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KSH(1) KSH(1)
NAME
ksh, rksh, pfksh - KornShell, a standard/restricted command and programming lan-
guage
SYNOPSIS
[ ?abcefhiknoprstuvxBCDP ] [ -R file ] [ ?o option ] ... [ - ] [ arg ... ]
DESCRIPTION
Ksh is a command and programming language that executes commands read from a termi-
nal 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 compo-
nents of variable names. A vname is a sequence of one or more identifiers sepa-
rated by a . and optionally preceded by a .. Vnames are used as function and vari-
able 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 spe-
cial 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 com-
mand 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 corre-
sponding 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 out-
put 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 redi-
rection 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 semi-
colon, 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 occuring within a
while, until, or if list, can be prededed 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 evalua-
tion 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 Expan-
sion 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. Other-
wise 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 selec-
tion list is printed before displaying the PS3 prompt for the next selec-
tion.
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 sub-
sequent 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 evalu-
ation 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 . spe-
cial built-in command to get the equivalent behavior as if the varname()
syntax were used to define it. (See Functions below.)
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, 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=(assign_list)
No space is permitted between varname and the =. 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 vari-
able 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.
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
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, 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 can-
not 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. There-
fore, 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 ~. 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 enclosed in parentheses preceded by a dollar
sign ( $() ) or a pair of grave accents (``) may be used as part or all of a word;
trailing new-lines are removed. In the second (obsolete) form, the string between
the quotes is processed for special quoting characters before the command is exe-
cuted (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.
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.
This feature is only available on versions of the UNIX operating system that sup-
port the /dev/fd directory for naming open files. Each command argument of the
form <(list) or >(list) will run process list asynchronously connected to some file
in /dev/fd. 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.
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 environ-
ment.
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 set -A vname value ... . The value of
all subscripts must be in the range of 0 through 1,048,575. 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 ] ...
or
vname[subscript]=value [ vname[subscript]=value ] ...
Note that no space is allowed before or after the =.
A nameref is a variable that is a reference to another variable. A nameref is cre-
ated 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 vari-
able 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 vari-
able 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 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 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 will be
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 @, same as above, except that when used in dou-
ble 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.
${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 substi-
tute 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 param-
eter. 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 pat-
tern 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 pat-
tern will be deleted and the / in front of string may be omitted. When
parameter is @, *, or an array variable with subscript @ or *, the substitu-
tion 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 parame-
ter 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 com-
mand 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.match
An indexed array which stores the most recent match and sub-pattern
matches after conditional pattern matches that match and after vari-
ables expansions using the operators #, %, or /. The 0-th element
stores the complete match and the i-th. element stores the i-th sub-
match. The .sh.match variable becomes 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 func-
tion is invoked.
.sh.subscript
Set to the name subscript of the variable at the time that a disci-
pline 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.
.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 ran-
dom numbers can be initialized by assigning a numeric value to RAN-
DOM.
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.
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 cor-
responding editing option (see Special Command set below) will be
turned on.
ENV If this variable is set, then parameter expansion, command substitu-
tion, and arithmetic substitution are performed on the value to gen-
erate the pathname of the script that will be executed when the shell
is invoked (see Invocation below). This file is typically used for
alias and function definitions. The default value is $HOME/.kshrc.
FCEDIT Obsolete name for the default editor name for the hist command.
FCEDIT is not used when HISTEDIT is set.
FIGNORE
A pattern that defines the set of filenames that will be ignored when
performing filename matching.
FPATH The search path for function definitions. The directories in this
path are searched for a file with the same name as the function or
command when a function with the -u attribute is referenced and when
a command is not found. If an executable file with the name of that
command is found, then it is read and executed in the current envi-
ronment. Unlike PATH, the current directory must be represented
explictily by . rather than by adjacent : characters or a beginning
or ending :.
HISTCMD
Number of the current command in the history file.
HISTEDIT
Name for the default editor name for the hist command.
HISTFILE
If this variable is set when the shell is invoked, then the value is
the pathname of the file that will be used to store the command his-
tory (see Command Re-entry below).
HISTSIZE
If this variable is set when the shell is invoked, then the number of
previously entered commands that are accessible by this shell will be
greater than or equal to this number. The default is 512.
HOME The default argument (home directory) for the cd command.
IFS Internal field separators, normally space, tab, and new-line that are
used to separate the results of command substitution or parameter
expansion and to separate fields with the built-in command read. The
first character of the IFS variable is used to separate arguments for
the "$*" substitution (see Quoting below). Each single occurrence of
an IFS character in the string to be split, that is not in the iss-
pace 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 iss-
pace class, so that if IFS consists of two tab characters, then two
adjacent tab characters delimit a null field.
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 $_.
PATH The search path for commands (see Execution below). The user may not
change PATH if executing under rksh (except in .profile).
PS1 The value of this variable is expanded for parameter expansion, com-
mand substitution, and arithmetic substitution to define the primary
prompt string which by default is ''$''. 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, com-
mand 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 braces denote optional portions. The optional p is a digit spec-
ifying the precision, the number of fractional digits after a decimal
point. A value of 0 causes no decimal point or fraction to be out-
put. 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,
$'\nreal\t%2lR\nuser\t%2lU\nsys%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 time-
out value for the read built-in command. The select compound command
terminates after TMOUT seconds when input is from a terminal. Other-
wise, 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 con-
tinuing until it reaches n2 incrementing n1 by n3. The cases where n3 is not spec-
ified 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 charac-
ter is replaced with a lexicographically sorted set of names that matches the pat-
tern 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 file-
name expansion, if the globstar option is on, two adjacent *'s by
itself will match all files and zero or more directories and subdi-
rectories. If followed by a / then only directories and subdirecto-
ries 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 !
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 omit-
ted, 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 follow-
ing 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. 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.
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
i Treat the match as case insensitive.
g File the longest match (greedy). This is the default.
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
\new-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:
\0 Causes the remainder of the string to be ignored.
\E Equivalent to the escape character (ascii 033),
\e Equivalent to the escape character (ascii 033),
\cx Expands to the character control-x.
\C[.name.]
Expands to the collating element name.
Inside double quote marks (""), parameter and command substitution occur and \
quotes the characters \, `, ", and $. A $ in front of a double quoted string will
be ignored in the "C" or "POSIX" locale, and may 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 com-
mand names listed below 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. 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. In
addition 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 above 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 expo-
nentiation. It has higher precedence than multiplication and is left associative.
In addition, when the value of an arithmetic variable or sub-expression can be rep-
resented 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 com-
mand. The -E option causes the expansion of the value to be represented using sci-
entific notation when it is expanded. The optional option argument n defines the
number of significant figures. The -F option causes the expansion to be repre-
sented as a floating decimal number when it is expanded. The optional option argu-
ment 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 will be used.
Arithmetic evaluation is performed on the value of each assignment to a variable
with the -E, -F, or -i attribute. 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
new-line is typed and further input is needed to complete a command, then the sec-
ondary prompt (i.e., 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:
string True, if string is not null.
-a file
Same as -e below. This 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.
-k file
True, if file exists and it has its sticky bit set.
-n string
True, if length of string is non-zero.
-o ?option
True, if option named option is a valid option name.
-o option
True, if option named option is on.
-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.
-t fildes
True, if file descriptor number fildes is open and associated with a termi-
nal 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.
-L file
True, if file exists and is a symbolic link.
-h file
True, if file exists and is a symbolic link.
-N file
True, if file exists and the modification time is greater than the last
access time.
-O file
True, if file exists and is owned by the effective user id of this process.
-G file
True, if file exists and its group matches the effective group id of this
process.
-S file
True, if file exists and is a socket.
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.
file1 -ef file2
True, if file1 and file2 exist and refer to the same file.
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 a pattern, the
.sh.match array variable will contain the match and sub-pattern matches.
string = pattern
Same as == above, but is obsolete.
string != pattern
True, if string does not match pattern. When the string matches the pattern
the .sh.match array variable will contain 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 charac-
ters.
string1 > string2
True, if string1 comes after string2 based on ASCII value of their charac-
ters.
The following obsolete arithmetic comparisons are also permitted:
exp1 -eq exp2
True, if exp1 is equal to exp2.
exp1 -ne exp2
True, if exp1 is not equal to exp2.
exp1 -lt exp2
True, if exp1 is less than 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 -ge exp2
True, if exp1 is greater than or equal to exp2.
In each of the above expressions, if file is of the form /dev/fd/n, where n is an
integer, then the test is applied to the open file whose descriptor number is n.
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/Output.
Before a command is executed, its input and output may be redirected using a spe-
cial notation interpreted by the shell. The following may appear anywhere in a
simple-command or may precede or follow a command and are not passed on to the
invoked command. Command substitution, parameter expansion, and arithmetic substi-
tution occur before word or digit is used except as noted below. File name genera-
tion 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 given 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 trun-
cated to zero length.
>|word Sames 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 substitu-
tion, and arithmetic substitution occur, \new-line 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 docu-
ment. If # is appended to <<, then leading spaces and tabs will be
stripped off the first line of the document and up to an equivalent
indentation will be stripped from the remaining lines and from word.
A tab stop is assumend 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 substitu-
tion, and arithmetic substitution occur.
<&digit The standard input is duplicated from file descriptor digit (see
dup(2)). Similarly for the standard output using >&digit.
<&digit- The file descriptor given by digit is moved to standard input. Simi-
larly 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.
>#((offset)) The same as <# except applies to file descriptor 1.
<#pattern Seeks 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 above 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 above, other than >&- and the ># and <# forms, is
preceded by {varname} with no intervening space, then a file descriptor number > 10
will be 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 descrip-
tor 1 and
exec {n}<file
means open file named 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 (i.e. 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, then the default stan-
dard 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/output specifications.
Environment.
The environment (see environ(7)) is a list of name-value pairs that is passed to an
executed program in the same way as a normal argument list. The names must be
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 environ-
ment seen by any executed command is thus composed of any name-value pairs origi-
nally inherited by the shell, whose values may 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 may 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 above execution of cmd is concerned except for spe-
cial built-in commands listed below - 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 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. It is likely to disap-
pear someday.
Functions.
For historical reasons, there are two ways to define functions, the name() syntax
and the function name syntax, described in the Commands section above. Shell func-
tions are read in and stored internally. Alias names are resolved when the func-
tion is read. Functions are executed like commands with the arguments passed as
positional parameters. (See Execution below.)
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 func-
tion. 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, will also be listed with -f.
Functions can be undefined with the -f option of the unset special built-in com-
mand.
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 may 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 exten-
sion provided by the builtin built-in utility. If the get discipline is defined
for a variable, it is invoked whenever the given variable is referenced. If the
variable .sh.value is assigned a value inside the discipline function, the refer-
enced variable will evaluate to this value instead. If the set discipline is
defined for a variable, it is invoked whenever the given variable is assigned a
value. If the append discipline is defined for a variable, it is invoked whenever
a value is appended to the given variable. The variable .sh.value is given the
value of the variable before invoking the discipline, and the variable will be
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 given variable is unset. The
variable will not be unset unless it is unset explicitly from within this disci-
pline 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
will contain the value being assigned inside the set discipline function. For the
set discipline, changing .sh.value will change the value that gets assigned.
Jobs.
If the monitor option of the set command is turned on, an interactive shell asso-
ciates 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 asyn-
chronously 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.
This paragraph and the next require features that are not in all versions of UNIX
and may not apply. If you are running a job and wish to do something else you may
hit the key ^Z (control-Z) which sends a STOP signal to the current job. The shell
will then normally indicate that the job has been 'Stopped', and print another
prompt. You can then manipulate the state of this job, putting it in the back-
ground 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 ^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 will stop if it tries to read from the terminal.
Background jobs are normally allowed to produce output, but this can be disabled by
giving the command stty tostop. If you set this tty option, then background jobs
will stop when they try to produce output like they do when they try to read input.
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 given 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 will be
warned that 'You have stopped(running) jobs.' You may use the jobs command to see
what they are. If you immediately try to exit again, the shell will not warn you a
second time, and the stopped jobs will be terminated. When a login shell receives
a HUP signal, it sends a HUP signal to each job that has not been disowned with the
disown built-in command described below.
Signals.
The INT and QUIT signals for an invoked command are ignored if the command is fol-
lowed by & and the monitor option is not active. Otherwise, signals have the val-
ues inherited by the shell from its parent (but see also the trap built-in command
below).
Execution.
Each time a command is read, the above substitutions are carried out. If the com-
mand name matches one of the Special Built-in Commands listed below, it is executed
within the current shell process. Next, the command name is checked to see if it
matches a user defined function. If it does, the positional parameters are saved
and then reset to the arguments of the 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 listed below, 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 /, then the search path is not used. Otherwise, each directory in
the path is searched for an executable file of the given name that is not a direc-
tory. If found, and if the shell determines that there is a built-in version of a
command corresponding to a given pathname, this built-in is invoked in the current
process. 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 given name is executed as described above. If not found, and the
file .paths is found, and this file contains a line of the form FPATH=path where
path names an existing directory, and this directory contains a file of the given
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 given name is exe-
cuted. Otherwise, if found, a process is created and an attempt is made to execute
the command via 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 , then the library named by value will be searched for as if it
were an option argument to builtin -f, and if it contains a built-in of the speci-
fied name this will be 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 exe-
cutable was found. If the environment variable name does not already exist it will
be 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, or if the setuid and/or 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 command(s) is printed and re-executed 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=new can 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' will re-execute the most recent command which starts with the
letter c, replacing the first occurrence of the string bad with the string good.
In-line Editing Options.
Normally, each command line entered from a terminal device is simply typed followed
by a new-line ('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 charac-
ter 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 will be centered about the cursor.
The mark is a > (<, *) if the line extends on the right (left, both) side(s) 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 given 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 comple-
tion, 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 comple-
tion that does not yield a unique match, a subsequent tab will provide 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 char-
acters that are actually seen by the shell. This trap is executed after each char-
acter (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 charac-
ter 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 (see
below) and is null otherwise. By prepending ${.sh.editmode} to a value assigned to
.sh.edchar it will cause 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 dif-
ference 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 char-
acter. For example, ^F is the notation for control F. This is entered by depress-
ing '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
would be the notation for ESC followed by 'SHIFT' (capital) 'F'.)
All edit commands operate from any place on the line (not just at the beginning).
Neither the 'RETURN' nor the 'LINE FEED' key is entered after edit commands except
when noted.
^F Move cursor forward (right) one character.
M-[C Move cursor forward (right) one character.
M-f Move 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 cursor backward (left) one character.
M-[D Move cursor backward (left) one character.
M-b Move cursor backward one word.
^A Move cursor to start of line.
M-[H Move cursor to start of line.
^E Move cursor to end of line.
M-[Y Move cursor to end of line.
^]char Move cursor forward to character char on current line.
M-^]char Move cursor backward to character char on current line.
^X^X Interchange the cursor and mark.
erase (User defined erase character as defined by the stty(1) command, usually
^H or #.) Delete previous character.
lnext (User defined literal next character as defined by the stty(1) command,
or ^V if not defined.) Removes the next character's editing features (if
any).
^D Delete current character.
M-d Delete current word.
M-^H (Meta-backspace) Delete previous word.
M-h Delete previous word.
M-^? (Meta-DEL) Delete previous word (if your interrupt character is ^? (DEL,
the default) then this command will not work).
^T Transpose current character with previous character and advance the cur-
sor in emacs mode. Transpose two previous characters in gmacs mode.
^C Capitalize current character.
M-c Capitalize 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 numeri-
cal parameter whose value is less than the current cursor position, then
delete from given position up to the cursor. If preceded by a numerical
parameter whose value is greater than the current cursor position, then
delete from cursor up to given cursor position.
^W Kill from the cursor to the mark.
M-p Push the region from the cursor to the mark on the stack.
kill (User defined kill character as defined by the stty command, usually ^G
or @.) Kill the entire current line. If two kill characters are entered
in succession, all kill characters from then on cause a line feed (useful
when using paper terminals).
^Y Restore last item removed from line. (Yank item back to the line.)
^L Line feed and print current line.
M-^L Clear the screen.
^@ (Null character) Set mark.
M-space (Meta space) Set 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 previous command. Each time ^P is entered the previous command
back in time is accessed. Moves back one line when not on the first line
of a multi-line command.
M-[A Equivalent to ^P.
M-< Fetch the least recent (oldest) history line.
M-> Fetch the most recent (youngest) history line.
^N Fetch 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 given, the search is forward. String is termi-
nated by a 'RETURN' or 'NEW LINE'. 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-b, M-c, M-d, M-
f, M-h, M-l and M-^H.
M-letter Soft-key - Your alias list is searched for an alias by the name _letter
and if an alias of this name is defined, its value will be inserted on
the input queue. The letter must not be one of the above meta-functions.
M-[letter Soft-key - Your alias list is searched for an alias by the name __letter
and if an alias of this name is defined, its value will be inserted on
the input queue. This can be used to program function keys on many ter-
minals.
M-. The last word of the previous command is inserted on the line. If pre-
ceded 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 file name generation on the current word. An asterisk is
appended if the word doesn't match any file or contain any special pat-
tern characters.
M-ESC Command or file name completion as described above.
^I tab Attempts command or file name completion as described above. If a par-
tial completion occurs, repeating this will behave 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, it generates the list of matching
commands or file names as described above. 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, it is inserted instead.
^U Multiply parameter of next command by 4.
\ Escape next character. Editing characters, the user's erase, kill and
interrupt (normally ^?) characters may be entered in a command line or
in a search string if preceded by a \. The \ removes the next charac-
ter's editing features (if any).
M-^V Display 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 new-line, 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 new-line 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 will be echoed again if the speed is 1200 baud or greater and it contains
any control characters or less than one second has elapsed since the prompt was
printed. The ESC character terminates canonical processing for the remainder of
the command and the user can then modify the command line. This scheme has the
advantages of canonical processing with the type-ahead echoing of raw mode.
If the option viraw is also set, the terminal will always have canonical processing
disabled. This mode is implicit for systems that do not support two alternate end
of line delimiters, and may be helpful for certain terminals.
Input Edit Commands
By default the editor is in input mode.
erase (User defined erase character as defined by the stty command, usu-
ally ^H or #.) Delete previous character.
^W Delete the previous blank separated word. On some systems the
viraw option may 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 may be required for
this to work.
\ Escape the next erase or kill character.
^I tab Attempts command or file name completion as described above and
returns to input mode. If a partial completion occurs, repeating
this will behave as if = were entered from control mode. If no
match is found or entered after space, a tab is inserted.
Motion Edit Commands
These commands will move the cursor.
[count]l Cursor forward (right) one character.
[count][C Cursor forward (right) one character.
[count]w Cursor forward one alpha-numeric word.
[count]W Cursor to the beginning of the next word that follows a blank.
[count]e Cursor to end of word.
[count]E Cursor to end of the current blank delimited word.
[count]h Cursor backward (left) one character.
[count][D Cursor backward (left) one character.
[count]b Cursor backward one word.
[count]B Cursor to preceding blank separated word.
[count]| 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]; Repeats count times, the last single character find command, f, F,
t, or T.
[count], Reverses the last single character find command count times.
0 Cursor to start of line.
^ Cursor to start of line.
[H Cursor to first non-blank character in line.
$ Cursor to end of line.
[Y Cursor to end of line.
% Moves to balancing (, ), {, }, [, or ]. If cursor is not on one
of the above characters, the remainder of the line is searched for
the first occurrence of one of the above characters first.
Search Edit Commands
These commands access your command history.
[count]k Fetch previous command. Each time k is entered the previous com-
mand back in time is accessed.
[count]- Equivalent to k.
[count][A Equivalent to k.
[count]j Fetch next command. Each time j is entered the next command for-
ward in time is accessed.
[count]+ Equivalent to j.
[count][B Equivalent to j.
[count]G The command number count is fetched. 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 'NEW LINE'. If
string is preceded by a ^, the matched line must begin with
string. If string is null, the previous string will be used.
?string Same as / except that search will be in the forward direction.
n Search for next match of the last pattern to / or ? commands.
N Search for next match of the last pattern to / or ?, but in
reverse direction.
Text Modification Edit Commands
These commands will 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 $a.
[count]cmotion
c[count]motion
Delete current character through the character that motion would
move the cursor to and enter input mode. If motion is c, the
entire line will be deleted and input mode entered.
C Delete the current character through the end of line and enter
input mode. Equivalent to c$.
S Equivalent to cc.
[count]s Replace characters under the cursor in input mode.
D Delete the current character through the end of line. Equivalent
to d$.
[count]dmotion
d[count]motion
Delete current character through the character that motion would
move to. If motion is d , the entire line will be deleted.
i Enter input mode and insert text before the current character.
I Insert text before the beginning of the line. Equivalent to 0i.
[count]P Place the previous text modification before the cursor.
[count]p Place the previous text modification after the cursor.
R Enter input mode and replace characters on the screen with charac-
ters you type overlay fashion.
[count]rc Replace the count character(s) starting at the current cursor
position with c, and advance the cursor.
[count]x Delete current character.
[count]X Delete preceding character.
[count]. Repeat the previous text modification command.
[count]~ Invert the case of the count character(s) starting at the current
cursor position and advance the cursor.
[count]_ Causes the count word of the previous command to be appended and
input mode entered. The last word is used if count is omitted.
* Causes an * to be appended to the current word and file name gen-
eration attempted. If no match is found, it rings the bell. Oth-
erwise, the word is replaced by the matching pattern and input
mode is entered.
\ Command or file name completion as described above.
Other Edit Commands
Miscellaneous commands.
[count]ymotion
y[count]motion
Yank current character through character that motion would move
the cursor to and puts them into the delete buffer. The text and
cursor are unchanged.
yy Yanks the entire line.
Y Yanks from current position to end of line. Equivalent to y$.
u Undo the last text modifying command.
U Undo all the text modifying commands performed on the line.
[count]v Returns the command hist -e ${VISUAL:-${EDITOR:-vi}} count in the
input buffer. If count is omitted, then the current line is used.
^L Line feed and print current line. Has effect only 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 #, then this command
deletes this # and each # that follows a newline. Otherwise,
sends the line after inserting a # in front of each line in the
command. Useful for causing the current line to be inserted in
the history as a comment and uncommenting previously commented
commands in the history file.
[count]= If count is not specified, it generates the list of matching com-
mands or file names as described above. Otherwise, the word under
the the cursor is replaced by the count item from the most
recently generated command or file list. If the cursor is not on
a word, it is inserted instead.
@letter Your alias list is searched for an alias by the name _letter and
if an alias of this name is defined, its value will be inserted 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/Output
redirection is permitted. Unless otherwise indicated, the output is written on
file descriptor 1 and the exit status, when there is no syntax error, is zero.
Except for :, true, false, echo, newgrp, and login, all built-in commands accept --
to indicate end of options. They also interpret the option --man as a request to
display the man 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 + sym-
bols 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 vari-
able 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 given, they become
the positional parameters while processing the . command and the original
positional parameters are restored upon completion. Otherwise the posi-
tional 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 given, an alias is defined for
each name whose value is given. 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 given 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 given, 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 given, 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 speci-
fied job into the background. The current job is put in the background if
job is not specified. See Jobs 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
b_mycommand(int argc, char *argv[], void *context) for the builtin command
mycommand where argv is array an 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 given built-ins. On systems that support dynamic load-
ing, 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 subse-
quent invocations of builtin. Multiple libraries can be specified with sep-
arate 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 can be in either of two forms. In the first form it changes
the current directory to arg. If arg is - the directory is changed to the
previous directory. The shell variable HOME is the default arg. The vari-
able 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). Note that the current directory is specified by a
null path name, which can appear immediately after the equal sign or between
the colon delimiters anywhere else in the path list. If arg begins with a /
then 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 may not be executed by rksh. rksh93.
command [ -pvxV ] name [ arg ... ]
Without the -v or -V options, command executes name with the arguments given
by arg. The -p option causes a default path to be searched rather than the
one defined by the value of PATH. Functions will not be searched for when
finding name. In addition, if name refers to a special built-in, none of
the special properties associated with the leading daggers will be honored.
(For example, the predefined alias redirect=?command exec? prevents a script
from terminating when an invalid redirection is given.) With the -x option,
if command execution would result in a failure because there are too many
arguments, errno E2BIG, the shell will invoke 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 will be passed on each invoca-
tion. The exit status will be the maximum invocation exit status. With the
-v option, command is equivalent to the built-in whence command described
below. The -V option causes command to act like whence -v.
+ continue [ n ]
Resume the next iteration of the enclosing for, while, until, or select
loop. If n is specified, then resume at the n-th enclosing loop.
disown [ job... ]
Causes the shell not to send a HUP signal to each given 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 con-
tain a \, then echo prints each of its arguments separated by a space and
terminated by a new-line. Otherwise, the behavior of echo is system depen-
dent and print or printf described below should be used. See echo(1) for
usage and description.
+ eval [ arg ... ]
The arguments are read as input to the shell and the resulting command(s)
executed.
+ exec [ -c ] [ -a name ] [ arg ... ]
If arg is given, 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/output arguments may
appear and affect the current process. If arg is not given, the effect of
this command is to modify file descriptors as prescribed by the input/output
redirection list. In this case, any file descriptor numbers greater than 2
that are opened with this mechanism are closed when invoking another pro-
gram.
+ exit [ n ]
Causes the shell to exit with the exit status specified by n. The value
will be the least significant 8 bits of the specified status. If n is omit-
ted, then the exit status is that of the last command executed. An end-of-
file will also cause the shell to exit except for a shell which has the
ignoreeof option (see set below) turned on.
++ export [ -p ] [ name[=value] ] ...
If name is not given, the names and values of each variable with the export
attribute are printed with the values quoted in a manner that allows them to
be re-input. The -p option causes the word export to be inserted before
each one. Otherwise, the given 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 speci-
fied 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 given by name. The
configuration parameters are defined by the IEEE POSIX 1003.1 and IEEE POSIX
1003.2 standards. (See pathconf(2) and sysconf(2).) The pathname argument
is required for parameters whose value depends on the location in the file
system. If no arguments are given, 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 not begin-
ning with + or - or the argument -- ends the options. Options beginning
with + are only recognized when optstring begins with a +. optstring con-
tains 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 argument 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 will be 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 may be specified as a number or as a string. A string is
used to locate the most recent command starting with the given string. A
negative number is used as an offset to the current command number. If the
-l option is selected, the commands are listed on standard output. Other-
wise, the editor program ename is invoked on a file containing these key-
board 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 exe-
cuted if the changes have been saved. If last is not specified, then it
will be set to first. If first is not specified, the default is the previ-
ous 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
above 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 given job; or all active jobs if job is omit-
ted. 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 given by number with the -n
option or by name with the -s option (as given in <signal.h>, stripped of
the prefix ''SIG'' with the exception that SIGCLD is named CHLD). For back-
ward 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 (hangup), then the job or process will be 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 corre-
sponding 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 Arith-
metic Evaluation above, for a description of arithmetic expression evalua-
tion.
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 out-
put. The -f option causes the arguments to be printed as described by
printf. In this case, any e, n, r, R options are ignored. Otherwise,
unless the -R or -r, are specified, the following escape conventions will be
applied:
\a The alert character (ascii 07).
\b The backspace character (ascii 010).
\c Causes print to end without processing more arguments and not adding
a new-line.
\f The formfeed character (ascii 014).
\n The new-line character (ascii 012).
\r The carriage return character (ascii 015).
\t The tab character (ascii 011).
\v The vertical tab character (ascii 013).
\E The escape character (ascii 033).
\\ The backslash character \.
\0x The character defined by the 1, 2, or 3-digit octal string given by
x.
The -R option will print all subsequent arguments and options other than -n.
The -e causes the above 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 will be placed. The default is 1. If the option -n is used, no new-
line 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 variable will be printed. This is most useful for vari-
ables whose attribute is -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 pat-
tern. 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 reinput to the shell. A %(date-format)T for-
mat 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 will output 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 caues base# to be prepended. The # flag when used with the d
specifier without an output base, causes the output to be displayed in thou-
sands 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 given, 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 continua-
tion. The -d option causes the read to continue to the first character of
delim rather than new-line. The -n option causes at most n bytes to read
rather a full line but will return 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 sec-
ond 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 will be 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 will be 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 spec-
ify a timeout 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 given, 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 re-inputted. The -p option causes the word readonly to be
inserted before each one. Otherwise, the given 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 will be 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 [ ?CGabefhkmnoprstuvx ] [ ?o [ option ] ] ... [ ?A vname ] [ arg ... ]
The options for this command have meaning as follows:
-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 Enable brace pattern field generation. This is the default behav-
ior.
-C Prevents redirection > from truncating existing files. Files that
are created are opened with the O_EXCL mode. Requires >| to trun-
cate a file when turned on.
-G Causes the pattern ** by itself to match files and zero or more
directories and sub-directories when used for file name generation.
If followed by a / only directories and sub-directories are matched.
-a All subsequent variables that are defined are automatically
exported.
-b Prints job completion messages as soon as a background job changes
state rather than waiting for the next prompt.
-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.
-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 will run in a separate process group and a line will
print upon completion. The exit status of background jobs is
reported in a completion message. On systems with job control, this
option is turned on automatically for interactive shells.
-n Read commands and check them for syntax errors, but do not execute
them. Ignored for interactive shells.
-o The following argument can be one of the following option names:
allexport
Same as -a.
errexit Same as -e.
bgnice All background jobs are run at a lower priority. This is
the default mode.
bracexpand
Same as -B.
emacs Puts you in an emacs style in-line editor for command entry.
globstar
Same as -G.
gmacs Puts you in a gmacs style in-line editor for command entry.
ignoreeof
The shell will 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 will use multiple lines on the screen
for lines that are longer than the width of the screen.
This may 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 will not complete until all components of the
pipeline have completed, and the return value will be the
value of the last non-zero command to fail or zero if no
command has failed.
showme When enabled, simple commands or pipelines preceded by a
semicolon (;) will be displayed as if the xtrace option were
enabled but will not be executed. Otherwise, the leading ;
will be ignored.
privileged
Same as -p.
verbose Same as -v.
trackall
Same as -h.
vi Puts you in insert mode of a vi style in-line 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, then the current option 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; useful in setting $1 to a value
beginning with -. If no arguments follow this option then the posi-
tional 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 may 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
given, then the names and values of all variables are printed on the stan-
dard output.
+ shift [ n ]
The positional parameters from $n+1 ... are renamed $1 ... , 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 sec-
ond given 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
will be processed as if it were an argument to eval when the shell receives
signal(s) sig. Each sig can be given as a number or as the name of the sig-
nal. 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 val-
ues. 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 will be executed
whenever a command has a non-zero exit status. If sig is DEBUG then action
will be executed before each command. The variable .sh.command will contain
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 will be 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. The following list of attributes may
be specified:
-A Declares vname to be an associative array. Subscripts are strings
rather than arithmetic expressions.
-a Declares vname to be an indexed array. This is optional unless
except for compound variable assignments.
-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 will
be used.
-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 will be used.
-H This option provides UNIX to host-name file mapping on non-UNIX
machines.
-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.
-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.
-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.
-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 will be searched to find the function definition when the
function is referenced. If no options other than -f is specified,
then the function definition will be 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.
-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 will be determined by the size associated with the -Z. If
the base64 string assigned results in more data, it will be trun-
cated. Otherwise, it will be 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.
-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 out-
put arithmetic base, otherwise the output base will be ten.
-l All upper-case characters are converted to lower-case. The upper-
case option, -u, is turned off.
-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 ref-
erence a variable inside a function whose name has been passed as an
argument.
-r The given vnames are marked readonly 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 lower-case characters are converted to upper-case. The lower-
case option, -l, is turned off.
-x The given vnames are marked for automatic export to the environment
of subsequently-executed commands. Variables whose names contain a .
cannot be exported.
The -i attribute cannot be specified along with -R, -L, -Z, or -f.
Using + rather than - causes these options to be turned off. If no vname
arguments are given, 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 given, only those variables which have all of the
given options are printed. Otherwise, the vnames and attributes of all
variables that have attributes are printed.
ulimit [ -HSacdfmnpstv ] [ limit ]
Set or display a resource limit. The available resource limits are listed
below. 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 below with each resource, or the value
unlimited. The -H and -S options specify whether the hard limit or the soft
limit for the given resource is set. A hard limit cannot be increased once
it is set. A soft limit can be increased up to the value of the hard limit.
If neither the 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. When more than one resource is
specified, then the limit name and unit is printed before the value.
-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 K-bytes 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 may be
read).
-m The number of K-bytes 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 K-bytes on the size of the stack area.
-t The number of CPU seconds to be used by each process.
-v The number of K-bytes for virtual memory.
If no option is given, -f is assumed.
umask [ -S ] [ mask ]
The user file-creation mask is set to mask (see umask(2)). mask can either
be an octal number or a symbolic value as described in chmod(1). If a sym-
bolic value is given, 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.
+ unalias [ -a ] name ...
The aliases given 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 given by the list of vnames are unassigned, i.e., their values
and attributes are erased. Readonly 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 will be 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
given, 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 -p option turns off
the -v option. The -a option is similar to the -v option but causes all
interpretations of the given 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/.pro-
file, if either file exists. Next, for interactive shells, commands are read from
the file named by performing parameter expansion, command substitution, and arith-
metic 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 will be 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
below; 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.
-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 above, is written to file descriptor 2.
-i If the -i option is present or if the shell input and output are attached
to a terminal (as told by tcgetattr(2)), then 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 If the -r option is present, the shell is a restricted shell.
-D A list of all double quoted strings that are preceded by a $ will be
printed on standard output and the shell will exit. This set of strings
will be subject to language translation when the locale is not C or
POSIX. No commands will be executed.
-P If -P or -o profile is present, the shell is a profile shell (see
pfexec(1)).
-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. The filename argument specifies the gener-
ated database. A script file must be provided on the command line as
well.
The remaining options and arguments are described under the set command above. An
optional - as the first argument is ignored.
Rksh Only.
Rksh is used to set up login names and execution environments whose capabilities
are more controlled than those of the standard shell. The actions of rksh are
identical to those of ksh, 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.
The restrictions above are enforced after .profile and the ENV files are inter-
preted.
When a command to be executed is found to be a shell procedure, rksh invokes ksh to
execute it. Thus, it is possible to provide to the end-user shell procedures that
have access to the full power of the standard shell, while imposing a limited menu
of commands; this scheme assumes that the end-user does not have write and execute
permissions in the same directory.
The net effect of these rules is that the writer of the .profile has complete con-
trol 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 (e.g., /usr/rbin)
that can be safely invoked by rksh.
EXIT STATUS
Errors detected by the shell, such as syntax errors, cause the shell to return a
non-zero exit status. If the shell is being used non-interactively, then execution
of the shell file is abandoned unless the error occurs inside a subshell in which
case the subshell is abandoned. Otherwise, the shell returns the exit status of
the last command executed (see also the exit command above). 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.
FILES
/etc/profile The system wide initialization file, executed for login shells.
$HOME/.profile
The personal initialization file, executed for login shells after /etc/pro-
file.
$HOME/..kshrc
Default personal initialization file, executed for interactive shells when
ENV is not set.
/etc/suid_profile
Alternative initialization file, executed when instead of personal initial-
ization file when the real and effective user or group id do not match.
/dev/null
NULL device
SEE ALSO
cat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1), fgrep(1),
gmacs(1), grep(1), newgrp(1), pfexec(1), stty(1), test(1), umask(1), vi(1), dup(2),
exec(2), fork(2), getpwnam(3), ioctl(2), lseek(2), paste(1), pathconf(2), pipe(2),
sysconf(2), umask(2), ulimit(2), wait(2), rand(3), a.out(5), profile(5), envi-
ron(7).
Morris I. Bolsky and David G. Korn, The New KornShell Command and Programming Lan-
guage, Prentice Hall, 1995.
POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE,
1993.
CAVEATS
If a command is executed, and then a command with the same name is installed in a
directory in the search path before the directory where the original command was
found, the shell will continue to exec the original command. Use the -t option of
the alias command to correct this situation.
Some very old shell scripts contain a ^ as a synonym for the pipe character |.
Using the hist built-in command within a compound command will cause the whole com-
mand to disappear from the history file.
The built-in command . file reads the whole file before any commands are executed.
Therefore, alias and unalias commands in the file will 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 won't be executed until the foreground job terminates.
It is a good idea to leave a space after the comma operator in arithmetic expres-
sions to prevent the comma from being interpreted as the decimal point character in
certain locales.
RDS Standard User Environment Utilities KSH(1)
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