently implemented.
V: The remainder of the pattern uses System V regular expression syntax.
i: Treat the match as case insensitive.
g: File the longest match (greedy). This is the default.
l: Left anchor the pattern. This is the default for K style patterns.
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 earlier (see Definitions above) has a special meaning to the shell and causes termination of a word unless quoted. A character may be quoted (i.e., made to stand for itself) by preceding it with a \. The pair ew-line 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:

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