1KSH(1) General Commands Manual KSH(1)
2
6 ksh, rksh - KornShell, a standard/restricted command and programming
7 language
8
10 ksh [ ±abcefhiklmnprstuvxBCDEGH ] [ ±o option ] ... [ - ] [ arg ... ]
11 rksh [ ±abcefhiklmnpstuvxBCDEGH ] [ ±o option ] ... [ - ] [ 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. See Invocation below for the meaning of arguments to the
19 shell.
20 Definitions.
22 A metacharacter is one of the following characters:
23 ; & ( ) | < > new-line space tab
25 A blank is a tab or a space. An identifier is a sequence of letters,
27 digits, or underscores starting with a letter or underscore. Identi‐
28 fiers are used as components of variable names. A vname is a sequence
29 of one or more identifiers separated by a . and optionally preceded by
30 a .. Vnames are used as function and variable names. A word is a se‐
31 quence of characters from the character set defined by the current lo‐
32 cale, excluding non-quoted metacharacters.
33 A command is a sequence of characters in the syntax of the shell lan‐
35 guage. The shell reads each command and carries out the desired action
36 either directly or by invoking separate utilities. A built-in command
37 is a command that is carried out by the shell itself without creating a
38 separate process. Some commands are built in purely for convenience
39 and are not documented here. Built-ins that cause side effects in the
40 shell environment and built-ins that are found before performing a path
41 search (see Execution below) are documented here. For historical rea‐
42 sons, some of these built-ins behave differently than other built-ins
43 and are called special built-ins.
44 Commands.
46 A simple-command is a list of variable assignments (see Variable As‐
47 signments below) or a sequence of blank separated words which may be
48 preceded by a list of variable assignments (see Environment below).
49 The first word specifies the name of the command to be executed. Ex‐
50 cept as specified below, the remaining words are passed as arguments to
51 the invoked command. The command name is passed as argument 0 (see
52 exec(2)). The value of a simple-command is its exit status; 0-255 if
53 it terminates normally; 256+signum if it terminates abnormally (the
54 name of the signal corresponding to the exit status can be obtained via
55 the -l option of the kill built-in utility).
56 A pipeline is a sequence of one or more commands separated by |. The
58 standard output of each command but the last is connected by a socket‐
59 pair(2) or (if the posix shell option is on) by a pipe(2) to the stan‐
60 dard input of the next command. Each command except the last is run
61 asynchronously in a subshell (see Subshells below). If the monitor or
62 pipefail option is on, or the pipeline is preceded by the reserved word
63 time, then the shell waits for all component commands in the pipeline
64 to terminate; otherwise, the shell only waits for the last component
65 command. The exit status of a pipeline is the exit status of its last
66 component command, unless the pipefail option is enabled. Each pipe‐
67 line can be preceded by the reserved word ! which causes the exit sta‐
68 tus of the pipeline to become 0 if the exit status of the last command
69 is non-zero, and 1 if the exit status of the last command is 0.
70 A list is a sequence of one or more pipelines separated by ;, &, |&,
72 &&, or ||, and optionally terminated by ;, &, or |&. Of these five
73 symbols, ;, &, and |& have equal precedence, which is lower than that
74 of && and ||. The symbols && and || also have equal precedence. A
75 semicolon (;) causes sequential execution of the preceding pipeline; an
76 ampersand (&) causes asynchronous execution of the preceding pipeline
77 (i.e., the shell does not wait for that pipeline to finish). The sym‐
78 bol |& causes asynchronous execution of the preceding pipeline with a
79 two-way pipe established to the parent shell; the standard input and
80 output of the spawned pipeline can be written to and read from by the
81 parent shell by applying the redirection operators <& and >& with arg p
82 to commands and by using -p option of the built-in commands read and
83 print described later. The symbol && (||) causes the list following it
84 to be executed only if the preceding pipeline returns a zero (non-zero)
85 value. One or more new-lines may appear in a list instead of a semi‐
86 colon, to delimit a command. The first item of the first pipeline of
87 a list that is a simple command not beginning with a redirection, and
88 not occurring within a while, until, or if list, can be preceded by a
89 semicolon. This semicolon is ignored unless the showme option is en‐
90 abled as described with the set built-in below.
91 A command is either a simple-command or a compound-command, which is
93 one of the following. Unless otherwise stated, the value returned by a
94 command is that of the last simple-command executed in the command.
95 for vname [ in word ... ] ;do list ;done
97 Each time a for command is executed, vname is set to the next
98 word taken from the in word list. If in word ... is omitted,
99 then the for command executes the do list once for each posi‐
100 tional parameter that is set starting from 1 (see Parameter Ex‐
101 pansion below). Execution ends when there are no more words in
102 the list.
103 for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
105 The arithmetic expression expr1 is evaluated first (see Arith‐
106 metic Evaluation below). The arithmetic expression expr2 is re‐
107 peatedly evaluated until it evaluates to zero and when non-zero,
108 list is executed and the arithmetic expression expr3 evaluated.
109 If any expression is omitted, then it behaves as if it evaluated
110 to 1.
111 select vname [ in word ... ] ;do list ;done
113 A select command prints on standard error (file descriptor 2)
114 the set of words, each preceded by a number. If in word ... is
115 omitted, then the positional parameters starting from 1 are used
116 instead (see Parameter Expansion below). The PS3 prompt is
117 printed and a line is read from the standard input. If this
118 line consists of the number of one of the listed words, then the
119 value of the variable vname is set to the word corresponding to
120 this number. If this line is empty, the selection list is
121 printed again. Otherwise the value of the variable vname is set
122 to the empty string. The contents of the line read from stan‐
123 dard input is saved in the variable REPLY. The list is executed
124 for each selection until a break or end-of-file is encountered.
125 If the REPLY variable is set to the empty string by the execu‐
126 tion of list, then the selection list is printed before display‐
127 ing the PS3 prompt for the next selection.
128 case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
130 A case command executes the list associated with the first pat‐
131 tern that matches word. The form of the patterns is the same as
132 that used for pathname expansion (see Pathname Expansion below).
133 The ;; operator causes execution of case to terminate. If ;& is
134 used in place of ;; the next subsequent list, if any, is exe‐
135 cuted.
136 if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
138 The list following if is executed and, if it returns a zero exit
139 status, the list following the first then is executed. Other‐
140 wise, the list following elif is executed and, if its value is
141 zero, the list following the next then is executed. Failing
142 each successive elif list, the else list is executed. If the if
143 list has non-zero exit status and there is no else list, then
144 the if command returns a zero exit status.
145 while list ;do list ;done
147 until list ;do list ;done
148 A while command repeatedly executes the while list and, if the
149 exit status of the last command in the list is zero, executes
150 the do list; otherwise the loop terminates. If no commands in
151 the do list are executed, then the while command returns a zero
152 exit status; until may be used in place of while to negate the
153 loop termination test.
154 while inputredirection ;do list ;done
156 Filescan loop. This is defined by a lone input redirection fol‐
157 lowing while (see Input/Output below). It is faster than using
158 the read built-in command in a regular while loop. The shell
159 reads lines from the file or stream opened by inputredirection
160 until the end is reached or the loop is broken. For each line
161 read, the command list is executed with the line's contents as‐
162 signed to the REPLY variable and the line's fields split into
163 the positional parameters (see Field Splitting and Positional
164 Parameters below). Within the list, standard input is redi‐
165 rected to /dev/null. If the posix compatibility shell option is
166 on, this loop type is disabled and inputredirection is processed
167 like a lone redirection in any other context.
168 ((expression))
170 The expression is evaluated using the rules for arithmetic eval‐
171 uation described below. If the value of the arithmetic expres‐
172 sion is non-zero, the exit status is 0, otherwise the exit sta‐
173 tus is 1.
174 (list)
176 Execute list in a subshell (see Subshells below). Note, that if
177 two adjacent open parentheses are needed for nesting, a space
178 must be inserted to avoid evaluation as an arithmetic command as
179 described above.
180 { list;}
182 list is simply executed. Note that unlike the metacharacters (
183 and ), { and } are reserved words and must occur at the begin‐
184 ning of a line or after a ; in order to be recognized.
185 [[ expression ]]
187 Evaluates expression and returns a zero exit status when expres‐
188 sion is true. See Conditional Expressions below, for a descrip‐
189 tion of expression.
190 function varname { list ;} [ redirection ... ]
192 varname () compound-command [ redirection ... ]
193 Define a function which is referenced by varname. A function
194 whose varname contains a . is called a discipline function and
195 the portion of the varname preceding the last . must refer to
196 an existing variable. The body of the function is the list of
197 commands between { and }. A function defined with the function
198 varname syntax can also be used as an argument to the . special
199 built-in command to get the equivalent behavior as if the var‐
200 name() syntax were used to define it. (See Functions below.)
201 namespace identifier { list ;}
203 Defines or uses the name space identifier and runs the commands
204 in list in this name space. (See Name Spaces below.)
205 time [ pipeline ]
207 If pipeline is omitted the user and system time for the current
208 shell and completed child processes is printed on standard er‐
209 ror. Otherwise, pipeline is executed and the elapsed time as
210 well as the user and system time are printed on standard error.
211 The TIMEFORMAT variable may be set to a format string that spec‐
212 ifies how the timing information should be displayed. See Shell
213 Variables below for a description of the TIMEFORMAT variable.
214 The following reserved words are recognized as reserved only when they
216 are the first word of a command and are not quoted:
217 if then else elif fi case esac for while until do done { } function se‐
219 lect time [[ ]] !
220 Variable Assignments.
222 One or more variable assignments can start a simple command or can be
223 arguments to the typeset, enum, export, or readonly special built-in
224 commands as well as to other declaration commands created as types.
225 The syntax for an assignment is of the form:
226 varname=word
228 varname[word]=word
229 No space is permitted between varname and the = or between = and
230 word.
231 varname=(assign_list)
233 No space is permitted between varname and the =. The variable
234 varname is unset before the assignment. An assign_list can be
235 one of the following:
236 word ...
237 Indexed array assignment.
238 [word]=word ...
239 Associative array assignment. If preceded by
240 typeset -a this will create an indexed array in‐
241 stead.
242 assignment ...
243 Compound variable assignment. This creates a
244 compound variable varname with subvariables of
245 the form varname.name, where name is the name
246 portion of assignment. The value of varname will
247 contain all the assignment elements. Additional
248 assignments made to subvariables of varname will
249 also be displayed as part of the value of var‐
250 name. If no assignments are specified, varname
251 will be a compound variable allowing subsequence
252 child elements to be defined.
253 typeset [options] assignment ...
254 Nested variable assignment. Multiple assignments
255 can be specified by separating each of them with
256 a ;. The previous value is unset before the as‐
257 signment. Other declaration commands such as
258 readonly, enum, and other declaration commands
259 can be used in place of typeset.
260 . filename
261 Include the assignment commands contained in
262 filename.
263 In addition, a += can be used in place of the = to signify adding to or
265 appending to the previous value. When += is applied to an arithmetic
266 type, word is evaluated as an arithmetic expression and added to the
267 current value. When applied to a string variable, the value defined by
268 word is appended to the value. For compound assignments, the previous
269 value is not unset and the new values are appended to the current ones
270 provided that the types are compatible.
271 The right hand side of a variable assignment undergoes all the expan‐
273 sion listed below except word splitting, brace expansion, and pathname
274 expansion. When the left hand side is an assignment is a compound
275 variable and the right hand is the name of a compound variable, the
276 compound variable on the right will be copied or appended to the com‐
277 pound variable on the left.
278 Comments.
280 A word beginning with # causes that word and all the following charac‐
281 ters up to a new-line to be ignored.
282 Aliasing.
284 The first word of each command is replaced by the text of an alias if
285 an alias for this word has been defined. An alias name consists of any
286 number of characters excluding metacharacters, quoting characters, file
287 expansion characters, parameter expansion and command substitution
288 characters, the characters / and =. The replacement string can contain
289 any valid shell script including the metacharacters listed above. The
290 first word of each command in the replaced text, other than any that
291 are in the process of being replaced, will be tested for aliases. If
292 the last character of the alias value is a blank then the word follow‐
293 ing the alias will also be checked for alias substitution. Aliases can
294 be used to redefine built-in commands but cannot be used to redefine
295 the reserved words listed above. Aliases can be created and listed
296 with the alias command and can be removed with the unalias command.
297 Aliasing is performed when scripts are read, not while they are exe‐
299 cuted. Therefore, for an alias to take effect, the alias definition
300 command has to be executed before the command which references the
301 alias is read.
302 The following aliases are automatically preset when the shell is in‐
304 voked as an interactive shell. Preset aliases can be unset or rede‐
305 fined.
306 history=′hist -l′
307 r=′hist -s′
308 Tilde Expansion.
310 After alias substitution is performed, each word is checked to see if
311 it begins with an unquoted ∼. For tilde expansion, word also refers to
312 the word portion of parameter expansion (see Parameter Expansion be‐
313 low). If a word is preceded by a tilde, then it is checked up to a /
314 to see if it matches a user name in the password database (see getpw‐
315 name(3)). If a match is found, the ∼ and the matched login name are
316 replaced by the login directory of the matched user. If no match is
317 found, the original text is left unchanged. A ∼ by itself, or in front
318 of a /, is replaced by $HOME, unless the HOME variable is unset, in
319 which case the current user's home directory as configured in the oper‐
320 ating system is used. A ∼ followed by a + or - is replaced by $PWD or
321 $OLDPWD respectively.
322 In addition, when expanding a variable assignment (see Variable Assign‐
324 ments above), tilde expansion is attempted when the value of the as‐
325 signment begins with a ∼, and when a ∼ appears after a :. A : also
326 terminates a user name following a ∼.
327 The tilde expansion mechanism may be extended or modified by defining
329 one of the discipline functions .sh.tilde.set or .sh.tilde.get (see
330 Functions and Discipline Functions below). If either exists, then upon
331 encountering a tilde word to expand, that function is called with the
332 tilde word assigned to either .sh.value (for the .sh.tilde.set func‐
333 tion) or .sh.tilde (for the .sh.tilde.get function). Performing tilde
334 expansion within a discipline function will not recursively call that
335 function, but default tilde expansion remains active, so literal tildes
336 should still be quoted where required. Either function may assign a
337 replacement string to .sh.value. If this value is non-empty and does
338 not start with a ∼, it replaces the default tilde expansion when the
339 function terminates. Otherwise, the tilde expansion is left unchanged.
340 Subshells.
342 A subshell is a separate execution environment that is a complete du‐
343 plicate of the current shell environment, except for two things: all
344 traps are reset to default except those for signals that are being ig‐
345 nored, and subshells cannot be interactive (i.e., they have no command
346 prompt). Changes made within a subshell do not affect the parent envi‐
347 ronment and are lost when the subshell exits.
348 Particular care should be taken not to confuse a subshell with a newly
350 invoked shell that is merely a child process of the current shell, and
351 which (unlike a subshell) starts from scratch in terms of variables and
352 functions and may be interactive. Beware of shell tutorials on the In‐
353 ternet that confuse these.
354 Subshells cannot be created or invoked using any command. Instead, the
356 following are automatically run in a subshell:
357 • any command or group of commands enclosed in parentheses;
359 • command substitutions of the first and third form (see Com‐
361 mand Substitution below);
362 • process substitutions (see Process Substitution below);
364 • all elements of a pipeline except the last;
366 • any command executed asynchronously (i.e., in a background
368 process).
369 Creating processes is expensive, so as a performance optimization, a
371 subshell of a non-interactive shell may share the process of its parent
372 environment. Such a subshell is known as a virtual subshell. Subshells
373 are virtual unless or until something (such as asynchronous execution,
374 or an attempt to set a process limit using the ulimit built-in command,
375 or other implementation- or system-defined requirements) makes it nec‐
376 essary to fork(2) it into a separate process. Barring any bugs in the
377 shell, virtual subshells should be indistinguishable from real sub‐
378 shells except by their execution speed and their process ID. See the
379 description of the .sh.pid variable below for more information.
380 Command Substitution.
382 The standard output from a command list enclosed in parentheses pre‐
383 ceded by a dollar sign ( $(list) ), or in a brace group preceded by a
384 dollar sign ( ${ list;} ), or in a pair of grave accents (``) may be
385 used as part or all of a word; trailing new-lines are removed. In the
386 second case, the { and } are treated as a reserved words so that { must
387 be followed by a blank and } must appear at the beginning of the line
388 or follow a ;. In the third (obsolete) form, the string between the
389 quotes is processed for special quoting characters before the command
390 is executed (see Quoting below). The command substitution $(cat file)
391 can be replaced by the equivalent but faster $(<file). The command
392 substitution $(n<#) will expand to the current byte offset for file de‐
393 scriptor n. Except for the second form, the command list is run in a
394 subshell so that no side effects are possible. For the second form,
395 the final } will be recognized as a reserved word after any token.
396 Arithmetic Expansion.
398 An arithmetic expression enclosed in double parentheses preceded by a
399 dollar sign ( $(()) ) is replaced by the value of the arithmetic ex‐
400 pression within the double parentheses.
401 Process Substitution.
403 Each command argument of the form <(list) or >(list) will run process
404 list asynchronously connected to some file in /dev/fd if this directory
405 exists, or else a fifo in a temporary directory. The name of this file
406 will become the argument to the command. If the form with > is se‐
407 lected then writing on this file will provide input for list. If < is
408 used, then the file passed as an argument will contain the output of
409 the list process. For example,
410 paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1)
412 >(process2)
413 cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
415 the results together, and sends it to the processes process1 and
416 process2, as well as putting it onto the standard output. Note that
417 the file, which is passed as an argument to the command, is a UNIX
418 pipe(2) so programs that expect to lseek(2) on the file will not work.
419 Process substitution of the form <(list) can also be used with the <
421 redirection operator which causes the output of list to be standard in‐
422 put or the input for whatever file descriptor is specified.
423 Parameter Expansion.
425 A parameter is a variable, one or more digits, or any of the characters
426 *, @, #, ?, -, $, and !. A variable is denoted by a vname. To create
427 a variable whose vname contains a ., a variable whose vname consists of
428 everything before the last . must already exist. A variable has a
429 value and zero or more attributes. Variables can be assigned values
430 and attributes by using the typeset special built-in command. The at‐
431 tributes supported by the shell are described later with the typeset
432 special built-in command. Exported variables pass their attributes to
433 the environment so that a newly invoked ksh that is a child or exec'd
434 process of the current shell will automatically import them, unless the
435 posix shell option is on.
436 The shell supports both indexed and associative arrays. An element of
438 an array variable is referenced by a subscript. A subscript for an in‐
439 dexed array is denoted by an arithmetic expression (see Arithmetic
440 Evaluation below) between a [ and a ]. To assign values to an indexed
441 array, use vname=(value ...) or set -A vname value ... . The value of
442 all non-negative subscripts must be in the range of 0 through
443 4,194,303. A negative subscript is treated as an offset from the maxi‐
444 mum current index +1 so that -1 refers to the last element. Indexed
445 arrays can be declared with the -a option to typeset. Indexed arrays
446 need not be declared. Any reference to a variable with a valid sub‐
447 script is legal and an array will be created if necessary.
448 An associative array is created with the -A option to typeset. A sub‐
450 script for an associative array is denoted by a string enclosed between
451 [ and ].
452 Referencing any array without a subscript is equivalent to referencing
454 the array with subscript 0.
455 The value of a variable may be assigned by writing:
457 vname=value [ vname=value ] ...
459 or
461 vname[subscript]=value [ vname[subscript]=value ] ...
463 Note that no space is allowed before or after the =.
465 Attributes assigned by the typeset special built-in command apply to
467 all elements of the array. An array element can be a simple variable,
468 a compound variable or an array variable. An element of an indexed ar‐
469 ray can be either an indexed array or an associative array. An element
470 of an associative array can also be either. To refer to an array ele‐
471 ment that is part of an array element, concatenate the subscript in
472 brackets. For example, to refer to the foobar element of an associa‐
473 tive array that is defined as the third element of the indexed array,
474 use ${vname[3][foobar]}
475 A nameref is a variable that is a reference to another variable. A
477 nameref is created with the -n attribute of typeset or with the equiva‐
478 lent nameref command. The value of the variable at the time of that
479 command becomes the variable that will be referenced whenever the
480 nameref variable is used. The name of a nameref cannot contain a ..
481 When a variable or function name contains a ., and the portion of the
482 name up to the first . matches the name of a nameref, the variable re‐
483 ferred to is obtained by replacing the nameref portion with the name of
484 the variable referenced by the nameref. If a nameref is used as the
485 index of a for loop, a name reference is established for each item in
486 the list.
487 A nameref provides a convenient way to refer to the variable inside a
489 function whose name is passed as an argument to a function. For exam‐
490 ple, if the name of a variable is passed as the first argument to a
491 function, the command typeset -n var=$1 (a.k.a. nameref var=$1) inside
492 the function causes references and assignments to var to be references
493 and assignments to the variable whose name has been passed to the func‐
494 tion. Note that, for this to work, the positional parameter must be
495 assigned directly to the nameref as part of the declaration command, as
496 in the example above; only that idiom can allow one function to access
497 a local variable of another. For instance, typeset -n var; var=$1
498 won't cross that barrier, nor will typeset foo=$1; typeset -n var=foo.
499 If any of the floating point attributes, -E, -F, or -X, or the integer
501 attribute, -i, is set for vname, then the value is subject to arith‐
502 metic evaluation as described below.
503 Positional parameters, parameters denoted by a number, may be assigned
505 values with the set special built-in command. Parameter $0 is set from
506 argument zero when the shell is invoked.
507 The character $ is used to introduce substitutable parameters.
509 ${parameter}
511 The shell reads all the characters from ${ to the matching } as
512 part of the same word even if it contains braces or metacharac‐
513 ters. The value, if any, of the parameter is substituted. The
514 braces are required when parameter is followed by a letter,
515 digit, or underscore that is not to be interpreted as part of
516 its name, when the variable name contains a .. The braces are
517 also required when a variable is subscripted unless it is part
518 of an Arithmetic Expression or a Conditional Expression. If pa‐
519 rameter is one or more digits then it is a positional parameter.
520 A positional parameter of more than one digit must be enclosed
521 in braces. If parameter is * or @, then all the positional pa‐
522 rameters, starting with $1, are substituted (separated by a
523 field separator character). If an array vname with last sub‐
524 script * @, or for indexed arrays of the form sub1 .. sub2. is
525 used, then the value for each of the elements between sub1 and
526 sub2 inclusive (or all elements for * and @) is substituted,
527 separated by the first character of the value of IFS.
528 ${#parameter}
530 If parameter is * or @, the number of positional parameters is
531 substituted. Otherwise, the length of the value of the parame‐
532 ter is substituted.
533 ${#vname[*]}
535 ${#vname[@]}
536 The number of elements in the array vname is substituted.
537 ${@vname}
539 Expands to the type name (See Type Variables below) or at‐
540 tributes of the variable referred to by vname.
541 ${!vname}
543 Expands to the name of the variable referred to by vname. This
544 will be vname except when vname is a name reference.
545 ${!vname[subscript]}
547 Expands to name of the subscript unless subscript is *, @. or
548 of the form sub1 .. sub2. When subscript is *, the list of ar‐
549 ray subscripts for vname is generated. For a variable that is
550 not an array, the value is 0 if the variable is set. Otherwise
551 it is the empty string. When subscript is @, same as above, ex‐
552 cept that when used in double quotes, each array subscript
553 yields a separate argument. When subscript is of the form sub1
554 .. sub2 it expands to the list of subscripts between sub1 and
555 sub2 inclusive using the same quoting rules as @.
556 ${!prefix@}
558 ${!prefix*}
559 These both expand to the names of the variables whose names be‐
560 gin with prefix. The expansions otherwise work like $@ and $*,
561 respectively (see under Quoting below).
562 ${parameter:-word}
564 If parameter is set and has a non-empty value, then substitute
565 its value; otherwise substitute word.
566 ${parameter:=word}
568 If parameter is not set or has the empty string value, then set
569 it to word; the value of the parameter is then substituted. Po‐
570 sitional parameters may not be assigned to in this way.
571 ${parameter:?word}
573 If parameter is set and has a non-empty value, then substitute
574 its value; otherwise, print word and exit from the shell (if not
575 interactive). If word is omitted then a standard message is
576 printed.
577 ${parameter:+word}
579 If parameter is set and has a non-empty value then substitute
580 word; otherwise substitute the empty string.
581 In the above, word is not evaluated unless it is to be used as the sub‐
583 stituted string, so that, in the following example, pwd is executed
584 only if d is not set or has the empty string value:
585 print ${d:-$(pwd)}
587 If the colon (:) is omitted from the above expressions, then the shell
589 only checks whether parameter is set or not.
590 ${parameter:offset:length}
592 ${parameter:offset}
593 Expands to the portion of the value of parameter starting at the
594 character (counting from 0) determined by expanding offset as an
595 arithmetic expression and consisting of the number of characters
596 determined by the arithmetic expression defined by length. In
597 the second form, the remainder of the value is used. If A nega‐
598 tive offset counts backwards from the end of parameter. Note
599 that one or more blanks is required in front of a minus sign to
600 prevent the shell from interpreting the operator as :-. If pa‐
601 rameter is * or @, or is an array name indexed by * or @, then
602 offset and length refer to the array index and number of ele‐
603 ments respectively. A negative offset is taken relative to one
604 greater than the highest subscript for indexed arrays. The or‐
605 der for associative arrays is unspecified.
606 ${parameter#pattern}
608 ${parameter##pattern}
609 If the shell pattern matches the beginning of the value of pa‐
610 rameter, then the value of this expansion is the value of the
611 parameter with the matched portion deleted; otherwise the value
612 of this parameter is substituted. In the first form the small‐
613 est matching pattern is deleted and in the second form the
614 largest matching pattern is deleted. When parameter is @, *, or
615 an array variable with subscript @ or *, the substring operation
616 is applied to each element in turn.
617 ${parameter%pattern}
619 ${parameter%%pattern}
620 If the shell pattern matches the end of the value of parameter,
621 then the value of this expansion is the value of the parameter
622 with the matched part deleted; otherwise substitute the value of
623 parameter. In the first form the smallest matching pattern is
624 deleted and in the second form the largest matching pattern is
625 deleted. When parameter is @, *, or an array variable with sub‐
626 script @ or *, the substring operation is applied to each ele‐
627 ment in turn.
628 ${parameter/pattern/string}
630 ${parameter//pattern/string}
631 ${parameter/#pattern/string}
632 ${parameter/%pattern/string}
633 Expands parameter and replaces the longest match of pattern with
634 the given string. Each occurrence of \n in string is replaced
635 by the portion of parameter that matches the n-th subpattern.
636 In the first form, only the first occurrence of pattern is re‐
637 placed. In the second form, each match for pattern is replaced
638 by the given string. The third form restricts the pattern match
639 to the beginning of the string while the fourth form restricts
640 the pattern match to the end of the string. In the first and
641 second forms, an empty pattern never matches. In the third and
642 fourth forms, an empty pattern matches the beginning or the end
643 of the string, respectively. When string is empty, the pattern
644 will be deleted and the / in front of string may be omitted.
645 When parameter is @, *, or an array variable with subscript @ or
646 *, the substitution operation is applied to each element in
647 turn. In this case, the string portion of word will be re-eval‐
648 uated for each element.
649 Shell Variables.
651 The following parameters are automatically set by the shell:
652 # The number of positional parameters in decimal.
653 - Options supplied to the shell on invocation or by the set
655 command.
656 ? The exit status returned by the last executed command.
658 Its meaning depends on the command or function that de‐
659 fines it, but there are conventions that other commands
660 often depend on: zero typically means 'success' or
661 'true', one typically means 'non-success' or 'false', and
662 a value greater than one typically indicates some kind of
663 error. Only the 8 least significant bits of $? (values 0
664 to 255) are preserved when the exit status is passed on
665 to a parent process, but within the same (sub)shell envi‐
666 ronment, it is a signed integer value with a range of
667 possible values as shown by the commands getconf INT_MIN
668 and getconf INT_MAX. Shell functions that run in the cur‐
669 rent environment may return status values in this range.
670 $ The process ID of the main shell process. Note that this
672 value will not change in a subshell, even if the subshell
673 runs in a different process. See also .sh.pid.
674 _ Initially, the value of _ is an absolute pathname of the
676 shell or script being executed as passed in the environ‐
677 ment. Subsequently it is assigned the last argument of
678 the previous command. This parameter is not set for com‐
679 mands which are asynchronous. This parameter is also
680 used to hold the name of the matching MAIL file when
681 checking for mail. While defining a compound variable or
682 a type, _ is initialized as a reference to the compound
683 variable or type. When a discipline function is invoked,
684 _ is initialized as a reference to the variable associ‐
685 ated with the call to this function. Finally when _ is
686 used as the name of the first variable of a type defini‐
687 tion, the new type is derived from the type of the first
688 variable. (See Type Variables below.)
689 ! The process ID of the last background command invoked or
691 the most recent job put in the background with the bg
692 built-in command.
693 .sh.command
695 When processing a DEBUG trap, this variable contains the
696 current command line that is about to run. The value is
697 in the same format as the output generated by the xtrace
698 option (minus the preceding PS4 prompt).
699 .sh.edchar
701 This variable contains the value of the keyboard charac‐
702 ter (or sequence of characters if the first character is
703 an ESC, ASCII 033) that has been entered when processing
704 a KEYBD trap (see Key Bindings below). If the value is
705 changed as part of the trap action, then the new value
706 replaces the key (or key sequence) that caused the trap.
707 .sh.edcol
709 The character position of the cursor at the time of the
710 most recent KEYBD trap.
711 .sh.edmode
713 Upon executing a KEYBD trap action, the value of this
714 variable is set to the ESC control character if the shell
715 is in vi input mode (See Vi Editing Mode below), or to
716 the empty string value otherwise.
717 .sh.edtext
719 The characters in the input buffer at the time of the
720 most recent KEYBD trap. The variable is unset when not
721 processing a KEYBD trap.
722 .sh.file
724 The pathname of the file that contains the current com‐
725 mand.
726 .sh.fun
728 The name of the current function that is being executed.
729 .sh.level
731 Set to the current call depth of functions and dot
732 scripts. Normally, this variable is read-only, but while
733 executing a DEBUG trap, its value may be changed to
734 switch the current function scope to that of the speci‐
735 fied level for the duration of the trap run, making it
736 possible to access a parent scope for debugging purposes.
737 When trap execution ends, the variable and the scope are
738 restored. It is an error to assign a value lower than 0
739 (the global scope) or higher than the current call depth.
740 .sh.lineno
742 Set during a DEBUG trap to the line number for the caller
743 of each function.
744 .sh.match
746 Whenever a match is found in a pattern matching operation
747 using either the [[ compound command (see Conditional Ex‐
748 pressions below) or the expansions ${parameter#pattern},
749 ${parameter%pattern}, ${parameter/pattern/string}, or one
750 of their variants (see Parameter Expansion above), the
751 match and its subpattern matches are stored in this in‐
752 dexed array, overwriting its previous values. The 0-th
753 element stores the complete match and the i-th element
754 stores the i-th submatch. For //, the array is two-di‐
755 mensional, with the first subscript indicating the most
756 recent match and subpattern match, and the second sub‐
757 script indicating which match with 0 representing the
758 first match. If no match is found, .sh.match is not re‐
759 set or modified. Note that even matching operations per‐
760 formed on the .sh.match variable itself will overwrite it
761 upon finding a match.
762 .sh.math
764 Used for defining arithmetic functions (see Arithmetic
765 Evaluation below) and stores the list of user defined
766 arithmetic functions.
767 .sh.name
769 Set to the name of the variable at the time that a disci‐
770 pline function is invoked.
771 .sh.subscript
773 Set to the name subscript of the variable at the time
774 that a discipline function is invoked.
775 .sh.subshell
777 The current depth for subshells and command substitution.
778 .sh.pid
780 Set to the process ID of the current shell process. Un‐
781 like $$, this is updated in a subshell when it forks into
782 a new process. Note that a virtual subshell may have to
783 fork mid-execution due to various system- and implementa‐
784 tion-dependent requirements, so the value should not be
785 counted on to remain the same from one command to the
786 next. If a persistent process ID is required for a sub‐
787 shell, it must be ensured it is running in its own
788 process first. Any attempt to set a process limit using
789 the ulimit built-in command, such as ulimit -t unlimited
790 2>/dev/null, is a reliable way to make a subshell fork if
791 it hasn't already.
792 .sh.ppid
794 Set to the process ID of the parent of the current shell
795 process. Unlike $PPID, this is updated in a subshell
796 when it forks into a new process. The same note as for
797 .sh.pid applies.
798 .sh.value
800 Set to the value of the variable at the time that the set
801 or append discipline function is invoked. When a user
802 defined arithmetic function is invoked, the value of
803 .sh.value is saved and .sh.value is set to long double
804 precision floating point. .sh.value is restored when the
805 function returns.
806 .sh.version
808 Set to a value that identifies the version of this shell.
809 COLUMNS
811 Width of the terminal window in character positions. Up‐
812 dated automatically at initialization and on receiving a
813 SIGWINCH signal. The shell uses the value to define the
814 width of the edit window for the shell edit modes and for
815 printing select lists.
816 KSH_VERSION
818 A name reference to .sh.version.
819 LINENO The current line number within the script or function be‐
821 ing executed.
822 LINES Height of the terminal window in lines. Updated automat‐
824 ically at initialization and on receiving a SIGWINCH sig‐
825 nal. The shell uses the value to determine the column
826 length for printing select lists: they are printed verti‐
827 cally until about two thirds of LINES lines are filled.
828 OLDPWD The previous working directory set by the cd command.
830 OPTARG The value of the last option argument processed by the
832 getopts built-in command.
833 OPTIND The index of the last option argument processed by the
835 getopts built-in command.
836 PPID The process ID of the parent of the main shell process.
838 Note that this value will not change in a subshell, even
839 if the subshell runs in a different process. See also
840 .sh.ppid.
841 PWD The present working directory set by the cd command.
843 RANDOM Each time this variable is referenced, a random integer,
845 uniformly distributed between 0 and 32767, is generated.
846 The sequence of random numbers can be initialized by as‐
847 signing a numeric value to RANDOM.
848 REPLY This variable is set by the select statement and by the
850 read built-in command when no arguments are supplied.
851 SECONDS
853 Each time this variable is referenced, the number of sec‐
854 onds since shell invocation is returned. If this vari‐
855 able is assigned a value, then the value returned upon
856 reference will be the value that was assigned plus the
857 number of seconds since the assignment.
858 SHLVL An integer variable that is incremented and exported each
860 time the shell is invoked. If SHLVL is not in the envi‐
861 ronment when the shell is invoked, it is set to 1.
862 The following variables are used by the shell:
864 CDPATH The search path for the cd command.
865 EDITOR If the VISUAL variable is not set, the value of this
867 variable will be checked for certain patterns and the
868 corresponding editing option will be turned on as de‐
869 scribed with VISUAL below.
870 ENV If this variable is set, then parameter expansion, com‐
872 mand substitution, and arithmetic expansion are performed
873 on the value to generate the pathname of the script that
874 will be executed when the shell is invoked interactively
875 (see Invocation below). This file is typically used for
876 alias and function definitions. The default value is
877 $HOME/.kshrc. On systems that support a system wide
878 /etc/ksh.kshrc initialization file, if the filename gen‐
879 erated by the expansion of ENV begins with /./ or ././
880 the system wide initialization file will not be executed.
881 FCEDIT Obsolete name for the default editor name for the hist
883 command. FCEDIT is not used when HISTEDIT is set.
884 FIGNORE
886 A pattern that defines the set of filenames that will be
887 ignored when performing filename matching.
888 FPATH The search path for function definitions. The directo‐
890 ries in this path are searched for a file with the same
891 name as the function or command when a function with the
892 -u attribute is referenced and when a command is not
893 found. If an executable file with the name of that com‐
894 mand is found, then it is read and executed in the cur‐
895 rent environment. Unlike PATH, the current directory
896 must be represented explicitly by . rather than by adja‐
897 cent : characters or a beginning or ending :.
898 histchars
900 This variable can be used to specify up to three ASCII
901 characters that control history expansion (see History
902 Expansion below). The first (default: !) signals the
903 start of a history expansion. The second (default: ^) is
904 used for short-form substitutions. The third (default:
905 #), when found as the first character of a word, causes
906 history expansion to be skipped for the rest of the words
907 on the line. Multi-byte characters (e.g. UTF-8) are not
908 supported and produce undefined results.
909 HISTCMD
911 Number of the current command in the history file.
912 HISTEDIT
914 Name for the default editor name for the hist command.
915 HISTFILE
917 If this variable is set when the shell is invoked, then
918 the value is the pathname of the file that will be used
919 to store the command history (see Command Re-entry be‐
920 low).
921 HISTSIZE
923 If this variable is set when the shell is invoked, then
924 the number of previously entered commands that are acces‐
925 sible by this shell will be greater than or equal to this
926 number. The default is 512.
927 HOME The default argument (home directory) for the cd command.
929 IFS Internal field separators, normally space, tab, and new-
931 line that are used to separate the results of command
932 substitution or parameter expansion and to separate
933 fields with the built-in command read. The first charac‐
934 ter of the IFS variable is used to separate arguments for
935 the "$*" expansion (see Quoting below). Each single oc‐
936 currence of an IFS character in the string to be split
937 that is not in the isspace character class, and any adja‐
938 cent characters in IFS that are in the isspace character
939 class, delimit a field. One or more characters in IFS
940 that belong to the isspace character class delimit a
941 field. In addition, if the same isspace character ap‐
942 pears consecutively inside IFS and the posix shell option
943 is not on, this character is treated as if it were not in
944 the isspace class - for example, if IFS consists of two
945 tab characters, then two adjacent tab characters delimit
946 an empty field.
947 JOBMAX This variable defines the maximum number running back‐
949 ground jobs that can run at a time. When this limit is
950 reached, the shell will wait for a job to complete before
951 starting a new job.
952 LANG This variable determines the locale category for any cat‐
954 egory not specifically selected with a variable starting
955 with LC_ or LANG.
956 LC_ALL This variable overrides the value of the LANG variable
958 and any other LC_ variable.
959 LC_COLLATE
961 This variable determines the locale category for charac‐
962 ter collation information.
963 LC_CTYPE
965 This variable determines the locale category for charac‐
966 ter handling functions. It determines the character
967 classes for pattern matching (see Pathname Expansion be‐
968 low).
969 LC_NUMERIC
971 This variable determines the locale category for the dec‐
972 imal point character.
973 MAIL If this variable is set to the name of a mail file and
975 the MAILPATH variable is not set, then the shell informs
976 the user of arrival of mail in the specified file.
977 MAILCHECK
979 This variable specifies how often (in seconds) the shell
980 will check for changes in the modification time of any of
981 the files specified by the MAILPATH or MAIL variables.
982 The default value is 600 seconds. When the time has
983 elapsed the shell will check before issuing the next
984 prompt.
985 MAILPATH
987 A colon ( : ) separated list of file names. If this
988 variable is set, then the shell informs the user of any
989 modifications to the specified files that have occurred
990 within the last MAILCHECK seconds. Each file name can be
991 followed by a ? and a message that will be printed. The
992 message will undergo parameter expansion, command substi‐
993 tution, and arithmetic expansion with the variable $_ de‐
994 fined as the name of the file that has changed. The de‐
995 fault message is you have mail in $_.
996 PATH The search path for commands (see Execution below). The
998 user may not change PATH if executing under rksh (except
999 in .profile).
1000 PS1 Every time a new command line is started on an interac‐
1002 tive shell, the value of this variable is expanded to re‐
1003 solve backslash escaping, parameter expansion, command
1004 substitution, and arithmetic expansion. The result de‐
1005 fines the primary prompt string for that command line.
1006 The default is ``$ ''. The character ! in the primary
1007 prompt string is replaced by the command number (see Com‐
1008 mand Re-entry below). Two successive occurrences of !
1009 will produce a single ! when the prompt string is
1010 printed. Note that any terminal escape sequences used in
1011 the PS1 prompt thus need every instance of ! in them to
1012 be changed to !!.
1013 PS2 Secondary prompt string, by default ``> ''.
1015 PS3 Selection prompt string used within a select loop, by de‐
1017 fault ``#? ''.
1018 PS4 The value of this variable is expanded for parameter
1020 evaluation, command substitution, and arithmetic expan‐
1021 sion and precedes each line of an execution trace. By
1022 default, PS4 is ``+ ''. In addition when PS4 is unset,
1023 the execution trace prompt is also ``+ ''.
1024 SHELL The pathname of the shell is kept in the environment. At
1026 invocation, if the basename of this variable is rsh,
1027 rksh, or krsh, then the shell becomes restricted.
1028 TIMEFORMAT
1030 The value of this parameter is used as a format string
1031 specifying how the timing information for pipelines pre‐
1032 fixed with the time reserved word should be displayed.
1033 The % character introduces a format sequence that is ex‐
1034 panded to a time value or other information. The format
1035 sequences and their meanings are as follows.
1036 %% A literal %.
1037 %[p][l]R The elapsed time in seconds.
1038 %[p][l]U The number of CPU seconds spent in user mode.
1039 %[p][l]S The number of CPU seconds spent in system mode.
1040 %P The CPU percentage, computed as (U + S) / R.
1041 The brackets denote optional portions. The optional p is
1043 a digit specifying the precision, the number of frac‐
1044 tional digits after a decimal point. A value of 0 causes
1045 no decimal point or fraction to be output. At most three
1046 places after the decimal point can be displayed; values
1047 of p greater than 3 are treated as 3. If p is not speci‐
1048 fied, the value 3 is used.
1049 The optional l specifies a longer format, including hours
1051 if greater than zero, minutes, and seconds of the form
1052 HHhMMmSS.FFs. The value of p determines whether or not
1053 the fraction is included. Seconds are zero-padded unless
1054 the posix shell option is on.
1055 All other characters are output without change and a
1057 trailing newline is added. If the variable is unset, the
1058 default value, $'\nreal\t%2lR\nuser\t%2lU\nsys\t%2lS', is
1059 used. If the value is empty, no timing information is
1060 displayed.
1061 TMOUT Terminal read timeout. If set to a value greater than
1063 zero, the read built-in command and the select compound
1064 command time out after TMOUT seconds when input is from a
1065 terminal. An interactive shell will issue a warning and
1066 allow for an extra 60 second timeout grace period before
1067 terminating if a line is not entered within the pre‐
1068 scribed number of seconds while reading from a terminal.
1069 (Note that the shell can be compiled with a maximum bound
1070 for this value which cannot be exceeded.)
1071 VISUAL The value of this variable is scanned when the shell is
1073 invoked and whenever its value is changed; if it is found
1074 to match certain patterns, the corresponding line editor
1075 (see In-line Editing Options below) is activated. If it
1076 matches the pattern *[Vv][Ii]*, the vi option is turned
1077 on; else if it matches the pattern *gmacs*, the gmacs op‐
1078 tion is turned on; else if it matches the pattern *macs*,
1079 the emacs option is turned on. If none of the patterns
1080 match, emacs is turned on by default upon initializing an
1081 interactive shell. If the value is changed by assignment
1082 and none of the patterns match, no options are changed.
1083 The value of VISUAL overrides the value of EDITOR.
1084 The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
1086 FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, histchars, and MAIL are
1087 not set at all by the shell (although HOME is set by login(1)). On
1088 some systems MAIL and SHELL are also set by login(1).
1089 Field Splitting.
1091 After parameter expansion and command substitution, the results of sub‐
1092 stitutions are scanned for the field separator characters (those found
1093 in IFS) and split into distinct fields where such characters are found.
1094 Explicit empty fields ("" or ′′) are retained. Implicit empty fields
1095 (those resulting from parameters that are unset or have empty string
1096 values or from command substitutions yielding the empty string, and
1097 that are not quoted with "") are removed.
1098 Brace Expansion.
1100 If the braceexpand (-B) option is set then each word, as well as any
1101 fields resulting from field splitting (see above), are checked to see
1102 if they contain one or more of the brace patterns {*,*}, {l1..l2} ,
1103 {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} , or {n1..n2 ..n3%fmt} , where
1104 * represents any character, l1,l2 are letters and n1,n2,n3 are signed
1105 numbers and fmt is a format specified as used by printf. In each case,
1106 fields are created by prepending the characters before the { and ap‐
1107 pending the characters after the } to each of the strings generated by
1108 the characters between the { and }. The resulting fields are checked
1109 to see if they have any brace patterns.
1110 In the first form, a field is created for each string between { and ,,
1112 between , and ,, and between , and }. The string represented by * can
1113 contain embedded matching { and } without quoting. Otherwise, each {
1114 and } with * must be quoted.
1115 In the seconds form, l1 and l2 must both be either upper case or both
1117 be lower case characters in the C locale. In this case a field is cre‐
1118 ated for each character from l1 through l2.
1119 In the remaining forms, a field is created for each number starting at
1121 n1 and continuing until it reaches n2 incrementing n1 by n3. The cases
1122 where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 oth‐
1123 erwise. If forms which specify %fmt any format flags, widths and pre‐
1124 cisions can be specified and fmt can end in any of the specifiers
1125 cdiouxX. For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8
1126 fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z04cx.
1127 Pathname Expansion.
1129 This is also known as globbing or sometimes filename generation. Path‐
1130 name expansion is disabled if the -f a.k.a. --noglob shell option is
1131 on. Otherwise, if certain special characters are found in a word or in
1132 a field resulting from field splitting (see above), then the word or
1133 field is regarded as a pattern. Each literal word is scanned for the
1134 characters *, ?, [, and (, but fields resulting from field splitting
1135 are scanned only for the characters *, ?, and [ for compatibility rea‐
1136 sons (in which case the ( character is not special and any pattern syn‐
1137 tax described below that involves parentheses does not apply).
1138 Each file name component that contains a recognized pattern character
1140 is replaced with a lexicographically sorted set of names that matches
1141 the pattern from that directory. If no file name is found that matches
1142 the pattern, then that component of the filename is left unchanged un‐
1143 less the pattern is prefixed with ∼(N), in which case it is removed as
1144 described below. The special traversal names . and .. are never
1145 matched. If FIGNORE is set, then each file name component that matches
1146 the pattern defined by the value of FIGNORE is ignored when generating
1147 the matching filenames. If FIGNORE is not set, the character . at the
1148 start of each file name component will be ignored unless the first
1149 character of the pattern corresponding to this component is the charac‐
1150 ter . itself. Note that, for uses of pattern matching other than
1151 pathname expansion, the / and . are not treated specially.
1152 * Matches any string, including the empty string. When
1154 used for filename expansion, if the globstar option is
1155 on, an isolated pattern of two adjacent *s will match all
1156 files and zero or more directories and subdirectories.
1157 If followed by a / then only directories and subdirecto‐
1158 ries will match.
1159 ? Matches any single character.
1160 [...] Matches any one of the enclosed characters. A pair of
1161 characters separated by - matches any character lexically
1162 between the pair, inclusive. If the first character fol‐
1163 lowing the opening [ is a ! or ^, then any character not
1164 enclosed is matched. A - can be included in the charac‐
1165 ter set by putting it as the first or last character.
1166 Within [ and ], character classes can be specified with
1167 the syntax [:class:], where class is one of the following
1168 classes defined in the ANSI C standard (note that word is
1169 equivalent to alnum plus the character _):
1170 alnum alpha blank cntrl digit graph lower print punct
1171 space upper word xdigit
1172 Within [ and ], an equivalence class can be specified
1173 with the syntax [=c=] which matches all characters with
1174 the same primary collation weight (as defined by the cur‐
1175 rent locale) as the character c. Within [ and ], [.sym‐
1176 bol.] matches the collating symbol symbol.
1177 A pattern-list is a list of one or more patterns separated from each
1179 other with a & or |. A & signifies that all patterns must be matched
1180 whereas | requires that only one pattern be matched. Composite pat‐
1181 terns can be formed with one or more of the following subpatterns:
1182 ?(pattern-list)
1183 Optionally matches any one of the given patterns.
1184 *(pattern-list)
1185 Matches zero or more occurrences of the given patterns.
1186 +(pattern-list)
1187 Matches one or more occurrences of the given patterns.
1188 {n}(pattern-list)
1189 Matches n occurrences of the given patterns.
1190 {m,n}(pattern-list)
1191 Matches from m to n occurrences of the given patterns.
1192 If m is omitted, 0 will be used. If n is omitted, at
1193 least m occurrences will be matched.
1194 @(pattern-list)
1195 Matches exactly one of the given patterns.
1196 !(pattern-list)
1197 Matches anything except one of the given patterns.
1198 By default, each pattern or subpattern will match the longest string
1200 possible consistent with generating the longest overall match. If more
1201 than one match is possible, the one starting closest to the beginning
1202 of the string will be chosen. However, for each of the above compound
1203 patterns, a - can be inserted in front of the ( to cause the shortest
1204 match to the specified pattern-list to be used.
1205 When pattern-list is contained within parentheses, the backslash char‐
1207 acter \ is treated specially even when inside a character class. All
1208 ANSI C character escapes are recognized and match the specified charac‐
1209 ter. In addition, the following escape sequences are recognized:
1210 \d Matches any character in the digit class.
1211 \D Matches any character not in the digit class.
1212 \s Matches any character in the space class.
1213 \S Matches any character not in the space class.
1214 \w Matches any character in the word class.
1215 \W Matches any character not in the word class.
1216 A pattern of the form %(pattern-pair(s)) is a subpattern that can be
1218 used to match nested character expressions. Each pattern-pair is a
1219 two-character sequence that cannot contain & or |. The first pattern-
1220 pair specifies the starting and ending characters for the match. Each
1221 subsequent pattern-pair represents the beginning and ending characters
1222 of a nested group that will be skipped over when counting starting and
1223 ending character matches. The behavior is unspecified when the first
1224 character of a pattern-pair is alphanumeric, except for the following:
1225 D Causes the ending character to terminate the search for
1226 this pattern without finding a match.
1227 E Causes the ending character to be interpreted as an es‐
1228 cape character.
1229 L Causes the ending character to be interpreted as a quote
1230 character, causing all characters to be ignored when
1231 looking for a match.
1232 Q Causes the ending character to be interpreted as a quote
1233 character, causing all characters other than any escape
1234 character to be ignored when looking for a match.
1235 Thus, %({}Q"E\), matches characters starting at { until the matching }
1237 is found, not counting any { or } that is inside a double-quoted string
1238 or preceded by the escape character \. Without the {}, this pattern
1239 matches any C language string.
1240 Each subpattern in a composite pattern is numbered, starting at 1, by
1242 the location of the ( within the pattern. The sequence \n, where n is
1243 a single digit and \n comes after the nth subpattern, matches the same
1244 string as the subpattern itself.
1245 Finally, a pattern can contain subpatterns of the form ∼(options:pat‐
1247 tern-list), where either options or :pattern-list can be omitted. Un‐
1248 like the other compound patterns, these subpatterns are not counted in
1249 the numbered subpatterns. :pattern-list must be omitted for options E,
1250 F, G, N, P, V, and X below. If options is present, it can consist of
1251 one or more of the following:
1252 + Enable the following options. This is the default.
1253 - Disable the following options.
1254 E The remainder of the pattern uses extended regular ex‐
1255 pression syntax like the -E option of the grep(1) com‐
1256 mand.
1257 F The remainder of the pattern uses the fixed pattern syn‐
1258 tax of the -F option of the grep(1) command.
1259 G The remainder of the pattern uses basic regular expres‐
1260 sion syntax like the grep(1) command without options.
1261 K The remainder of the pattern uses shell pattern syntax.
1262 This is the default.
1263 N When it is the first letter and is used with pathname ex‐
1264 pansion, and no matches occur, the file pattern expands
1265 to the empty string instead of remaining unexpanded.
1266 Otherwise, it is ignored.
1267 X The remainder of the pattern uses augmented regular ex‐
1268 pression syntax like the -X option of the AT&T AST ver‐
1269 sion of the grep(1) command.
1270 P The remainder of the pattern uses perl(1) regular expres‐
1271 sion syntax. Not all perl regular expression syntax is
1272 currently implemented.
1273 V The remainder of the pattern uses System V regular ex‐
1274 pression syntax.
1275 i Always treat the match as case-insensitive, regardless of
1276 the globcasedetect shell option.
1277 g File the longest match (greedy). This is the default.
1278 l Left-anchor the pattern. This is the default for K style
1279 patterns.
1280 r Right-anchor the pattern. This is the default for K
1281 style patterns.
1282 If both options and :pattern-list are specified, then the options apply
1284 only to pattern-list. Otherwise, these options remain in effect until
1285 they are disabled by a subsequent ∼(...) or at the end of the subpat‐
1286 tern containing ∼(...).
1287 Quoting.
1289 Each of the metacharacters listed earlier (see Definitions above) has a
1290 special meaning to the shell and causes termination of a word unless
1291 quoted. A character may be quoted (i.e., made to stand for itself) by
1292 preceding it with a \. The pair \new-line is removed. All characters
1293 enclosed between a pair of single quote marks (′′) that is not preceded
1294 by a $ are quoted. A single quote cannot appear within the single
1295 quotes. A single quoted string preceded by an unquoted $ is processed
1296 as an ANSI C string except for the following:
1297 \0 Causes the remainder of the string to be ignored.
1298 \E Equivalent to the escape character (ASCII 033),
1299 \e Equivalent to the escape character (ASCII 033),
1300 \cx Expands to the character control-x.
1301 \C[.name.]
1302 Expands to the collating element name.
1303 Inside double quote marks (""), parameter and command substitution oc‐
1305 cur and \ quotes the characters \, `, ", and $. A $ in front of a dou‐
1306 ble quoted string will be ignored in the "C" or "POSIX" locale, and may
1307 cause the string to be replaced by a locale specific string otherwise.
1308 The meaning of $* and $@ is identical when not quoted or when used as a
1309 variable assignment value or as a file name. However, when used as a
1310 command argument, "$*" is equivalent to "$1d$2d...", where d is the
1311 first character of the IFS variable, whereas "$@" is equivalent to "$1"
1312 "$2" .... Inside grave quote marks (``), \ quotes the characters \, `,
1313 and $. If the grave quotes occur within double quotes, then \ also
1314 quotes the character ".
1315 The special meaning of reserved words or aliases can be removed by
1317 quoting any character of the reserved word. The recognition of func‐
1318 tion names or built-in command names listed below cannot be altered by
1319 quoting them.
1320 Arithmetic Evaluation.
1322 The shell performs arithmetic evaluation for arithmetic expansion, to
1323 evaluate an arithmetic command, to evaluate an indexed array subscript,
1324 and to evaluate arguments to the built-in commands shift and let as
1325 well as arguments to numeric format specifiers given to print -f and
1326 printf. Evaluations are performed using double precision floating
1327 point arithmetic or long double precision floating point for systems
1328 that provide this data type. Floating point constants follow the ANSI
1329 C programming language floating point conventions. The case-insensi‐
1330 tive floating point constants NaN and Inf can be used to represent "not
1331 a number" and infinity respectively, unless the posix shell option is
1332 on. Integer constants follow the ANSI C programming language integer
1333 constant conventions although only single byte character constants are
1334 recognized and character casts are not recognized. In addition con‐
1335 stants can be of the form [base#]n where base is a decimal number be‐
1336 tween two and sixty-four representing the arithmetic base and n is a
1337 number in that base. The digits above 9 are represented by the lower
1338 case letters, the upper case letters, @, and _ respectively. For bases
1339 less than or equal to 36, upper and lower case characters can be used
1340 interchangeably.
1341 An arithmetic expression uses the same syntax, precedence, and associa‐
1343 tivity of expression as the C language. All the C language operators
1344 that apply to floating point quantities can be used. In addition, the
1345 operator ** can be used for exponentiation. It has higher precedence
1346 than multiplication and is left associative. In addition, when the
1347 value of an arithmetic variable or subexpression can be represented as
1348 a long integer, all C language integer arithmetic operations can be
1349 performed. Variables can be referenced by name within an arithmetic
1350 expression without using the parameter expansion syntax. When a vari‐
1351 able is referenced, its value is evaluated as an arithmetic expression.
1352 Any of the following math library functions that are in the C math li‐
1354 brary can be used within an arithmetic expression:
1355 abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos cosh
1357 erf erfc exp exp10 exp2 expm1 fabs fdim finite float floor fma fmax
1358 fmin fmod fpclass fpclassify hypot ilogb int isfinite isgreater is‐
1359 greaterequal isinf isinfinite isless islessequal islessgreater isnan
1360 isnormal issubnormal isunordered iszero j0 j1 jn ldexp lgamma log log10
1361 log1p log2 logb nearbyint nextafter nexttoward pow remainder rint round
1362 scalb scalbn signbit sin sinh sqrt tan tanh tgamma trunc y0 y1 yn
1363 In addition, arithmetic functions can be defined as shell functions
1365 with a variant of the function name syntax,
1366 function .sh.math.name ident ... { list ;}
1368 where name is the function name used in the arithmetic expres‐
1369 sion and each identifier, ident is a name reference to the long
1370 double precision floating point argument. The value of
1371 .sh.value when the function returns is the value of this func‐
1372 tion. User defined functions can take up to 3 arguments and
1373 override C math library functions.
1374 An internal representation of a variable as a double precision floating
1376 point can be specified with the -E [n], -F [n], or -X [n] option of the
1377 typeset special built-in command. The -E option causes the expansion
1378 of the value to be represented using scientific notation when it is ex‐
1379 panded. The optional option argument n defines the number of signifi‐
1380 cant figures. The -F option causes the expansion to be represented as
1381 a floating decimal number when it is expanded. The -X option causes
1382 the expansion to be represented using the %a format defined by ISO
1383 C-99. The optional option argument n defines the number of places af‐
1384 ter the decimal (or radix) point in this case.
1385 An internal integer representation of a variable can be specified with
1387 the -i [n] option of the typeset special built-in command. The op‐
1388 tional option argument n specifies an arithmetic base to be used when
1389 expanding the variable. If you do not specify an arithmetic base, base
1390 10 will be used.
1391 Arithmetic evaluation is performed on the value of each assignment to a
1393 variable with the -E, -F, -X, or -i attribute. Assigning a floating
1394 point number to a variable whose type is an integer causes the frac‐
1395 tional part to be truncated.
1396 Prompting.
1398 When used interactively, the shell prompts with the value of PS1 after
1399 expanding it for parameter expansion, command substitution, and arith‐
1400 metic expansion, before reading a command. In addition, each single !
1401 in the prompt is replaced by the command number. A !! is required to
1402 place ! in the prompt. If at any time a new-line is typed and further
1403 input is needed to complete a command, then the secondary prompt (i.e.,
1404 the value of PS2) is issued.
1405 Conditional Expressions.
1407 A conditional expression is used with the [[ compound command to test
1408 attributes of files and to compare strings. Field splitting and path‐
1409 name expansion are not performed on the words between [[ and ]]. Each
1410 expression can be constructed from one or more of the following unary
1411 or binary expressions:
1412 string Same as -n string below.
1413 -a file
1414 Same as -e below. This is obsolete.
1415 -b file
1416 True if file exists and is a block special file.
1417 -c file
1418 True if file exists and is a character special file.
1419 -d file
1420 True if file exists and is a directory.
1421 -e file
1422 True if file exists.
1423 -f file
1424 True if file exists and is an ordinary file.
1425 -g file
1426 True if file exists and it has its setgid bit set.
1427 -k file
1428 True if file exists and it has its sticky bit set.
1429 -n string
1430 True if length of string is non-zero.
1431 -o ?option
1432 True if option named option is a valid option name.
1433 -o option
1434 True if option named option is on.
1435 -p file
1436 True if file exists and is a fifo special file or a pipe.
1437 -r file
1438 True if file exists and is readable by current process.
1439 -s file
1440 True if file exists and has size greater than zero.
1441 -t fildes
1442 True if file descriptor number fildes is open and associ‐
1443 ated with a terminal device.
1444 -u file
1445 True if file exists and it has its setuid bit set.
1446 -v name
1447 True if variable name is a valid variable name and is
1448 set.
1449 -w file
1450 True if file exists and is writable by current process.
1451 -x file
1452 True if file exists and is executable by current process.
1453 If file exists and is a directory, then true if the cur‐
1454 rent process has permission to search in the directory.
1455 -z string
1456 True if length of string is zero.
1457 -L file
1458 True if file exists and is a symbolic link.
1459 -h file
1460 True if file exists and is a symbolic link.
1461 -N file
1462 True if file exists and the modification time is greater
1463 than the last access time.
1464 -O file
1465 True if file exists and is owned by the effective user ID
1466 of this process.
1467 -G file
1468 True if file exists and its group matches the effective
1469 group ID of this process.
1470 -R name
1471 True if variable name is a name reference.
1472 -S file
1473 True if file exists and is a socket.
1474 file1 -nt file2
1475 True if file1 exists and file2 does not, or file1 is
1476 newer than file2.
1477 file1 -ot file2
1478 True if file2 exists and file1 does not, or file1 is
1479 older than file2.
1480 file1 -ef file2
1481 True if file1 and file2 exist and refer to the same file.
1482 string == pattern
1483 True if string matches pattern. Any part of pattern can
1484 be quoted to cause it to be matched as a string. With a
1485 successful match to a pattern, the .sh.match array vari‐
1486 able will contain the match and subpattern matches.
1487 string = pattern
1488 Same as == above, but is obsolete.
1489 string != pattern
1490 True if string does not match pattern. When the string
1491 matches the pattern the .sh.match array variable will
1492 contain the match and subpattern matches.
1493 string =∼ ere
1494 True if string matches the pattern ∼(E)ere where ere is
1495 an extended regular expression.
1496 string1 < string2
1497 True if string1 comes before string2 based on ASCII value
1498 of their characters.
1499 string1 > string2
1500 True if string1 comes after string2 based on ASCII value
1501 of their characters.
1502 The following obsolete arithmetic comparisons are also permitted:
1504 exp1 -eq exp2
1505 True if exp1 is equal to exp2.
1506 exp1 -ne exp2
1507 True if exp1 is not equal to exp2.
1508 exp1 -lt exp2
1509 True if exp1 is less than exp2.
1510 exp1 -gt exp2
1511 True if exp1 is greater than exp2.
1512 exp1 -le exp2
1513 True if exp1 is less than or equal to exp2.
1514 exp1 -ge exp2
1515 True if exp1 is greater than or equal to exp2.
1516 In each of the above expressions, if file is of the form /dev/fd/n,
1518 where n is an integer, then the test is applied to the open file whose
1519 descriptor number is n. The posix shell option disables this special
1520 handling.
1521 A compound expression can be constructed from these primitives by using
1523 any of the following, listed in decreasing order of precedence:
1524 (expression)
1525 True if expression is true. Used to group expressions.
1526 ! expression
1527 True if expression is false.
1528 expression1 && expression2
1529 True if expression1 and expression2 are both true.
1530 expression1 || expression2
1531 True if either expression1 or expression2 is true.
1532 Input/Output.
1534 Before a command is executed, its input and output may be redirected
1535 using a special notation interpreted by the shell. The following may
1536 appear anywhere in a simple-command or may precede or follow a command
1537 and are not passed on to the invoked command. Command substitution,
1538 parameter expansion, and arithmetic expansion occur before word or
1539 digit is used except as noted below. Pathname expansion occurs only if
1540 the shell is interactive and the pattern matches a single file. Field
1541 splitting is not performed.
1542 In each of the following redirections, if file is of the form
1544 /dev/sctp/host/port, /dev/tcp/host/port, or /dev/udp/host/port, where
1545 host is a hostname or host address, and port is a service given by name
1546 or an integer port number, then the redirection attempts to make a tcp,
1547 sctp or udp connection to the corresponding socket.
1548 No intervening space is allowed between the characters of redirection
1550 operators.
1551 <word Use file word as standard input (file descriptor 0).
1553 >word Use file word as standard output (file descriptor 1). If
1555 the file does not exist then it is created. If the file
1556 exists, and the noclobber option is on, this causes an
1557 error; otherwise, it is truncated to zero length.
1558 >|word Same as >, except that it overrides the noclobber option.
1560 >;word Write output to a temporary file. If the command com‐
1562 pletes successfully rename it to word, otherwise, delete
1563 the temporary file. >;word cannot be used with the exec
1564 and redirect built-ins.
1565 >>word Use file word as standard output. If the file exists,
1567 then output is appended to it (by first seeking to the
1568 end-of-file); otherwise, the file is created.
1569 <>word Open file word for reading and writing as standard out‐
1571 put. If the posix option is active, it defaults to stan‐
1572 dard input instead.
1573 <>;word The same as <>word except that if the command completes
1575 successfully, word is truncated to the offset at command
1576 completion. <>;word cannot be used with the exec and re‐
1577 direct built-ins.
1578 <<[-]word The shell input is read up to a line that is the same as
1580 word after any quoting has been removed, or to an end-of-
1581 file. No parameter expansion, command substitution,
1582 arithmetic expansion or pathname expansion is performed
1583 on word. The resulting document, called a here-document,
1584 becomes the standard input. If any character of word is
1585 quoted, then no interpretation is placed upon the charac‐
1586 ters of the document; otherwise, parameter expansion,
1587 command substitution, and arithmetic expansion occur,
1588 \new-line is ignored, and \ must be used to quote the
1589 characters \, $, `. If - is appended to <<, then all
1590 leading tabs are stripped from word and from the docu‐
1591 ment. If # is appended to <<, then leading spaces and
1592 tabs will be stripped off the first line of the document
1593 and up to an equivalent indentation will be stripped from
1594 the remaining lines and from word. A tab stop is assumed
1595 to occur at every 8 columns for the purposes of determin‐
1596 ing the indentation.
1597 <<<word A short form of here document in which word becomes the
1599 contents of the here-document after any parameter expan‐
1600 sion, command substitution, and arithmetic expansion oc‐
1601 cur.
1602 <&digit The standard input is duplicated from file descriptor
1604 digit (see dup(2)).
1605 >&digit The standard output is duplicated from file descriptor
1607 digit.
1608 <&digit- The file descriptor given by digit is moved to standard
1610 input.
1611 >&digit- The file descriptor given by digit is moved to standard
1613 output.
1614 <&- The standard input is closed.
1616 >&- The standard output is closed.
1618 <&p The input from the co-process is moved to standard input.
1620 >&p The output to the co-process is moved to standard output.
1622 <#((expr)) Evaluate arithmetic expression expr and position file de‐
1624 scriptor 0 to the resulting value bytes from the start of
1625 the file. The variables CUR and EOF evaluate to the cur‐
1626 rent offset and end-of-file offset respectively when
1627 evaluating expr.
1628 >#((offset)) The same as <# except applies to file descriptor 1.
1630 <#pattern Seeks forward to the beginning of the next line contain‐
1632 ing pattern.
1633 <##pattern The same as <# except that the portion of the file that
1635 is skipped is copied to standard output.
1636 If one of the above is preceded by a digit, with no intervening space,
1638 then the file descriptor number referred to is that specified by the
1639 digit (instead of the default 0 or 1). If one of the above, other than
1640 >&- and the ># and <# forms, is preceded by {varname} with no interven‐
1641 ing space, then a file descriptor number > 9 will be selected by the
1642 shell and stored in the variable varname, so it can be read from or
1643 written to with redirections like <& $varname or >& $varname. If >&-
1644 or the any of the ># and <# forms is preceded by {varname} the value of
1645 varname defines the file descriptor to close or position. For example:
1646 ... 2>&1
1648 means file descriptor 2 is to be opened for writing as a duplicate of
1650 file descriptor 1 and
1651 exec {n}<file
1653 means open file named file for reading and store the file descriptor
1655 number in variable n.
1656 A special shorthand redirection operator &>word is available; it is
1658 equivalent to >word 2>&1. It cannot be preceded by any digit or vari‐
1659 able name. This shorthand is disabled if the posix shell option is ac‐
1660 tive.
1661 The order in which redirections are specified is significant. The
1663 shell evaluates each redirection in terms of the (file descriptor,
1664 file) association at the time of evaluation. For example:
1665 ... 1>fname 2>&1
1667 first associates file descriptor 1 with file fname. It then associates
1669 file descriptor 2 with the file associated with file descriptor 1 (i.e.
1670 fname). If the order of redirections were reversed, file descriptor 2
1671 would be associated with the terminal (assuming file descriptor 1 had
1672 been) and then file descriptor 1 would be associated with file fname.
1673 If a command is followed by & and job control is not active, then the
1675 default standard input for the command is the empty file /dev/null.
1676 Otherwise, the environment for the execution of a command contains the
1677 file descriptors of the invoking shell as modified by input/output
1678 specifications.
1679 Environment.
1681 The environment (see environ(7)) is a list of name-value pairs that is
1682 passed to an executed program in the same way as a normal argument
1683 list. The names must be identifiers and the values are character
1684 strings. The shell interacts with the environment in several ways. On
1685 invocation, the shell scans the environment and creates a variable for
1686 each name found, giving it the corresponding value and attributes and
1687 marking it export. Executed commands inherit the environment. If the
1688 user modifies the values of these variables or creates new ones, using
1689 the export or typeset -x commands, they become part of the environment.
1690 The environment seen by any executed command is thus composed of any
1691 name-value pairs originally inherited by the shell, whose values may be
1692 modified by the current shell, plus any additions which must be noted
1693 in export or typeset -x commands.
1694 The environment for any simple-command or function may be augmented by
1696 prefixing it with one or more variable assignments. A variable assign‐
1697 ment argument is a word of the form identifier=value. Thus:
1698 TERM=450 cmd args and
1700 (export TERM; TERM=450; cmd args)
1701 are equivalent (as far as the above execution of cmd is concerned ex‐
1703 cept for special built-in commands listed below - those that are marked
1704 with †).
1705 If the obsolete -k option is set, all variable assignment arguments are
1707 placed in the environment, even if they occur after the command name.
1708 The following first prints a=b c and then c:
1709 echo a=b c
1711 set -k
1712 echo a=b c
1713 This feature is intended for use with scripts written for early ver‐
1715 sions of the shell and its use in new scripts is strongly discouraged.
1716 It is likely to disappear someday.
1717 Functions.
1719 For historical reasons, there are two ways to define functions, the
1720 name() syntax and the function name syntax, described in the Commands
1721 section above. Shell functions are read in and stored internally.
1722 Alias names are resolved when the function is read. Functions are exe‐
1723 cuted like commands with the arguments passed as positional parameters.
1724 (See Execution below.)
1725 Functions defined by the function name syntax and called by name exe‐
1727 cute in the same process as the caller and share all files and present
1728 working directory with the caller. Traps caught by the caller are re‐
1729 set to their default action inside the function. A trap condition that
1730 is not caught or ignored by the function causes the function to termi‐
1731 nate and the condition to be passed on to the caller. A trap on EXIT
1732 set inside a function is executed in the environment of the caller af‐
1733 ter the function completes. Ordinarily, variables are shared between
1734 the calling program and the function. However, the typeset special
1735 built-in command used within a function defines local variables whose
1736 scope includes the current function. They can be passed to functions
1737 that they call in the variable assignment list that precedes the call
1738 or as arguments passed as name references. Errors within functions re‐
1739 turn control to the caller.
1740 Functions defined with the name() syntax and functions defined with the
1742 function name syntax that are invoked with the . special built-in are
1743 executed in the caller's environment and share all variables and traps
1744 with the caller. Errors within these function executions cause the
1745 script that contains them to abort.
1746 The special built-in command return is used to return from function
1748 calls.
1749 Function names can be listed with the -f or +f option of the typeset
1751 special built-in command. The text of functions, when available, will
1752 also be listed with -f. Functions can be undefined with the -f option
1753 of the unset special built-in command.
1754 Ordinarily, functions are unset when the shell executes a shell script.
1756 Functions that need to be defined across separate invocations of the
1757 shell should be placed in a directory and the FPATH variable should
1758 contain the name of this directory. They may also be specified in the
1759 ENV file.
1760 Discipline Functions.
1762 Each variable can have zero or more discipline functions associated
1763 with it. The shell initially understands the discipline names get,
1764 set, append, and unset but can be added when defining new types. On
1765 most systems others can be added at run time via the C programming in‐
1766 terface extension provided by the builtin built-in utility. If the get
1767 discipline is defined for a variable, it is invoked whenever the given
1768 variable is referenced. If the variable .sh.value is assigned a value
1769 inside the discipline function, the referenced variable will evaluate
1770 to this value instead. If the set discipline is defined for a vari‐
1771 able, it is invoked whenever the given variable is assigned a value.
1772 If the append discipline is defined for a variable, it is invoked when‐
1773 ever a value is appended to the given variable. The variable .sh.value
1774 is given the value of the variable before invoking the discipline, and
1775 the variable will be assigned the value of .sh.value after the disci‐
1776 pline completes. If .sh.value is unset inside the discipline, then
1777 that value is unchanged. If the unset discipline is defined for a
1778 variable, it is invoked whenever the given variable is unset.
1779 The variable .sh.name contains the name of the variable for which the
1781 discipline function is called, .sh.subscript is the subscript of the
1782 variable, and .sh.value will contain the value being assigned inside
1783 the set discipline function. The variable _ is a reference to the
1784 variable including the subscript if any. For the set discipline,
1785 changing .sh.value will change the value that gets assigned. Finally,
1786 the expansion ${var.name}, when name is the name of a discipline, and
1787 there is no variable of this name, is equivalent to the command substi‐
1788 tution ${ var.name;}.
1789 Name Spaces.
1792 Commands and functions that are executed as part of the list of a name‐
1793 space command that modify variables or create new ones, create a new
1794 variable whose name is the name of the name space as given by identi‐
1795 fier preceded by .. When a variable whose name is name is referenced,
1796 it is first searched for using .identifier.name. Similarly, a function
1797 defined by a command in the namespace list is created using the name
1798 space name preceded by a ..
1799 When the list of a namespace command contains a namespace command, the
1801 names of variables and functions that are created consist of the vari‐
1802 able or function name preceded by the list of identifiers each preceded
1803 by ..
1804 Outside of a name space, a variable or function created inside a name
1806 space can be referenced by preceding it with the name space name.
1807 By default, variables starting with .sh are in the sh name space.
1809 Type Variables.
1812 Typed variables provide a way to create data structure and objects. A
1813 type can be defined either by a shared library, by the enum built-in
1814 command described below, or by using the new -T option of the typeset
1815 built-in command. With the -T option of typeset, the type name, speci‐
1816 fied as an option argument to -T, is set with a compound variable as‐
1817 signment that defines the type. Function definitions can appear inside
1818 the compound variable assignment and these become discipline functions
1819 for this type and can be invoked or redefined by each instance of the
1820 type. The function name create is treated specially. It is invoked
1821 for each instance of the type that is created but is not inherited and
1822 cannot be redefined for each instance.
1823 When a type is defined a special built-in command of that name is
1825 added. These built-ins are declaration commands and follow the same
1826 expansion rules as the built-in commands described below that are
1827 marked with a ‡ symbol. These commands can subsequently be used inside
1828 further type definitions. The man page for these commands can be gen‐
1829 erated by using the --man option or any of the other -- options de‐
1830 scribed with getopts. The -r, -a, -A, -h, and -S options of typeset
1831 are permitted with each of these new built-ins.
1832 An instance of a type is created by invoking the type name followed by
1834 one or more instance names. Each instance of the type is initialized
1835 with a copy of the subvariables except for subvariables that are de‐
1836 fined with the -S option. Variables defined with the -S are shared by
1837 all instances of the type. Each instance can change the value of any
1838 subvariable and can also define new discipline functions of the same
1839 names as those defined by the type definition as well as any standard
1840 discipline names. No additional subvariables can be defined for any
1841 instance.
1842 When defining a type, if the value of a subvariable is not set and the
1844 -r attribute is specified, it causes the subvariable to be a required
1845 subvariable. Whenever an instance of a type is created, all required
1846 subvariables must be specified. These subvariables become read-only in
1847 each instance.
1848 When unset is invoked on a subvariable within a type, and the -r attri‐
1850 bute has not been specified for this field, the value is reset to the
1851 default value associative with the type. Invoking unset on a type in‐
1852 stance not contained within another type deletes all subvariables and
1853 the variable itself.
1854 A type definition can be derived from another type definition by defin‐
1856 ing the first subvariable name as _ and defining its type as the base
1857 type. Any remaining definitions will be additions and modifications
1858 that apply to the new type. If the new type name is the same as that
1859 of the base type, the type will be replaced and the original type will
1860 no longer be accessible.
1861 The typeset command with the -T and no option argument or operands will
1863 write all the type definitions to standard output in a form that can be
1864 read in to create all they types.
1865 Jobs.
1867 If the monitor option of the set command is turned on, an interactive
1868 shell associates a job with each pipeline. It keeps a table of current
1869 jobs, printed by the jobs command, and assigns them small integer num‐
1870 bers. When a job is started asynchronously with &, the shell prints a
1871 line which looks like:
1872 [1] 1234
1874 indicating that the job which was started asynchronously was job number
1876 1 and had one (top-level) process, whose process ID was 1234.
1877 This paragraph and the next require features that are not in all ver‐
1879 sions of UNIX and may not apply. If you are running a job and wish to
1880 do something else you may hit the key ^Z (control-Z) which sends a STOP
1881 signal to the current job. The shell will then normally indicate that
1882 the job has been `Stopped', and print another prompt. You can then ma‐
1883 nipulate the state of this job, putting it in the background with the
1884 bg command, or run some other commands and then eventually bring the
1885 job back into the foreground with the foreground command fg. A ^Z
1886 takes effect immediately and is like an interrupt in that pending out‐
1887 put and unread input are discarded when it is typed.
1888 A job being run in the background will stop if it tries to read from
1890 the terminal. Background jobs are normally allowed to produce output,
1891 but this can be disabled by giving the command stty tostop. If you set
1892 this tty option, then background jobs will stop when they try to pro‐
1893 duce output like they do when they try to read input.
1894 There are several ways to refer to jobs in the shell. A job can be re‐
1896 ferred to by the process ID of any process of the job or by one of the
1897 following:
1898 %number
1899 The job with the given number.
1900 %string
1901 Any job whose command line begins with string.
1902 %?string
1903 Any job whose command line contains string.
1904 %% Current job.
1905 %+ Equivalent to %%.
1906 %- Previous job.
1907 The shell learns immediately whenever a process changes state. It nor‐
1909 mally informs you whenever a job becomes blocked so that no further
1910 progress is possible, but only just before it prints a prompt. This is
1911 done so that it does not otherwise disturb your work. The notify op‐
1912 tion of the set command causes the shell to print these job change mes‐
1913 sages as soon as they occur.
1914 When the monitor option is on, each background job that completes trig‐
1916 gers any trap set for CHLD.
1917 When you try to leave the shell while jobs are running or stopped, you
1919 will be warned that `You have stopped(running) jobs.' You may use the
1920 jobs command to see what they are. If you immediately try to exit
1921 again, the shell will not warn you a second time, and the stopped jobs
1922 will be terminated. When a login shell receives a HUP signal, it sends
1923 a HUP signal to each job that has not been disowned with the disown
1924 built-in command described below.
1925 Signals.
1927 The INT and QUIT signals for an invoked command are ignored if the com‐
1928 mand is followed by & and the monitor option is not active. Otherwise,
1929 signals have the values inherited by the shell from its parent (but see
1930 also the trap built-in command below).
1931 Execution.
1933 Each time a command is read, the above expansions and substitutions are
1934 carried out. If the command name matches one of the Special Built-in
1935 Commands listed below, it is executed within the current shell process.
1936 Next, the command name is checked to see if it matches a user defined
1937 function. If it does, the positional parameters are saved and then re‐
1938 set to the arguments of the function call. A function is also executed
1939 in the current shell process. When the function completes or issues a
1940 return, the positional parameter list is restored. For functions de‐
1941 fined with the function name syntax, any trap set on EXIT within the
1942 function is executed. The exit value of a function is the value of the
1943 last command executed. If a command name is not a special built-in
1944 command or a user defined function, but it is one of the built-in com‐
1945 mands listed below, it is executed in the current shell process.
1946 The shell variables PATH followed by the variable FPATH defines the
1948 list of directories to search for the command name. Alternative direc‐
1949 tory names are separated by a colon (:). The default path is the value
1950 that was output by getconf PATH at the time ksh was compiled. The cur‐
1951 rent directory can be specified by two or more adjacent colons, or by a
1952 colon at the beginning or end of the path list. If the command name
1953 contains a /, then the search path is not used. Otherwise, each direc‐
1954 tory in the list of directories defined by PATH and FPATH is checked in
1955 order. If the directory being searched is contained in FPATH and con‐
1956 tains a file whose name matches the command being searched, then this
1957 file is loaded into the current shell environment as if it were the ar‐
1958 gument to the . command except that only preset aliases are expanded,
1959 and a function of the given name is executed as described above.
1960 If this directory is not in FPATH the shell first determines whether
1962 there is a built-in version of a command corresponding to a given path‐
1963 name and if so it is invoked in the current process. If no built-in is
1964 found, the shell checks for a file named .paths in this directory. If
1965 found and there is a line of the form FPATH=path where path names an
1966 existing directory then that directory is searched immediately after
1967 the current directory as if it were found in the FPATH variable. If
1968 path does not begin with /, it is checked for relative to the directory
1969 being searched.
1970 The .paths file is then checked for a line of the form PLUGIN_LIB=lib‐
1972 name [ : libname ] ... . Each library named by libname will be
1973 searched for as if it were an option argument to builtin -f, and if it
1974 contains a built-in of the specified name this will be executed instead
1975 of a command by this name. Any built-in loaded from a library found
1976 this way will be associated with the directory containing the .paths
1977 file so it will only execute if not found in an earlier directory.
1978 Finally, the directory will be checked for a file of the given name.
1980 If the file has execute permission but is not an a.out file, it is as‐
1981 sumed to be a file containing shell commands. A separate shell is
1982 spawned to read it. All non-exported variables are removed in this
1983 case. If the shell command file doesn't have read permission, or if
1984 the setuid and/or setgid bits are set on the file, then the shell exe‐
1985 cutes an agent whose job it is to set up the permissions and execute
1986 the shell with the shell command file passed down as an open file. If
1987 the .paths contains a line of the form name=value in the first or sec‐
1988 ond line, then the environment variable name is modified by prepending
1989 the directory specified by value to the directory list. If value is
1990 not an absolute directory, then it specifies a directory relative to
1991 the directory that the executable was found. If the environment vari‐
1992 able name does not already exist it will be added to the environment
1993 list for the specified command. A parenthesized command is executed in
1994 a subshell without removing non-exported variables.
1995 Command Re-entry.
1997 The text of the last HISTSIZE (default 512) commands entered from a
1998 terminal device is saved in a history file. The file $HOME/.sh_history
1999 is used if the HISTFILE variable is not set or if the file it names is
2000 not writable. A shell can access the commands of all interactive
2001 shells which use the same named HISTFILE. The built-in command hist is
2002 used to list or edit a portion of this file. The portion of the file
2003 to be edited or listed can be selected by number or by giving the first
2004 character or characters of the command. A single command or range of
2005 commands can be specified. If you do not specify an editor program as
2006 an argument to hist then the value of the variable HISTEDIT is used.
2007 If HISTEDIT is unset, the obsolete variable FCEDIT is used. If FCEDIT
2008 is not defined, then /bin/ed is used. The edited command(s) is printed
2009 and re-executed upon leaving the editor unless you quit without writ‐
2010 ing. The -s option (and in obsolete versions, the editor name -) is
2011 used to skip the editing phase and to re-execute the command. In this
2012 case a substitution parameter of the form old=new can be used to modify
2013 the command before execution. For example, with the preset alias r,
2014 which is aliased to ′hist -s′, typing `r bad=good c' will re-execute
2015 the most recent command which starts with the letter c, replacing the
2016 first occurrence of the string bad with the string good.
2017 History Expansion.
2019 History expansions introduce words from the history list into the input
2020 stream, making it easy to repeat commands, repeat arguments of a previ‐
2021 ous command in the current command, or fix typos in the previous com‐
2022 mand. The history expansion facility is an alternative to history con‐
2023 trol via the fc or hist built-in command. To enable it, turn on the -H
2024 or histexpand option using the set command (see Built-in Commands be‐
2025 low).
2026 History expansions begin with the character !. They may begin anywhere
2028 in the input. The ! may be preceded by a \ or enclosed in single
2029 quotes to prevent its special meaning. A ! is also passed unchanged
2030 when it is followed by a space, tab, newline, = or (. History expan‐
2031 sions do not nest. They are parsed separately before the shell parser
2032 is invoked, so they can override shell grammar rules.
2033 By default, the expanded version of any line that contains a history
2035 expansion is printed, added to the history, and then immediately exe‐
2036 cuted. History expansions are never added to the history themselves,
2037 regardless of whether they succeed or fail due to an error. Normally,
2038 this means that a command line with an erroneous history expansion is
2039 lost and needs to be retyped from scratch, but if the histreedit shell
2040 option is turned on and a line editor is active (see In-line Editing
2041 Options below), the erroneous line is pre-filled into the next prompt's
2042 input buffer for correcting. The histverify option causes the same to
2043 be done for the results of successful history expansions, allowing ver‐
2044 ification and editing before execution.
2045 A history expansion may have an event specification, which indicates
2047 the event from which words are to be taken, a word designator, which
2048 selects particular words from the chosen event, and/or a modifier,
2049 which manipulates the selected words.
2050 An event specification can be:
2052 n A number, referring to a particular event.
2054 -n An offset, referring to the event n before the current
2055 event.
2056 # The current event.
2057 ! The previous event (equivalent to -1).
2058 s The most recent event whose first word begins with the
2059 string s.
2060 ?s? The most recent event which contains the string s. The
2061 second ? can be omitted if it is immediately followed by a
2062 newline.
2063 For example, consider this bit of someone's history list as might be
2065 output by the hist -l command:
2066 9 nroff -man wumpus.man
2068 10 cp wumpus.man wumpus.man.old
2069 11 vi wumpus.man
2070 12 diff wumpus.man.old wumpus.man
2071 The commands are shown with their event numbers. The current event,
2073 which we haven't typed in yet, is event 13. !11 and !-2 refer to event
2074 11. !! refers to the previous event, 12. !! can be abbreviated ! if
2075 it is followed by : (see below). !n refers to event 9, which begins
2076 with n. !?old? also refers to event 12, which contains old. Without
2077 word designators or modifiers, history references simply expand to the
2078 entire event, so we might type !cp to redo the copy command or !!|more
2079 if the diff output scrolled off the top of the screen.
2080 To select words from an event, the event specification can be followed
2082 by a : and a designator for the desired words. The words of an input
2083 line are numbered from 0, the first word (usually the command name) be‐
2084 ing 0, the second word (first argument) being 1, etc. The basic word
2085 designators are:
2086 0 The first word (command name).
2088 n The nth argument.
2089 ^ The first argument, equivalent to 1.
2090 $ The last argument.
2091 % The word matched by the most recent ?s? search.
2092 x-y A range of words.
2093 -y Equivalent to 0-y.
2094 * Equivalent to ^-$, but returns nothing if the event con‐
2095 tains only 1 word.
2096 x* Equivalent to x-$.
2097 x- Equivalent to x*, but omitting the last word ($).
2098 Selected words are inserted into the command line separated by single
2100 blanks. For example, the diff command in the previous example might
2101 have been typed as diff !!:1.old !!:1 (using :1 to select the first ar‐
2102 gument from the previous event) or diff !-2:2 !-2:1 to select and swap
2103 the arguments from the cp command. If we didn't care about the order
2104 of the diff, we might have said diff !-2:1-2 or simply diff !-2:*. The
2105 cp command might have been written cp wumpus.man !#:1.old, using # to
2106 refer to the current event. !n:- hurkle.man would reuse the first two
2107 words from the nroff command to say nroff -man hurkle.man.
2108 The : separating the event specification from the word designator can
2110 be omitted if the argument selector begins with a ^, $, *, % or -. For
2111 example, our diff command might have been diff !!^.old !!^ or, equiva‐
2112 lently, diff !!$.old !!$. However, if !! is abbreviated !, an argument
2113 selector beginning with - will be interpreted as an event specifica‐
2114 tion.
2115 The word(s) in a history reference can be edited by following them with
2117 one or more modifiers, each preceded by a colon (:):
2118 h Remove a trailing pathname component, leaving the head.
2120 t Remove all leading pathname components, leaving the tail.
2121 r Remove a filename extension .xxx, leaving the root name.
2122 e Remove all but the extension.
2123 s/l/r/ Substitute l for r. l is simply a string like r, not a
2124 regular expression as in the eponymous ed(1) command. Any
2125 character may be used as the delimiter in place of /; a \
2126 can be used to quote the delimiter inside l and r. The
2127 character & in the r is replaced by l; \ also quotes &. If
2128 l is empty, the l from the previous substitution is used,
2129 or if there is none, the s from the most recent ?s? search.
2130 The trailing delimiter may be omitted if it is immediately
2131 followed by a newline.
2132 & Repeat the previous substitution.
2133 g Global substitution, for example :gs/foo/bar/ or :g&. Ap‐
2134 plies the s or & modifier to the entire command line.
2135 a Same as g.
2136 p Print the new command line but do not execute it.
2137 q Quote the expanded words, preventing further expansions.
2138 x Like q, but break into words at blanks, tabs and newlines.
2139 Modifiers are applied to only the first modifiable word (unless g or a
2141 is used). It is an error for no word to be modifiable.
2142 For example, the diff command might have been written as diff wum‐
2144 pus.man.old !#^:r, using :r to remove .old from the first argument on
2145 the same line (!#^). We might follow mail -s "I forgot my password"
2146 rot with !:s/rot/root to correct the spelling of root.
2147 History expansions also occur when an input line begins with ^. When
2149 it is the first character on an input line, it is an abbreviation of
2150 !:s^. Thus we might have said ^rot^root to make the spelling correc‐
2151 tion in the previous example. This is the only history expansion that
2152 does not explicitly begin with !.
2153 If a word on a command line begins with the history comment character
2155 #, history expansion is ignored for the rest of that line. This usu‐
2156 ally causes the shell parser (which uses the same character to signal a
2157 comment) to treat the rest of the line as a comment as well, but as
2158 history expansion is parsed separately from the shell grammar and with
2159 different rules, this cannot be guaranteed in all cases. If the his‐
2160 tory comment character is changed, the shell grammar comment character
2161 does not change along with it.
2162 The three characters used to signal history expansion can be changed
2164 using the histchars shell variable; see Shell Variables above.
2165 In-line Editing Options.
2167 Normally, each command line entered from a terminal device is simply
2168 typed followed by a new-line (`RETURN' or `LINE FEED'). If either the
2169 emacs, gmacs, or vi option is active, the user can edit the command
2170 line. To be in either of these edit modes, set the corresponding op‐
2171 tion. An editing option is automatically selected each time the VISUAL
2172 or EDITOR variable is assigned a value matching any of these editor
2173 names; for details, see Shell Variables above under VISUAL.
2174 The editing features require that the user's terminal accept `RETURN'
2176 as carriage return without line feed and that a space (` ') must over‐
2177 write the current character on the screen.
2178 Unless the multiline option is on, the editing modes implement a con‐
2180 cept where the user is looking through a window at the current line.
2181 The window width is the value of COLUMNS if it is defined, otherwise
2182 80. If the window width is too small to display the prompt and leave
2183 at least 8 columns to enter input, the prompt is truncated from the
2184 left. If the line is longer than the window width minus two, a mark is
2185 displayed at the end of the window to notify the user. As the cursor
2186 moves and reaches the window boundaries, the window will be centered
2187 about the cursor. The mark is a > (<, *) if the line extends on the
2188 right (left, both) side(s) of the window.
2189 The search commands in each edit mode provide access to the history
2191 file. Only strings are matched, not patterns, although a leading ^ in
2192 the string restricts the match to begin at the first character in the
2193 line.
2194 Each of the edit modes has an operation to list the files or commands
2196 that match a partially entered word. When applied to the first word on
2197 the line, or the first word after a ;, |, &, or (, and the word does
2198 not begin with ∼ or contain a /, the list of aliases, functions, and
2199 executable commands defined by the PATH variable that could match the
2200 partial word is displayed. Otherwise, the list of files that match the
2201 given word is displayed. If the partially entered word does not con‐
2202 tain any file expansion characters, a * is appended before generating
2203 these lists. After displaying the generated list, the input line is
2204 redrawn. These operations are called command name listing and file
2205 name listing, respectively. There are additional operations, referred
2206 to as command name completion and file name completion, which compute
2207 the list of matching commands or files, but instead of printing the
2208 list, replace the current word with a complete or partial match. For
2209 file name completion, if the match is unique, a / is appended if the
2210 file is a directory and a space is appended if the file is not a direc‐
2211 tory. Otherwise, the longest common prefix for all the matching files
2212 replaces the word. For command name completion, only the portion of
2213 the file names after the last / are used to find the longest command
2214 prefix. If only a single name matches this prefix, then the word is
2215 replaced with the command name followed by a space. When using a tab
2216 for completion that does not yield a unique match, a subsequent tab
2217 will provide a numbered list of matching alternatives. A specific se‐
2218 lection can be made by entering the selection number followed by a tab.
2219 Neither completion nor listing operations are attempted before the
2220 first character in a line.
2221 Key Bindings.
2223 The KEYBD trap can be used to intercept keys as they are typed and
2224 change the characters that are actually seen by the shell. This trap
2225 is executed after each character (or sequence of characters when the
2226 first character is ESC) is entered while reading from a terminal. The
2227 variable .sh.edchar contains the character or character sequence which
2228 generated the trap. Changing the value of .sh.edchar in the trap ac‐
2229 tion causes the shell to behave as if the new value were entered from
2230 the keyboard rather than the original value.
2231 The variable .sh.edcol is set to the input column number of the cursor
2233 at the time of the input. The variable .sh.edmode is set to ESC when
2234 in vi input mode (see below) and set to the empty string otherwise.
2235 Prepending ${.sh.editmode} to a value assigned to .sh.edchar will cause
2236 the shell to change to control mode if it is not already in this mode.
2237 This trap is not invoked for characters entered as arguments to editing
2239 directives, or while reading input for a character search.
2240 Emacs Editing Mode.
2242 This mode is entered by enabling either the emacs or gmacs option. The
2243 only difference between these two modes is the way they handle ^T. To
2244 edit, the user moves the cursor to the point needing correction and
2245 then inserts or deletes characters or words as needed. All the editing
2246 commands are control characters or escape sequences. The notation for
2247 control characters is caret (^) followed by the character. For exam‐
2248 ple, ^F is the notation for control F. This is entered by depressing
2249 `f' while holding down the `CTRL' (control) key. The `SHIFT' key is
2250 not depressed. (The notation ^? indicates the DEL (delete) key.)
2251 The notation for escape sequences is M- followed by a character. For
2253 example, M-f (pronounced Meta f) is entered by depressing ESC (ASCII
2254 033) followed by `f'. (M-F would be the notation for ESC followed by
2255 `SHIFT' (capital) `F'.)
2256 All edit commands operate from any place on the line (not just at the
2258 beginning). Neither the `RETURN' nor the `LINE FEED' key is entered
2259 after edit commands except when noted.
2260 The M-[ multi-character commands below are DEC VT220 escape sequences
2262 generated by special keys on standard PC keyboards, such as the arrow
2263 keys. You could type them directly but they are meant to recognize the
2264 keys in question, which are indicated in parentheses.
2265 ^F Move cursor forward (right) one character.
2267 M-[C (Right arrow) Same as ^F.
2268 M-f Move cursor forward one word. (The emacs editor's idea of a
2269 word is a string of characters consisting of only letters,
2270 digits and underscores.)
2271 M-[1;3C (Alt-Right arrow) Same as M-f.
2272 M-[1;5C (Ctrl-Right arrow) Same as M-f.
2273 M-[1;9C (iTerm2 Alt-Right arrow) Same as M-f.
2274 ^B Move cursor backward (left) one character.
2275 M-[D (Left arrow) Same as ^B.
2276 M-b Move cursor backward one word.
2277 M-[1;3D (Alt-Left arrow) Same as M-b.
2278 M-[1;5D (Ctrl-Left arrow) Same as M-b.
2279 M-[1;9D (iTerm2 Alt-Left arrow) Same as M-b.
2280 ^A Move cursor to start of line.
2281 M-[H (Home) Same as ^A.
2282 M-[1~ Same as ^A.
2283 M-[7~ Same as ^A.
2284 ^E Move cursor to end of line.
2285 M-[F (End) Same as ^E.
2286 M-[4~ Same as ^E.
2287 M-[8~ Same as ^E.
2288 M-[Y Same as ^E.
2289 M-OA (Up Arrow) Same as M-[A.
2290 M-OB (Down Arrow) Same as M-[B.
2291 M-OC (Right Arrow) Same as M-[C.
2292 M-OD (Left Arrow) Same as M-[D.
2293 M-O5C (Ctrl-Right Arrow) Same as M-f.
2294 M-O5D (Ctrl-Left Arrow) Same as M-b.
2295 ^]char Move cursor forward to character char on current line.
2296 M-^]char Move cursor backward to character char on current line.
2297 ^X^X Interchange the cursor and mark.
2298 erase (User defined erase character as defined by the stty(1) com‐
2299 mand, usually ^H.) Delete previous character.
2300 lnext (User defined literal next character as defined by the
2301 stty(1) command, or ^V if not defined.) Removes the next
2302 character's editing features (if any).
2303 ^D Delete current character.
2304 M-[3~ (Forward delete) Same as ^D.
2305 M-d Delete current word.
2306 M-[3;5~ (Ctrl-Delete) Same as M-d.
2307 M-^H (Meta-backspace) Delete previous word.
2308 M-h Delete previous word.
2309 M-^? (Meta-DEL) Delete previous word (if your interrupt character
2310 is ^? (DEL, the default) then this command will not work).
2311 ^T Transpose current character with previous character and ad‐
2312 vance the cursor in emacs mode. Transpose two previous char‐
2313 acters in gmacs mode.
2314 ^C Capitalize current character.
2315 M-c Capitalize current word.
2316 M-l Change the current word to lower case.
2317 ^K Delete from the cursor to the end of the line. If preceded
2318 by a numerical parameter whose value is less than the current
2319 cursor position, then delete from given position up to the
2320 cursor. If preceded by a numerical parameter whose value is
2321 greater than the current cursor position, then delete from
2322 cursor up to given cursor position.
2323 ^W Kill from the cursor to the mark.
2324 M-p Push the region from the cursor to the mark on the stack.
2325 kill (User defined kill character as defined by the stty(1) com‐
2326 mand, usually ^U.) Kill the entire current line. If two
2327 kill characters are entered in succession, all kill charac‐
2328 ters from then on cause a line feed (useful when using paper
2329 terminals). A subsequent pair of kill characters undoes this
2330 change.
2331 ^Y Restore last item removed from line. (Yank item back to the
2332 line.)
2333 ^X^E Return the command hist -e ${VISUAL:-${EDITOR:-vi}} in the
2334 input buffer to call a full editor — vi by default — on the
2335 current command line.
2336 ^L Line feed and print current line.
2337 M-^L Clear the screen.
2338 ^@ (Null character) Set mark.
2339 M-space (Meta space) Set mark.
2340 ^J (New line) Execute the current line.
2341 ^M (Return) Execute the current line.
2342 eof End-of-file character, normally ^D, is processed as an End-
2343 of-file only if the current line is empty.
2344 ^P Fetch previous command. Each time ^P is entered the previous
2345 command back in time is accessed. Moves back one line when
2346 not on the first line of a multi-line command.
2347 M-[A (Up arrow) If the cursor is at the end of the line, it is
2348 equivalent to ^R with string set to the contents of the cur‐
2349 rent line. Otherwise, it is equivalent to ^P.
2350 M-< Fetch the least recent (oldest) history line.
2351 M-> Fetch the most recent (youngest) history line.
2352 ^N Fetch next command line. Each time ^N is entered the next
2353 command line forward in time is accessed.
2354 M-[B (Down arrow) Equivalent to ^N.
2355 ^Rstring Reverse search history for a previous command line containing
2356 string. If a parameter of zero is given, the search is for‐
2357 ward. String is terminated by a `RETURN' or `NEW LINE'. If
2358 string is preceded by a ^, the matched line must begin with
2359 string. If string is omitted, then the next command line
2360 containing the most recent string is accessed. In this case
2361 a parameter of zero reverses the direction of the search.
2362 ^G Exit reverse search mode.
2363 ^O Operate - Execute the current line and fetch the next line
2364 relative to current line from the history file.
2365 M-digits (Escape) Define numeric parameter, the digits are taken as a
2366 parameter to the next command. The commands that accept a
2367 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
2368 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l, M-^H, and the
2369 arrow keys and forward-delete key.
2370 M-letter Soft-key - Your alias list is searched for an alias by the
2371 name _letter and if an alias of this name is defined, its
2372 value will be inserted on the input queue. The letter must
2373 not be one of the above meta-functions.
2374 M-[letter Soft-key - Your alias list is searched for an alias by the
2375 name __letter and if an alias of this name is defined, its
2376 value will be inserted on the input queue. This can be used
2377 to program function keys on many terminals.
2378 M-. The last word of the previous command is inserted on the
2379 line. If preceded by a numeric parameter, the value of this
2380 parameter determines which word to insert rather than the
2381 last word.
2382 M-_ Same as M-..
2383 M-* Attempt pathname expansion on the current word. An asterisk
2384 is appended if the word doesn't match any file or contain any
2385 special pattern characters.
2386 M-ESC Command or file name completion as described above.
2387 ^I tab Attempts command or file name completion as described above.
2388 If a partial completion occurs, repeating this will behave as
2389 if M-= were entered. If no match is found or entered after
2390 space, a tab is inserted.
2391 M-= If not preceded by a numeric parameter, it generates the list
2392 of matching commands or file names as described above. Oth‐
2393 erwise, the word under the cursor is replaced by the item
2394 corresponding to the value of the numeric parameter from the
2395 most recently generated command or file list. If the cursor
2396 is not on a word, it is inserted instead.
2397 ^U Multiply parameter of next command by 4.
2398 \ If the backslashctrl shell option is on (which is the default
2399 setting), this escapes the next character. Editing charac‐
2400 ters, the user's erase, kill and interrupt (normally ^C)
2401 characters may be entered in a command line or in a search
2402 string if preceded by a \. The \ removes the next charac‐
2403 ter's editing features (if any). See also lnext which is not
2404 subject to any shell option.
2405 M-^V Display version of the shell.
2406 M-[2~ (Insert) Escape the next character.
2407 M-# If the line does not begin with a #, a # is inserted at the
2408 beginning of the line and after each new-line, and the line
2409 is entered. This causes a comment to be inserted in the his‐
2410 tory file. If the line begins with a #, the # is deleted and
2411 one # after each new-line is also deleted.
2412 Vi Editing Mode.
2414 There are two typing modes. Initially, when you enter a command you
2415 are in the input mode. To edit, the user enters control mode by typing
2416 ESC (033) and moves the cursor to the point needing correction and then
2417 inserts or deletes characters or words as needed. Most control com‐
2418 mands accept an optional repeat count prior to the command.
2419 The notation for control characters used below is ^ followed by a char‐
2421 acter. For instance, ^H is entered by holding down the Control key and
2422 pressing H. ^[ (Control+[) is equivalent to the ESC key. The notation
2423 for escape sequences is ^[ followed by one or more characters.
2424 The ^[[ (ESC [) multi-character commands below are DEC VT220 escape se‐
2426 quences generated by special keys on standard PC keyboards, such as the
2427 arrow keys, which are indicated in parentheses. When in input mode,
2428 these keys will switch you to control mode before performing the asso‐
2429 ciated action. These sequences can use preceding repeat count parame‐
2430 ters, but only when the ^[ and the subsequent [ are entered into the
2431 input buffer at the same time, such as when pressing one of those keys.
2432 Input Edit Commands
2434 By default the editor is in input mode.
2435 erase (User defined erase character as defined by the
2437 stty(1) command, usually ^H or #.) Delete previous
2438 character.
2439 ^W Delete the previous blank separated word.
2440 eof As the first character of the line causes the shell to
2441 terminate unless the ignoreeof option is set. Other‐
2442 wise this character is ignored.
2443 lnext (User defined literal next character as defined by the
2444 stty(1) or ^V if not defined.) Removes the next char‐
2445 acter's editing features (if any).
2446 \ If the backslashctrl shell option is on (which is the
2447 default setting), this escapes the next erase or kill
2448 character.
2449 ^I tab Attempts command or file name completion as described
2450 above and returns to input mode. If a partial comple‐
2451 tion occurs, repeating this will behave as if = were
2452 entered from control mode. If no match is found or
2453 entered after space, a tab is inserted.
2454 Motion Edit Commands
2456 These commands will move the cursor.
2457 [count]l Cursor forward (right) one character.
2459 [count]^[[C
2460 (Right arrow) Same as l.
2461 [count]w Cursor forward one alphanumeric word.
2462 [count]W Cursor to the beginning of the next word that follows
2463 a blank.
2464 [count]e Cursor to end of word.
2465 [count]E Cursor to end of the current blank delimited word.
2466 [count]h Cursor backward (left) one character.
2467 [count]^[[D
2468 (Left arrow) Same as h.
2469 [count]b Cursor backward one word.
2470 [count]B Cursor to preceding blank separated word.
2471 [count]| Cursor to column count.
2472 [count]fc Find the next character c in the current line.
2473 [count]Fc Find the previous character c in the current line.
2474 [count]tc Equivalent to f followed by h.
2475 [count]Tc Equivalent to F followed by l.
2476 [count]; Repeats count times, the last single character find
2477 command, f, F, t, or T.
2478 [count], Reverses the last single character find command count
2479 times.
2480 0 Cursor to start of line.
2481 ^[[H (Home) Same as 0.
2482 ^[[1~ Same as 0.
2483 ^[[7~ Same as 0.
2484 ^[[1;3D (Alt-Left arrow) Same as b.
2485 ^[[1;5D (Ctrl-Left arrow) Same as b.
2486 ^[[1;9D (iTerm2 Alt-Left arrow) Same as b.
2487 ^[[1;3C (Alt-Right arrow) Same as w.
2488 ^[[1;5C (Ctrl-Right arrow) Same as w.
2489 ^[[1;9C (iTerm2 Alt-Right arrow) Same as w.
2490 ^[[2~ (Insert) Same as i.
2491 ^[[3;5~ (Ctrl-Delete) Same as dw.
2492 ^[OA (Up Arrow) Same as ^[[A.
2493 ^[OB (Down Arrow) Same as ^[[B.
2494 ^[OC (Right Arrow) Same as ^[[C.
2495 ^[OD (Left Arrow) Same as ^[[D.
2496 ^[O5C (Ctrl-Right Arrow) Same as w.
2497 ^[O5D (Ctrl-Left Arrow) Same as b.
2498 ^ Cursor to first non-blank character in line.
2499 $ Cursor to end of line.
2500 ^[[F (End) Same as $.
2501 ^[[4~ Same as $.
2502 ^[[8~ Same as $.
2503 ^[[Y Same as $.
2504 ^G Exit reverse search mode.
2505 % Moves to balancing (, ), {, }, [, or ]. If cursor is
2506 not on one of the above characters, the remainder of
2507 the line is searched for the first occurrence of one
2508 of the above characters first.
2509 Search Edit Commands
2511 These commands access your command history.
2512 [count]k Fetch previous command. Each time k is entered the
2514 previous command back in time is accessed.
2515 [count]- Equivalent to k.
2516 [count]^[[A
2517 (Up arrow) If cursor is at the end of the line it is
2518 equivalent to / with string set to the contents of the
2519 current line. Otherwise, it is equivalent to k.
2520 [count]j Fetch next command. Each time j is entered the next
2521 command forward in time is accessed.
2522 [count]+ Equivalent to j.
2523 [count]^[[B
2524 (Down arrow) Equivalent to j.
2525 [count]G The command number count is fetched. The default is
2526 the least recent history command.
2527 /string Search backward through history for a previous command
2528 containing string. String is terminated by a `RETURN'
2529 or `NEW LINE'. If string is preceded by a ^, the
2530 matched line must begin with string. If string is
2531 empty, the previous string will be used.
2532 ?string Same as / except that search will be in the forward
2533 direction.
2534 n Search for next match of the last pattern to / or ?
2535 commands.
2536 N Search for next match of the last pattern to / or ?,
2537 but in reverse direction.
2538 Text Modification Edit Commands
2540 These commands will modify the line.
2541 a Enter input mode and enter text after the current
2543 character.
2544 A Append text to the end of the line. Equivalent to $a.
2545 [count]cmotion
2546 c[count]motion
2547 Delete current character through the character that
2548 motion would move the cursor to and enter input mode.
2549 If motion is c, the entire line will be deleted and
2550 input mode entered.
2551 C Delete the current character through the end of line
2552 and enter input mode. Equivalent to c$.
2553 S Equivalent to cc.
2554 [count]s Replace characters under the cursor in input mode.
2555 D Delete the current character through the end of line.
2556 Equivalent to d$.
2557 [count]dmotion
2558 d[count]motion
2559 Delete current character through the character that
2560 motion would move to. If motion is d , the entire
2561 line will be deleted.
2562 i Enter input mode and insert text before the current
2563 character.
2564 I Insert text before the first non-blank character.
2565 Equivalent to ^i.
2566 [count]P Place the previous text modification before the cur‐
2567 sor.
2568 [count]p Place the previous text modification after the cursor.
2569 R Enter input mode and replace characters on the screen
2570 with characters you type overlay fashion.
2571 [count]rc Replace the count character(s) starting at the current
2572 cursor position with c, and advance the cursor.
2573 [count]x Delete current character.
2574 [count]^[[3~
2575 (Forward delete) Same as x.
2576 [count]X Delete preceding character.
2577 [count]. Repeat the previous text modification command.
2578 [count]∼ Invert the case of the count character(s) starting at
2579 the current cursor position and advance the cursor.
2580 [count]_ Causes the count word of the previous command to be
2581 appended and input mode entered. The last word is
2582 used if count is omitted.
2583 * Causes an * to be appended to the current word and
2584 pathname expansion attempted. If no match is found,
2585 it rings the bell. Otherwise, the word is replaced by
2586 the matching pattern and input mode is entered.
2587 \ Command or file name completion as described above.
2588 Other Edit Commands
2590 Miscellaneous commands.
2591 [count]ymotion
2593 y[count]motion
2594 Yank current character through character that motion
2595 would move the cursor to and puts them into the delete
2596 buffer. The text and cursor are unchanged.
2597 yy Yanks the entire line.
2598 Y Yanks from current position to end of line. Equiva‐
2599 lent to y$.
2600 u Undo the last text modifying command.
2601 U Undo all the text modifying commands performed on the
2602 line.
2603 [count]v Returns the command hist -e ${VISUAL:-${EDITOR:-vi}}
2604 count in the input buffer to call a full editor — vi
2605 by default — on a history entry. If count is omitted,
2606 then the current line is used.
2607 ^L Line feed and print current line. Has effect only in
2608 control mode.
2609 ^J (New line) Execute the current line, regardless of
2610 mode.
2611 ^M (Return) Execute the current line, regardless of mode.
2612 # If the first character of the command is a #, then
2613 this command deletes this # and each # that follows a
2614 newline. Otherwise, sends the line after inserting a
2615 # in front of each line in the command. Useful for
2616 causing the current line to be inserted in the history
2617 as a comment and uncommenting previously commented
2618 commands in the history file.
2619 [count]= If count is not specified, it generates the list of
2620 matching commands or file names as described above.
2621 Otherwise, the word under the cursor is replaced by
2622 the count item from the most recently generated com‐
2623 mand or file list. If the cursor is not on a word, it
2624 is inserted instead.
2625 @letter Your alias list is searched for an alias by the name
2626 _letter and if an alias of this name is defined, its
2627 value will be inserted on the input queue for process‐
2628 ing.
2629 ^V Display version of the shell.
2630 Built-in Commands.
2632 The simple-commands listed below are built in to the shell and are exe‐
2633 cuted in the same process as the shell. The effects of any added In‐
2634 put/Output redirections are local to the command, except for the exec
2635 and redirect commands. Unless otherwise indicated, the output is writ‐
2636 ten on standard output (file descriptor 1) and the exit status, when
2637 there is no syntax error, is zero. Except for :, true, false, and
2638 echo, all built-in commands accept -- to indicate end of options, and
2639 are self-documenting.
2640 The self-documenting commands interpret the option --man as a request
2642 to display that command's own manual page, --help as a request to dis‐
2643 play the OPTIONS section from their manual page, and -? as a request
2644 to print a brief usage message. All these are processed as error mes‐
2645 sages, so they are written on standard error (file descriptor 2) and to
2646 pipe them into a pager such as more(1) you need to add a 2>&1 redirect‐
2647 ion before the |. The display of boldface text depends on whether stan‐
2648 dard error is on a terminal, so is disabled when using a pager. Export‐
2649 ing the ERROR_OPTIONS environment variable with a value containing em‐
2650 phasis will force this on; a value containing noemphasis forces it off.
2651 The test/[ command needs an additional -- argument to recognize self-
2652 documentation options, e.g. test --man --. The exec and redirect com‐
2653 mands, as they make redirections permanent, should use self-documenta‐
2654 tion options in a subshell when redirecting, for example: (redirect
2655 --man) 2>&1. There are advanced output options as well; see getopts
2656 --man for more information.
2657 Commands that are preceded by a † symbol below are special built-
2659 in commands and are treated specially in the following ways:
2660 1. Variable assignment lists preceding the command remain in
2661 effect when the command completes.
2662 2. I/O redirections are processed after variable assign‐
2663 ments.
2664 3. Errors cause a script that contains them to abort.
2665 4. They are not valid function names.
2666 Commands that are preceded by a ‡ symbol below are declaration com‐
2668 mands. Any following words that are in the format of a variable as‐
2669 signment are expanded with the same rules as a variable assignment.
2670 This means that tilde expansion is performed after the = sign, array
2671 assignments of the form varname=(assign_list) are supported, and field
2672 splitting and pathname expansion are not performed.
2673 † : [ arg ... ]
2675 The command only expands parameters.
2676 † . name [ arg ... ]
2678 If name is a function defined with the function name reserved
2679 word syntax, the function is executed in the current environment
2680 (as if it had been defined with the name() syntax). Otherwise
2681 if name refers to a file, the file is read in its entirety and
2682 the commands are executed in the current shell environment. The
2683 search path specified by PATH is used to find the directory con‐
2684 taining the file. If any arguments arg are given, they become
2685 the positional parameters while processing the . command and
2686 the original positional parameters are restored upon completion.
2687 Otherwise the positional parameters are unchanged. The exit
2688 status is the exit status of the last command executed.
2689 [ expression ]
2691 The [ command is the same as test, with the exception that an
2692 additional closing ] argument is required. See test below.
2693 alias [ -ptx ] [ name[ =value ] ] ...
2695 alias with no arguments prints the list of aliases in the form
2696 name=value on standard output. The -p option causes the word
2697 alias to be inserted before each one. When one or more argu‐
2698 ments are given, an alias is defined for each name whose value
2699 is given. A trailing space in value causes the next word to be
2700 checked for alias substitution. With the -t option, each name
2701 is looked up as a command in $PATH and its path is added to the
2702 hash table as a 'tracked alias'. If no name is given, this
2703 prints the hash table. See hash. Without the -t option, for
2704 each name in the argument list for which no value is given, the
2705 name and value of the alias is printed. The obsolete -x option
2706 has no effect in most contexts, although if it's used with -t it
2707 will suppress all output. The exit status is non-zero if a name
2708 is given, but no value, and no alias has been defined for the
2709 name.
2710 autoload name ...
2712 Marks each name undefined so that the FPATH variable will be
2713 searched to find the function definition when the function is
2714 referenced. The same as typeset -fu.
2715 bg [ job... ]
2717 This command is only on systems that support job control. Puts
2718 each specified job into the background. The current job is put
2719 in the background if job is not specified. See Jobs for a de‐
2720 scription of the format of job.
2721 † break [ n ]
2723 Exit from the enclosing for, while, until, or select loop, if
2724 any. If n is specified, then break n levels.
2725 builtin [ -ds ] [ -f file ] [ name ... ]
2727 If name is not specified, and no -f option is specified, the
2728 built-ins are printed on standard output. The -s option prints
2729 only the special built-ins. Otherwise, each name represents the
2730 pathname whose basename is the name of the built-in. The entry
2731 point function name is determined by prepending b_ to the built-
2732 in name. A built-in specified by a pathname will only be exe‐
2733 cuted when that pathname would be found during the path search.
2734 Built-ins found in libraries loaded via the .paths file will as‐
2735 sociate with the pathname of the directory containing the .paths
2736 file.
2737 The ISO C/C++ prototype is b_mycommand(int argc, char *argv[],
2739 void *context) for the builtin command mycommand where argv is
2740 array an of argc elements and context is an optional pointer to
2741 a Shell_t structure as described in <ast/shell.h>.
2742 Special built-ins cannot be bound to a pathname or deleted. The
2744 -d option deletes each of the given built-ins. On systems that
2745 support dynamic loading, the -f option names a shared library
2746 containing the code for built-ins. The shared library prefix
2747 and/or suffix, which depend on the system, can be omitted. Once
2748 a library is loaded, its symbols become available for subsequent
2749 invocations of builtin. Multiple libraries can be specified
2750 with separate invocations of the builtin command. Libraries are
2751 searched in the reverse order in which they are specified. When
2752 a library is loaded, it looks for a function in the library
2753 whose name is lib_init() and invokes this function with an argu‐
2754 ment of 0.
2755 cd [ -L ] [ -eP ] [ arg ]
2757 cd [ -L ] [ -eP ] old new
2758 This command can be in either of two forms. In the first form
2759 it changes the current directory to arg. If arg is - the direc‐
2760 tory is changed to the previous directory. The shell variable
2761 HOME is the default arg. The variable PWD is set to the current
2762 directory. The shell variable CDPATH defines the search path
2763 for the directory containing arg. Alternative directory names
2764 are separated by a colon (:). The default path is the empty
2765 string (specifying the current directory). Note that the cur‐
2766 rent directory may be specified by a dot (.) or by an empty
2767 path name, either of which can appear immediately after the
2768 equal sign or between the colon delimiters anywhere else in the
2769 path list. If arg begins with a / then the search path is not
2770 used. Otherwise, each directory in the path is searched for
2771 arg.
2772 The second form of cd substitutes the string new for the string
2773 old in the current directory name, PWD, and tries to change to
2774 this new directory.
2775 By default, symbolic link names are treated literally when find‐
2776 ing the directory name. This is equivalent to the -L option.
2777 The -P option causes symbolic links to be resolved when deter‐
2778 mining the directory. The last instance of -L or -P on the com‐
2779 mand line determines which method is used.
2780 If -e and -P are both in effect and the correct PWD could not be
2781 determined after successfully changing the directory, cd will
2782 return with exit status one and produce no output. If any other
2783 error occurs while both flags are active, the exit status is
2784 greater than one.
2785 The cd command may not be executed by rksh.
2786 command [ -pvxV ] name [ arg ... ]
2788 With the -v option, command is equivalent to the built-in whence
2789 command described below. The -V option causes command to act
2790 like whence -v.
2791 Without the -v or -V options, command executes name with the ar‐
2793 guments given by arg. Functions and aliases will not be
2794 searched for when finding name. If name refers to a special
2795 built-in, as marked with † in this manual, command disables the
2796 special properties described above for that mark, executing the
2797 command as a regular built-in. (For example, using command set
2798 -o option-name prevents a script from terminating when an in‐
2799 valid option name is given.)
2800 The -p option causes the operating system's standard utilities
2802 path (as output by getconf PATH) to be searched rather than the
2803 one defined by the value of PATH.
2804 The -x option searches for name as an external command, bypass‐
2806 ing built-ins. If the arguments contain at least one word that
2807 expands to multiple arguments, for example *.txt or "$@", then
2808 the -x option also allows executing external commands with argu‐
2809 ment lists that are longer than the operating system allows.
2810 This functionality is similar to xargs(1) but is easier to use.
2811 The shell does this by invoking the external command multiple
2812 times if needed, dividing the expanded argument list over the
2813 invocations. Any arguments that come before the first word that
2814 expands to multiple arguments, as well as any that follow the
2815 last such word, are repeated for each invocation. This allows
2816 each invocation to use the same command options, as well as the
2817 same trailing destination arguments for commands like cp(1) or
2818 mv(1). When all invocations are completed, command -x exits
2819 with the status of the invocation that had the highest exit sta‐
2820 tus. (Note that command -x may still fail with an "argument
2821 list too long" error if a single argument exceeds the maximum
2822 length of the argument list, or if a long arguments list con‐
2823 tains no word that expands to multiple arguments.)
2824 ‡ compound vname[=value] ...
2826 Causes each vname to be a compound variable. The same as type‐
2827 set -C.
2828 † continue [ n ]
2830 Resume the next iteration of the enclosing for, while, until, or
2831 select loop. If n is specified, then resume at the n-th enclos‐
2832 ing loop.
2833 disown [ job... ]
2835 Causes the shell not to send a HUP signal to each given job, or
2836 all active jobs if job is omitted, when a login shell termi‐
2837 nates.
2838 echo [ arg ... ]
2840 When the first arg does not begin with a -, and none of the ar‐
2841 guments contain a \, then echo prints each of its arguments sep‐
2842 arated by a space and terminated by a new-line. Otherwise, the
2843 behavior of echo is system dependent and print or printf de‐
2844 scribed below should be used. See echo(1) for usage and de‐
2845 scription.
2846 ‡ enum [ -i ] type[=(value ...) ] ...
2848 Creates, for each type specified, an enumeration type declara‐
2849 tion command named type. Variables of the created type can only
2850 store any one of the values given. For example, enum
2851 bool=(false true) creates a Boolean variable type of which vari‐
2852 ables may be declared like bool x=true y=false. If =(value ...)
2853 is omitted, then type must be an indexed array variable with at
2854 least two elements and the values are taken from this array
2855 variable. If -i is specified the values are case-insensitive.
2856 Declaration commands are created as special builtins that cannot
2857 be removed or overridden by shell functions. Each created dec‐
2858 laration command has a --man option that shows documentation on
2859 its type's behavior and possible values.
2860 Within arithmetic expressions (see Arithmetic Evaluation above),
2862 enumeration type values translate to index numbers between 0 and
2863 the number of defined values minus 1. It is an error for an
2864 arithmetic expression to assign a value outside of that range.
2865 Decimal fractions are ignored. Taking the bool type from the
2866 example above, if a variable of this type is used in an arith‐
2867 metic expression, false translates to 0 and true to 1. Enumera‐
2868 tion values may also be used directly in an arithmetic expres‐
2869 sion that refers to a variable of an enumeration type. To con‐
2870 tinue our example, for a bool variable v, ((v==true)) is the
2871 same as ((v==1)) and if a variable named true exists, it is ig‐
2872 nored.
2873 † eval [ arg ... ]
2875 The arguments are read as input to the shell and the resulting
2876 command(s) executed.
2877 † exec [ -c ] [ -a name ] [ arg ... ]
2879 If arg is given, the command specified by the arguments is exe‐
2880 cuted in place of this shell without creating a new process.
2881 The value of the SHLVL environment variable is decreased by one,
2882 unless the shell replaced is a subshell. The -c option causes
2883 the environment to be cleared before applying variable assign‐
2884 ments associated with the exec invocation. The -a option causes
2885 name rather than the first arg, to become argv[0] for the new
2886 process. If arg is not given and only I/O redirections are
2887 given, then this command persistently modifies file descriptors
2888 as in redirect.
2889 † exit [ n ]
2891 Causes the shell to exit with the exit status specified by n.
2892 The value will be the least significant 8 bits of n (if speci‐
2893 fied) or of the exit status of the last command executed. An
2894 end-of-file will also cause the shell to exit, except for an in‐
2895 teractive shell that has the ignoreeof option turned on (see set
2896 below).
2897 †‡ export [ -p ] [ name[=value] ] ...
2899 If name is not given, the names and values of each variable with
2900 the export attribute are printed with the values quoted in a
2901 manner that allows them to be re-input. The export command is
2902 the same as typeset -x except that if you use export within a
2903 function, no local variable is created. The -p option causes
2904 the word export to be inserted before each one. Otherwise, the
2905 given names are marked for automatic export to the environment
2906 of subsequently-executed commands.
2907 false Does nothing, and exits 1. Used with until for infinite loops.
2909 fc [ -e ename ] [ -N num ] [ -nlr ] [ first [ last ] ]
2911 fc -s [ old=new ] [ command ]
2912 The same as hist.
2913 fg [ job... ]
2915 This command is only on systems that support job control. Each
2916 job specified is brought to the foreground and waited for in the
2917 specified order. Otherwise, the current job is brought into the
2918 foreground. See Jobs for a description of the format of job.
2919 ‡ float vname[=value] ...
2921 Declares each vname to be a long floating point number. The
2922 same as typeset -lE.
2923 functions [ -Stux ] [ name ... ]
2925 Lists functions. The same as typeset -f.
2926 getconf [ name [ pathname ] ]
2928 Prints the current value of the configuration parameter given by
2929 name. The configuration parameters are defined by the IEEE
2930 POSIX 1003.1 and IEEE POSIX 1003.2 standards. (See pathconf(2)
2931 and sysconf(3).) The pathname argument is required for parame‐
2932 ters whose value depends on the location in the file system. If
2933 no arguments are given, getconf prints the names and values of
2934 the current configuration parameters. The pathname / is used
2935 for each of the parameters that requires pathname.
2936 getopts [ -a name ] optstring vname [ arg ... ]
2938 Checks arg for legal options. If arg is omitted, the positional
2939 parameters are used. An option argument begins with a + or a -.
2940 An option not beginning with + or - or the argument -- ends the
2941 options. Options beginning with + are only recognized when opt‐
2942 string begins with a +. optstring contains the letters that
2943 getopts recognizes. If a letter is followed by a :, that option
2944 is expected to have an argument. The options can be separated
2945 from the argument by blanks. The option -? causes getopts to
2946 generate a usage message on standard error. The -a argument can
2947 be used to specify the name to use for the usage message, which
2948 defaults to $0.
2949 getopts places the next option letter it finds inside variable
2950 vname each time it is invoked. The option letter will be
2951 prepended with a + when arg begins with a +. The index of the
2952 next arg is stored in OPTIND. The option argument, if any, gets
2953 stored in OPTARG.
2954 A leading : in optstring causes getopts to store the letter of
2955 an invalid option in OPTARG, and to set vname to ? for an un‐
2956 known option and to : when a required option argument is miss‐
2957 ing. Otherwise, getopts prints an error message. The exit sta‐
2958 tus is non-zero when there are no more options.
2959 There is no way to specify any of the options :, +, -, ?, [, and
2960 ]. The option # can only be specified as the first option.
2961 hash [ -r ] [ utility ]
2963 hash displays or modifies the hash table with the locations of
2964 recently used programs. If given no arguments, it lists all com‐
2965 mand/path associations (a.k.a. 'tracked aliases') in the hash
2966 table. Otherwise, hash performs a PATH search for each utility
2967 supplied and adds the result to the hash table. The -r option
2968 empties the hash table. This can also be achieved by resetting
2969 PATH.
2970 hist [ -e ename ] [ -N num ] [ -nlr ] [ first [ last ] ]
2972 hist -s [ old=new ] [ command ]
2973 In the first form, a range of commands from first to last is se‐
2974 lected from the last HISTSIZE commands that were typed at the
2975 terminal. The arguments first and last may be specified as a
2976 number or as a string. A string is used to locate the most re‐
2977 cent command starting with the given string. A negative number
2978 is used as an offset to the current command number. If the -l
2979 option is selected, the commands are listed on standard output.
2980 Otherwise, the editor program ename is invoked on a file con‐
2981 taining these keyboard commands. If ename is not supplied, then
2982 the value of the variable HISTEDIT is used. If HISTEDIT is not
2983 set, then FCEDIT (default /bin/ed) is used as the editor. When
2984 editing is complete, the edited command(s) is executed if the
2985 changes have been saved. If last is not specified, then it will
2986 be set to first. If first is not specified, the default is the
2987 previous command for editing and -16 for listing. The option -r
2988 reverses the order of the commands and the option -n suppresses
2989 command numbers when listing. In the second form, command is
2990 interpreted as first described above and defaults to the last
2991 command executed. The resulting command is executed after the
2992 optional substitution old=new is performed. The option -N
2993 causes hist to start num commands back.
2994 ‡ integer vname[=value] ...
2996 Declares each vname to be a long integer number. The same as
2997 typeset -li.
2998 jobs [ -lnp ] [ job ... ]
3000 Lists information about each given job; or all active jobs if
3001 job is omitted. The -l option lists process IDs in addition to
3002 the normal information. The -n option only displays jobs that
3003 have stopped or exited since last notified. The -p option
3004 causes only the process group to be listed. See Jobs for a de‐
3005 scription of the format of job.
3006 kill [ -s signame ] job ...
3008 kill [ -n signum ] job ...
3009 kill -Ll [ sig ... ]
3010 Sends either the TERM (terminate) signal or the specified signal
3011 to the specified jobs or processes. Signals are either given by
3012 number with the -n option or by name with the -s option (as
3013 given in <signal.h>, stripped of the prefix ``SIG''. For back‐
3014 ward compatibility, the n and s can be omitted and the number or
3015 name placed immediately after the -. If the signal being sent
3016 is TERM (terminate) or HUP (hangup), then the job or process
3017 will be sent a CONT (continue) signal if it is stopped. The ar‐
3018 gument job can be the process ID of a process that is not a mem‐
3019 ber of one of the active jobs. See Jobs for a description of
3020 the format of job. In the third form, kill -l or kill -L, if
3021 sig is not specified, the signal names are listed. The -l op‐
3022 tion lists only the signal names. The -L option lists each sig‐
3023 nal name and corresponding number. Otherwise, for each sig that
3024 is a name, the corresponding signal number is listed. For each
3025 sig that is a number, the signal name corresponding to the least
3026 significant 8 bits of sig is listed.
3027 let arg ...
3029 Each arg is a separate arithmetic expression to be evaluated.
3030 let only recognizes octal numbers starting with 0 when the set
3031 option letoctal is on. See Arithmetic Evaluation above for a
3032 description of arithmetic expression evaluation.
3033 The exit status is 0 if the value of the last expression is non-
3034 zero, and 1 otherwise.
3035 ‡ nameref vname[=refname] ...
3037 Declares each vname to be a variable name reference. The same
3038 as typeset -n.
3039 print [ -CRenprsv ] [ -u unit ] [ -f format ] [ arg ... ]
3041 With no options or with option - or --, each arg is printed on
3042 standard output. The -f option causes the arguments to be
3043 printed as described by printf. In this case, any e, n, r, R
3044 options are ignored. Otherwise, unless the -C, -R, -r, or -v
3045 are specified, the following escape conventions will be applied:
3046 \a The alert character (ASCII 07).
3047 \b The backspace character (ASCII 010).
3048 \c Causes print to end without processing more arguments and
3049 not adding a new-line.
3050 \f The formfeed character (ASCII 014).
3051 \n The newline character (ASCII 012).
3052 \r The carriage return character (ASCII 015).
3053 \t The tab character (ASCII 011).
3054 \v The vertical tab character (ASCII 013).
3055 \E The escape character (ASCII 033).
3056 \\ The backslash character \.
3057 \0x The character defined by the 1, 2, or 3-digit octal
3058 string given by x.
3059 The -R option will print all subsequent arguments and options
3061 other than -n. The -e causes the above escape conventions to be
3062 applied. This is the default behavior. It reverses the effect
3063 of an earlier -r. The -p option causes the arguments to be
3064 written onto the pipe of the process spawned with |& instead of
3065 standard output. The -v option treats each arg as a variable
3066 name and writes the value in the printf %B format. The -C op‐
3067 tion treats each arg as a variable name and writes the value in
3068 the printf %#B format. The -s option causes the arguments to be
3069 written onto the history file instead of standard output. The
3070 -u option can be used to specify a one digit file descriptor
3071 unit number unit on which the output will be placed. The de‐
3072 fault is 1. If the option -n is used, no new-line is added to
3073 the output.
3074 printf [ -v vname ] format [ arg ... ]
3076 The arguments arg are printed on standard output in accordance
3077 with the ANSI C formatting rules associated with the format
3078 string format. If the number of arguments exceeds the number of
3079 format specifications, the format string is reused to format re‐
3080 maining arguments. The following extensions can also be used:
3081 %b A %b format can be used instead of %s to cause escape se‐
3082 quences in the corresponding arg to be expanded as de‐
3083 scribed in print.
3084 %B A %B option causes each of the arguments to be treated as
3085 variable names and the binary value of variable will be
3086 printed. The alternate flag # causes a compound variable
3087 to be output on a single line. This is most useful for
3088 compound variables and variables whose attribute is -b.
3089 %H A %H format can be used instead of %s to cause characters
3090 in arg that are special in HTML and XML to be output as
3091 their entity name. The alternate flag # formats the out‐
3092 put for use as a URI.
3093 %p A %p format will convert the given number to hexadecimal.
3094 %P A %P format can be used instead of %s to cause arg to be
3095 interpreted as an extended regular expression and be
3096 printed as a shell pattern.
3097 %q A %q format can be used instead of %s to cause the re‐
3098 sulting string to be quoted in a manner than can be rein‐
3099 put to the shell. When q is preceded by the alternative
3100 format specifier, #, the string is quoted in manner suit‐
3101 able as a field in a .csv format file.
3102 %(date-format)T
3103 A %(date-format)T format can be used to treat an argument
3104 as a date/time string and to format the date/time accord‐
3105 ing to the date-format.
3106 %Q A %Q format will convert the given number of seconds to
3107 readable time.
3108 %R A %R format can be used instead of %s to cause arg to be
3109 interpreted as a shell pattern and to be printed as an
3110 extended regular expression.
3111 %Z A %Z format will output a byte whose value is 0.
3112 %d The precision field of the %d format can be followed by a
3113 . and the output base. In this case, the # flag charac‐
3114 ter causes base# to be prepended.
3115 # The # flag, when used with the %d format without an out‐
3116 put base, displays the output in powers of 1000 indicated
3117 by one of the following suffixes: k M G T P E, and when
3118 used with the %i format displays the output in powers of
3119 1024 indicated by one of the following suffixes: Ki Mi Gi
3120 Ti Pi Ei.
3121 = The = flag centers the output within the specified field
3122 width.
3123 L The L flag, when used with the %c or %s formats, treats
3124 precision as character width instead of byte count.
3125 , The , flag, when used with the %d or %f formats, sepa‐
3126 rates groups of digits with the grouping delimiter (, on
3127 groups of 3 in the C locale).
3128 The -v option assigns the output directly to a variable instead
3130 of writing it to standard output. This is faster than capturing
3131 the output using a command substitution and avoids the latter's
3132 stripping of final linefeed characters (\n). The vname argument
3133 should be a valid variable name, optionally with one or more ar‐
3134 ray subscripts in square brackets. Note that square brackets
3135 should be quoted to avoid pathname expansion.
3136 pwd [ -LP ]
3139 Outputs the value of the current working directory. The -L op‐
3140 tion is the default; it prints the logical name of the current
3141 directory. If the -P option is given, all symbolic links are
3142 resolved from the name. The last instance of -L or -P on the
3143 command line determines which method is used.
3144 read [ -ACSaprsv ] [ -d delim ] [ -n n ] [ -N n ] [ -t timeout ] [ -u
3146 unit ] [ vname?prompt ] [ vname ... ]
3147 The shell input mechanism. One line is read and is broken up
3148 into fields using the characters in IFS as separators. The es‐
3149 cape character, \, is used to remove any special meaning for the
3150 next character and for line continuation. The first field is
3151 assigned to the first vname, the second field to the second
3152 vname, etc., with leftover fields assigned to the last vname.
3153 If vname is omitted, then REPLY is used as the default vname.
3154 When vname has the binary attribute and -n or -N is specified,
3155 the bytes that are read are stored directly into the variable.
3156 If you append ?prompt to the first vname, then read will display
3157 prompt on standard error before reading if standard input is a
3158 terminal or pipe; the ? should be quoted to protect it from
3159 pathname expansion. The exit status is 0 unless an end-of-file
3160 is encountered or read has timed out. The options for the read
3161 command have meaning as follows:
3162 -A Causes the variable vname to be unset and each field
3163 that is read to be stored in successive elements of the
3164 indexed array vname.
3165 -C Causes the variable vname to be read as a compound vari‐
3166 able. Blanks will be ignored when finding the beginning
3167 open parenthesis.
3168 -N Causes n bytes to be read unless an end-of-file has been
3169 encountered or the read times out because of the -t op‐
3170 tion.
3171 -S Causes the line to be treated like a record in a .csv
3172 format file so that double quotes can be used to allow
3173 the delimiter character and the new-line character to
3174 appear within a field.
3175 -a Same as -A.
3176 -d Causes the read to continue to the first character of
3177 delim instead of the newline control character. Multi‐
3178 byte characters for delim are not supported.
3179 -n Causes at most n bytes to be read instead of a full
3180 line, but will return when reading from a slow device as
3181 soon as any characters have been read.
3182 -p Input is read from the current co-process spawned by the
3183 shell using ⎪&. An end-of-file causes read to discon‐
3184 nect the co-process so that another can be created.
3185 -r Raw mode. The \ character is not treated specially.
3186 -s The input will be saved as a command in the history
3187 file.
3188 -t Used to specify a timeout in seconds when reading from a
3189 terminal or pipe.
3190 -u This option can be used to specify a one-digit file de‐
3191 scriptor unit unit to read from. The file descriptor
3192 can be opened with the exec or redirect built-in com‐
3193 mand. If unit is p, input is read from the current co-
3194 process as with the -p option. The default value of
3195 unit is 0.
3196 -v The value of the first vname will be used as a default
3197 value when reading from a terminal device.
3198 †‡ readonly [ -p ] [ vname[=value] ] ...
3200 If vname is not given, the names and values of each variable
3201 with the read-only attribute is printed with the values quoted
3202 in a manner that allows them to be re-input. The -p option
3203 causes the word readonly to be inserted before each one. Other‐
3204 wise, the given vnames are marked read-only and these names can‐
3205 not be changed by subsequent assignment. Unlike typeset -r ,
3206 readonly does not create a function-local scope and the given
3207 vnames are marked globally read-only by default. When defining
3208 a type, if the value of a read-only subvariable is not defined,
3209 the value is required when creating each instance.
3210 redirect
3212 This command only accepts input/output redirections. It can
3213 open and close files and modify file descriptors from 0 to 9 as
3214 specified by the input/output redirection list (see the In‐
3215 put/Output section above), with the difference that the effect
3216 persists past the execution of the redirect command. When in‐
3217 voking another program, file descriptors greater than 2 that
3218 were opened with this mechanism are only passed on if they are
3219 explicitly redirected to themselves as part of the invocation
3220 (e.g. 4>&4) or if the posix option is set.
3221 † return [ n ]
3223 Causes a shell function, dot script (see . and source), or pro‐
3224 file script to return to the invoking shell environment with the
3225 exit status specified by n. This status value can use the full
3226 signed integer range as shown by the commands getconf INT_MIN
3227 and getconf INT_MAX. A value outside that range will produce a
3228 warning and an exit status of 128. If n is omitted, then the
3229 value of $? is assumed, i.e., the exit status of the last com‐
3230 mand executed is passed on. If return is invoked while not in a
3231 function, dot script, or profile script, then it behaves the
3232 same as exit.
3233 † set [ ±BCGHabefhkmnprstuvx ] [ ±o [ option ] ] ... [ ±A vname ] [
3235 arg ... ]
3236 The options for this command have meaning as follows:
3237 -A Array assignment. Unset the variable vname and assign
3238 values sequentially from the arg list. If +A is used,
3239 the variable vname is not unset first.
3240 -B Enable brace group expansion. On by default, except if
3241 ksh is invoked as sh or rsh.
3242 -C Prevents redirection > from truncating existing files.
3243 Files that are created are opened with the O_EXCL mode.
3244 Requires >| to truncate a file when turned on.
3245 -G Enables recursive pathname expansion. This adds the
3246 double-star pattern ** to the pathname expansion (see
3247 Pathname Expansion above). By itself, it matches the
3248 recursive contents of the current directory, which is to
3249 say, all files and directories in the current directory
3250 and in all its subdirectories, sub-subdirectories, and
3251 so on. If the pathname pattern ends in **/, only direc‐
3252 tories and subdirectories are matched, including sym‐
3253 bolic links that point to directories. A prefixed di‐
3254 rectory name is not included in the results unless that
3255 directory was itself found by a pattern. For example,
3256 dir/** matches the recursive contents of dir but not dir
3257 itself, whereas di[r]/** matches both dir itself and the
3258 recursive contents of dir. Symbolic links to non-direc‐
3259 tories are not followed. Symbolic links to directories
3260 are followed if they are specified literally or match a
3261 pattern as described under Pathname Expansion, but not
3262 if they result from a double-star pattern.
3263 -H Enable !-style history expansion similar to csh(1). See
3264 History Expansion above.
3265 -a All variables that are assigned a value while this op‐
3266 tion is on are automatically exported, unless they have
3267 a dot in their name. Variables created in namespaces
3268 declared with the namespace keyword (see Name Spaces
3269 above) are only exported while their name space is ac‐
3270 tive.
3271 -b Prints job completion messages as soon as a background
3272 job changes state rather than waiting for the next
3273 prompt. If one of the shell line editors is in use (see
3274 In-line Editing Options above), the completion message
3275 is inserted directly above the command line being typed.
3276 -e Unless contained in a || or && command, or the command
3277 following an if while or until command or in the pipe‐
3278 line following !, if a command has a non-zero exit sta‐
3279 tus, execute the ERR trap, if set, and exit. This mode
3280 is disabled while reading profiles.
3281 -f Disables pathname expansion.
3282 -h Obsolete; no effect.
3283 -k All variable assignment arguments are placed in the en‐
3284 vironment for a command, not just those that precede the
3285 command name.
3286 -m Background jobs will run in a separate process group and
3287 a line will print upon completion. The exit status of
3288 background jobs is reported in a completion message. A
3289 pipeline will not terminate until all component commands
3290 of the pipeline have terminated. On systems with job
3291 control, this option is turned on automatically for in‐
3292 teractive shells.
3293 -n Read commands and check them for syntax errors, but do
3294 not execute them. Ignored for interactive shells.
3295 -o The following argument can be one of the following op‐
3296 tion names:
3297 allexport
3298 Same as -a.
3299 backslashctrl
3300 The backslash character \ escapes the next con‐
3301 trol character in the emacs built-in editor and
3302 the next erase or kill character in the vi
3303 built-in editor. On by default.
3304 bgnice All background jobs are run at a lower priority.
3305 This is the default mode.
3306 braceexpand
3307 Same as -B.
3308 emacs Activates the emacs-style command line editor.
3309 See Emacs Editing Mode above.
3310 errexit Same as -e.
3311 functrace
3312 Causes the -x option's state and the DEBUG trap
3313 action to be inherited by functions defined us‐
3314 ing the function keyword (see Functions above)
3315 instead of being reset to default. Changes made
3316 to them within the function do not propagate
3317 back to the parent scope. Similarly, this op‐
3318 tion also causes the DEBUG trap action to be in‐
3319 herited by subshells.
3320 globcasedetect
3321 When this option is turned on, globbing (see
3322 Pathname Expansion above) and file name listing
3323 and completion (see In-line Editing Options
3324 above) automatically become case-insensitive on
3325 file systems where the difference between upper-
3326 and lowercase is ignored for file names. This is
3327 transparently determined for each directory, so
3328 a path pattern that spans multiple file systems
3329 can be part case-sensitive and part case-insen‐
3330 sitive. In more precise terms, each slash-sepa‐
3331 rated path name component pattern p is treated
3332 as ~(i:p) if its parent directory exists on a
3333 case-insensitive file system. This option is
3334 only present on operating systems that support
3335 case-insensitive file systems.
3336 globstar
3337 Same as -G.
3338 gmacs Activates the emacs-style command line editor
3339 with modified ^T. See Emacs Editing Mode above.
3340 histexpand
3341 Same as -H.
3342 histreedit
3343 If a history expansion (see -H) fails, the com‐
3344 mand line is reloaded into the next prompt's
3345 edit buffer, allowing corrections.
3346 histverify
3347 The results of a history expansion (see -H) are
3348 not immediately executed. Instead, the expanded
3349 line is loaded into the next prompt's edit buf‐
3350 fer, allowing further changes.
3351 ignoreeof
3352 An interactive shell will not exit on end-of-
3353 file. The command exit must be used.
3354 keyword Same as -k.
3355 letoctal
3356 The let command allows octal numbers starting
3357 with 0. On by default if ksh is invoked as sh
3358 or rsh.
3359 markdirs
3360 All directory names resulting from pathname ex‐
3361 pansion have a trailing / appended.
3362 monitor Same as -m.
3363 multiline
3364 The built-in editors will use multiple lines on
3365 the screen for lines that are longer than the
3366 width of the screen. This may not work for all
3367 terminals. The shell uses the system default
3368 tput(1) command to obtain the terminal escape
3369 codes for the necessary operations. Multi-line
3370 editing is disabled if this fails. On most sys‐
3371 tems, setting the TERM variable to your termi‐
3372 nal's type and exporting it corrects this situa‐
3373 tion. The multiline option is ineffectual on
3374 systems whose tput(1) command supports neither
3375 terminfo(5) nor termcap(5) capability names.
3376 noclobber
3377 Same as -C.
3378 noexec Same as -n.
3379 noglob Same as -f.
3380 nolog Obsolete; has no effect.
3381 notify Same as -b.
3382 nounset Same as -u.
3383 pipefail
3384 The exit status of the entire pipeline will be
3385 that of the last component command that exited
3386 with a non-zero exit status, or zero if no com‐
3387 mand exited with a non-zero exit status. The
3388 shell will wait for all component commands of
3389 the pipeline to terminate, instead of only wait‐
3390 ing for the last component command.
3391 posix Enables the POSIX standard mode for maximum com‐
3392 patibility with other compliant shells. At the
3393 moment that the posix option is turned on, it
3394 also turns on letoctal and turns off -B/braceex‐
3395 pand; the reverse is done when posix is turned
3396 back off. (These options can still be controlled
3397 independently in between.) Furthermore, the
3398 posix option is automatically turned on upon in‐
3399 vocation if the shell is invoked as sh or rsh,
3400 or if -o posix or --posix is specified on the
3401 shell invocation command line, or when executing
3402 scripts without a #! path with this option ac‐
3403 tive in the invoking shell. In that case, the
3404 invoked shell will not import type attributes
3405 for variables (such as integer or left/right
3406 justify) from the environment.
3407 In addition, while on, the posix option
3408 • disables exporting variable type attributes
3409 to the environment for other ksh processes to
3410 import;
3411 • disallows brace expansion on the results of
3412 unquoted expansions (if the -B/braceexpand
3413 option is turned back on);
3414 • disables the special handling of repeated
3415 isspace class characters in the IFS variable;
3416 • causes file descriptors > 2 to be left open
3417 when invoking another program;
3418 • disables the &> redirection shorthand;
3419 • disables fast filescan loops of type while
3420 inputredirection ;do list ;done;
3421 • makes the <> redirection operator default to
3422 redirecting standard input if no file de‐
3423 scriptor number precedes it;
3424 • causes the shell to use a standard UNIX
3425 pipe(2) instead of a socketpair(2) to connect
3426 commands in a pipeline (when reading directly
3427 from a pipeline, the <#pattern and <##pattern
3428 redirection operators will not work and the
3429 -n option to the read built-in will not re‐
3430 turn early when reading from a slow device);
3431 • disables the special floating point constants
3432 Inf and NaN in arithmetic evaluation so that,
3433 e.g., $((inf)) and $((nan)) refer to the
3434 variables by those names;
3435 • enables the recognition of a leading zero as
3436 introducing an octal number in all arithmetic
3437 evaluation contexts, except in the let built-
3438 in while letoctal is off;
3439 • disables zero-padding of seconds in the out‐
3440 put of the time and times built-ins;
3441 • stops the . command (but not source) from
3442 looking up functions defined with the func‐
3443 tion syntax;
3444 • disables the recognition of unexpanded shell
3445 arithmetic expressions for the numerical con‐
3446 version specifiers of the printf built-in
3447 command, causing them to print a warning for
3448 operands that are not valid decimal, 0x-pre‐
3449 fixed hexadecimal or 0-prefixed octal num‐
3450 bers;
3451 • disables the special handling of /dev/fd/n in
3452 file existence and access test operators in
3453 test/[ and [[, causing these to operate on
3454 the file /dev/fd/n in the file system;
3455 • disables the recognition of unexpanded shell
3456 arithmetic expressions in the numerical com‐
3457 parison operators -eq, -ne, -gt, -ge, -lt and
3458 -le of the test/[ built-in command, causing
3459 them to accept only decimal numbers as oper‐
3460 ands;
3461 • changes the test/[ built-in command to make
3462 its deprecated expr1 -a expr2 and expr1 -o
3463 expr2 operators work even if expr1 equals "!"
3464 or "(" (which means the nonstandard unary -a
3465 file and -o option operators cannot be di‐
3466 rectly negated using ! or wrapped in paren‐
3467 theses); and
3468 • disables a hack that makes test -t ([ -t ])
3469 equivalent to test -t 1 ([ -t 1 ]).
3470 privileged
3471 Same as -p.
3472 showme When enabled, simple commands or pipelines pre‐
3473 ceded by a semicolon (;) will be displayed as if
3474 the xtrace option were enabled but will not be
3475 executed. Otherwise, the leading ; will be ig‐
3476 nored.
3477 trackall
3478 Same as -h.
3479 verbose Same as -v.
3480 vi Activates the vi-style command line editor, ini‐
3481 tially in input mode. See Vi Editing Mode
3482 above.
3483 viraw Obsolete; has no effect.
3484 xtrace Same as -x.
3485 If no option name is supplied, then the current option
3487 settings are printed.
3488 -p Disables processing of the $HOME/.profile file and uses
3490 the file /etc/suid_profile instead of the ENV file.
3491 This mode is on whenever the effective UID (GID) is not
3492 equal to the real UID (GID). Turning this off causes
3493 the effective UID and GID to be set to the real UID and
3494 GID.
3495 -r Enables the restricted shell. This option cannot be un‐
3496 set once set.
3497 -s Sort the positional parameters lexicographically.
3498 -t (Obsolete). Exit after reading and executing one com‐
3499 mand.
3500 -u Treat unset parameters as an error when substituting.
3501 $@ and $* are exempt.
3502 -v Print shell input lines as they are read.
3503 -x Print commands and their arguments as they are executed.
3504 -- Do not change any of the options; useful in setting $1
3505 to a value beginning with -. If no arguments follow
3506 this option then the positional parameters are unset.
3507 As an obsolete feature, if the first arg is - then the -x and -v
3509 options are turned off and the next arg is treated as the first
3510 argument. Using + rather than - causes these options to be
3511 turned off. These options can also be used upon invocation of
3512 the shell. The current set of options may be found in $-. Un‐
3513 less -A is specified, the remaining arguments are positional pa‐
3514 rameters and are assigned, in order, to $1 $2 .... If no argu‐
3515 ments are given, then the names and values of all variables are
3516 printed on the standard output.
3517 † shift [ n ]
3519 The positional parameters from $n+1 ... are renamed $1 ... ,
3520 default n is 1. The parameter n can be any arithmetic expres‐
3521 sion that evaluates to a non-negative number less than or equal
3522 to $#.
3523 sleep [ -s ] duration
3525 Suspends execution for the number of decimal seconds or frac‐
3526 tions of a second given by duration. duration can be an inte‐
3527 ger, floating point value or ISO 8601 duration specifying the
3528 length of time to sleep. The option -s causes the sleep builtin
3529 to terminate when it receives any signal. If duration is not
3530 specified in conjunction with -s, sleep will wait for a signal
3531 indefinitely.
3532 source name [ arg ... ]
3534 Same as ., except it is not treated as a special built-in com‐
3535 mand.
3536 stop job ...
3538 Sends a SIGSTOP signal to one or more processes specified by
3539 job, suspending them until they receive SIGCONT. The same as
3540 kill -s STOP.
3541 suspend
3543 Sends a SIGSTOP signal to the main shell process, suspending the
3544 script or child shell session until it receives SIGCONT (for in‐
3545 stance, when typing fg in the parent shell). Equivalent to
3546 kill -s STOP "$$", except that it accepts no operands and re‐
3547 fuses to suspend a login shell.
3548 test expression
3550 The test and [ commands execute conditional expressions similar
3551 to those specified for the [[ compound command under Conditional
3552 Expressions above, but with several important differences. The
3553 =, == and != operators test for string (in)equality without pat‐
3554 tern matching; == is nonstandard and unportable. The && and ||
3555 operators are not available. Instead, the -a and -o binary oper‐
3556 ators can be used, but they are fraught with pitfalls due to
3557 grammatical ambiguities and therefore deprecated in favor of in‐
3558 voking separate test commands. Most importantly, as test and [
3559 are simple regular commands, field splitting and pathname expan‐
3560 sion are performed on all their arguments and all aspects of
3561 regular shell grammar (such as redirection) remain active. This
3562 is usually harmful, so care must be taken to quote arguments and
3563 expansions to avoid this. To avoid the many pitfalls arising
3564 from these issues, the [[ compound command should be used in‐
3565 stead. The primary purpose of the test and [ commands is compat‐
3566 ibility with other shells that lack [[.
3567 The test/[ command does not parse options except if there are
3569 two arguments and the second is --. To access the inline docu‐
3570 mentation with an option such as --man, you need one of the
3571 forms test --man -- or [ --man -- ].
3572 times Displays the accumulated user and system CPU times, one line
3574 with the times used by the shell and another with those used by
3575 all of the shell's child processes. No options are supported.
3576 Seconds are zero-padded unless the posix shell option is on.
3577 † trap [ -p ] [ action ] [ sig ] ...
3579 The -p option causes the trap action associated with each trap
3580 as specified by the arguments to be printed with appropriate
3581 quoting. Otherwise, action will be processed as if it were an
3582 argument to eval when the shell receives signal(s) sig. Each
3583 sig can be given as a number or as the name of the signal. Trap
3584 commands are executed in order of signal number. Any attempt to
3585 set a trap on a signal that was ignored on entry to the current
3586 shell is ineffective. If action is omitted and the first sig is
3587 a number, or if action is -, then the trap(s) for each sig are
3588 reset to their original values. If action is the empty string,
3589 then this signal is ignored by the shell and by the commands it
3590 invokes. If sig is ERR then action will be executed whenever a
3591 command has a non-zero exit status. If sig is DEBUG then action
3592 will be executed before each command. The variable .sh.command
3593 will contain the current command line when action is running, in
3594 the same format as the output generated by the xtrace option
3595 (minus the preceding PS4 prompt). If the exit status of the
3596 trap is 2 the command will not be executed. If the exit status
3597 of the trap is 255 and inside a function or a dot script, the
3598 function or dot script will return. If sig is 0 or EXIT and the
3599 trap statement is executed inside the body of a function defined
3600 with the function name syntax, then the command action is exe‐
3601 cuted after the function completes. If sig is 0 or EXIT for a
3602 trap set outside any function then the command action is exe‐
3603 cuted on exit from the shell. If sig is KEYBD, then action will
3604 be executed whenever a key is read while in emacs, gmacs, or vi
3605 mode. The trap command with no arguments prints a list of com‐
3606 mands associated with each signal number.
3607 An exit or return without an argument in a trap action will preserve
3609 the exit status of the command that invoked the trap.
3610 true Does nothing, and exits 0. Used with while for infinite loops.
3612 type [ -afpPqt ] name ...
3614 The same as whence -v.
3615 †‡ typeset [ ±ACHSbflmnprstux ] [ ±EFLRXZi[n] ] [ +-M [ mapname ] ]
3617 [ -T [ tname=(assign_list) ] ] [ -h str ] [ -a [ [type] ] ] [
3618 vname[=value ] ] ...
3619 Sets attributes and values for shell variables and functions.
3620 When invoked inside a function defined with the function name
3621 syntax, a new instance of the variable vname is created, and the
3622 variable's value and type are restored when the function com‐
3623 pletes. The following list of attributes may be specified:
3624 -A Declares vname to be an associative array. Subscripts
3625 are strings rather than arithmetic expressions.
3626 -C Causes each vname to be a compound variable. If value
3627 names a compound variable, it is copied into vname. Oth‐
3628 erwise, the empty compound value is assigned to vname.
3629 -a Declares vname to be an indexed array. This is the de‐
3630 fault. Subscripts are numerical and start at 0. To make
3631 it possible to use alphanumeric enumeration constants of
3632 a given type as subscripts, an option value of the form
3633 [type] can be specified (including the surrounding square
3634 brackets), which should be quoted to avoid pathname ex‐
3635 pansion), where type must be the name of an enumeration
3636 type created with the enum command.
3637 -E Declares vname to be a double precision floating point
3638 number. If n is non-zero, it defines the number of sig‐
3639 nificant figures that are used when expanding vname.
3640 Otherwise, ten significant figures will be used.
3641 -F Declares vname to be a double precision floating point
3642 number. If n is non-zero, it defines the number of
3643 places after the decimal point that are used when expand‐
3644 ing vname. Otherwise ten places after the decimal point
3645 will be used.
3646 -H This option provides UNIX to host-name file mapping on
3647 non-UNIX machines.
3648 -L Left justify and remove leading blanks from value. If n
3649 is non-zero, it defines the width of the field, otherwise
3650 it is determined by the width of the value of first as‐
3651 signment. When the variable is assigned to, it is filled
3652 on the right with blanks or truncated, if necessary, to
3653 fit into the field. The -R option is turned off.
3654 -M Use the character mapping mapping defined by wctrans(3).
3655 such as tolower and toupper when assigning a value to
3656 each of the specified operands. When mapping is speci‐
3657 fied and there are not operands, all variables that use
3658 this mapping are written to standard output. When map‐
3659 ping is omitted and there are no operands, all mapped
3660 variables are written to standard output.
3661 -R Right justify and fill with leading blanks. If n is non-
3662 zero, it defines the width of the field, otherwise it is
3663 determined by the width of the value of first assignment.
3664 The field is left filled with blanks or truncated from
3665 the end if the variable is reassigned. The -L option is
3666 turned off.
3667 -S When used within the assign_list of a type definition, it
3668 causes the specified subvariable to be shared by all in‐
3669 stances of the type. When used inside a function defined
3670 with the function reserved word, the specified variables
3671 will have function static scope. Otherwise, the variable
3672 is unset prior to processing the assignment list.
3673 -T If followed by tname, it creates a type named by tname
3674 using the compound assignment assign_list to tname. Oth‐
3675 erwise, it writes all the type definitions to standard
3676 output.
3677 -X Declares vname to be a double precision floating point
3678 number and expands using the %a format of ISO-C99. If n
3679 is non-zero, it defines the number of hex digits after
3680 the radix point that is used when expanding vname. The
3681 default is 10.
3682 -Z Right justify and fill with leading zeros if the first
3683 non-blank character is a digit and the -L option has not
3684 been set. Remove leading zeros if the -L option is also
3685 set. If n is non-zero, it defines the width of the
3686 field, otherwise it is determined by the width of the
3687 value of first assignment.
3688 -f The names refer to function names rather than variable
3689 names. No assignments can be made and the only other
3690 valid options are -S, -t, -u and -x. The -S can be used
3691 with discipline functions defined in a type to indicate
3692 that the function is static. For a static function, the
3693 same method will be used by all instances of that type no
3694 matter which instance references it. In addition, it can
3695 only use value of variables from the original type defi‐
3696 nition. These discipline functions cannot be redefined
3697 in any type instance. The -t option turns on execution
3698 tracing for this function. The -u option causes this
3699 function to be marked undefined. The FPATH variable will
3700 be searched to find the function definition when the
3701 function is referenced. If no options other than -f is
3702 specified, then the function definition will be displayed
3703 on standard output. If +f is specified, then a line con‐
3704 taining the function name followed by a shell comment
3705 containing the line number and path name of the file
3706 where this function was defined, if any, is displayed.
3707 The exit status can be used to determine whether the
3708 function is defined so that typeset -f .sh.math.name will
3709 return 0 when math function name is defined and non-zero
3710 otherwise.
3711 -b The variable can hold any number of bytes of data. The
3712 data can be text or binary. The value is represented by
3713 the base64 encoding of the data. If -Z is also speci‐
3714 fied, the size in bytes of the data in the buffer will be
3715 determined by the size associated with the -Z. If the
3716 base64 string assigned results in more data, it will be
3717 truncated. Otherwise, it will be filled with bytes whose
3718 value is zero. The printf format %B can be used to out‐
3719 put the actual data in this buffer instead of the base64
3720 encoding of the data.
3721 -g Forces variables to be created or modified at the global
3722 scope, even when typeset is executed in a function de‐
3723 fined by the function name syntax (see Functions above)
3724 or in a name space (see Name Spaces above).
3725 -h Used within type definitions to add information when gen‐
3726 erating information about the subvariable on the man
3727 page. It is ignored when used outside of a type defini‐
3728 tion. When used with -f the information is associated
3729 with the corresponding discipline function.
3730 -i Declares vname to be represented internally as integer.
3731 The right hand side of an assignment is evaluated as an
3732 arithmetic expression when assigning to an integer. If n
3733 is non-zero, it defines the output arithmetic base, oth‐
3734 erwise the output base will be ten.
3735 -l Used with -i, -E or -F, to indicate long integer, or long
3736 float. Otherwise, all uppercase characters are converted
3737 to lowercase. The uppercase option, -u, is turned off.
3738 Equivalent to -M tolower .
3739 -m Moves or renames the variable. The value is the name of
3740 a variable whose value will be moved to vname. The orig‐
3741 inal variable will be unset. Cannot be used with any
3742 other options.
3743 -n Declares vname to be a reference to the variable whose
3744 name is defined by the value of variable vname. This is
3745 usually used to reference a variable inside a function
3746 whose name has been passed as an argument. Cannot be
3747 used with other options except -g.
3748 -p The name, attributes and values for the given vnames are
3749 written on standard output in a form that can be used as
3750 shell input. If +p is specified, then the values are not
3751 displayed.
3752 -r The given vnames are marked read-only and these names
3753 cannot be changed by subsequent assignment.
3754 -s When given along with -i, restricts integer size to
3755 short.
3756 -t Tags the variables. Tags are user definable and have no
3757 special meaning to the shell.
3758 -u When given along with -i, specifies unsigned integer.
3759 Otherwise, all lowercase characters are converted to up‐
3760 percase. The lowercase option, -l, is turned off.
3761 Equivalent to -M toupper .
3762 -x The given vnames are marked for automatic export to the
3763 environment of subsequently-executed commands. Variables
3764 whose names contain a . cannot be exported.
3765 The -i, -F, -E, and -X options cannot be specified along with
3767 -R, -L, or -Z. The -b option cannot be specified along with -L,
3768 -u, or -l. The -f, -m, -n, and -T options cannot be used to‐
3769 gether with any other option.
3770 Using + rather than - causes these options to be turned off. If
3772 no vname arguments are given, a list of vnames (and optionally
3773 the values) of the variables is printed. (Using + rather than -
3774 keeps the values from being printed.) The -p option causes
3775 typeset followed by the option letters to be printed before each
3776 name rather than the names of the options. If any option other
3777 than -p is given, only those variables which have all of the
3778 given options are printed. Otherwise, the vnames and attributes
3779 of all variables that have attributes are printed.
3780 ulimit [ -HSaMctdfkxlqenVuPpmrRbiswTv ] [ limit ]
3782 Set or display a resource limit. The available resource limits
3783 are listed below. Many systems do not support one or more of
3784 these limits. The limit for a specified resource is set when
3785 limit is specified. The value of limit can be a number in the
3786 unit specified below with each resource, or the value unlimited.
3787 The -H and -S options specify whether the hard limit or the soft
3788 limit for the given resource is set. A hard limit cannot be in‐
3789 creased once it is set. A soft limit can be increased up to the
3790 value of the hard limit. If neither the H nor S option is spec‐
3791 ified, the limit applies to both. The current resource limit is
3792 printed when limit is omitted. In this case, the soft limit is
3793 printed unless H is specified. When more than one resource is
3794 specified, then the limit name and unit is printed before the
3795 value.
3796 -a Lists all of the current resource limits.
3797 -b The socket buffer size in bytes.
3798 -c The number of 512-byte blocks on the size of core dumps.
3799 -d The number of K-bytes on the size of the data area.
3800 -e The scheduling priority.
3801 -f The number of 512-byte blocks on files that can be writ‐
3802 ten by the current process or by child processes (files
3803 of any size may be read).
3804 -i The signal queue size.
3805 -k The max number of kqueues created by the current user.
3806 -l The locked address space in K-bytes.
3807 -M The address space limit in K-bytes.
3808 -m The number of K-bytes on the size of physical memory.
3809 -n The number of file descriptors plus 1.
3810 -P The max number of pseudo-terminals created by the current
3811 user.
3812 -p The number of 512-byte blocks for pipe buffering.
3813 -q The message queue size in K-bytes.
3814 -R The max time a real-time process can run before blocking,
3815 in microseconds. If this limit is exceeded the process
3816 is sent a SIGXCPU signal.
3817 -r The max real-time priority.
3818 -s The number of K-bytes on the size of the stack area.
3819 -T The number of threads.
3820 -t The number of CPU seconds to be used by each process.
3821 -u The number of processes.
3822 -V The number of open vnode monitors.
3823 -v The number of K-bytes for virtual memory.
3824 -w The swap size in K-bytes.
3825 -x The number of file locks.
3826 If no option is given, -f is assumed.
3828 umask [ -S ] [ mask ]
3830 The user file-creation mask is set to mask (see umask(2)). mask
3831 can either be an octal number or a symbolic value as described
3832 in chmod(1). If a symbolic value is given, the new umask value
3833 is the complement of the result of applying mask to the comple‐
3834 ment of the previous umask value. If mask is omitted, the cur‐
3835 rent value of the mask is printed. The -S option causes the
3836 mode to be printed as a symbolic value. Otherwise, the mask is
3837 printed in octal.
3838 unalias [ -a ] name ...
3840 The aliases given by the list of names are removed from the
3841 alias list. The -a option causes all the aliases to be unset.
3842 † unset [ -fnv ] vname ...
3844 The variables given by the list of vnames are unassigned, i.e.,
3845 except for subvariables within a type, their values and at‐
3846 tributes are erased. For subvariables of a type, the values are
3847 reset to the default value from the type definition. Readonly
3848 variables cannot be unset. If the -f option is set, then the
3849 names refer to function names. If the -v option is set, then
3850 the names refer to variable names. The -f option overrides -v.
3851 If -n is set and name is a name reference, then name will be un‐
3852 set rather than the variable that it references. The default is
3853 equivalent to -v. Unsetting LINENO, MAILCHECK, OPTARG, OPTIND,
3854 RANDOM, SECONDS, TMOUT, and _ removes their special meaning even
3855 if they are subsequently assigned to.
3856 wait [ job ... ]
3858 Wait for the specified job and report its termination status.
3859 If job is not given, then all currently active child processes
3860 are waited for. The exit status from this command is that of
3861 the last process waited for if job is specified; otherwise it is
3862 zero. See Jobs for a description of the format of job.
3863 whence [ -afpPqtv ] name ...
3865 For each name, indicate how it would be interpreted if used as a
3866 command name.
3867 The -v option produces a more verbose report. The -f option
3868 skips the search for functions. The -p and -P options do a path
3869 search for name even if name is an alias, a function, or a re‐
3870 served word. Both of these options turn off the -v option. The
3871 -q option causes whence to enter quiet mode. whence will return
3872 zero if all arguments are built-ins, functions, or are programs
3873 found on the path. The -t option only outputs the type of the
3874 given command. Like -p and -P, -t will turn off the -v option.
3875 The -a option is similar to the -v option but causes all inter‐
3876 pretations of the given name to be reported.
3877 Invocation.
3879 If the shell is invoked by exec(2), initialization depends on argument
3880 zero ($0) as follows. If the first character of $0 is -, or the -l op‐
3881 tion is given on the invocation command line, then the shell is assumed
3882 to be a login shell. If the basename of the command path in $0 is rsh,
3883 rksh, or krsh, then the shell becomes restricted. If the basename is
3884 sh or rsh, or the -o posix option is given on the invocation command
3885 line, then the shell is initialized in full POSIX compliance mode (see
3886 the set builtin command above for more information). After this, if
3887 the shell was assumed to be a login shell, commands are read from
3888 /etc/profile and then from $HOME/.profile if it exists. Alternatively,
3889 the option -l causes the shell to be treated as a login shell. Next,
3890 for interactive shells, commands are read from the file named by ENV if
3891 the file exists, its name being determined by performing parameter ex‐
3892 pansion, command substitution, and arithmetic expansion on the value of
3893 that environment variable. If the -s option is not present and arg and
3894 a file by the name of arg exists, then it reads and executes this
3895 script. Otherwise, if the first arg does not contain a /, a path
3896 search is performed on the first arg to determine the name of the
3897 script to execute. The script arg must have execute permission and any
3898 setuid and setgid settings will be ignored. If the script is not found
3899 on the path, arg is processed as if it named a built-in command or
3900 function. Commands are then read as described below; the following op‐
3901 tions are interpreted by the shell when it is invoked:
3902 -D A list of all double quoted strings that are preceded by a $
3904 will be printed on standard output and the shell will exit.
3905 This set of strings will be subject to language translation
3906 when the locale is not C or POSIX. No commands will be exe‐
3907 cuted.
3908 -E or -o rc or --rc
3910 Read the file named by the ENV variable or by $HOME/.kshrc if
3911 not defined after the profiles. On by default for interactive
3912 shells. Use +E, +o rc or --norc to turn off.
3913 -c Read and execute a script from the first arg instead of a file.
3915 The second arg, if present, becomes that script's command name
3916 ($0). Any third and further args become positional parameters
3917 starting at $1.
3918 -s Read and execute a script from standard input instead of a
3920 file. The command name ($0) cannot be set. Any args become
3921 the positional parameters starting at $1. This option is
3922 forced on if no arg is given and is ignored if -c is also spec‐
3923 ified.
3924 -i or -o interactive or --interactive
3926 If the -i option is present or if the shell's standard input
3927 and standard error are attached to a terminal (as told by tcge‐
3928 tattr(3)), then this shell is interactive. In this case TERM
3929 is ignored (so that kill 0 does not kill an interactive shell)
3930 and INTR is caught and ignored (so that wait is interruptible).
3931 In all cases, QUIT is ignored by the shell.
3932 -r or -o restricted or --restricted
3934 If the -r option is present, the shell is a restricted shell.
3935 The remaining options and arguments are described under the set command
3937 above. An optional - as the first argument is ignored.
3938 Rksh Only.
3940 Rksh is used to set up login names and execution environments whose ca‐
3941 pabilities are more controlled than those of the standard shell. The
3942 actions of rksh are identical to those of ksh, except that the follow‐
3943 ing are disallowed:
3944 • unsetting the restricted option
3946 • changing directory (see cd(1))
3948 • setting or unsetting the value or attributes of SHELL,
3950 ENV, FPATH, or PATH
3951 • specifying path or command names containing /
3953 • redirecting output (>, >|, <>, and >>)
3955 • adding or deleting built-in commands
3957 • using command -p to invoke a command
3959 The restrictions above are enforced after .profile and the ENV files
3961 are interpreted.
3962 When a command to be executed is found to be a shell procedure, rksh
3964 invokes ksh to execute it. Thus, it is possible to provide to the end-
3965 user shell procedures that have access to the full power of the stan‐
3966 dard shell, while imposing a limited menu of commands; this scheme as‐
3967 sumes that the end-user does not have write and execute permissions in
3968 the same directory.
3969 The net effect of these rules is that the writer of the .profile has
3971 complete control over user actions, by performing guaranteed setup ac‐
3972 tions and leaving the user in an appropriate directory (probably not
3973 the login directory).
3974 The system administrator often sets up a directory of commands (e.g.,
3976 /usr/rbin) that can be safely invoked by rksh.
3977
3979 Errors detected by the shell, such as syntax errors, cause the shell to
3980 return a non-zero exit status. If the shell is being used non-interac‐
3981 tively, then execution of the shell file is abandoned unless the error
3982 occurs inside a subshell in which case the subshell is abandoned. Oth‐
3983 erwise, the shell returns the exit status of the last command executed
3984 (see also the exit command above). Run time errors detected by the
3985 shell are reported by printing the command or function name and the er‐
3986 ror condition. If the line number that the error occurred on is
3987 greater than one, then the line number is also printed in square brack‐
3988 ets ([]) after the command or function name.
3989
3991 /etc/profile
3992 The system wide initialization file, executed for login shells.
3993 $HOME/.profile
3995 The personal initialization file, executed for login shells af‐
3996 ter /etc/profile.
3997 $HOME/.kshrc
3999 Default personal initialization file, executed for interactive
4000 shells when ENV is not set.
4001 /etc/suid_profile
4003 Alternative initialization file, executed instead of the per‐
4004 sonal initialization file when the real and effective user or
4005 group ID do not match.
4006 /dev/null
4008 The null device.
4009
4011 cat(1), cd(1), chmod(1), cut(1), date(1), echo(1), emacs(1), env(1),
4012 gmacs(1), grep(1), stty(1), test(1), umask(1), vi(1), dup(2), exec(2),
4013 fork(2), getpwnam(3), ioctl(2), lseek(2), paste(1), pathconf(2),
4014 pipe(2), sysconf(3), umask(2), ulimit(2), wait(2), strftime(3), wc‐
4015 trans(3), rand(3), a.out(5), profile(5), environ(7).
4016 Morris I. Bolsky and David G. Korn, The New KornShell Command and Pro‐
4018 gramming Language, Prentice Hall, 1995.
4019 POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC
4021 9945-2, IEEE, 1993.
4022
4024 If a command is executed, and then a command with the same name is in‐
4025 stalled in a directory in the search path before the directory where
4026 the original command was found, the shell will continue to exec the
4027 original command. Use the hash command or the -t option of the alias
4028 command to correct this situation.
4029 Using the hist built-in command within a compound command will cause
4031 the whole command to disappear from the history file.
4032 The built-in command . file reads the whole file before any commands
4034 are executed. Therefore, alias and unalias commands in the file will
4035 not apply to any commands defined in the file.
4036 Traps are not processed while a job is waiting for a foreground
4038 process. Thus, a trap on CHLD won't be executed until the foreground
4039 job terminates.
4040 In locales that use a multibyte character set such as UTF-8, the KEYBD
4042 trap is only triggered for ASCII characters (1-127).
4043 It is a good idea to leave a space after the comma operator in arith‐
4045 metic expressions to prevent the comma from being interpreted as the
4046 decimal point character in certain locales.
4047 KSH(1)