1KSH(1) General Commands Manual KSH(1)
2
6 ksh, rksh, pfksh - KornShell, a standard/restricted command and pro‐
7 gramming language
8
10 ksh [ ±abcefhiknoprstuvxBCDP ] [ -R file ] [ ±o option ] ... [ - ] [
11 arg ... ]
12
14 Ksh is a command and programming language that executes commands read
15 from a terminal or a file. Rksh is a restricted version of the command
16 interpreter ksh; it is used to set up login names and execution envi‐
17 ronments whose capabilities are more controlled than those of the stan‐
18 dard shell. Rpfksh is a profile shell version of the command inter‐
19 preter ksh; it is used to to execute commands with the attributes spec‐
20 ified by the user's profiles (see pfexec(1)). See Invocation below for
21 the meaning of arguments to the shell.
22 Definitions.
24 A metacharacter is one of the following characters:
25 ; & ( ) ⎪ < > new-line space tab
27 A blank is a tab or a space. An identifier is a sequence of letters,
29 digits, or underscores starting with a letter or underscore. Identi‐
30 fiers are used as components of variable names. A vname is a sequence
31 of one or more identifiers separated by a . and optionally preceded by
32 a .. Vnames are used as function and variable names. A word is a
33 sequence of characters from the character set defined by the current
34 locale, excluding non-quoted metacharacters.
35 A command is a sequence of characters in the syntax of the shell lan‐
37 guage. The shell reads each command and carries out the desired action
38 either directly or by invoking separate utilities. A built-in command
39 is a command that is carried out by the shell itself without creating a
40 separate process. Some commands are built-in purely for convenience
41 and are not documented here. Built-ins that cause side effects in the
42 shell environment and built-ins that are found before performing a path
43 search (see Execution below) are documented here. For historical rea‐
44 sons, some of these built-ins behave differently than other built-ins
45 and are called special built-ins.
46 Commands.
48 A simple-command is a list of variable assignments (see Variable
49 Assignments below) or a sequence of blank separated words which may be
50 preceded by a list of variable assignments (see Environment below).
51 The first word specifies the name of the command to be executed.
52 Except as specified below, the remaining words are passed as arguments
53 to the invoked command. The command name is passed as argument 0 (see
54 exec(2)). The value of a simple-command is its exit status; 0-255 if
55 it terminates normally; 256+signum if it terminates abnormally (the
56 name of the signal corresponding to the exit status can be obtained via
57 the -l option of the kill built-in utility).
58 A pipeline is a sequence of one or more commands separated by ⎪. The
60 standard output of each command but the last is connected by a pipe(2)
61 to the standard input of the next command. Each command, except possi‐
62 bly the last, is run as a separate process; the shell waits for the
63 last command to terminate. The exit status of a pipeline is the exit
64 status of the last command unless the pipefail option is enabled. Each
65 pipeline can be preceded by the reserved word ! which causes the exit
66 status of the pipeline to become 0 if the exit status of the last com‐
67 mand is non-zero, and 1 if the exit status of the last command is 0.
68 A list is a sequence of one or more pipelines separated by ;, &, ⎪&,
70 &&, or ⎪⎪, and optionally terminated by ;, &, or ⎪&. Of these five
71 symbols, ;, &, and ⎪& have equal precedence, which is lower than that
72 of && and ⎪⎪. The symbols && and ⎪⎪ also have equal precedence. A
73 semicolon (;) causes sequential execution of the preceding pipeline; an
74 ampersand (&) causes asynchronous execution of the preceding pipeline
75 (i.e., the shell does not wait for that pipeline to finish). The sym‐
76 bol ⎪& causes asynchronous execution of the preceding pipeline with a
77 two-way pipe established to the parent shell; the standard input and
78 output of the spawned pipeline can be written to and read from by the
79 parent shell by applying the redirection operators <& and >& with arg p
80 to commands and by using -p option of the built-in commands read and
81 print described later. The symbol && (⎪⎪) causes the list following it
82 to be executed only if the preceding pipeline returns a zero (non-zero)
83 value. One or more new-lines may appear in a list instead of a semi‐
84 colon, to delimit a command. The first item of the first pipeline of
85 a list that is a simple command not beginning with a redirection, and
86 not occurring within a while, until, or if list, can be preceded by a
87 semicolon. This semicolon is ignored unless the showme option is
88 enabled as described with the set built-in below.
89 A command is either a simple-command or one of the following. Unless
91 otherwise stated, the value returned by a command is that of the last
92 simple-command executed in the command.
93 for vname [ in word ... ] ;do list ;done
95 Each time a for command is executed, vname is set to the next
96 word taken from the in word list. If in word ... is omitted,
97 then the for command executes the do list once for each posi‐
98 tional parameter that is set starting from 1 (see Parameter
99 Expansion below). Execution ends when there are no more words
100 in the list.
101 for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
103 The arithmetic expression expr1 is evaluated first (see Arith‐
104 metic evaluation below). The arithmetic expression expr2 is
105 repeatedly evaluated until it evaluates to zero and when non-
106 zero, list is executed and the arithmetic expression expr3 eval‐
107 uated. If any expression is omitted, then it behaves as if it
108 evaluated to 1.
109 select vname [ in word ... ] ;do list ;done
111 A select command prints on standard error (file descriptor 2)
112 the set of words, each preceded by a number. If in word ... is
113 omitted, then the positional parameters starting from 1 are used
114 instead (see Parameter Expansion below). The PS3 prompt is
115 printed and a line is read from the standard input. If this
116 line consists of the number of one of the listed words, then the
117 value of the variable vname is set to the word corresponding to
118 this number. If this line is empty, the selection list is
119 printed again. Otherwise the value of the variable vname is set
120 to null. The contents of the line read from standard input is
121 saved in the variable REPLY. The list is executed for each
122 selection until a break or end-of-file is encountered. If the
123 REPLY variable is set to null by the execution of list, then the
124 selection list is printed before displaying the PS3 prompt for
125 the next selection.
126 case word in [ [(]pattern [ ⎪ pattern ] ... ) list ;; ] ... esac
128 A case command executes the list associated with the first pat‐
129 tern that matches word. The form of the patterns is the same as
130 that used for file-name generation (see File Name Generation
131 below). The ;; operator causes execution of case to terminate.
132 If ;& is used in place of ;; the next subsequent list, if any,
133 is executed.
134 if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
136 The list following if is executed and, if it returns a zero exit
137 status, the list following the first then is executed. Other‐
138 wise, the list following elif is executed and, if its value is
139 zero, the list following the next then is executed. Failing
140 each successive elif list, the else list is executed. If the if
141 list has non-zero exit status and there is no else list, then
142 the if command returns a zero exit status.
143 while list ;do list ;done
145 until list ;do list ;done
146 A while command repeatedly executes the while list and, if the
147 exit status of the last command in the list is zero, executes
148 the do list; otherwise the loop terminates. If no commands in
149 the do list are executed, then the while command returns a zero
150 exit status; until may be used in place of while to negate the
151 loop termination test.
152 ((expression))
154 The expression is evaluated using the rules for arithmetic eval‐
155 uation described below. If the value of the arithmetic expres‐
156 sion is non-zero, the exit status is 0, otherwise the exit sta‐
157 tus is 1.
158 (list)
160 Execute list in a separate environment. Note, that if two adja‐
161 cent open parentheses are needed for nesting, a space must be
162 inserted to avoid evaluation as an arithmetic command as
163 described above.
164 { list;}
166 list is simply executed. Note that unlike the metacharacters (
167 and ), { and } are reserved words and must occur at the begin‐
168 ning of a line or after a ; in order to be recognized.
169 [[ expression ]]
171 Evaluates expression and returns a zero exit status when expres‐
172 sion is true. See Conditional Expressions below, for a descrip‐
173 tion of expression.
174 function varname { list ;}
176 varname () { list ;}
177 Define a function which is referenced by varname. A function
178 whose varname contains a . is called a discipline function and
179 the portion of the varname preceding the last . must refer to
180 an existing variable. The body of the function is the list of
181 commands between { and }. A function defined with the function
182 varname syntax can also be used as an argument to the . special
183 built-in command to get the equivalent behavior as if the var‐
184 name() syntax were used to define it. (See Functions below.)
185 namespace identifier { list ;}
187 Defines or uses the name space identifier and runs the commands
188 in list in this name space. (See Name Spaces below.)
189 & [ name [ arg... ] ]
191 Causes subsequent list commands terminated by & to be placed in
192 the background job pool name. If name is omitted a default
193 unnamed pool is used. Commands in a named background pool may
194 be executed remotely.
195 time [ pipeline ]
197 If pipeline is omitted the user and system time for the current
198 shell and completed child processes is printed on standard
199 error. Otherwise, pipeline is executed and the elapsed time as
200 well as the user and system time are printed on standard error.
201 The TIMEFORMAT variable may be set to a format string that spec‐
202 ifies how the timing information should be displayed. See Shell
203 Variables below for a description of the TIMEFORMAT variable.
204 The following reserved words are recognized as reserved only when they
206 are the first word of a command and are not quoted:
207 if then else elif fi case esac for while until do done { } function
209 select time [[ ]] !
210 Variable Assignments.
212 One or more variable assignments can start a simple command or can be
213 arguments to the typeset, enum, export, or readonly special built-in
214 commands as well as to other declaration commands created as types.
215 The syntax for an assignment is of the form:
216 varname=word
218 varname[word]=word
219 No space is permitted between varname and the = or between = and
220 word.
221 varname=(assign_list)
223 No space is permitted between varname and the =. The variable
224 varname is unset before the assignment. An assign_list can be
225 one of the following:
226 word ...
227 Indexed array assignment.
228 [word]=word ...
229 Associative array assignment. If preceded by
230 typeset -a this will create an indexed array
231 instead.
232 assignment ...
233 Compound variable assignment. This creates a
234 compound variable varname with sub-variables of
235 the form varname.name, where name is the name
236 portion of assignment. The value of varname will
237 contain all the assignment elements. Additional
238 assignments made to sub-variables of varname will
239 also be displayed as part of the value of var‐
240 name. If no assignments are specified, varname
241 will be a compound variable allowing subsequence
242 child elements to be defined.
243 typeset [options] assignment ...
244 Nested variable assignment. Multiple assignments
245 can be specified by separating each of them with
246 a ;. The previous value is unset before the
247 assignment. Other declaration commands such as
248 readonly, enum, and other declaration commands
249 can be used in place of typeset.
250 . filename
251 Include the assignment commands contained in
252 filename.
253 In addition, a += can be used in place of the = to signify adding to or
255 appending to the previous value. When += is applied to an arithmetic
256 type, word is evaluated as an arithmetic expression and added to the
257 current value. When applied to a string variable, the value defined by
258 word is appended to the value. For compound assignments, the previous
259 value is not unset and the new values are appended to the current ones
260 provided that the types are compatible.
261 The right hand side of a variable assignment undergoes all the expan‐
263 sion listed below except word splitting, brace expansion, and file name
264 generation. When the left hand side is an assignment is a compound
265 variable and the right hand is the name of a compound variable, the
266 compound variable on the right will be copied or appended to the com‐
267 pound variable on the left.
268 Comments.
270 A word beginning with # causes that word and all the following charac‐
271 ters up to a new-line to be ignored.
272 Aliasing.
273 The first word of each command is replaced by the text of an alias if
274 an alias for this word has been defined. An alias name consists of any
275 number of characters excluding metacharacters, quoting characters, file
276 expansion characters, parameter expansion and command substitution
277 characters, the characters / and =. The replacement string can contain
278 any valid shell script including the metacharacters listed above. The
279 first word of each command in the replaced text, other than any that
280 are in the process of being replaced, will be tested for aliases. If
281 the last character of the alias value is a blank then the word follow‐
282 ing the alias will also be checked for alias substitution. Aliases can
283 be used to redefine built-in commands but cannot be used to redefine
284 the reserved words listed above. Aliases can be created and listed
285 with the alias command and can be removed with the unalias command.
286 Aliasing is performed when scripts are read, not while they are exe‐
287 cuted. Therefore, for an alias to take effect, the alias definition
288 command has to be executed before the command which references the
289 alias is read.
290 The following aliases are compiled into the shell but can be unset or
291 redefined:
292 autoload=′typeset -fu′
293 command=′command ′
294 compound=′typeset -C′
295 fc=hist
296 float=′typeset -lE′
297 functions=′typeset -f′
298 hash=′alias -t --′
299 history=′hist -l′
300 integer=′typeset -li′
301 nameref=′typeset -n′
302 nohup=′nohup ′
303 r=′hist -s′
304 redirect=′command exec′
305 source=′command .′
306 stop=′kill -s STOP′
307 suspend=′kill -s STOP $$′
308 times=′{ { time;} 2>&1;}′
309 type=′whence -v′
310 Tilde Substitution.
312 After alias substitution is performed, each word is checked to see if
313 it begins with an unquoted ∼. For tilde substitution, word also refers
314 to the word portion of parameter expansion (see Parameter Expansion
315 below). If it does, then the word up to a / is checked to see if it
316 matches a user name in the password database (See getpwname(3).) If a
317 match is found, the ∼ and the matched login name are replaced by the
318 login directory of the matched user. If no match is found, the origi‐
319 nal text is left unchanged. A ∼ by itself, or in front of a /, is
320 replaced by $HOME. A ∼ followed by a + or - is replaced by the value
321 of $PWD and $OLDPWD respectively.
322 In addition, when expanding a variable assignment, tilde substitution
324 is attempted when the value of the assignment begins with a ∼, and when
325 a ∼ appears after a :. The : also terminates a ∼ login name.
326 Command Substitution.
328 The standard output from a command list enclosed in parentheses pre‐
329 ceded by a dollar sign ( $(list) ), or in a brace group preceded by a
330 dollar sign ( ${ list;} ), or in a pair of grave accents (``) may be
331 used as part or all of a word; trailing new-lines are removed. In the
332 second case, the { and } are treated as a reserved words so that { must
333 be followed by a blank and } must appear at the beginning of the line
334 or follow a ;. In the third (obsolete) form, the string between the
335 quotes is processed for special quoting characters before the command
336 is executed (see Quoting below). The command substitution $(cat file)
337 can be replaced by the equivalent but faster $(<file). The command
338 substitution $(n<#) will expand to the current byte offset for file
339 descriptor n. Except for the second form, the command list is run in a
340 subshell so that no side effects are possible. For the second form,
341 the final } will be recognized as a reserved word after any token.
342 Arithmetic Substitution.
344 An arithmetic expression enclosed in double parentheses preceded by a
345 dollar sign ( $(()) ) is replaced by the value of the arithmetic
346 expression within the double parentheses.
347 Process Substitution.
349 Each command argument of the form <(list) or >(list) will run process
350 list asynchronously connected to some file in /dev/fd if this directory
351 exists, or else a fifo a temporary directory. The name of this file
352 will become the argument to the command. If the form with > is
353 selected then writing on this file will provide input for list. If <
354 is used, then the file passed as an argument will contain the output of
355 the list process. For example,
356 paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1)
358 >(process2)
359 cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
361 the results together, and sends it to the processes process1 and
362 process2, as well as putting it onto the standard output. Note that
363 the file, which is passed as an argument to the command, is a UNIX
364 pipe(2) so programs that expect to lseek(2) on the file will not work.
365 Process substitution of the form <(list) can also be used with the <
367 redirection operator which causes the output of list to be standard
368 input or the input for whatever file descriptor is specified.
369 Parameter Expansion.
371 A parameter is a variable, one or more digits, or any of the characters
372 ∗, @, #, ?, -, $, and !. A variable is denoted by a vname. To create
373 a variable whose vname contains a ., a variable whose vname consists of
374 everything before the last . must already exist. A variable has a
375 value and zero or more attributes. Variables can be assigned values
376 and attributes by using the typeset special built-in command. The
377 attributes supported by the shell are described later with the typeset
378 special built-in command. Exported variables pass values and
379 attributes to the environment.
380 The shell supports both indexed and associative arrays. An element of
382 an array variable is referenced by a subscript. A subscript for an
383 indexed array is denoted by an arithmetic expression (see Arithmetic
384 evaluation below) between a [ and a ]. To assign values to an indexed
385 array, use vname=(value ...) or set -A vname value ... . The value of
386 all non-negative subscripts must be in the range of 0 through
387 4,194,303. A negative subscript is treated as an offset from the maxi‐
388 mum current index +1 so that -1 refers to the last element. Indexed
389 arrays can be declared with the -a option to typeset. Indexed arrays
390 need not be declared. Any reference to a variable with a valid sub‐
391 script is legal and an array will be created if necessary.
392 An associative array is created with the -A option to typeset. A sub‐
394 script for an associative array is denoted by a string enclosed between
395 [ and ].
396 Referencing any array without a subscript is equivalent to referencing
398 the array with subscript 0.
399 The value of a variable may be assigned by writing:
401 vname=value [ vname=value ] ...
403 or
405 vname[subscript]=value [ vname[subscript]=value ] ...
406 Note that no space is allowed before or after the =.
407 Attributes assigned by the typeset special built-in command apply to
408 all elements of the array. An array element can be a simple variable,
409 a compound variable or an array variable. An element of an indexed
410 array can be either an indexed array or an associative array. An ele‐
411 ment of an associative array can also be either. To refer to an array
412 element that is part of an array element, concatenate the subscript in
413 brackets. For example, to refer to the foobar element of an associa‐
414 tive array that is defined as the third element of the indexed array,
415 use ${vname[3][foobar]}
416 A nameref is a variable that is a reference to another variable. A
417 nameref is created with the -n attribute of typeset. The value of the
418 variable at the time of the typeset command becomes the variable that
419 will be referenced whenever the nameref variable is used. The name of
420 a nameref cannot contain a .. When a variable or function name con‐
421 tains a ., and the portion of the name up to the first . matches the
422 name of a nameref, the variable referred to is obtained by replacing
423 the nameref portion with the name of the variable referenced by the
424 nameref. If a nameref is used as the index of a for loop, a name ref‐
425 erence is established for each item in the list. A nameref provides a
426 convenient way to refer to the variable inside a function whose name is
427 passed as an argument to a function. For example, if the name of a
428 variable is passed as the first argument to a function, the command
429 typeset -n var=$1
430 inside the function causes references and assignments to var to be ref‐
431 erences and assignments to the variable whose name has been passed to
432 the function.
433 If any of the floating point attributes, -E, -F, or -X, or the integer
434 attribute, -i, is set for vname, then the value is subject to arith‐
435 metic evaluation as described below.
436 Positional parameters, parameters denoted by a number, may be assigned
437 values with the set special built-in command. Parameter $0 is set from
438 argument zero when the shell is invoked.
439 The character $ is used to introduce substitutable parameters.
440 ${parameter}
441 The shell reads all the characters from ${ to the matching } as
442 part of the same word even if it contains braces or metacharac‐
443 ters. The value, if any, of the parameter is substituted. The
444 braces are required when parameter is followed by a letter,
445 digit, or underscore that is not to be interpreted as part of
446 its name, when the variable name contains a .. The braces are
447 also required when a variable is subscripted unless it is part
448 of an Arithmetic Expression or a Conditional Expression. If
449 parameter is one or more digits then it is a positional parame‐
450 ter. A positional parameter of more than one digit must be
451 enclosed in braces. If parameter is ∗ or @, then all the posi‐
452 tional parameters, starting with $1, are substituted (separated
453 by a field separator character). If an array vname with last
454 subscript ∗ @, or for index arrays of the form sub1 .. sub2.
455 is used, then the value for each of the elements between sub1
456 and sub2 inclusive (or all elements for ∗ and @) is substituted,
457 separated by the first character of the value of IFS.
458 ${#parameter}
459 If parameter is ∗ or @, the number of positional parameters is
460 substituted. Otherwise, the length of the value of the parame‐
461 ter is substituted.
462 ${#vname[*]}
463 ${#vname[@]}
464 The number of elements in the array vname is substituted.
465 ${@vname}
467 Expands to the type name (See Type Variables below) or
468 attributes of the variable referred to by vname.
469 ${!vname}
470 Expands to the name of the variable referred to by vname. This
471 will be vname except when vname is a name reference.
472 ${!vname[subscript]}
473 Expands to name of the subscript unless subscript is *, @. or
474 of the form sub1 .. sub2. When subscript is *, the list of
475 array subscripts for vname is generated. For a variable that is
476 not an array, the value is 0 if the variable is set. Otherwise
477 it is null. When subscript is @, same as above, except that
478 when used in double quotes, each array subscript yields a sepa‐
479 rate argument. When subscript is of the form sub1 .. sub2 it
480 expands to the list of subscripts between sub1 and sub2 inclu‐
481 sive using the same quoting rules as @.
482 ${!prefix*}
483 Expands to the names of the variables whose names begin with
484 prefix.
485 ${parameter:-word}
486 If parameter is set and is non-null then substitute its value;
487 otherwise substitute word.
488 ${parameter:=word}
489 If parameter is not set or is null then set it to word; the
490 value of the parameter is then substituted. Positional parame‐
491 ters may not be assigned to in this way.
492 ${parameter:?word}
493 If parameter is set and is non-null then substitute its value;
494 otherwise, print word and exit from the shell (if not interac‐
495 tive). If word is omitted then a standard message is printed.
496 ${parameter:+word}
497 If parameter is set and is non-null then substitute word; other‐
498 wise substitute nothing.
499 In the above, word is not evaluated unless it is to be used as the sub‐
500 stituted string, so that, in the following example, pwd is executed
501 only if d is not set or is null:
502 print ${d:-$(pwd)}
503 If the colon ( : ) is omitted from the above expressions, then the
504 shell only checks whether parameter is set or not.
505 ${parameter:offset:length}
506 ${parameter:offset}
507 Expands to the portion of the value of parameter starting at the
508 character (counting from 0) determined by expanding offset as an
509 arithmetic expression and consisting of the number of characters
510 determined by the arithmetic expression defined by length. In
511 the second form, the remainder of the value is used. If A nega‐
512 tive offset counts backwards from the end of parameter. Note
513 that one or more blanks is required in front of a minus sign to
514 prevent the shell from interpreting the operator as :-. If
515 parameter is ∗ or @, or is an array name indexed by ∗ or @, then
516 offset and length refer to the array index and number of ele‐
517 ments respectively. A negative offset is taken relative to one
518 greater than the highest subscript for indexed arrays. The
519 order for associate arrays is unspecified.
520 ${parameter#pattern}
521 ${parameter##pattern}
522 If the shell pattern matches the beginning of the value of
523 parameter, then the value of this expansion is the value of the
524 parameter with the matched portion deleted; otherwise the value
525 of this parameter is substituted. In the first form the small‐
526 est matching pattern is deleted and in the second form the
527 largest matching pattern is deleted. When parameter is @, *, or
528 an array variable with subscript @ or *, the substring operation
529 is applied to each element in turn.
530 ${parameter%pattern}
532 ${parameter%%pattern}
533 If the shell pattern matches the end of the value of parameter,
534 then the value of this expansion is the value of the parameter
535 with the matched part deleted; otherwise substitute the value of
536 parameter. In the first form the smallest matching pattern is
537 deleted and in the second form the largest matching pattern is
538 deleted. When parameter is @, *, or an array variable with sub‐
539 script @ or *, the substring operation is applied to each ele‐
540 ment in turn.
541 ${parameter/pattern/string}
543 ${parameter//pattern/string}
544 ${parameter/#pattern/string}
545 ${parameter/%pattern/string}
546 Expands parameter and replaces the longest match of pattern with
547 the given string. Each occurrence of \n in string is replaced
548 by the portion of parameter that matches the n-th sub-pattern.
549 In the first form, only the first occurrence of pattern is
550 replaced. In the second form, each match for pattern is
551 replaced by the given string. The third form restricts the pat‐
552 tern match to the beginning of the string while the fourth form
553 restricts the pattern match to the end of the string. When
554 string is null, the pattern will be deleted and the / in front
555 of string may be omitted. When parameter is @, *, or an array
556 variable with subscript @ or *, the substitution operation is
557 applied to each element in turn. In this case, the string por‐
558 tion of word will be re-evaluated for each element.
559 The following parameters are automatically set by the shell:
561 # The number of positional parameters in decimal.
562 - Options supplied to the shell on invocation or by the set
563 command.
564 ? The decimal value returned by the last executed command.
565 $ The process number of this shell.
566 _ Initially, the value of _ is an absolute pathname of the
567 shell or script being executed as passed in the environ‐
568 ment. Subsequently it is assigned the last argument of
569 the previous command. This parameter is not set for com‐
570 mands which are asynchronous. This parameter is also
571 used to hold the name of the matching MAIL file when
572 checking for mail. While defining a compound variable or
573 a type, _ is initialized as a reference to the compound
574 variable or type. When a discipline function is invoked,
575 _ is initialized as a reference to the variable associ‐
576 ated with the call to this function. Finally when _ is
577 used as the name of the first variable of a type defini‐
578 tion, the new type is derived from the type of the first
579 variable (See Type Variables below.).
580 ! The process id or the pool name and job number of the
581 last background command invoked or the most recent job
582 put in the background with the bg built-in command.
583 Background jobs started in a named pool will be in the
584 form pool.number where pool is the pool name and number
585 is the job number within that pool.
586 .sh.command
587 When processing a DEBUG trap, this variable contains the
588 current command line that is about to run.
589 .sh.edchar
590 This variable contains the value of the keyboard charac‐
591 ter (or sequence of characters if the first character is
592 an ESC, ascii 033) that has been entered when processing
593 a KEYBD trap (see Key Bindings below). If the value is
594 changed as part of the trap action, then the new value
595 replaces the key (or key sequence) that caused the trap.
596 .sh.edcol
597 The character position of the cursor at the time of the
598 most recent KEYBD trap.
599 .sh.edmode
600 The value is set to ESC when processing a KEYBD trap
601 while in vi insert mode. (See Vi Editing Mode below.)
602 Otherwise, .sh.edmode is null when processing a KEYBD
603 trap.
604 .sh.edtext
605 The characters in the input buffer at the time of the
606 most recent KEYBD trap. The value is null when not pro‐
607 cessing a KEYBD trap.
608 .sh.file
609 The pathname of the file than contains the current com‐
610 mand.
611 .sh.fun
612 The name of the current function that is being executed.
613 .sh.level
614 Set to the current function depth. This can be changed
615 inside a DEBUG trap and will set the context to the spec‐
616 ified level.
617 .sh.lineno
618 Set during a DEBUG trap to the line number for the caller
619 of each function.
620 .sh.match
621 An indexed array which stores the most recent match and
622 sub-pattern matches after conditional pattern matches
623 that match and after variables expansions using the oper‐
624 ators #, %, or /. The 0-th element stores the complete
625 match and the i-th. element stores the i-th submatch.
626 The .sh.match variable becomes unset when the variable
627 that has expanded is assigned a new value.
628 .sh.math
629 Used for defining arithmetic functions (see Arithmetic
630 evaluation below). and stores the list of user defined
631 arithmetic functions.
632 .sh.name
633 Set to the name of the variable at the time that a disci‐
634 pline function is invoked.
635 .sh.subscript
636 Set to the name subscript of the variable at the time
637 that a discipline function is invoked.
638 .sh.subshell
639 The current depth for subshells and command substitution.
640 .sh.value
641 Set to the value of the variable at the time that the set
642 or append discipline function is invoked. When a user
643 defined arithmetic function is invoked, the value of
644 .sh.value is saved and .sh.value is set to long double
645 precision floating point. .sh.value is restored when the
646 function returns.
647 .sh.version
648 Set to a value that identifies the version of this shell.
649 KSH_VERSION
650 A name reference to .sh.version.
651 LINENO The current line number within the script or function
652 being executed.
653 OLDPWD The previous working directory set by the cd command.
654 OPTARG The value of the last option argument processed by the
655 getopts built-in command.
656 OPTIND The index of the last option argument processed by the
657 getopts built-in command.
658 PPID The process number of the parent of the shell.
659 PWD The present working directory set by the cd command.
660 RANDOM Each time this variable is referenced, a random integer,
661 uniformly distributed between 0 and 32767, is generated.
662 The sequence of random numbers can be initialized by
663 assigning a numeric value to RANDOM.
664 REPLY This variable is set by the select statement and by the
665 read built-in command when no arguments are supplied.
666 SECONDS
667 Each time this variable is referenced, the number of sec‐
668 onds since shell invocation is returned. If this vari‐
669 able is assigned a value, then the value returned upon
670 reference will be the value that was assigned plus the
671 number of seconds since the assignment.
672 SHLVL An integer variable the is incremented each time the
673 shell is invoked and is exported. If SHLVL is not in the
674 environment when the shell is invoked, it is set to 1.
675 The following variables are used by the shell:
677 CDPATH The search path for the cd command.
678 COLUMNS
679 If this variable is set, the value is used to define the
680 width of the edit window for the shell edit modes and for
681 printing select lists.
682 EDITOR If the VISUAL variable is not set, the value of this
683 variable will be checked for the patterns as described
684 with VISUAL below and the corresponding editing option
685 (see Special Command set below) will be turned on.
686 ENV If this variable is set, then parameter expansion, com‐
687 mand substitution, and arithmetic substitution are per‐
688 formed on the value to generate the pathname of the
689 script that will be executed when the shell is invoked
690 interactively (see Invocation below). This file is typi‐
691 cally used for alias and function definitions. The
692 default value is $HOME/.kshrc. On systems that support a
693 system wide /etc/ksh.kshrc initialization file, if the
694 filename generated by the expansion of ENV begins with
695 /./ or ././ the system wide initialization file will not
696 be executed.
697 FCEDIT Obsolete name for the default editor name for the hist
698 command. FCEDIT is not used when HISTEDIT is set.
699 FIGNORE
700 A pattern that defines the set of filenames that will be
701 ignored when performing filename matching.
702 FPATH The search path for function definitions. The directo‐
703 ries in this path are searched for a file with the same
704 name as the function or command when a function with the
705 -u attribute is referenced and when a command is not
706 found. If an executable file with the name of that com‐
707 mand is found, then it is read and executed in the cur‐
708 rent environment. Unlike PATH, the current directory
709 must be represented explicitly by . rather than by adja‐
710 cent : characters or a beginning or ending :.
711 HISTCMD
712 Number of the current command in the history file.
713 HISTEDIT
714 Name for the default editor name for the hist command.
715 HISTFILE
716 If this variable is set when the shell is invoked, then
717 the value is the pathname of the file that will be used
718 to store the command history (see Command Re-entry
719 below).
720 HISTSIZE
721 If this variable is set when the shell is invoked, then
722 the number of previously entered commands that are acces‐
723 sible by this shell will be greater than or equal to this
724 number. The default is 512.
725 HOME The default argument (home directory) for the cd command.
726 IFS Internal field separators, normally space, tab, and new-
727 line that are used to separate the results of command
728 substitution or parameter expansion and to separate
729 fields with the built-in command read. The first charac‐
730 ter of the IFS variable is used to separate arguments for
731 the "$∗" substitution (see Quoting below). Each single
732 occurrence of an IFS character in the string to be split,
733 that is not in the isspace character class, and any adja‐
734 cent characters in IFS that are in the isspace character
735 class, delimit a field. One or more characters in IFS
736 that belong to the isspace character class, delimit a
737 field. In addition, if the same isspace character
738 appears consecutively inside IFS, this character is
739 treated as if it were not in the isspace class, so that
740 if IFS consists of two tab characters, then two adjacent
741 tab characters delimit a null field.
742 JOBMAX This variable defines the maximum number running back‐
743 ground jobs that can run at a time. When this limit is
744 reached, the shell will wait for a job to complete before
745 staring a new job.
746 LANG This variable determines the locale category for any cat‐
747 egory not specifically selected with a variable starting
748 with LC_ or LANG.
749 LC_ALL This variable overrides the value of the LANG variable
750 and any other LC_ variable.
751 LC_COLLATE
752 This variable determines the locale category for charac‐
753 ter collation information.
754 LC_CTYPE
755 This variable determines the locale category for charac‐
756 ter handling functions. It determines the character
757 classes for pattern matching (see File Name Generation
758 below).
759 LC_NUMERIC
760 This variable determines the locale category for the dec‐
761 imal point character.
762 LINES If this variable is set, the value is used to determine
763 the column length for printing select lists. Select
764 lists will print vertically until about two-thirds of
765 LINES lines are filled.
766 MAIL If this variable is set to the name of a mail file and
767 the MAILPATH variable is not set, then the shell informs
768 the user of arrival of mail in the specified file.
769 MAILCHECK
770 This variable specifies how often (in seconds) the shell
771 will check for changes in the modification time of any of
772 the files specified by the MAILPATH or MAIL variables.
773 The default value is 600 seconds. When the time has
774 elapsed the shell will check before issuing the next
775 prompt.
776 MAILPATH
777 A colon ( : ) separated list of file names. If this
778 variable is set, then the shell informs the user of any
779 modifications to the specified files that have occurred
780 within the last MAILCHECK seconds. Each file name can be
781 followed by a ? and a message that will be printed. The
782 message will undergo parameter expansion, command substi‐
783 tution, and arithmetic substitution with the variable $_
784 defined as the name of the file that has changed. The
785 default message is you have mail in $_.
786 PATH The search path for commands (see Execution below). The
787 user may not change PATH if executing under rksh (except
788 in .profile).
789 PS1 The value of this variable is expanded for parameter
790 expansion, command substitution, and arithmetic substitu‐
791 tion to define the primary prompt string which by default
792 is ``$''. The character ! in the primary prompt string
793 is replaced by the command number (see Command Re-entry
794 below). Two successive occurrences of ! will produce a
795 single ! when the prompt string is printed.
796 PS2 Secondary prompt string, by default ``> ''.
797 PS3 Selection prompt string used within a select loop, by
798 default ``#? ''.
799 PS4 The value of this variable is expanded for parameter
800 evaluation, command substitution, and arithmetic substi‐
801 tution and precedes each line of an execution trace. By
802 default, PS4 is ``+ ''. In addition when PS4 is unset,
803 the execution trace prompt is also ``+ ''.
804 SHELL The pathname of the shell is kept in the environment. At
805 invocation, if the basename of this variable is rsh,
806 rksh, or krsh, then the shell becomes restricted. If it
807 is pfsh or pfksh, then the shell becomes a profile shell
808 (see pfexec(1)).
809 TIMEFORMAT
810 The value of this parameter is used as a format string
811 specifying how the timing information for pipelines pre‐
812 fixed with the time reserved word should be displayed.
813 The % character introduces a format sequence that is
814 expanded to a time value or other information. The for‐
815 mat sequences and their meanings are as follows.
816 %% A literal %.
817 %[p][l]R The elapsed time in seconds.
818 %[p][l]U The number of CPU seconds spent in user mode.
819 %[p][l]S The number of CPU seconds spent in system mode.
820 %P The CPU percentage, computed as (U + S) / R.
821 The brackets denote optional portions. The optional p is
823 a digit specifying the precision, the number of frac‐
824 tional digits after a decimal point. A value of 0 causes
825 no decimal point or fraction to be output. At most three
826 places after the decimal point can be displayed; values
827 of p greater than 3 are treated as 3. If p is not speci‐
828 fied, the value 3 is used.
829 The optional l specifies a longer format, including hours
831 if greater than zero, minutes, and seconds of the form
832 HHhMMmSS.FFs. The value of p determines whether or not
833 the fraction is included.
834 All other characters are output without change and a
836 trailing newline is added. If unset, the default value,
837 $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS', is used. If the
838 value is null, no timing information is displayed.
839 TMOUT If set to a value greater than zero, TMOUT will be the
841 default timeout value for the read built-in command. The
842 select compound command terminates after TMOUT seconds
843 when input is from a terminal. Otherwise, the shell will
844 terminate if a line is not entered within the prescribed
845 number of seconds while reading from a terminal. (Note
846 that the shell can be compiled with a maximum bound for
847 this value which cannot be exceeded.)
848 VISUAL If the value of this variable matches the pattern
850 *[Vv][Ii]*, then the vi option (see Special Command set
851 below) is turned on. If the value matches the pattern
852 *gmacs* , the gmacs option is turned on. If the value
853 matches the pattern *macs*, then the emacs option will be
854 turned on. The value of VISUAL overrides the value of
855 EDITOR.
856 The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
858 FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set at
859 all by the shell (although HOME is set by login(1)). On some systems
860 MAIL and SHELL are also set by login(1).
861 Field Splitting.
863 After parameter expansion and command substitution, the results of sub‐
864 stitutions are scanned for the field separator characters (those found
865 in IFS) and split into distinct fields where such characters are found.
866 Explicit null fields ("" or ′′) are retained. Implicit null fields
867 (those resulting from parameters that have no values or command substi‐
868 tutions with no output) are removed.
869 If the braceexpand (-B) option is set then each of the fields resulting
871 from IFS are checked to see if they contain one or more of the brace
872 patterns {*,*}, {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,
873 or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are let‐
874 ters and n1,n2,n3 are signed numbers and fmt is a format specified as
875 used by printf. In each case, fields are created by prepending the
876 characters before the { and appending the characters after the } to
877 each of the strings generated by the characters between the { and }.
878 The resulting fields are checked to see if they have any brace pat‐
879 terns.
880 In the first form, a field is created for each string between { and ,,
882 between , and ,, and between , and }. The string represented by * can
883 contain embedded matching { and } without quoting. Otherwise, each {
884 and } with * must be quoted.
885 In the seconds form, l1 and l2 must both be either upper case or both
887 be lower case characters in the C locale. In this case a field is cre‐
888 ated for each character from l1 thru l2.
889 In the remaining forms, a field is created for each number starting at
891 n1 and continuing until it reaches n2 incrementing n1 by n3. The cases
892 where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 oth‐
893 erwise. If forms which specify %fmt any format flags, widths and pre‐
894 cisions can be specified and fmt can end in any of the specifiers
895 cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8
896 fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.
897 File Name Generation.
899 Following splitting, each field is scanned for the characters ∗, ?, (,
900 and [ unless the -f option has been set. If one of these characters
901 appears, then the word is regarded as a pattern. Each file name compo‐
902 nent that contains any pattern character is replaced with a lexico‐
903 graphically sorted set of names that matches the pattern from that
904 directory. If no file name is found that matches the pattern, then
905 that component of the filename is left unchanged unless the pattern is
906 prefixed with ∼(N) in which case it is removed as described below. If
907 FIGNORE is set, then each file name component that matches the pattern
908 defined by the value of FIGNORE is ignored when generating the matching
909 filenames. The names . and .. are also ignored. If FIGNORE is not
910 set, the character . at the start of each file name component will be
911 ignored unless the first character of the pattern corresponding to this
912 component is the character . itself. Note, that for other uses of
913 pattern matching the / and . are not treated specially.
914 ∗ Matches any string, including the null string. When used
916 for filename expansion, if the globstar option is on, two
917 adjacent ∗'s by itself will match all files and zero or
918 more directories and subdirectories. If followed by a /
919 then only directories and subdirectories will match.
920 ? Matches any single character.
921 [...] Matches any one of the enclosed characters. A pair of
922 characters separated by - matches any character lexically
923 between the pair, inclusive. If the first character fol‐
924 lowing the opening [ is a ! or ^ then any character not
925 enclosed is matched. A - can be included in the charac‐
926 ter set by putting it as the first or last character.
927 Within [ and ], character classes can be specified with
928 the syntax [:class:] where class is one of the following
929 classes defined in the ANSI-C standard: (Note that word
930 is equivalent to alnum plus the character _.)
931 alnum alpha blank cntrl digit graph lower print punct
932 space upper word xdigit
933 Within [ and ], an equivalence class can be specified
934 with the syntax [=c=] which matches all characters with
935 the same primary collation weight (as defined by the cur‐
936 rent locale) as the character c. Within [ and ], [.sym‐
937 bol.] matches the collating symbol symbol.
938 A pattern-list is a list of one or more patterns separated from each
939 other with a & or ⎪. A & signifies that all patterns must be matched
940 whereas ⎪ requires that only one pattern be matched. Composite pat‐
941 terns can be formed with one or more of the following sub-patterns:
942 ?(pattern-list)
943 Optionally matches any one of the given patterns.
944 *(pattern-list)
945 Matches zero or more occurrences of the given patterns.
946 +(pattern-list)
947 Matches one or more occurrences of the given patterns.
948 {n}(pattern-list)
949 Matches n occurrences of the given patterns.
950 {m,n}(pattern-list)
951 Matches from m to n occurrences of the given patterns.
952 If m is omitted, 0 will be used. If n is omitted at
953 least m occurrences will be matched.
954 @(pattern-list)
955 Matches exactly one of the given patterns.
956 !(pattern-list)
957 Matches anything except one of the given patterns.
958 By default, each pattern, or sub-pattern will match the longest string
959 possible consistent with generating the longest overall match. If more
960 than one match is possible, the one starting closest to the beginning
961 of the string will be chosen. However, for each of the above compound
962 patterns a - can be inserted in front of the ( to cause the shortest
963 match to the specified pattern-list to be used.
964 When pattern-list is contained within parentheses, the backslash char‐
966 acter \ is treated specially even when inside a character class. All
967 ANSI-C character escapes are recognized and match the specified charac‐
968 ter. In addition the following escape sequences are recognized:
969 \d Matches any character in the digit class.
970 \D Matches any character not in the digit class.
971 \s Matches any character in the space class.
972 \S Matches any character not in the space class.
973 \w Matches any character in the word class.
974 \W Matches any character not in the word class.
975 A pattern of the form %(pattern-pair(s)) is a sub-pattern that can be
977 used to match nested character expressions. Each pattern-pair is a two
978 character sequence which cannot contain & or ⎪. The first pattern-pair
979 specifies the starting and ending characters for the match. Each sub‐
980 sequent pattern-pair represents the beginning and ending characters of
981 a nested group that will be skipped over when counting starting and
982 ending character matches. The behavior is unspecified when the first
983 character of a pattern-pair is alpha-numeric except for the following:
984 D Causes the ending character to terminate the search for
985 this pattern without finding a match.
986 E Causes the ending character to be interpreted as an
987 escape character.
988 L Causes the ending character to be interpreted as a quote
989 character causing all characters to be ignored when look‐
990 ing for a match.
991 Q Causes the ending character to be interpreted as a quote
992 character causing all characters other than any escape
993 character to be ignored when looking for a match.
994 Thus, %({}Q"E\), matches characters starting at { until the matching }
995 is found not counting any { or } that is inside a double quoted string
996 or preceded by the escape character \. Without the {} this pattern
997 matches any C language string.
998 Each sub-pattern in a composite pattern is numbered, starting at 1, by
1000 the location of the ( within the pattern. The sequence \n, where n is
1001 a single digit and \n comes after the n-th. sub-pattern, matches the
1002 same string as the sub-pattern itself.
1003 Finally a pattern can contain sub-patterns of the form ∼(options:pat‐
1005 tern-list), where either options or :pattern-list can be omitted.
1006 Unlike the other compound patterns, these sub-patterns are not counted
1007 in the numbered sub-patterns. :pattern-list must be omitted for
1008 options F, G, N , and V below. If options is present, it can consist
1009 of one or more of the following:
1010 + Enable the following options. This is the default.
1011 - Disable the following options.
1012 E The remainder of the pattern uses extended regular
1013 expression syntax like the egrep(1) command.
1014 F The remainder of the pattern uses fgrep(1) expression
1015 syntax.
1016 G The remainder of the pattern uses basic regular expres‐
1017 sion syntax like the grep(1) command.
1018 K The remainder of the pattern uses shell pattern syntax.
1019 This is the default.
1020 N This is ignored. However, when it is the first letter
1021 and is used with file name generation, and no matches
1022 occur, the file pattern expands to the empty string.
1023 X The remainder of the pattern uses augmented regular
1024 expression syntax like the xgrep(1) command.
1025 P The remainder of the pattern uses perl(1) regular expres‐
1026 sion syntax. Not all perl regular expression syntax is
1027 currently implemented.
1028 V The remainder of the pattern uses System V regular
1029 expression syntax.
1030 i Treat the match as case insensitive.
1031 g File the longest match (greedy). This is the default.
1032 l Left anchor the pattern. This is the default for K style
1033 patterns.
1034 r Right anchor the pattern. This is the default for K
1035 style patterns.
1036 If both options and :pattern-list are specified, then the options apply
1037 only to pattern-list. Otherwise, these options remain in effect until
1038 they are disabled by a subsequent ∼(...) or at the end of the sub-pat‐
1039 tern containing ∼(...).
1040 Quoting.
1042 Each of the metacharacters listed earlier (see Definitions above) has a
1043 special meaning to the shell and causes termination of a word unless
1044 quoted. A character may be quoted (i.e., made to stand for itself) by
1045 preceding it with a \. The pair \new-line is removed. All characters
1046 enclosed between a pair of single quote marks (′′) that is not preceded
1047 by a $ are quoted. A single quote cannot appear within the single
1048 quotes. A single quoted string preceded by an unquoted $ is processed
1049 as an ANSI-C string except for the following:
1050 \0 Causes the remainder of the string to be ignored.
1051 \E Equivalent to the escape character (ascii 033),
1052 \e Equivalent to the escape character (ascii 033),
1053 \cx Expands to the character control-x.
1054 \C[.name.]
1055 Expands to the collating element name.
1056 Inside double quote marks (""), parameter and command substitution
1058 occur and \ quotes the characters \, `, ", and $. A $ in front of a
1059 double quoted string will be ignored in the "C" or "POSIX" locale, and
1060 may cause the string to be replaced by a locale specific string other‐
1061 wise. The meaning of $∗ and $@ is identical when not quoted or when
1062 used as a variable assignment value or as a file name. However, when
1063 used as a command argument, "$∗" is equivalent to "$1d$2d...", where d
1064 is the first character of the IFS variable, whereas "$@" is equivalent
1065 to "$1" "$2" .... Inside grave quote marks (``), \ quotes the charac‐
1066 ters \, `, and $. If the grave quotes occur within double quotes, then
1067 \ also quotes the character ".
1068 The special meaning of reserved words or aliases can be removed by
1070 quoting any character of the reserved word. The recognition of func‐
1071 tion names or built-in command names listed below cannot be altered by
1072 quoting them.
1073 Arithmetic Evaluation.
1075 The shell performs arithmetic evaluation for arithmetic substitution,
1076 to evaluate an arithmetic command, to evaluate an indexed array sub‐
1077 script, and to evaluate arguments to the built-in commands shift and
1078 let. Evaluations are performed using double precision floating point
1079 arithmetic or long double precision floating point for systems that
1080 provide this data type. Floating point constants follow the ANSI-C
1081 programming language floating point conventions. The floating point
1082 constants Nan and Inf can be use to represent "not a number" and infin‐
1083 ity respectively. Integer constants follow the ANSI-C programming lan‐
1084 guage integer constant conventions although only single byte character
1085 constants are recognized and character casts are not recognized. In
1086 addition constants can be of the form [base#]n where base is a decimal
1087 number between two and sixty-four representing the arithmetic base and
1088 n is a number in that base. The digits above 9 are represented by the
1089 lower case letters, the upper case letters, @, and _ respectively. For
1090 bases less than or equal to 36, upper and lower case characters can be
1091 used interchangeably.
1092 An arithmetic expression uses the same syntax, precedence, and associa‐
1094 tivity of expression as the C language. All the C language operators
1095 that apply to floating point quantities can be used. In addition, the
1096 operator ** can be used for exponentiation. It has higher precedence
1097 than multiplication and is left associative. In addition, when the
1098 value of an arithmetic variable or sub-expression can be represented as
1099 a long integer, all C language integer arithmetic operations can be
1100 performed. Variables can be referenced by name within an arithmetic
1101 expression without using the parameter expansion syntax. When a vari‐
1102 able is referenced, its value is evaluated as an arithmetic expression.
1103 Any of the following math library functions that are in the C math
1105 library can be used within an arithmetic expression:
1106 abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos cosh
1108 erf erfc exp exp2 expm1 fabs fpclassify fdim finite floor fma fmax fmin
1109 fmod hypot ilogb int isfinite sinf isnan isnormal issubnormal issubor‐
1110 dered iszero j0 j1 jn lgamma log log10 log2 logb nearbyint nextafter
1111 nexttoward pow remainder rint round scanb signbit sin sinh sqrt tan
1112 tanh tgamma trunc y0 y1 yn In addition, arithmetic functions can be
1113 define as shell functions with a variant of the function name syntax,
1114 function .sh.math.name ident ... { list ;}
1116 where name is the function name used in the arithmetic expres‐
1117 sion and each identifier, ident is a name reference to the long
1118 double precision floating point argument. The value of
1119 .sh.value when the function returns is the value of this func‐
1120 tion. User defined functions can take up to 3 arguments and
1121 override C math library functions.
1122 An internal representation of a variable as a double precision floating
1124 point can be specified with the -E [n], -F [n], or -X [n] option of the
1125 typeset special built-in command. The -E option causes the expansion
1126 of the value to be represented using scientific notation when it is
1127 expanded. The optional option argument n defines the number of signif‐
1128 icant figures. The -F option causes the expansion to be represented as
1129 a floating decimal number when it is expanded. The -X option cause the
1130 expansion to be represented using the %a format defined by ISO C-99.
1131 The optional option argument n defines the number of places after the
1132 decimal (or radix) point in this case.
1133 An internal integer representation of a variable can be specified with
1135 the -i [n] option of the typeset special built-in command. The
1136 optional option argument n specifies an arithmetic base to be used when
1137 expanding the variable. If you do not specify an arithmetic base, base
1138 10 will be used.
1139 Arithmetic evaluation is performed on the value of each assignment to a
1141 variable with the -E, -F, -X, or -i attribute. Assigning a floating
1142 point number to a variable whose type is an integer causes the frac‐
1143 tional part to be truncated.
1144 Prompting.
1146 When used interactively, the shell prompts with the value of PS1 after
1147 expanding it for parameter expansion, command substitution, and arith‐
1148 metic substitution, before reading a command. In addition, each single
1149 ! in the prompt is replaced by the command number. A !! is required
1150 to place ! in the prompt. If at any time a new-line is typed and fur‐
1151 ther input is needed to complete a command, then the secondary prompt
1152 (i.e., the value of PS2) is issued.
1153 Conditional Expressions.
1155 A conditional expression is used with the [[ compound command to test
1156 attributes of files and to compare strings. Field splitting and file
1157 name generation are not performed on the words between [[ and ]]. Each
1158 expression can be constructed from one or more of the following unary
1159 or binary expressions:
1160 string True, if string is not null.
1161 -a file
1162 Same as -e below. This is obsolete.
1163 -b file
1164 True, if file exists and is a block special file.
1165 -c file
1166 True, if file exists and is a character special file.
1167 -d file
1168 True, if file exists and is a directory.
1169 -e file
1170 True, if file exists.
1171 -f file
1172 True, if file exists and is an ordinary file.
1173 -g file
1174 True, if file exists and it has its setgid bit set.
1175 -k file
1176 True, if file exists and it has its sticky bit set.
1177 -n string
1178 True, if length of string is non-zero.
1179 -o ?option
1180 True, if option named option is a valid option name.
1181 -o option
1182 True, if option named option is on.
1183 -p file
1184 True, if file exists and is a fifo special file or a pipe.
1185 -r file
1186 True, if file exists and is readable by current process.
1187 -s file
1188 True, if file exists and has size greater than zero.
1189 -t fildes
1190 True, if file descriptor number fildes is open and associated
1191 with a terminal device.
1192 -u file
1193 True, if file exists and it has its setuid bit set.
1194 -v name
1195 True, if variable name is a valid variable name and is set.
1196 -w file
1197 True, if file exists and is writable by current process.
1198 -x file
1199 True, if file exists and is executable by current process. If
1200 file exists and is a directory, then true if the current process
1201 has permission to search in the directory.
1202 -z string
1203 True, if length of string is zero.
1204 -L file
1205 True, if file exists and is a symbolic link.
1206 -h file
1207 True, if file exists and is a symbolic link.
1208 -N file
1209 True, if file exists and the modification time is greater than
1210 the last access time.
1211 -O file
1212 True, if file exists and is owned by the effective user id of
1213 this process.
1214 -G file
1215 True, if file exists and its group matches the effective group
1216 id of this process.
1217 -R name
1218 True if variable name is a name reference.
1219 -S file
1220 True, if file exists and is a socket.
1221 file1 -nt file2
1222 True, if file1 exists and file2 does not, or file1 is newer than
1223 file2.
1224 file1 -ot file2
1225 True, if file2 exists and file1 does not, or file1 is older than
1226 file2.
1227 file1 -ef file2
1228 True, if file1 and file2 exist and refer to the same file.
1229 string == pattern
1230 True, if string matches pattern. Any part of pattern can be
1231 quoted to cause it to be matched as a string. With a successful
1232 match to a pattern, the .sh.match array variable will contain
1233 the match and sub-pattern matches.
1234 string = pattern
1235 Same as == above, but is obsolete.
1236 string != pattern
1237 True, if string does not match pattern. When the string matches
1238 the pattern the .sh.match array variable will contain the match
1239 and sub-pattern matches.
1240 string =∼ ere
1241 True if string matches the pattern ∼(E)ere where ere is an
1242 extended regular expression.
1243 string1 < string2
1244 True, if string1 comes before string2 based on ASCII value of
1245 their characters.
1246 string1 > string2
1247 True, if string1 comes after string2 based on ASCII value of
1248 their characters.
1249 The following obsolete arithmetic comparisons are also permitted:
1250 exp1 -eq exp2
1251 True, if exp1 is equal to exp2.
1252 exp1 -ne exp2
1253 True, if exp1 is not equal to exp2.
1254 exp1 -lt exp2
1255 True, if exp1 is less than exp2.
1256 exp1 -gt exp2
1257 True, if exp1 is greater than exp2.
1258 exp1 -le exp2
1259 True, if exp1 is less than or equal to exp2.
1260 exp1 -ge exp2
1261 True, if exp1 is greater than or equal to exp2.
1262 In each of the above expressions, if file is of the form /dev/fd/n,
1264 where n is an integer, then the test is applied to the open file whose
1265 descriptor number is n.
1266 A compound expression can be constructed from these primitives by using
1268 any of the following, listed in decreasing order of precedence.
1269 (expression)
1270 True, if expression is true. Used to group expressions.
1271 ! expression
1272 True if expression is false.
1273 expression1 && expression2
1274 True, if expression1 and expression2 are both true.
1275 expression1 ⎪⎪ expression2
1276 True, if either expression1 or expression2 is true.
1277 Input/Output.
1279 Before a command is executed, its input and output may be redirected
1280 using a special notation interpreted by the shell. The following may
1281 appear anywhere in a simple-command or may precede or follow a command
1282 and are not passed on to the invoked command. Command substitution,
1283 parameter expansion, and arithmetic substitution occur before word or
1284 digit is used except as noted below. File name generation occurs only
1285 if the shell is interactive and the pattern matches a single file.
1286 Field splitting is not performed.
1287 In each of the following redirections, if file is of the form
1289 /dev/sctp/host/port, /dev/tcp/host/port, or /dev/udp/host/port, where
1290 host is a hostname or host address, and port is a service given by name
1291 or an integer port number, then the redirection attempts to make a tcp,
1292 sctp or udp connection to the corresponding socket.
1293 No intervening space is allowed between the characters of redirection
1295 operators.
1296 <word Use file word as standard input (file descriptor 0).
1298 >word Use file word as standard output (file descriptor 1). If
1300 the file does not exist then it is created. If the file
1301 exists, and the noclobber option is on, this causes an
1302 error; otherwise, it is truncated to zero length.
1303 >|word Same as >, except that it overrides the noclobber option.
1305 >;word Write output to a temporary file. If the command com‐
1307 pletes successfully rename it to word, otherwise, delete
1308 the temporary file. >;word cannot be used with the
1309 exec(2). built-in.
1310 >>word Use file word as standard output. If the file exists,
1312 then output is appended to it (by first seeking to the
1313 end-of-file); otherwise, the file is created.
1314 <>word Open file word for reading and writing as standard out‐
1316 put.
1317 <>;word The same as <>word except that if the command completes
1319 successfully, word is truncated to the offset at command
1320 completion. <>;word cannot be used with the exec(2).
1321 built-in.
1322 <<[-]word The shell input is read up to a line that is the same as
1324 word after any quoting has been removed, or to an end-of-
1325 file. No parameter substitution, command substitution,
1326 arithmetic substitution or file name generation is per‐
1327 formed on word. The resulting document, called a here-
1328 document, becomes the standard input. If any character
1329 of word is quoted, then no interpretation is placed upon
1330 the characters of the document; otherwise, parameter
1331 expansion, command substitution, and arithmetic substitu‐
1332 tion occur, \new-line is ignored, and \ must be used to
1333 quote the characters \, $, `. If - is appended to <<,
1334 then all leading tabs are stripped from word and from the
1335 document. If # is appended to <<, then leading spaces
1336 and tabs will be stripped off the first line of the docu‐
1337 ment and up to an equivalent indentation will be stripped
1338 from the remaining lines and from word. A tab stop is
1339 assumed to occur at every 8 columns for the purposes of
1340 determining the indentation.
1341 <<<word A short form of here document in which word becomes the
1343 contents of the here-document after any parameter expan‐
1344 sion, command substitution, and arithmetic substitution
1345 occur.
1346 <&digit The standard input is duplicated from file descriptor
1348 digit (see dup(2)). Similarly for the standard output
1349 using >&digit.
1350 <&digit- The file descriptor given by digit is moved to standard
1352 input. Similarly for the standard output using >&digit-.
1353 <&- The standard input is closed. Similarly for the standard
1355 output using >&-.
1356 <&p The input from the co-process is moved to standard input.
1358 >&p The output to the co-process is moved to standard output.
1360 <#((expr)) Evaluate arithmetic expression expr and position file
1362 descriptor 0 to the resulting value bytes from the start
1363 of the file. The variables CUR and EOF evaluate to the
1364 current offset and end-of-file offset respectively when
1365 evaluating expr.
1366 >#((offset)) The same as <# except applies to file descriptor 1.
1368 <#pattern Seeks forward to the beginning of the next line contain‐
1370 ing pattern.
1371 <##pattern The same as <# except that the portion of the file that
1373 is skipped is copied to standard output.
1374 If one of the above is preceded by a digit, with no intervening space,
1376 then the file descriptor number referred to is that specified by the
1377 digit (instead of the default 0 or 1). If one of the above, other than
1378 >&- and the ># and <# forms, is preceded by {varname} with no interven‐
1379 ing space, then a file descriptor number > 10 will be selected by the
1380 shell and stored in the variable varname. If >&- or the any of the >#
1381 and <# forms is preceded by {varname} the value of varname defines the
1382 file descriptor to close or position. For example:
1383 ... 2>&1
1385 means file descriptor 2 is to be opened for writing as a duplicate of
1387 file descriptor 1 and
1388 exec {n}<file
1390 means open file named file for reading and store the file descriptor
1392 number in variable n.
1393 The order in which redirections are specified is significant. The
1395 shell evaluates each redirection in terms of the (file descriptor,
1396 file) association at the time of evaluation. For example:
1397 ... 1>fname 2>&1
1399 first associates file descriptor 1 with file fname. It then associates
1401 file descriptor 2 with the file associated with file descriptor 1 (i.e.
1402 fname). If the order of redirections were reversed, file descriptor 2
1403 would be associated with the terminal (assuming file descriptor 1 had
1404 been) and then file descriptor 1 would be associated with file fname.
1405 If a command is followed by & and job control is not active, then the
1407 default standard input for the command is the empty file /dev/null.
1408 Otherwise, the environment for the execution of a command contains the
1409 file descriptors of the invoking shell as modified by input/output
1410 specifications.
1411 Environment.
1413 The environment (see environ(7)) is a list of name-value pairs that is
1414 passed to an executed program in the same way as a normal argument
1415 list. The names must be identifiers and the values are character
1416 strings. The shell interacts with the environment in several ways. On
1417 invocation, the shell scans the environment and creates a variable for
1418 each name found, giving it the corresponding value and attributes and
1419 marking it export. Executed commands inherit the environment. If the
1420 user modifies the values of these variables or creates new ones, using
1421 the export or typeset -x commands, they become part of the environment.
1422 The environment seen by any executed command is thus composed of any
1423 name-value pairs originally inherited by the shell, whose values may be
1424 modified by the current shell, plus any additions which must be noted
1425 in export or typeset -x commands.
1426 The environment for any simple-command or function may be augmented by
1428 prefixing it with one or more variable assignments. A variable assign‐
1429 ment argument is a word of the form identifier=value. Thus:
1430 TERM=450 cmd args and
1432 (export TERM; TERM=450; cmd args)
1433 are equivalent (as far as the above execution of cmd is concerned
1435 except for special built-in commands listed below - those that are pre‐
1436 ceded with a dagger).
1437 If the obsolete -k option is set, all variable assignment arguments are
1439 placed in the environment, even if they occur after the command name.
1440 The following first prints a=b c and then c:
1441 echo a=b c
1443 set -k
1444 echo a=b c
1445 This feature is intended for use with scripts written for early ver‐
1446 sions of the shell and its use in new scripts is strongly discouraged.
1447 It is likely to disappear someday.
1448 Functions.
1450 For historical reasons, there are two ways to define functions, the
1451 name() syntax and the function name syntax, described in the Commands
1452 section above. Shell functions are read in and stored internally.
1453 Alias names are resolved when the function is read. Functions are exe‐
1454 cuted like commands with the arguments passed as positional parameters.
1455 (See Execution below.)
1456 Functions defined by the function name syntax and called by name exe‐
1458 cute in the same process as the caller and share all files and present
1459 working directory with the caller. Traps caught by the caller are
1460 reset to their default action inside the function. A trap condition
1461 that is not caught or ignored by the function causes the function to
1462 terminate and the condition to be passed on to the caller. A trap on
1463 EXIT set inside a function is executed in the environment of the caller
1464 after the function completes. Ordinarily, variables are shared between
1465 the calling program and the function. However, the typeset special
1466 built-in command used within a function defines local variables whose
1467 scope includes the current function. They can be passed to functions
1468 that they call in the variable assignment list that precedes the call
1469 or as arguments passed as name references. Errors within functions
1470 return control to the caller.
1471 Functions defined with the name() syntax and functions defined with the
1473 function name syntax that are invoked with the . special built-in are
1474 executed in the caller's environment and share all variables and traps
1475 with the caller. Errors within these function executions cause the
1476 script that contains them to abort.
1477 The special built-in command return is used to return from function
1479 calls.
1480 Function names can be listed with the -f or +f option of the typeset
1482 special built-in command. The text of functions, when available, will
1483 also be listed with -f. Functions can be undefined with the -f option
1484 of the unset special built-in command.
1485 Ordinarily, functions are unset when the shell executes a shell script.
1487 Functions that need to be defined across separate invocations of the
1488 shell should be placed in a directory and the FPATH variable should
1489 contain the name of this directory. They may also be specified in the
1490 ENV file.
1491 Discipline Functions.
1493 Each variable can have zero or more discipline functions associated
1494 with it. The shell initially understands the discipline names get,
1495 set, append, and unset but can be added when defining new types. On
1496 most systems others can be added at run time via the C programming
1497 interface extension provided by the builtin built-in utility. If the
1498 get discipline is defined for a variable, it is invoked whenever the
1499 given variable is referenced. If the variable .sh.value is assigned a
1500 value inside the discipline function, the referenced variable will
1501 evaluate to this value instead. If the set discipline is defined for a
1502 variable, it is invoked whenever the given variable is assigned a
1503 value. If the append discipline is defined for a variable, it is
1504 invoked whenever a value is appended to the given variable. The vari‐
1505 able .sh.value is given the value of the variable before invoking the
1506 discipline, and the variable will be assigned the value of .sh.value
1507 after the discipline completes. If .sh.value is unset inside the dis‐
1508 cipline, then that value is unchanged. If the unset discipline is
1509 defined for a variable, it is invoked whenever the given variable is
1510 unset. The variable will not be unset unless it is unset explicitly
1511 from within this discipline function.
1512 The variable .sh.name contains the name of the variable for which the
1514 discipline function is called, .sh.subscript is the subscript of the
1515 variable, and .sh.value will contain the value being assigned inside
1516 the set discipline function. The variable _ is a reference to the
1517 variable including the subscript if any. For the set discipline,
1518 changing .sh.value will change the value that gets assigned. Finally,
1519 the expansion ${var.name}, when name is the name of a discipline, and
1520 there is no variable of this name, is equivalent to the command substi‐
1521 tution ${ var.name;}.
1522 Name Spaces.
1525 Commands and functions that are executed as part of the list of a
1526 namespace command that modify variables or create new ones, create a
1527 new variable whose name is the name of the name space as given by iden‐
1528 tifier preceded by .. When a variable whose name is name is refer‐
1529 enced, it is first searched for using .identifier.name. Similarly, a
1530 function defined by a command in the namespace list is created using
1531 the name space name preceded by a ..
1532 When the list of a namespace command contains a namespace command, the
1534 names of variables and functions that are created consist of the vari‐
1535 able or function name preceded by the list of identifiers each preceded
1536 by ..
1537 Outside of a name space, a variable or function created inside a name
1539 space can be referenced by preceding it with the name space name.
1540 By default, variables staring with .sh are in the sh name space.
1542 Type Variables.
1545 Typed variables provide a way to create data structure and objects. A
1546 type can be defined either by a shared library, by the enum built-in
1547 command described below, or by using the new -T option of the typeset
1548 built-in command. With the -T option of typeset, the type name, speci‐
1549 fied as an option argument to -T, is set with a compound variable
1550 assignment that defines the type. Function definitions can appear
1551 inside the compound variable assignment and these become discipline
1552 functions for this type and can be invoked or redefined by each
1553 instance of the type. The function name create is treated specially.
1554 It is invoked for each instance of the type that is created but is not
1555 inherited and cannot be redefined for each instance.
1556 When a type is defined a special built-in command of that name is
1558 added. These built-ins are declaration commands and follow the same
1559 expansion rules as all the special built-in commands defined below that
1560 are preceded by ††. These commands can subsequently be used inside
1561 further type definitions. The man page for these commands can be gen‐
1562 erated by using the --man option or any of the other -- options
1563 described with getopts. The -r, -a, -A, -h, and -S options of typeset
1564 are permitted with each of these new built-ins.
1565 An instance of a type is created by invoking the type name followed by
1567 one or more instance names. Each instance of the type is initialized
1568 with a copy of the sub-variables except for sub-variables that are
1569 defined with the -S option. Variables defined with the -S are shared
1570 by all instances of the type. Each instance can change the value of
1571 any sub-variable and can also define new discipline functions of the
1572 same names as those defined by the type definition as well as any stan‐
1573 dard discipline names. No additional sub-variables can be defined for
1574 any instance.
1575 When defining a type, if the value of a sub-variable is not set and the
1577 -r attribute is specified, it causes the sub-variable to be a required
1578 sub-variable. Whenever an instance of a type is created, all required
1579 sub-variables must be specified. These sub-variables become readonly
1580 in each instance.
1581 When unset is invoked on a sub-variable within a type, and the -r
1583 attribute has not been specified for this field, the value is reset to
1584 the default value associative with the type. Invoking unset on a type
1585 instance not contained within another type deletes all sub-variables
1586 and the variable itself.
1587 A type definition can be derived from another type definition by defin‐
1589 ing the first sub-variable name as _ and defining its type as the base
1590 type. Any remaining definitions will be additions and modifications
1591 that apply to the new type. If the new type name is the same is that
1592 of the base type, the type will be replaced and the original type will
1593 no longer be accessible.
1594 The typeset command with the -T and no option argument or operands will
1596 write all the type definitions to standard output in a form that that
1597 can be read in to create all they types.
1598 Jobs.
1600 If the monitor option of the set command is turned on, an interactive
1601 shell associates a job with each pipeline. It keeps a table of current
1602 jobs, printed by the jobs command, and assigns them small integer num‐
1603 bers. When a job is started asynchronously with &, the shell prints a
1604 line which looks like:
1605 [1] 1234
1607 indicating that the job which was started asynchronously was job number
1609 1 and had one (top-level) process, whose process id was 1234.
1610 This paragraph and the next require features that are not in all ver‐
1612 sions of UNIX and may not apply. If you are running a job and wish to
1613 do something else you may hit the key ^Z (control-Z) which sends a STOP
1614 signal to the current job. The shell will then normally indicate that
1615 the job has been `Stopped', and print another prompt. You can then
1616 manipulate the state of this job, putting it in the background with the
1617 bg command, or run some other commands and then eventually bring the
1618 job back into the foreground with the foreground command fg. A ^Z
1619 takes effect immediately and is like an interrupt in that pending out‐
1620 put and unread input are discarded when it is typed.
1621 A job being run in the background will stop if it tries to read from
1623 the terminal. Background jobs are normally allowed to produce output,
1624 but this can be disabled by giving the command stty tostop. If you set
1625 this tty option, then background jobs will stop when they try to pro‐
1626 duce output like they do when they try to read input.
1627 A job pool is a collection of jobs started with list & associated with
1629 a name.
1630 There are several ways to refer to jobs in the shell. A job can be
1632 referred to by the process id of any process of the job or by one of
1633 the following:
1634 %number
1635 The job with the given number.
1636 pool All the jobs in the job pool named by pool.
1637 pool.number
1638 The job number number in the job pool named by pool.
1639 %string
1640 Any job whose command line begins with string.
1641 %?string
1642 Any job whose command line contains string.
1643 %% Current job.
1644 %+ Equivalent to %%.
1645 %- Previous job. In addition, unless noted otherwise, wherever a
1646 job can be specified, the name of a background job pool can be
1647 used to represent all the jobs in that pool.
1648 The shell learns immediately whenever a process changes state. It nor‐
1650 mally informs you whenever a job becomes blocked so that no further
1651 progress is possible, but only just before it prints a prompt. This is
1652 done so that it does not otherwise disturb your work. The notify
1653 option of the set command causes the shell to print these job change
1654 messages as soon as they occur.
1655 When the monitor option is on, each background job that completes trig‐
1657 gers any trap set for CHLD.
1658 When you try to leave the shell while jobs are running or stopped, you
1660 will be warned that `You have stopped(running) jobs.' You may use the
1661 jobs command to see what they are. If you immediately try to exit
1662 again, the shell will not warn you a second time, and the stopped jobs
1663 will be terminated. When a login shell receives a HUP signal, it sends
1664 a HUP signal to each job that has not been disowned with the disown
1665 built-in command described below.
1666 Signals.
1668 The INT and QUIT signals for an invoked command are ignored if the com‐
1669 mand is followed by & and the monitor option is active. Otherwise,
1670 signals have the values inherited by the shell from its parent (but see
1671 also the trap built-in command below).
1672 Execution.
1674 Each time a command is read, the above substitutions are carried out.
1675 If the command name matches one of the Special Built-in Commands listed
1676 below, it is executed within the current shell process. Next, the com‐
1677 mand name is checked to see if it matches a user defined function. If
1678 it does, the positional parameters are saved and then reset to the
1679 arguments of the function call. A function is also executed in the
1680 current shell process. When the function completes or issues a return,
1681 the positional parameter list is restored. For functions defined with
1682 the function name syntax, any trap set on EXIT within the function is
1683 executed. The exit value of a function is the value of the last com‐
1684 mand executed. If a command name is not a special built-in command or
1685 a user defined function, but it is one of the built-in commands listed
1686 below, it is executed in the current shell process.
1687 The shell variables PATH followed by the variable FPATH defines the
1689 list of directories to search for the command name. Alternative direc‐
1690 tory names are separated by a colon (:). The default path is equal to
1691 getconf PATH output. The current directory can be specified by two or
1692 more adjacent colons, or by a colon at the beginning or end of the path
1693 list. If the command name contains a /, then the search path is not
1694 used. Otherwise, each directory in the list of directories defined by
1695 PATH and FPATH is checked in order. If the directory being searched is
1696 contained in FPATH and contains a file whose name matches the command
1697 being searched, then this file is loaded into the current shell envi‐
1698 ronment as if it were the argument to the . command except that only
1699 preset aliases are expanded, and a function of the given name is exe‐
1700 cuted as described above.
1701 If this directory is not in FPATH the shell first determines whether
1703 there is a built-in version of a command corresponding to a given path‐
1704 name and if so it is invoked in the current process. If no built-in is
1705 found, the shell checks for a file named .paths in this directory. If
1706 found and there is a line of the form FPATH=path where path names an
1707 existing directory then that directory is searched after immediately
1708 after the current directory as if it were found in the FPATH variable.
1709 If path does not begin with /, it is checked for relative to the direc‐
1710 tory being searched.
1711 The .paths file is then checked for a line of the form PLUGIN_LIB=lib‐
1713 name [ : libname ] ... . Each library named by libname will be
1714 searched for as if it were an option argument to builtin -f, and if it
1715 contains a built-in of the specified name this will be executed instead
1716 of a command by this name. Any built-in loaded from a library found
1717 this way will be associated with the directory containing the .paths
1718 file so it will only execute if not found in an earlier directory.
1719 Finally, the directory will be checked for a file of the given name.
1721 If the file has execute permission but is not an a.out file, it is
1722 assumed to be a file containing shell commands. A separate shell is
1723 spawned to read it. All non-exported variables are removed in this
1724 case. If the shell command file doesn't have read permission, or if
1725 the setuid and/or setgid bits are set on the file, then the shell exe‐
1726 cutes an agent whose job it is to set up the permissions and execute
1727 the shell with the shell command file passed down as an open file. If
1728 the .paths contains a line of the form name=value in the first or sec‐
1729 ond line, then the environment variable name is modified by prepending
1730 the directory specified by value to the directory list. If value is
1731 not an absolute directory, then it specifies a directory relative to
1732 the directory that the executable was found. If the environment vari‐
1733 able name does not already exist it will be added to the environment
1734 list for the specified command. A parenthesized command is executed in
1735 a sub-shell without removing non-exported variables.
1736 Command Re-entry.
1738 The text of the last HISTSIZE (default 512) commands entered from a
1739 terminal device is saved in a history file. The file $HOME/.sh_history
1740 is used if the HISTFILE variable is not set or if the file it names is
1741 not writable. A shell can access the commands of all interactive
1742 shells which use the same named HISTFILE. The built-in command hist is
1743 used to list or edit a portion of this file. The portion of the file
1744 to be edited or listed can be selected by number or by giving the first
1745 character or characters of the command. A single command or range of
1746 commands can be specified. If you do not specify an editor program as
1747 an argument to hist then the value of the variable HISTEDIT is used.
1748 If HISTEDIT is unset, the obsolete variable FCEDIT is used. If FCEDIT
1749 is not defined, then /bin/ed is used. The edited command(s) is printed
1750 and re-executed upon leaving the editor unless you quit without writ‐
1751 ing. The -s option (and in obsolete versions, the editor name -) is
1752 used to skip the editing phase and to re-execute the command. In this
1753 case a substitution parameter of the form old=new can be used to modify
1754 the command before execution. For example, with the preset alias r,
1755 which is aliased to ′hist -s′, typing `r bad=good c' will re-execute
1756 the most recent command which starts with the letter c, replacing the
1757 first occurrence of the string bad with the string good.
1758 In-line Editing Options.
1760 Normally, each command line entered from a terminal device is simply
1761 typed followed by a new-line (`RETURN' or `LINE FEED'). If either the
1762 emacs, gmacs, or vi option is active, the user can edit the command
1763 line. To be in either of these edit modes set the corresponding
1764 option. An editing option is automatically selected each time the VIS‐
1765 UAL or EDITOR variable is assigned a value ending in either of these
1766 option names.
1767 The editing features require that the user's terminal accept `RETURN'
1769 as carriage return without line feed and that a space (` ') must over‐
1770 write the current character on the screen.
1771 Unless the multiline option is on, the editing modes implement a con‐
1773 cept where the user is looking through a window at the current line.
1774 The window width is the value of COLUMNS if it is defined, otherwise
1775 80. If the window width is too small to display the prompt and leave
1776 at least 8 columns to enter input, the prompt is truncated from the
1777 left. If the line is longer than the window width minus two, a mark is
1778 displayed at the end of the window to notify the user. As the cursor
1779 moves and reaches the window boundaries the window will be centered
1780 about the cursor. The mark is a > (<, *) if the line extends on the
1781 right (left, both) side(s) of the window.
1782 The search commands in each edit mode provide access to the history
1784 file. Only strings are matched, not patterns, although a leading ^ in
1785 the string restricts the match to begin at the first character in the
1786 line.
1787 Each of the edit modes has an operation to list the files or commands
1789 that match a partially entered word. When applied to the first word on
1790 the line, or the first word after a ;, ⎪, &, or (, and the word does
1791 not begin with ∼ or contain a /, the list of aliases, functions, and
1792 executable commands defined by the PATH variable that could match the
1793 partial word is displayed. Otherwise, the list of files that match the
1794 given word is displayed. If the partially entered word does not con‐
1795 tain any file expansion characters, a * is appended before generating
1796 these lists. After displaying the generated list, the input line is
1797 redrawn. These operations are called command name listing and file
1798 name listing, respectively. There are additional operations, referred
1799 to as command name completion and file name completion, which compute
1800 the list of matching commands or files, but instead of printing the
1801 list, replace the current word with a complete or partial match. For
1802 file name completion, if the match is unique, a / is appended if the
1803 file is a directory and a space is appended if the file is not a direc‐
1804 tory. Otherwise, the longest common prefix for all the matching files
1805 replaces the word. For command name completion, only the portion of
1806 the file names after the last / are used to find the longest command
1807 prefix. If only a single name matches this prefix, then the word is
1808 replaced with the command name followed by a space. When using a tab
1809 for completion that does not yield a unique match, a subsequent tab
1810 will provide a numbered list of matching alternatives. A specific
1811 selection can be made by entering the selection number followed by a
1812 tab.
1813 Key Bindings.
1815 The KEYBD trap can be used to intercept keys as they are typed and
1816 change the characters that are actually seen by the shell. This trap
1817 is executed after each character (or sequence of characters when the
1818 first character is ESC) is entered while reading from a terminal. The
1819 variable .sh.edchar contains the character or character sequence which
1820 generated the trap. Changing the value of .sh.edchar in the trap
1821 action causes the shell to behave as if the new value were entered from
1822 the keyboard rather than the original value.
1823 The variable .sh.edcol is set to the input column number of the cursor
1825 at the time of the input. The variable .sh.edmode is set to ESC when
1826 in vi insert mode (see below) and is null otherwise. By prepending
1827 ${.sh.editmode} to a value assigned to .sh.edchar it will cause the
1828 shell to change to control mode if it is not already in this mode.
1829 This trap is not invoked for characters entered as arguments to editing
1831 directives, or while reading input for a character search.
1832 Emacs Editing Mode.
1834 This mode is entered by enabling either the emacs or gmacs option. The
1835 only difference between these two modes is the way they handle ^T. To
1836 edit, the user moves the cursor to the point needing correction and
1837 then inserts or deletes characters or words as needed. All the editing
1838 commands are control characters or escape sequences. The notation for
1839 control characters is caret (^) followed by the character. For exam‐
1840 ple, ^F is the notation for control F. This is entered by depressing
1841 `f' while holding down the `CTRL' (control) key. The `SHIFT' key is
1842 not depressed. (The notation ^? indicates the DEL (delete) key.)
1843 The notation for escape sequences is M- followed by a character. For
1845 example, M-f (pronounced Meta f) is entered by depressing ESC (ascii
1846 033) followed by `f'. (M-F would be the notation for ESC followed by
1847 `SHIFT' (capital) `F'.)
1848 All edit commands operate from any place on the line (not just at the
1850 beginning). Neither the `RETURN' nor the `LINE FEED' key is entered
1851 after edit commands except when noted.
1852 ^F Move cursor forward (right) one character.
1854 M-[C Move cursor forward (right) one character.
1855 M-f Move cursor forward one word. (The emacs editor's idea of a
1856 word is a string of characters consisting of only letters,
1857 digits and underscores.)
1858 ^B Move cursor backward (left) one character.
1859 M-[D Move cursor backward (left) one character.
1860 M-b Move cursor backward one word.
1861 ^A Move cursor to start of line.
1862 M-[H Move cursor to start of line.
1863 ^E Move cursor to end of line.
1864 M-[Y Move cursor to end of line.
1865 ^]char Move cursor forward to character char on current line.
1866 M-^]char Move cursor backward to character char on current line.
1867 ^X^X Interchange the cursor and mark.
1868 erase (User defined erase character as defined by the stty(1) com‐
1869 mand, usually ^H or #.) Delete previous character.
1870 lnext (User defined literal next character as defined by the
1871 stty(1) command, or ^V if not defined.) Removes the next
1872 character's editing features (if any).
1873 ^D Delete current character.
1874 M-d Delete current word.
1875 M-^H (Meta-backspace) Delete previous word.
1876 M-h Delete previous word.
1877 M-^? (Meta-DEL) Delete previous word (if your interrupt character
1878 is ^? (DEL, the default) then this command will not work).
1879 ^T Transpose current character with previous character and
1880 advance the cursor in emacs mode. Transpose two previous
1881 characters in gmacs mode.
1882 ^C Capitalize current character.
1883 M-c Capitalize current word.
1884 M-l Change the current word to lower case.
1885 ^K Delete from the cursor to the end of the line. If preceded
1886 by a numerical parameter whose value is less than the current
1887 cursor position, then delete from given position up to the
1888 cursor. If preceded by a numerical parameter whose value is
1889 greater than the current cursor position, then delete from
1890 cursor up to given cursor position.
1891 ^W Kill from the cursor to the mark.
1892 M-p Push the region from the cursor to the mark on the stack.
1893 kill (User defined kill character as defined by the stty command,
1894 usually ^G or @.) Kill the entire current line. If two kill
1895 characters are entered in succession, all kill characters
1896 from then on cause a line feed (useful when using paper ter‐
1897 minals).
1898 ^Y Restore last item removed from line. (Yank item back to the
1899 line.)
1900 ^L Line feed and print current line.
1901 M-^L Clear the screen.
1902 ^@ (Null character) Set mark.
1903 M-space (Meta space) Set mark.
1904 ^J (New line) Execute the current line.
1905 ^M (Return) Execute the current line.
1906 eof End-of-file character, normally ^D, is processed as an End-
1907 of-file only if the current line is null.
1908 ^P Fetch previous command. Each time ^P is entered the previous
1909 command back in time is accessed. Moves back one line when
1910 not on the first line of a multi-line command.
1911 M-[A If the cursor is at the end of the line, it is equivalent to
1912 ^R with string set to the contents of the current line. Oth‐
1913 erwise, it is equivalent to ^P.
1914 M-< Fetch the least recent (oldest) history line.
1915 M-> Fetch the most recent (youngest) history line.
1916 ^N Fetch next command line. Each time ^N is entered the next
1917 command line forward in time is accessed.
1918 M-[B Equivalent to ^N.
1919 ^Rstring Reverse search history for a previous command line containing
1920 string. If a parameter of zero is given, the search is for‐
1921 ward. String is terminated by a `RETURN' or `NEW LINE'. If
1922 string is preceded by a ^, the matched line must begin with
1923 string. If string is omitted, then the next command line
1924 containing the most recent string is accessed. In this case
1925 a parameter of zero reverses the direction of the search.
1926 ^O Operate - Execute the current line and fetch the next line
1927 relative to current line from the history file.
1928 M-digits (Escape) Define numeric parameter, the digits are taken as a
1929 parameter to the next command. The commands that accept a
1930 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
1931 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
1932 M-letter Soft-key - Your alias list is searched for an alias by the
1933 name _letter and if an alias of this name is defined, its
1934 value will be inserted on the input queue. The letter must
1935 not be one of the above meta-functions.
1936 M-[letter Soft-key - Your alias list is searched for an alias by the
1937 name __letter and if an alias of this name is defined, its
1938 value will be inserted on the input queue. This can be used
1939 to program function keys on many terminals.
1940 M-. The last word of the previous command is inserted on the
1941 line. If preceded by a numeric parameter, the value of this
1942 parameter determines which word to insert rather than the
1943 last word.
1944 M-_ Same as M-..
1945 M-* Attempt file name generation on the current word. An aster‐
1946 isk is appended if the word doesn't match any file or contain
1947 any special pattern characters.
1948 M-ESC Command or file name completion as described above.
1949 ^I tab Attempts command or file name completion as described above.
1950 If a partial completion occurs, repeating this will behave as
1951 if M-= were entered. If no match is found or entered after
1952 space, a tab is inserted.
1953 M-= If not preceded by a numeric parameter, it generates the list
1954 of matching commands or file names as described above. Oth‐
1955 erwise, the word under the cursor is replaced by the item
1956 corresponding to the value of the numeric parameter from the
1957 most recently generated command or file list. If the cursor
1958 is not on a word, it is inserted instead.
1959 ^U Multiply parameter of next command by 4.
1960 \ Escape next character. Editing characters, the user's erase,
1961 kill and interrupt (normally ^?) characters may be entered
1962 in a command line or in a search string if preceded by a \.
1963 The \ removes the next character's editing features (if any).
1964 M-^V Display version of the shell.
1965 M-# If the line does not begin with a #, a # is inserted at the
1966 beginning of the line and after each new-line, and the line
1967 is entered. This causes a comment to be inserted in the his‐
1968 tory file. If the line begins with a #, the # is deleted and
1969 one # after each new-line is also deleted.
1970 Vi Editing Mode.
1972 There are two typing modes. Initially, when you enter a command you
1973 are in the input mode. To edit, the user enters control mode by typing
1974 ESC (033) and moves the cursor to the point needing correction and then
1975 inserts or deletes characters or words as needed. Most control com‐
1976 mands accept an optional repeat count prior to the command.
1977 When in vi mode on most systems, canonical processing is initially
1979 enabled and the command will be echoed again if the speed is 1200 baud
1980 or greater and it contains any control characters or less than one sec‐
1981 ond has elapsed since the prompt was printed. The ESC character termi‐
1982 nates canonical processing for the remainder of the command and the
1983 user can then modify the command line. This scheme has the advantages
1984 of canonical processing with the type-ahead echoing of raw mode.
1985 If the option viraw is also set, the terminal will always have canoni‐
1987 cal processing disabled. This mode is implicit for systems that do not
1988 support two alternate end of line delimiters, and may be helpful for
1989 certain terminals.
1990 Input Edit Commands
1992 By default the editor is in input mode.
1993 erase (User defined erase character as defined by the stty
1994 command, usually ^H or #.) Delete previous character.
1995 ^W Delete the previous blank separated word. On some
1996 systems the viraw option may be required for this to
1997 work.
1998 eof As the first character of the line causes the shell to
1999 terminate unless the ignoreeof option is set. Other‐
2000 wise this character is ignored.
2001 lnext (User defined literal next character as defined by the
2002 stty(1) or ^V if not defined.) Removes the next char‐
2003 acter's editing features (if any). On some systems
2004 the viraw option may be required for this to work.
2005 \ Escape the next erase or kill character.
2006 ^I tab Attempts command or file name completion as described
2007 above and returns to input mode. If a partial comple‐
2008 tion occurs, repeating this will behave as if = were
2009 entered from control mode. If no match is found or
2010 entered after space, a tab is inserted.
2011 Motion Edit Commands
2012 These commands will move the cursor.
2013 [count]l Cursor forward (right) one character.
2014 [count][C Cursor forward (right) one character.
2015 [count]w Cursor forward one alpha-numeric word.
2016 [count]W Cursor to the beginning of the next word that follows
2017 a blank.
2018 [count]e Cursor to end of word.
2019 [count]E Cursor to end of the current blank delimited word.
2020 [count]h Cursor backward (left) one character.
2021 [count][D Cursor backward (left) one character.
2022 [count]b Cursor backward one word.
2023 [count]B Cursor to preceding blank separated word.
2024 [count]⎪ Cursor to column count.
2025 [count]fc Find the next character c in the current line.
2026 [count]Fc Find the previous character c in the current line.
2027 [count]tc Equivalent to f followed by h.
2028 [count]Tc Equivalent to F followed by l.
2029 [count]; Repeats count times, the last single character find
2030 command, f, F, t, or T.
2031 [count], Reverses the last single character find command count
2032 times.
2033 0 Cursor to start of line.
2034 ^ Cursor to start of line.
2035 [H Cursor to first non-blank character in line.
2036 $ Cursor to end of line.
2037 [Y Cursor to end of line.
2038 % Moves to balancing (, ), {, }, [, or ]. If cursor is
2039 not on one of the above characters, the remainder of
2040 the line is searched for the first occurrence of one
2041 of the above characters first.
2042 Search Edit Commands
2043 These commands access your command history.
2044 [count]k Fetch previous command. Each time k is entered the
2045 previous command back in time is accessed.
2046 [count]- Equivalent to k.
2047 [count][A If cursor is at the end of the line it is equivalent
2048 to / with string^set to the contents of the current
2049 line. Otherwise, it is equivalent to k.
2050 [count]j Fetch next command. Each time j is entered the next
2051 command forward in time is accessed.
2052 [count]+ Equivalent to j.
2053 [count][B Equivalent to j.
2054 [count]G The command number count is fetched. The default is
2055 the least recent history command.
2056 /string Search backward through history for a previous command
2057 containing string. String is terminated by a `RETURN'
2058 or `NEW LINE'. If string is preceded by a ^, the
2059 matched line must begin with string. If string is
2060 null, the previous string will be used.
2061 ?string Same as / except that search will be in the forward
2062 direction.
2063 n Search for next match of the last pattern to / or ?
2064 commands.
2065 N Search for next match of the last pattern to / or ?,
2066 but in reverse direction.
2067 Text Modification Edit Commands
2068 These commands will modify the line.
2069 a Enter input mode and enter text after the current
2070 character.
2071 A Append text to the end of the line. Equivalent to $a.
2072 [count]cmotion
2073 c[count]motion
2074 Delete current character through the character that
2075 motion would move the cursor to and enter input mode.
2076 If motion is c, the entire line will be deleted and
2077 input mode entered.
2078 C Delete the current character through the end of line
2079 and enter input mode. Equivalent to c$.
2080 S Equivalent to cc.
2081 [count]s Replace characters under the cursor in input mode.
2082 D Delete the current character through the end of line.
2083 Equivalent to d$.
2084 [count]dmotion
2085 d[count]motion
2086 Delete current character through the character that
2087 motion would move to. If motion is d , the entire
2088 line will be deleted.
2089 i Enter input mode and insert text before the current
2090 character.
2091 I Insert text before the beginning of the line. Equiva‐
2092 lent to 0i.
2093 [count]P Place the previous text modification before the cur‐
2094 sor.
2095 [count]p Place the previous text modification after the cursor.
2096 R Enter input mode and replace characters on the screen
2097 with characters you type overlay fashion.
2098 [count]rc Replace the count character(s) starting at the current
2099 cursor position with c, and advance the cursor.
2100 [count]x Delete current character.
2101 [count]X Delete preceding character.
2102 [count]. Repeat the previous text modification command.
2103 [count]∼ Invert the case of the count character(s) starting at
2104 the current cursor position and advance the cursor.
2105 [count]_ Causes the count word of the previous command to be
2106 appended and input mode entered. The last word is
2107 used if count is omitted.
2108 * Causes an * to be appended to the current word and
2109 file name generation attempted. If no match is found,
2110 it rings the bell. Otherwise, the word is replaced by
2111 the matching pattern and input mode is entered.
2112 \ Command or file name completion as described above.
2113 Other Edit Commands
2114 Miscellaneous commands.
2115 [count]ymotion
2116 y[count]motion
2117 Yank current character through character that motion
2118 would move the cursor to and puts them into the delete
2119 buffer. The text and cursor are unchanged.
2120 yy Yanks the entire line.
2121 Y Yanks from current position to end of line. Equiva‐
2122 lent to y$.
2123 u Undo the last text modifying command.
2124 U Undo all the text modifying commands performed on the
2125 line.
2126 [count]v Returns the command hist -e ${VISUAL:-${EDITOR:-vi}}
2127 count in the input buffer. If count is omitted, then
2128 the current line is used.
2129 ^L Line feed and print current line. Has effect only in
2130 control mode.
2131 ^J (New line) Execute the current line, regardless of
2132 mode.
2133 ^M (Return) Execute the current line, regardless of mode.
2134 # If the first character of the command is a #, then
2135 this command deletes this # and each # that follows a
2136 newline. Otherwise, sends the line after inserting a
2137 # in front of each line in the command. Useful for
2138 causing the current line to be inserted in the history
2139 as a comment and uncommenting previously commented
2140 commands in the history file.
2141 [count]= If count is not specified, it generates the list of
2142 matching commands or file names as described above.
2143 Otherwise, the word under the the cursor is replaced
2144 by the count item from the most recently generated
2145 command or file list. If the cursor is not on a word,
2146 it is inserted instead.
2147 @letter Your alias list is searched for an alias by the name
2148 _letter and if an alias of this name is defined, its
2149 value will be inserted on the input queue for process‐
2150 ing.
2151 ^V Display version of the shell.
2152 Built-in Commands.
2154 The following simple-commands are executed in the shell process.
2155 Input/Output redirection is permitted. Unless otherwise indicated, the
2156 output is written on file descriptor 1 and the exit status, when there
2157 is no syntax error, is zero. Except for :, true, false, echo, newgrp,
2158 and login, all built-in commands accept -- to indicate end of options.
2159 They also interpret the option --man as a request to display the man
2160 page onto standard error and -? as a help request which prints a usage
2161 message on standard error. Commands that are preceded by one or two †
2162 symbols are special built-in commands and are treated specially in the
2163 following ways:
2164 1. Variable assignment lists preceding the command remain in effect
2165 when the command completes.
2166 2. I/O redirections are processed after variable assignments.
2167 3. Errors cause a script that contains them to abort.
2168 4. They are not valid function names.
2169 5. Words following a command preceded by †† that are in the format
2170 of a variable assignment are expanded with the same rules as a
2171 variable assignment. This means that tilde substitution is per‐
2172 formed after the = sign and field splitting and file name gener‐
2173 ation are not performed. These are called declaration built-
2174 ins.
2175 † : [ arg ... ]
2177 The command only expands parameters.
2178 † . name [ arg ... ]
2180 If name is a function defined with the function name reserved
2181 word syntax, the function is executed in the current environment
2182 (as if it had been defined with the name() syntax.) Otherwise
2183 if name refers to a file, the file is read in its entirety and
2184 the commands are executed in the current shell environment. The
2185 search path specified by PATH is used to find the directory con‐
2186 taining the file. If any arguments arg are given, they become
2187 the positional parameters while processing the . command and
2188 the original positional parameters are restored upon completion.
2189 Otherwise the positional parameters are unchanged. The exit
2190 status is the exit status of the last command executed.
2191 †† alias [ -ptx ] [ name[ =value ] ] ...
2193 alias with no arguments prints the list of aliases in the form
2194 name=value on standard output. The -p option causes the word
2195 alias to be inserted before each one. When one or more argu‐
2196 ments are given, an alias is defined for each name whose value
2197 is given. A trailing space in value causes the next word to be
2198 checked for alias substitution. The obsolete -t option is used
2199 to set and list tracked aliases. The value of a tracked alias
2200 is the full pathname corresponding to the given name. The value
2201 becomes undefined when the value of PATH is reset but the alias
2202 remains tracked. Without the -t option, for each name in the
2203 argument list for which no value is given, the name and value of
2204 the alias is printed. The obsolete -x option has no effect.
2205 The exit status is non-zero if a name is given, but no value,
2206 and no alias has been defined for the name.
2207 bg [ job... ]
2209 This command is only on systems that support job control. Puts
2210 each specified job into the background. The current job is put
2211 in the background if job is not specified. See Jobs for a
2212 description of the format of job.
2213 † break [ n ]
2215 Exit from the enclosing for, while, until, or select loop, if
2216 any. If n is specified, then break n levels.
2217 builtin [ -ds ] [ -f file ] [ name ... ]
2219 If name is not specified, and no -f option is specified, the
2220 built-ins are printed on standard output. The -s option prints
2221 only the special built-ins. Otherwise, each name represents the
2222 pathname whose basename is the name of the built-in. The entry
2223 point function name is determined by prepending b_ to the built-
2224 in name. A built-in specified by a pathname will only be exe‐
2225 cuted when that pathname would be found during the path search.
2226 Built-ins found in libraries loaded via the .paths file will be
2227 associate with the pathname of the directory containing the
2228 .paths file.
2229 The ISO C/C++ prototype is b_mycommand(int argc, char *argv[], void
2231 *context) for the builtin command mycommand where argv is array an of
2232 argc elements and context is an optional pointer to a Shell_t structure
2233 as described in <ast/shell.h>.
2234 Special built-ins cannot be bound to a pathname or deleted. The -d
2235 option deletes each of the given built-ins. On systems that support
2236 dynamic loading, the -f option names a shared library containing the
2237 code for built-ins. The shared library prefix and/or suffix, which
2238 depend on the system, can be omitted. Once a library is loaded, its
2239 symbols become available for subsequent invocations of builtin. Multi‐
2240 ple libraries can be specified with separate invocations of the builtin
2241 command. Libraries are searched in the reverse order in which they are
2242 specified. When a library is loaded, it looks for a function in the
2243 library whose name is lib_init() and invokes this function with an
2244 argument of 0.
2245 cd [ -LP ] [ arg ]
2247 cd [ -LP ] old new
2248 This command can be in either of two forms. In the first form
2249 it changes the current directory to arg. If arg is - the direc‐
2250 tory is changed to the previous directory. The shell variable
2251 HOME is the default arg. The variable PWD is set to the current
2252 directory. The shell variable CDPATH defines the search path
2253 for the directory containing arg. Alternative directory names
2254 are separated by a colon (:). The default path is <null> (spec‐
2255 ifying the current directory). Note that the current directory
2256 is specified by a null path name, which can appear immediately
2257 after the equal sign or between the colon delimiters anywhere
2258 else in the path list. If arg begins with a / then the search
2259 path is not used. Otherwise, each directory in the path is
2260 searched for arg.
2261 The second form of cd substitutes the string new for the string
2262 old in the current directory name, PWD, and tries to change to
2263 this new directory.
2264 By default, symbolic link names are treated literally when find‐
2265 ing the directory name. This is equivalent to the -L option.
2266 The -P option causes symbolic links to be resolved when deter‐
2267 mining the directory. The last instance of -L or -P on the com‐
2268 mand line determines which method is used.
2269 The cd command may not be executed by rksh. rksh93.
2270 command [ -pvxV ] name [ arg ... ]
2272 Without the -v or -V options, command executes name with the
2273 arguments given by arg. The -p option causes a default path to
2274 be searched rather than the one defined by the value of PATH.
2275 Functions will not be searched for when finding name. In addi‐
2276 tion, if name refers to a special built-in, none of the special
2277 properties associated with the leading daggers will be honored.
2278 (For example, the predefined alias redirect=′command exec′ pre‐
2279 vents a script from terminating when an invalid redirection is
2280 given.) With the -x option, if command execution would result
2281 in a failure because there are too many arguments, errno E2BIG,
2282 the shell will invoke command name multiple times with a subset
2283 of the arguments on each invocation. Arguments that occur prior
2284 to the first word that expands to multiple arguments and after
2285 the last word that expands to multiple arguments will be passed
2286 on each invocation. The exit status will be the maximum invoca‐
2287 tion exit status. With the -v option, command is equivalent to
2288 the built-in whence command described below. The -V option
2289 causes command to act like whence -v.
2290 † continue [ n ]
2292 Resume the next iteration of the enclosing for, while, until, or
2293 select loop. If n is specified, then resume at the n-th enclos‐
2294 ing loop.
2295 disown [ job... ]
2297 Causes the shell not to send a HUP signal to each given job, or
2298 all active jobs if job is omitted, when a login shell termi‐
2299 nates.
2300 echo [ arg ... ]
2302 When the first arg does not begin with a -, and none of the
2303 arguments contain a \, then echo prints each of its arguments
2304 separated by a space and terminated by a new-line. Otherwise,
2305 the behavior of echo is system dependent and print or printf
2306 described below should be used. See echo(1) for usage and
2307 description.
2308 †† enum [ -i ] type[=(value ...) ]
2310 Creates a declaration command named type that is an integer type
2311 that allows one of the specified values as enumeration names.
2312 If =(value ...) is omitted, then type must be an indexed array
2313 variable with at least two elements and the values are taken
2314 from this array variable. If -i is specified the values are
2315 case insensitive.
2316 † eval [ arg ... ]
2318 The arguments are read as input to the shell and the resulting
2319 command(s) executed.
2320 † exec [ -c ] [ -a name ] [ arg ... ]
2322 If arg is given, the command specified by the arguments is exe‐
2323 cuted in place of this shell without creating a new process.
2324 The -c option causes the environment to be cleared before apply‐
2325 ing variable assignments associated with the exec invocation.
2326 The -a option causes name rather than the first arg, to become
2327 argv[0] for the new process. Input/output arguments may appear
2328 and affect the current process. If arg is not given, the effect
2329 of this command is to modify file descriptors as prescribed by
2330 the input/output redirection list. In this case, any file
2331 descriptor numbers greater than 2 that are opened with this
2332 mechanism are closed when invoking another program.
2333 † exit [ n ]
2335 Causes the shell to exit with the exit status specified by n.
2336 The value will be the least significant 8 bits of the specified
2337 status. If n is omitted, then the exit status is that of the
2338 last command executed. An end-of-file will also cause the shell
2339 to exit except for a shell which has the ignoreeof option (see
2340 set below) turned on.
2341 †† export [ -p ] [ name[=value] ] ...
2343 If name is not given, the names and values of each variable with
2344 the export attribute are printed with the values quoted in a
2345 manner that allows them to be re-input. The export command is
2346 the same as typeset -x except that if you use export within a
2347 function, no local variable is created. The -p option causes
2348 the word export to be inserted before each one. Otherwise, the
2349 given names are marked for automatic export to the environment
2350 of subsequently-executed commands.
2351 false Does nothing, and exits 1. Used with until for infinite loops.
2353 fg [ job... ]
2355 This command is only on systems that support job control. Each
2356 job specified is brought to the foreground and waited for in the
2357 specified order. Otherwise, the current job is brought into the
2358 foreground. See Jobs for a description of the format of job.
2359 getconf [ name [ pathname ] ]
2361 Prints the current value of the configuration parameter given by
2362 name. The configuration parameters are defined by the IEEE
2363 POSIX 1003.1 and IEEE POSIX 1003.2 standards. (See pathconf(2)
2364 and sysconf(2).) The pathname argument is required for parame‐
2365 ters whose value depends on the location in the file system. If
2366 no arguments are given, getconf prints the names and values of
2367 the current configuration parameters. The pathname / is used
2368 for each of the parameters that requires pathname.
2369 getopts [ -a name ] optstring vname [ arg ... ]
2371 Checks arg for legal options. If arg is omitted, the positional
2372 parameters are used. An option argument begins with a + or a -.
2373 An option not beginning with + or - or the argument -- ends the
2374 options. Options beginning with + are only recognized when opt‐
2375 string begins with a +. optstring contains the letters that
2376 getopts recognizes. If a letter is followed by a :, that option
2377 is expected to have an argument. The options can be separated
2378 from the argument by blanks. The option -? causes getopts to
2379 generate a usage message on standard error. The -a argument can
2380 be used to specify the name to use for the usage message, which
2381 defaults to $0.
2382 getopts places the next option letter it finds inside variable
2383 vname each time it is invoked. The option letter will be
2384 prepended with a + when arg begins with a +. The index of the
2385 next arg is stored in OPTIND. The option argument, if any, gets
2386 stored in OPTARG.
2387 A leading : in optstring causes getopts to store the letter of
2388 an invalid option in OPTARG, and to set vname to ? for an
2389 unknown option and to : when a required option argument is miss‐
2390 ing. Otherwise, getopts prints an error message. The exit sta‐
2391 tus is non-zero when there are no more options.
2392 There is no way to specify any of the options :, +, -, ?, [, and
2393 ]. The option # can only be specified as the first option.
2394 hist [ -e ename ] [ -nlr ] [ first [ last ] ]
2396 hist -s [ old=new ] [ command ]
2397 In the first form, a range of commands from first to last is
2398 selected from the last HISTSIZE commands that were typed at the
2399 terminal. The arguments first and last may be specified as a
2400 number or as a string. A string is used to locate the most
2401 recent command starting with the given string. A negative num‐
2402 ber is used as an offset to the current command number. If the
2403 -l option is selected, the commands are listed on standard out‐
2404 put. Otherwise, the editor program ename is invoked on a file
2405 containing these keyboard commands. If ename is not supplied,
2406 then the value of the variable HISTEDIT is used. If HISTEDIT is
2407 not set, then FCEDIT (default /bin/ed) is used as the editor.
2408 When editing is complete, the edited command(s) is executed if
2409 the changes have been saved. If last is not specified, then it
2410 will be set to first. If first is not specified, the default is
2411 the previous command for editing and -16 for listing. The
2412 option -r reverses the order of the commands and the option -n
2413 suppresses command numbers when listing. In the second form,
2414 command is interpreted as first described above and defaults to
2415 the last command executed. The resulting command is executed
2416 after the optional substitution old=new is performed.
2417 jobs [ -lnp ] [ job ... ]
2419 Lists information about each given job; or all active jobs if
2420 job is omitted. The -l option lists process ids in addition to
2421 the normal information. The -n option only displays jobs that
2422 have stopped or exited since last notified. The -p option
2423 causes only the process group to be listed. See Jobs for a
2424 description of the format of job.
2425 kill [ -s signame ] job ...
2427 kill [ -n signum ] job ...
2428 kill -Ll [ sig ... ]
2429 Sends either the TERM (terminate) signal or the specified signal
2430 to the specified jobs or processes. Signals are either given by
2431 number with the -n option or by name with the -s option (as
2432 given in <signal.h>, stripped of the prefix ``SIG'' with the
2433 exception that SIGCLD is named CHLD). For backward compatibil‐
2434 ity, the n and s can be omitted and the number or name placed
2435 immediately after the -. If the signal being sent is TERM (ter‐
2436 minate) or HUP (hangup), then the job or process will be sent a
2437 CONT (continue) signal if it is stopped. The argument job can
2438 be the process id of a process that is not a member of one of
2439 the active jobs. See Jobs for a description of the format of
2440 job. In the third form, kill -l, or kill -L, if sig is not
2441 specified, the signal names are listed. The -l option list only
2442 the signal names. -L options lists each signal name and corre‐
2443 sponding number. Otherwise, for each sig that is a name, the
2444 corresponding signal number is listed. For each sig that is a
2445 number, the signal name corresponding to the least significant 8
2446 bits of sig is listed.
2447 let arg ...
2449 Each arg is a separate arithmetic expression to be evaluated.
2450 let only recognizes octal constants starting with 0 when the set
2451 option letoctal is on. See Arithmetic Evaluation above, for a
2452 description of arithmetic expression evaluation.
2453 The exit status is 0 if the value of the last expression is non-
2454 zero, and 1 otherwise.
2455 † newgrp [ arg ... ]
2457 Equivalent to exec /bin/newgrp arg ....
2458 print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
2460 With no options or with option - or --, each arg is printed on
2461 standard output. The -f option causes the arguments to be
2462 printed as described by printf. In this case, any e, n, r, R
2463 options are ignored. Otherwise, unless the -C, -R, -r, or -v
2464 are specified, the following escape conventions will be applied:
2465 \a The alert character (ascii 07).
2466 \b The backspace character (ascii 010).
2467 \c Causes print to end without processing more arguments and
2468 not adding a new-line.
2469 \f The formfeed character (ascii 014).
2470 \n The new-line character (ascii 012).
2471 \r The carriage return character (ascii 015).
2472 \t The tab character (ascii 011).
2473 \v The vertical tab character (ascii 013).
2474 \E The escape character (ascii 033).
2475 \\ The backslash character \.
2476 \0x The character defined by the 1, 2, or 3-digit octal
2477 string given by x.
2478 The -R option will print all subsequent arguments and options
2480 other than -n. The -e causes the above escape conventions to be
2481 applied. This is the default behavior. It reverses the effect
2482 of an earlier -r. The -p option causes the arguments to be
2483 written onto the pipe of the process spawned with ⎪& instead of
2484 standard output. The -v option treats each arg as a variable
2485 name and writes the value in the printf %B format. The -C
2486 option treats each arg as a variable name and writes the value
2487 in the printf %#B format. The -s option causes the arguments to
2488 be written onto the history file instead of standard output.
2489 The -u option can be used to specify a one digit file descriptor
2490 unit number unit on which the output will be placed. The
2491 default is 1. If the option -n is used, no new-line is added to
2492 the output.
2493 printf format [ arg ... ]
2495 The arguments arg are printed on standard output in accordance
2496 with the ANSI-C formatting rules associated with the format
2497 string format. If the number of arguments exceeds the number of
2498 format specifications, the format string is reused to format
2499 remaining arguments. The following extensions can also be used:
2500 %b A %b format can be used instead of %s to cause escape
2501 sequences in the corresponding arg to be expanded as
2502 described in print.
2503 %B A %B option causes each of the arguments to be treated as
2504 variable names and the binary value of variable will be
2505 printed. The alternate flag # causes a compound variable
2506 to be output on a single line. This is most useful for
2507 compound variables and variables whose attribute is -b.
2508 %H A %H format can be used instead of %s to cause characters
2509 in arg that are special in HTML and XML to be output as
2510 their entity name. The alternate flag # formats the out‐
2511 put for use as a URI.
2512 %P A %P format can be used instead of %s to cause arg to be
2513 interpreted as an extended regular expression and be
2514 printed as a shell pattern.
2515 %R A %R format can be used instead of %s to cause arg to be
2516 interpreted as a shell pattern and to be printed as an
2517 extended regular expression.
2518 %q A %q format can be used instead of %s to cause the
2519 resulting string to be quoted in a manner than can be
2520 reinput to the shell. When q is preceded by the alterna‐
2521 tive format specifier, #, the string is quoted in manner
2522 suitable as a field in a .csv format file.
2523 %(date-format)T
2524 A %(date-format)T format can be use to treat an argument
2525 as a date/time string and to format the date/time accord‐
2526 ing to the date-format as defined for the date(1) com‐
2527 mand.
2528 %Z A %Z format will output a byte whose value is 0.
2529 %d The precision field of the %d format can be followed by a
2530 . and the output base. In this case, the # flag charac‐
2531 ter causes base# to be prepended.
2532 # The # flag, when used with the %d format without an out‐
2533 put base, displays the output in powers of 1000 indicated
2534 by one of the following suffixes: k M G T P E, and when
2535 used with the %i format displays the output in powers of
2536 1024 indicated by one of the following suffixes: Ki Mi Gi
2537 Ti Pi Ei.
2538 = The = flag centers the output within the specified field
2539 width.
2540 L The L flag, when used with the %c or %s formats, treats
2541 precision as character width instead of byte count.
2542 , The , flag, when used with the %d or %f formats, sepa‐
2543 rates groups of digits with the grouping delimiter (, on
2544 groups of 3 in the C locale.)
2545 pwd [ -LP ]
2547 Outputs the value of the current working directory. The -L
2548 option is the default; it prints the logical name of the current
2549 directory. If the -P option is given, all symbolic links are
2550 resolved from the name. The last instance of -L or -P on the
2551 command line determines which method is used.
2552 read [ -ACSprsv ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u
2554 unit] [ vname?prompt ] [ vname ... ]
2555 The shell input mechanism. One line is read and is broken up
2556 into fields using the characters in IFS as separators. The
2557 escape character, \, is used to remove any special meaning for
2558 the next character and for line continuation. The -d option
2559 causes the read to continue to the first character of delim
2560 rather than new-line. The -n option causes at most n bytes to
2561 read rather a full line but will return when reading from a slow
2562 device as soon as any characters have been read. The -N option
2563 causes exactly n to be read unless an end-of-file has been
2564 encountered or the read times out because of the -t option. In
2565 raw mode, -r, the \ character is not treated specially. The
2566 first field is assigned to the first vname, the second field to
2567 the second vname, etc., with leftover fields assigned to the
2568 last vname. When vname has the binary attribute and -n or -N is
2569 specified, the bytes that are read are stored directly into the
2570 variable. If the -v is specified, then the value of the first
2571 vname will be used as a default value when reading from a termi‐
2572 nal device. The -A option causes the variable vname to be unset
2573 and each field that is read to be stored in successive elements
2574 of the indexed array vname. The -C option causes the variable
2575 vname to be read as a compound variable. Blanks will be ignored
2576 when finding the beginning open parenthesis. The -S option
2577 causes the line to be treated like a record in a .csv format
2578 file so that double quotes can be used to allow the delimiter
2579 character and the new-line character to appear within a field.
2580 The -p option causes the input line to be taken from the input
2581 pipe of a process spawned by the shell using ⎪&. If the -s
2582 option is present, the input will be saved as a command in the
2583 history file. The option -u can be used to specify a one digit
2584 file descriptor unit unit to read from. The file descriptor can
2585 be opened with the exec special built-in command. The default
2586 value of unit n is 0. The option -t is used to specify a time‐
2587 out in seconds when reading from a terminal or pipe. If vname
2588 is omitted, then REPLY is used as the default vname. An end-of-
2589 file with the -p option causes cleanup for this process so that
2590 another can be spawned. If the first argument contains a ?, the
2591 remainder of this word is used as a prompt on standard error
2592 when the shell is interactive. The exit status is 0 unless an
2593 end-of-file is encountered or read has timed out.
2594 †† readonly [ -p ] [ vname[=value] ] ...
2596 If vname is not given, the names and values of each variable
2597 with the readonly attribute is printed with the values quoted in
2598 a manner that allows them to be re-inputted. The -p option
2599 causes the word readonly to be inserted before each one. Other‐
2600 wise, the given vnames are marked readonly and these names can‐
2601 not be changed by subsequent assignment. When defining a type,
2602 if the value of a readonly sub-variable is not defined the value
2603 is required when creating each instance.
2604 † return [ n ]
2606 Causes a shell function or . script to return to the invoking
2607 script with the exit status specified by n. The value will be
2608 the least significant 8 bits of the specified status. If n is
2609 omitted, then the return status is that of the last command exe‐
2610 cuted. If return is invoked while not in a function or a .
2611 script, then it behaves the same as exit.
2612 † set [ ±BCGabefhkmnoprstuvx ] [ ±o [ option ] ] ... [ ±A vname ] [
2614 arg ... ]
2615 The options for this command have meaning as follows:
2616 -A Array assignment. Unset the variable vname and assign
2617 values sequentially from the arg list. If +A is used,
2618 the variable vname is not unset first.
2619 -B Enable brace pattern field generation. This is the
2620 default behavior.
2621 -B Enable brace group expansion. On by default.
2622 -C Prevents redirection > from truncating existing files.
2623 Files that are created are opened with the O_EXCL mode.
2624 Requires >⎪ to truncate a file when turned on.
2625 -G Causes the pattern ∗∗ by itself to match files and zero
2626 or more directories and sub-directories when used for
2627 file name generation. If followed by a / only directo‐
2628 ries and sub-directories are matched.
2629 -a All subsequent variables that are defined are automati‐
2630 cally exported.
2631 -b Prints job completion messages as soon as a background
2632 job changes state rather than waiting for the next
2633 prompt.
2634 -e Unless contained in a ⎪⎪ or && command, or the command
2635 following an if while or until command or in the pipe‐
2636 line following !, if a command has a non-zero exit sta‐
2637 tus, execute the ERR trap, if set, and exit. This mode
2638 is disabled while reading profiles.
2639 -f Disables file name generation.
2640 -h Each command becomes a tracked alias when first encoun‐
2641 tered.
2642 -k (Obsolete). All variable assignment arguments are placed
2643 in the environment for a command, not just those that
2644 precede the command name.
2645 -m Background jobs will run in a separate process group and
2646 a line will print upon completion. The exit status of
2647 background jobs is reported in a completion message. On
2648 systems with job control, this option is turned on auto‐
2649 matically for interactive shells.
2650 -n Read commands and check them for syntax errors, but do
2651 not execute them. Ignored for interactive shells.
2652 -o The following argument can be one of the following
2653 option names:
2654 allexport
2655 Same as -a.
2656 errexit Same as -e.
2657 bgnice All background jobs are run at a lower priority.
2658 This is the default mode.
2659 braceexpand
2660 Same as -B.
2661 emacs Puts you in an emacs style in-line editor for
2662 command entry.
2663 globstar
2664 Same as -G.
2665 gmacs Puts you in a gmacs style in-line editor for
2666 command entry.
2667 ignoreeof
2668 The shell will not exit on end-of-file. The
2669 command exit must be used.
2670 keyword Same as -k.
2671 letoctal
2672 The let command allows octal constants starting
2673 with 0.
2674 markdirs
2675 All directory names resulting from file name
2676 generation have a trailing / appended.
2677 monitor Same as -m.
2678 multiline
2679 The built-in editors will use multiple lines on
2680 the screen for lines that are longer than the
2681 width of the screen. This may not work for all
2682 terminals.
2683 noclobber
2684 Same as -C.
2685 noexec Same as -n.
2686 noglob Same as -f.
2687 nolog Do not save function definitions in the history
2688 file.
2689 notify Same as -b.
2690 nounset Same as -u.
2691 pipefail
2692 A pipeline will not complete until all compo‐
2693 nents of the pipeline have completed, and the
2694 return value will be the value of the last non-
2695 zero command to fail or zero if no command has
2696 failed.
2697 showme When enabled, simple commands or pipelines pre‐
2698 ceded by a semicolon (;) will be displayed as if
2699 the xtrace option were enabled but will not be
2700 executed. Otherwise, the leading ; will be
2701 ignored.
2702 privileged
2703 Same as -p.
2704 verbose Same as -v.
2705 trackall
2706 Same as -h.
2707 vi Puts you in insert mode of a vi style in-line
2708 editor until you hit the escape character 033.
2709 This puts you in control mode. A return sends
2710 the line.
2711 viraw Each character is processed as it is typed in vi
2712 mode.
2713 xtrace Same as -x.
2714 If no option name is supplied, then the current option
2715 settings are printed.
2716 -p Disables processing of the $HOME/.profile file and uses
2717 the file /etc/suid_profile instead of the ENV file.
2718 This mode is on whenever the effective uid (gid) is not
2719 equal to the real uid (gid). Turning this off causes
2720 the effective uid and gid to be set to the real uid and
2721 gid.
2722 -r Enables the restricted shell. This option cannot be
2723 unset once set.
2724 -s Sort the positional parameters lexicographically.
2725 -t (Obsolete). Exit after reading and executing one com‐
2726 mand.
2727 -u Treat unset parameters as an error when substituting.
2728 -v Print shell input lines as they are read.
2729 -x Print commands and their arguments as they are executed.
2730 -- Do not change any of the options; useful in setting $1
2731 to a value beginning with -. If no arguments follow
2732 this option then the positional parameters are unset.
2733 As an obsolete feature, if the first arg is - then the -x and -v
2735 options are turned off and the next arg is treated as the first
2736 argument. Using + rather than - causes these options to be
2737 turned off. These options can also be used upon invocation of
2738 the shell. The current set of options may be found in $-.
2739 Unless -A is specified, the remaining arguments are positional
2740 parameters and are assigned, in order, to $1 $2 .... If no
2741 arguments are given, then the names and values of all variables
2742 are printed on the standard output.
2743 † shift [ n ]
2745 The positional parameters from $n+1 ... are renamed $1 ... ,
2746 default n is 1. The parameter n can be any arithmetic expres‐
2747 sion that evaluates to a non-negative number less than or equal
2748 to $#.
2749 sleep seconds
2751 Suspends execution for the number of decimal seconds or frac‐
2752 tions of a second given by seconds.
2753 † trap [ -p ] [ action ] [ sig ] ...
2755 The -p option causes the trap action associated with each trap
2756 as specified by the arguments to be printed with appropriate
2757 quoting. Otherwise, action will be processed as if it were an
2758 argument to eval when the shell receives signal(s) sig. Each
2759 sig can be given as a number or as the name of the signal. Trap
2760 commands are executed in order of signal number. Any attempt to
2761 set a trap on a signal that was ignored on entry to the current
2762 shell is ineffective. If action is omitted and the first sig is
2763 a number, or if action is -, then the trap(s) for each sig are
2764 reset to their original values. If action is the null string
2765 then this signal is ignored by the shell and by the commands it
2766 invokes. If sig is ERR then action will be executed whenever a
2767 command has a non-zero exit status. If sig is DEBUG then action
2768 will be executed before each command. The variable .sh.command
2769 will contain the contents of the current command line when
2770 action is running. If the exit status of the trap is 2 the com‐
2771 mand will not be executed. If the exit status of the trap is
2772 255 and inside a function or a dot script, the function or dot
2773 script will return. If sig is 0 or EXIT and the trap statement
2774 is executed inside the body of a function defined with the func‐
2775 tion name syntax, then the command action is executed after the
2776 function completes. If sig is 0 or EXIT for a trap set outside
2777 any function then the command action is executed on exit from
2778 the shell. If sig is KEYBD, then action will be executed when‐
2779 ever a key is read while in emacs, gmacs, or vi mode. The trap
2780 command with no arguments prints a list of commands associated
2781 with each signal number.
2782 An exit or return without an argument in a trap action will preserve
2784 the exit status of the command that invoked the trap.
2785 true Does nothing, and exits 0. Used with while for infinite loops.
2787 †† typeset [ ±ACHSfblmnprtux ] [ ±EFLRXZi[n] ] [ +-M [ mapname ] ] [
2789 -T [ tname=(assign_list) ] ] [ -h str ] [ -a [type] ] [ vname[=value ]
2790 ] ...
2791 Sets attributes and values for shell variables and functions.
2792 When invoked inside a function defined with the function name
2793 syntax, a new instance of the variable vname is created, and the
2794 variable's value and type are restored when the function com‐
2795 pletes. The following list of attributes may be specified:
2796 -A Declares vname to be an associative array. Subscripts
2797 are strings rather than arithmetic expressions.
2798 -C causes each vname to be a compound variable. value names
2799 a compound variable it is copied into vname. Otherwise,
2800 it unsets each vname.
2801 -a Declares vname to be an indexed array. If type is speci‐
2802 fied, it must be the name of an enumeration type created
2803 with the enum command and it allows enumeration constants
2804 to be used as subscripts.
2805 -E Declares vname to be a double precision floating point
2806 number. If n is non-zero, it defines the number of sig‐
2807 nificant figures that are used when expanding vname.
2808 Otherwise, ten significant figures will be used.
2809 -F Declares vname to be a double precision floating point
2810 number. If n is non-zero, it defines the number of
2811 places after the decimal point that are used when expand‐
2812 ing vname. Otherwise ten places after the decimal point
2813 will be used.
2814 -H This option provides UNIX to host-name file mapping on
2815 non-UNIX machines.
2816 -L Left justify and remove leading blanks from value. If n
2817 is non-zero, it defines the width of the field, otherwise
2818 it is determined by the width of the value of first
2819 assignment. When the variable is assigned to, it is
2820 filled on the right with blanks or truncated, if neces‐
2821 sary, to fit into the field. The -R option is turned
2822 off.
2823 -M Use the character mapping mapping defined by wctrans(3).
2824 such as tolower and toupper when assigning a value to
2825 each of the specified operands. When mapping is speci‐
2826 fied and there are not operands, all variables that use
2827 this mapping are written to standard output. When map‐
2828 ping is omitted and there are no operands, all mapped
2829 variables are written to standard output.
2830 -R Right justify and fill with leading blanks. If n is non-
2831 zero, it defines the width of the field, otherwise it is
2832 determined by the width of the value of first assignment.
2833 The field is left filled with blanks or truncated from
2834 the end if the variable is reassigned. The -L option is
2835 turned off.
2836 -S When used within the assign_list of a type definition, it
2837 causes the specified sub-variable to be shared by all
2838 instances of the type. When used inside a function
2839 defined with the function reserved word, the specified
2840 variables will have function static scope. Otherwise,
2841 the variable is unset prior to processing the assignment
2842 list.
2843 -T If followed by tname, it creates a type named by tname
2844 using the compound assignment assign_list to tname. Oth‐
2845 erwise, it writes all the type definitions to standard
2846 output.
2847 -X Declares vname to be a double precision floating point
2848 number and expands using the %a format of ISO-C99. If n
2849 is non-zero, it defines the number of hex digits after
2850 the radix point that is used when expanding vname. The
2851 default is 10.
2852 -Z Right justify and fill with leading zeros if the first
2853 non-blank character is a digit and the -L option has not
2854 been set. Remove leading zeros if the -L option is also
2855 set. If n is non-zero, it defines the width of the
2856 field, otherwise it is determined by the width of the
2857 value of first assignment.
2858 -f The names refer to function names rather than variable
2859 names. No assignments can be made and the only other
2860 valid options are -S, -t, -u and -x. The -S can be used
2861 with discipline functions defined in a type to indicate
2862 that the function is static. For a static function, the
2863 same method will be used by all instances of that type no
2864 matter which instance references it. In addition, it can
2865 only use value of variables from the original type defi‐
2866 nition. These discipline functions cannot be redefined
2867 in any type instance. The -t option turns on execution
2868 tracing for this function. The -u option causes this
2869 function to be marked undefined. The FPATH variable will
2870 be searched to find the function definition when the
2871 function is referenced. If no options other than -f is
2872 specified, then the function definition will be displayed
2873 on standard output. If +f is specified, then a line con‐
2874 taining the function name followed by a shell comment
2875 containing the line number and path name of the file
2876 where this function was defined, if any, is displayed.
2877 The exit status can be used to determine whether the
2878 function is defined so that typeset -f .sh.math.name will
2879 return 0 when math function name is defined and non-zero
2880 otherwise.
2881 -b The variable can hold any number of bytes of data. The
2882 data can be text or binary. The value is represented by
2883 the base64 encoding of the data. If -Z is also speci‐
2884 fied, the size in bytes of the data in the buffer will be
2885 determined by the size associated with the -Z. If the
2886 base64 string assigned results in more data, it will be
2887 truncated. Otherwise, it will be filled with bytes whose
2888 value is zero. The printf format %B can be used to out‐
2889 put the actual data in this buffer instead of the base64
2890 encoding of the data.
2891 -h Used within type definitions to add information when gen‐
2892 erating information about the sub-variable on the man
2893 page. It is ignored when used outside of a type defini‐
2894 tion. When used with -f the information is associated
2895 with the corresponding discipline function.
2896 -i Declares vname to be represented internally as integer.
2897 The right hand side of an assignment is evaluated as an
2898 arithmetic expression when assigning to an integer. If n
2899 is non-zero, it defines the output arithmetic base, oth‐
2900 erwise the output base will be ten.
2901 -l Used with -i, -E or -F, to indicate long integer, or long
2902 float. Otherwise, all upper-case characters are con‐
2903 verted to lower-case. The upper-case option, -u, is
2904 turned off. Equivalent to -M tolower .
2905 -m moves or renames the variable. The value is the name of
2906 a variable whose value will be moved to vname. The orig‐
2907 inal variable will be unset. Cannot be used with any
2908 other options.
2909 -n Declares vname to be a reference to the variable whose
2910 name is defined by the value of variable vname. This is
2911 usually used to reference a variable inside a function
2912 whose name has been passed as an argument. Cannot be
2913 used with any other options.
2914 -p The name, attributes and values for the given vnames are
2915 written on standard output in a form that can be used as
2916 shell input. If +p is specified, then the values are not
2917 displayed.
2918 -r The given vnames are marked readonly and these names can‐
2919 not be changed by subsequent assignment.
2920 -t Tags the variables. Tags are user definable and have no
2921 special meaning to the shell.
2922 -u When given along with -i, specifies unsigned integer.
2923 Otherwise, all lower-case characters are converted to
2924 upper-case. The lower-case option, -l, is turned off.
2925 Equivalent to -M toupper .
2926 -x The given vnames are marked for automatic export to the
2927 environment of subsequently-executed commands. Variables
2928 whose names contain a . cannot be exported.
2929 The -i attribute cannot be specified along with -R, -L, -Z, or
2931 -f.
2932 Using + rather than - causes these options to be turned off. If
2934 no vname arguments are given, a list of vnames (and optionally
2935 the values) of the variables is printed. (Using + rather than -
2936 keeps the values from being printed.) The -p option causes
2937 typeset followed by the option letters to be printed before each
2938 name rather than the names of the options. If any option other
2939 than -p is given, only those variables which have all of the
2940 given options are printed. Otherwise, the vnames and attributes
2941 of all variables that have attributes are printed.
2942 ulimit [ -HSacdfmnpstv ] [ limit ]
2944 Set or display a resource limit. The available resource limits
2945 are listed below. Many systems do not support one or more of
2946 these limits. The limit for a specified resource is set when
2947 limit is specified. The value of limit can be a number in the
2948 unit specified below with each resource, or the value unlimited.
2949 The -H and -S options specify whether the hard limit or the soft
2950 limit for the given resource is set. A hard limit cannot be
2951 increased once it is set. A soft limit can be increased up to
2952 the value of the hard limit. If neither the H nor S option is
2953 specified, the limit applies to both. The current resource
2954 limit is printed when limit is omitted. In this case, the soft
2955 limit is printed unless H is specified. When more than one
2956 resource is specified, then the limit name and unit is printed
2957 before the value.
2958 -a Lists all of the current resource limits.
2959 -c The number of 512-byte blocks on the size of core dumps.
2960 -d The number of K-bytes on the size of the data area.
2961 -f The number of 512-byte blocks on files that can be writ‐
2962 ten by the current process or by child processes (files
2963 of any size may be read).
2964 -m The number of K-bytes on the size of physical memory.
2965 -n The number of file descriptors plus 1.
2966 -p The number of 512-byte blocks for pipe buffering.
2967 -s The number of K-bytes on the size of the stack area.
2968 -t The number of CPU seconds to be used by each process.
2969 -v The number of K-bytes for virtual memory.
2970 If no option is given, -f is assumed.
2972 umask [ -S ] [ mask ]
2974 The user file-creation mask is set to mask (see umask(2)). mask
2975 can either be an octal number or a symbolic value as described
2976 in chmod(1). If a symbolic value is given, the new umask value
2977 is the complement of the result of applying mask to the comple‐
2978 ment of the previous umask value. If mask is omitted, the cur‐
2979 rent value of the mask is printed. The -S option causes the
2980 mode to be printed as a symbolic value. Otherwise, the mask is
2981 printed in octal.
2982 † unalias [ -a ] name ...
2984 The aliases given by the list of names are removed from the
2985 alias list. The -a option causes all the aliases to be unset.
2986 †unset [ -fnv ] vname ...
2988 The variables given by the list of vnames are unassigned, i.e.,
2989 except for sub-variables within a type, their values and
2990 attributes are erased. For sub-variables of a type, the values
2991 are reset to the default value from the type definition. Read‐
2992 only variables cannot be unset. If the -f option is set, then
2993 the names refer to function names. If the -v option is set,
2994 then the names refer to variable names. The -f option overrides
2995 -v. If -n is set and name is a name reference, then name will
2996 be unset rather than the variable that it references. The
2997 default is equivalent to -v. Unsetting LINENO, MAILCHECK,
2998 OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their spe‐
2999 cial meaning even if they are subsequently assigned to.
3000 wait [ job ... ]
3002 Wait for the specified job and report its termination status.
3003 If job is not given, then all currently active child processes
3004 are waited for. The exit status from this command is that of
3005 the last process waited for if job is specified; otherwise it is
3006 zero. See Jobs for a description of the format of job.
3007 whence [ -afpv ] name ...
3009 For each name, indicate how it would be interpreted if used as a
3010 command name.
3011 The -v option produces a more verbose report. The -f option
3012 skips the search for functions. The -p option does a path
3013 search for name even if name is an alias, a function, or a
3014 reserved word. The -p option turns off the -v option. The -a
3015 option is similar to the -v option but causes all interpreta‐
3016 tions of the given name to be reported.
3017 Invocation.
3019 If the shell is invoked by exec(2), and the first character of argument
3020 zero ($0) is -, then the shell is assumed to be a login shell and com‐
3021 mands are read from /etc/profile and then from either .profile in the
3022 current directory or $HOME/.profile, if either file exists. Next, for
3023 interactive shells, commands are read from the file named by performing
3024 parameter expansion, command substitution, and arithmetic substitution
3025 on the value of the environment variable ENV if the file exists. If
3026 the -s option is not present and arg and a file by the name of arg
3027 exists, then it reads and executes this script. Otherwise, if the
3028 first arg does not contain a /, a path search is performed on the first
3029 arg to determine the name of the script to execute. The script arg
3030 must have execute permission and any setuid and setgid settings will be
3031 ignored. If the script is not found on the path, arg is processed as
3032 if it named a built-in command or function. Commands are then read as
3033 described below; the following options are interpreted by the shell
3034 when it is invoked:
3035 -D Do not execute the script, but output the set of double quoted
3037 strings preceded by a $. These strings are needed for local‐
3038 ization of the script to different locales.
3039 -E Reads the file named by the ENV variable or by $HOME/.kshrc if
3040 not defined after the profiles.
3041 -c If the -c option is present, then commands are read from the
3042 first arg. Any remaining arguments become positional parame‐
3043 ters starting at 0.
3044 -s If the -s option is present or if no arguments remain, then
3045 commands are read from the standard input. Shell output,
3046 except for the output of the Special Commands listed above,
3047 is written to file descriptor 2.
3048 -i If the -i option is present or if the shell input and error
3049 output are attached to a terminal (as told by tcgetattr(2)),
3050 then this shell is interactive. In this case TERM is ignored
3051 (so that kill 0 does not kill an interactive shell) and INTR
3052 is caught and ignored (so that wait is ). In all cases, QUIT
3053 is ignored by the shell.
3054 -r If the -r option is present, the shell is a restricted shell.
3055 -D A list of all double quoted strings that are preceded by a $
3056 will be printed on standard output and the shell will exit.
3057 This set of strings will be subject to language translation
3058 when the locale is not C or POSIX. No commands will be exe‐
3059 cuted.
3060 -P If -P or -o profile is present, the shell is a profile shell
3062 (see pfexec(1)).
3063 -R filename
3065 The -R filename option is used to generate a cross reference
3066 database that can be used by a separate utility to find defi‐
3067 nitions and references for variables and commands. The file‐
3068 name argument specifies the generated database. A script file
3069 must be provided on the command line as well.
3070 The remaining options and arguments are described under the set command
3072 above. An optional - as the first argument is ignored.
3073 Rksh Only.
3075 Rksh is used to set up login names and execution environments whose
3076 capabilities are more controlled than those of the standard shell. The
3077 actions of rksh are identical to those of ksh, except that the follow‐
3078 ing are disallowed:
3079 Unsetting the restricted option.
3080 changing directory (see cd(1)),
3081 setting or unsetting the value or attributes of SHELL, ENV,
3082 FPATH, or PATH,
3083 specifying path or command names containing /,
3084 redirecting output (>, >|, <>, and >>).
3085 adding or deleting built-in commands.
3086 using command -p to invoke a command.
3087 The restrictions above are enforced after .profile and the ENV files
3089 are interpreted.
3090 When a command to be executed is found to be a shell procedure, rksh
3092 invokes ksh to execute it. Thus, it is possible to provide to the end-
3093 user shell procedures that have access to the full power of the stan‐
3094 dard shell, while imposing a limited menu of commands; this scheme
3095 assumes that the end-user does not have write and execute permissions
3096 in the same directory.
3097 The net effect of these rules is that the writer of the .profile has
3099 complete control over user actions, by performing guaranteed setup
3100 actions and leaving the user in an appropriate directory (probably not
3101 the login directory).
3102 The system administrator often sets up a directory of commands (e.g.,
3104 /usr/rbin) that can be safely invoked by rksh.
3105
3107 Errors detected by the shell, such as syntax errors, cause the shell to
3108 return a non-zero exit status. If the shell is being used non-interac‐
3109 tively, then execution of the shell file is abandoned unless the error
3110 occurs inside a subshell in which case the subshell is abandoned. Oth‐
3111 erwise, the shell returns the exit status of the last command executed
3112 (see also the exit command above). Run time errors detected by the
3113 shell are reported by printing the command or function name and the
3114 error condition. If the line number that the error occurred on is
3115 greater than one, then the line number is also printed in square brack‐
3116 ets ([]) after the command or function name.
3117
3119 /etc/profile
3120 The system wide initialization file, executed for login shells.
3121 $HOME/.profile
3123 The personal initialization file, executed for login shells
3124 after /etc/profile.
3125 $HOME/..kshrc
3127 Default personal initialization file, executed for interactive
3128 shells when ENV is not set.
3129 /etc/suid_profile
3131 Alternative initialization file, executed instead of the per‐
3132 sonal initialization file when the real and effective user or
3133 group id do not match.
3134 /dev/null
3136 NULL device
3137
3139 cat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1),
3140 fgrep(1), gmacs(1), grep(1), newgrp(1), pfexec(1), stty(1), test(1),
3141 umask(1), vi(1), dup(2), exec(2), fork(2), getpwnam(3), ioctl(2),
3142 lseek(2), paste(1), pathconf(2), pipe(2), sysconf(2), umask(2),
3143 ulimit(2), wait(2), wctrans(3), rand(3), a.out(5), profile(5), envi‐
3144 ron(7).
3145 Morris I. Bolsky and David G. Korn, The New KornShell Command and Pro‐
3147 gramming Language, Prentice Hall, 1995.
3148 POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC
3150 9945-2, IEEE, 1993.
3151
3153 If a command is executed, and then a command with the same name is
3154 installed in a directory in the search path before the directory where
3155 the original command was found, the shell will continue to exec the
3156 original command. Use the -t option of the alias command to correct
3157 this situation.
3158 Some very old shell scripts contain a ^ as a synonym for the pipe char‐
3160 acter ⎪.
3161 Using the hist built-in command within a compound command will cause
3163 the whole command to disappear from the history file.
3164 The built-in command . file reads the whole file before any commands
3166 are executed. Therefore, alias and unalias commands in the file will
3167 not apply to any commands defined in the file.
3168 Traps are not processed while a job is waiting for a foreground
3170 process. Thus, a trap on CHLD won't be executed until the foreground
3171 job terminates.
3172 It is a good idea to leave a space after the comma operator in arith‐
3174 metic expressions to prevent the comma from being interpreted as the
3175 decimal point character in certain locales.
3176 KSH(1)