User Commands KSH(1)
NAME
ksh, rksh, pfksh - KornShell, a standard/restricted command
and programming language
SYNOPSIS
ksh [ _abcefhikmnoprstuvxBCDP ] [ -R file ] [ _o option ]
... [ - ] [ arg ... ]
rksh [ _abcefhikmnoprstuvxBCD ] [ -R file ] [ _o option ]
... [ - ] [ arg ... ]
DESCRIPTION
Ksh is a command and programming language that executes com-
mands read from a terminal or a file. Rksh is a restricted
version of the command interpreter ksh; it is used to set up
login names and execution environments whose capabilities
are more controlled than those of the standard shell.
Rpfksh is a profile shell version of the command interpreter
ksh; it is used to to execute commands with the attributes
specified by the user's profiles (see pfexec(1)). See Invo-
cation below for the meaning of arguments to the shell.
Definitions.
A metacharacter is one of the following characters:
; & ( ) | < > new-line space tab
A blank is a tab or a space. An identifier is a sequence of
letters, digits, or underscores starting with a letter or
underscore. Identifiers are used as components of variable
names. A vname is a sequence of one or more identifiers
separated by a . and optionally preceded by a .. Vnames are
used as function and variable names. A word is a sequence
of characters from the character set defined by the current
locale, excluding non-quoted metacharacters.
A command is a sequence of characters in the syntax of the
shell language. The shell reads each command and carries
out the desired action either directly or by invoking
separate utilities. A built-in command is a command that is
carried out by the shell itself without creating a separate
process. Some commands are built-in purely for convenience
and are not documented here. Built-ins that cause side
effects in the shell environment and built-ins that are
found before performing a path search (see Execution below)
are documented here. For historical reasons, some of these
built-ins behave differently than other built-ins and are
called special built-ins.
Commands.
A simple-command is a list of variable assignments (see
Variable Assignments below) or a sequence of blank separated
words which may be preceded by a list of variable
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assignments (see Environment below). The first word speci-
fies the name of the command to be executed. Except as
specified below, the remaining words are passed as arguments
to the invoked command. The command name is passed as argu-
ment 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 correspond-
ing to the exit status can be obtained via the -l option of
the kill built-in utility).
A pipeline is a sequence of one or more commands separated
by |. The standard output of each command but the last is
connected by a pipe(2) to the standard input of the next
command. Each command, except possibly the last, is run as
a separate process; the shell waits for the last command to
terminate. The exit status of a pipeline is the exit status
of the last command unless the pipefail option is enabled.
Each pipeline can be preceded by the reserved word ! which
causes the exit status of the pipeline to become 0 if the
exit status of the last command is non-zero, and 1 if the
exit status of the last command is 0.
A list is a sequence of one or more pipelines separated by
;, &, |&, &&, or ||, and optionally terminated by ;, &, or
|&. Of these five symbols, ;, &, and |& have equal pre-
cedence, which is lower than that of && and ||. The symbols
&& and || also have equal precedence. A semicolon (;)
causes sequential execution of the preceding pipeline; an
ampersand (&) causes asynchronous execution of the preceding
pipeline (i.e., the shell does not wait for that pipeline to
finish). The symbol |& causes asynchronous execution of the
preceding pipeline with a two-way pipe established to the
parent shell; the standard input and output of the spawned
pipeline can be written to and read from by the parent shell
by applying the redirection operators <& and >& with arg p
to commands and by using -p option of the built-in commands
read and print described later. The symbol && (||) causes
the list following it to be executed only if the preceding
pipeline returns a zero (non-zero) value. One or more new-
lines may appear in a list instead of a semicolon, to del-
imit a command.
A command is either a simple-command or one of the follow-
ing. Unless otherwise stated, the value returned by a com-
mand is that of the last simple-command executed in the com-
mand.
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
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starting from 1 (see Parameter Expansion below). Exe-
cution ends when there are no more words in the list.
for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
The arithmetic expression expr1 is evaluated first (see
Arithmetic evaluation below). The arithmetic expres-
sion expr2 is repeatedly evaluated until it evaluates
to zero and when non-zero, list is executed and the
arithmetic expression expr3 evaluated. If any expres-
sion 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 posi-
tional parameters starting from 1 are used instead (see
Parameter Expansion below). The PS3 prompt is printed
and a line is read from the standard input. If this
line consists of the number of one of the listed words,
then the value of the variable vname is set to the word
corresponding to this number. If this line is empty,
the selection list is printed again. Otherwise the
value of the variable vname is set to null. The con-
tents of the line read from standard input is saved in
the variable REPLY. The list is executed for each
selection until a break or end-of-file is encountered.
If the REPLY variable is set to null by the execution
of list, then the selection list is printed before
displaying the PS3 prompt for the next selection.
case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
A case command executes the list associated with the
first pattern that matches word. The form of the pat-
terns is the same as that used for file-name generation
(see File Name Generation below). The ;; operator
causes execution of case to terminate. If ;& is used
in place of ;; the next subsequent list, if any, is
executed.
;fi
if list ;then list [ elif list ;then list ] ... [ ;else list ]
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 exe-
cuted 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
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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 ter-
minates. 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 arith-
metic evaluation described below. If the value of the
arithmetic expression is non-zero, the exit status is
0, otherwise the exit status is 1.
(list)
Execute list in a separate environment. Note, that if
two adjacent open parentheses are needed for nesting, a
space must be inserted to avoid evaluation as an arith-
metic command as described above.
{ list;}
list is simply executed. Note that unlike the meta-
characters ( 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 discip-
line function and the portion of the varname preceding
the last . must refer to an existing variable. The body
of the function is the list of commands between { and
}. A function defined with the function varname syntax
can also be used as an argument to the . special
built-in command to get the equivalent behavior as if
the varname() syntax were used to define it. (See
Functions below.)
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
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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 spe-
cial 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.
assignment ...
Compound variable assignment. This
creates a compound variable varname with
sub-variables of the form varname.name,
where name is the name portion of
assignment. The value of varname will
contain all the assignment elements.
Additional assignments made to sub-
variables of varname will also be
displayed as part of the value of var-
name. 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 separat-
ing 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
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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 previ-
ous 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 follow-
ing 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 meta-
characters, 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 cannot be used to redefine the
reserved words listed above. Aliases can be created and
listed with the alias command and can be removed with the
unalias command.
Aliasing is performed when scripts are read, not while they
are executed. Therefore, for an alias to take effect, the
alias definition command has to be executed before the com-
mand 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 -E'
functions='typeset -f'
hash='alias -t ~--'
history='hist -l'
integer='typeset -i'
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
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to see if it begins with an unquoted ~. For tilde substitu-
tion, 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 (often the /etc/passwd file).
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 ~ fol-
lowed 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 executed (see Quoting
below). The command substitution $(cat file) can be
replaced by the equivalent but faster $(<file). The command
substitution $(n<#) will expand to the current byte offset
for file descriptor n.
Arithmetic Substitution.
An arithmetic expression enclosed in double parentheses pre-
ceded 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 support the /dev/fd directory for nam-
ing 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 >(pro-
cess1) >(process2)
cuts fields 1 and 3 from the files file1 and file2 respec-
tively, 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
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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 vari-
ables pass values and attributes to the environment.
The shell supports both indexed and associative arrays. An
element of an array variable is referenced by a subscript.
A subscript for an indexed array is denoted by an arithmetic
expression (see Arithmetic evaluation below) between a [ and
a ]. To assign values to an indexed array, use set -A vname
value ... . The value of all subscripts must be in the
range of 0 through 4095. Indexed arrays need not be
declared. Any reference to a variable with a valid sub-
script 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 vari-
able. A nameref is created with the -n attribute of
typeset. The value of the variable at the time of the
typeset command becomes the variable that will be referenced
whenever the nameref variable is used. The name of a nam-
eref cannot contain a .. When a variable or function name
contains a ., and the portion of the name up to the first .
matches the name of a nameref, the variable referred to is
obtained by replacing the nameref portion with the name of
the variable referenced by the nameref. If a nameref is
used as the index of a for loop, a name reference is esta-
blished for each item in the list. A nameref provides a
convenient way to refer to the variable inside a function
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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 parame-
ters.
${parameter}
The shell reads all the characters from ${ to the
matching } as part of the same word even if it contains
braces or metacharacters. The value, if any, of the
parameter is substituted. The braces are required when
parameter is followed by a letter, digit, or underscore
that is not to be interpreted as part of its name, when
the variable name contains a ., or when a variable is
subscripted. If parameter is one or more digits then
it is a positional parameter. A positional parameter
of more than one digit must be enclosed in braces. If
parameter is * or @, then all the positional parame-
ters, 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 param-
eters is substituted. Otherwise, the length of the
value of the parameter is substituted.
${#vname[*]}
${#vname[@]}
The number of elements in the array vname is substi-
tuted.
${!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 sub-
scripts for vname is generated. For a variable that is
not an array, the value is 0 if the variable is set.
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Otherwise it is null. When subscript is @, same as
above, except that when used in double quotes, each
array subscript yields a separate argument.
${!prefix*}
Expands to the names of the variables whose names begin
with prefix.
${parameter:-word}
If parameter is set and is non-null then substitute its
value; otherwise substitute word.
${parameter:=word}
If parameter is not set or is null then set it to word;
the value of the parameter is then substituted. Posi-
tional 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 stan-
dard message is printed.
${parameter:+word}
If parameter is set and is non-null then substitute
word; otherwise substitute nothing.
In the above, word is not evaluated unless it is to be used
as the substituted string, so that, in the following exam-
ple, 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 start-
ing at the character (counting from 0) determined by
expanding offset as an arithmetic expression and con-
sisting of the number of characters determined by the
arithmetic expression defined by length. In the second
form, the remainder of the value is used. If A negative
offset counts backwards from the end of parameter.
Note that one or more blanks is required in front of a
minus sign to prevent the shell from interpreting the
operator as :-. If parameter is * or @, or is an array
name indexed by * or @, then offset and length refer to
the array index and number of elements respectively. A
negative offset is taken relative to one greater than
the highest subscript for indexed arrays. The order
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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 sub-
stituted. In the first form the smallest matching pat-
tern is deleted and in the second form the largest
matching pattern is deleted. When parameter is @, *,
or an array variable with subscript @ or *, the sub-
string operation is applied to each element in turn.
${parameter%pattern}
${parameter%%pattern}
If the shell pattern matches the end of the value of
parameter, then the value of this expansion is the
value of the parameter with the matched part deleted;
otherwise substitute the value of parameter. In the
first form the smallest matching pattern is deleted and
in the second form the largest matching pattern is
deleted. When parameter is @, *, or an array variable
with subscript @ or *, the substring operation is
applied to each element in turn.
${parameter/pattern/string}
${parameter//pattern/string}
${parameter/#pattern/string}
${parameter/%pattern/string}
Expands parameter and replaces the longest match of
pattern with the given string. Each occurrence of \n
in string is replaced by the portion of parameter that
matches the n-th sub-pattern. In the first form, only
the first occurrence of pattern is replaced. In the
second form, each match for pattern is replaced by the
given string. The third form restricts the pattern
match to the beginning of the string while the fourth
form restricts the pattern match to the end of the
string. When string is null, the pattern will be
deleted and the / in front of string may be omitted.
When parameter is @, *, or an array variable with sub-
script @ or *, the substitution operation is applied to
each element in turn. In this case, the string portion
of word will be re-evaluated for each element.
The following parameters are automatically set by the shell:
# The number of positional parameters in decimal.
- Options supplied to the shell on invocation or by
the set command.
? The decimal value returned by the last executed
command.
$ The process number of this shell.
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_ Initially, the value of _ is an absolute pathname
of the shell or script being executed as passed in
the environment. Subsequently it is assigned the
last argument of the previous command. This
parameter is not set for commands which are asyn-
chronous. 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.
.sh.command
When processing a DEBUG trap, this variable con-
tains the current command line that is about to
run.
.sh.edchar
This variable contains the value of the keyboard
character (or sequence of characters if the first
character is an ESC, ascii 033) that has been
entered when processing a KEYBD trap (see Key
Bindings below). If the value is changed as part
of the trap action, then the new value replaces
the key (or key sequence) that caused the trap.
.sh.edcol
The character position of the cursor at the time
of the most recent KEYBD trap.
.sh.edmode
The value is set to ESC when processing a KEYBD
trap while in vi insert mode. (See Vi Editing
Mode below.) Otherwise, .sh.edmode is null when
processing a KEYBD trap.
.sh.edtext
The characters in the input buffer at the time of
the most recent KEYBD trap. The value is null
when not processing a KEYBD trap.
.sh.file
The pathname of the file than contains the current
command.
.sh.fun
The name of the current function that is being
executed.
.sh.match
An indexed array which stores the most recent
match and sub-pattern matches after conditional
pattern matches that match and after variables
expansions using the operators #, %, or /. The
0-th element stores the complete match and the i-
th. element stores the i-th submatch. The
.sh.match variable becomes unset when the variable
that has expanded is assigned a new value.
.sh.name
Set to the name of the variable at the time that a
discipline function is invoked.
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.sh.subscript
Set to the name subscript of the variable at the
time that a discipline function is invoked.
.sh.subshell
The current depth for subshells and command sub-
stitution.
.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 func-
tion being executed.
OLDPWD
The previous working directory set by the cd com-
mand.
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 com-
mand.
RANDOM
Each time this variable is referenced, a random
integer, uniformly distributed between 0 and
32767, is generated. The sequence of random
numbers can be initialized by assigning a numeric
value to RANDOM.
REPLY
This variable is set by the select statement and
by the read built-in command when no arguments are
supplied.
SECONDS
Each time this variable is referenced, the number
of seconds since shell invocation is returned. If
this variable is assigned a value, then the value
returned upon reference will be the value that was
assigned plus the number of seconds since the
assignment.
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.
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EDITOR
If the value of this variable ends in emacs,
gmacs, or vi and the VISUAL variable is not set,
then the corresponding option (see Special Command
set below) will be turned on.
ENV If this variable is set, then parameter expansion,
command substitution, and arithmetic substitution
are performed on the value to generate the path-
name 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 $HOME/.kshrc.
FCEDIT
Obsolete name for the default editor name for the
hist command. FCEDIT is not used when HISTEDIT is
set.
FIGNORE
A pattern that defines the set of filenames that
will be ignored when performing filename matching.
FPATH
The search path for function definitions. The
directories in this path are searched for a file
with the same name as the function or command when
a function with the -u attribute is referenced and
when a command is not found. If an executable
file with the name of that command is found, then
it is read and executed in the current environ-
ment. Unlike PATH, the current directory must be
represented explictily by . rather than by adja-
cent : characters or a beginning or ending :.
HISTCMD
Number of the current command in the history file.
HISTEDIT
Name for the default editor name for the hist com-
mand.
HISTFILE
If this variable is set when the shell is invoked,
then the value is the pathname of the file that
will be used to store the command history (see
Command Re-entry below).
HISTSIZE
If this variable is set when the shell is invoked,
then the number of previously entered commands
that are accessible by this shell will be greater
than or equal to this number. The default is 128.
HOME The default argument (home directory) for the cd
command.
IFS Internal field separators, normally space, tab,
and new-line that are used to separate the results
of command substitution or parameter expansion and
to separate fields with the built-in command read.
The first character of the IFS variable is used to
RDS Standard Last change: User Environment Utilities 14
User Commands KSH(1)
separate arguments for the "$*" substitution (see
Quoting below). Each single occurrence of an IFS
character in the string to be split, that is not
in the isspace character class, and any adjacent
characters in IFS that are in the isspace charac-
ter class, delimit a field. One or more charac-
ters in IFS that belong to the isspace character
class, delimit a field. In addition, if the same
isspace character appears consecutively inside
IFS, this character is treated as if it were not
in the isspace class, so that if IFS consists of
two tab characters, then two adjacent tab charac-
ters 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 ?
RDS Standard Last change: User Environment Utilities 15
User Commands KSH(1)
and a message that will be printed. The message
will undergo parameter expansion, command substi-
tution, and arithmetic substitution with the vari-
able $_ defined as the name of the file that has
changed. The default message is you have mail in
$_.
PATH The search path for commands (see Execution
below). The user may not change PATH if executing
under rksh (except in .profile).
PS1 The value of this variable is expanded for parame-
ter expansion, command substitution, and arith-
metic substitution to define the primary prompt
string which by default is ``$''. 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 parame-
ter evaluation, command substitution, and arith-
metic 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 environ-
ment. 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 sys-
tem mode.
%P The CPU percentage, computed as (U + S)
/ R.
The braces denote optional portions. The optional
p is a digit specifying the precision, the number
of fractional digits after a decimal point. A
RDS Standard Last change: User Environment Utilities 16
User Commands KSH(1)
value of 0 causes no decimal point or fraction to
be output. At most three places after the decimal
point can be displayed; values of p greater than 3
are treated as 3. If p is not specified, the
value 3 is used.
The optional l specifies a longer format, includ-
ing 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 timeout value for the read built-in
command. The select compound command terminates
after TMOUT seconds when input is from a terminal.
Otherwise, the shell will terminate if a line is
not entered within the prescribed number of
seconds while reading from a terminal. (Note that
the shell can be compiled with a maximum bound for
this value which cannot be exceeded.)
VISUAL
If the value of this variable ends in emacs,
gmacs, or vi then the corresponding option (see
Special Command set below) 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.
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User Commands KSH(1)
If the braceexpand (-B) option is set then each of the
fields resulting from IFS are checked to see if they contain
one or more of the brace patterns {*,*}, {l1..l2} , {n1..n2}
, {n1..n2% fmt} , {n1..n2 ..n3} , or {n1..n2 ..n3%fmt} ,
where * represents any character, l1,l2 are letters and
n1,n2,n3 are signed numbers and fmt is a format specified as
used by printf. In each case, fields are created by
prepending the characters before the { and appending the
characters after the } to each of the strings generated by
the characters between the { and }. The resulting fields
are checked to see if they have any brace patterns.
In the first form, a field is created for each string
between { and ,, between , and ,, and between , and }. The
string represented by * can contain embedded matching { and
} without quoting. Otherwise, each { and } with * must be
quoted.
In the seconds form, l1 and l2 must both be either upper
case or both be lower case characters in the C locale. In
this case a field is created for each character from l1 thru
l2.
In the remaining forms, a field is created for each number
starting at n1 and continuing until it reaches n2 increment-
ing n1 by n3. The the cases where n3 is not specified
behave as if n3 where 1 if n1<=n2 and -1 otherwise. If
forms which specify %fmt any format flags, widths and preci-
sions can be specified and fmt can end in any of the specif-
iers 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 charac-
ters *, ?, (, and [ unless the -f option has been set. If
one of these characters appears, then the word is regarded
as a pattern. Each file name component that contains any
pattern character is replaced with a lexicographically
sorted set of names that matches the pattern from that
directory. If no file name is found that matches the pat-
tern, then that component of the filename is left unchanged.
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 charac-
ter . 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.
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User Commands KSH(1)
* Matches any string, including the null string.
When used for filename expansion, if the globstar
option is on, two adjacent *'s by itself will
match all files and zero or more directories and
subdirectories. If followed by a / than only
directories and subdirectories will match.
? Matches any single character.
[...]
Matches any one of the enclosed characters. A
pair of characters separated by - matches any
character lexically between the pair, inclusive.
If the first character following the opening [ is
a ! 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 stan-
dard: (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 sym-
bol symbol.
A pattern-list is a list of one or more patterns separated
from each other with a & or |. A & signifies that all pat-
terns must be matched whereas | requires that only one pat-
tern 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 pat-
terns.
+(pattern-list)
Matches one or more occurrences of the given pat-
terns.
{n}(pattern-list)
Matches n occurrences of the given patterns.
{m,n}(pattern-list)
Matches from m to n occurrences of the given pat-
terns. If m is omitted, 0 will be used. If n is
omitted at least m occurrences will be matched.
@(pattern-list)
Matches exactly one of the given patterns.
!(pattern-list)
Matches anything except one of the given patterns.
By default, each pattern, or sub-pattern will match the
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User Commands KSH(1)
longest string possible consistent with generating the long-
est 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 parenthesis, the
backslash character \ is treated specially even when inside
a character class. All ANSI-C character escapes are recog-
nized and match the specified character. In addition the
following escape sequences are recognized:
\d Matches any charcter in the digit class.
\D Matches any charcter not in the digit class.
\s Matches any charcter in the space class.
\S Matches any charcter not in the space class.
\w Matches any charcter in the word class.
\W Matches any charcter 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 start-
ing 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, start-
ing 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.
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User Commands KSH(1)
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.
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 subse-
quent ~(...) 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 termi-
nation 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 pre-
ceded 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 sub-
stitution 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$2d...", where d is the first character of the IFS vari-
able, whereas "$@" 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
RDS Standard Last change: User Environment Utilities 21
User Commands KSH(1)
recognition of function names or built-in command names
listed below cannot be altered by quoting them.
Arithmetic Evaluation.
The shell performs arithmetic evaluation for arithmetic sub-
stitution, 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 recog-
nized. 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 charac-
ters can be used interchangeably.
An arithmetic expression uses the same syntax, precedence,
and associativity of expression as the C language. All the
C language operators that apply to floating point quantities
can be used. In addition, the operator ** can be used for
exponentiation. It has higher precedence than multiplica-
tion as is left associative. In addition, when the value of
an arithmetic variable or sub-expression can be represented
as a long integer, all C language integer arithmetic opera-
tions can be performed. Variables can be referenced by name
within an arithmetic expression without using the parameter
expansion syntax. When a variable is referenced, its value
is evaluated as an arithmetic expression.
The following math library functions can be used with an
arithmetic expression:
abs acos asin atan atan2 cos cosh exp floor fmod hypot int
log pow sin sinh sqrt tan tanh
An internal representation of a variable as a double preci-
sion floating point can be specified with the -E [n] or -F
[n] option of the typeset special built-in command. The -E
option causes the expansion of the value to be represented
using scientific notation when it is expanded. The optional
option argument n defines the number of significant figures.
The -F option causes the expansion to be represented as a
floating decimal number when it is expanded. The optional
option argument n defines the number of places after the
decimal point in this case.
RDS Standard Last change: User Environment Utilities 22
User Commands KSH(1)
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 sub-
stitution, 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
secondary prompt (i.e., the value of PS2) is issued.
Conditional Expressions.
A conditional expression is used with the [[ compound com-
mand 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 con-
structed 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
RDS Standard Last change: User Environment Utilities 23
User Commands KSH(1)
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 pro-
cess.
-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 terminal device.
-u file
True, if file exists and it has its setuid bit set.
-w file
True, if file exists and is writable by current pro-
cess.
-x file
True, if file exists and is executable by current pro-
cess. 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 effec-
tive 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
RDS Standard Last change: User Environment Utilities 24
User Commands KSH(1)
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. With the
string matches the pattern the .sh.match array variable
will contain the match and sub-pattern matches.
string1 < string2
True, if string1 comes before string2 based on ASCII
value of their characters.
string1 > string2
True, if string1 comes after string2 based on ASCII
value of their characters.
The following obsolete arithmetic comparisons are also per-
mitted:
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 primi-
tives by using any of the following, listed in decreasing
order of precedence.
(expression)
True, if expression is true. Used to group expres-
sions.
! 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 special 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,
RDS Standard Last change: User Environment Utilities 25
User Commands KSH(1)
parameter expansion, and arithmetic substitution occur
before word or digit is used except as noted below. File
name generation occurs only if the shell is interactive and
the pattern matches a single file. Field splitting is not
performed.
In each of the following redirections, if file is of the
form /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 or udp connection to the correspond-
ing socket.
No intervening space is allowed between the characters of
redirection operators.
<word Use file word as standard input (file descrip-
tor 0).
>word Use file word as standard output (file
descriptor 1). If the file does not exist
then it is created. If the file exists, and
the noclobber option is on, this causes an
error; otherwise, it is truncated to zero
length.
>|word 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 per-
formed 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, parame-
ter expansion, command substitution, and
arithmetic substitution occur, \new-line is
ignored, and \ must be used to quote the char-
acters \, $, `. If - is appended to <<, then
all leading tabs are stripped from word and
RDS Standard Last change: User Environment Utilities 26
User Commands KSH(1)
from the document.
<<<word A short form of here document in which word
becomes the contents of the here-document
after any parameter expansion, command substi-
tution, 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. Similarly for the standard
output using >&digit-.
<&- The standard input is closed. Similarly for
the standard output using >&-.
<&p The input from the co-process is moved to
standard input.
>&p The output to the co-process is moved to stan-
dard output.
<# Evaluate arithmetic expression expr and posi-
tion file descriptor 0 to the resulting value
bytes from the start of the file. The vari-
ables CUR and EOF evaluate to the current
offset and end-of-file offset respectively
when evaluating expr.
># The same as <# except applies to file descrip-
tor 1.
If one of the above is preceded by a digit, with no inter-
vening 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 descriptor 1 and
exec {n}<file
RDS Standard Last change: User Environment Utilities 27
User Commands KSH(1)
means open file named file for reading and store the file
descriptor number in variable n.
The order in which redirections are specified is signifi-
cant. The shell evaluates each redirection in terms of the
(file descriptor, file) association at the time of evalua-
tion. 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 redirec-
tions 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 standard input for the command is the empty
file /dev/null. Otherwise, the environment for the execu-
tion 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 vari-
ables 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 originally inherited by the shell, whose
values may be modified by the current shell, plus any addi-
tions 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 assign-
ments. 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 con-
cerned except for special built-in commands listed below -
those that are preceded with a dagger).
RDS Standard Last change: User Environment Utilities 28
User Commands KSH(1)
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 disappear someday.
Functions.
For historical reasons, there are two ways to define func-
tions, the name() syntax and the function name syntax,
described in the Commands section above. Shell functions
are read in and stored internally. Alias names are resolved
when the function is read. Functions are executed like com-
mands 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 function. They can be passed to functions that they
call in the variable assignment list the 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-
RDS Standard Last change: User Environment Utilities 29
User Commands KSH(1)
in command.
Ordinarily, functions are unset when the shell executes a
shell script. Functions that need to be defined across
separate invocations of the shell should be placed in a
directory and the FPATH variable should contain the name of
this directory. They 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 program-
ming interface extension 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 dis-
cipline function, the referenced 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 dis-
cipline, then that value is unchanged. If the unset discip-
line 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 discipline
function.
The variable .sh.name contains the name of the variable for
which the discipline function is called, .sh.subscript is
the subscript of the variable, and .sh.value will contain
the value being assigned inside the .set discipline func-
tion. 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 associates a job with each pipeline. It
keeps a table of current jobs, printed by the jobs command,
and assigns them small integer numbers. When a job is
started asynchronously with &, the shell prints a line which
looks like:
[1] 1234
indicating that the job which was started asynchronously was
job number 1 and had one (top-level) process, whose process
id was 1234.
RDS Standard Last change: User Environment Utilities 30
User Commands KSH(1)
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 manipu-
late the state of this job, putting it in the background
with the bg command, or run some other commands and then
eventually bring the job back into the foreground with the
foreground command fg. A ^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 giv-
ing the command stty tostop. If you set this tty option,
then background jobs will stop when they try to produce out-
put 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 com-
pletes 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 ter-
minated. 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.
RDS Standard Last change: User Environment Utilities 31
User Commands KSH(1)
Signals.
The INT and QUIT signals for an invoked command are ignored
if the command is followed by & and the monitor option is
not active. Otherwise, signals have the values inherited by
the shell from its parent (but see also the trap built-in
command below).
Execution.
Each time a command is read, the above substitutions are
carried out. If the command 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 argu-
ments 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 exe-
cuted. 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 directory. 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 vari-
able, 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 the this file con-
tains 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 . spe-
cial built-in command and a function of the given name is
executed. Otherwise, if found, a process is created and an
attempt is made to execute the command via exec(2).
RDS Standard Last change: User Environment Utilities 32
User Commands KSH(1)
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 specified 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 direc-
tory, then it specifies a directory relative to the direc-
tory that the executable 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 128) 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 edi-
tor 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.
RDS Standard Last change: User Environment Utilities 33
User Commands KSH(1)
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 edit-
ing option is automatically selected each time the VISUAL or
EDITOR variable is assigned a value ending in either of
these option names.
The editing features require that the user's terminal accept
`RETURN' as carriage return without line feed and that a
space (` ') must overwrite the current character on the
screen.
Unless the multiline option is on, the editing modes imple-
ment 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 win-
dow 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 opera-
tions are called command name listing and file name listing,
respectively. There are additional operations, referred to
as command name completion and file name completion, which
compute the list of matching commands or files, but instead
of printing the list, replace the current word with a com-
plete 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.
RDS Standard Last change: User Environment Utilities 34
User Commands KSH(1)
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 com-
mand name followed by a space.
Key Bindings.
The KEYBD trap can be used to intercept keys as they are
typed and change the characters that are actually seen by
the shell. This trap is executed after each character (or
sequence of characters when the first character is ESC) is
entered while reading from a terminal. The variable
.sh.edchar contains the character or character sequence
which generated the trap. Changing the value of .sh.edchar
in the trap action causes the shell to behave as if the new
value were entered from the keyboard rather than the origi-
nal 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 charac-
ter search.
Emacs Editing Mode.
This mode is entered by enabling either the emacs or gmacs
option. The only difference between these two modes is the
way they handle ^T. To edit, the user moves the cursor to
the point needing correction and then inserts or deletes
characters or words as needed. All the editing commands are
control characters or escape sequences. The notation for
control characters is caret (^) followed by the character.
For example, ^F is the notation for control F. This is
entered by depressing `f' while holding down the `CTRL'
(control) key. The `SHIFT' key is not depressed. (The
notation ^? indicates the DEL (delete) key.)
The notation for escape sequences is M- followed by a char-
acter. 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.
RDS Standard Last change: User Environment Utilities 35
User Commands KSH(1)
^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 consist-
ing 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 previ-
ous character.
^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 com-
mand will not work).
^T Transpose current character with previous charac-
ter and advance the cursor in emacs mode. Tran-
spose 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 numerical parameter whose value is
less than the current cursor position, then delete
from given position up to the cursor. If preceded
by a numerical parameter whose value is greater
than the current cursor position, then delete from
cursor up to given cursor position.
^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 termi-
nals).
^Y Restore last item removed from line. (Yank item
back to the line.)
RDS Standard Last change: User Environment Utilities 36
User Commands KSH(1)
^L Line feed and print current line.
^@ (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 ter-
minated 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 com-
mand line containing the most recent string is
accessed. In this case a parameter of zero rev-
erses the direction of the search.
^O Operate - Execute the current line and fetch the
next line relative to current line from the his-
tory 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. The can be used to program functions
keys on many terminals.
M-. The last word of the previous command is inserted
on the line. If preceded by a numeric parameter,
the value of this parameter determines which word
to insert rather than the last word.
M-_ Same as M-..
M-* Attempt file name generation on the current word.
An asterisk is appended if the word doesn't match
RDS Standard Last change: User Environment Utilities 37
User Commands KSH(1)
any file or contain any special pattern charac-
ters.
M-ESC Command or file name completion as described
above.
^I Command or file name completion as described
above.
M-= If not preceded by a numeric parameter, it gen-
erates 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 character's editing features (if any).
^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 charac-
ters 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 con-
trol characters or less than one second has elapsed since
the prompt was printed. The ESC character terminates canon-
ical 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 echo-
ing 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.
RDS Standard Last change: User Environment Utilities 38
User Commands KSH(1)
Input Edit Commands
By default the editor is in input mode.
erase (User defined erase character as defined by
the stty command, usually ^H or #.) Delete
previous character.
^W Delete the previous blank separated word. On
some systems the viraw option 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.
^V Escape next character. Editing characters
and the user's erase or kill characters may
be entered in a command line or in a search
string if preceded by a ^V. The ^V 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.
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 charac-
ter find command, f, F, t, or T.
[count], Reverses the last single character find com-
mand 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,
RDS Standard Last change: User Environment Utilities 39
User Commands KSH(1)
the remainder of the line is searched for the
first occurrence of one of the above charac-
ters first.
Search Edit Commands
These commands access your command history.
[count]k Fetch previous command. Each time k is
entered the previous command 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 forward 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 previ-
ous 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 $a.
[count]cmotion
c[count]motion
Delete current character through the charac-
ter that motion would move the cursor to and
enter input mode. If motion is c, the entire
line will be deleted and input mode entered.
C Delete the current character through the end
of line and enter input mode. Equivalent to
c$.
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$.
[count]dmotion
d[count]motion
Delete current character through the charac-
ter that motion would move to. If motion is
RDS Standard Last change: User Environment Utilities 40
User Commands KSH(1)
d , the entire line will be deleted.
i Enter input mode and insert text before the
current character.
I Insert text before the beginning of the line.
Equivalent to 0i.
[count]P Place the previous text modification before
the cursor.
[count]p Place the previous text modification after
the cursor.
R Enter input mode and replace characters on
the screen with characters you type overlay
fashion.
[count]rc Replace the count character(s) starting at
the current cursor position with c, and
advance the cursor.
[count]x Delete current character.
[count]X Delete preceding character.
[count]. Repeat the previous text modification com-
mand.
[count]~ Invert the case of the count character(s)
starting at the current cursor position and
advance the cursor.
[count]_ Causes the count word of the previous command
to be appended and input mode entered. The
last word is used if count is omitted.
* Causes an * to be appended to the current
word and file name generation attempted. If
no match is found, it rings the bell. Other-
wise, the word is replaced by the matching
pattern and input mode is entered.
\ Command or file name completion as described
above.
^I Command or file name completion as described
above.
Other Edit Commands
Miscellaneous commands.
[count]ymotion
y[count]motion
Yank current character through character that
motion would move the cursor to and puts them
into the delete buffer. The text and cursor
are unchanged.
yy Yanks the entire line.
Y Yanks from current position to end of line.
Equivalent to y$.
u Undo the last text modifying command.
U Undo all the text modifying commands per-
formed 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.
RDS Standard Last change: User Environment Utilities 41
User Commands KSH(1)
^L Line feed and print current line. Has effect
only in control mode.
^J (New line) Execute the current line, regard-
less 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 com-
mented commands in the history file.
[count]= If count is not specified, it generates the
list of matching commands 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 pro-
cess. Input/Output redirection is permitted. Unless other-
wise 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 - symbols are special
built-in commands and are treated specially in the following
ways:
1. Variable assignment lists preceding the command remain
in effect when the command completes.
2. I/O redirections are processed after variable assign-
ments.
3. Errors cause a script that contains them to abort.
4. They are not valid function names.
5. Words following a command preceded by ~-- that are in
the format of a variable assignment are expanded with
the same rules as a variable assignment. This means
that tilde substitution is performed after the = sign
and field splitting and file name generation are not
performed.
RDS Standard Last change: User Environment Utilities 42
User Commands KSH(1)
- : [ 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 positional
parameters are unchanged. The exit status is the exit
status of the last command executed.
~-- alias [ -ptx ] [ name[ =value ] ] ...
alias with no arguments prints the list of aliases in
the form name=value on standard output. The -p option
causes the word alias to be inserted before each one.
When one or more arguments are 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 con-
trol. Puts each specified 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 speci-
fied, the built-ins are printed on standard output.
The -s option prints only the special built-ins.
RDS Standard Last change: User Environment Utilities 43
User Commands KSH(1)
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. 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 omit-
ted. Once a library is loaded, its symbols become
available for subsequent invocations of builtin. Mul-
tiple libraries can be specified with separate invoca-
tions 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 func-
tion 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 variable PWD is set to the current directory. The
shell variable CDPATH defines the search path for the
directory containing arg. Alternative directory names
are separated by a colon (:). The default path is
<null> (specifying the current directory). 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.
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
RDS Standard Last change: User Environment Utilities 44
User Commands KSH(1)
refers to a special built-in, none of the special pro-
perties associated with the leading daggers will be
honored. (For example, the predefined alias
redirect='command exec' prevents a script from ter-
minating 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 invoca-
tion. 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 invocation. The exit status will be the max-
imum invocation exit status. With the -v option, com-
mand 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 contain 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
dependent 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 associ-
ated 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
RDS Standard Last change: User Environment Utilities 45
User Commands KSH(1)
that are opened with this mechanism are closed when
invoking another program.
- exit [ n ]
Causes the shell to exit with the exit status specified
by n. The value will be the least significant 8 bits
of the specified status. If n is omitted, then the
exit status is that of the last command executed. An
end-of-file 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 con-
trol. Each job specified is brought to the foreground
and waited for in the specified order. Otherwise, the
current job is brought into the foreground. See Jobs
for a description of the format of job.
getconf [ name [ pathname ] ]
Prints the current value of the configuration parameter
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 beginning with +
or - or the argument ~-- ends the options. Options
beginning with + are only recognized when optstring
begins with a +. optstring contains the letters that
getopts recognizes. If a letter is followed by a :,
RDS Standard Last change: User Environment Utilities 46
User Commands KSH(1)
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 mes-
sage 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 start-
ing 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. Otherwise, the editor program ename is invoked
on a file containing these keyboard commands. If ename
is not supplied, then the value of the variable
HISTEDIT is used. If HISTEDIT is not set, then FCEDIT
(default /bin/ed) is used as the editor. When editing
is complete, the edited command(s) is executed if the
changes have been saved. If last is not specified,
then it will be set to first. If first is not speci-
fied, the default is the previous command for editing
and -16 for listing. The option -r reverses the order
of the commands and the option -n suppresses command
numbers when listing. In the second form, command is
interpreted as first described 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 omitted. The -l option lists process
ids in addition to the normal information. The -n
RDS Standard Last change: User Environment Utilities 47
User Commands KSH(1)
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 speci-
fied signal to the specified jobs or processes. Sig-
nals 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 backward compatibility, the
n and s can be omitted and the number or name placed
immediately after the -. If the signal being sent is
TERM (terminate) or HUP (hangup), then the job or pro-
cess 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 corresponding signal number is listed.
For each sig that is a number, the signal name
corresponding to the least significant 8 bits of sig is
listed.
let arg ...
Each arg is a separate arithmetic expression to be
evaluated. See Arithmetic Evaluation above, for a
description of arithmetic expression evaluation.
The exit status is 0 if the value of the last expres-
sion is non-zero, and 1 otherwise.
- newgrp [ arg ... ]
Equivalent to exec /bin/newgrp arg ....
print [ -Renprs ] [ -u unit] [ -f format ] [ arg ... ]
With no options or with option - or ~--, each arg is
printed on standard output. The -f option causes the
arguments to be printed as described by printf. In
this case, any e, n, r, R options are ignored. Other-
wise, 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 argu-
ments 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).
RDS Standard Last change: User Environment Utilities 48
User Commands KSH(1)
\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 descrip-
tor 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 argu-
ments 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 vari-
able will be printed. This is most useful for variables
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 to be output as their entity
name. A %P format can be used instead of %s to cause
arg to be interpreted as an extended regular expression
and be printed as a shell pattern. A %R format can be
used instead of %s to cause arg 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
format can be use to treat an argument as a date/time
string and to format the date/time according to the
date-format as defined for the date(1) command. A %Z
format will output a byte whose value is 0. The preci-
sion field of the %d format can be followed by a . and
the output base.
pwd [ -LP ]
Outputs the value of the current working directory.
RDS Standard Last change: User Environment Utilities 49
User Commands KSH(1)
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.
unit] [ vname?prompt ] [ vname ... ]
read [ -Aprs ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u
The shell input mechanism. One line is read and is
broken up into fields using the characters in IFS as
separators. The escape character, \, is used to remove
any special meaning for the next character and for line
continuation. The -d option causes the read to con-
tinue 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 \ char-
acter is not treated specially. The first field is
assigned to the first vname, the second field to the
second vname, etc., with leftover fields assigned to
the last vname. When vname has the binary attribute
and -n or -N is specified, the bytes that are read are
stored directly into the variable. 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 specify 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 readonly 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
RDS Standard Last change: User Environment Utilities 50
User Commands KSH(1)
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.
[ arg ... ]
- set [ _CGabefhkmnopstuvx ] [ _o [ option ] ] ... [ _A vname ]
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 behavior.
-C Prevents redirection > from truncating existing
files. Files that are created are opened with
the O_EXCL mode. Requires >| to truncate a
file when turned on.
-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 wait-
ing for the next prompt.
-e If a command has a non-zero exit status, exe-
cute 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
RDS Standard Last change: User Environment Utilities 51
User Commands KSH(1)
interactive shells.
-o The following argument can be one of the fol-
lowing 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.
breacexpand
Sans as -B.
emacs Puts you in an emacs style in-line edi-
tor for command entry.
globstar
Same as -G.
gmacs Puts you in a gmacs style in-line edi-
tor 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 com-
pleted, and the return value will be
the value of the last non-zero command
to fail or zero of no command has
failed.
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
RDS Standard Last change: User Environment Utilities 52
User Commands KSH(1)
character 033. This puts you in con-
trol mode. A return sends the line.
viraw Each character is processed as it is
typed in vi mode.
xtrace Same as -x.
option settings are printed.
If no option name is supplied, then the current
-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 effec-
tive uid and gid to be set to the real uid and
gid.
-s Sort the positional parameters lexicographi-
cally.
-t (Obsolete). Exit after reading and executing
one command.
-u Treat unset parameters as an error when substi-
tuting.
-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 standard 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 second 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
RDS Standard Last change: User Environment Utilities 53
User Commands KSH(1)
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 signal. Trap commands
are executed in order of signal number. Any attempt to
set a trap on a signal that was ignored on entry to the
current shell is ineffective. If action is omitted and
the first sig is a number, or if action is -, then the
trap(s) for each sig are reset to their original
values. If action is the null string then this signal
is ignored by the shell and by the commands it invokes.
If sig is ERR then action 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 syn-
tax, 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 exe-
cuted 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 [ _AHflbnprtux ] [ _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 vari-
able 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. Sub-
scripts are strings rather than arithmetic expres-
sions.
-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 fig-
ures 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 map-
ping on non-UNIX machines.
RDS Standard Last change: User Environment Utilities 54
User Commands KSH(1)
-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 speci-
fied, then a line containing the function name
followed by a shell comment containing the line
number and path name of the file where this func-
tion 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 assign-
ing to an integer. If n is non-zero, it defines
the output arithmetic base, otherwise the output
base will be ten.
RDS Standard Last change: User Environment Utilities 55
User Commands KSH(1)
-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 reference a vari-
able 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 com-
mands. 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 attri-
butes 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 options 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
RDS Standard Last change: User Environment Utilities 56
User Commands KSH(1)
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 pro-
cess.
-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 symbolic
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 unas-
signed, 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, MAIL-
CHECK, OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _
removes their special meaning even if they are subse-
quently 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
RDS Standard Last change: User Environment Utilities 57
User Commands KSH(1)
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
options skips the search for functions. The -p option
does a path search for name even if name is an alias, a
function, or a reserved word. The -a option is similar
to the -v option but causes all interpretations of the
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/.profile, if either file exists. Next, for interac-
tive shells, commands are read from the file named by per-
forming parameter expansion, command substitution, and
arithmetic substitution on the value of the environment
variable ENV if the file exists. If the -s option is not
present and arg and a file by the name of arg exits, 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 res-
tricted shell.
RDS Standard Last change: User Environment Utilities 58
User Commands KSH(1)
-D A list of all double quoted strings that are pre-
ceded 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 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 environ-
ments 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:
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 interpreted.
When a command to be executed is found to be a shell pro-
cedure, rksh invokes ksh to execute it. Thus, it is possi-
ble to provide to the end-user shell procedures that have
access to the full power of the standard shell, while impos-
ing a limited menu of commands; this scheme assumes that the
end-user does not have write and execute permissions in the
same directory.
The net effect of these rules is that the writer of the
.profile has complete control over user actions, by perform-
ing 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 com-
mands (e.g., /usr/rbin) that can be safely invoked by rksh.
RDS Standard Last change: User Environment Utilities 59
User Commands KSH(1)
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 func-
tion 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/passwd
/etc/profile
/etc/suid_profile
$HOME/.profile
/tmp/sh*
/dev/null
SEE ALSO
cat(1), cd(1), chmod(1), cut(1), echo(1), emacs(1), env(1),
gmacs(1), newgrp(1), pfexec(1), stty(1), test(1), umask(1),
vi(1), dup(2), exec(2), fork(2), 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),
environ(7).
Morris I. Bolsky and David G. Korn, The New KornShell Com-
mand and Programming Language, 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 command to disappear from the history
file.
The built-in command . file reads the whole file before any
commands are executed. Therefore, alias and unalias
RDS Standard Last change: User Environment Utilities 60
User Commands KSH(1)
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 fore-
ground 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 expressions to prevent the comma from being
interpreted as the decimal point character in certain
locales.
RDS Standard Last change: User Environment Utilities 61
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