1MKSH(1) BSD General Commands Manual MKSH(1)
2
4 mksh, sh — MirBSD Korn shell
5
7 mksh [-+abCefhiklmnprUuvXx] [-T /dev/ttyCn | -] [-+o option] [-c string |
8 -s | file [argument ...]]
9
11 mksh is a command interpreter intended for both interactive and shell
12 script use. Its command language is a superset of the sh(C) shell lan‐
13 guage and largely compatible to the original Korn shell.
14 The options are as follows:
16 -c string
18 mksh will execute the command(s) contained in string.
19 -i Interactive shell. A shell is “interactive” if this option is
21 used or if both standard input and standard error are attached to
22 a tty(4). An interactive shell has job control enabled, ignores
23 the SIGINT, SIGQUIT, and SIGTERM signals, and prints prompts
24 before reading input (see the PS1 and PS2 parameters). It also
25 processes the ENV parameter or $HOME/.mkshrc (see below). For
26 non-interactive shells, the trackall option is on by default (see
27 the set command below).
28 -l Login shell. If the basename the shell is called with (i.e.
30 argv[0]) starts with ‘-’ or if this option is used, the shell is
31 assumed to be a login shell and the shell reads and executes the
32 contents of /etc/profile and $HOME/.profile if they exist and are
33 readable.
34 -p Privileged shell. A shell is “privileged” if this option is used
36 or if the real user ID or group ID does not match the effective
37 user ID or group ID (see getuid(2) and getgid(2)). A privileged
38 shell does not process $HOME/.profile nor the ENV parameter or
39 $HOME/.mkshrc (see below). Instead, the file /etc/suid_profile
40 is processed. Clearing the privileged option causes the shell to
41 set its effective user ID (group ID) to its real user ID (group
42 ID).
43 -r Restricted shell. A shell is “restricted” if this option is
45 used. The following restrictions come into effect after the
46 shell processes any profile and ENV files:
47 · The cd command is disabled.
49 · The SHELL, ENV, and PATH parameters cannot be changed.
50 · Command names can't be specified with absolute or relative
51 paths.
52 · The -p option of the built-in command command can't be used.
53 · Redirections that create files can't be used (i.e. ‘>’, ‘>|’,
54 ‘>>’, ‘<>’).
55 -s The shell reads commands from standard input; all non-option
57 arguments are positional parameters.
58 -T tty Spawn mksh on the tty(4) device given. Superuser only. If tty
60 is a dash, detach from controlling terminal (daemonise) instead.
61 In addition to the above, the options described in the set built-in com‐
63 mand can also be used on the command line: both [-+abCefhkmnuvXx] and
64 [-+o option] can be used for single letter or long options, respectively.
65 If neither the -c nor the -s option is specified, the first non-option
67 argument specifies the name of a file the shell reads commands from. If
68 there are no non-option arguments, the shell reads commands from the
69 standard input. The name of the shell (i.e. the contents of $0) is
70 determined as follows: if the -c option is used and there is a non-option
71 argument, it is used as the name; if commands are being read from a file,
72 the file is used as the name; otherwise, the basename the shell was
73 called with (i.e. argv[0]) is used.
74 If the ENV parameter is set when an interactive shell starts (or, in the
76 case of login shells, after any profiles are processed), its value is
77 subjected to parameter, command, arithmetic, and tilde (‘~’) substitution
78 and the resulting file (if any) is read and executed. If the ENV vari‐
79 able is unset or empty, the file $HOME/.mkshrc is read and processed like
80 above instead, leaving ENV unchanged. This processing does not occur if
81 ENV is set to a non-existing filename.
82 The exit status of the shell is 127 if the command file specified on the
84 command line could not be opened, or non-zero if a fatal syntax error
85 occurred during the execution of a script. In the absence of fatal
86 errors, the exit status is that of the last command executed, or zero, if
87 no command is executed.
88 Command syntax
90 The shell begins parsing its input by removing any backslash-newline com‐
91 binations, then breaking it into words. Words (which are sequences of
92 characters) are delimited by unquoted whitespace characters (space, tab,
93 and newline) or meta-characters (‘<’, ‘>’, ‘|’, ‘;’, ‘(’, ‘)’, and ‘&’).
94 Aside from delimiting words, spaces and tabs are ignored, while newlines
95 usually delimit commands. The meta-characters are used in building the
96 following tokens: ‘<’, ‘<&’, ‘<<’, ‘<<<’, ‘>’, ‘>&’, ‘>>’, etc. are used
97 to specify redirections (see Input/output redirection below); ‘|’ is used
98 to create pipelines; ‘|&’ is used to create co-processes (see
99 Co-processes below); ‘;’ is used to separate commands; ‘&’ is used to
100 create asynchronous pipelines; ‘&&’ and ‘||’ are used to specify condi‐
101 tional execution; ‘;;’ is used in case statements; ‘(( .. ))’ is used in
102 arithmetic expressions; and lastly, ‘( .. )’ is used to create subshells.
103 Whitespace and meta-characters can be quoted individually using a back‐
105 slash (‘\’), or in groups using double (‘"’) or single (‘'’) quotes.
106 Note that the following characters are also treated specially by the
107 shell and must be quoted if they are to represent themselves: ‘\’, ‘"’,
108 ‘'’, ‘#’, ‘$’, ‘`’, ‘~’, ‘{’, ‘}’, ‘*’, ‘?’, and ‘[’. The first three of
109 these are the above mentioned quoting characters (see Quoting below);
110 ‘#’, if used at the beginning of a word, introduces a comment – every‐
111 thing after the ‘#’ up to the nearest newline is ignored; ‘$’ is used to
112 introduce parameter, command, and arithmetic substitutions (see
113 Substitution below); ‘`’ introduces an old-style command substitution
114 (see Substitution below); ‘~’ begins a directory expansion (see Tilde
115 expansion below); ‘{’ and ‘}’ delimit csh(1)-style alterations (see Brace
116 expansion below); and finally, ‘*’, ‘?’, and ‘[’ are used in file name
117 generation (see File name patterns below).
118 As words and tokens are parsed, the shell builds commands, of which there
120 are two basic types: simple-commands, typically programmes that are exe‐
121 cuted, and compound-commands, such as for and if statements, grouping
122 constructs, and function definitions.
123 A simple-command consists of some combination of parameter assignments
125 (see Parameters below), input/output redirections (see Input/output
126 redirections below), and command words; the only restriction is that
127 parameter assignments come before any command words. The command words,
128 if any, define the command that is to be executed and its arguments. The
129 command may be a shell built-in command, a function, or an external com‐
130 mand (i.e. a separate executable file that is located using the PATH
131 parameter; see Command execution below). Note that all command con‐
132 structs have an exit status: for external commands, this is related to
133 the status returned by wait(2) (if the command could not be found, the
134 exit status is 127; if it could not be executed, the exit status is 126);
135 the exit status of other command constructs (built-in commands, func‐
136 tions, compound-commands, pipelines, lists, etc.) are all well-defined
137 and are described where the construct is described. The exit status of a
138 command consisting only of parameter assignments is that of the last com‐
139 mand substitution performed during the parameter assignment or 0 if there
140 were no command substitutions.
141 Commands can be chained together using the ‘|’ token to form pipelines,
143 in which the standard output of each command but the last is piped (see
144 pipe(2)) to the standard input of the following command. The exit status
145 of a pipeline is that of its last command. A pipeline may be prefixed by
146 the ‘!’ reserved word which causes the exit status of the pipeline to be
147 logically complemented: if the original status was 0, the complemented
148 status will be 1; if the original status was not 0, the complemented sta‐
149 tus will be 0.
150 Lists of commands can be created by separating pipelines by any of the
152 following tokens: ‘&&’, ‘||’, ‘&’, ‘|&’, and ‘;’. The first two are for
153 conditional execution: “cmd1 && cmd2” executes cmd2 only if the exit sta‐
154 tus of cmd1 is zero; ‘||’ is the opposite – cmd2 is executed only if the
155 exit status of cmd1 is non-zero. ‘&&’ and ‘||’ have equal precedence
156 which is higher than that of ‘&’, ‘|&’, and ‘;’, which also have equal
157 precedence. Note that the ‘&&’ and ‘||’ operators are
158 "left-associative". For example, both of these commands will print only
159 "bar":
160 $ false && echo foo || echo bar
162 $ true || echo foo && echo bar
163 The ‘&’ token causes the preceding command to be executed asynchronously;
165 that is, the shell starts the command but does not wait for it to com‐
166 plete (the shell does keep track of the status of asynchronous commands;
167 see Job control below). When an asynchronous command is started when job
168 control is disabled (i.e. in most scripts), the command is started with
169 signals SIGINT and SIGQUIT ignored and with input redirected from
170 /dev/null (however, redirections specified in the asynchronous command
171 have precedence). The ‘|&’ operator starts a co-process which is a spe‐
172 cial kind of asynchronous process (see Co-processes below). Note that a
173 command must follow the ‘&&’ and ‘||’ operators, while it need not follow
174 ‘&’, ‘|&’, or ‘;’. The exit status of a list is that of the last command
175 executed, with the exception of asynchronous lists, for which the exit
176 status is 0.
177 Compound commands are created using the following reserved words. These
179 words are only recognised if they are unquoted and if they are used as
180 the first word of a command (i.e. they can't be preceded by parameter
181 assignments or redirections):
182 case else function then !
184 do esac if time [[
185 done fi in until {
186 elif for select while }
187 Note: Some shells (but not this one) execute control structure commands
189 in a subshell when one or more of their file descriptors are redirected,
190 so any environment changes inside them may fail. To be portable, the
191 exec statement should be used instead to redirect file descriptors before
192 the control structure.
193 In the following compound command descriptions, command lists (denoted as
195 list) that are followed by reserved words must end with a semicolon, a
196 newline, or a (syntactically correct) reserved word. For example, the
197 following are all valid:
198 $ { echo foo; echo bar; }
200 $ { echo foo; echo bar<newline>}
201 $ { { echo foo; echo bar; } }
202 This is not valid:
204 $ { echo foo; echo bar }
206 (list) Execute list in a subshell. There is no implicit way to pass
208 environment changes from a subshell back to its parent.
209 { list; }
211 Compound construct; list is executed, but not in a subshell.
212 Note that ‘{’ and ‘}’ are reserved words, not meta-characters.
213 case word in [([] pattern [| pattern] ... ) list ;; ] ... esac
215 The case statement attempts to match word against a specified
216 pattern; the list associated with the first successfully matched
217 pattern is executed. Patterns used in case statements are the
218 same as those used for file name patterns except that the
219 restrictions regarding ‘.’ and ‘/’ are dropped. Note that any
220 unquoted space before and after a pattern is stripped; any space
221 within a pattern must be quoted. Both the word and the patterns
222 are subject to parameter, command, and arithmetic substitution,
223 as well as tilde substitution. For historical reasons, open and
224 close braces may be used instead of in and esac e.g. case $foo {
225 *) echo bar; }. The exit status of a case statement is that of
226 the executed list; if no list is executed, the exit status is
227 zero.
228 for name [in word ...]; do list; done
230 For each word in the specified word list, the parameter name is
231 set to the word and list is executed. If in is not used to spec‐
232 ify a word list, the positional parameters ($1, $2, etc.) are
233 used instead. For historical reasons, open and close braces may
234 be used instead of do and done e.g. for i; { echo $i; }. The
235 exit status of a for statement is the last exit status of list;
236 if list is never executed, the exit status is zero.
237 if list; then list; [elif list; then list;] ... [else list;] fi
239 If the exit status of the first list is zero, the second list is
240 executed; otherwise, the list following the elif, if any, is exe‐
241 cuted with similar consequences. If all the lists following the
242 if and elifs fail (i.e. exit with non-zero status), the list fol‐
243 lowing the else is executed. The exit status of an if statement
244 is that of non-conditional list that is executed; if no non-con‐
245 ditional list is executed, the exit status is zero.
246 select name [in word ...]; do list; done
248 The select statement provides an automatic method of presenting
249 the user with a menu and selecting from it. An enumerated list
250 of the specified word(s) is printed on standard error, followed
251 by a prompt (PS3: normally ‘#? ’). A number corresponding to one
252 of the enumerated words is then read from standard input, name is
253 set to the selected word (or unset if the selection is not
254 valid), REPLY is set to what was read (leading/trailing space is
255 stripped), and list is executed. If a blank line (i.e. zero or
256 more IFS characters) is entered, the menu is reprinted without
257 executing list.
258 When list completes, the enumerated list is printed if REPLY is
260 NULL, the prompt is printed, and so on. This process continues
261 until an end-of-file is read, an interrupt is received, or a
262 break statement is executed inside the loop. If “in word ...” is
263 omitted, the positional parameters are used (i.e. $1, $2, etc.).
264 For historical reasons, open and close braces may be used instead
265 of do and done e.g. select i; { echo $i; }. The exit status of a
266 select statement is zero if a break statement is used to exit the
267 loop, non-zero otherwise.
268 until list; do list; done
270 This works like while, except that the body is executed only
271 while the exit status of the first list is non-zero.
272 while list; do list; done
274 A while is a pre-checked loop. Its body is executed as often as
275 the exit status of the first list is zero. The exit status of a
276 while statement is the last exit status of the list in the body
277 of the loop; if the body is not executed, the exit status is
278 zero.
279 function name { list; }
281 Defines the function name (see Functions below). Note that redi‐
282 rections specified after a function definition are performed
283 whenever the function is executed, not when the function defini‐
284 tion is executed.
285 name() command
287 Mostly the same as function (see Functions below).
288 time [-p] [pipeline]
290 The time reserved word is described in the Command execution sec‐
291 tion.
292 (( expression ))
294 The arithmetic expression expression is evaluated; equivalent to
295 “let expression” (see Arithmetic expressions and the let command,
296 below).
297 [[ expression ]]
299 Similar to the test and [ ... ] commands (described later), with
300 the following exceptions:
301 · Field splitting and file name generation are not per‐
303 formed on arguments.
304 · The -a (AND) and -o (OR) operators are replaced with
306 ‘&&’ and ‘||’, respectively.
307 · Operators (e.g. ‘-f’, ‘=’, ‘!’) must be unquoted.
309 · The second operand of the ‘!=’ and ‘=’ expressions are
311 patterns (e.g. the comparison [[ foobar = f*r ]] suc‐
312 ceeds).
313 · The single argument form of test, which tests if the
315 argument has a non-zero length, is not valid; explicit
316 operators must always be used e.g. instead of [ str ]
317 use [[ -n str ]].
318 · Parameter, command, and arithmetic substitutions are
320 performed as expressions are evaluated and lazy expres‐
321 sion evaluation is used for the ‘&&’ and ‘||’ opera‐
322 tors. This means that in the following statement,
323 $(<foo) is evaluated if and only if the file foo exists
324 and is readable:
325 $ [[ -r foo && $(<foo) = b*r ]]
327 Quoting
329 Quoting is used to prevent the shell from treating characters or words
330 specially. There are three methods of quoting. First, ‘\’ quotes the
331 following character, unless it is at the end of a line, in which case
332 both the ‘\’ and the newline are stripped. Second, a single quote (‘'’)
333 quotes everything up to the next single quote (this may span lines).
334 Third, a double quote (‘"’) quotes all characters, except ‘$’, ‘`’ and
335 ‘\’, up to the next unquoted double quote. ‘$’ and ‘`’ inside double
336 quotes have their usual meaning (i.e. parameter, command, or arithmetic
337 substitution) except no field splitting is carried out on the results of
338 double-quoted substitutions. If a ‘\’ inside a double-quoted string is
339 followed by ‘\’, ‘$’, ‘`’, or ‘"’, it is replaced by the second charac‐
340 ter; if it is followed by a newline, both the ‘\’ and the newline are
341 stripped; otherwise, both the ‘\’ and the character following are
342 unchanged.
343 Aliases
345 There are two types of aliases: normal command aliases and tracked
346 aliases. Command aliases are normally used as a short hand for a long or
347 often used command. The shell expands command aliases (i.e. substitutes
348 the alias name for its value) when it reads the first word of a command.
349 An expanded alias is re-processed to check for more aliases. If a com‐
350 mand alias ends in a space or tab, the following word is also checked for
351 alias expansion. The alias expansion process stops when a word that is
352 not an alias is found, when a quoted word is found, or when an alias word
353 that is currently being expanded is found.
354 The following command aliases are defined automatically by the shell:
356 autoload='typeset -fu'
358 functions='typeset -f'
359 hash='alias -t'
360 history='fc -l'
361 integer='typeset -i'
362 local='typeset'
363 login='exec login'
364 nohup='nohup '
365 r='fc -e -'
366 stop='kill -STOP'
367 suspend='kill -STOP $$'
368 type='whence -v'
369 Tracked aliases allow the shell to remember where it found a particular
371 command. The first time the shell does a path search for a command that
372 is marked as a tracked alias, it saves the full path of the command. The
373 next time the command is executed, the shell checks the saved path to see
374 that it is still valid, and if so, avoids repeating the path search.
375 Tracked aliases can be listed and created using alias -t. Note that
376 changing the PATH parameter clears the saved paths for all tracked
377 aliases. If the trackall option is set (i.e. set -o trackall or set -h),
378 the shell tracks all commands. This option is set automatically for non-
379 interactive shells. For interactive shells, only the following commands
380 are automatically tracked, unless -o posix is set: cat(1), cc(1),
381 chmod(1), cp(1), date(1), ed(1), emacs(1), grep(1), ls(1), make(1),
382 mv(1), pr(1), rm(1), sed(1), sh(1), vi(1), and who(1).
383 Substitution
385 The first step the shell takes in executing a simple-command is to per‐
386 form substitutions on the words of the command. There are three kinds of
387 substitution: parameter, command, and arithmetic. Parameter substitu‐
388 tions, which are described in detail in the next section, take the form
389 $name or ${...}; command substitutions take the form $(command) or (dep‐
390 recated) `command`; and arithmetic substitutions take the form
391 $((expression)).
392 If a substitution appears outside of double quotes, the results of the
394 substitution are generally subject to word or field splitting according
395 to the current value of the IFS parameter. The IFS parameter specifies a
396 list of characters which are used to break a string up into several
397 words; any characters from the set space, tab, and newline that appear in
398 the IFS characters are called “IFS whitespace”. Sequences of one or more
399 IFS whitespace characters, in combination with zero or one non-IFS white‐
400 space characters, delimit a field. As a special case, leading and trail‐
401 ing IFS whitespace and trailing IFS non-whitespace are stripped (i.e. no
402 leading or trailing empty field is created by it); leading non-IFS white‐
403 space does create an empty field.
404 Example: If IFS is set to “<space>:”, and VAR is set to
406 “<space>A<space>:<space><space>B::D”, the substitution for $VAR results
407 in four fields: ‘A’, ‘B’, ‘’ (an empty field), and ‘D’. Note that if the
408 IFS parameter is set to the NULL string, no field splitting is done; if
409 the parameter is unset, the default value of space, tab, and newline is
410 used.
411 Also, note that the field splitting applies only to the immediate result
413 of the substitution. Using the previous example, the substitution for
414 $VAR:E results in the fields: ‘A’, ‘B’, ‘’, and ‘D:E’, not ‘A’, ‘B’, ‘’,
415 ‘D’, and ‘E’. This behavior is POSIX compliant, but incompatible with
416 some other shell implementations which do field splitting on the word
417 which contained the substitution or use IFS as a general whitespace
418 delimiter.
419 The results of substitution are, unless otherwise specified, also subject
421 to brace expansion and file name expansion (see the relevant sections
422 below).
423 A command substitution is replaced by the output generated by the speci‐
425 fied command which is run in a subshell. For $(command) substitutions,
426 normal quoting rules are used when command is parsed; however, for the
427 deprecated `command` form, a ‘\’ followed by any of ‘$’, ‘`’, or ‘\’ is
428 stripped (a ‘\’ followed by any other character is unchanged). As a spe‐
429 cial case in command substitutions, a command of the form <file is inter‐
430 preted to mean substitute the contents of file. Note that $(<foo) has
431 the same effect as $(cat foo), but it is carried out more efficiently
432 because no process is started.
433 Note: $(command) expressions are currently parsed by finding matching
435 parentheses, regardless of quoting. This should be fixed soon.
436 Arithmetic substitutions are replaced by the value of the specified
438 expression. For example, the command print $((2+3*4)) displays 14. See
439 Arithmetic expressions for a description of an expression.
440 Parameters
442 Parameters are shell variables; they can be assigned values and their
443 values can be accessed using a parameter substitution. A parameter name
444 is either one of the special single punctuation or digit character param‐
445 eters described below, or a letter followed by zero or more letters or
446 digits (‘_’ counts as a letter). The latter form can be treated as
447 arrays by appending an array index of the form [expr] where expr is an
448 arithmetic expression. Array indices are currently limited to the range
449 0 through 4294967295 (for mksh only; portable maximum is 1023), inclu‐
450 sive. Parameter substitutions take the form $name, ${name}, or
451 ${name[expr]} where name is a parameter name. If substitution is per‐
452 formed on a parameter (or an array parameter element) that is not set, a
453 null string is substituted unless the nounset option (set -o nounset or
454 set -u) is set, in which case an error occurs.
455 Parameters can be assigned values in a number of ways. First, the shell
457 implicitly sets some parameters like ‘#’, ‘PWD’, and ‘$’; this is the
458 only way the special single character parameters are set. Second, param‐
459 eters are imported from the shell's environment at startup. Third,
460 parameters can be assigned values on the command line: for example,
461 FOO=bar sets the parameter “FOO” to “bar”; multiple parameter assignments
462 can be given on a single command line and they can be followed by a sim‐
463 ple-command, in which case the assignments are in effect only for the
464 duration of the command (such assignments are also exported; see below
465 for the implications of this). Note that both the parameter name and the
466 ‘=’ must be unquoted for the shell to recognise a parameter assignment.
467 The fourth way of setting a parameter is with the export, readonly, and
468 typeset commands; see their descriptions in the Command execution sec‐
469 tion. Fifth, for and select loops set parameters as well as the getopts,
470 read, and set -A commands. Lastly, parameters can be assigned values
471 using assignment operators inside arithmetic expressions (see Arithmetic
472 expressions below) or using the ${name=value} form of the parameter sub‐
473 stitution (see below).
474 Parameters with the export attribute (set using the export or typeset -x
476 commands, or by parameter assignments followed by simple commands) are
477 put in the environment (see environ(7)) of commands run by the shell as
478 name=value pairs. The order in which parameters appear in the environ‐
479 ment of a command is unspecified. When the shell starts up, it extracts
480 parameters and their values from its environment and automatically sets
481 the export attribute for those parameters.
482 Modifiers can be applied to the ${name} form of parameter substitution:
484 ${name:-word}
486 If name is set and not NULL, it is substituted; otherwise, word
487 is substituted.
488 ${name:+word}
490 If name is set and not NULL, word is substituted; otherwise,
491 nothing is substituted.
492 ${name:=word}
494 If name is set and not NULL, it is substituted; otherwise, it is
495 assigned word and the resulting value of name is substituted.
496 ${name:?word}
498 If name is set and not NULL, it is substituted; otherwise, word
499 is printed on standard error (preceded by name:) and an error
500 occurs (normally causing termination of a shell script, function,
501 or script sourced using the ‘.’ built-in). If word is omitted,
502 the string “parameter null or not set” is used instead. Cur‐
503 rently a bug, if word is a variable which expands to the null
504 string, the error message is also printed.
505 In the above modifiers, the ‘:’ can be omitted, in which case the condi‐
507 tions only depend on name being set (as opposed to set and not NULL). If
508 word is needed, parameter, command, arithmetic, and tilde substitution
509 are performed on it; if word is not needed, it is not evaluated.
510 The following forms of parameter substitution can also be used:
512 ${#name}
514 The number of positional parameters if name is ‘*’, ‘@’, or not
515 specified; otherwise the length of the string value of parameter
516 name.
517 ${#name[*]}
519 ${#name[@]}
520 The number of elements in the array name.
521 ${name#pattern}
523 ${name##pattern}
524 If pattern matches the beginning of the value of parameter name,
525 the matched text is deleted from the result of substitution. A
526 single ‘#’ results in the shortest match, and two of them result
527 in the longest match.
528 ${name%pattern}
530 ${name%%pattern}
531 Like ${..#..} substitution, but it deletes from the end of the
532 value.
533 ${name/pattern/string}
535 ${name//pattern/string}
536 Like ${..#..} substitution, but it replaces the longest match of
537 pattern, anchored anywhere in the value, with string. If pattern
538 begins with ‘#’, it is anchored at the beginning of the value; if
539 it begins with ‘%’, it is anchored at the end. A single ‘/’
540 replaces the first occurence of the search pattern, and two of
541 them replace all occurences. If /string is omitted, the pattern
542 is replaced by the empty string, i.e. deleted.
543 ${name:pos:len}
545 The first lenbytes of name,starting at position pos,are substi‐
546 tuted. Both posand :lenare optional. If posis negative, count‐
547 ing starts at the end of the string; if it is omitted, it
548 defaults to 0. If lenis omitted or greater than the length of
549 the remaining string, all of it is substituted. Both posand
550 lenare evaluated as arithmetic expressions. Currently, posmust
551 start with a space, opening parenthesis or digit to be recog‐
552 nised.
553 The following special parameters are implicitly set by the shell and can‐
555 not be set directly using assignments:
556 ! Process ID of the last background process started. If no back‐
558 ground processes have been started, the parameter is not set.
559 # The number of positional parameters ($1, $2, etc.).
561 $ The PID of the shell, or the PID of the original shell if it is
563 a subshell. Do NOTuse this mechanism for generating temporary
564 file names; see mktemp(1)instead.
565 - The concatenation of the current single letter options (see the
567 setcommand below for a list of options).
568 ? The exit status of the last non-asynchronous command executed.
570 If the last command was killed by a signal, $?is set to 128 plus
571 the signal number.
572 0 The name of the shell, determined as follows: the first argument
574 to mkshif it was invoked with the -coption and arguments were
575 given; otherwise the fileargument, if it was supplied; or else
576 the basename the shell was invoked with (i.e. argv[0]).$0is also
577 set to the name of the current script or the name of the current
578 function, if it was defined with the functionkeyword (i.e. a
579 Korn shell style function).
580 1...9 The first nine positional parameters that were supplied to the
582 shell, function, or script sourced using the ‘.’built-in. Fur‐
583 ther positional parameters may be accessed using ${number}.
584 * All positional parameters (except parameter 0) i.e. $1, $2, $3,
586 ... If used outside of double quotes, parameters are separate
587 words (which are subjected to word splitting); if used within
588 double quotes, parameters are separated by the first character
589 of the IFSparameter (or the empty string if IFSis NULL).
590 @ Same as $*,unless it is used inside double quotes, in which case
592 a separate word is generated for each positional parameter. If
593 there are no positional parameters, no word is generated. $@can
594 be used to access arguments, verbatim, without losing
595 NULLarguments or splitting arguments with spaces.
596 The following parameters are set and/or used by the shell:
598 _(underscore)
600 When an external command is executed by the shell, this param‐
601 eter is set in the environment of the new process to the path
602 of the executed command. In interactive use, this parameter
603 is also set in the parent shell to the last word of the previ‐
604 ous command.
605 CDPATH Search path for the cdbuilt-in command. It works the same way
607 as PATHfor those directories not beginning with ‘/’in
608 cdcommands. Note that if CDPATHis set and does not contain
609 ‘.’or contains an empty path, the current directory is not
610 searched. Also, the cdbuilt-in command will display the
611 resulting directory when a match is found in any search path
612 other than the empty path.
613 COLUMNS Set to the number of columns on the terminal or window. Cur‐
615 rently set to the “cols”value as reported by stty(1)if that
616 value is non-zero. This parameter is used by the interactive
617 line editing modes, and by the select,set-o,and kill-lcommands
618 to format information columns.
619 ENV If this parameter is found to be set after any profile files
621 are executed, the expanded value is used as a shell startup
622 file. It typically contains function and alias definitions.
623 ERRNO Integer value of the shell's errnovariable. It indicates the
625 reason the last system call failed. Not yet implemented.
626 EXECSHELL If set, this parameter is assumed to contain the shell that is
628 to be used to execute commands that execve(2)fails to execute
629 and which do not start with a “#!shell”sequence.
630 FCEDIT The editor used by the fccommand (see below).
632 FPATH Like PATH,but used when an undefined function is executed to
634 locate the file defining the function. It is also searched
635 when a command can't be found using PATH.See Functionsbelow
636 for more information.
637 HISTFILE The name of the file used to store command history. When
639 assigned to, history is loaded from the specified file. Also,
640 several invocations of the shell running on the same machine
641 will share history if their HISTFILEparameters all point to
642 the same file.
643 Note:If HISTFILEisn't set, no history file is used. This is
645 different from AT&T UNIXksh.
646 HISTSIZE The number of commands normally stored for history. The
648 default is 500.
649 HOME The default directory for the cdcommand and the value substi‐
651 tuted for an unqualified ~(see Tildeexpansionbelow).
652 IFS Internal field separator, used during substitution and by the
654 readcommand, to split values into distinct arguments; normally
655 set to space, tab, and newline. See Substitutionabove for
656 details.
657 Note:This parameter is not imported from the environment when
659 the shell is started.
660 KSH_VERSION
662 The name and version of the shell (read-only). See also the
663 version commands in Emacseditingmodeand Vieditingmodesections,
664 below.
665 LINENO The line number of the function or shell script that is cur‐
667 rently being executed.
668 LINES Set to the number of lines on the terminal or window.
670 OLDPWD The previous working directory. Unset if cdhas not success‐
672 fully changed directories since the shell started, or if the
673 shell doesn't know where it is.
674 OPTARG When using getopts,it contains the argument for a parsed
676 option, if it requires one.
677 OPTIND The index of the next argument to be processed by
679 getopts.Assigning 1 to this parameter causes getoptsto process
680 arguments from the beginning the next time it is invoked.
681 PATH A colon separated list of directories that are searched when
683 looking for commands and files sourced using the ‘.’command
684 (see below). An empty string resulting from a leading or
685 trailing colon, or two adjacent colons, is treated as a
686 ‘.’(the current directory).
687 PPID The process ID of the shell's parent (read-only).
689 PS1 The primary prompt for interactive shells. Parameter, com‐
691 mand, and arithmetic substitutions are performed, and ‘!’is
692 replaced with the current command number (see the fccommand
693 below). A literal ‘!’can be put in the prompt by placing
694 ‘!!’in PS1.
695 The default prompt is ‘$ ’for non-root users, ‘# ’for root.
697 If mkshis invoked by root and PS1does not contain a
698 ‘#’character, the default value will be used even if
699 PS1already exists in the environment.
700 The mkshdistribution comes with a sample dot.mkshrccontaining
702 a sophisticated example, but you might like the following one
703 (note that ${HOSTNAME:=$(hostname -s)} and the root-vs-user
704 distinguishing clause are (in this example) executed at
705 PS1assignment time, while the $USER and $PWD are escaped and
706 thus will be evaluated each time a prompt is displayed):
707 PS1='${USER:=$(id -un)}'"@${HOSTNAME:=$(hostname -s)}:\$PWD $(
709 if (( $(id -u) )); then print \$; else print \#; fi) "
710 Note that since the command-line editors try to figure out how
712 long the prompt is (so they know how far it is to the edge of
713 the screen), escape codes in the prompt tend to mess things
714 up. You can tell the shell not to count certain sequences
715 (such as escape codes) by prefixing your prompt with a charac‐
716 ter (such as control-A) followed by a carriage return and then
717 delimiting the escape codes with this character. Any
718 occurences of that character in the prompt are not printed.
719 By the way, don't blame me for this hack; it's derived from
720 the original ksh88(1),which did print the delimiter character
721 so you were out of luck if you did not have any non-printing
722 characters.
723 Since Backslashes and other special characters may be inter‐
725 preted by the shell, to set PS1either escape the backslash
726 itself, or use double quotes. The latter is more practical.
727 This is a more complex example, avoiding to directly enter
728 special characters (for example with ^Vin the emacs editing
729 mode), which embeds the current working directory, in reverse
730 video, in the prompt string:
731 x=$(print \\001)
733 PS1="$x$(print \\r)$x$(tput smso)$x\$PWD$x$(tput rmso)$x> "
734 PS2 Secondary prompt string, by default ‘> ’,used when more input
736 is needed to complete a command.
737 PS3 Prompt used by the selectstatement when reading a menu selec‐
739 tion. The default is ‘#? ’.
740 PS4 Used to prefix commands that are printed during execution
742 tracing (see the set-xcommand below). Parameter, command, and
743 arithmetic substitutions are performed before it is printed.
744 The default is ‘+ ’.
745 PWD The current working directory. May be unset or NULLif the
747 shell doesn't know where it is.
748 RANDOM Every time RANDOMis referenced, it is assigned a 15-bit
750 pseudo-random number, i.e. between 0 and 32767, first. See
751 the description of set-oarc4randombelow for details.
752 REPLY Default parameter for the readcommand if no names are given.
754 Also used in selectloops to store the value that is read from
755 standard input.
756 SECONDS The number of seconds since the shell started or, if the
758 parameter has been assigned an integer value, the number of
759 seconds since the assignment plus the value that was assigned.
760 TMOUT If set to a positive integer in an interactive shell, it spec‐
762 ifies the maximum number of seconds the shell will wait for
763 input after printing the primary prompt (PS1).If the time is
764 exceeded, the shell exits.
765 TMPDIR The directory temporary shell files are created in. If this
767 parameter is not set, or does not contain the absolute path of
768 a writable directory, temporary files are created in /tmp.
769 Tildeexpansion
771 Tilde expansion which is done in parallel with parameter substitution, is
772 done on words starting with an unquoted ‘~’.The characters following the
773 tilde, up to the first ‘/’,if any, are assumed to be a login name. If
774 the login name is empty, ‘+’,or ‘-’,the value of the HOME,PWD,or
775 OLDPWDparameter is substituted, respectively. Otherwise, the password
776 file is searched for the login name, and the tilde expression is substi‐
777 tuted with the user's home directory. If the login name is not found in
778 the password file or if any quoting or parameter substitution occurs in
779 the login name, no substitution is performed.
780 In parameter assignments (such as those preceding a simple-command or
782 those occurring in the arguments of alias,export,readonly,and
783 typeset),tilde expansion is done after any assignment (i.e. after the
784 equals sign) or after an unquoted colon (‘:’);login names are also delim‐
785 ited by colons.
786 The home directory of previously expanded login names are cached and re-
788 used. The alias-dcommand may be used to list, change, and add to this
789 cache (e.g. alias-dfac=/usr/local/facilities;cd~fac/bin).
790 Braceexpansion(alteration)
792 Brace expressions take the following form:
793 prefix{str1,...,strN}suffix
795 The expressions are expanded to N words, each of which is the concatena‐
797 tion of prefix, stri, and suffix (e.g. “a{c,b{X,Y},d}e” expands to four
798 words: “ace”, “abXe”, “abYe”, and “ade”). As noted in the example, brace
799 expressions can be nested and the resulting words are not sorted. Brace
800 expressions must contain an unquoted comma (‘,’) for expansion to occur
801 (e.g. {} and {foo} are not expanded). Brace expansion is carried out
802 after parameter substitution and before file name generation.
803 Filenamepatterns
805 A file name pattern is a word containing one or more unquoted ‘?’, ‘*’,
806 ‘+’, ‘@’, or ‘!’ characters or “[..]” sequences. Once brace expansion
807 has been performed, the shell replaces file name patterns with the sorted
808 names of all the files that match the pattern (if no files match, the
809 word is left unchanged). The pattern elements have the following mean‐
810 ing:
811 ? Matches any single character.
813 * Matches any sequence of characters.
815 [..] Matches any of the characters inside the brackets. Ranges of
817 characters can be specified by separating two characters by a ‘-’
818 (e.g. “[a0-9]” matches the letter ‘a’ or any digit). In order to
819 represent itself, a ‘-’ must either be quoted or the first or
820 last character in the character list. Similarly, a ‘]’ must be
821 quoted or the first character in the list if it is to represent
822 itself instead of the end of the list. Also, a ‘!’ appearing at
823 the start of the list has special meaning (see below), so to rep‐
824 resent itself it must be quoted or appear later in the list.
825 [!..] Like [..], except it matches any character not inside the brack‐
827 ets.
828 *(pattern|...|pattern)
830 Matches any string of characters that matches zero or more occur‐
831 rences of the specified patterns. Example: The pattern
832 *(foo|bar) matches the strings “”, “foo”, “bar”, “foobarfoo”,
833 etc.
834 +(pattern|...|pattern)
836 Matches any string of characters that matches one or more occur‐
837 rences of the specified patterns. Example: The pattern
838 +(foo|bar) matches the strings “foo”, “bar”, “foobar”, etc.
839 ?(pattern|...|pattern)
841 Matches the empty string or a string that matches one of the
842 specified patterns. Example: The pattern ?(foo|bar) only matches
843 the strings “”, “foo”, and “bar”.
844 @(pattern|...|pattern)
846 Matches a string that matches one of the specified patterns.
847 Example: The pattern @(foo|bar) only matches the strings “foo”
848 and “bar”.
849 !(pattern|...|pattern)
851 Matches any string that does not match one of the specified pat‐
852 terns. Examples: The pattern !(foo|bar) matches all strings
853 except “foo” and “bar”; the pattern !(*) matches no strings; the
854 pattern !(?)* matches all strings (think about it).
855 Note that mksh (andpdksh) never matches ‘.’ and ‘..’, but AT&T UNIX ksh,
857 Bourne sh, and GNU bash do.
858 Note that none of the above pattern elements match either a period (‘.’)
860 at the start of a file name or a slash (‘/’), even if they are explicitly
861 used in a [..] sequence; also, the names ‘.’ and ‘..’ are never matched,
862 even by the pattern ‘.*’.
863 If the markdirs option is set, any directories that result from file name
865 generation are marked with a trailing ‘/’.
866 The POSIX character classes (i.e. [:class-name:] inside a [..] expres‐
868 sion) are not yet implemented.
869 Input/outputredirection
871 When a command is executed, its standard input, standard output, and
872 standard error (file descriptors 0, 1, and 2, respectively) are normally
873 inherited from the shell. Three exceptions to this are commands in pipe‐
874 lines, for which standard input and/or standard output are those set up
875 by the pipeline, asynchronous commands created when job control is dis‐
876 abled, for which standard input is initially set to be from /dev/null,
877 and commands for which any of the following redirections have been speci‐
878 fied:
879 >file Standard output is redirected to file. If file does not exist,
881 it is created; if it does exist, is a regular file, and the
882 noclobber option is set, an error occurs; otherwise, the file is
883 truncated. Note that this means the command cmd<foo>foo will
884 open foo for reading and then truncate it when it opens it for
885 writing, before cmd gets a chance to actually read foo.
886 >|file Same as >, except the file is truncated, even if the noclobber
888 option is set.
889 >>file Same as >, except if file exists it is appended to instead of
891 being truncated. Also, the file is opened in append mode, so
892 writes always go to the end of the file (see open(2)).
893 <file Standard input is redirected from file, which is opened for read‐
895 ing.
896 <>file Same as <, except the file is opened for reading and writing.
898 <<marker
900 After reading the command line containing this kind of redirect‐
901 ion (called a “heredocument”), the shell copies lines from the
902 command source into a temporary file until a line matching marker
903 is read. When the command is executed, standard input is redi‐
904 rected from the temporary file. If marker contains no quoted
905 characters, the contents of the temporary file are processed as
906 if enclosed in double quotes each time the command is executed,
907 so parameter, command, and arithmetic substitutions are per‐
908 formed, along with backslash (‘\’) escapes for ‘$’, ‘`’, ‘\’, and
909 ‘\newline’, but not for ‘"’. If multiple here documents are used
910 on the same command line, they are saved in order.
911 <<-marker
913 Same as <<, except leading tabs are stripped from lines in the
914 here document.
915 <<<word
917 Same as <<, except that word is the here document. This is
918 called a here string.
919 <&fd Standard input is duplicated from file descriptor fd. fd can be
921 a single digit, indicating the number of an existing file
922 descriptor; the letter ‘p’, indicating the file descriptor asso‐
923 ciated with the output of the current co-process; or the charac‐
924 ter ‘-’, indicating standard input is to be closed.
925 >&fd Same as <&, except the operation is done on standard output.
927 In any of the above redirections, the file descriptor that is redirected
929 (i.e. standard input or standard output) can be explicitly given by pre‐
930 ceding the redirection with a single digit. Parameter, command, and
931 arithmetic substitutions, tilde substitutions, and (if the shell is
932 interactive) file name generation are all performed on the file, marker,
933 and fd arguments of redirections. Note, however, that the results of any
934 file name generation are only used if a single file is matched; if multi‐
935 ple files match, the word with the expanded file name generation charac‐
936 ters is used. Note that in restricted shells, redirections which can
937 create files cannot be used.
938 For simple-commands, redirections may appear anywhere in the command; for
940 compound-commands (if statements, etc.), any redirections must appear at
941 the end. Redirections are processed after pipelines are created and in
942 the order they are given, so the following will print an error with a
943 line number prepended to it:
944 $cat/foo/bar2>&1>/dev/null|cat-n
946 Arithmeticexpressions
948 Integer arithmetic expressions can be used with the let command, inside
949 $((..)) expressions, inside array references (e.g. name[expr]), as
950 numeric arguments to the test command, and as the value of an assignment
951 to an integer parameter.
952 Expressions may contain alpha-numeric parameter identifiers, array refer‐
954 ences, and integer constants and may be combined with the following C
955 operators (listed and grouped in increasing order of precedence):
956 Unary operators:
958 + - ! ~ ++ --
960 Binary operators:
962 ,
964 = *= /= %= += -= <<= >>= &= ^= |=
965 ||
966 &&
967 |
968 ^
969 &
970 == !=
971 < <= >= >
972 << >>
973 + -
974 * / %
975 Ternary operators:
977 ?: (precedence is immediately higher than assignment)
979 Grouping operators:
981 ( )
983 Integer constants may be specified with arbitrary bases using the nota‐
985 tion base#number, where base is a decimal integer specifying the base,
986 and number is a number in the specified base. Additionally, integers may
987 be prefixed with ‘0X’ or ‘0x’ (specifying base 16), similar to AT&T UNIX
988 ksh, or ‘0’ (base 8), as an mksh extension, in all forms of arithmetic
989 expressions, except as numeric arguments to the test command.
990 The operators are evaluated as follows:
992 unary+ Result is the argument (included for completeness).
994 unary- Negation.
996 ! Logical NOT; the result is 1 if argument is zero, 0 if not.
998 ~ Arithmetic (bit-wise) NOT.
1000 ++ Increment; must be applied to a parameter (not a literal or
1002 other expression). The parameter is incremented by 1.
1003 When used as a prefix operator, the result is the incre‐
1004 mented value of the parameter; when used as a postfix oper‐
1005 ator, the result is the original value of the parameter.
1006 -- Similar to ++, except the parameter is decremented by 1.
1008 , Separates two arithmetic expressions; the left-hand side is
1010 evaluated first, then the right. The result is the value
1011 of the expression on the right-hand side.
1012 = Assignment; the variable on the left is set to the value on
1014 the right.
1015 *=/=+=-=<<= >>=&=^=|=
1017 Assignment operators. ⟨var⟩⟨op⟩=⟨expr⟩ is the same as
1018 ⟨var⟩=⟨var⟩⟨op⟩⟨expr⟩, with any operator precedence in
1019 ⟨expr⟩ preserved. For example, “var1*=5+3” is the same as
1020 specifying “var1=var1*(5+3)”.
1021 || Logical OR; the result is 1 if either argument is non-zero,
1023 0 if not. The right argument is evaluated only if the left
1024 argument is zero.
1025 && Logical AND; the result is 1 if both arguments are non-
1027 zero, 0 if not. The right argument is evaluated only if
1028 the left argument is non-zero.
1029 | Arithmetic (bit-wise) OR.
1031 ^ Arithmetic (bit-wise) XOR (exclusive-OR).
1033 & Arithmetic (bit-wise) AND.
1035 == Equal; the result is 1 if both arguments are equal, 0 if
1037 not.
1038 != Not equal; the result is 0 if both arguments are equal, 1
1040 if not.
1041 < Less than; the result is 1 if the left argument is less
1043 than the right, 0 if not.
1044 <=>=> Less than or equal, greater than or equal, greater than.
1046 See <.
1047 <<>> Shift left (right); the result is the left argument with
1049 its bits shifted left (right) by the amount given in the
1050 right argument.
1051 +-*/ Addition, subtraction, multiplication, and division.
1053 % Remainder; the result is the remainder of the division of
1055 the left argument by the right. The sign of the result is
1056 unspecified if either argument is negative.
1057 ⟨arg1⟩?⟨arg2⟩:⟨arg3⟩
1059 If ⟨arg1⟩ is non-zero, the result is ⟨arg2⟩; otherwise the
1060 result is ⟨arg3⟩.
1061 Co-processes
1063 A co-process (which is a pipeline created with the ‘|&’ operator) is an
1064 asynchronous process that the shell can both write to (using print-p) and
1065 read from (using read-p). The input and output of the co-process can
1066 also be manipulated using >&p and <&p redirections, respectively. Once a
1067 co-process has been started, another can't be started until the co-
1068 process exits, or until the co-process's input has been redirected using
1069 an execn>&p redirection. If a co-process's input is redirected in this
1070 way, the next co-process to be started will share the output with the
1071 first co-process, unless the output of the initial co-process has been
1072 redirected using an execn<&p redirection.
1073 Some notes concerning co-processes:
1075 · The only way to close the co-process's input (so the co-process reads
1077 an end-of-file) is to redirect the input to a numbered file descrip‐
1078 tor and then close that file descriptor: exec3>&p;exec3>&-
1079 · In order for co-processes to share a common output, the shell must
1081 keep the write portion of the output pipe open. This means that end-
1082 of-file will not be detected until all co-processes sharing the co-
1083 process's output have exited (when they all exit, the shell closes
1084 its copy of the pipe). This can be avoided by redirecting the output
1085 to a numbered file descriptor (as this also causes the shell to close
1086 its copy). Note that this behaviour is slightly different from the
1087 original Korn shell which closes its copy of the write portion of the
1088 co-process output when the most recently started co-process (instead
1089 of when all sharing co-processes) exits.
1090 · print-p will ignore SIGPIPE signals during writes if the signal is
1092 not being trapped or ignored; the same is true if the co-process
1093 input has been duplicated to another file descriptor and print-un is
1094 used.
1095 Functions
1097 Functions are defined using either Korn shell functionfunction-name syn‐
1098 tax or the Bourne/POSIX shell function-name() syntax (see below for the
1099 difference between the two forms). Functions are like .‐scripts (i.e.
1100 scripts sourced using the ‘.’ built-in) in that they are executed in the
1101 current environment. However, unlike .‐scripts, shell arguments (i.e.
1102 positional parameters $1, $2, etc.) are never visible inside them. When
1103 the shell is determining the location of a command, functions are
1104 searched after special built-in commands, before regular and non-regular
1105 built-ins, and before the PATH is searched.
1106 An existing function may be deleted using unset-ffunction-name. A list
1108 of functions can be obtained using typeset+f and the function definitions
1109 can be listed using typeset-f. The autoload command (which is an alias
1110 for typeset-fu) may be used to create undefined functions: when an unde‐
1111 fined function is executed, the shell searches the path specified in the
1112 FPATH parameter for a file with the same name as the function which, if
1113 found, is read and executed. If after executing the file the named func‐
1114 tion is found to be defined, the function is executed; otherwise, the
1115 normal command search is continued (i.e. the shell searches the regular
1116 built-in command table and PATH). Note that if a command is not found
1117 using PATH, an attempt is made to autoload a function using FPATH (this
1118 is an undocumented feature of the original Korn shell).
1119 Functions can have two attributes, “trace” and “export”, which can be set
1121 with typeset-ft and typeset-fx, respectively. When a traced function is
1122 executed, the shell's xtrace option is turned on for the function's dura‐
1123 tion; otherwise, the xtrace option is turned off. The “export” attribute
1124 of functions is currently not used. In the original Korn shell, exported
1125 functions are visible to shell scripts that are executed.
1126 Since functions are executed in the current shell environment, parameter
1128 assignments made inside functions are visible after the function com‐
1129 pletes. If this is not the desired effect, the typeset command can be
1130 used inside a function to create a local parameter. Note that special
1131 parameters (e.g. $$,$!) can't be scoped in this way.
1132 The exit status of a function is that of the last command executed in the
1134 function. A function can be made to finish immediately using the return
1135 command; this may also be used to explicitly specify the exit status.
1136 Functions defined with the function reserved word are treated differently
1138 in the following ways from functions defined with the () notation:
1139 · The $0 parameter is set to the name of the function (Bourne-style
1141 functions leave $0 untouched).
1142 · Parameter assignments preceding function calls are not kept in the
1144 shell environment (executing Bourne-style functions will keep assign‐
1145 ments).
1146 · OPTIND is saved/reset and restored on entry and exit from the func‐
1148 tion so getopts can be used properly both inside and outside the
1149 function (Bourne-style functions leave OPTIND untouched, so using
1150 getopts inside a function interferes with using getopts outside the
1151 function).
1152 In the future, the following differences will also be added:
1154 · A separate trap/signal environment will be used during the execution
1156 of functions. This will mean that traps set inside a function will
1157 not affect the shell's traps and signals that are not ignored in the
1158 shell (but may be trapped) will have their default effect in a func‐
1159 tion.
1160 · The EXIT trap, if set in a function, will be executed after the func‐
1162 tion returns.
1163 Commandexecution
1165 After evaluation of command-line arguments, redirections, and parameter
1166 assignments, the type of command is determined: a special built-in, a
1167 function, a regular built-in, or the name of a file to execute found
1168 using the PATH parameter. The checks are made in the above order. Spe‐
1169 cial built-in commands differ from other commands in that the PATH param‐
1170 eter is not used to find them, an error during their execution can cause
1171 a non-interactive shell to exit, and parameter assignments that are spec‐
1172 ified before the command are kept after the command completes. Regular
1173 built-in commands are different only in that the PATH parameter is not
1174 used to find them.
1175 The original ksh and POSIX differ somewhat in which commands are consid‐
1177 ered special or regular:
1178 POSIX special commands
1180 .,:,break,continue, eval,exec,exit,export, readonly,return,set,shift,
1182 trap,unset
1183 Additional mksh special commands
1185 builtin,times,typeset
1187 Very special commands (non-POSIX)
1189 alias,readonly,set,typeset
1191 POSIX regular commands
1193 alias,bg,cd,command, false,fc,fg,getopts, jobs,kill,read,true,
1195 umask,unalias,wait
1196 Additional mksh regular commands
1198 [,echo,let,mknod, print,pwd,test,ulimit, whence
1200 In the future, the additional mksh special and regular commands may be
1202 treated differently from the POSIX special and regular commands.
1203 Once the type of command has been determined, any command-line parameter
1205 assignments are performed and exported for the duration of the command.
1206 The following describes the special and regular built-in commands:
1208 .file[arg...]
1210 This is called the “dot” command. Execute the commands in file
1211 in the current environment. The file is searched for in the
1212 directories of PATH. If arguments are given, the positional
1213 parameters may be used to access them while file is being exe‐
1214 cuted. If no arguments are given, the positional parameters are
1215 those of the environment the command is used in.
1216 :[...] The null command. Exit status is set to zero.
1218 alias [-d|-t[-r]| +-x] [-p] [+] [name [=value] ...]
1220 Without arguments, alias lists all aliases. For any name without
1221 a value, the existing alias is listed. Any name with a value
1222 defines an alias (see Aliases above).
1223 When listing aliases, one of two formats is used. Normally,
1225 aliases are listed as name=value, where value is quoted. If
1226 options were preceded with ‘+’, or a lone ‘+’ is given on the
1227 command line, only name is printed.
1228 The -d option causes directory aliases which are used in tilde
1230 expansion to be listed or set (see Tildeexpansion above).
1231 If the -p option is used, each alias is prefixed with the string
1233 “alias ”.
1234 The -t option indicates that tracked aliases are to be listed/set
1236 (values specified on the command line are ignored for tracked
1237 aliases). The -r option indicates that all tracked aliases are
1238 to be reset.
1239 The -x option sets (+xclears) the export attribute of an alias,
1241 or, if no names are given, lists the aliases with the export
1242 attribute (exporting an alias has no effect).
1243 bg[job...]
1245 Resume the specified stopped job(s) in the background. If no
1246 jobs are specified, %+ is assumed. See Jobcontrol below for more
1247 information.
1248 bind[-l]
1250 The current bindings are listed. If the -l flag is given, bind
1251 instead lists the names of the functions to which keys may be
1252 bound. See Emacseditingmode for more information.
1253 bind[-m] string=[substitute] ...
1255 bind string=[editing-command] ...
1256 The specified editing command is bound to the given string, which
1257 should consist of a control character optionally preceded by one
1258 of the two prefix characters and optionally succeded by a tilde
1259 character. Future input of the string will cause the editing
1260 command to be immediately invoked. If the -m flag is given, the
1261 specified input string will afterwards be immediately replaced by
1262 the given substitute string which may contain editing commands.
1263 If a tilde postfix is given, a tilde trailing the one or two
1264 prefices and the control character is ignored, any other trailing
1265 character will be processed afterwards.
1266 Control characters may be written using caret notation i.e. ^X
1268 represents Control-X. Note that although only two prefix charac‐
1269 ters (usually ESC and ^X) are supported, some multi-character
1270 sequences can be supported.
1271 The following default bindings show how the arrow keys, the home,
1273 end and delete key on a BSD wsvt25, xterm-xfree86 or GNU screen
1274 terminal are bound (of course some escape sequences won't work
1275 out quite this nicely):
1276 bind '^[['=prefix-2
1278 bind '^XA'=up-history
1279 bind '^XB'=down-history
1280 bind '^XC'=forward-char
1281 bind '^XD'=backward-char
1282 bind '^X1~'=beginning-of-line
1283 bind '^X7~'=beginning-of-line
1284 bind '^XH'=beginning-of-line
1285 bind '^X4~'=end-of-line
1286 bind '^X8~'=end-of-line
1287 bind '^XF'=end-of-line
1288 bind '^X3~'=delete-char-forward
1289 break[level]
1291 Exit the levelth inner-most for, select, until, or while loop.
1292 level defaults to 1.
1293 builtincommand[arg...]
1295 Execute the built-in command command.
1296 cd [-LP] [dir]
1298 Set the working directory to dir. If the parameter CDPATH is
1299 set, it lists the search path for the directory containing dir.
1300 A NULL path means the current directory. If dir is found in any
1301 component of the CDPATH search path other than the NULL path, the
1302 name of the new working directory will be written to standard
1303 output. If dir is missing, the home directory HOME is used. If
1304 dir is ‘-’, the previous working directory is used (see the
1305 OLDPWD parameter).
1306 If the -L option (logical path) is used or if the physical option
1308 isn't set (see the set command below), references to ‘..’ in dir
1309 are relative to the path used to get to the directory. If the -P
1310 option (physical path) is used or if the physical option is set,
1311 ‘..’ is relative to the filesystem directory tree. The PWD and
1312 OLDPWD parameters are updated to reflect the current and old
1313 working directory, respectively.
1314 cd [-LP] oldnew
1316 The string new is substituted for old in the current directory,
1317 and the shell attempts to change to the new directory.
1318 command [-pVv] cmd [arg...]
1320 If neither the -v nor -V option is given, cmd is executed exactly
1321 as if command had not been specified, with two exceptions:
1322 firstly, cmd cannot be a shell function; and secondly, special
1323 built-in commands lose their specialness (i.e. redirection and
1324 utility errors do not cause the shell to exit, and command
1325 assignments are not permanent).
1326 If the -p option is given, a default search path is used instead
1328 of the current value of PATH, the actual value of which is system
1329 dependent.
1330 If the -v option is given, instead of executing cmd, information
1332 about what would be executed is given (and the same is done for
1333 arg...). For special and regular built-in commands and func‐
1334 tions, their names are simply printed; for aliases, a command
1335 that defines them is printed; and for commands found by searching
1336 the PATH parameter, the full path of the command is printed. If
1337 no command is found (i.e. the path search fails), nothing is
1338 printed and command exits with a non-zero status. The -V option
1339 is like the -v option, except it is more verbose.
1340 continue[level]
1342 Jumps to the beginning of the levelth inner-most for, select,
1343 until, or while loop. level defaults to 1.
1344 echo [-Een] [arg...]
1346 Prints its arguments (separated by spaces) followed by a newline,
1347 to the standard output. The newline is suppressed if any of the
1348 arguments contain the backslash sequence ‘\c’. See the print
1349 command below for a list of other backslash sequences that are
1350 recognised.
1351 The options are provided for compatibility with BSD shell
1353 scripts. The -n option suppresses the trailing newline, -e
1354 enables backslash interpretation (a no-op, since this is normally
1355 done), and -E suppresses backslash interpretation.
1356 evalcommand...
1358 The arguments are concatenated (with spaces between them) to form
1359 a single string which the shell then parses and executes in the
1360 current environment.
1361 exec [command[arg...]]
1363 The command is executed without forking, replacing the shell
1364 process.
1365 If no command is given except for I/O redirection, the I/O redi‐
1367 rection is permanent and the shell is not replaced. Any file
1368 descriptors greater than 2 which are opened or dup(2)'d in this
1369 way are not made available to other executed commands (i.e. com‐
1370 mands that are not built-in to the shell). Note that the Bourne
1371 shell differs here; it does pass these file descriptors on.
1372 exit[status]
1374 The shell exits with the specified exit status. If status is not
1375 specified, the exit status is the current value of the $? parame‐
1376 ter.
1377 export [-p] [parameter[=value]]
1379 Sets the export attribute of the named parameters. Exported
1380 parameters are passed in the environment to executed commands.
1381 If values are specified, the named parameters are also assigned.
1382 If no parameters are specified, the names of all parameters with
1384 the export attribute are printed one per line, unless the -p
1385 option is used, in which case export commands defining all
1386 exported parameters, including their values, are printed.
1387 false A command that exits with a non-zero status.
1389 fc [-eeditor| -l[-n]] [-r] [first[last]]
1391 first and last select commands from the history. Commands can be
1392 selected by history number or a string specifying the most recent
1393 command starting with that string. The -l option lists the com‐
1394 mand on standard output, and -n inhibits the default command num‐
1395 bers. The -r option reverses the order of the list. Without -l,
1396 the selected commands are edited by the editor specified with the
1397 -e option, or if no -e is specified, the editor specified by the
1398 FCEDIT parameter (if this parameter is not set, /bin/ed is used),
1399 and then executed by the shell.
1400 fc -e-|-s [-g] [old=new] [prefix]
1402 Re-execute the selected command (the previous command by default)
1403 after performing the optional substitution of old with new. If
1404 -g is specified, all occurrences of old are replaced with new.
1405 The meaning of -e- and -s is identical: re-execute the selected
1406 command without invoking an editor. This command is usually
1407 accessed with the predefined aliasr='fc-e-'.
1408 fg[job...]
1410 Resume the specified job(s) in the foreground. If no jobs are
1411 specified, %+ is assumed. See Jobcontrol below for more informa‐
1412 tion.
1413 getopts optstringname [arg...]
1415 Used by shell procedures to parse the specified arguments (or
1416 positional parameters, if no arguments are given) and to check
1417 for legal options. optstring contains the option letters that
1418 getopts is to recognise. If a letter is followed by a colon, the
1419 option is expected to have an argument. Options that do not take
1420 arguments may be grouped in a single argument. If an option
1421 takes an argument and the option character is not the last char‐
1422 acter of the argument it is found in, the remainder of the argu‐
1423 ment is taken to be the option's argument; otherwise, the next
1424 argument is the option's argument.
1425 Each time getopts is invoked, it places the next option in the
1427 shell parameter name and the index of the argument to be pro‐
1428 cessed by the next call to getopts in the shell parameter OPTIND.
1429 If the option was introduced with a ‘+’, the option placed in
1430 name is prefixed with a ‘+’. When an option requires an argu‐
1431 ment, getopts places it in the shell parameter OPTARG.
1432 When an illegal option or a missing option argument is encoun‐
1434 tered, a question mark or a colon is placed in name (indicating
1435 an illegal option or missing argument, respectively) and OPTARG
1436 is set to the option character that caused the problem. Further‐
1437 more, if optstring does not begin with a colon, a question mark
1438 is placed in name, OPTARG is unset, and an error message is
1439 printed to standard error.
1440 When the end of the options is encountered, getopts exits with a
1442 non-zero exit status. Options end at the first (non-option argu‐
1443 ment) argument that does not start with a ‘-’, or when a ‘--’
1444 argument is encountered.
1445 Option parsing can be reset by setting OPTIND to 1 (this is done
1447 automatically whenever the shell or a shell procedure is
1448 invoked).
1449 Warning: Changing the value of the shell parameter OPTIND to a
1451 value other than 1, or parsing different sets of arguments with‐
1452 out resetting OPTIND, may lead to unexpected results.
1453 hash [-r] [name...]
1455 Without arguments, any hashed executable command pathnames are
1456 listed. The -r option causes all hashed commands to be removed
1457 from the hash table. Each name is searched as if it were a com‐
1458 mand name and added to the hash table if it is an executable com‐
1459 mand.
1460 jobs [-lnp] [job...]
1462 Display information about the specified job(s); if no jobs are
1463 specified, all jobs are displayed. The -n option causes informa‐
1464 tion to be displayed only for jobs that have changed state since
1465 the last notification. If the -l option is used, the process ID
1466 of each process in a job is also listed. The -p option causes
1467 only the process group of each job to be printed. See Jobcontrol
1468 below for the format of job and the displayed job.
1469 kill [-ssigname| -signum| -signame] {job|pid|pgrp} ...
1471 Send the specified signal to the specified jobs, process IDs, or
1472 process groups. If no signal is specified, the TERM signal is
1473 sent. If a job is specified, the signal is sent to the job's
1474 process group. See Jobcontrol below for the format of job.
1475 kill -l [exit-status...]
1477 Print the signal name corresponding to exit-status. If no argu‐
1478 ments are specified, a list of all the signals, their numbers,
1479 and a short description of them are printed.
1480 let[expression...]
1482 Each expression is evaluated (see Arithmeticexpressions above).
1483 If all expressions are successfully evaluated, the exit status is
1484 0 (1) if the last expression evaluated to non-zero (zero). If an
1485 error occurs during the parsing or evaluation of an expression,
1486 the exit status is greater than 1. Since expressions may need to
1487 be quoted, ((expr)) is syntactic sugar for let"expr".
1488 mknod [-mmode] name [c|b] majorminor
1490 mknod [-mmode] name p
1491 Create a device special file. The file type may be b (block type
1492 device), c (character type device), or p (named pipe). The file
1493 created may be modified according to its mode (via the -m
1494 option), major (major device number), and minor (minor device
1495 number).
1496 See mknod(8) for further information.
1498 print [-nprsu[n]| -R[-en]] [argument...]
1500 print prints its arguments on the standard output, separated by
1501 spaces and terminated with a newline. The -n option suppresses
1502 the newline. By default, certain C escapes are translated.
1503 These include ‘\b’, ‘\f’, ‘\n’, ‘\r’, ‘\t’, ‘\u####’, ‘\v’,
1504 ‘\x##’, and ‘\0###’; ‘#’ is, in the case of \0###, an octal, or,
1505 in the case of \u#### or \x##, a hexadecimal digit, of which
1506 there may be 0 to 2/3/4. The \x## and \0### escapes translate to
1507 raw 8-bit octets; the \u#### escape translates a Unicode code‐
1508 point to UTF-8. ‘\c’ is equivalent to using the -n option. ‘\’
1509 expansion may be inhibited with the -r option. The -s option
1510 prints to the history file instead of standard output; the -u
1511 option prints to file descriptor n (n defaults to 1 if omitted);
1512 and the -p option prints to the co-process (see Co-processes
1513 above).
1514 The -R option is used to emulate, to some degree, the BSD echo(1)
1516 command which does not process ‘\’ sequences unless the -e option
1517 is given. As above, the -n option suppresses the trailing new‐
1518 line.
1519 pwd[-LP]
1521 Print the present working directory. If the -L option is used or
1522 if the physical option isn't set (see the set command below), the
1523 logical path is printed (i.e. the path used to cd to the current
1524 directory). If the -P option (physical path) is used or if the
1525 physical option is set, the path determined from the filesystem
1526 (by following ‘..’ directories to the root directory) is printed.
1527 read [-prsu[n]] [parameter...]
1529 Reads a line of input from the standard input, separates the line
1530 into fields using the IFS parameter (see Substitution above), and
1531 assigns each field to the specified parameters. If there are
1532 more parameters than fields, the extra parameters are set to
1533 NULL, or alternatively, if there are more fields than parameters,
1534 the last parameter is assigned the remaining fields (inclusive of
1535 any separating spaces). If no parameters are specified, the
1536 REPLY parameter is used. If the input line ends in a backslash
1537 and the -r option was not used, the backslash and the newline are
1538 stripped and more input is read. If no input is read, read exits
1539 with a non-zero status.
1540 The first parameter may have a question mark and a string
1542 appended to it, in which case the string is used as a prompt
1543 (printed to standard error before any input is read) if the input
1544 is a tty(4) (e.g. readnfoo?'numberoffoos:').
1545 The -un and -p options cause input to be read from file descrip‐
1547 tor n (n defaults to 0 if omitted) or the current co-process (see
1548 Co-processes above for comments on this), respectively. If the
1549 -s option is used, input is saved to the history file.
1550 Another handy set of tricks: If read is run in a loop such as
1552 whilereadfoo;do...;done then leading whitespace will be removed
1553 (IFS) and backslashes processed (-r). You might want to use
1554 whileIFS=read-rfoo;do...;done for pristine I/O (variable split‐
1555 ting, as in whileIFS=readfoobar;do...;done is not possible
1556 though).
1557 The inner loop will be executed in a subshell and variable
1559 changes cannot be propagated if executed in a pipeline:
1560 foo | bar | while read foo; do ...; done
1562 Use co-processes instead:
1564 foo | bar |&
1566 while read -p foo; do ...; done
1567 exec 3>&p; exec 3>&-
1568 readonly [-p] [parameter [=value] ...]
1570 Sets the read-only attribute of the named parameters. If values
1571 are given, parameters are set to them before setting the
1572 attribute. Once a parameter is made read-only, it cannot be
1573 unset and its value cannot be changed.
1574 If no parameters are specified, the names of all parameters with
1576 the read-only attribute are printed one per line, unless the -p
1577 option is used, in which case readonly commands defining all
1578 read-only parameters, including their values, are printed.
1579 renamefromto
1581 Renames the file from to to. Both must be complete pathnames and
1582 on the same device. This builtin is intended for emergency situ‐
1583 ations where /bin/mv becomes unusable, and directly calls
1584 rename(2).
1585 return[status]
1587 Returns from a function or . script, with exit status status. If
1588 no status is given, the exit status of the last executed command
1589 is used. If used outside of a function or . script, it has the
1590 same effect as exit. Note that mksh treats both profile and ENV
1591 files as . scripts, while the original Korn shell only treats
1592 profiles as . scripts.
1593 set[+-abCefhkmnpsuvXx] [+-ooption] [+-Aname] [--] [arg...]
1595 The set command can be used to set (-) or clear (+) shell
1596 options, set the positional parameters, or set an array parame‐
1597 ter. Options can be changed using the +-ooption syntax, where
1598 option is the long name of an option, or using the +-letter syn‐
1599 tax, where letter is the option's single letter name (not all
1600 options have a single letter name). The following table lists
1601 both option letters (if they exist) and long names along with a
1602 description of what the option does:
1603 -Aname Sets the elements of the array parameter name to
1605 arg... If -A is used, the array is reset (i.e.
1606 emptied) first; if +A is used, the first N ele‐
1607 ments are set (where N is the number of argu‐
1608 ments); the rest are left untouched.
1609 An alternative syntax for the command
1611 set-Afoo--abc which is compatible to GNU bash
1612 and also supported by AT&T UNIX ksh93 is:
1613 foo=(abc)
1614 -a|allexport All new parameters are created with the export
1616 attribute.
1617 -b|notify Print job notification messages asynchronously,
1619 instead of just before the prompt. Only used if
1620 job control is enabled (-m).
1621 -C|noclobber Prevent > redirection from overwriting existing
1623 files. Instead, >| must be used to force an
1624 overwrite.
1625 -e|errexit Exit (after executing the ERR trap) as soon as
1627 an error occurs or a command fails (i.e. exits
1628 with a non-zero status). This does not apply to
1629 commands whose exit status is explicitly tested
1630 by a shell construct such as if, until, while,
1631 &&, or || statements.
1632 -f|noglob Do not expand file name patterns.
1634 -h|trackall Create tracked aliases for all executed commands
1636 (see Aliases above). Enabled by default for
1637 non-interactive shells.
1638 -k|keyword Parameter assignments are recognised anywhere in
1640 a command.
1641 -m|monitor Enable job control (default for interactive
1643 shells).
1644 -n|noexec Do not execute any commands. Useful for check‐
1646 ing the syntax of scripts (ignored if interac‐
1647 tive).
1648 -p|privileged The shell is a privileged shell. It is set
1650 automatically if, when the shell starts, the
1651 real UID or GID does not match the effective UID
1652 (EUID) or GID (EGID), respectively. See above
1653 for a description of what this means.
1654 -s|stdin If used when the shell is invoked, commands are
1656 read from standard input. Set automatically if
1657 the shell is invoked with no arguments.
1658 When -s is used with the set command it causes
1660 the specified arguments to be sorted before
1661 assigning them to the positional parameters (or
1662 to array name, if -A is used).
1663 -U|utf8-hack Enable UTF-8 support in the Emacseditingmode.
1665 This is enabled automatically for interactive
1666 shells if your system supports
1667 setlocale(LC_CTYPE,"") and optionally
1668 nl_langinfo(CODESET), and at least one of these
1669 returns something that matches “UTF-8” or
1670 “utf8”, or if the input begins with a Byte Order
1671 Mark.
1672 -u|nounset Referencing of an unset parameter is treated as
1674 an error, unless one of the ‘-’, ‘+’, or ‘=’
1675 modifiers is used.
1676 -v|verbose Write shell input to standard error as it is
1678 read.
1679 -X|markdirs Mark directories with a trailing ‘/’ during file
1681 name generation.
1682 -x|xtrace Print commands and parameter assignments when
1684 they are executed, preceded by the value of PS4.
1685 arc4random Use arc4random(3) high-quality random numbers
1687 for the value of RANDOM if set (to either 1 or
1688 2), or a semi-predictable sequence from rand(3)
1689 if unset. Setting this flag will change its
1690 value to 1; the default value is 2, which means
1691 it automatically switches to 0 if RANDOM is
1692 written to.
1693 bgnice Background jobs are run with lower priority.
1695 braceexpand Enable brace expansion (a.k.a. alternation).
1697 This is enabled by default. If disabled, tilde
1698 expansion after an equals sign is disabled as a
1699 side effect.
1700 emacs Enable BRL emacs-like command-line editing
1702 (interactive shells only); see Emacseditingmode.
1703 gmacs Enable gmacs-like command-line editing (interac‐
1705 tive shells only). Currently identical to emacs
1706 editing except that transpose-chars (^T) acts
1707 slightly differently.
1708 ignoreeof The shell will not (easily) exit when end-of-
1710 file is read; exit must be used. To avoid infi‐
1711 nite loops, the shell will exit if EOF is read
1712 13 times in a row.
1713 interactive The shell is an interactive shell. This option
1715 can only be used when the shell is invoked. See
1716 above for a description of what this means.
1717 login The shell is a login shell. This option can
1719 only be used when the shell is invoked. See
1720 above for a description of what this means.
1721 nohup Do not kill running jobs with a SIGHUP signal
1723 when a login shell exits. Currently set by
1724 default, but this will change in the future to
1725 be compatible with AT&T UNIX ksh, which doesn't
1726 have this option, but does send the SIGHUP sig‐
1727 nal.
1728 nolog No effect. In the original Korn shell, this
1730 prevents function definitions from being stored
1731 in the history file.
1732 physical Causes the cd and pwd commands to use “physical”
1734 (i.e. the filesystem's) ‘..’ directories instead
1735 of “logical” directories (i.e. the shell handles
1736 ‘..’, which allows the user to be oblivious of
1737 symbolic links to directories). Clear by
1738 default. Note that setting this option does not
1739 affect the current value of the PWD parameter;
1740 only the cd command changes PWD. See the cd and
1741 pwd commands above for more details.
1742 posix Enable POSIX mode. Currently, this just turns
1744 off braceexpand mode when turned on, which can
1745 be turned back on manually.
1746 restricted The shell is a restricted shell. This option
1748 can only be used when the shell is invoked. See
1749 above for a description of what this means.
1750 vi Enable vi(1)-like command-line editing (interac‐
1752 tive shells only).
1753 vi-esccomplete In vi command-line editing, do command and file
1755 name completion when escape (^[) is entered in
1756 command mode.
1757 vi-tabcomplete In vi command-line editing, do command and file
1759 name completion when tab (^I) is entered in
1760 insert mode. This is the default.
1761 viraw No effect. In the original Korn shell, unless
1763 viraw was set, the vi command-line mode would
1764 let the tty(4) driver do the work until ESC (^[)
1765 was entered. mksh is always in viraw mode.
1766 These options can also be used upon invocation of the shell. The
1768 current set of options (with single letter names) can be found in
1769 the parameter ‘$-’. set-o with no option name will list all the
1770 options and whether each is on or off; set+o will print the long
1771 names of all options that are currently on.
1772 Remaining arguments, if any, are positional parameters and are
1774 assigned, in order, to the positional parameters (i.e. $1, $2,
1775 etc.). If options end with ‘--’ and there are no remaining argu‐
1776 ments, all positional parameters are cleared. If no options or
1777 arguments are given, the values of all names are printed. For
1778 unknown historical reasons, a lone ‘-’ option is treated spe‐
1779 cially – it clears both the -x and -v options.
1780 shift[number]
1782 The positional parameters number+1, number+2, etc. are renamed to
1783 ‘1’, ‘2’, etc. number defaults to 1.
1784 sourcefile[arg...]
1786 Like .(“dot”), except that the current working directory is
1787 appended to the PATH in GNU bash and mksh. In ksh93 and mksh,
1788 this is implemented as a shell alias instead of a builtin.
1789 testexpression
1791 [expression]
1792 test evaluates the expression and returns zero status if true, 1
1793 if false, or greater than 1 if there was an error. It is nor‐
1794 mally used as the condition command of if and while statements.
1795 Symbolic links are followed for all file expressions except -h
1796 and -L.
1797 The following basic expressions are available:
1799 -afile file exists.
1801 -bfile file is a block special device.
1803 -cfile file is a character special device.
1805 -dfile file is a directory.
1807 -efile file exists.
1809 -ffile file is a regular file.
1811 -Gfile file's group is the shell's effective group
1813 ID.
1814 -gfile file's mode has the setgid bit set.
1816 -hfile file is a symbolic link.
1818 -kfile file's mode has the sticky(8) bit set.
1820 -Lfile file is a symbolic link.
1822 -Ofile file's owner is the shell's effective user ID.
1824 -ooption Shell option is set (see the set command above
1826 for a list of options). As a non-standard
1827 extension, if the option starts with a ‘!’,
1828 the test is negated; the test always fails if
1829 option doesn't exist (so [ -o foo -o -o !foo ]
1830 returns true if and only if option foo
1831 exists).
1832 -pfile file is a named pipe.
1834 -rfile file exists and is readable.
1836 -Sfile file is a unix(4)-domain socket.
1838 -sfile file is not empty.
1840 -t[fd] File descriptor fd is a tty(4) device. fd may
1842 be left out, in which case it is taken to be
1843 1.
1844 -ufile file's mode has the setuid bit set.
1846 -wfile file exists and is writable.
1848 -xfile file exists and is executable.
1850 file1-ntfile2 file1 is newer than file2 or file1 exists and
1852 file2 does not.
1853 file1-otfile2 file1 is older than file2 or file2 exists and
1855 file1 does not.
1856 file1-effile2 file1 is the same file as file2.
1858 string string has non-zero length.
1860 -nstring string is not empty.
1862 -zstring string is empty.
1864 string=string Strings are equal.
1866 string==string Strings are equal.
1868 string>string First string operand is greater than second
1870 string operand.
1871 string<string First string operand is less than second
1873 string operand.
1874 string!=string Strings are not equal.
1876 number-eqnumber Numbers compare equal.
1878 number-nenumber Numbers compare not equal.
1880 number-genumber Numbers compare greater than or equal.
1882 number-gtnumber Numbers compare greater than.
1884 number-lenumber Numbers compare less than or equal.
1886 number-ltnumber Numbers compare less than.
1888 The above basic expressions, in which unary operators have prece‐
1890 dence over binary operators, may be combined with the following
1891 operators (listed in increasing order of precedence):
1892 expr -o expr Logical OR.
1894 expr -a expr Logical AND.
1895 ! expr Logical NOT.
1896 ( expr ) Grouping.
1897 Note that some special rules are applied (courtesy of POSIX) if
1899 the number of arguments to test or [...] is less than five: if
1900 leading ‘!’ arguments can be stripped such that only one argument
1901 remains then a string length test is performed (again, even if
1902 the argument is a unary operator); if leading ‘!’ arguments can
1903 be stripped such that three arguments remain and the second argu‐
1904 ment is a binary operator, then the binary operation is performed
1905 (even if the first argument is a unary operator, including an
1906 unstripped ‘!’).
1907 Note: A common mistake is to use “if[$foo=bar]” which fails if
1909 parameter “foo” is NULL or unset, if it has embedded spaces (i.e.
1910 IFS characters), or if it is a unary operator like ‘!’ or ‘-n’.
1911 Use tests like “if[x"$foo"=x"bar"]” instead, or the double-
1912 bracket operator: “if[[$foo=bar]]”
1913 time [-p] [pipeline]
1915 If a pipeline is given, the times used to execute the pipeline
1916 are reported. If no pipeline is given, then the user and system
1917 time used by the shell itself, and all the commands it has run
1918 since it was started, are reported. The times reported are the
1919 real time (elapsed time from start to finish), the user CPU time
1920 (time spent running in user mode), and the system CPU time (time
1921 spent running in kernel mode). Times are reported to standard
1922 error; the format of the output is:
1923 0m0.00s real 0m0.00s user 0m0.00s system
1925 If the -p option is given the output is slightly longer:
1927 real 0.00
1929 user 0.00
1930 sys 0.00
1931 It is an error to specify the -p option unless pipeline is a sim‐
1933 ple command.
1934 Simple redirections of standard error do not affect the output of
1936 the time command:
1937 $timesleep12>afile
1939 ${timesleep1;}2>afile
1940 Times for the first command do not go to “afile”, but those of
1942 the second command do.
1943 times Print the accumulated user and system times used both by the
1945 shell and by processes that the shell started which have exited.
1946 The format of the output is:
1947 0m0.00s 0m0.00s
1949 0m0.00s 0m0.00s
1950 trap[handlersignal...]
1952 Sets a trap handler that is to be executed when any of the speci‐
1953 fied signals are received. handler is either a NULL string,
1954 indicating the signals are to be ignored, a minus sign (‘-’),
1955 indicating that the default action is to be taken for the signals
1956 (see signal(3)), or a string containing shell commands to be
1957 evaluated and executed at the first opportunity (i.e. when the
1958 current command completes, or before printing the next PS1
1959 prompt) after receipt of one of the signals. signal is the name
1960 of a signal (e.g. PIPE or ALRM) or the number of the signal (see
1961 the kill-l command above).
1962 There are two special signals: EXIT (also known as 0) which is
1964 executed when the shell is about to exit, and ERR, which is exe‐
1965 cuted after an error occurs (an error is something that would
1966 cause the shell to exit if the -e or errexit option were set –
1967 see the set command above). EXIT handlers are executed in the
1968 environment of the last executed command. Note that for non-
1969 interactive shells, the trap handler cannot be changed for sig‐
1970 nals that were ignored when the shell started.
1971 With no arguments, trap lists, as a series of trap commands, the
1973 current state of the traps that have been set since the shell
1974 started. Note that the output of trap cannot be usefully piped
1975 to another process (an artifact of the fact that traps are
1976 cleared when subprocesses are created).
1977 The original Korn shell's DEBUG trap and the handling of ERR and
1979 EXIT traps in functions are not yet implemented.
1980 true A command that exits with a zero value.
1982 typeset [[+-lprtUux] [-L[n]] [-R[n]] [-Z[n]] [-i[n]] |-f[-tux]] [name
1984 [=value] ...]
1985 Display or set parameter attributes. With no name arguments,
1986 parameter attributes are displayed; if no options are used, the
1987 current attributes of all parameters are printed as typeset com‐
1988 mands; if an option is given (or ‘-’ with no option letter), all
1989 parameters and their values with the specified attributes are
1990 printed; if options are introduced with ‘+’, parameter values are
1991 not printed.
1992 If name arguments are given, the attributes of the named parame‐
1994 ters are set (-) or cleared (+). Values for parameters may
1995 optionally be specified. If typeset is used inside a function,
1996 any newly created parameters are local to the function.
1997 When -f is used, typeset operates on the attributes of functions.
1999 As with parameters, if no name arguments are given, functions are
2000 listed with their values (i.e. definitions) unless options are
2001 introduced with ‘+’, in which case only the function names are
2002 reported.
2003 -f Function mode. Display or set functions and their
2005 attributes, instead of parameters.
2006 -i[n] Integer attribute. n specifies the base to use when dis‐
2008 playing the integer (if not specified, the base given in
2009 the first assignment is used). Parameters with this
2010 attribute may be assigned values containing arithmetic
2011 expressions.
2012 -L[n] Left justify attribute. n specifies the field width. If
2014 n is not specified, the current width of a parameter (or
2015 the width of its first assigned value) is used. Leading
2016 whitespace (and zeros, if used with the -Z option) is
2017 stripped. If necessary, values are either truncated or
2018 space padded to fit the field width.
2019 -l Lower case attribute. All upper case characters in val‐
2021 ues are converted to lower case. (In the original Korn
2022 shell, this parameter meant “longinteger” when used with
2023 the -i option.)
2024 -p Print complete typeset commands that can be used to re-
2026 create the attributes and values of parameters.
2027 -R[n] Right justify attribute. n specifies the field width.
2029 If n is not specified, the current width of a parameter
2030 (or the width of its first assigned value) is used.
2031 Trailing whitespace is stripped. If necessary, values
2032 are either stripped of leading characters or space padded
2033 to make them fit the field width.
2034 -r Read-only attribute. Parameters with this attribute may
2036 not be assigned to or unset. Once this attribute is set,
2037 it cannot be turned off.
2038 -t Tag attribute. Has no meaning to the shell; provided for
2040 application use.
2041 For functions, -t is the trace attribute. When functions
2043 with the trace attribute are executed, the xtrace (-x)
2044 shell option is temporarily turned on.
2045 -U Unsigned integer attribute. Integers are printed as
2047 unsigned values (combine with the -i option). This
2048 option is not in the original Korn shell.
2049 -u Upper case attribute. All lower case characters in val‐
2051 ues are converted to upper case. (In the original Korn
2052 shell, this parameter meant “unsignedinteger” when used
2053 with the -i option which meant upper case letters would
2054 never be used for bases greater than 10. See the -U
2055 option.)
2056 For functions, -u is the undefined attribute. See
2058 Functions above for the implications of this.
2059 -x Export attribute. Parameters (or functions) are placed
2061 in the environment of any executed commands. Exported
2062 functions are not yet implemented.
2063 -Z[n] Zero fill attribute. If not combined with -L, this is
2065 the same as -R, except zero padding is used instead of
2066 space padding.
2067 If any of the -i, -L, -l, -R, -U, -u, or -Z options are changed,
2069 all others from this set are cleared, unless they are also given
2070 on the same command line.
2071 ulimit [-acdfHLlmnpSsTtvw] [value]
2073 Display or set process limits. If no options are used, the file
2074 size limit (-f) is assumed. value, if specified, may be either
2075 an arithmetic expression or the word “unlimited”. The limits
2076 affect the shell and any processes created by the shell after a
2077 limit is imposed. Note that some systems may not allow limits to
2078 be increased once they are set. Also note that the types of lim‐
2079 its available are system dependent – some systems have only the
2080 -f limit.
2081 -a Display all limits; unless -H is used, soft limits are
2083 displayed.
2084 -cn Impose a size limit of n blocks on the size of core dumps.
2086 -dn Impose a size limit of n kibibytes on the size of the data
2088 area.
2089 -fn Impose a size limit of n blocks on files written by the
2091 shell and its child processes (files of any size may be
2092 read).
2093 -H Set the hard limit only (the default is to set both hard
2095 and soft limits).
2096 -Ln Control flocks; documentation is missing.
2098 -ln Impose a limit of n kibibytes on the amount of locked
2100 (wired) physical memory.
2101 -mn Impose a limit of n kibibytes on the amount of physical
2103 memory used.
2104 -nn Impose a limit of n file descriptors that can be open at
2106 once.
2107 -pn Impose a limit of n processes that can be run by the user
2109 at any one time.
2110 -S Set the soft limit only (the default is to set both hard
2112 and soft limits).
2113 -sn Impose a size limit of n kibibytes on the size of the
2115 stack area.
2116 -Tn Impose a time limit of n real seconds to be used by each
2118 process.
2119 -tn Impose a time limit of n CPU seconds spent in user mode to
2121 be used by each process.
2122 -vn Impose a limit of n kibibytes on the amount of virtual
2124 memory (address space) used.
2125 -wn Impose a limit of n kibibytes on the amount of swap space
2127 used.
2128 As far as ulimit is concerned, a block is 512 bytes.
2130 umask [-S] [mask]
2132 Display or set the file permission creation mask, or umask (see
2133 umask(2)). If the -S option is used, the mask displayed or set
2134 is symbolic; otherwise, it is an octal number.
2135 Symbolic masks are like those used by chmod(1). When used, they
2137 describe what permissions may be made available (as opposed to
2138 octal masks in which a set bit means the corresponding bit is to
2139 be cleared). For example, “ug=rwx,o=” sets the mask so files
2140 will not be readable, writable, or executable by “others”, and is
2141 equivalent (on most systems) to the octal mask “007”.
2142 unalias [-adt] [name...]
2144 The aliases for the given names are removed. If the -a option is
2145 used, all aliases are removed. If the -t or -d options are used,
2146 the indicated operations are carried out on tracked or directory
2147 aliases, respectively.
2148 unset [-fv] parameter...
2150 Unset the named parameters (-v, the default) or functions (-f).
2151 wait[job...]
2153 Wait for the specified job(s) to finish. The exit status of wait
2154 is that of the last specified job; if the last job is killed by a
2155 signal, the exit status is 128 + the number of the signal (see
2156 kill-lexit-status above); if the last specified job can't be
2157 found (because it never existed, or had already finished), the
2158 exit status of wait is 127. See Jobcontrol below for the format
2159 of job. wait will return if a signal for which a trap has been
2160 set is received, or if a SIGHUP, SIGINT, or SIGQUIT signal is
2161 received.
2162 If no jobs are specified, wait waits for all currently running
2164 jobs (if any) to finish and exits with a zero status. If job
2165 monitoring is enabled, the completion status of jobs is printed
2166 (this is not the case when jobs are explicitly specified).
2167 whence [-pv] [name...]
2169 For each name, the type of command is listed (reserved word,
2170 built-in, alias, function, tracked alias, or executable). If the
2171 -p option is used, a path search is performed even if name is a
2172 reserved word, alias, etc. Without the -v option, whence is sim‐
2173 ilar to command-v except that whence will find reserved words and
2174 won't print aliases as alias commands. With the -v option,
2175 whence is the same as command-V. Note that for whence, the -p
2176 option does not affect the search path used, as it does for
2177 command. If the type of one or more of the names could not be
2178 determined, the exit status is non-zero.
2179 Jobcontrol
2181 Job control refers to the shell's ability to monitor and control jobs
2182 which are processes or groups of processes created for commands or pipe‐
2183 lines. At a minimum, the shell keeps track of the status of the back‐
2184 ground (i.e. asynchronous) jobs that currently exist; this information
2185 can be displayed using the jobs commands. If job control is fully
2186 enabled (using set-m or set-omonitor), as it is for interactive shells,
2187 the processes of a job are placed in their own process group. Foreground
2188 jobs can be stopped by typing the suspend character from the terminal
2189 (normally ^Z), jobs can be restarted in either the foreground or back‐
2190 ground using the fg and bg commands, and the state of the terminal is
2191 saved or restored when a foreground job is stopped or restarted, respec‐
2192 tively.
2193 Note that only commands that create processes (e.g. asynchronous com‐
2195 mands, subshell commands, and non-built-in, non-function commands) can be
2196 stopped; commands like read cannot be.
2197 When a job is created, it is assigned a job number. For interactive
2199 shells, this number is printed inside “[..]”, followed by the process IDs
2200 of the processes in the job when an asynchronous command is run. A job
2201 may be referred to in the bg, fg, jobs, kill, and wait commands either by
2202 the process ID of the last process in the command pipeline (as stored in
2203 the $! parameter) or by prefixing the job number with a percent sign
2204 (‘%’). Other percent sequences can also be used to refer to jobs:
2205 %+|%%|% The most recently stopped job, or, if there are no stopped
2207 jobs, the oldest running job.
2208 %- The job that would be the %+ job if the latter did not
2210 exist.
2211 %n The job with job number n.
2213 %?string The job with its command containing the string string (an
2215 error occurs if multiple jobs are matched).
2216 %string The job with its command starting with the string string
2218 (an error occurs if multiple jobs are matched).
2219 When a job changes state (e.g. a background job finishes or foreground
2221 job is stopped), the shell prints the following status information:
2222 [number]flagstatuscommand
2224 where...
2226 number is the job number of the job;
2228 flag is the ‘+’ or ‘-’ character if the job is the %+ or %- job,
2230 respectively, or space if it is neither;
2231 status indicates the current state of the job and can be:
2233 Done[number]
2235 The job exited. number is the exit status of the job
2236 which is omitted if the status is zero.
2237 Running The job has neither stopped nor exited (note that
2239 running does not necessarily mean consuming CPU time
2240 – the process could be blocked waiting for some
2241 event).
2242 Stopped[signal]
2244 The job was stopped by the indicated signal (if no
2245 signal is given, the job was stopped by SIGTSTP).
2246 signal-description[“coredumped”]
2248 The job was killed by a signal (e.g. memory fault,
2249 hangup); use kill-l for a list of signal descrip‐
2250 tions. The “coredumped” message indicates the
2251 process created a core file.
2252 command is the command that created the process. If there are multiple
2254 processes in the job, each process will have a line showing its
2255 command and possibly its status, if it is different from the
2256 status of the previous process.
2257 When an attempt is made to exit the shell while there are jobs in the
2259 stopped state, the shell warns the user that there are stopped jobs and
2260 does not exit. If another attempt is immediately made to exit the shell,
2261 the stopped jobs are sent a SIGHUP signal and the shell exits. Simi‐
2262 larly, if the nohup option is not set and there are running jobs when an
2263 attempt is made to exit a login shell, the shell warns the user and does
2264 not exit. If another attempt is immediately made to exit the shell, the
2265 running jobs are sent a SIGHUP signal and the shell exits.
2266 Interactiveinputlineediting
2268 The shell supports three modes of reading command lines from a tty(4) in
2269 an interactive session, controlled by the emacs, gmacs, and vi options
2270 (at most one of these can be set at once). The default is emacs. Edit‐
2271 ing modes can be set explicitly using the set built-in. If none of these
2272 options are enabled, the shell simply reads lines using the normal tty(4)
2273 driver. If the emacs or gmacs option is set, the shell allows emacs-like
2274 editing of the command; similarly, if the vi option is set, the shell
2275 allows vi-like editing of the command. These modes are described in
2276 detail in the following sections.
2277 In these editing modes, if a line is longer than the screen width (see
2279 the COLUMNS parameter), a ‘>’, ‘+’, or ‘<’ character is displayed in the
2280 last column indicating that there are more characters after, before and
2281 after, or before the current position, respectively. The line is
2282 scrolled horizontally as necessary.
2283 Emacseditingmode
2285 When the emacs option is set, interactive input line editing is enabled.
2286 Warning: This mode is slightly different from the emacs mode in the orig‐
2287 inal Korn shell. In this mode, various editing commands (typically bound
2288 to one or more control characters) cause immediate actions without wait‐
2289 ing for a newline. Several editing commands are bound to particular con‐
2290 trol characters when the shell is invoked; these bindings can be changed
2291 using the bind command.
2292 The following is a list of available editing commands. Each description
2294 starts with the name of the command, suffixed with a colon; an [n] (if
2295 the command can be prefixed with a count); and any keys the command is
2296 bound to by default, written using caret notation e.g. the ASCII ESC
2297 character is written as ^[. These control sequences are not case sensi‐
2298 tive. A count prefix for a command is entered using the sequence ^[n,
2299 where n is a sequence of 1 or more digits. Unless otherwise specified,
2300 if a count is omitted, it defaults to 1.
2301 Note that editing command names are used only with the bind command.
2303 Furthermore, many editing commands are useful only on terminals with a
2304 visible cursor. The default bindings were chosen to resemble correspond‐
2305 ing Emacs key bindings. The user's tty(4) characters (e.g. ERASE) are
2306 bound to reasonable substitutes and override the default bindings.
2307 abort:^C,^G
2309 Abort the current command, empty the line buffer and set the exit
2310 state to interrupted.
2311 auto-insert:[n]
2313 Simply causes the character to appear as literal input. Most
2314 ordinary characters are bound to this.
2315 backward-char: [n] ^B,^XD
2317 Moves the cursor backward n characters.
2318 backward-word: [n] ^[b
2320 Moves the cursor backward to the beginning of the word; words
2321 consist of alphanumerics, underscore (‘_’), and dollar sign (‘$’)
2322 characters.
2323 beginning-of-history:^[<
2325 Moves to the beginning of the history.
2326 beginning-of-line:^A
2328 Moves the cursor to the beginning of the edited input line.
2329 capitalise-word: [n] ^[C,^[c
2331 Uppercase the first character in the next n words, leaving the
2332 cursor past the end of the last word.
2333 clear-screen:^[^L
2335 Prints a compile-time configurable sequence to clear the screen
2336 and home the cursor, redraws the entire prompt and the currently
2337 edited input line. The default sequence works for almost all
2338 standard terminals.
2339 comment:^[#
2341 If the current line does not begin with a comment character, one
2342 is added at the beginning of the line and the line is entered (as
2343 if return had been pressed); otherwise, the existing comment
2344 characters are removed and the cursor is placed at the beginning
2345 of the line.
2346 complete:^[^[
2348 Automatically completes as much as is unique of the command name
2349 or the file name containing the cursor. If the entire remaining
2350 command or file name is unique, a space is printed after its com‐
2351 pletion, unless it is a directory name in which case ‘/’ is
2352 appended. If there is no command or file name with the current
2353 partial word as its prefix, a bell character is output (usually
2354 causing a beep to be sounded).
2355 complete-command:^X^[
2357 Automatically completes as much as is unique of the command name
2358 having the partial word up to the cursor as its prefix, as in the
2359 complete command above.
2360 complete-file:^[^X
2362 Automatically completes as much as is unique of the file name
2363 having the partial word up to the cursor as its prefix, as in the
2364 complete command described above.
2365 complete-list:^I,^[=
2367 Complete as much as is possible of the current word, and list the
2368 possible completions for it. If only one completion is possible,
2369 match as in the complete command above. Note that ^I is usually
2370 generated by the TAB (tabulator) key.
2371 delete-char-backward: [n] ERASE,^?,^H
2373 Deletes n characters before the cursor.
2374 delete-char-forward:[n]
2376 Deletes n characters after the cursor.
2377 delete-word-backward: [n] ERASE,^[^?,^[^H,^[h
2379 Deletes n words before the cursor.
2380 delete-word-forward: [n] ^[d
2382 Deletes characters after the cursor up to the end of n words.
2383 down-history: [n] ^N,^XB
2385 Scrolls the history buffer forward n lines (later). Each input
2386 line originally starts just after the last entry in the history
2387 buffer, so down-history is not useful until either search-history
2388 or up-history has been performed.
2389 downcase-word: [n] ^[L,^[l
2391 Lowercases the next n words.
2392 end-of-history:^[>
2394 Moves to the end of the history.
2395 end-of-line:^E
2397 Moves the cursor to the end of the input line.
2398 eot:^_ Acts as an end-of-file; this is useful because edit-mode input
2400 disables normal terminal input canonicalization.
2401 eot-or-delete: [n] ^D
2403 Acts as eot if alone on a line; otherwise acts as
2404 delete-char-forward.
2405 error:(notbound)
2407 Error (ring the bell).
2408 exchange-point-and-mark:^X^X
2410 Places the cursor where the mark is and sets the mark to where
2411 the cursor was.
2412 expand-file:^[*
2414 Appends a ‘*’ to the current word and replaces the word with the
2415 result of performing file globbing on the word. If no files
2416 match the pattern, the bell is rung.
2417 forward-char: [n] ^F,^XC
2419 Moves the cursor forward n characters.
2420 forward-word: [n] ^[f
2422 Moves the cursor forward to the end of the nth word.
2423 goto-history: [n] ^[g
2425 Goes to history number n.
2426 kill-line:KILL
2428 Deletes the entire input line.
2429 kill-region:^W
2431 Deletes the input between the cursor and the mark.
2432 kill-to-eol: [n] ^K
2434 Deletes the input from the cursor to the end of the line if n is
2435 not specified; otherwise deletes characters between the cursor
2436 and column n.
2437 list:^[?
2439 Prints a sorted, columnated list of command names or file names
2440 (if any) that can complete the partial word containing the cur‐
2441 sor. Directory names have ‘/’ appended to them.
2442 list-command:^X?
2444 Prints a sorted, columnated list of command names (if any) that
2445 can complete the partial word containing the cursor.
2446 list-file:^X^Y
2448 Prints a sorted, columnated list of file names (if any) that can
2449 complete the partial word containing the cursor. File type indi‐
2450 cators are appended as described under list above.
2451 newline:^J,^M
2453 Causes the current input line to be processed by the shell. The
2454 current cursor position may be anywhere on the line.
2455 newline-and-next:^O
2457 Causes the current input line to be processed by the shell, and
2458 the next line from history becomes the current line. This is
2459 only useful after an up-history or search-history.
2460 no-op:QUIT
2462 This does nothing.
2463 prefix-1:^[
2465 Introduces a 2-character command sequence.
2466 prefix-2:^X,^[[,^[O
2468 Introduces a 2-character command sequence.
2469 prev-hist-word: [n] ^[.,^[_
2471 The last (nth) word of the previous command is inserted at the
2472 cursor.
2473 quote:^^,^V
2475 The following character is taken literally rather than as an
2476 editing command.
2477 redraw:^L
2479 Reprints the last line of the prompt string and the current input
2480 line on a new line.
2481 search-character-backward: [n] ^[^]
2483 Search backward in the current line for the nth occurrence of the
2484 next character typed.
2485 search-character-forward: [n] ^]
2487 Search forward in the current line for the nth occurrence of the
2488 next character typed.
2489 search-history:^R
2491 Enter incremental search mode. The internal history list is
2492 searched backwards for commands matching the input. An initial
2493 ‘^’ in the search string anchors the search. The escape key will
2494 leave search mode. Other commands will be executed after leaving
2495 search mode. Successive search-history commands continue search‐
2496 ing backward to the next previous occurrence of the pattern. The
2497 history buffer retains only a finite number of lines; the oldest
2498 are discarded as necessary.
2499 set-mark-command:^[⟨space⟩
2501 Set the mark at the cursor position.
2502 transpose-chars:^T
2504 If at the end of line, or if the gmacs option is set, this
2505 exchanges the two previous characters; otherwise, it exchanges
2506 the previous and current characters and moves the cursor one
2507 character to the right.
2508 up-history: [n] ^P,^XA
2510 Scrolls the history buffer backward n lines (earlier).
2511 upcase-word: [n] ^[U,^[u
2513 Uppercase the next n words.
2514 version:^[^V
2516 Display the version of mksh. The current edit buffer is restored
2517 as soon as a key is pressed. The restoring keypress is pro‐
2518 cessed, unless it is a space.
2519 yank:^Y
2521 Inserts the most recently killed text string at the current cur‐
2522 sor position.
2523 yank-pop:^[y
2525 Immediately after a yank, replaces the inserted text string with
2526 the next previously killed text string.
2527 Vieditingmode
2529 The vi command-line editor in mksh has basically the same commands as the
2530 vi(1) editor with the following exceptions:
2531 · You start out in insert mode.
2533 · There are file name and command completion commands: =, \, *, ^X, ^E,
2535 ^F, and, optionally, ⟨tab⟩ and ⟨esc⟩.
2536 · The _ command is different (in mksh, it is the last argument command;
2538 in vi(1) it goes to the start of the current line).
2539 · The / and G commands move in the opposite direction to the j command.
2541 · Commands which don't make sense in a single line editor are not
2543 available (e.g. screen movement commands and ex(1)-style colon (:)
2544 commands).
2545 Like vi(1), there are two modes: “insert” mode and “command” mode. In
2547 insert mode, most characters are simply put in the buffer at the current
2548 cursor position as they are typed; however, some characters are treated
2549 specially. In particular, the following characters are taken from cur‐
2550 rent tty(4) settings (see stty(1)) and have their usual meaning (normal
2551 values are in parentheses): kill (^U), erase (^?), werase (^W), eof (^D),
2552 intr (^C), and quit (^\). In addition to the above, the following char‐
2553 acters are also treated specially in insert mode:
2554 ^E Command and file name enumeration (see below).
2556 ^F Command and file name completion (see below). If used twice
2558 in a row, the list of possible completions is displayed; if
2559 used a third time, the completion is undone.
2560 ^H Erases previous character.
2562 ^J|^M End of line. The current line is read, parsed, and executed
2564 by the shell.
2565 ^V Literal next. The next character typed is not treated spe‐
2567 cially (can be used to insert the characters being described
2568 here).
2569 ^X Command and file name expansion (see below).
2571 ⟨esc⟩ Puts the editor in command mode (see below).
2573 ⟨tab⟩ Optional file name and command completion (see ^F above),
2575 enabled with set-ovi-tabcomplete.
2576 In command mode, each character is interpreted as a command. Characters
2578 that don't correspond to commands, are illegal combinations of commands,
2579 or are commands that can't be carried out, all cause beeps. In the fol‐
2580 lowing command descriptions, an [n] indicates the command may be prefixed
2581 by a number (e.g. 10l moves right 10 characters); if no number prefix is
2582 used, n is assumed to be 1 unless otherwise specified. The term
2583 “currentposition” refers to the position between the cursor and the char‐
2584 acter preceding the cursor. A “word” is a sequence of letters, digits,
2585 and underscore characters or a sequence of non-letter, non-digit, non-
2586 underscore, and non-whitespace characters (e.g. “ab2*&^” contains two
2587 words) and a “big-word” is a sequence of non-whitespace characters.
2588 Special mksh vi commands:
2590 The following commands are not in, or are different from, the normal vi
2592 file editor:
2593 [n]_ Insert a space followed by the nth big-word from the last
2595 command in the history at the current position and enter
2596 insert mode; if n is not specified, the last word is
2597 inserted.
2598 # Insert the comment character (‘#’) at the start of the cur‐
2600 rent line and return the line to the shell (equivalent to
2601 I#^J).
2602 [n]g Like G, except if n is not specified, it goes to the most
2604 recent remembered line.
2605 [n]v Edit line n using the vi(1) editor; if n is not specified,
2607 the current line is edited. The actual command executed is
2608 fc-e${VISUAL:-${EDITOR:-vi}}n.
2609 *and^X Command or file name expansion is applied to the current big-
2611 word (with an appended ‘*’ if the word contains no file glob‐
2612 bing characters) – the big-word is replaced with the result‐
2613 ing words. If the current big-word is the first on the line
2614 (or follows one of the following characters: ‘;’, ‘|’, ‘&’,
2615 ‘(’, or ‘)’ and does not contain a slash (‘/’) then command
2616 expansion is done; otherwise file name expansion is done.
2617 Command expansion will match the big-word against all
2618 aliases, functions, and built-in commands as well as any exe‐
2619 cutable files found by searching the directories in the PATH
2620 parameter. File name expansion matches the big-word against
2621 the files in the current directory. After expansion, the
2622 cursor is placed just past the last word and the editor is in
2623 insert mode.
2624 [n]\, [n]^F, [n]⟨tab⟩, and [n]⟨esc⟩
2626 Command/file name completion. Replace the current big-word
2627 with the longest unique match obtained after performing com‐
2628 mand and file name expansion. ⟨tab⟩ is only recognised if
2629 the vi-tabcomplete option is set, while ⟨esc⟩ is only recog‐
2630 nised if the vi-esccomplete option is set (see set-o). If n
2631 is specified, the nth possible completion is selected (as
2632 reported by the command/file name enumeration command).
2633 =and^E Command/file name enumeration. List all the commands or
2635 files that match the current big-word.
2636 ^V Display the version of mksh. The current edit buffer is
2638 restored as soon as a key is pressed. The restoring keypress
2639 is ignored.
2640 @c Macro expansion. Execute the commands found in the alias c.
2642 Intra-line movement commands:
2644 [n]hand [n]^H
2646 Move left n characters.
2647 [n]land [n]⟨space⟩
2649 Move right n characters.
2650 0 Move to column 0.
2652 ^ Move to the first non-whitespace character.
2654 [n]| Move to column n.
2656 $ Move to the last character.
2658 [n]b Move back n words.
2660 [n]B Move back n big-words.
2662 [n]e Move forward to the end of the word, n times.
2664 [n]E Move forward to the end of the big-word, n times.
2666 [n]w Move forward n words.
2668 [n]W Move forward n big-words.
2670 % Find match. The editor looks forward for the nearest parenthe‐
2672 sis, bracket, or brace and then moves the cursor to the matching
2673 parenthesis, bracket, or brace.
2674 [n]fc Move forward to the nth occurrence of the character c.
2676 [n]Fc Move backward to the nth occurrence of the character c.
2678 [n]tc Move forward to just before the nth occurrence of the character
2680 c.
2681 [n]Tc Move backward to just before the nth occurrence of the character
2683 c.
2684 [n]; Repeats the last f,F,t, or T command.
2686 [n], Repeats the last f,F,t, or T command, but moves in the opposite
2688 direction.
2689 Inter-line movement commands:
2691 [n]j, [n]+, and [n]^N
2693 Move to the nth next line in the history.
2694 [n]k, [n]-, and [n]^P
2696 Move to the nth previous line in the history.
2697 [n]G Move to line n in the history; if n is not specified, the number
2699 of the first remembered line is used.
2700 [n]g Like G, except if n is not specified, it goes to the most recent
2702 remembered line.
2703 [n]/string
2705 Search backward through the history for the nth line containing
2706 string; if string starts with ‘^’, the remainder of the string
2707 must appear at the start of the history line for it to match.
2708 [n]?string
2710 Same as /, except it searches forward through the history.
2711 [n]n Search for the nth occurrence of the last search string; the
2713 direction of the search is the same as the last search.
2714 [n]N Search for the nth occurrence of the last search string; the
2716 direction of the search is the opposite of the last search.
2717 Edit commands
2719 [n]a Append text n times; goes into insert mode just after the current
2721 position. The append is only replicated if command mode is re-
2722 entered i.e. ⟨esc⟩ is used.
2723 [n]A Same as a, except it appends at the end of the line.
2725 [n]i Insert text n times; goes into insert mode at the current posi‐
2727 tion. The insertion is only replicated if command mode is re-
2728 entered i.e. ⟨esc⟩ is used.
2729 [n]I Same as i, except the insertion is done just before the first
2731 non-blank character.
2732 [n]s Substitute the next n characters (i.e. delete the characters and
2734 go into insert mode).
2735 S Substitute whole line. All characters from the first non-blank
2737 character to the end of the line are deleted and insert mode is
2738 entered.
2739 [n]cmove-cmd
2741 Change from the current position to the position resulting from
2742 nmove-cmds (i.e. delete the indicated region and go into insert
2743 mode); if move-cmd is c, the line starting from the first non-
2744 blank character is changed.
2745 C Change from the current position to the end of the line (i.e.
2747 delete to the end of the line and go into insert mode).
2748 [n]x Delete the next n characters.
2750 [n]X Delete the previous n characters.
2752 D Delete to the end of the line.
2754 [n]dmove-cmd
2756 Delete from the current position to the position resulting from
2757 nmove-cmds; move-cmd is a movement command (see above) or d, in
2758 which case the current line is deleted.
2759 [n]rc Replace the next n characters with the character c.
2761 [n]R Replace. Enter insert mode but overwrite existing characters
2763 instead of inserting before existing characters. The replacement
2764 is repeated n times.
2765 [n]~ Change the case of the next n characters.
2767 [n]ymove-cmd
2769 Yank from the current position to the position resulting from
2770 nmove-cmds into the yank buffer; if move-cmd is y, the whole line
2771 is yanked.
2772 Y Yank from the current position to the end of the line.
2774 [n]p Paste the contents of the yank buffer just after the current
2776 position, n times.
2777 [n]P Same as p, except the buffer is pasted at the current position.
2779 Miscellaneous vi commands
2781 ^Jand^M
2783 The current line is read, parsed, and executed by the shell.
2784 ^Land^R
2786 Redraw the current line.
2787 [n]. Redo the last edit command n times.
2789 u Undo the last edit command.
2791 U Undo all changes that have been made to the current line.
2793 intrandquit
2795 The interrupt and quit terminal characters cause the current line
2796 to be deleted and a new prompt to be printed.
2797
2799 ~/.mkshrc User's startup script (interactive shells). Used
2800 only if ENV is unset or empty.
2801 ~/.profile User's login profile.
2802 /etc/profile System login profile.
2803 /etc/shells Shell database.
2804 /etc/suid_profile Privileged shell profile.
2805
2807 awk(1), ed(1), getopt(1), sed(1), sh(1), stty(1), dup(2), execve(2),
2808 getgid(2), getuid(2), mknod(2), mkfifo(2), open(2), pipe(2), rename(2),
2809 wait(2), arc4random(3), getopt(3), nl_langinfo(3), rand(3), setlocale(3),
2810 signal(3), srand(3), system(3), tty(4), shells(5), environ(7), script(7),
2811 utf-8(7), mknod(8)
2812 http://docsrv.sco.com:507/en/man/html.C/sh.C.html
2814 MorrisBolsky, The KornShell Command and Programming Language, Prentice
2816 Hall PTR, xvi + 356 pages, 1989, ISBN 978-0-13-516972-8 (0-13-516972-0).
2817 MorrisI.Bolsky and DavidG.Korn, The New KornShell Command and Programming
2819 Language (2nd Edition), Prentice Hall PTR, xvi + 400 pages, 1995, ISBN
2820 978-0-13-182700-4 (0-13-182700-6).
2821 StephenG.Kochan and PatrickH.Wood, UNIX Shell Programming, Hayden,
2823 Revised Edition, xi + 490 pages, 1990, ISBN 978-0-672-48448-3
2824 (0-672-48448-X).
2825 IEEE Inc., IEEE Standard for Information Technology – Portable Operating
2827 System Interface (POSIX), IEEE Press, Part 2: Shell and Utilities,
2828 xvii + 1195 pages, 1993, ISBN 978-1-55937-255-8 (1-55937-255-9).
2829 BillRosenblatt, Learning the Korn Shell, O'Reilly, 360 pages, 1993, ISBN
2831 978-1-56592-054-5 (1-56592-054-6).
2832 BillRosenblatt and ArnoldRobbins, Learning the Korn Shell, Second
2834 Edition, O'Reilly, 432 pages, 2002, ISBN 978-0-596-00195-7
2835 (0-596-00195-9).
2836 BarryRosenberg, KornShell Programming Tutorial, Addison-Wesley
2838 Professional, xxi + 324 pages, 1991, ISBN 978-0-201-56324-5
2839 (0-201-56324-X).
2840
2842 This shell is based upon the Public Domain Korn SHell. It has been
2843 developed further by the MirOS project incorporating changes from the
2844 Debian and OpenBSD projects and patches and suggestions from users and
2845 many other persons, and is currently maintained by
2846 ThorstenGlaser<tg@mirbsd.de>.
2847
2849 This document attempts to describe mksh R33c and up, compiled without any
2850 options impacting functionality, such as MKSH_SMALL, for an operating
2851 environment supporting all of its advanced needs. Please report bugs in
2852 mksh to the ⟨miros-discuss@mirbsd.org⟩ mailing list or in the #!/bin/mksh
2853 (or#ksh) IRC channel at irc.freenode.net:6667.
2854MirBSD April 1, 2008 MirBSD