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ksh93, rksh93 - Korn Shell, a standard and restricted command and programming language
ksh93 [±abcefhikmnoprstuvxBCD] [-R file] [ ±o option] ...
[-] [arg ...]
rksh93 [±abcefhikmnoprstuvxBCD] [-R file] [±o option] ...
[-] [arg ...]
ksh93 is a command and programming language that executes commands read from a terminal or a file. rksh93 is a restricted version of the command interpreter ksh93. rksh93 is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell.
See Invocation for the meaning of arguments to the shell.
A metacharacter is defined as one of the following characters:
; & ( ) | < > NEWLINE SPACE TAB
A blank is a TAB or a SPACE.
An identifier is a sequence of letters, digits, or underscores starting with a letter or underscore. Identifiers are used as components of variable names.
A vname is a sequence of one or more identifiers separated by a period (.) and optionally preceded by a period (.). vnames are used as function and variable names.
A word is a sequence of characters from the character set defined by the current locale, excluding non-quoted metacharacters.
A command is a sequence of characters in the syntax of the shell language. The shell reads each command and carries out the desired action either directly or by invoking separate utilities. A built-in command is a command that is carried out by the shell itself without creating a separate process. Some commands are built-in purely for convenience and are not documented in this manual page. Built-ins that cause side effects in the shell environment and built-ins that are found before performing a path search (see Execution) are documented in this manual page. For historical reasons, some of these built-ins behave differently than other built-ins and are called special built-ins.
A simple-command is a list of variable assignments (see Variable Assignments) or a sequence of blank-separated words which can be preceded by a list of variable assignments. See the Environment section of this manual page.
The first word specifies the name of the command to be executed. Except as specified in this section, the remaining words are passed as arguments to the invoked command. The command name is passed as argument 0. See exec(2). The value of a simple-command is its exit status. If it terminates normally, its value is 0-255. If it terminates abnormally, its value is 256+signum. The name of the signal corresponding to the exit status can be obtained by way of the -l option of the kill built-in utility.
A pipeline is a sequence of one or more commands separated by |. The standard output of each command but the last is connected by a pipe(2) to the standard input of the next command. Each command, except possibly the last, is run as a separate process. The shell waits for the last command to terminate. The exit status of a pipeline is the exit status of the last command unless the pipefail option is enabled. Each pipeline can be preceded by the reserved word!. This causes the exit status of the pipeline to become 0 if the exit status of the last command is non-zero, and 1 if the exit status of the last command is 0.
A list is a sequence of one or more pipelines separated by ;, &, |&, &&, or ||, and optionally terminated by ;, &, or |&. Of these five symbols, ;, &, and |& have equal precedence, which is lower than that of && and ||. The symbols && and || also have equal precedence.
A semicolon (;) causes sequential execution of the preceding pipeline. An ampersand (&) causes asynchronous execution of the preceding pipeline, that is, the shell does not wait for that pipeline to finish. The symbol |& causes asynchronous execution of the preceding pipeline with a two-way pipe established to the parent shell. The standard input and output of the spawned pipeline can be written to and read from by the parent shell by applying the redirection operators <& and >& with arg p to commands and by using -p option of the built-in commands read and print. The symbol && (||) causes the list following it to be executed only if the preceding pipeline returns a zero (non-zero) value. One or more NEWLINEs can appear in a list instead of a semicolon, to delimit a command. The first item of the first pipeline of a list that is a simple command not beginning with a redirection, and not occurring within a while, until, or if list , can be preceded by a semicolon. This semicolon is ignored unless the showme option is enabled as described with the set built-in.
A command is either a simple-command or one of commands in the following list. Unless otherwise stated, the value returned by a command is that of the last simple-command executed in the command.
for vname [ in word ... ] ;do list ;done
(( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
select vname [ in word ... ] ;do list ;done
case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac
The ;; operator causes execution of case to terminate. If ;& is used in place of ;; the next subsequent list, if any, is executed.
if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
while list ;do list ;done
until list ;do list ;done
((expression))
(list;)
list is simply executed. Unlike the metacharacters, ( and ), { and } are reserved words and must occur at the beginning of a line or after a ; to be recognized.
[[ expression ]]
function varname { list ;}
varname () { list ;}
The body of the function is the list of commands between { and }. A function defined with the function varname syntax can also be used as an argument to the . special built-in command to get the equivalent behavior as if the varname() syntax were used to define it. See Functions.
time [ pipeline ]
The following reserved words are recognized as reserved only when they are the first word of a command and are not quoted:
case
do
done
else
elif
esac
for
fi
function
if
select
then
time
until
while
{ }
[[ ]]
!
One or more variable assignments can start a simple command or can be arguments to the typeset, export, or readonly special built-in commands. The syntax for an assignment is of the form:
varname=word
varname[word]=word
varname=(assignlist)
word ...
[word]=word ...
assignment ...
typeset [options] assignment ...
In addition, a += can be used in place of the = to signify adding to or appending to the previous value. When += is applied to an arithmetic type, word is evaluated as an arithmetic expression and added to the current value. When applied to a string variable, the value defined by word is appended to the value. For compound assignments, the previous value is not unset and the new values are appended to the current ones provided that the types are compatible.
A word beginning with # causes that word and all the following characters up to a NEWLINE to be commented, or ignored.
The first word of each command is replaced by the text of an alias if an alias for this word has been defined. An alias name consists of any number of characters excluding metacharacters, quoting characters, file expansion characters, parameter expansion characters, command substitution characters, and =. The replacement string can contain any valid shell script including the metacharacters listed in the Commands section. The first word of each command in the replaced text, other than any that are in the process of being replaced, are tested for aliases. If the last character of the alias value is a BLANK then the word following the alias is also checked for alias substitution.
Aliases can be used to redefine built-in commands but cannot be used to redefine the reserved words listed in the Commands section. Aliases can be created and listed with the alias command and can be removed with the unalias command.
Aliasing is performed when scripts are read, not while they are executed. For an alias to take effect, the alias definition command has to be executed before the command which references the alias is read. The following aliases are compiled into the shell but can be unset or redefined:
autoload='typeset -fu'
command='command '
fc=hist
float='typeset -lE'
functions='typeset -f'
hash='alias -t --'
history='hist -l'
integer='typeset -li'
nameref='typeset -n'
nohup='nohup '
r='hist -s'
redirect='command exec'
source='command .'
stop='kill -s STOP'
suspend='kill -s STOP $$'
times='{ { time;} 2>&1;}'
type='whence -v'
After alias substitution is performed, each word is checked to see if it begins with an unquoted tilde (~). For tilde substitution, word also refers to the word portion of parameter expansion. See Parameter Expansion.
If it does, the word up to a / is checked to see if it matches a user name in the password database. If a match is found, the ~ and the matched login name are replaced by the login directory of the matched user. If no match is found, the original text is left unchanged. A ~ by itself, or in front of a /, is replaced by $HOME. A ~ followed by a + or - is replaced by the value of $PWD and $OLDPWD respectively.
In addition, when expanding a variable assignment, tilde substitution is attempted when the value of the assignment begins with a ~, and when a ~ appears after a colon (:). The : also terminates a ~ login name.
The standard output from a command enclosed in parentheses preceded by a dollar sign ($) or a pair of grave accents (``) can be used as part or all of a word. Trailing NEWLINEs are removed. In the second (obsolete) form, the string between the quotes is processed for special quoting characters before the command is executed. See Quoting.
The command substitution $(cat file) can be replaced by the equivalent but faster $(<file). The command substitution $(n<#) expands to the current byte offset for file descriptor n.
An arithmetic expression enclosed in double parentheses preceded by a dollar sign ( $((arithmetic_expression))) is replaced by the value of the arithmetic expression within the double parentheses.
Process substitution is only available on versions of the UNIX operating system that support the /dev/fd directory for naming open files.
Each command argument of the form <(list) or >(list) runs process list asynchronously connected to some file in /dev/fd. The name of this file becomes the argument to the command. If the form with > is selected then writing on this file provides input for list. If < is used, then the file passed as an argument contains the output of the list process.
For example,
paste <(cut -f1 file1) <(cut -f3 file2) | tee \
>(process1) >(process2)
cuts fields 1 and 3 from the files file1 and file2 respectively, pastes the results together, and sends it to the processes process1 and process2. It also displays the results to the standard output. The file, which is passed as an argument to the command, is a UNIX pipe(2). Programs that expect to lseek(2) on the file do not work.
A parameter is a variable, one or more digits, or any of the characters *, @, #, ?, -, $, and !. A variable is denoted by a vname. To create a variable whose vname contains a ., a variable whose vname consists of everything before the last . must already exist. A variable has a value and zero or more attributes. Variables can be assigned values and attributes by using the typeset special built-in command. The attributes supported by the shell are described later with the typeset special built-in command. Exported variables pass values and attributes to the environment.
The shell supports both indexed and associative arrays. An element of an array variable is referenced by a subscript. A subscript for an indexed array is denoted by an arithmetic expression, (see Arithmetic Evaluation), between a [ and a ]. Use set -A vname value ... to assign values to an indexed array. The value of all subscripts must be in the range of 0 through 1,048,575. Indexed arrays do not need to be declared. Any reference to a variable with a valid subscript is legal and an array is created if necessary.
An associative array is created with the -A option to typeset. A subscript for an associative array is denoted by a string enclosed between [ and ].
Referencing any array without a subscript is equivalent to referencing the array with subscript 0.
The value of a variable can be assigned by:
vname=value [vname=value] ...
or
vname[subscript]=value [vname[subscript]=value] ...
No space is allowed before or after the =. A nameref is a variable that is a reference to another variable. A nameref is created with the -n attribute of typeset. The value of the variable at the time of the typeset command becomes the variable that is referenced whenever the nameref variable is used. The name of a nameref cannot contain a dot (.). When a variable or function name contains a ., and the portion of the name up to the first . matches the name of a nameref, the variable referred to is obtained by replacing the nameref portion with the name of the variable referenced by the nameref. If a nameref is used as the index of a for loop, a name reference is established for each item in the list. A nameref provides a convenient way to refer to the variable inside a function whose name is passed as an argument to a function. For example, if the name of a variable is passed as the first argument to a function, the command
typeset -n var=$1
inside the function causes references and assignments to var to be references and assignments to the variable whose name has been passed to the function. If either of the floating point attributes, -E, or -F, or the integer attribute, -i, is set for vname, then the value is subject to arithmetic evaluation as described in this manual page. Positional parameters, parameters denoted by a number, can be assigned values with the set special built-in command. Parameter $0 is set from argument zero when the shell is invoked. The character $ is used to introduce substitutable parameters.
${parameter}
${#parameter}
${#vname[*]}
${#vname[@]}
${!vname}
${!vname[subscript]}
${!prefix*}
${parameter:-word}
word is not evaluated unless it is to be used as the substituted string.
In the following example, pwd is executed only if d is not set or is NULL:
print ${d:-$(pwd)}
If the colon (: ) is omitted from the expression, the shell only checks whether parameter is set or not.
${parameter:=word}
word is not evaluated unless it is to be used as the substituted string.
In the following example, pwd is executed only if d is not set or is NULL:
print ${d:-$(pwd)}
If the colon (:) is omitted from the expression, the shell only checks whether parameter is set or not.
${parameter:?word}
word is not evaluated unless it is to be used as the substituted string.
In the following example, pwd is executed only if d is not set or is NULL:
print ${d:-$(pwd)}
If the colon (: ) is omitted from the expression, the shell only checks whether parameter is set or not.
${parameter:+word}
word is not evaluated unless it is to be used as the substituted string.
In the following example, pwd is executed only if d is not set or is NULL:
print ${d:-$(pwd)}
If the colon (:) is omitted from the expression, the shell only checks whether parameter is set or not.
${parameter:offset:length}
${parameter:offset}
In the second form, the remainder of the value is used. A negative offset counts backwards from the end of parameter.
One or more BLANKs is required in front of a minus sign to prevent the shell from interpreting the operator as :-. If parameter is * or @, or is an array name indexed by * or @, then offset and length refer to the array index and number of elements respectively. A negative offset is taken relative to one greater than the highest subscript for indexed arrays. The order for associative arrays is unspecified.
${parameter#pattern}
${parameter##pattern}
${parameter%pattern}
${parameter%%pattern}
${parameter/pattern/string}
${parameter//pattern/string}
${parameter/#pattern/string}
${parameter/%pattern/string}
When string is null, the pattern is deleted and the / in front of string can be omitted. When parameter is @, *, or an array variable with subscript @ or *, the substitution operation is applied to each element in turn. In this case, the string portion of word is re-evaluated for each element.
In the first form, only the first occurrence of pattern is replaced.
In the second form, each match for pattern is replaced by the specified string.
The third form restricts the pattern match to the beginning of the string.
The fourth form restricts the pattern match to the end of the string.
The following parameters are automatically set by the shell:
#
-
?
$
_
This parameter is not set for commands which are asynchronous. This parameter is also used to hold the name of the matching MAIL file when checking for mail.
!
.sh.command
.sh.edchar
.sh.edcol
.sh.edmode
.sh.edtext
.sh.file
.sh.fun
.sh.match
.sh.name
.sh.subscript
.sh.subshell
.sh.value
.sh.version
LINENO
OLDPWD
OPTARG
OPTIND
PPID
PWD
RANDOM
REPLY
SECONDS
The following variables are used by the shell:
CDPATH
COLUMNS
EDITOR
See the set command in the Special Command section of this manual page.
ENV
See the Invocation section of this manual page.
ENV is not set by the shell.
FCEDIT
The shell specifies a default value to FCEDIT.
FIGNORE
FPATH
HISTCMD
HISTEDIT
HISTFILE
HISTSIZE
HOME
HOME is not set by the shell. HOME is set by login(1).
IFS
Each single occurrence of an IFS character in the string to be split, that is not in the issspace character class, and any adjacent characters in IFS that are in the issspace character class, delimit a field. One or more characters in IFS that belong to the issspace character class, delimit a field. In addition, if the same issspace character appears consecutively inside IFS, this character is treated as if it were not in the issspace class, so that if IFS consists of two tab characters, then two adjacent tab characters delimit a null field.
The shell specifies a default value to IFS.
LANG
LC_ALL
LC_COLLATE
LC_CTYPE
LC_NUMERIC
LINES
MAIL is not set by the shell. On some systems, MAIL is set by login(1).
MAILCHECK
The shell specifies a default value to MAILCHECK.
MAILPATH
PATH
The shell specifies a default value to PATH.
PS1
The shell specifies a default value to PS1.
PS2
The shell specifies a default value to PS2.
PS3
The shell specifies a default value to PS3.
PS4
The shell specifies a default value to PS4.
SHELL
SHELL is not set by the shell. On some systems, SHELL is set by login(1).
TIMEFORMAT
The format sequences and their meanings are as follows.
%%
%[p][l]R
%[p][l]U
%[p][l]S
%P
The braces denote optional portions. The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point can be displayed. Values of p greater than 3 are treated as 3. If p is not specified, the value 3 is used.
The optional l specifies a longer format, including hours if greater than zero, minutes, and seconds of the form HHhMMmSS.FFs. The value of p determines whether or not the fraction is included.
All other characters are output without change and a trailing NEWLINE is added. If unset, the default value, $'eal %2lRser %2lUys%2lS', is used. If the value is null, no timing information is displayed.
TMOUT
The shell specifies a default value to TMOUT.
VISUAL
After parameter expansion and command substitution, the results of substitutions are scanned for the field separator characters (those found in IFS) and split into distinct fields where such characters are found. Explicit null fields ("" or '') are retained. Implicit null fields, those resulting from parameters that have no values or command substitutions with no output, are removed.
If the braceexpand (-B) option is set, each of the fields resulting from IFS are checked to see if they contain one or more of the brace patterns. Valid brace patterns: {*,*}, {l1..l2} , {n1..n2}, {n1..n2%fmt} {n1..n2 ..n3}, or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are letters and n1,n2,n3 are signed numbers and fmt is a format specified as used by printf. In each case, fields are created by prepending the characters before the { and appending the characters after the } to each of the strings generated by the characters between the { and }. The resulting fields are checked to see if they have any brace patterns.
In the first form, a field is created for each string between { and ,, between , and ,, and between , and }. The string represented by * can contain embedded matching { and } without quoting. Otherwise, each { and } with * must be quoted.
In the second form, l1 and l2 must both be either upper case or both be lower case characters in the C locale. In this case a field is created for each character from l1 through l2.
In the remaining forms, a field is created for each number starting at n1. This continues until it reaches n2 and increments n1 by n3. The cases where n3 is not specified behave as if n3 were 1 if n1<=n2, and -1 otherwise. In forms which specify %fmt, any format flags, widths and precisions can be specified and fmt can end in any of the specifiers cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8 fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx, and z4cx.
Following splitting, each field is scanned for the characters *, ?, (, and [, unless the -f option has been set. If one of these characters appears, then the word is regarded as a pattern.
Each file name component that contains any pattern character is replaced with a lexicographically sorted set of names that matches the pattern from that directory. If no file name is found that matches the pattern, then that component of the file name is left unchanged unless the pattern is prefixed with ~(N) in which case it is removed. If FIGNORE is set, then each file name component that matches the pattern defined by the value of FIGNORE is ignored when generating the matching file names. The names . and .. are also ignored. If FIGNORE is not set, the character . at the start of each file name component is ignored unless the first character of the pattern corresponding to this component is the character . itself. For other uses of pattern matching the / and . are not specially treated.
*
?
[...]
alnum alpha blank cntrl digit graph lower print punct space upper word xdigit
word is equivalent to alnum plus the character _. Within [ and ], an equivalence class can be specified with the syntax [=c=] which matches all characters with the same primary collation weight (as defined by the current locale) as the character c. Within [ and ], [.symbol.] matches the collating symbol symbol.
A pattern-list is a list of one or more patterns separated from each other with an & or |. An & signifies that all patterns must be matched whereas | requires that only one pattern be matched. Composite patterns can be formed with one or more of the following sub-patterns:
?(pattern-list)
*(pattern-list)
+(pattern-list)
{n(pattern-list)
{m,n(pattern-list)
@(pattern-list)
!(pattern-list)
By default, each pattern, or sub-pattern matches the longest string possible consistent with generating the longest overall match. If more than one match is possible, the one starting closest to the beginning of the string is chosen. However, for each of the compound patterns a - can be inserted in front of the ( to cause the shortest match to the specified pattern-list to be used.
When pattern-list is contained within parentheses, the backslash character \ is treated specially even when inside a character class. All ANSI-C character escapes are recognized and match the specified character. In addition the following escape sequences are recognized:
\d
\D
\s
\S
\w
\W
A pattern of the form %(pattern-pairs) is a sub-pattern that can be used to match nested character expressions. Each pattern-pair is a two character sequence which cannot contain & or |. The first pattern-pair specifies the starting and ending characters for the match. Each subsequent pattern-pair represents the beginning and ending characters of a nested group that is skipped over when counting starting and ending character matches. The behavior is unspecified when the first character of a pattern-pair is alphanumeric except for the following:
D
E
L
Q
%({}Q"E\), matches characters starting at { until the matching } is found not counting any { or } that is inside a double quoted string or preceded by the escape character \. Without the {} this pattern matches any C language string.
Each sub-pattern in a composite pattern is numbered, starting at 1, by the location of the ( within the pattern. The sequence \n, where n is a single digit and \n comes after the nth. sub-pattern, matches the same string as the sub-pattern itself.
A pattern can contain sub-patterns of the form ~(options:pattern-list), where either options or :pattern-list can be omitted. Unlike the other compound patterns, these sub-patterns are not counted in the numbered sub-patterns. If options is present, it can consist of one or more of the following:
+
-
E
F
g
This is the default.
G
i
K
This is the default.
l
This is the default for K style patterns.
N
r
This is the default for K style patterns.
If both options and :pattern-list are specified, then the options apply only to pattern-list. Otherwise, these options remain in effect until they are disabled by a subsequent ~(...) or at the end of the sub-pattern containing ~(...).
Each of the metacharacters listed in the Definitions has a special meaning to the shell.
g
i
If both options and :pattern-list are specified, then the options apply only to pattern-list. Otherwise, the options remain in effect until they are disabled by a subsequent ~(...) or at the end of the sub-pattern containing ~(...).
Each of the metacharacters listed in the Definitions section of this manual page has a special meaning to the shell and causes termination of a word unless quoted. A character can be quoted, that is, made to stand for itself, by preceding it with a backslash (\). The pair \NEWLINE is removed. All characters enclosed between a pair of single quote marks ('') that is not preceded by a $ are quoted. A single quote cannot appear within the single quotes. A single quoted string preceded by an unquoted $ is processed as an ANSI-C string except for the following:
\0
\cx
\C[.name.]
\e
\E
Inside double quote marks (""), parameter and command substitution occur and \ quotes the characters \, `, ", and $. A $ in front of a double quoted string is ignored in the C or POSIX locale, and might cause the string to be replaced by a locale specific string otherwise. The meaning of $* and $@ is identical when not quoted or when used as a variable assignment value or as a file name. However, when used as a command argument, "$*" is equivalent to "$1d$2d...", where d is the first character of the IFS variable, whereas "$@" is equivalent to "$1" "$2" .... Inside grave quote marks (``), \fR quotes the characters \, `, and $. If the grave quotes occur within double quotes, then \ also quotes the character ".
The special meaning of reserved words or aliases can be removed by quoting any character of the reserved word. The recognition of function names or built-in command names cannot be altered by quoting them.
The shell performs arithmetic evaluation for arithmetic substitution, to evaluate an arithmetic command, to evaluate an indexed array subscript, and to evaluate arguments to the built-in commands shift and let. Arithmetic evaluation is also performed on argument operands of the built-in command printf that correspond to numeric format specifiers in the format operand. See printf(1). Evaluations are performed using double precision floating point arithmetic or long double precision floating point for systems that provide this data type. Floating point constants follow the ANSI-C programming language floating point conventions. Integer constants follow the ANSI-C programming language integer constant conventions although only single byte character constants are recognized and character casts are not recognized. Constants can be of the form [base#]n where base is a decimal number between two and sixty-four representing the arithmetic base and n is a number in that base. The digits greater than 9 are represented by the lower case letters, the upper case letters, @, and _ respectively. For bases less than or equal to 36, upper and lower case characters can be used interchangeably.
An arithmetic expression uses the same syntax, precedence, and associativity of expression as the C language. All the C language operators that apply to floating point quantities can be used. In addition, the operator ** can be used for exponentiation. It has higher precedence than multiplication and is left associative. When the value of an arithmetic variable or subexpression can be represented as a long integer, all C language integer arithmetic operations can be performed. Variables can be referenced by name within an arithmetic expression without using the parameter expansion syntax. When a variable is referenced, its value is evaluated as an arithmetic expression.
Any of the following math library functions that are in the C math library can be used within an arithmetic expression:
abs acos acosh asin asinh atan atan2 atanh cbrt copysign cos cosh erf erfc exp exp2 expm1 fabs fdim finite floor fma fmax fmod hypot ilogb int isinf isnan lgamma log log2 logb nearbyint nextafter nexttoward pow remainder rint round sin sinh sqrt tan tanh tgamma trunc
An internal representation of a variable as a double precision floating point can be specified with the -E [n] or -F [n] option of the typeset special built-in command. The -E option causes the expansion of the value to be represented using scientific notation when it is expanded. The optional option argument n defines the number of significant figures. The -F option causes the expansion to be represented as a floating decimal number when it is expanded. The optional option argument n defines the number of places after the decimal point in this case.
An internal integer representation of a variable can be specified with the -i [n] option of the typeset special built-in command. The optional option argument n specifies an arithmetic base to be used when expanding the variable. If you do not specify an arithmetic base, base 10 is used.
Arithmetic evaluation is performed on the value of each assignment to a variable with the -E, -F, or -i option. Assigning a floating point number to a variable whose type is an integer causes the fractional part to be truncated.
When used interactively, the shell prompts with the value of PS1 after expanding it for parameter expansion, command substitution, and arithmetic substitution, before reading a command. In addition, each single ! in the prompt is replaced by the command number. A !! is required to place ! in the prompt. If at any time a NEWLINE is typed and further input is needed to complete a command, then the secondary prompt, that is, the value of PS2, is issued.
A conditional expression is used with the [[ compound command to test attributes of files and to compare strings. Field splitting and file name generation are not performed on the words between [[ and ]].
Each expression can be constructed from one or more of the following unary or binary expressions:
-a file
This option is the same as -e. This option is obsolete.
-b file
-c file
-d file
-e file
-f file
-g file
-G file
-h file
-k file
-L file
-n string
-N file
-o option
-o ?option
-O file
-p file
-r file
-s file
-S file
-t fildes
-u file
-w file
-x file
-z string
file1 -ef file2
file1 -nt file2
file1 -ot file2
string
string == pattern
string = pattern
string != pattern
string =~ ere
string1 < string2
string1 > string2
In each of the following expressions, if file is of the form /dev/fd/n, where n is an integer, the test is applied to the open file whose descriptor number is n. The following obsolete arithmetic comparisons are supported:
exp1 -eq exp2
exp1 -ge exp2
exp1 -gt exp2
exp1 -le exp2
exp1 -lt exp2
exp1 -ne exp2
A compound expression can be constructed from these primitives by using any of the following, listed in decreasing order of precedence:
(expression)
! expression
expression1 && expression2
expression1 || expression2
Before a command is executed, its input and output can be redirected using a special notation interpreted by the shell. The following can appear anywhere in a simple command or can precede or follow a command and are not passed on to the invoked command. Command substitution, parameter expansion, and arithmetic substitution occur before word or digit is used except as noted in this section. File name generation occurs only if the shell is interactive and the pattern matches a single file. Field splitting is not performed.
In each of the following redirections, if file is of the form /dev/sctp/host/port, /dev/tcp/host/port, or /dev/udp/host/port, where host is a hostname or host address, and port is a service specified by name or an integer port number, then the redirection attempts to make a tcp, sctp or udp connection to the corresponding socket.
No intervening space is allowed between the characters of redirection operators.
<word
>word
>|word
>>word
<>word
<<[-]word
<<<word
<&digit
<&digit-
<&-
<&p
>&p
<#((expr))
>#((expr))
<#pattern
<##pattern
If one of the redirection operators is preceded by a digit, with no intervening space, then the file descriptor number referred to is that specified by the digit (instead of the default 0 or 1). If one of the redirection operators other than >&- and the ># and <# forms, is preceded by {varname} with no intervening space, then a file descriptor number > 10 is selected by the shell and stored in the variable varname. If >&- or the any of the ># and <# forms is preceded by {varname} the value of varname defines the file descriptor to close or position. For example:
... 2>&1
means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and
exec [n]<file
means open file for reading and store the file descriptor number in variable n. The order in which redirections are specified is significant. The shell evaluates each redirection in terms of the (file_descriptor, file) association at the time of evaluation. For example:
... 1>fname 2>&1
first associates file descriptor 1 with file fname. It then associates file descriptor 2 with the file associated with file descriptor 1, that is, fname. If the order of redirections were reversed, file descriptor 2 would be associated with the terminal (assuming file descriptor 1 had been) and then file descriptor 1 would be associated with file fname. If a command is followed by & and job control is not active, the default standard input for the command is the empty file /dev/null. Otherwise, the environment for the execution of a command contains the file descriptors of the invoking shell as modified by input and output specifications.
The environment is a list of name-value pairs that is passed to an executed program in the same way as a normal argument list. See environ(5).
The names must be identifiers and the values are character strings. The shell interacts with the environment in several ways. On invocation, the shell scans the environment and creates a variable for each name found, giving it the corresponding value and attributes and marking it export. Executed commands inherit the environment. If the user modifies the values of these variables or creates new ones, using the export or typeset -x commands, they become part of the environment. The environment seen by any executed command is thus composed of any name-value pairs originally inherited by the shell, whose values can be modified by the current shell, plus any additions which must be noted in export or typeset -x commands. The environment for any simple-command or function can be augmented by prefixing it with one or more variable assignments. A variable assignment argument is a word of the form identifier=value. Thus:
TERM=450 cmd args
and
(export TERM; TERM=450; cmd args)
are equivalent (as far as the execution of cmd is concerned except for special built-in commands listed in the Built-Ins section, those that are preceded with a dagger. If the obsolete -k option is set, all variable assignment arguments are placed in the environment, even if they occur after the command name.
The following example first prints a=b c and then c:
echo a=b c set -k echo a=b c
This feature is intended for use with scripts written for early versions of the shell and its use in new scripts is strongly discouraged.
For historical reasons, there are two ways to define functions, the name() syntax and the function name syntax. These are described in the Commands section of this manual page.
Shell functions are read in and stored internally. Alias names are resolved when the function is read. Functions are executed like commands with the arguments passed as positional parameters. See the Execution section of this manual page for details.
Functions defined by the function name syntax and called by name execute in the same process as the caller and share all files and present working directory with the caller. Traps caught by the caller are reset to their default action inside the function. A trap condition that is not caught or ignored by the function causes the function to terminate and the condition to be passed on to the caller. A trap on EXIT set inside a function is executed in the environment of the caller after the function completes. Ordinarily, variables are shared between the calling program and the function. However, the typeset special built-in command used within a function defines local variables whose scope includes the current function. They can be passed to functions that they call in the variable assignment list that precedes the call or as arguments passed as name references. Errors within functions return control to the caller.
Functions defined with the name() syntax and functions defined with the function name syntax that are invoked with the . special built-in are executed in the caller's environment and share all variables and traps with the caller. Errors within these function executions cause the script that contains them to abort.
The special built-in command return is used to return from function calls.
Function names can be listed with the -f or +f option of the typeset special built-in command. The text of functions, when available, is also listed with -f. Functions can be undefined with the -f option of the unset special built-in command.
Ordinarily, functions are unset when the shell executes a shell script. Functions that need to be defined across separate invocations of the shell should be placed in a directory and the FPATH variable should contain the name of this directory. They can also be specified in the ENV file.
Each variable can have zero or more discipline functions associated with it. The shell initially understands the discipline names get, set, append, and unset but on most systems others can be added at run time via the C programming interface extension provided by the builtin built-in utility. If the get discipline is defined for a variable, it is invoked whenever the specified variable is referenced. If the variable .sh.value is assigned a value inside the discipline function, the referenced variable is evaluated to this value instead. If the set discipline is defined for a variable, it is invoked whenever the specified variable is assigned a value. If the append discipline is defined for a variable, it is invoked whenever a value is appended to the specified variable. The variable .sh.value is specified the value of the variable before invoking the discipline, and the variable is assigned the value of .sh.value after the discipline completes. If .sh.value is unset inside the discipline, then that value is unchanged. If the unset discipline is defined for a variable, it is invoked whenever the specified variable is unset. The variable is not unset unless it is unset explicitly from within this discipline function.
The variable .sh.name contains the name of the variable for which the discipline function is called, .sh.subscript is the subscript of the variable, and .sh.value contains the value being assigned inside the set discipline function. For the set discipline, changing .sh.value changes the value that gets assigned.
If the monitor option of the set command is turned on, an interactive shell associates a job with each pipeline. It keeps a table of current jobs, printed by the jobs command, and assigns them small integer numbers. When a job is started asynchronously with &, the shell prints a line which looks like:
[1] 1234
indicating that the job which was started asynchronously was job number 1 and had one (top-level) process, whose process id was 1234.
If you are running a job and wish to stop it, CTRL-z sends a STOP signal to the current job. The shell normally displays a message that the job has been stopped, and displays another prompt. You can then manipulate the state of this job, putting it in the background with the bg command, or run some other commands and then eventually bring the job back into the foreground with the foreground command fg. A CTRL-z takes effect immediately and is like an interrupt in that pending output and unread input are discarded when it is typed.
A job being run in the background stops if it tries to read from the terminal. Background jobs are normally allowed to produce output, but this can be disabled by giving the command sttytostop. If you set this tty option, then background jobs stop when they try to produce output like they do when they try to read input.
There are several ways to refer to jobs in the shell. A job can be referred to by the process id of any process of the job or by one of the following:
%number
%string
%?string
%%
%+
%-
The shell learns immediately whenever a process changes state. It normally informs you whenever a job becomes blocked so that no further progress is possible, but only just before it prints a prompt. This is done so that it does not otherwise disturb your work. The notify option of the set command causes the shell to print these job change messages as soon as they occur.
When the monitor option is on, each background job that completes triggers any trap set for CHLD.
When you try to leave the shell while jobs are running or stopped, you are warned that You have stopped(running) jobs. You can use the jobs command to see what they are. If you immediately try to exit again, the shell does not warn you a second time, and the stopped jobs are terminated. When a login shell receives a HUP signal, it sends a HUP signal to each job that has not been disowned with the disown built-in command.
The INT and QUIT signals for an invoked command are ignored if the command is followed by & and the monitor option is not active. Otherwise, signals have the values inherited by the shell from its parent. See the trap built-in command.
Each time a command is read, the substitutions are carried out. If the command name matches one of the ones in the Special Built-in Commands section of this manual page, it is executed within the current shell process. Next, the command name is checked to see if it matches a user defined function. If it does, the positional parameters are saved and then reset to the arguments of the function call. A function is also executed in the current shell process. When the function completes or issues a return, the positional parameter list is restored. For functions defined with the function name syntax, any trap set on EXIT within the function is executed. The exit value of a function is the value of the last command executed. If a command name is not a special built-in command or a user defined function, but it is one of the built-in commands, it is executed in the current shell process.
The shell variable PATH defines the search path for the directory containing the command. Alternative directory names are separated by a colon (:). The default path is /bin:/usr/bin:, specifying /bin, /usr/bin, and the current directory in that order. The current directory can be specified by two or more adjacent colons, or by a colon at the beginning or end of the path list. If the command name contains a slash (/), the search path is not used. Otherwise, each directory in the path is searched for an executable file of the specified name that is not a directory. If found, and if the shell determines that there is a built-in version of a command corresponding to a specified pathname, this built-in is invoked in the current process. If found, and this directory is also contained in the value of the FPATH variable, then this file is loaded into the current shell environment as if it were the argument to the . command except that only preset aliases are expanded, and a function of the specified name is executed as described in this manual page. If not found, and the file .paths is found, and this file contains a line of the form FPATH=path where path is an existing directory, and this directory contains a file of the specified name, then this file is loaded into the current shell environment as if it were the argument to the . special built-in command and a function of the specified name is executed. Otherwise, if found, a process is created and an attempt is made to execute the command using exec(2).
When an executable is found, the directory where it is found in is searched for a file named .paths. If this file is found and it contains a line of the form BUILTIN_LIB=value, the library named by value is searched for as if it were an option argument to builtin -f, and if it contains a built-in of the specified name this is executed instead of a command by this name. Otherwise, if this file is found and it contains a line of the form name=value in the first or second line, then the environment variable name is modified by prepending the directory specified by value to the directory list. If value is not an absolute directory, then it specifies a directory relative to the directory that the executable was found. If the environment variable name does not already exist it is added to the environment list for the specified command.
If the file has execute permission but is not an a.out file, it is assumed to be a file containing shell commands. A separate shell is spawned to read it. All non-exported variables are removed in this case. If the shell command file doesn't have read permission, and/or if the setuid and setgid bits are set on the file, then the shell executes an agent whose job it is to set up the permissions and execute the shell with the shell command file passed down as an open file. A parenthesized command is executed in a sub-shell without removing non-exported variables.
The text of the last HISTSIZE (default 512) commands entered from a terminal device is saved in a history file. The file $HOME/.sh_history is used if the HISTFILE variable is not set or if the file it names is not writable. A shell can access the commands of all interactive shells which use the same named HISTFILE. The built-in command hist is used to list or edit a portion of this file. The portion of the file to be edited or listed can be selected by number or by giving the first character or characters of the command. A single command or range of commands can be specified. If you do not specify an editor program as an argument to hist then the value of the variable HISTEDIT is used. If HISTEDIT is unset, the obsolete variable FCEDIT is used. If FCEDIT is not defined, then /bin/ed is used. The edited commands are printed and executed again upon leaving the editor unless you quit without writing. The -s option (and in obsolete versions, the editor name -) is used to skip the editing phase and to re-execute the command. In this case a substitution parameter of the form old=newcan be used to modify the command before execution. For example, with the preset alias r, which is aliased to 'hist -s', typing `r bad=good c' re-executes the most recent command which starts with the letter c, replacing the first occurrence of the string bad with the string good.
Normally, each command line entered from a terminal device is simply typed followed by a NEWLINE (RETURN or LINE FEED). If either the emacs, gmacs, or vi option is active, the user can edit the command line. To be in either of these edit modes set the corresponding option. An editing option is automatically selected each time the VISUAL or EDITOR variable is assigned a value ending in either of these option names.
The editing features require that the user's terminal accept RETURN as carriage return without line feed and that a SPACE must overwrite the current character on the screen.
Unless the multiline option is on, the editing modes implement a concept where the user is looking through a window at the current line. The window width is the value of COLUMNS if it is defined, otherwise 80. If the window width is too small to display the prompt and leave at least 8 columns to enter input, the prompt is truncated from the left. If the line is longer than the window width minus two, a mark is displayed at the end of the window to notify the user. As the cursor moves and reaches the window boundaries the window is centered about the cursor. The mark is a > (<, *) if the line extends on the right , left, or both sides of the window.
The search commands in each edit mode provide access to the history file. Only strings are matched, not patterns, although a leading ^ in the string restricts the match to begin at the first character in the line.
Each of the edit modes has an operation to list the files or commands that match a partially entered word. When applied to the first word on the line, or the first word after a ;, |, &, or (, and the word does not begin with ~ or contain a /, the list of aliases, functions, and executable commands defined by the PATH variable that could match the partial word is displayed. Otherwise, the list of files that match the specified word is displayed. If the partially entered word does not contain any file expansion characters, a * is appended before generating these lists. After displaying the generated list, the input line is redrawn. These operations are called command name listing and file name listing, respectively. There are additional operations, referred to as command name completion and file name completion, which compute the list of matching commands or files, but instead of printing the list, replace the current word with a complete or partial match. For file name completion, if the match is unique, a / is appended if the file is a directory and a space is appended if the file is not a directory. Otherwise, the longest common prefix for all the matching files replaces the word. For command name completion, only the portion of the file names after the last / are used to find the longest command prefix. If only a single name matches this prefix, then the word is replaced with the command name followed by a space. When using a TAB for completion that does not yield a unique match, a subsequent TAB provides a numbered list of matching alternatives. A specific selection can be made by entering the selection number followed by a TAB.
The KEYBD trap can be used to intercept keys as they are typed and change the characters that are actually seen by the shell. This trap is executed after each character (or sequence of characters when the first character is ESC) is entered while reading from a terminal.
The variable .sh.edchar contains the character or character sequence which generated the trap. Changing the value of .sh.edchar in the trap action causes the shell to behave as if the new value were entered from the keyboard rather than the original value. The variable .sh.edcol is set to the input column number of the cursor at the time of the input. The variable .sh.edmode is set to ESC when in vi insert mode and is null otherwise. By prepending ${.sh.editmode} to a value assigned to .sh.edchar it causes the shell to change to control mode if it is not already in this mode.
This trap is not invoked for characters entered as arguments to editing directives, or while reading input for a character search.
This mode is entered by enabling either the emacs or gmacs option. The only difference between these two modes is the way they handle ^T. To edit, the user moves the cursor to the point needing correction and then inserts or deletes characters or words as needed. All the editing commands are control characters or escape sequences. The notation for control characters is caret (^) followed by the character.
For example, ^F is the notation for CTRL/F. This is entered by depressing f while holding down the CTRL (control) key. The SHIFT key is not depressed. (The notation ^? indicates the DEL (delete) key.)
The notation for escape sequences is M- followed by a character. For example, M-f (pronounced Meta f) is entered by depressing ESC (ASCII 033) followed by f. M-F is the notation for ESC followed by F.
All edit commands operate from any place on the line, not just at the beginning. The RETURN or the LINE FEED key is not entered after edit commands except when noted.
^F
M-[C
M-f
^B
M-[D
M-b
^A
M-[H
^E
M-[Y
^]char
M-^]char
^X^X
erase
lnext
^D
M-d
M-^H
M-h
M-^?
^T
^C
M-c
M-l
^K
^W
M-p
kill
^Y
^L
M-^L
^@
M-space
^J
^M
EOF
^P
M-[A
M-<
M->
^N
M-[B
^Rstring
^O
M-digits
M-letter
M-[letter
M-.
M-_
M-*
M-ESC
^ITAB
M-=
^U
\
M-^V
M-#
There are two typing modes. Initially, when you enter a command you are in the input mode. To edit, the user enters control mode by typing ESC (033) and moves the cursor to the point needing correction and then inserts or deletes characters or words as needed. Most control commands accept an optional repeat count prior to the command.
When in vi mode on most systems, canonical processing is initially enabled and the command is echoed again if the speed is 1200 baud or greater and it contains any control characters or less than one second has elapsed since the prompt was printed. The ESC character terminates canonical processing for the remainder of the command and the user can then modify the command line. This scheme has the advantages of canonical processing with the type-ahead echoing of raw mode.
If the option viraw is also set, the terminal is always have canonical processing disabled. This mode is implicit for systems that do not support two alternate end of line delimiters, and might be helpful for certain terminals.
By default the editor is in input mode.
The following input edit commands are supported:
ERASE
^W
EOF
lnext
\
^I TAB
The motion edit commands move the cursor.
The following motion edit commands are supported:
[count]l
[count][C
[count]w
[count]W
[count]e
[count]E
[count]h
[count][D
[count]b
[count]B
[count]|
[count]fc
[count]Fc
[count]tC
[count]Tc
[count];
[count],
0
^
[H
$
[Y
%
The search edit commands access your command history.
The following search edit commands are supported:
[count]k
[count]-
Equivalent to k.
[count][A
Equivalent to k.
[count]j
[count]+
Equivalent to j.
[count][B
Equivalent to j.
[count]G
/string
?string
Same as / except that search is in the forward direction.
n
N
The following commands modify the line:
a
A
[count]cmotion
c[count]motion
C
S
[count]s
D[count]dmotion
d[count]motion
i
I
[count]P
[count]p
R
[count]rc
[count]x
[count]X
[count].
[count]~
[count]_
*
\
The following miscellaneous edit commands are supported:
[count]ymotion
y[count]motion
yy
Y
u
U
[count]V
hist -e ${VISUAL:-${EDITOR:-vi}} count
in the input buffer. If count is omitted, the current line is used.
^L
^J
^M
#
Otherwise, send the line after inserting a # in front of each line in the command.
This is command is useful for causing the current line to be inserted in the history as a comment and un-commenting previously commented commands in the history file.
[count]=
Otherwise, replace the word at the current cursor location with the count item from the most recently generated command or file list. If the cursor is not on a word, it is inserted after the current cursor location.
@letter
^V
The following simple-commands are executed in the shell process. Input and output redirection is permitted. Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when there is no syntax error, is 0. Except for :, true, false, echo, newgrp, and login, all built-in commands accept -- to indicate the end of options. They also interpret the option --man as a request to display the manual page onto standard error and -? as a help request which prints a usage message on standard error.
Commands that are preceded by one or two ++ symbols are special built-in commands and are treated specially in the following ways:
+ : [arg ...]
+ . name [arg ...]
++ alias [-ptx] [name[ =value]] ...
bg [ job...]
+ break [n]
builtin [-ds ] [-f file] [name ...]
cd [-LP] [arg]
cd [-LP] old new
In the first form it changes the current directory to arg. If arg is a -, the directory is changed to the previous directory. The shell variable HOME is the default arg. The variable PWD is set to the current directory. The shell variable CDPATH defines the search path for the directory containing arg. Alternative directory names are separated by a colon (:). The default path is NULL (specifying the current directory). The current directory is specified by a null path name, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If arg begins with a /, the search path is not used. Otherwise, each directory in the path is searched for arg.
The second form of cd substitutes the string new for the string old in the current directory name, PWD, and tries to change to this new directory. By default, symbolic link names are treated literally when finding the directory name. This is equivalent to the -L option. The -P option causes symbolic links to be resolved when determining the directory. The last instance of -L or -P on the command line determines which method is used. The cd command cannot be executed by rksh93.
command [-pvVx] name [arg ...]
The -p option causes a default path to be searched rather than the one defined by the value of PATH. Functions are not searched when finding name. In addition, if name refers to a special built-in, none of the special properties associated with the leading daggers are honored. For example, the predefined alias redirect='command exec' prevents a script from terminating when an invalid redirection is specified.
With the -x option, if command execution would result in a failure because there are too many arguments, errno E2BIG, the shell invokes command name multiple times with a subset of the arguments on each invocation. Arguments that occur prior to the first word that expands to multiple arguments and after the last word that expands to multiple arguments are passed on each invocation. The exit status is the maximum invocation exit status.
With the -v option, command is equivalent to the built-in whence command described in this section. The -V option causes command to act like whence -v.
+continue [n]
disown [job...]
echo [arg ...]
+eval [arg ...]
+exec [-c] [-a name ...] [arg ...]
+exit [n]
++export [-p] [name[=value]] ...
false
fg [job ...]
getconf [name [pathname]]
The pathname argument is required for parameters whose value depends on the location in the file system. If no arguments are specified, getconf prints the names and values of the current configuration parameters. The pathname / is used for each of the parameters that requires pathname.
getopts [ -a name] optstring vname [arg ...]
hist [ -e ename][-nlr] [ first[last ] ]
hist -s [ old=new ] [ command]
jobs -lnp [job ...]
kill [-s signame] job ...
kill [-n signum] job ...
kill -l [sig ...]
let [arg ...]
+newgrp [arg ...]
print [-Renprs] [ -u unit] [ -f format ] [ arg ...]
\a
\b
\c
\f
\n
\r
\t
\v
\E
\\
\0x
The -R option prints all subsequent arguments and options other than -n. The -e causes the escape conventions to be applied This is the default behavior. It reverses the effect of an earlier -r. The -p option causes the arguments to be written onto the pipe of the process spawned with |& instead of standard output. The -s option causes the arguments to be written onto the history file instead of standard output. The -u option can be used to specify a one digit file descriptor unit number unit on which the output is placed. The default is 1. If the option -n is used, no NEWLINE is added to the output.
printf format[arg ...]
pwd [-LP]
read [-Aprs] [-d delim] [ -n n] [[ -N n] [[-t timeout] [-u unit] [vname?prompt] [ vname ... ]
++readonly [-p] [ vname[=value]] ...
+return [n]
+set [ ±BCGabefhkmnoprstuvx] [±o [ option ] ] ... [ ±A vname] [arg...]
-a
-A
-b
-B
-C
-e
-f
-G
-h
-k
-m
-n
-o
The following argument can be one of the following option names:
allexport
bgnice
braceexpand
emacs
errexit
globstar
gmacs
ignoreeof
keyword
markdirs
monitor
multiline
noclobber
noexec
noglob
nolog
notify
nounset
pipefail
privileged
showme
trackall
verbose
vi
viraw
xtrace
If no option name is supplied, the current options settings are printed.
-p
-r
-s
-t
-u
-v
-x
--
As an obsolete feature, if the first arg is - then the -x and -v options are turned off and the next arg is treated as the first argument. Using + rather than - causes these options to be turned off. These options can also be used upon invocation of the shell. The current set of options can be found in $-. Unless -A is specified, the remaining arguments are positional parameters and are assigned, in order, to $1 $2 .... If no arguments are specified, then the names and values of all variables are printed on the standard output.
+shift [n]
sleep seconds
+trap -p [action] [sig] ...
true
++typeset [±AHflabnprtux ] [ ±EFLRZi[n] ] [ vname[=value ] ]
Using + rather than - causes these options to be turned off. If no vname arguments are specified, a list of vnames (and optionally the values) of the variables is printed. Using + rather than - keeps the values from being printed.) The -p option causes typeset followed by the option letters to be printed before each name rather than the names of the options. If any option other than -p is specified, only those variables which have all of the specified options are printed. Otherwise, the vnames and attributes of all variables that have attributes are printed.
The following list of attributes can be specified:
-a
-A
-b
-E
-f
The -i attribute cannot be specified with -f.
-F
-H
-i
The -i attribute cannot be specified along with -R, -L, -Z, or -f.
-l
-L
The -i attribute cannot be specified with -L.
-n
-R
The -i attribute cannot be specified with -R.
-r
-t
-u
-x
-Z
The -i attribute cannot be specified with -Z.
ulimit [-HSacdfmnpstv] [ limit]
If no option is specified, -f is assumed.
The following are the available resource limits:
-a
-c
-d
-f
-H
A hard limit cannot be increased once it is set.
If neither the -H nor -S option is specified, the limit applies to both. The current resource limit is printed when limit is omitted. In this case, the soft limit is printed unless -H is specified.
-m
-n
-p
-s
-S
A soft limit can be increased up to the value of the hard limit.
If neither the -H nor -S option is specified, the limit applies to both. The current resource limit is printed when limit is omitted. In this case, the soft limit is printed unless -H is specified.
-t
-v
umask [-S][mask]
If a symbolic value is specified, the new umask value is the complement of the result of applying mask to the complement of the previous umask value. If mask is omitted, the current value of the mask is printed. The -S option causes the mode to be printed as a symbolic value. Otherwise, the mask is printed in octal.
See umask(2)
+unalias [-a] name
+unset [-fnv] vname
wait [job]
whence [-afpv] name ...
If the shell is invoked by exec(2), and the first character of argument zero ($0) is -, then the shell is assumed to be a login shell and commands are read from /etc/profile and then from either .profile in the current directory or $HOME/.profile, if either file exists. Next, for interactive shells, commands are read first from /etc/ksh.kshrc, and then from the file named by performing parameter expansion, command substitution, and arithmetic substitution on the value of the environment variable ENV if the file exists. If the -s option is not present and arg and a file by the name of arg exists, then it reads and executes this script. Otherwise, if the first arg does not contain a /, a path search is performed on the first arg to determine the name of the script to execute. The script arg must have execute permission and any setuid and setgid settings are ignored. If the script is not found on the path, arg is processed as if it named a built-in command or function.
Commands are then read as described, and the following options are interpreted by the shell when it is invoked:
-c
-D
-i
-R filename
-r
-s
The remaining options and arguments are described under the set command. An optional - as the first argument is ignored.
rksh93 is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell.
The actions of rksh93 are identical to those of ksh93, except that the following are disallowed:
These restrictions are enforced after .profile and the ENV files are interpreted.
When a command to be executed is found to be a shell procedure, rksh93 invokes ksh93 to execute it. Thus, it is possible to provide to the end-user shell procedures that have access to the full power of the standard shell, while imposing a limited menu of commands. This scheme assumes that the end-user does not have write and execute permissions in the same directory. The net effect of these rules is that the writer of the .profile has complete control over user actions, by performing guaranteed setup actions and leaving the user in an appropriate directory (probably not the login directory). The system administrator often sets up a directory of commands, for example, /usr/rbin, that can be safely invoked by rksh.
See largefile(5) for the description of the behavior of ksh93 and rksh93 when encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
The following exit values are returned:
non-zero
If the shell is being used non-interactively, then execution of the shell file is abandoned unless the error occurs inside a sub-shell in which case the sub-shell is abandoned.
exit status of last command executed
Run time errors detected by the shell are reported by printing the command or function name and the error condition. If the line number that the error occurred on is greater than one, then the line number is also printed in square brackets ([]) after the command or function name.
See the ksh93 exit command for additional details.
/etc/profile
/etc/ksh.kshrc
$HOME/.profile
$HOME/.kshrc
/etc/suid-profile
/dev/null
David Korn, dgk@research.att.com
See attributes(5) for descriptions of the following attributes:
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The scripting interface is Uncommitted. The environment variables, .paths feature, and editing modes are Volatile.
cat(1), cd(1), chmod(1), cut(1), date(1), egrep(1), echo(1), egrep(1), env(1), fgrep(1), grep(1), login(1), newgrp(1), paste(1), printf(1), stty(1), test(1), umask(1), vi(1), dup(2), exec(2), fork(2), ioctl(2), lseek(2), pathconf(2), pipe(2), sysconf(3C), ulimit(2), umask(2), rand(3C)tcgetattr(3C), wait(3C), a.out(4), profile(4), attributes(5), environ(5), largefile(5), standards(5)
Bolsky, Morris I. and Korn, David G., The New KornShell Command and Programming Language, Prentice Hall, 1995.
POSIX-Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.
If a command is executed, and then a command with the same name is installed in a directory in the search path before the directory where the original command was found, the shell continues to exec the original command. Use the -t option of the alias command to correct this situation.
Some very old shell scripts contain a caret (^) as a synonym for the pipe character (|).
Using the hist built-in command within a compound command causes the whole command to disappear from the history file.
The built-in command . file reads the whole file before any commands are executed. alias and unalias commands in the file do not apply to any commands defined in the file.
Traps are not processed while a job is waiting for a foreground process. Thus, a trap on CHLD is not executed until the foreground job terminates.
It is a good idea to leave a space after the comma operator in arithmetic expressions to prevent the comma from being interpreted as the decimal point character in certain locales.
There might be some restrictions on creating a .paths file which is portable across other operating systems.
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