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 builtin-name [argument ...]
10
12 mksh is a command interpreter intended for both interactive and shell
13 script use. Its command language is a superset of the sh(C) shell lan‐
14 guage and largely compatible to the original Korn shell.
15 Most builtins can be called directly, for example if a link points from
17 its name to the shell; not all make sense, have been tested or work at
18 all though.
19 The options are as follows:
21 -c string mksh will execute the command(s) contained in string.
23 -i Interactive shell. A shell is “interactive” if this option is
25 used or if both standard input and standard error are attached
26 to a tty(4). An interactive shell has job control enabled,
27 ignores the SIGINT, SIGQUIT, and SIGTERM signals, and prints
28 prompts before reading input (see the PS1 and PS2 parameters).
29 It also processes the ENV parameter or the mkshrc file (see
30 below). For non-interactive shells, the trackall option is on
31 by default (see the set command below).
32 -l Login shell. If the basename the shell is called with (i.e.
34 argv[0]) starts with ‘-’ or if this option is used, the shell
35 is assumed to be a login shell; see Startup files below.
36 -p Privileged shell. A shell is “privileged” if this option is
38 used or if the real user ID or group ID does not match the
39 effective user ID or group ID (see getuid(2) and getgid(2)).
40 Clearing the privileged option causes the shell to set its
41 effective user ID (group ID) to its real user ID (group ID).
42 For further implications, see Startup files.
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 (and chdir) 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
53 used.
54 · Redirections that create files can't be used (i.e. ‘>’,
55 ‘>|’, ‘>>’, ‘<>’).
56 -s The shell reads commands from standard input; all non-option
58 arguments are positional parameters.
59 -T tty Spawn mksh on the tty(4) device given. Superuser only. If
61 tty is a dash, detach from controlling terminal (daemonise)
62 instead.
63 In addition to the above, the options described in the set built-in com‐
65 mand can also be used on the command line: both [-+abCefhkmnuvXx] and
66 [-+o option] can be used for single letter or long options, respectively.
67 If neither the -c nor the -s option is specified, the first non-option
69 argument specifies the name of a file the shell reads commands from. If
70 there are no non-option arguments, the shell reads commands from the
71 standard input. The name of the shell (i.e. the contents of $0) is
72 determined as follows: if the -c option is used and there is a non-option
73 argument, it is used as the name; if commands are being read from a file,
74 the file is used as the name; otherwise, the basename the shell was
75 called with (i.e. argv[0]) is used.
76 The exit status of the shell is 127 if the command file specified on the
78 command line could not be opened, or non-zero if a fatal syntax error
79 occurred during the execution of a script. In the absence of fatal
80 errors, the exit status is that of the last command executed, or zero, if
81 no command is executed.
82 Startup files
84 For the actual location of these files, see FILES. A login shell pro‐
85 cesses the system profile first. A privileged shell then processes the
86 suid profile. A non-privileged login shell processes the user profile
87 next. A non-privileged interactive shell checks the value of the ENV
88 parameter after subjecting it to parameter, command, arithmetic and tilde
89 (‘~’) substitution; if unset or empty, the user mkshrc profile is pro‐
90 cessed; otherwise, if a file whose name is the substitution result
91 exists, it is processed; non-existence is silently ignored.
92 Command syntax
94 The shell begins parsing its input by removing any backslash-newline com‐
95 binations, then breaking it into words. Words (which are sequences of
96 characters) are delimited by unquoted whitespace characters (space, tab,
97 and newline) or meta-characters (‘<’, ‘>’, ‘|’, ‘;’, ‘(’, ‘)’, and ‘&’).
98 Aside from delimiting words, spaces and tabs are ignored, while newlines
99 usually delimit commands. The meta-characters are used in building the
100 following tokens: ‘<’, ‘<&’, ‘<<’, ‘<<<’, ‘>’, ‘>&’, ‘>>’, ‘&>’, etc. are
101 used to specify redirections (see Input/output redirection below); ‘|’ is
102 used to create pipelines; ‘|&’ is used to create co-processes (see
103 Co-processes below); ‘;’ is used to separate commands; ‘&’ is used to
104 create asynchronous pipelines; ‘&&’ and ‘||’ are used to specify condi‐
105 tional execution; ‘;;’, ‘;&’ and ‘;|’ are used in case statements; ‘(( ..
106 ))’ is used in arithmetic expressions; and lastly, ‘( .. )’ is used to
107 create subshells.
108 Whitespace and meta-characters can be quoted individually using a back‐
110 slash (‘\’), or in groups using double (‘"’) or single (‘'’) quotes.
111 Note that the following characters are also treated specially by the
112 shell and must be quoted if they are to represent themselves: ‘\’, ‘"’,
113 ‘'’, ‘#’, ‘$’, ‘`’, ‘~’, ‘{’, ‘}’, ‘*’, ‘?’, and ‘[’. The first three of
114 these are the above mentioned quoting characters (see Quoting below);
115 ‘#’, if used at the beginning of a word, introduces a comment – every‐
116 thing after the ‘#’ up to the nearest newline is ignored; ‘$’ is used to
117 introduce parameter, command, and arithmetic substitutions (see
118 Substitution below); ‘`’ introduces an old-style command substitution
119 (see Substitution below); ‘~’ begins a directory expansion (see Tilde
120 expansion below); ‘{’ and ‘}’ delimit csh(1)-style alterations (see Brace
121 expansion below); and finally, ‘*’, ‘?’, and ‘[’ are used in file name
122 generation (see File name patterns below).
123 As words and tokens are parsed, the shell builds commands, of which there
125 are two basic types: simple-commands, typically programmes that are exe‐
126 cuted, and compound-commands, such as for and if statements, grouping
127 constructs, and function definitions.
128 A simple-command consists of some combination of parameter assignments
130 (see Parameters below), input/output redirections (see Input/output
131 redirections below), and command words; the only restriction is that
132 parameter assignments come before any command words. The command words,
133 if any, define the command that is to be executed and its arguments. The
134 command may be a shell built-in command, a function, or an external com‐
135 mand (i.e. a separate executable file that is located using the PATH
136 parameter; see Command execution below). Note that all command con‐
137 structs have an exit status: for external commands, this is related to
138 the status returned by wait(2) (if the command could not be found, the
139 exit status is 127; if it could not be executed, the exit status is 126);
140 the exit status of other command constructs (built-in commands, func‐
141 tions, compound-commands, pipelines, lists, etc.) are all well-defined
142 and are described where the construct is described. The exit status of a
143 command consisting only of parameter assignments is that of the last com‐
144 mand substitution performed during the parameter assignment or 0 if there
145 were no command substitutions.
146 Commands can be chained together using the ‘|’ token to form pipelines,
148 in which the standard output of each command but the last is piped (see
149 pipe(2)) to the standard input of the following command. The exit status
150 of a pipeline is that of its last command. All commands of a pipeline
151 are executed in separate subshells; this is allowed by POSIX but differs
152 from both variants of AT&T UNIX ksh, where all but the last command were
153 executed in subshells; see the read builtin's description for implica‐
154 tions and workarounds. A pipeline may be prefixed by the ‘!’ reserved
155 word which causes the exit status of the pipeline to be logically comple‐
156 mented: if the original status was 0, the complemented status will be 1;
157 if the original status was not 0, the complemented status will be 0.
158 Lists of commands can be created by separating pipelines by any of the
160 following tokens: ‘&&’, ‘||’, ‘&’, ‘|&’, and ‘;’. The first two are for
161 conditional execution: “cmd1 && cmd2” executes cmd2 only if the exit sta‐
162 tus of cmd1 is zero; ‘||’ is the opposite – cmd2 is executed only if the
163 exit status of cmd1 is non-zero. ‘&&’ and ‘||’ have equal precedence
164 which is higher than that of ‘&’, ‘|&’, and ‘;’, which also have equal
165 precedence. Note that the ‘&&’ and ‘||’ operators are
166 "left-associative". For example, both of these commands will print only
167 "bar":
168 $ false && echo foo || echo bar
170 $ true || echo foo && echo bar
171 The ‘&’ token causes the preceding command to be executed asynchronously;
173 that is, the shell starts the command but does not wait for it to com‐
174 plete (the shell does keep track of the status of asynchronous commands;
175 see Job control below). When an asynchronous command is started when job
176 control is disabled (i.e. in most scripts), the command is started with
177 signals SIGINT and SIGQUIT ignored and with input redirected from
178 /dev/null (however, redirections specified in the asynchronous command
179 have precedence). The ‘|&’ operator starts a co-process which is a spe‐
180 cial kind of asynchronous process (see Co-processes below). Note that a
181 command must follow the ‘&&’ and ‘||’ operators, while it need not follow
182 ‘&’, ‘|&’, or ‘;’. The exit status of a list is that of the last command
183 executed, with the exception of asynchronous lists, for which the exit
184 status is 0.
185 Compound commands are created using the following reserved words. These
187 words are only recognised if they are unquoted and if they are used as
188 the first word of a command (i.e. they can't be preceded by parameter
189 assignments or redirections):
190 case else function then ! (
192 do esac if time [[ ((
193 done fi in until {
194 elif for select while }
195 In the following compound command descriptions, command lists (denoted as
197 list) that are followed by reserved words must end with a semicolon, a
198 newline, or a (syntactically correct) reserved word. For example, the
199 following are all valid:
200 $ { echo foo; echo bar; }
202 $ { echo foo; echo bar<newline>}
203 $ { { echo foo; echo bar; } }
204 This is not valid:
206 $ { echo foo; echo bar }
208 (list)
210 Execute list in a subshell. There is no implicit way to pass envi‐
211 ronment changes from a subshell back to its parent.
212 { list; }
214 Compound construct; list is executed, but not in a subshell. Note
215 that ‘{’ and ‘}’ are reserved words, not meta-characters.
216 case word in [[(] pattern [| pat] ...) list [;; | ;& | ;| ]] ... esac
218 The case statement attempts to match word against a specified
219 pattern; the list associated with the first successfully matched
220 pattern is executed. Patterns used in case statements are the same
221 as those used for file name patterns except that the restrictions
222 regarding ‘.’ and ‘/’ are dropped. Note that any unquoted space
223 before and after a pattern is stripped; any space within a pattern
224 must be quoted. Both the word and the patterns are subject to
225 parameter, command, and arithmetic substitution, as well as tilde
226 substitution.
227 For historical reasons, open and close braces may be used instead
229 of in and esac e.g. case $foo { *) echo bar;; }.
230 The list terminators are:
232 ‘;;’ Terminate after the list.
234 ‘;&’ Fall through into the next list.
236 ‘;|’ Evaluate the remaining pattern-list tuples.
238 The exit status of a case statement is that of the executed list;
240 if no list is executed, the exit status is zero.
241 for name [in word ...]; do list; done
243 For each word in the specified word list, the parameter name is set
244 to the word and list is executed. If in is not used to specify a
245 word list, the positional parameters ($1, $2, etc.) are used
246 instead. For historical reasons, open and close braces may be used
247 instead of do and done e.g. for i; { echo $i; }. The exit status
248 of a for statement is the last exit status of list; if list is
249 never executed, the exit status is zero.
250 if list; then list; [elif list; then list;] ... [else list;] fi
252 If the exit status of the first list is zero, the second list is
253 executed; otherwise, the list following the elif, if any, is exe‐
254 cuted with similar consequences. If all the lists following the if
255 and elifs fail (i.e. exit with non-zero status), the list following
256 the else is executed. The exit status of an if statement is that
257 of non-conditional list that is executed; if no non-conditional
258 list is executed, the exit status is zero.
259 select name [in word ...]; do list; done
261 The select statement provides an automatic method of presenting the
262 user with a menu and selecting from it. An enumerated list of the
263 specified word(s) is printed on standard error, followed by a
264 prompt (PS3: normally ‘#? ’). A number corresponding to one of the
265 enumerated words is then read from standard input, name is set to
266 the selected word (or unset if the selection is not valid), REPLY
267 is set to what was read (leading/trailing space is stripped), and
268 list is executed. If a blank line (i.e. zero or more IFS octets)
269 is entered, the menu is reprinted without executing list.
270 When list completes, the enumerated list is printed if REPLY is
272 NULL, the prompt is printed, and so on. This process continues
273 until an end-of-file is read, an interrupt is received, or a break
274 statement is executed inside the loop. If “in word ...” is omit‐
275 ted, the positional parameters are used (i.e. $1, $2, etc.). For
276 historical reasons, open and close braces may be used instead of do
277 and done e.g. select i; { echo $i; }. The exit status of a select
278 statement is zero if a break statement is used to exit the loop,
279 non-zero otherwise.
280 until list; do list; done
282 This works like while, except that the body is executed only while
283 the exit status of the first list is non-zero.
284 while list; do list; done
286 A while is a pre-checked loop. Its body is executed as often as
287 the exit status of the first list is zero. The exit status of a
288 while statement is the last exit status of the list in the body of
289 the loop; if the body is not executed, the exit status is zero.
290 function name { list; }
292 Defines the function name (see Functions below). Note that redi‐
293 rections specified after a function definition are performed when‐
294 ever the function is executed, not when the function definition is
295 executed.
296 name() command
298 Mostly the same as function (see Functions below). Whitespace
299 (space or tab) after name will be ignored most of the time.
300 function name() { list; }
302 The same as name() (bashism). The function keyword is ignored.
303 time [-p] [pipeline]
305 The Command execution section describes the time reserved word.
306 (( expression ))
308 The arithmetic expression expression is evaluated; equivalent to
309 “let expression” (see Arithmetic expressions and the let command,
310 below).
311 [[ expression ]]
313 Similar to the test and [ ... ] commands (described later), with
314 the following exceptions:
315 · Field splitting and file name generation are not performed on
317 arguments.
318 · The -a (AND) and -o (OR) operators are replaced with ‘&&’ and
320 ‘||’, respectively.
321 · Operators (e.g. ‘-f’, ‘=’, ‘!’) must be unquoted.
323 · Parameter, command, and arithmetic substitutions are performed
325 as expressions are evaluated and lazy expression evaluation is
326 used for the ‘&&’ and ‘||’ operators. This means that in the
327 following statement, $(<foo) is evaluated if and only if the
328 file foo exists and is readable:
329 $ [[ -r foo && $(<foo) = b*r ]]
331 · The second operand of the ‘!=’ and ‘=’ expressions are patterns
333 (e.g. the comparison [[ foobar = f*r ]] succeeds). This even
334 works indirectly:
335 $ bar=foobar; baz='f*r'
337 $ [[ $bar = $baz ]]; echo $?
338 $ [[ $bar = "$baz" ]]; echo $?
339 Perhaps surprisingly, the first comparison succeeds, whereas
341 the second doesn't.
342 Quoting
344 Quoting is used to prevent the shell from treating characters or words
345 specially. There are three methods of quoting. First, ‘\’ quotes the
346 following character, unless it is at the end of a line, in which case
347 both the ‘\’ and the newline are stripped. Second, a single quote (‘'’)
348 quotes everything up to the next single quote (this may span lines).
349 Third, a double quote (‘"’) quotes all characters, except ‘$’, ‘`’ and
350 ‘\’, up to the next unquoted double quote. ‘$’ and ‘`’ inside double
351 quotes have their usual meaning (i.e. parameter, command, or arithmetic
352 substitution) except no field splitting is carried out on the results of
353 double-quoted substitutions. If a ‘\’ inside a double-quoted string is
354 followed by ‘\’, ‘$’, ‘`’, or ‘"’, it is replaced by the second charac‐
355 ter; if it is followed by a newline, both the ‘\’ and the newline are
356 stripped; otherwise, both the ‘\’ and the character following are
357 unchanged.
358 If a single-quoted string is preceded by an unquoted ‘$’, C style back‐
360 slash expansion (see below) is applied (even single quote characters
361 inside can be escaped and do not terminate the string then); the expanded
362 result is treated as any other single-quoted string. If a double-quoted
363 string is preceded by an unquoted ‘$’, the latter is ignored.
364 Backslash expansion
366 In places where backslashes are expanded, certain C and AT&T UNIX ksh or
367 GNU bash style escapes are translated. These include ‘\a’, ‘\b’, ‘\f’,
368 ‘\n’, ‘\r’, ‘\t’, ‘\U########’, ‘\u####’, and ‘\v’. For ‘\U########’ and
369 ‘\u####’, “#” means a hexadecimal digit, of thich there may be none up to
370 four or eight; these escapes translate a Unicode codepoint to UTF-8.
371 Furthermore, ‘\E’ and ‘\e’ expand to the escape character.
372 In the print builtin mode, ‘\"’, ‘\'’, and ‘\?’ are explicitly excluded;
374 octal sequences must have the none up to three octal digits “#” prefixed
375 with the digit zero (‘\0###’); hexadecimal sequences ‘\x##’ are limited
376 to none up to two hexadecimal digits “#”; both octal and hexadecimal
377 sequences convert to raw octets; ‘\#’, where # is none of the above,
378 translates to \# (backslashes are retained).
379 Backslash expansion in the C style mode slightly differs: octal sequences
381 ‘\###’ must have no digit zero prefixing the one up to three octal digits
382 “#” and yield raw octets; hexadecimal sequences ‘\x#*’ greedily eat up as
383 many hexadecimal digits “#” as they can and terminate with the first non-
384 hexadecimal digit; these translate a Unicode codepoint to UTF-8. The
385 sequence ‘\c#’, where “#” is any octet, translates to Ctrl-# (which basi‐
386 cally means, ‘\c?’ becomes DEL, everything else is bitwise ANDed with
387 0x1F). Finally, ‘\#’, where # is none of the above, translates to # (has
388 the backslash trimmed), even if it is a newline.
389 Aliases
391 There are two types of aliases: normal command aliases and tracked
392 aliases. Command aliases are normally used as a short hand for a long or
393 often used command. The shell expands command aliases (i.e. substitutes
394 the alias name for its value) when it reads the first word of a command.
395 An expanded alias is re-processed to check for more aliases. If a com‐
396 mand alias ends in a space or tab, the following word is also checked for
397 alias expansion. The alias expansion process stops when a word that is
398 not an alias is found, when a quoted word is found, or when an alias word
399 that is currently being expanded is found.
400 The following command aliases are defined automatically by the shell:
402 autoload='typeset -fu'
404 functions='typeset -f'
405 hash='alias -t'
406 history='fc -l'
407 integer='typeset -i'
408 local='typeset'
409 login='exec login'
410 nameref='typeset -n'
411 nohup='nohup '
412 r='fc -e -'
413 stop='kill -STOP'
414 suspend='kill -STOP $$'
415 type='whence -v'
416 Tracked aliases allow the shell to remember where it found a particular
418 command. The first time the shell does a path search for a command that
419 is marked as a tracked alias, it saves the full path of the command. The
420 next time the command is executed, the shell checks the saved path to see
421 that it is still valid, and if so, avoids repeating the path search.
422 Tracked aliases can be listed and created using alias -t. Note that
423 changing the PATH parameter clears the saved paths for all tracked
424 aliases. If the trackall option is set (i.e. set -o trackall or set -h),
425 the shell tracks all commands. This option is set automatically for non-
426 interactive shells. For interactive shells, only the following commands
427 are automatically tracked: cat(1), cc(1), chmod(1), cp(1), date(1),
428 ed(1), emacs(1), grep(1), ls(1), make(1), mv(1), pr(1), rm(1), sed(1),
429 sh(1), vi(1), and who(1).
430 Substitution
432 The first step the shell takes in executing a simple-command is to per‐
433 form substitutions on the words of the command. There are three kinds of
434 substitution: parameter, command, and arithmetic. Parameter substitu‐
435 tions, which are described in detail in the next section, take the form
436 $name or ${...}; command substitutions take the form $(command) or (dep‐
437 recated) `command`; and arithmetic substitutions take the form
438 $((expression)).
439 If a substitution appears outside of double quotes, the results of the
441 substitution are generally subject to word or field splitting according
442 to the current value of the IFS parameter. The IFS parameter specifies a
443 list of octets which are used to break a string up into several words;
444 any octets from the set space, tab, and newline that appear in the IFS
445 octets are called “IFS whitespace”. Sequences of one or more IFS white‐
446 space octets, in combination with zero or one non-IFS whitespace octets,
447 delimit a field. As a special case, leading and trailing IFS whitespace
448 and trailing IFS non-whitespace are stripped (i.e. no leading or trailing
449 empty field is created by it); leading non-IFS whitespace does create an
450 empty field.
451 Example: If IFS is set to “<space>:”, and VAR is set to
453 “<space>A<space>:<space><space>B::D”, the substitution for $VAR results
454 in four fields: ‘A’, ‘B’, ‘’ (an empty field), and ‘D’. Note that if the
455 IFS parameter is set to the NULL string, no field splitting is done; if
456 the parameter is unset, the default value of space, tab, and newline is
457 used.
458 Also, note that the field splitting applies only to the immediate result
460 of the substitution. Using the previous example, the substitution for
461 $VAR:E results in the fields: ‘A’, ‘B’, ‘’, and ‘D:E’, not ‘A’, ‘B’, ‘’,
462 ‘D’, and ‘E’. This behavior is POSIX compliant, but incompatible with
463 some other shell implementations which do field splitting on the word
464 which contained the substitution or use IFS as a general whitespace
465 delimiter.
466 The results of substitution are, unless otherwise specified, also subject
468 to brace expansion and file name expansion (see the relevant sections
469 below).
470 A command substitution is replaced by the output generated by the speci‐
472 fied command which is run in a subshell. For $(command) substitutions,
473 normal quoting rules are used when command is parsed; however, for the
474 deprecated `command` form, a ‘\’ followed by any of ‘$’, ‘`’, or ‘\’ is
475 stripped (a ‘\’ followed by any other character is unchanged). As a spe‐
476 cial case in command substitutions, a command of the form <file is inter‐
477 preted to mean substitute the contents of file. Note that $(<foo) has
478 the same effect as $(cat foo).
479 Note that some shells do not use a recursive parser for command substitu‐
481 tions, leading to failure for certain constructs; to be portable, use as
482 workaround ‘x=$(cat) <<"EOF"’ (or the newline-keeping ‘x=<<"EOF"’ exten‐
483 sion) instead to merely slurp the string. IEEE Std 1003.1 (“POSIX.1”)
484 recommends to use case statements of the form ‘x=$(case $foo in (bar)
485 echo $bar ;; (*) echo $baz ;; esac)’ instead, which would work but not
486 serve as example for this portability issue.
487 x=$(case $foo in bar) echo $bar ;; *) echo $baz ;; esac)
489 # above fails to parse on old shells; below is the workaround
490 x=$(eval $(cat)) <<"EOF"
491 case $foo in bar) echo $bar ;; *) echo $baz ;; esac
492 EOF
493 Arithmetic substitutions are replaced by the value of the specified
495 expression. For example, the command print $((2+3*4)) displays 14. See
496 Arithmetic expressions for a description of an expression.
497 Parameters
499 Parameters are shell variables; they can be assigned values and their
500 values can be accessed using a parameter substitution. A parameter name
501 is either one of the special single punctuation or digit character param‐
502 eters described below, or a letter followed by zero or more letters or
503 digits (‘_’ counts as a letter). The latter form can be treated as
504 arrays by appending an array index of the form [expr] where expr is an
505 arithmetic expression. Array indices in mksh are limited to the range 0
506 through 4294967295, inclusive. That is, they are a 32-bit unsigned inte‐
507 ger.
508 Parameter substitutions take the form $name, ${name}, or ${name[expr]}
510 where name is a parameter name. Substitution of all array elements with
511 ${name[*]} and ${name[@]} works equivalent to $* and $@ for positional
512 parameters. If substitution is performed on a parameter (or an array
513 parameter element) that is not set, a null string is substituted unless
514 the nounset option (set -o nounset or set -u) is set, in which case an
515 error occurs.
516 Parameters can be assigned values in a number of ways. First, the shell
518 implicitly sets some parameters like ‘#’, ‘PWD’, and ‘$’; this is the
519 only way the special single character parameters are set. Second, param‐
520 eters are imported from the shell's environment at startup. Third,
521 parameters can be assigned values on the command line: for example,
522 FOO=bar sets the parameter “FOO” to “bar”; multiple parameter assignments
523 can be given on a single command line and they can be followed by a sim‐
524 ple-command, in which case the assignments are in effect only for the
525 duration of the command (such assignments are also exported; see below
526 for the implications of this). Note that both the parameter name and the
527 ‘=’ must be unquoted for the shell to recognise a parameter assignment.
528 The construct FOO+=baz is also recognised; the old and new values are
529 immediately concatenated. The fourth way of setting a parameter is with
530 the export, global, readonly, and typeset commands; see their descrip‐
531 tions in the Command execution section. Fifth, for and select loops set
532 parameters as well as the getopts, read, and set -A commands. Lastly,
533 parameters can be assigned values using assignment operators inside
534 arithmetic expressions (see Arithmetic expressions below) or using the
535 ${name=value} form of the parameter substitution (see below).
536 Parameters with the export attribute (set using the export or typeset -x
538 commands, or by parameter assignments followed by simple commands) are
539 put in the environment (see environ(7)) of commands run by the shell as
540 name=value pairs. The order in which parameters appear in the environ‐
541 ment of a command is unspecified. When the shell starts up, it extracts
542 parameters and their values from its environment and automatically sets
543 the export attribute for those parameters.
544 Modifiers can be applied to the ${name} form of parameter substitution:
546 ${name:-word}
548 If name is set and not NULL, it is substituted; otherwise, word
549 is substituted.
550 ${name:+word}
552 If name is set and not NULL, word is substituted; otherwise,
553 nothing is substituted.
554 ${name:=word}
556 If name is set and not NULL, it is substituted; otherwise, it is
557 assigned word and the resulting value of name is substituted.
558 ${name:?word}
560 If name is set and not NULL, it is substituted; otherwise, word
561 is printed on standard error (preceded by name:) and an error
562 occurs (normally causing termination of a shell script, function,
563 or script sourced using the ‘.’ built-in). If word is omitted,
564 the string “parameter null or not set” is used instead. Cur‐
565 rently a bug, if word is a variable which expands to the null
566 string, the error message is also printed.
567 Note that, for all of the above, word is actually considered quoted, and
569 special parsing rules apply. The parsing rules also differ on whether
570 the expression is double-quoted: word then uses double-quoting rules,
571 except for the double quote itself (‘"’) and the closing brace, which, if
572 backslash escaped, gets quote removal applied.
573 In the above modifiers, the ‘:’ can be omitted, in which case the condi‐
575 tions only depend on name being set (as opposed to set and not NULL). If
576 word is needed, parameter, command, arithmetic, and tilde substitution
577 are performed on it; if word is not needed, it is not evaluated.
578 The following forms of parameter substitution can also be used (if name
580 is an array, its element #0 will be substituted in a scalar context):
581 ${#name}
583 The number of positional parameters if name is ‘*’, ‘@’, or not
584 specified; otherwise the length (in characters) of the string
585 value of parameter name.
586 ${#name[*]}
588 ${#name[@]}
589 The number of elements in the array name.
590 ${%name}
592 The width (in screen columns) of the string value of parameter
593 name, or -1 if ${name} contains a control character.
594 ${!name}
596 The name of the variable referred to by name. This will be name
597 except when name is a name reference (bound variable), created by
598 the nameref command (which is an alias for typeset -n).
599 ${!name[*]}
601 ${!name[@]}
602 The names of indices (keys) in the array name.
603 ${name#pattern}
605 ${name##pattern}
606 If pattern matches the beginning of the value of parameter name,
607 the matched text is deleted from the result of substitution. A
608 single ‘#’ results in the shortest match, and two of them result
609 in the longest match. Cannot be applied to a vector (${*} or
610 ${@} or ${array[*]} or ${array[@]}).
611 ${name%pattern}
613 ${name%%pattern}
614 Like ${..#..} substitution, but it deletes from the end of the
615 value. Cannot be applied to a vector.
616 ${name/pattern/string}
618 ${name//pattern/string}
619 Like ${..#..} substitution, but it replaces the longest match of
620 pattern, anchored anywhere in the value, with string. If pattern
621 begins with ‘#’, it is anchored at the beginning of the value; if
622 it begins with ‘%’, it is anchored at the end. A single ‘/’
623 replaces the first occurence of the search pattern, and two of
624 them replace all occurences. If /string is omitted, the pattern
625 is replaced by the empty string, i.e. deleted. Cannot be applied
626 to a vector. Inefficiently implemented.
627 ${name:pos:len}
629 The first len characters of name, starting at position pos, are
630 substituted. Both pos and :len are optional. If pos is nega‐
631 tive, counting starts at the end of the string; if it is omitted,
632 it defaults to 0. If len is omitted or greater than the length
633 of the remaining string, all of it is substituted. Both pos and
634 len are evaluated as arithmetic expressions. Currently, pos must
635 start with a space, opening parenthesis or digit to be recog‐
636 nised. Cannot be applied to a vector.
637 ${name@#}
639 The internal hash of the expansion of name. At the moment, this
640 is OAAT1 (Bob Jenkins' one-at-a-time hash with an initialisation
641 value of 0x00000100), this will change for R41. This is the hash
642 the shell uses internally for its associative arrays.
643 Note that pattern may need extended globbing pattern (@(...)), single
645 ('...') or double ("...") quote escaping unless -o sh is set.
646 The following special parameters are implicitly set by the shell and can‐
648 not be set directly using assignments:
649 ! Process ID of the last background process started. If no back‐
651 ground processes have been started, the parameter is not set.
652 # The number of positional parameters ($1, $2, etc.).
654 $ The PID of the shell, or the PID of the original shell if it is a
656 subshell. Do NOT use this mechanism for generating temporary
657 file names; see mktemp(1) instead.
658 - The concatenation of the current single letter options (see the
660 set command below for a list of options).
661 ? The exit status of the last non-asynchronous command executed.
663 If the last command was killed by a signal, $? is set to 128 plus
664 the signal number.
665 0 The name of the shell, determined as follows: the first argument
667 to mksh if it was invoked with the -c option and arguments were
668 given; otherwise the file argument, if it was supplied; or else
669 the basename the shell was invoked with (i.e. argv[0]). $0 is
670 also set to the name of the current script or the name of the
671 current function, if it was defined with the function keyword
672 (i.e. a Korn shell style function).
673 1 .. 9 The first nine positional parameters that were supplied to the
675 shell, function, or script sourced using the ‘.’ built-in. Fur‐
676 ther positional parameters may be accessed using ${number}.
677 * All positional parameters (except 0), i.e. $1, $2, $3, ...
679 If used outside of double quotes, parameters are separate words
680 (which are subjected to word splitting); if used within double
681 quotes, parameters are separated by the first character of the
682 IFS parameter (or the empty string if IFS is NULL).
683 @ Same as $*, unless it is used inside double quotes, in which case
685 a separate word is generated for each positional parameter. If
686 there are no positional parameters, no word is generated. $@ can
687 be used to access arguments, verbatim, without losing NULL argu‐
688 ments or splitting arguments with spaces.
689 The following parameters are set and/or used by the shell:
691 _ (underscore) When an external command is executed by the
693 shell, this parameter is set in the environment of the new
694 process to the path of the executed command. In interactive
695 use, this parameter is also set in the parent shell to the
696 last word of the previous command.
697 CDPATH Search path for the cd built-in command. It works the same
699 way as PATH for those directories not beginning with ‘/’ in
700 cd commands. Note that if CDPATH is set and does not con‐
701 tain ‘.’ or contains an empty path, the current directory is
702 not searched. Also, the cd built-in command will display
703 the resulting directory when a match is found in any search
704 path other than the empty path.
705 COLUMNS Set to the number of columns on the terminal or window.
707 Always set, defaults to 80, unless the value as reported by
708 stty(1) is non-zero and sane enough; similar for LINES.
709 This parameter is used by the interactive line editing
710 modes, and by the select, set -o, and kill -l commands to
711 format information columns.
712 ENV If this parameter is found to be set after any profile files
714 are executed, the expanded value is used as a shell startup
715 file. It typically contains function and alias definitions.
716 ERRNO Integer value of the shell's errno variable. It indicates
718 the reason the last system call failed. Not yet imple‐
719 mented.
720 EXECSHELL If set, this parameter is assumed to contain the shell that
722 is to be used to execute commands that execve(2) fails to
723 execute and which do not start with a “#!shell” sequence.
724 FCEDIT The editor used by the fc command (see below).
726 FPATH Like PATH, but used when an undefined function is executed
728 to locate the file defining the function. It is also
729 searched when a command can't be found using PATH. See
730 Functions below for more information.
731 HISTFILE The name of the file used to store command history. When
733 assigned to, history is loaded from the specified file.
734 Also, several invocations of the shell will share history if
735 their HISTFILE parameters all point to the same file.
736 Note: If HISTFILE isn't set, no history file is used. This
738 is different from AT&T UNIX ksh.
739 HISTSIZE The number of commands normally stored for history. The
741 default is 500.
742 HOME The default directory for the cd command and the value sub‐
744 stituted for an unqualified ~ (see Tilde expansion below).
745 IFS Internal field separator, used during substitution and by
747 the read command, to split values into distinct arguments;
748 normally set to space, tab, and newline. See Substitution
749 above for details.
750 Note: This parameter is not imported from the environment
752 when the shell is started.
753 KSHEGID The effective group id of the shell.
755 KSHGID The real group id of the shell.
757 KSHUID The real user id of the shell.
759 KSH_VERSION The name and version of the shell (read-only). See also the
761 version commands in Emacs editing mode and Vi editing mode
762 sections, below.
763 LINENO The line number of the function or shell script that is cur‐
765 rently being executed.
766 LINES Set to the number of lines on the terminal or window.
768 Always set, defaults to 24.
769 OLDPWD The previous working directory. Unset if cd has not suc‐
771 cessfully changed directories since the shell started, or if
772 the shell doesn't know where it is.
773 OPTARG When using getopts, it contains the argument for a parsed
775 option, if it requires one.
776 OPTIND The index of the next argument to be processed when using
778 getopts. Assigning 1 to this parameter causes getopts to
779 process arguments from the beginning the next time it is
780 invoked.
781 PATH A colon separated list of directories that are searched when
783 looking for commands and files sourced using the ‘.’ command
784 (see below). An empty string resulting from a leading or
785 trailing colon, or two adjacent colons, is treated as a ‘.’
786 (the current directory).
787 PGRP The process ID of the shell's process group leader.
789 PIPESTATUS An array containing the errorlevel (exit status) codes, one
791 by one, of the last pipeline run in the foreground.
792 PPID The process ID of the shell's parent.
794 PS1 The primary prompt for interactive shells. Parameter, com‐
796 mand, and arithmetic substitutions are performed, and ‘!’ is
797 replaced with the current command number (see the fc command
798 below). A literal ‘!’ can be put in the prompt by placing
799 ‘!!’ in PS1.
800 The default prompt is ‘$ ’ for non-root users, ‘# ’ for
802 root. If mksh is invoked by root and PS1 does not contain a
803 ‘#’ character, the default value will be used even if PS1
804 already exists in the environment.
805 The mksh distribution comes with a sample dot.mkshrc con‐
807 taining a sophisticated example, but you might like the fol‐
808 lowing one (note that ${HOSTNAME:=$(hostname)} and the root-
809 vs-user distinguishing clause are (in this example) executed
810 at PS1 assignment time, while the $USER and $PWD are escaped
811 and thus will be evaluated each time a prompt is displayed):
812 PS1='${USER:=$(id -un)}'"@${HOSTNAME:=$(hostname)}:\$PWD $(
814 if (( USER_ID )); then print \$; else print \#; fi) "
815 Note that since the command-line editors try to figure out
817 how long the prompt is (so they know how far it is to the
818 edge of the screen), escape codes in the prompt tend to mess
819 things up. You can tell the shell not to count certain
820 sequences (such as escape codes) by prefixing your prompt
821 with a character (such as Ctrl-A) followed by a carriage
822 return and then delimiting the escape codes with this char‐
823 acter. Any occurences of that character in the prompt are
824 not printed. By the way, don't blame me for this hack; it's
825 derived from the original ksh88(1), which did print the
826 delimiter character so you were out of luck if you did not
827 have any non-printing characters.
828 Since Backslashes and other special characters may be inter‐
830 preted by the shell, to set PS1 either escape the backslash
831 itself, or use double quotes. The latter is more practical.
832 This is a more complex example, avoiding to directly enter
833 special characters (for example with ^V in the emacs editing
834 mode), which embeds the current working directory, in
835 reverse video (colour would work, too), in the prompt
836 string:
837 x=$(print \\001)
839 PS1="$x$(print \\r)$x$(tput smso)$x\$PWD$x$(tput rmso)$x> "
840 Due to pressure from David G. Korn, mksh now also supports
842 the following form:
843 PS1=$'\1\r\1\e[7m\1$PWD\1\e[0m\1> '
845 PS2 Secondary prompt string, by default ‘> ’, used when more
847 input is needed to complete a command.
848 PS3 Prompt used by the select statement when reading a menu
850 selection. The default is ‘#? ’.
851 PS4 Used to prefix commands that are printed during execution
853 tracing (see the set -x command below). Parameter, command,
854 and arithmetic substitutions are performed before it is
855 printed. The default is ‘+ ’.
856 PWD The current working directory. May be unset or NULL if the
858 shell doesn't know where it is.
859 RANDOM Each time RANDOM is referenced, it is assigned a number
861 between 0 and 32767 from a Linear Congruential PRNG first.
862 REPLY Default parameter for the read command if no names are
864 given. Also used in select loops to store the value that is
865 read from standard input.
866 SECONDS The number of seconds since the shell started or, if the
868 parameter has been assigned an integer value, the number of
869 seconds since the assignment plus the value that was
870 assigned.
871 TMOUT If set to a positive integer in an interactive shell, it
873 specifies the maximum number of seconds the shell will wait
874 for input after printing the primary prompt (PS1). If the
875 time is exceeded, the shell exits.
876 TMPDIR The directory temporary shell files are created in. If this
878 parameter is not set, or does not contain the absolute path
879 of a writable directory, temporary files are created in
880 /tmp.
881 USER_ID The effective user id of the shell.
883 Tilde expansion
885 Tilde expansion which is done in parallel with parameter substitution, is
886 done on words starting with an unquoted ‘~’. The characters following
887 the tilde, up to the first ‘/’, if any, are assumed to be a login name.
888 If the login name is empty, ‘+’, or ‘-’, the value of the HOME, PWD, or
889 OLDPWD parameter is substituted, respectively. Otherwise, the password
890 file is searched for the login name, and the tilde expression is substi‐
891 tuted with the user's home directory. If the login name is not found in
892 the password file or if any quoting or parameter substitution occurs in
893 the login name, no substitution is performed.
894 In parameter assignments (such as those preceding a simple-command or
896 those occurring in the arguments of alias, export, global, readonly, and
897 typeset), tilde expansion is done after any assignment (i.e. after the
898 equals sign) or after an unquoted colon (‘:’); login names are also
899 delimited by colons.
900 The home directory of previously expanded login names are cached and re-
902 used. The alias -d command may be used to list, change, and add to this
903 cache (e.g. alias -d fac=/usr/local/facilities; cd ~fac/bin).
904 Brace expansion (alteration)
906 Brace expressions take the following form:
907 prefix{str1,...,strN}suffix
909 The expressions are expanded to N words, each of which is the concatena‐
911 tion of prefix, stri, and suffix (e.g. “a{c,b{X,Y},d}e” expands to four
912 words: “ace”, “abXe”, “abYe”, and “ade”). As noted in the example, brace
913 expressions can be nested and the resulting words are not sorted. Brace
914 expressions must contain an unquoted comma (‘,’) for expansion to occur
915 (e.g. {} and {foo} are not expanded). Brace expansion is carried out
916 after parameter substitution and before file name generation.
917 File name patterns
919 A file name pattern is a word containing one or more unquoted ‘?’, ‘*’,
920 ‘+’, ‘@’, or ‘!’ characters or “[..]” sequences. Once brace expansion
921 has been performed, the shell replaces file name patterns with the sorted
922 names of all the files that match the pattern (if no files match, the
923 word is left unchanged). The pattern elements have the following mean‐
924 ing:
925 ? Matches any single character.
927 * Matches any sequence of octets.
929 [..] Matches any of the octets inside the brackets. Ranges of octets
931 can be specified by separating two octets by a ‘-’ (e.g. “[a0-9]”
932 matches the letter ‘a’ or any digit). In order to represent
933 itself, a ‘-’ must either be quoted or the first or last octet in
934 the octet list. Similarly, a ‘]’ must be quoted or the first
935 octet in the list if it is to represent itself instead of the end
936 of the list. Also, a ‘!’ appearing at the start of the list has
937 special meaning (see below), so to represent itself it must be
938 quoted or appear later in the list.
939 [!..] Like [..], except it matches any octet not inside the brackets.
941 *(pattern|...|pattern)
943 Matches any string of octets that matches zero or more occur‐
944 rences of the specified patterns. Example: The pattern
945 *(foo|bar) matches the strings “”, “foo”, “bar”, “foobarfoo”,
946 etc.
947 +(pattern|...|pattern)
949 Matches any string of octets that matches one or more occurrences
950 of the specified patterns. Example: The pattern +(foo|bar)
951 matches the strings “foo”, “bar”, “foobar”, etc.
952 ?(pattern|...|pattern)
954 Matches the empty string or a string that matches one of the
955 specified patterns. Example: The pattern ?(foo|bar) only matches
956 the strings “”, “foo”, and “bar”.
957 @(pattern|...|pattern)
959 Matches a string that matches one of the specified patterns.
960 Example: The pattern @(foo|bar) only matches the strings “foo”
961 and “bar”.
962 !(pattern|...|pattern)
964 Matches any string that does not match one of the specified pat‐
965 terns. Examples: The pattern !(foo|bar) matches all strings
966 except “foo” and “bar”; the pattern !(*) matches no strings; the
967 pattern !(?)* matches all strings (think about it).
968 Note that mksh (and pdksh) never matches ‘.’ and ‘..’, but AT&T UNIX ksh,
970 Bourne sh, and GNU bash do.
971 Note that none of the above pattern elements match either a period (‘.’)
973 at the start of a file name or a slash (‘/’), even if they are explicitly
974 used in a [..] sequence; also, the names ‘.’ and ‘..’ are never matched,
975 even by the pattern ‘.*’.
976 If the markdirs option is set, any directories that result from file name
978 generation are marked with a trailing ‘/’.
979 Input/output redirection
981 When a command is executed, its standard input, standard output, and
982 standard error (file descriptors 0, 1, and 2, respectively) are normally
983 inherited from the shell. Three exceptions to this are commands in pipe‐
984 lines, for which standard input and/or standard output are those set up
985 by the pipeline, asynchronous commands created when job control is dis‐
986 abled, for which standard input is initially set to be from /dev/null,
987 and commands for which any of the following redirections have been speci‐
988 fied:
989 > file Standard output is redirected to file. If file does not
991 exist, it is created; if it does exist, is a regular file,
992 and the noclobber option is set, an error occurs; otherwise,
993 the file is truncated. Note that this means the command cmd
994 <foo >foo will open foo for reading and then truncate it when
995 it opens it for writing, before cmd gets a chance to actually
996 read foo.
997 >| file Same as >, except the file is truncated, even if the
999 noclobber option is set.
1000 >> file Same as >, except if file exists it is appended to instead of
1002 being truncated. Also, the file is opened in append mode, so
1003 writes always go to the end of the file (see open(2)).
1004 < file Standard input is redirected from file, which is opened for
1006 reading.
1007 <> file Same as <, except the file is opened for reading and writing.
1009 << marker After reading the command line containing this kind of redi‐
1011 rection (called a “here document”), the shell copies lines
1012 from the command source into a temporary file until a line
1013 matching marker is read. When the command is executed, stan‐
1014 dard input is redirected from the temporary file. If marker
1015 contains no quoted characters, the contents of the temporary
1016 file are processed as if enclosed in double quotes each time
1017 the command is executed, so parameter, command, and arith‐
1018 metic substitutions are performed, along with backslash (‘\’)
1019 escapes for ‘$’, ‘`’, ‘\’, and ‘\newline’, but not for ‘"’.
1020 If multiple here documents are used on the same command line,
1021 they are saved in order.
1022 If no marker is given, the here document ends at the next <<
1024 and substitution will be performed. If marker is only a set
1025 of either single “''” or double ‘""’ quotes with nothing in
1026 between, the here document ends at the next empty line and
1027 substitution will not be performed.
1028 <<- marker Same as <<, except leading tabs are stripped from lines in
1030 the here document.
1031 <<< word Same as <<, except that word is the here document. This is
1033 called a here string.
1034 <& fd Standard input is duplicated from file descriptor fd. fd can
1036 be a number, indicating the number of an existing file
1037 descriptor; the letter ‘p’, indicating the file descriptor
1038 associated with the output of the current co-process; or the
1039 character ‘-’, indicating standard input is to be closed.
1040 Note that fd is limited to a single digit in most shell
1041 implementations.
1042 >& fd Same as <&, except the operation is done on standard output.
1044 &> file Same as > file 2>&1. This is a GNU bash extension supported
1046 by mksh which also supports the preceding explicit fd number,
1047 for example, 3&> file is the same as 3> file 2>&3 in mksh but
1048 a syntax error in GNU bash.
1049 &>| file, &>> file, &>& fd
1051 Same as >| file, >> file, or >& fd, followed by 2>&1, as
1052 above. These are mksh extensions.
1053 In any of the above redirections, the file descriptor that is redirected
1055 (i.e. standard input or standard output) can be explicitly given by pre‐
1056 ceding the redirection with a number (portably, only a single digit).
1057 Parameter, command, and arithmetic substitutions, tilde substitutions,
1058 and (if the shell is interactive) file name generation are all performed
1059 on the file, marker, and fd arguments of redirections. Note, however,
1060 that the results of any file name generation are only used if a single
1061 file is matched; if multiple files match, the word with the expanded file
1062 name generation characters is used. Note that in restricted shells,
1063 redirections which can create files cannot be used.
1064 For simple-commands, redirections may appear anywhere in the command; for
1066 compound-commands (if statements, etc.), any redirections must appear at
1067 the end. Redirections are processed after pipelines are created and in
1068 the order they are given, so the following will print an error with a
1069 line number prepended to it:
1070 $ cat /foo/bar 2>&1 >/dev/null | pr -n -t
1072 File descriptors created by input/output redirections are private to the
1074 Korn shell, but passed to sub-processes if -o posix or -o sh is set.
1075 Arithmetic expressions
1077 Integer arithmetic expressions can be used with the let command, inside
1078 $((..)) expressions, inside array references (e.g. name[expr]), as
1079 numeric arguments to the test command, and as the value of an assignment
1080 to an integer parameter.
1081 Expressions are calculated using signed arithmetic and the mksh_ari_t
1083 type (a 32-bit signed integer), unless they begin with a sole ‘#’ charac‐
1084 ter, in which case they use mksh_uari_t (a 32-bit unsigned integer).
1085 Expressions may contain alpha-numeric parameter identifiers, array refer‐
1087 ences, and integer constants and may be combined with the following C
1088 operators (listed and grouped in increasing order of precedence):
1089 Unary operators:
1091 + - ! ~ ++ --
1093 Binary operators:
1095 ,
1097 = *= /= %= += -= <<= >>= &= ^= |=
1098 ||
1099 &&
1100 |
1101 ^
1102 &
1103 == !=
1104 < <= >= >
1105 << >>
1106 + -
1107 * / %
1108 Ternary operators:
1110 ?: (precedence is immediately higher than assignment)
1112 Grouping operators:
1114 ( )
1116 Integer constants and expressions are calculated using the mksh_ari_t (if
1118 signed) or mksh_uari_t (if unsigned) type, and are limited to 32 bits.
1119 Overflows wrap silently. Integer constants may be specified with arbi‐
1120 trary bases using the notation base#number, where base is a decimal inte‐
1121 ger specifying the base, and number is a number in the specified base.
1122 Additionally, integers may be prefixed with ‘0X’ or ‘0x’ (specifying base
1123 16), similar to AT&T UNIX ksh, or ‘0’ (base 8), as an mksh extension, in
1124 all forms of arithmetic expressions, except as numeric arguments to the
1125 test command. As a special mksh extension, numbers to the base of one
1126 are treated as either (8-bit transparent) ASCII or Unicode codepoints,
1127 depending on the shell's utf8-mode flag (current setting). The AT&T UNIX
1128 ksh93 syntax of “'x'” instead of “1#x” is also supported. Note that NUL
1129 bytes (integral value of zero) cannot be used. In Unicode mode, raw
1130 octets are mapped into the range EF80..EFFF as in OPTU-8, which is in the
1131 PUA and has been assigned by CSUR for this use. If more than one octet
1132 in ASCII mode, or a sequence of more than one octet not forming a valid
1133 and minimal CESU-8 sequence is passed, the behaviour is undefined (usu‐
1134 ally, the shell aborts with a parse error, but rarely, it succeeds, e.g.
1135 on the sequence C2 20). That's why you should always use ASCII mode
1136 unless you know that the input is well-formed UTF-8 in the range of
1137 0000..FFFD.
1138 The operators are evaluated as follows:
1140 unary +
1142 Result is the argument (included for completeness).
1143 unary -
1145 Negation.
1146 ! Logical NOT; the result is 1 if argument is zero, 0 if not.
1148 ~ Arithmetic (bit-wise) NOT.
1150 ++ Increment; must be applied to a parameter (not a literal or
1152 other expression). The parameter is incremented by 1.
1153 When used as a prefix operator, the result is the incre‐
1154 mented value of the parameter; when used as a postfix oper‐
1155 ator, the result is the original value of the parameter.
1156 -- Similar to ++, except the parameter is decremented by 1.
1158 , Separates two arithmetic expressions; the left-hand side is
1160 evaluated first, then the right. The result is the value
1161 of the expression on the right-hand side.
1162 = Assignment; the variable on the left is set to the value on
1164 the right.
1165 *= /= += -= <<= >>= &= ^= |=
1167 Assignment operators. ⟨var⟩⟨op⟩=⟨expr⟩ is the same as
1168 ⟨var⟩=⟨var⟩⟨op⟩⟨expr⟩, with any operator precedence in
1169 ⟨expr⟩ preserved. For example, “var1 *= 5 + 3” is the same
1170 as specifying “var1 = var1 * (5 + 3)”.
1171 || Logical OR; the result is 1 if either argument is non-zero,
1173 0 if not. The right argument is evaluated only if the left
1174 argument is zero.
1175 && Logical AND; the result is 1 if both arguments are non-
1177 zero, 0 if not. The right argument is evaluated only if
1178 the left argument is non-zero.
1179 | Arithmetic (bit-wise) OR.
1181 ^ Arithmetic (bit-wise) XOR (exclusive-OR).
1183 & Arithmetic (bit-wise) AND.
1185 == Equal; the result is 1 if both arguments are equal, 0 if
1187 not.
1188 != Not equal; the result is 0 if both arguments are equal, 1
1190 if not.
1191 < Less than; the result is 1 if the left argument is less
1193 than the right, 0 if not.
1194 <= >= >
1196 Less than or equal, greater than or equal, greater than.
1197 See <.
1198 << >> Shift left (right); the result is the left argument with
1200 its bits shifted left (right) by the amount given in the
1201 right argument.
1202 + - * /
1204 Addition, subtraction, multiplication, and division.
1205 % Remainder; the result is the remainder of the division of
1207 the left argument by the right. The sign of the result is
1208 unspecified if either argument is negative.
1209 ⟨arg1⟩?⟨arg2⟩:⟨arg3⟩
1211 If ⟨arg1⟩ is non-zero, the result is ⟨arg2⟩; otherwise the
1212 result is ⟨arg3⟩.
1213 Co-processes
1215 A co-process (which is a pipeline created with the ‘|&’ operator) is an
1216 asynchronous process that the shell can both write to (using print -p)
1217 and read from (using read -p). The input and output of the co-process
1218 can also be manipulated using >&p and <&p redirections, respectively.
1219 Once a co-process has been started, another can't be started until the
1220 co-process exits, or until the co-process's input has been redirected
1221 using an exec n>&p redirection. If a co-process's input is redirected in
1222 this way, the next co-process to be started will share the output with
1223 the first co-process, unless the output of the initial co-process has
1224 been redirected using an exec n<&p redirection.
1225 Some notes concerning co-processes:
1227 · The only way to close the co-process's input (so the co-process reads
1229 an end-of-file) is to redirect the input to a numbered file descrip‐
1230 tor and then close that file descriptor: exec 3>&p; exec 3>&-
1231 · In order for co-processes to share a common output, the shell must
1233 keep the write portion of the output pipe open. This means that end-
1234 of-file will not be detected until all co-processes sharing the co-
1235 process's output have exited (when they all exit, the shell closes
1236 its copy of the pipe). This can be avoided by redirecting the output
1237 to a numbered file descriptor (as this also causes the shell to close
1238 its copy). Note that this behaviour is slightly different from the
1239 original Korn shell which closes its copy of the write portion of the
1240 co-process output when the most recently started co-process (instead
1241 of when all sharing co-processes) exits.
1242 · print -p will ignore SIGPIPE signals during writes if the signal is
1244 not being trapped or ignored; the same is true if the co-process
1245 input has been duplicated to another file descriptor and print -un is
1246 used.
1247 Functions
1249 Functions are defined using either Korn shell function function-name syn‐
1250 tax or the Bourne/POSIX shell function-name() syntax (see below for the
1251 difference between the two forms). Functions are like .‐scripts (i.e.
1252 scripts sourced using the ‘.’ built-in) in that they are executed in the
1253 current environment. However, unlike .‐scripts, shell arguments (i.e.
1254 positional parameters $1, $2, etc.) are never visible inside them. When
1255 the shell is determining the location of a command, functions are
1256 searched after special built-in commands, before regular and non-regular
1257 built-ins, and before the PATH is searched.
1258 An existing function may be deleted using unset -f function-name. A list
1260 of functions can be obtained using typeset +f and the function defini‐
1261 tions can be listed using typeset -f. The autoload command (which is an
1262 alias for typeset -fu) may be used to create undefined functions: when an
1263 undefined function is executed, the shell searches the path specified in
1264 the FPATH parameter for a file with the same name as the function which,
1265 if found, is read and executed. If after executing the file the named
1266 function is found to be defined, the function is executed; otherwise, the
1267 normal command search is continued (i.e. the shell searches the regular
1268 built-in command table and PATH). Note that if a command is not found
1269 using PATH, an attempt is made to autoload a function using FPATH (this
1270 is an undocumented feature of the original Korn shell).
1271 Functions can have two attributes, “trace” and “export”, which can be set
1273 with typeset -ft and typeset -fx, respectively. When a traced function
1274 is executed, the shell's xtrace option is turned on for the function's
1275 duration. The “export” attribute of functions is currently not used. In
1276 the original Korn shell, exported functions are visible to shell scripts
1277 that are executed.
1278 Since functions are executed in the current shell environment, parameter
1280 assignments made inside functions are visible after the function com‐
1281 pletes. If this is not the desired effect, the typeset command can be
1282 used inside a function to create a local parameter. Note that AT&T UNIX
1283 ksh93 uses static scoping (one global scope, one local scope per func‐
1284 tion), whereas mksh uses dynamic scoping (nested scopes of varying local‐
1285 ity). Note that special parameters (e.g. $$, $!) can't be scoped in this
1286 way.
1287 The exit status of a function is that of the last command executed in the
1289 function. A function can be made to finish immediately using the return
1290 command; this may also be used to explicitly specify the exit status.
1291 Functions defined with the function reserved word are treated differently
1293 in the following ways from functions defined with the () notation:
1294 · The $0 parameter is set to the name of the function (Bourne-style
1296 functions leave $0 untouched).
1297 · Parameter assignments preceding function calls are not kept in the
1299 shell environment (executing Bourne-style functions will keep assign‐
1300 ments).
1301 · OPTIND is saved/reset and restored on entry and exit from the func‐
1303 tion so getopts can be used properly both inside and outside the
1304 function (Bourne-style functions leave OPTIND untouched, so using
1305 getopts inside a function interferes with using getopts outside the
1306 function).
1307 · Bourne-style function definitions take precedence over alias derefer‐
1309 ences and remove alias definitions upon encounter, while aliases take
1310 precedence over Korn-style functions.
1311 In the future, the following differences will also be added:
1313 · A separate trap/signal environment will be used during the execution
1315 of functions. This will mean that traps set inside a function will
1316 not affect the shell's traps and signals that are not ignored in the
1317 shell (but may be trapped) will have their default effect in a func‐
1318 tion.
1319 · The EXIT trap, if set in a function, will be executed after the func‐
1321 tion returns.
1322 Command execution
1324 After evaluation of command-line arguments, redirections, and parameter
1325 assignments, the type of command is determined: a special built-in, a
1326 function, a regular built-in, or the name of a file to execute found
1327 using the PATH parameter. The checks are made in the above order. Spe‐
1328 cial built-in commands differ from other commands in that the PATH param‐
1329 eter is not used to find them, an error during their execution can cause
1330 a non-interactive shell to exit, and parameter assignments that are spec‐
1331 ified before the command are kept after the command completes. Regular
1332 built-in commands are different only in that the PATH parameter is not
1333 used to find them.
1334 The original ksh and POSIX differ somewhat in which commands are consid‐
1336 ered special or regular:
1337 POSIX special commands
1339 ., :, break, continue, eval, exec, exit, export, readonly, return, set,
1341 shift, trap, unset, wait
1342 Additional mksh special commands
1344 builtin, global, times, typeset
1346 Very special commands (non-POSIX)
1348 alias, readonly, set, typeset
1350 POSIX regular commands
1352 alias, bg, cd, command, false, fc, fg, getopts, jobs, kill, read, true,
1354 umask, unalias
1355 Additional mksh regular commands
1357 [, chdir, bind, cat, echo, let, mknod, print, printf, pwd, realpath,
1359 rename, sleep, test, ulimit, whence
1360 In the future, the additional mksh special and regular commands may be
1362 treated differently from the POSIX special and regular commands.
1363 Once the type of command has been determined, any command-line parameter
1365 assignments are performed and exported for the duration of the command.
1366 The following describes the special and regular built-in commands:
1368 . file [arg ...]
1370 This is called the “dot” command. Execute the commands in file in
1371 the current environment. The file is searched for in the directo‐
1372 ries of PATH. If arguments are given, the positional parameters
1373 may be used to access them while file is being executed. If no
1374 arguments are given, the positional parameters are those of the
1375 environment the command is used in.
1376 : [...]
1378 The null command. Exit status is set to zero.
1379 alias [-d | -t [-r] | +-x] [-p] [+] [name [=value] ...]
1381 Without arguments, alias lists all aliases. For any name without
1382 a value, the existing alias is listed. Any name with a value
1383 defines an alias (see Aliases above).
1384 When listing aliases, one of two formats is used. Normally,
1386 aliases are listed as name=value, where value is quoted. If
1387 options were preceded with ‘+’, or a lone ‘+’ is given on the com‐
1388 mand line, only name is printed.
1389 The -d option causes directory aliases which are used in tilde
1391 expansion to be listed or set (see Tilde expansion above).
1392 If the -p option is used, each alias is prefixed with the string
1394 “alias ”.
1395 The -t option indicates that tracked aliases are to be listed/set
1397 (values specified on the command line are ignored for tracked
1398 aliases). The -r option indicates that all tracked aliases are to
1399 be reset.
1400 The -x option sets (+x clears) the export attribute of an alias,
1402 or, if no names are given, lists the aliases with the export
1403 attribute (exporting an alias has no effect).
1404 bg [job ...]
1406 Resume the specified stopped job(s) in the background. If no jobs
1407 are specified, %+ is assumed. See Job control below for more
1408 information.
1409 bind [-l]
1411 The current bindings are listed. If the -l flag is given, bind
1412 instead lists the names of the functions to which keys may be
1413 bound. See Emacs editing mode for more information.
1414 bind [-m] string=[substitute] ...
1416 bind string=[editing-command] ...
1417 The specified editing command is bound to the given string, which
1418 should consist of a control character optionally preceded by one
1419 of the two prefix characters and optionally succeded by a tilde
1420 character. Future input of the string will cause the editing com‐
1421 mand to be immediately invoked. If the -m flag is given, the
1422 specified input string will afterwards be immediately replaced by
1423 the given substitute string which may contain editing commands but
1424 not other macros. If a tilde postfix is given, a tilde trailing
1425 the one or two prefices and the control character is ignored, any
1426 other trailing character will be processed afterwards.
1427 Control characters may be written using caret notation i.e. ^X
1429 represents Ctrl-X. Note that although only two prefix characters
1430 (usually ESC and ^X) are supported, some multi-character sequences
1431 can be supported.
1432 The following default bindings show how the arrow keys, the home,
1434 end and delete key on a BSD wsvt25, xterm-xfree86 or GNU screen
1435 terminal are bound (of course some escape sequences won't work out
1436 quite this nicely):
1437 bind '^X'=prefix-2
1439 bind '^[['=prefix-2
1440 bind '^XA'=up-history
1441 bind '^XB'=down-history
1442 bind '^XC'=forward-char
1443 bind '^XD'=backward-char
1444 bind '^X1~'=beginning-of-line
1445 bind '^X7~'=beginning-of-line
1446 bind '^XH'=beginning-of-line
1447 bind '^X4~'=end-of-line
1448 bind '^X8~'=end-of-line
1449 bind '^XF'=end-of-line
1450 bind '^X3~'=delete-char-forward
1451 break [level]
1453 Exit the levelth inner-most for, select, until, or while loop.
1454 level defaults to 1.
1455 builtin [--] command [arg ...]
1457 Execute the built-in command command.
1458 cat [-u] [file ...]
1460 Read files sequentially, in command line order, and write them to
1461 standard output. If a file is a single dash (‘-’) or absent, read
1462 from standard input. Unless compiled with MKSH_NO_EXTERNAL_CAT,
1463 if any options are given, an external cat(1) utility is invoked
1464 instead if called from the shell. For direct builtin calls, the
1465 POSIX -u option is supported as a no-op.
1466 cd [-L] [dir]
1468 cd -P [-e] [dir]
1469 chdir [-eLP] [dir]
1470 Set the working directory to dir. If the parameter CDPATH is set,
1471 it lists the search path for the directory containing dir. A NULL
1472 path means the current directory. If dir is found in any compo‐
1473 nent of the CDPATH search path other than the NULL path, the name
1474 of the new working directory will be written to standard output.
1475 If dir is missing, the home directory HOME is used. If dir is
1476 ‘-’, the previous working directory is used (see the OLDPWD param‐
1477 eter).
1478 If the -L option (logical path) is used or if the physical option
1480 isn't set (see the set command below), references to ‘..’ in dir
1481 are relative to the path used to get to the directory. If the -P
1482 option (physical path) is used or if the physical option is set,
1483 ‘..’ is relative to the filesystem directory tree. The PWD and
1484 OLDPWD parameters are updated to reflect the current and old work‐
1485 ing directory, respectively. If the -e option is set for physical
1486 filesystem traversal, and PWD could not be set, the exit code is
1487 1; greater than 1 if an error occurred, 0 otherwise.
1488 cd [-eLP] old new
1490 chdir [-eLP] old new
1491 The string new is substituted for old in the current directory,
1492 and the shell attempts to change to the new directory.
1493 command [-pVv] cmd [arg ...]
1495 If neither the -v nor -V option is given, cmd is executed exactly
1496 as if command had not been specified, with two exceptions:
1497 firstly, cmd cannot be a shell function; and secondly, special
1498 built-in commands lose their specialness (i.e. redirection and
1499 utility errors do not cause the shell to exit, and command assign‐
1500 ments are not permanent).
1501 If the -p option is given, a default search path is used instead
1503 of the current value of PATH, the actual value of which is system
1504 dependent.
1505 If the -v option is given, instead of executing cmd, information
1507 about what would be executed is given (and the same is done for
1508 arg ...). For special and regular built-in commands and func‐
1509 tions, their names are simply printed; for aliases, a command that
1510 defines them is printed; and for commands found by searching the
1511 PATH parameter, the full path of the command is printed. If no
1512 command is found (i.e. the path search fails), nothing is printed
1513 and command exits with a non-zero status. The -V option is like
1514 the -v option, except it is more verbose.
1515 continue [level]
1517 Jumps to the beginning of the levelth inner-most for, select,
1518 until, or while loop. level defaults to 1.
1519 echo [-Een] [arg ...]
1521 Warning: this utility is not portable; use the Korn shell builtin
1522 print or the much slower POSIX utility printf instead.
1523 Prints its arguments (separated by spaces) followed by a newline,
1525 to the standard output. The newline is suppressed if any of the
1526 arguments contain the backslash sequence ‘\c’. See the print com‐
1527 mand below for a list of other backslash sequences that are recog‐
1528 nised.
1529 The options are provided for compatibility with BSD shell scripts.
1531 The -n option suppresses the trailing newline, -e enables back‐
1532 slash interpretation (a no-op, since this is normally done), and
1533 -E suppresses backslash interpretation.
1534 If the posix or sh option is set or this is a direct builtin call,
1536 only the first argument is treated as an option, and only if it is
1537 exactly “-n”. Backslash interpretation is disabled.
1538 eval command ...
1540 The arguments are concatenated (with spaces between them) to form
1541 a single string which the shell then parses and executes in the
1542 current environment.
1543 exec [command [arg ...]]
1545 The command is executed without forking, replacing the shell
1546 process.
1547 If no command is given except for I/O redirection, the I/O redi‐
1549 rection is permanent and the shell is not replaced. Any file
1550 descriptors greater than 2 which are opened or dup(2)'d in this
1551 way are not made available to other executed commands (i.e. com‐
1552 mands that are not built-in to the shell). Note that the Bourne
1553 shell differs here; it does pass these file descriptors on.
1554 exit [status]
1556 The shell exits with the specified exit status. If status is not
1557 specified, the exit status is the current value of the $? parame‐
1558 ter.
1559 export [-p] [parameter[=value]]
1561 Sets the export attribute of the named parameters. Exported
1562 parameters are passed in the environment to executed commands. If
1563 values are specified, the named parameters are also assigned.
1564 If no parameters are specified, all parameters with the export
1566 attribute set are printed one per line; either their names, or, if
1567 a ‘-’ with no option letter is specified, name=value pairs, or,
1568 with -p, export commands defining all exported parameters, includ‐
1569 ing their values.
1570 false A command that exits with a non-zero status.
1572 fc [-e editor | -l [-n]] [-r] [first [last]]
1574 first and last select commands from the history. Commands can be
1575 selected by history number or a string specifying the most recent
1576 command starting with that string. The -l option lists the com‐
1577 mand on standard output, and -n inhibits the default command num‐
1578 bers. The -r option reverses the order of the list. Without -l,
1579 the selected commands are edited by the editor specified with the
1580 -e option, or if no -e is specified, the editor specified by the
1581 FCEDIT parameter (if this parameter is not set, /bin/ed is used),
1582 and then executed by the shell.
1583 fc -e - | -s [-g] [old=new] [prefix]
1585 Re-execute the selected command (the previous command by default)
1586 after performing the optional substitution of old with new. If -g
1587 is specified, all occurrences of old are replaced with new. The
1588 meaning of -e - and -s is identical: re-execute the selected com‐
1589 mand without invoking an editor. This command is usually accessed
1590 with the predefined alias r='fc -e -' or (deprecated; will be
1591 removed RSN) by prefixing an interactive mode input line with ‘!’
1592 (wbx extension).
1593 fg [job ...]
1595 Resume the specified job(s) in the foreground. If no jobs are
1596 specified, %+ is assumed. See Job control below for more informa‐
1597 tion.
1598 getopts optstring name [arg ...]
1600 Used by shell procedures to parse the specified arguments (or
1601 positional parameters, if no arguments are given) and to check for
1602 legal options. optstring contains the option letters that getopts
1603 is to recognise. If a letter is followed by a colon, the option
1604 is expected to have an argument. Options that do not take argu‐
1605 ments may be grouped in a single argument. If an option takes an
1606 argument and the option character is not the last character of the
1607 argument it is found in, the remainder of the argument is taken to
1608 be the option's argument; otherwise, the next argument is the
1609 option's argument.
1610 Each time getopts is invoked, it places the next option in the
1612 shell parameter name and the index of the argument to be processed
1613 by the next call to getopts in the shell parameter OPTIND. If the
1614 option was introduced with a ‘+’, the option placed in name is
1615 prefixed with a ‘+’. When an option requires an argument, getopts
1616 places it in the shell parameter OPTARG.
1617 When an illegal option or a missing option argument is encoun‐
1619 tered, a question mark or a colon is placed in name (indicating an
1620 illegal option or missing argument, respectively) and OPTARG is
1621 set to the option character that caused the problem. Furthermore,
1622 if optstring does not begin with a colon, a question mark is
1623 placed in name, OPTARG is unset, and an error message is printed
1624 to standard error.
1625 When the end of the options is encountered, getopts exits with a
1627 non-zero exit status. Options end at the first (non-option argu‐
1628 ment) argument that does not start with a ‘-’, or when a ‘--’
1629 argument is encountered.
1630 Option parsing can be reset by setting OPTIND to 1 (this is done
1632 automatically whenever the shell or a shell procedure is invoked).
1633 Warning: Changing the value of the shell parameter OPTIND to a
1635 value other than 1, or parsing different sets of arguments without
1636 resetting OPTIND, may lead to unexpected results.
1637 hash [-r] [name ...]
1639 Without arguments, any hashed executable command pathnames are
1640 listed. The -r option causes all hashed commands to be removed
1641 from the hash table. Each name is searched as if it were a com‐
1642 mand name and added to the hash table if it is an executable com‐
1643 mand.
1644 jobs [-lnp] [job ...]
1646 Display information about the specified job(s); if no jobs are
1647 specified, all jobs are displayed. The -n option causes informa‐
1648 tion to be displayed only for jobs that have changed state since
1649 the last notification. If the -l option is used, the process ID
1650 of each process in a job is also listed. The -p option causes
1651 only the process group of each job to be printed. See Job control
1652 below for the format of job and the displayed job.
1653 kill [-s signame | -signum | -signame] { job | pid | pgrp } ...
1655 Send the specified signal to the specified jobs, process IDs, or
1656 process groups. If no signal is specified, the TERM signal is
1657 sent. If a job is specified, the signal is sent to the job's
1658 process group. See Job control below for the format of job.
1659 kill -l [exit-status ...]
1661 Print the signal name corresponding to exit-status. If no argu‐
1662 ments are specified, a list of all the signals, their numbers, and
1663 a short description of them are printed.
1664 let [expression ...]
1666 Each expression is evaluated (see Arithmetic expressions above).
1667 If all expressions are successfully evaluated, the exit status is
1668 0 (1) if the last expression evaluated to non-zero (zero). If an
1669 error occurs during the parsing or evaluation of an expression,
1670 the exit status is greater than 1. Since expressions may need to
1671 be quoted, (( expr )) is syntactic sugar for let "expr".
1672 mknod [-m mode] name b|c major minor
1674 mknod [-m mode] name p
1675 Create a device special file. The file type may be b (block type
1676 device), c (character type device), or p (named pipe). The file
1677 created may be modified according to its mode (via the -m option),
1678 major (major device number), and minor (minor device number).
1679 See mknod(8) for further information.
1681 print [-nprsu[n] | -R [-en]] [argument ...]
1683 print prints its arguments on the standard output, separated by
1684 spaces and terminated with a newline. The -n option suppresses
1685 the newline. By default, certain C escapes are translated. These
1686 include these mentioned in Backslash expansion above, as well as
1687 ‘\c’, which is equivalent to using the -n option. Backslash
1688 expansion may be inhibited with the -r option. The -s option
1689 prints to the history file instead of standard output; the -u
1690 option prints to file descriptor n (n defaults to 1 if omitted);
1691 and the -p option prints to the co-process (see Co-processes
1692 above).
1693 The -R option is used to emulate, to some degree, the BSD echo(1)
1695 command which does not process ‘\’ sequences unless the -e option
1696 is given. As above, the -n option suppresses the trailing new‐
1697 line.
1698 printf format [arguments ...]
1700 Formatted output. Approximately the same as the utility printf,
1701 except that it uses the same Backslash expansion and I/O code as
1702 the rest of mksh. This is not normally part of mksh; however,
1703 distributors may have added this as builtin as a speed hack.
1704 pwd [-LP]
1706 Print the present working directory. If the -L option is used or
1707 if the physical option isn't set (see the set command below), the
1708 logical path is printed (i.e. the path used to cd to the current
1709 directory). If the -P option (physical path) is used or if the
1710 physical option is set, the path determined from the filesystem
1711 (by following ‘..’ directories to the root directory) is printed.
1712 read [-A | -a] [-d x] [-N z | -n z] [-p | -u[n]] [-t n] [-rs] [p ...]
1714 Reads a line of input, separates the input into fields using the
1715 IFS parameter (see Substitution above), and assigns each field to
1716 the specified parameters p. If no parameters are specified, the
1717 REPLY parameter is used to store the result. With the -A and -a
1718 options, only no or one parameter is accepted. If there are more
1719 parameters than fields, the extra parameters are set to the empty
1720 string or 0; if there are more fields than parameters, the last
1721 parameter is assigned the remaining fields (including the word
1722 separators).
1723 The options are as follows:
1725 -A Store the result into the parameter p (or REPLY) as array
1727 of words.
1728 -a Store the result without word splitting into the parameter
1730 p (or REPLY) as array of characters (wide characters if the
1731 utf8-mode option is enacted, octets otherwise).
1732 -d x Use the first byte of x, NUL if empty, instead of the ASCII
1734 newline character as input line delimiter.
1735 -N z Instead of reading till end-of-line, read exactly z bytes;
1737 less if EOF or a timeout occurs.
1738 -n z Instead of reading till end-of-line, read up to z bytes but
1740 return as soon as any bytes are read, e.g. from a slow ter‐
1741 minal device, or if EOF or a timeout occurs.
1742 -p Read from the currently active co-process, see Co-processes
1744 above for details on this.
1745 -u[n] Read from the file descriptor n (defaults to 0, i.e. stan‐
1747 dard input). The argument must immediately follow the
1748 option character.
1749 -t n Interrupt reading after n seconds (specified as positive
1751 decimal value with an optional fractional part).
1752 -r Normally, the ASCII backslash character escapes the special
1754 meaning of the following character and is stripped from the
1755 input; read does not stop when encountering a backslash-
1756 newline sequence and does not store that newline in the
1757 result. This option enables raw mode, in which backslashes
1758 are not processed.
1759 -s The input line is saved to the history.
1761 If the input is a terminal, both the -N and -n options set it into
1763 raw mode; they read an entire file if -1 is passed as z argument.
1764 The first parameter may have a question mark and a string appended
1766 to it, in which case the string is used as a prompt (printed to
1767 standard error before any input is read) if the input is a tty(4)
1768 (e.g. read nfoo?'number of foos: ').
1769 If no input is read or a timeout occurred, read exits with a non-
1771 zero status.
1772 Another handy set of tricks: If read is run in a loop such as
1774 while read foo; do ...; done then leading whitespace will be
1775 removed (IFS) and backslashes processed. You might want to use
1776 while IFS= read -r foo; do ...; done for pristine I/O. Similar‐
1777 ily, when using the -a option, use of the -r option might be pru‐
1778 dent; the same applies for:
1779 find . -type f -print0 | \
1781 while IFS= read -d '' -r filename; do
1782 print -r -- "found <${filename#./}>"
1783 done
1784 The inner loop will be executed in a subshell and variable changes
1786 cannot be propagated if executed in a pipeline:
1787 bar | baz | while read foo; do ...; done
1789 Use co-processes instead:
1791 bar | baz |&
1793 while read -p foo; do ...; done
1794 exec 3>&p; exec 3>&-
1795 readonly [-p] [parameter [=value] ...]
1797 Sets the read-only attribute of the named parameters. If values
1798 are given, parameters are set to them before setting the
1799 attribute. Once a parameter is made read-only, it cannot be unset
1800 and its value cannot be changed.
1801 If no parameters are specified, the names of all parameters with
1803 the read-only attribute are printed one per line, unless the -p
1804 option is used, in which case readonly commands defining all read-
1805 only parameters, including their values, are printed.
1806 realpath [--] name
1808 Prints the resolved absolute pathname corresponding to name. If
1809 name ends with a slash (‘/’), it's also checked for existence and
1810 whether it is a directory; otherwise, realpath returns 0 if the
1811 pathname either exists or can be created immediately, i.e. all but
1812 the last component exist and are directories.
1813 rename [--] from to
1815 Renames the file from to to. Both must be complete pathnames and
1816 on the same device. This builtin is intended for emergency situa‐
1817 tions where /bin/mv becomes unusable, and directly calls
1818 rename(2).
1819 return [status]
1821 Returns from a function or . script, with exit status status. If
1822 no status is given, the exit status of the last executed command
1823 is used. If used outside of a function or . script, it has the
1824 same effect as exit. Note that mksh treats both profile and ENV
1825 files as . scripts, while the original Korn shell only treats pro‐
1826 files as . scripts.
1827 set [+-abCefhiklmnprsUuvXx] [+-o option] [+-A name] [--] [arg ...]
1829 The set command can be used to set (-) or clear (+) shell options,
1830 set the positional parameters, or set an array parameter. Options
1831 can be changed using the +-o option syntax, where option is the
1832 long name of an option, or using the +-letter syntax, where letter
1833 is the option's single letter name (not all options have a single
1834 letter name). The following table lists both option letters (if
1835 they exist) and long names along with a description of what the
1836 option does:
1837 -A name
1839 Sets the elements of the array parameter name to arg ... If
1840 -A is used, the array is reset (i.e. emptied) first; if +A is
1841 used, the first N elements are set (where N is the number of
1842 arguments); the rest are left untouched.
1843 An alternative syntax for the command set -A foo -- a b c
1845 which is compatible to GNU bash and also supported by AT&T
1846 UNIX ksh93 is: foo=(a b c); foo+=(d e)
1847 Another AT&T UNIX ksh93 and GNU bash extension allows speci‐
1849 fying the indices used for arg ... (from the above example, a
1850 b c) like this: set -A foo -- [0]=a [1]=b [2]=c or foo=([0]=a
1851 [1]=b [2]=c) which can also be written foo=([0]=a b c)
1852 because indices are incremented automatically.
1853 -a | -o allexport
1855 All new parameters are created with the export attribute.
1856 -b | -o notify
1858 Print job notification messages asynchronously, instead of
1859 just before the prompt. Only used if job control is enabled
1860 (-m).
1861 -C | -o noclobber
1863 Prevent > redirection from overwriting existing files.
1864 Instead, >| must be used to force an overwrite.
1865 -e | -o errexit
1867 Exit (after executing the ERR trap) as soon as an error
1868 occurs or a command fails (i.e. exits with a non-zero sta‐
1869 tus). This does not apply to commands whose exit status is
1870 explicitly tested by a shell construct such as if, until,
1871 while, &&, ||, or ! statements.
1872 -f | -o noglob
1874 Do not expand file name patterns.
1875 -h | -o trackall
1877 Create tracked aliases for all executed commands (see Aliases
1878 above). Enabled by default for non-interactive shells.
1879 -i | -o interactive
1881 The shell is an interactive shell. This option can only be
1882 used when the shell is invoked. See above for a description
1883 of what this means.
1884 -k | -o keyword
1886 Parameter assignments are recognised anywhere in a command.
1887 -l | -o login
1889 The shell is a login shell. This option can only be used
1890 when the shell is invoked. See above for a description of
1891 what this means.
1892 -m | -o monitor
1894 Enable job control (default for interactive shells).
1895 -n | -o noexec
1897 Do not execute any commands. Useful for checking the syntax
1898 of scripts (ignored if interactive).
1899 -p | -o privileged
1901 The shell is a privileged shell. It is set automatically if,
1902 when the shell starts, the real UID or GID does not match the
1903 effective UID (EUID) or GID (EGID), respectively. See above
1904 for a description of what this means.
1905 -r | -o restricted
1907 The shell is a restricted shell. This option can only be
1908 used when the shell is invoked. See above for a description
1909 of what this means.
1910 -s | -o stdin
1912 If used when the shell is invoked, commands are read from
1913 standard input. Set automatically if the shell is invoked
1914 with no arguments.
1915 When -s is used with the set command it causes the specified
1917 arguments to be sorted before assigning them to the posi‐
1918 tional parameters (or to array name, if -A is used).
1919 -U | -o utf8-mode
1921 Enable UTF-8 support in the Emacs editing mode and internal
1922 string handling functions. This flag is disabled by default,
1923 but can be enabled by setting it on the shell command line;
1924 is enabled automatically for interactive shells if requested
1925 at compile time, your system supports setlocale(LC_CTYPE, "")
1926 and optionally nl_langinfo(CODESET), or the LC_ALL, LC_CTYPE,
1927 or LANG environment variables, and at least one of these
1928 returns something that matches “UTF-8” or “utf8” case-insen‐
1929 sitively; for direct builtin calls depending on the aforemen‐
1930 tioned environment variables; or for stdin or scripts, if the
1931 input begins with a UTF-8 Byte Order Mark.
1932 -u | -o nounset
1934 Referencing of an unset parameter, other than “$@” or “$*”,
1935 is treated as an error, unless one of the ‘-’, ‘+’, or ‘=’
1936 modifiers is used.
1937 -v | -o verbose
1939 Write shell input to standard error as it is read.
1940 -X | -o markdirs
1942 Mark directories with a trailing ‘/’ during file name genera‐
1943 tion.
1944 -x | -o xtrace
1946 Print commands and parameter assignments when they are exe‐
1947 cuted, preceded by the value of PS4.
1948 -o arc4random
1950 Deprecated, will be removed in mksh R41. Do not use, emits a
1951 warning to stderr.
1952 -o bgnice
1954 Background jobs are run with lower priority.
1955 -o braceexpand
1957 Enable brace expansion (a.k.a. alternation). This is enabled
1958 by default. If disabled, tilde expansion after an equals
1959 sign is disabled as a side effect.
1960 -o emacs
1962 Enable BRL emacs-like command-line editing (interactive
1963 shells only); see Emacs editing mode.
1964 -o gmacs
1966 Enable gmacs-like command-line editing (interactive shells
1967 only). Currently identical to emacs editing except that
1968 transpose-chars (^T) acts slightly differently.
1969 -o ignoreeof
1971 The shell will not (easily) exit when end-of-file is read;
1972 exit must be used. To avoid infinite loops, the shell will
1973 exit if EOF is read 13 times in a row.
1974 -o nohup
1976 Do not kill running jobs with a SIGHUP signal when a login
1977 shell exits. Currently set by default, but this may change
1978 in the future to be compatible with AT&T UNIX ksh, which
1979 doesn't have this option, but does send the SIGHUP signal.
1980 -o nolog
1982 No effect. In the original Korn shell, this prevents func‐
1983 tion definitions from being stored in the history file.
1984 -o physical
1986 Causes the cd and pwd commands to use “physical” (i.e. the
1987 filesystem's) ‘..’ directories instead of “logical” directo‐
1988 ries (i.e. the shell handles ‘..’, which allows the user to
1989 be oblivious of symbolic links to directories). Clear by
1990 default. Note that setting this option does not affect the
1991 current value of the PWD parameter; only the cd command
1992 changes PWD. See the cd and pwd commands above for more
1993 details.
1994 -o posix
1996 Enable a somewhat more POSIXish mode. As a side effect, set‐
1997 ting this flag turns off braceexpand mode, which can be
1998 turned back on manually, and sh mode.
1999 -o sh
2001 Enable /bin/sh (kludge) mode. Automatically enabled if the
2002 basename of the shell invocation begins with “sh” and this
2003 autodetection feature is compiled in (not in MirBSD). As a
2004 side effect, setting this flag turns off braceexpand mode,
2005 which can be turned back on manually, and posix mode.
2006 -o vi
2008 Enable vi(1)-like command-line editing (interactive shells
2009 only).
2010 -o vi-esccomplete
2012 In vi command-line editing, do command and file name comple‐
2013 tion when escape (^[) is entered in command mode.
2014 -o vi-tabcomplete
2016 In vi command-line editing, do command and file name comple‐
2017 tion when tab (^I) is entered in insert mode. This is the
2018 default.
2019 -o viraw
2021 No effect. In the original Korn shell, unless viraw was set,
2022 the vi command-line mode would let the tty(4) driver do the
2023 work until ESC (^[) was entered. mksh is always in viraw
2024 mode.
2025 These options can also be used upon invocation of the shell. The
2027 current set of options (with single letter names) can be found in
2028 the parameter ‘$-’. set -o with no option name will list all the
2029 options and whether each is on or off; set +o will print the long
2030 names of all options that are currently on.
2031 Remaining arguments, if any, are positional parameters and are
2033 assigned, in order, to the positional parameters (i.e. $1, $2,
2034 etc.). If options end with ‘--’ and there are no remaining argu‐
2035 ments, all positional parameters are cleared. If no options or
2036 arguments are given, the values of all names are printed. For
2037 unknown historical reasons, a lone ‘-’ option is treated specially
2038 – it clears both the -v and -x options.
2039 shift [number]
2041 The positional parameters number+1, number+2, etc. are renamed to
2042 ‘1’, ‘2’, etc. number defaults to 1.
2043 sleep seconds
2045 Suspends execution for a minimum of the seconds specified as posi‐
2046 tive decimal value with an optional fractional part. Signal
2047 delivery may continue execution earlier.
2048 source file [arg ...]
2050 Like . (“dot”), except that the current working directory is
2051 appended to the PATH in GNU bash and mksh. In ksh93 and mksh,
2052 this is implemented as a shell alias instead of a builtin.
2053 test expression
2055 [ expression ]
2056 test evaluates the expression and returns zero status if true, 1
2057 if false, or greater than 1 if there was an error. It is normally
2058 used as the condition command of if and while statements. Sym‐
2059 bolic links are followed for all file expressions except -h and
2060 -L.
2061 The following basic expressions are available:
2063 -a file file exists.
2065 -b file file is a block special device.
2067 -c file file is a character special device.
2069 -d file file is a directory.
2071 -e file file exists.
2073 -f file file is a regular file.
2075 -G file file's group is the shell's effective group ID.
2077 -g file file's mode has the setgid bit set.
2079 -H file file is a context dependent directory (only
2081 useful on HP-UX).
2082 -h file file is a symbolic link.
2084 -k file file's mode has the sticky(8) bit set.
2086 -L file file is a symbolic link.
2088 -O file file's owner is the shell's effective user ID.
2090 -o option Shell option is set (see the set command above
2092 for a list of options). As a non-standard
2093 extension, if the option starts with a ‘!’, the
2094 test is negated; the test always fails if
2095 option doesn't exist (so [ -o foo -o -o !foo ]
2096 returns true if and only if option foo exists).
2097 The same can be achieved with [ -o ?foo ] like
2098 in AT&T UNIX ksh93. option can also be the
2099 short flag led by either ‘-’ or ‘+’ (no logical
2100 negation), for example ‘-x’ or ‘+x’ instead of
2101 ‘xtrace’.
2102 -p file file is a named pipe.
2104 -r file file exists and is readable.
2106 -S file file is a unix(4)-domain socket.
2108 -s file file is not empty.
2110 -t fd File descriptor fd is a tty(4) device.
2112 -u file file's mode has the setuid bit set.
2114 -w file file exists and is writable.
2116 -x file file exists and is executable.
2118 file1 -nt file2 file1 is newer than file2 or file1 exists and
2120 file2 does not.
2121 file1 -ot file2 file1 is older than file2 or file2 exists and
2123 file1 does not.
2124 file1 -ef file2 file1 is the same file as file2.
2126 string string has non-zero length.
2128 -n string string is not empty.
2130 -z string string is empty.
2132 string = string Strings are equal.
2134 string == string Strings are equal.
2136 string > string First string operand is greater than second
2138 string operand.
2139 string < string First string operand is less than second string
2141 operand.
2142 string != string Strings are not equal.
2144 number -eq number Numbers compare equal.
2146 number -ne number Numbers compare not equal.
2148 number -ge number Numbers compare greater than or equal.
2150 number -gt number Numbers compare greater than.
2152 number -le number Numbers compare less than or equal.
2154 number -lt number Numbers compare less than.
2156 The above basic expressions, in which unary operators have prece‐
2158 dence over binary operators, may be combined with the following
2159 operators (listed in increasing order of precedence):
2160 expr -o expr Logical OR.
2162 expr -a expr Logical AND.
2163 ! expr Logical NOT.
2164 ( expr ) Grouping.
2165 Note that a number actually may be an arithmetic expression, such
2167 as a mathematical term or the name of an integer variable:
2168 x=1; [ "x" -eq 1 ] evaluates to true
2170 Note that some special rules are applied (courtesy of POSIX) if
2172 the number of arguments to test or [ ... ] is less than five: if
2173 leading ‘!’ arguments can be stripped such that only one argument
2174 remains then a string length test is performed (again, even if the
2175 argument is a unary operator); if leading ‘!’ arguments can be
2176 stripped such that three arguments remain and the second argument
2177 is a binary operator, then the binary operation is performed (even
2178 if the first argument is a unary operator, including an unstripped
2179 ‘!’).
2180 Note: A common mistake is to use “if [ $foo = bar ]” which fails
2182 if parameter “foo” is NULL or unset, if it has embedded spaces
2183 (i.e. IFS octets), or if it is a unary operator like ‘!’ or ‘-n’.
2184 Use tests like “if [ x"$foo" = x"bar" ]” instead, or the double-
2185 bracket operator “if [[ $foo = bar ]]” or, to avoid pattern match‐
2186 ing (see [[ above): “if [[ $foo = "$bar" ]]”
2187 time [-p] [pipeline]
2189 If a pipeline is given, the times used to execute the pipeline are
2190 reported. If no pipeline is given, then the user and system time
2191 used by the shell itself, and all the commands it has run since it
2192 was started, are reported. The times reported are the real time
2193 (elapsed time from start to finish), the user CPU time (time spent
2194 running in user mode), and the system CPU time (time spent running
2195 in kernel mode). Times are reported to standard error; the format
2196 of the output is:
2197 0m0.00s real 0m0.00s user 0m0.00s system
2199 If the -p option is given the output is slightly longer:
2201 real 0.00
2203 user 0.00
2204 sys 0.00
2205 It is an error to specify the -p option unless pipeline is a sim‐
2207 ple command.
2208 Simple redirections of standard error do not affect the output of
2210 the time command:
2211 $ time sleep 1 2>afile
2213 $ { time sleep 1; } 2>afile
2214 Times for the first command do not go to “afile”, but those of the
2216 second command do.
2217 times Print the accumulated user and system times used both by the shell
2219 and by processes that the shell started which have exited. The
2220 format of the output is:
2221 0m0.00s 0m0.00s
2223 0m0.00s 0m0.00s
2224 trap [handler signal ...]
2226 Sets a trap handler that is to be executed when any of the speci‐
2227 fied signals are received. handler is either a NULL string, indi‐
2228 cating the signals are to be ignored, a minus sign (‘-’), indicat‐
2229 ing that the default action is to be taken for the signals (see
2230 signal(3)), or a string containing shell commands to be evaluated
2231 and executed at the first opportunity (i.e. when the current com‐
2232 mand completes, or before printing the next PS1 prompt) after
2233 receipt of one of the signals. signal is the name of a signal
2234 (e.g. PIPE or ALRM) or the number of the signal (see the kill -l
2235 command above).
2236 There are two special signals: EXIT (also known as 0) which is
2238 executed when the shell is about to exit, and ERR, which is exe‐
2239 cuted after an error occurs (an error is something that would
2240 cause the shell to exit if the -e or errexit option were set – see
2241 the set command above). EXIT handlers are executed in the envi‐
2242 ronment of the last executed command. Note that for non-interac‐
2243 tive shells, the trap handler cannot be changed for signals that
2244 were ignored when the shell started.
2245 With no arguments, trap lists, as a series of trap commands, the
2247 current state of the traps that have been set since the shell
2248 started. Note that the output of trap cannot be usefully piped to
2249 another process (an artifact of the fact that traps are cleared
2250 when subprocesses are created).
2251 The original Korn shell's DEBUG trap and the handling of ERR and
2253 EXIT traps in functions are not yet implemented.
2254 true A command that exits with a zero value.
2256 global [[+-alpnrtUux] [-L[n]] [-R[n]] [-Z[n]] [-i[n]] | -f [-tux]] [name
2258 [=value] ...]
2259 typeset [[+-alpnrtUux] [-LRZ[n]] [-i[n]] | -f [-tux]] [name [=value] ...]
2260 Display or set parameter attributes. With no name arguments,
2261 parameter attributes are displayed; if no options are used, the
2262 current attributes of all parameters are printed as typeset com‐
2263 mands; if an option is given (or ‘-’ with no option letter), all
2264 parameters and their values with the specified attributes are
2265 printed; if options are introduced with ‘+’, parameter values are
2266 not printed.
2267 If name arguments are given, the attributes of the named parame‐
2269 ters are set (-) or cleared (+). Values for parameters may
2270 optionally be specified. For name[*], the change affects the
2271 entire array, and no value may be specified.
2272 If typeset is used inside a function, any parameters specified are
2274 localised. This is not done by the otherwise identical global.
2275 When -f is used, typeset operates on the attributes of functions.
2277 As with parameters, if no name arguments are given, functions are
2278 listed with their values (i.e. definitions) unless options are
2279 introduced with ‘+’, in which case only the function names are
2280 reported.
2281 -a Indexed array attribute.
2283 -f Function mode. Display or set functions and their
2285 attributes, instead of parameters.
2286 -i[n] Integer attribute. n specifies the base to use when dis‐
2288 playing the integer (if not specified, the base given in
2289 the first assignment is used). Parameters with this
2290 attribute may be assigned values containing arithmetic
2291 expressions.
2292 -L[n] Left justify attribute. n specifies the field width. If
2294 n is not specified, the current width of a parameter (or
2295 the width of its first assigned value) is used. Leading
2296 whitespace (and zeros, if used with the -Z option) is
2297 stripped. If necessary, values are either truncated or
2298 space padded to fit the field width.
2299 -l Lower case attribute. All upper case characters in values
2301 are converted to lower case. (In the original Korn shell,
2302 this parameter meant “long integer” when used with the -i
2303 option.)
2304 -n Create a bound variable (name reference): any access to
2306 the variable name will access the variable value in the
2307 current scope (this is different from AT&T UNIX ksh93!)
2308 instead. Also different from AT&T UNIX ksh93 is that
2309 value is lazily evaluated at the time name is accessed.
2310 This can be used by functions to access variables whose
2311 names are passed as parametres, instead of using eval.
2312 -p Print complete typeset commands that can be used to re-
2314 create the attributes and values of parameters.
2315 -R[n] Right justify attribute. n specifies the field width. If
2317 n is not specified, the current width of a parameter (or
2318 the width of its first assigned value) is used. Trailing
2319 whitespace is stripped. If necessary, values are either
2320 stripped of leading characters or space padded to make
2321 them fit the field width.
2322 -r Read-only attribute. Parameters with this attribute may
2324 not be assigned to or unset. Once this attribute is set,
2325 it cannot be turned off.
2326 -t Tag attribute. Has no meaning to the shell; provided for
2328 application use.
2329 For functions, -t is the trace attribute. When functions
2331 with the trace attribute are executed, the xtrace (-x)
2332 shell option is temporarily turned on.
2333 -U Unsigned integer attribute. Integers are printed as
2335 unsigned values (combine with the -i option). This option
2336 is not in the original Korn shell.
2337 -u Upper case attribute. All lower case characters in values
2339 are converted to upper case. (In the original Korn shell,
2340 this parameter meant “unsigned integer” when used with the
2341 -i option which meant upper case letters would never be
2342 used for bases greater than 10. See the -U option.)
2343 For functions, -u is the undefined attribute. See
2345 Functions above for the implications of this.
2346 -x Export attribute. Parameters (or functions) are placed in
2348 the environment of any executed commands. Exported func‐
2349 tions are not yet implemented.
2350 -Z[n] Zero fill attribute. If not combined with -L, this is the
2352 same as -R, except zero padding is used instead of space
2353 padding. For integers, the number instead of the base is
2354 padded.
2355 If any of the -i, -L, -l, -R, -U, -u, or -Z options are changed,
2357 all others from this set are cleared, unless they are also given
2358 on the same command line.
2359 ulimit [-aBCcdefHiLlMmnOPpqrSsTtVvw] [value]
2361 Display or set process limits. If no options are used, the file
2362 size limit (-f) is assumed. value, if specified, may be either an
2363 arithmetic expression or the word “unlimited”. The limits affect
2364 the shell and any processes created by the shell after a limit is
2365 imposed. Note that some systems may not allow limits to be
2366 increased once they are set. Also note that the types of limits
2367 available are system dependent – some systems have only the -f
2368 limit.
2369 -a Display all limits; unless -H is used, soft limits are dis‐
2371 played.
2372 -B n Set the socket buffer size to n kibibytes.
2374 -C n Set the number of cached threads to n.
2376 -c n Impose a size limit of n blocks on the size of core dumps.
2378 -d n Impose a size limit of n kibibytes on the size of the data
2380 area.
2381 -e n Set the maximum niceness to n.
2383 -f n Impose a size limit of n blocks on files written by the
2385 shell and its child processes (files of any size may be
2386 read).
2387 -H Set the hard limit only (the default is to set both hard
2389 and soft limits).
2390 -i n Set the number of pending signals to n.
2392 -L n Control flocks; documentation is missing.
2394 -l n Impose a limit of n kibibytes on the amount of locked
2396 (wired) physical memory.
2397 -M n Set the AIO locked memory to n kibibytes.
2399 -m n Impose a limit of n kibibytes on the amount of physical
2401 memory used.
2402 -n n Impose a limit of n file descriptors that can be open at
2404 once.
2405 -O n Set the number of AIO operations to n.
2407 -P n Limit the number of threads per process to n.
2409 -p n Impose a limit of n processes that can be run by the user
2411 at any one time.
2412 -q n Limit the size of POSIX message queues to n bytes.
2414 -r n Set the maximum real-time priority to n.
2416 -S Set the soft limit only (the default is to set both hard
2418 and soft limits).
2419 -s n Impose a size limit of n kibibytes on the size of the stack
2421 area.
2422 -T n Impose a time limit of n real seconds to be used by each
2424 process.
2425 -t n Impose a time limit of n CPU seconds spent in user mode to
2427 be used by each process.
2428 -V n Set the number of vnode monitors on Haiku to n.
2430 -v n Impose a limit of n kibibytes on the amount of virtual mem‐
2432 ory (address space) used.
2433 -w n Impose a limit of n kibibytes on the amount of swap space
2435 used.
2436 As far as ulimit is concerned, a block is 512 bytes.
2438 umask [-S] [mask]
2440 Display or set the file permission creation mask, or umask (see
2441 umask(2)). If the -S option is used, the mask displayed or set is
2442 symbolic; otherwise, it is an octal number.
2443 Symbolic masks are like those used by chmod(1). When used, they
2445 describe what permissions may be made available (as opposed to
2446 octal masks in which a set bit means the corresponding bit is to
2447 be cleared). For example, “ug=rwx,o=” sets the mask so files will
2448 not be readable, writable, or executable by “others”, and is
2449 equivalent (on most systems) to the octal mask “007”.
2450 unalias [-adt] [name ...]
2452 The aliases for the given names are removed. If the -a option is
2453 used, all aliases are removed. If the -t or -d options are used,
2454 the indicated operations are carried out on tracked or directory
2455 aliases, respectively.
2456 unset [-fv] parameter ...
2458 Unset the named parameters (-v, the default) or functions (-f).
2459 With parameter[*], attributes are kept, only values are unset.
2460 The exit status is non-zero if any of the parameters have the
2462 read-only attribute set, zero otherwise.
2463 wait [job ...]
2465 Wait for the specified job(s) to finish. The exit status of wait
2466 is that of the last specified job; if the last job is killed by a
2467 signal, the exit status is 128 + the number of the signal (see
2468 kill -l exit-status above); if the last specified job can't be
2469 found (because it never existed, or had already finished), the
2470 exit status of wait is 127. See Job control below for the format
2471 of job. wait will return if a signal for which a trap has been
2472 set is received, or if a SIGHUP, SIGINT, or SIGQUIT signal is
2473 received.
2474 If no jobs are specified, wait waits for all currently running
2476 jobs (if any) to finish and exits with a zero status. If job mon‐
2477 itoring is enabled, the completion status of jobs is printed (this
2478 is not the case when jobs are explicitly specified).
2479 whence [-pv] [name ...]
2481 For each name, the type of command is listed (reserved word,
2482 built-in, alias, function, tracked alias, or executable). If the
2483 -p option is used, a path search is performed even if name is a
2484 reserved word, alias, etc. Without the -v option, whence is simi‐
2485 lar to command -v except that whence will find reserved words and
2486 won't print aliases as alias commands. With the -v option, whence
2487 is the same as command -V. Note that for whence, the -p option
2488 does not affect the search path used, as it does for command. If
2489 the type of one or more of the names could not be determined, the
2490 exit status is non-zero.
2491 Job control
2493 Job control refers to the shell's ability to monitor and control jobs
2494 which are processes or groups of processes created for commands or pipe‐
2495 lines. At a minimum, the shell keeps track of the status of the back‐
2496 ground (i.e. asynchronous) jobs that currently exist; this information
2497 can be displayed using the jobs commands. If job control is fully
2498 enabled (using set -m or set -o monitor), as it is for interactive
2499 shells, the processes of a job are placed in their own process group.
2500 Foreground jobs can be stopped by typing the suspend character from the
2501 terminal (normally ^Z), jobs can be restarted in either the foreground or
2502 background using the fg and bg commands, and the state of the terminal is
2503 saved or restored when a foreground job is stopped or restarted, respec‐
2504 tively.
2505 Note that only commands that create processes (e.g. asynchronous com‐
2507 mands, subshell commands, and non-built-in, non-function commands) can be
2508 stopped; commands like read cannot be.
2509 When a job is created, it is assigned a job number. For interactive
2511 shells, this number is printed inside “[..]”, followed by the process IDs
2512 of the processes in the job when an asynchronous command is run. A job
2513 may be referred to in the bg, fg, jobs, kill, and wait commands either by
2514 the process ID of the last process in the command pipeline (as stored in
2515 the $! parameter) or by prefixing the job number with a percent sign
2516 (‘%’). Other percent sequences can also be used to refer to jobs:
2517 %+ | %% | % The most recently stopped job, or, if there are no stopped
2519 jobs, the oldest running job.
2520 %- The job that would be the %+ job if the latter did not
2522 exist.
2523 %n The job with job number n.
2525 %?string The job with its command containing the string string (an
2527 error occurs if multiple jobs are matched).
2528 %string The job with its command starting with the string string
2530 (an error occurs if multiple jobs are matched).
2531 When a job changes state (e.g. a background job finishes or foreground
2533 job is stopped), the shell prints the following status information:
2534 [number] flag status command
2536 where...
2538 number is the job number of the job;
2540 flag is the ‘+’ or ‘-’ character if the job is the %+ or %- job,
2542 respectively, or space if it is neither;
2543 status indicates the current state of the job and can be:
2545 Done [number]
2547 The job exited. number is the exit status of the job
2548 which is omitted if the status is zero.
2549 Running The job has neither stopped nor exited (note that
2551 running does not necessarily mean consuming CPU time
2552 – the process could be blocked waiting for some
2553 event).
2554 Stopped [signal]
2556 The job was stopped by the indicated signal (if no
2557 signal is given, the job was stopped by SIGTSTP).
2558 signal-description [“core dumped”]
2560 The job was killed by a signal (e.g. memory fault,
2561 hangup); use kill -l for a list of signal descrip‐
2562 tions. The “core dumped” message indicates the
2563 process created a core file.
2564 command is the command that created the process. If there are multiple
2566 processes in the job, each process will have a line showing its
2567 command and possibly its status, if it is different from the
2568 status of the previous process.
2569 When an attempt is made to exit the shell while there are jobs in the
2571 stopped state, the shell warns the user that there are stopped jobs and
2572 does not exit. If another attempt is immediately made to exit the shell,
2573 the stopped jobs are sent a SIGHUP signal and the shell exits. Simi‐
2574 larly, if the nohup option is not set and there are running jobs when an
2575 attempt is made to exit a login shell, the shell warns the user and does
2576 not exit. If another attempt is immediately made to exit the shell, the
2577 running jobs are sent a SIGHUP signal and the shell exits.
2578 Interactive input line editing
2580 The shell supports three modes of reading command lines from a tty(4) in
2581 an interactive session, controlled by the emacs, gmacs, and vi options
2582 (at most one of these can be set at once). The default is emacs. Edit‐
2583 ing modes can be set explicitly using the set built-in. If none of these
2584 options are enabled, the shell simply reads lines using the normal tty(4)
2585 driver. If the emacs or gmacs option is set, the shell allows emacs-like
2586 editing of the command; similarly, if the vi option is set, the shell
2587 allows vi-like editing of the command. These modes are described in
2588 detail in the following sections.
2589 In these editing modes, if a line is longer than the screen width (see
2591 the COLUMNS parameter), a ‘>’, ‘+’, or ‘<’ character is displayed in the
2592 last column indicating that there are more characters after, before and
2593 after, or before the current position, respectively. The line is
2594 scrolled horizontally as necessary.
2595 Completed lines are pushed into the history, unless they begin with an
2597 IFS octet or IFS white space, or are the same as the previous line.
2598 Emacs editing mode
2600 When the emacs option is set, interactive input line editing is enabled.
2601 Warning: This mode is slightly different from the emacs mode in the orig‐
2602 inal Korn shell. In this mode, various editing commands (typically bound
2603 to one or more control characters) cause immediate actions without wait‐
2604 ing for a newline. Several editing commands are bound to particular con‐
2605 trol characters when the shell is invoked; these bindings can be changed
2606 using the bind command.
2607 The following is a list of available editing commands. Each description
2609 starts with the name of the command, suffixed with a colon; an [n] (if
2610 the command can be prefixed with a count); and any keys the command is
2611 bound to by default, written using caret notation e.g. the ASCII ESC
2612 character is written as ^[. These control sequences are not case sensi‐
2613 tive. A count prefix for a command is entered using the sequence ^[n,
2614 where n is a sequence of 1 or more digits. Unless otherwise specified,
2615 if a count is omitted, it defaults to 1.
2616 Note that editing command names are used only with the bind command.
2618 Furthermore, many editing commands are useful only on terminals with a
2619 visible cursor. The default bindings were chosen to resemble correspond‐
2620 ing Emacs key bindings. The user's tty(4) characters (e.g. ERASE) are
2621 bound to reasonable substitutes and override the default bindings.
2622 abort: ^C, ^G
2624 Abort the current command, empty the line buffer and set the exit
2625 state to interrupted.
2626 auto-insert: [n]
2628 Simply causes the character to appear as literal input. Most
2629 ordinary characters are bound to this.
2630 backward-char: [n] ^B, ^XD, ANSI-CurLeft
2632 Moves the cursor backward n characters.
2633 backward-word: [n] ^[b, ANSI-Ctrl-CurLeft, ANSI-Alt-CurLeft
2635 Moves the cursor backward to the beginning of the word; words
2636 consist of alphanumerics, underscore (‘_’), and dollar sign (‘$’)
2637 characters.
2638 beginning-of-history: ^[<
2640 Moves to the beginning of the history.
2641 beginning-of-line: ^A, ANSI-Home
2643 Moves the cursor to the beginning of the edited input line.
2644 capitalise-word: [n] ^[C, ^[c
2646 Uppercase the first character in the next n words, leaving the
2647 cursor past the end of the last word.
2648 clear-screen: ^[^L
2650 Prints a compile-time configurable sequence to clear the screen
2651 and home the cursor, redraws the entire prompt and the currently
2652 edited input line. The default sequence works for almost all
2653 standard terminals.
2654 comment: ^[#
2656 If the current line does not begin with a comment character, one
2657 is added at the beginning of the line and the line is entered (as
2658 if return had been pressed); otherwise, the existing comment
2659 characters are removed and the cursor is placed at the beginning
2660 of the line.
2661 complete: ^[^[
2663 Automatically completes as much as is unique of the command name
2664 or the file name containing the cursor. If the entire remaining
2665 command or file name is unique, a space is printed after its com‐
2666 pletion, unless it is a directory name in which case ‘/’ is
2667 appended. If there is no command or file name with the current
2668 partial word as its prefix, a bell character is output (usually
2669 causing a beep to be sounded).
2670 complete-command: ^X^[
2672 Automatically completes as much as is unique of the command name
2673 having the partial word up to the cursor as its prefix, as in the
2674 complete command above.
2675 complete-file: ^[^X
2677 Automatically completes as much as is unique of the file name
2678 having the partial word up to the cursor as its prefix, as in the
2679 complete command described above.
2680 complete-list: ^I, ^[=
2682 Complete as much as is possible of the current word, and list the
2683 possible completions for it. If only one completion is possible,
2684 match as in the complete command above. Note that ^I is usually
2685 generated by the TAB (tabulator) key.
2686 delete-char-backward: [n] ERASE, ^?, ^H
2688 Deletes n characters before the cursor.
2689 delete-char-forward: [n] ANSI-Del
2691 Deletes n characters after the cursor.
2692 delete-word-backward: [n] WERASE, ^[^?, ^[^H, ^[h
2694 Deletes n words before the cursor.
2695 delete-word-forward: [n] ^[d
2697 Deletes characters after the cursor up to the end of n words.
2698 down-history: [n] ^N, ^XB, ANSI-CurDown
2700 Scrolls the history buffer forward n lines (later). Each input
2701 line originally starts just after the last entry in the history
2702 buffer, so down-history is not useful until either
2703 search-history, search-history-up or up-history has been per‐
2704 formed.
2705 downcase-word: [n] ^[L, ^[l
2707 Lowercases the next n words.
2708 edit-line: [n] ^Xe
2710 Edit line n or the current line, if not specified, interactively.
2711 The actual command executed is fc -e ${VISUAL:-${EDITOR:-vi}} n.
2712 end-of-history: ^[>
2714 Moves to the end of the history.
2715 end-of-line: ^E, ANSI-End
2717 Moves the cursor to the end of the input line.
2718 eot: ^_
2720 Acts as an end-of-file; this is useful because edit-mode input
2721 disables normal terminal input canonicalization.
2722 eot-or-delete: [n] ^D
2724 Acts as eot if alone on a line; otherwise acts as
2725 delete-char-forward.
2726 error: (not bound)
2728 Error (ring the bell).
2729 exchange-point-and-mark: ^X^X
2731 Places the cursor where the mark is and sets the mark to where
2732 the cursor was.
2733 expand-file: ^[*
2735 Appends a ‘*’ to the current word and replaces the word with the
2736 result of performing file globbing on the word. If no files
2737 match the pattern, the bell is rung.
2738 forward-char: [n] ^F, ^XC, ANSI-CurRight
2740 Moves the cursor forward n characters.
2741 forward-word: [n] ^[f, ANSI-Ctrl-CurRight, ANSI-Alt-CurRight
2743 Moves the cursor forward to the end of the nth word.
2744 goto-history: [n] ^[g
2746 Goes to history number n.
2747 kill-line: KILL
2749 Deletes the entire input line.
2750 kill-region: ^W
2752 Deletes the input between the cursor and the mark.
2753 kill-to-eol: [n] ^K
2755 Deletes the input from the cursor to the end of the line if n is
2756 not specified; otherwise deletes characters between the cursor
2757 and column n.
2758 list: ^[?
2760 Prints a sorted, columnated list of command names or file names
2761 (if any) that can complete the partial word containing the cur‐
2762 sor. Directory names have ‘/’ appended to them.
2763 list-command: ^X?
2765 Prints a sorted, columnated list of command names (if any) that
2766 can complete the partial word containing the cursor.
2767 list-file: ^X^Y
2769 Prints a sorted, columnated list of file names (if any) that can
2770 complete the partial word containing the cursor. File type indi‐
2771 cators are appended as described under list above.
2772 newline: ^J, ^M
2774 Causes the current input line to be processed by the shell. The
2775 current cursor position may be anywhere on the line.
2776 newline-and-next: ^O
2778 Causes the current input line to be processed by the shell, and
2779 the next line from history becomes the current line. This is
2780 only useful after an up-history, search-history or
2781 search-history-up.
2782 no-op: QUIT
2784 This does nothing.
2785 prefix-1: ^[
2787 Introduces a 2-character command sequence.
2788 prefix-2: ^X, ^[[, ^[O
2790 Introduces a 2-character command sequence.
2791 prev-hist-word: [n] ^[., ^[_
2793 The last word, or, if given, the nth word (zero-based) of the
2794 previous (on repeated execution, second-last, third-last, etc.)
2795 command is inserted at the cursor. Use of this editing command
2796 trashes the mark.
2797 quote: ^^, ^V
2799 The following character is taken literally rather than as an
2800 editing command.
2801 redraw: ^L
2803 Reprints the last line of the prompt string and the current input
2804 line on a new line.
2805 search-character-backward: [n] ^[^]
2807 Search backward in the current line for the nth occurrence of the
2808 next character typed.
2809 search-character-forward: [n] ^]
2811 Search forward in the current line for the nth occurrence of the
2812 next character typed.
2813 search-history: ^R
2815 Enter incremental search mode. The internal history list is
2816 searched backwards for commands matching the input. An initial
2817 ‘^’ in the search string anchors the search. The escape key will
2818 leave search mode. Other commands, including sequences of escape
2819 as prefix-1 followed by a prefix-1 or prefix-2 key will be exe‐
2820 cuted after leaving search mode. The abort (^G) command will
2821 restore the input line before search started. Successive
2822 search-history commands continue searching backward to the next
2823 previous occurrence of the pattern. The history buffer retains
2824 only a finite number of lines; the oldest are discarded as neces‐
2825 sary.
2826 search-history-up: ANSI-PgUp
2828 Search backwards through the history buffer for commands whose
2829 beginning match the portion of the input line before the cursor.
2830 When used on an empty line, this has the same effect as
2831 up-history.
2832 search-history-down: ANSI-PgDn
2834 Search forwards through the history buffer for commands whose
2835 beginning match the portion of the input line before the cursor.
2836 When used on an empty line, this has the same effect as
2837 down-history. This is only useful after an up-history,
2838 search-history or search-history-up.
2839 set-mark-command: ^[⟨space⟩
2841 Set the mark at the cursor position.
2842 transpose-chars: ^T
2844 If at the end of line, or if the gmacs option is set, this
2845 exchanges the two previous characters; otherwise, it exchanges
2846 the previous and current characters and moves the cursor one
2847 character to the right.
2848 up-history: [n] ^P, ^XA, ANSI-CurUp
2850 Scrolls the history buffer backward n lines (earlier).
2851 upcase-word: [n] ^[U, ^[u
2853 Uppercase the next n words.
2854 version: ^[^V
2856 Display the version of mksh. The current edit buffer is restored
2857 as soon as a key is pressed. The restoring keypress is pro‐
2858 cessed, unless it is a space.
2859 yank: ^Y
2861 Inserts the most recently killed text string at the current cur‐
2862 sor position.
2863 yank-pop: ^[y
2865 Immediately after a yank, replaces the inserted text string with
2866 the next previously killed text string.
2867 Vi editing mode
2869 Note: The vi command-line editing mode is orphaned, yet still functional.
2870 The vi command-line editor in mksh has basically the same commands as the
2872 vi(1) editor with the following exceptions:
2873 · You start out in insert mode.
2875 · There are file name and command completion commands: =, \, *, ^X, ^E,
2877 ^F, and, optionally, ⟨tab⟩ and ⟨esc⟩.
2878 · The _ command is different (in mksh, it is the last argument command;
2880 in vi(1) it goes to the start of the current line).
2881 · The / and G commands move in the opposite direction to the j command.
2883 · Commands which don't make sense in a single line editor are not
2885 available (e.g. screen movement commands and ex(1)-style colon (:)
2886 commands).
2887 Like vi(1), there are two modes: “insert” mode and “command” mode. In
2889 insert mode, most characters are simply put in the buffer at the current
2890 cursor position as they are typed; however, some characters are treated
2891 specially. In particular, the following characters are taken from cur‐
2892 rent tty(4) settings (see stty(1)) and have their usual meaning (normal
2893 values are in parentheses): kill (^U), erase (^?), werase (^W), eof (^D),
2894 intr (^C), and quit (^\). In addition to the above, the following char‐
2895 acters are also treated specially in insert mode:
2896 ^E Command and file name enumeration (see below).
2898 ^F Command and file name completion (see below). If used twice in
2900 a row, the list of possible completions is displayed; if used a
2901 third time, the completion is undone.
2902 ^H Erases previous character.
2904 ^J | ^M End of line. The current line is read, parsed, and executed by
2906 the shell.
2907 ^V Literal next. The next character typed is not treated specially
2909 (can be used to insert the characters being described here).
2910 ^X Command and file name expansion (see below).
2912 ⟨esc⟩ Puts the editor in command mode (see below).
2914 ⟨tab⟩ Optional file name and command completion (see ^F above),
2916 enabled with set -o vi-tabcomplete.
2917 In command mode, each character is interpreted as a command. Characters
2919 that don't correspond to commands, are illegal combinations of commands,
2920 or are commands that can't be carried out, all cause beeps. In the fol‐
2921 lowing command descriptions, an [n] indicates the command may be prefixed
2922 by a number (e.g. 10l moves right 10 characters); if no number prefix is
2923 used, n is assumed to be 1 unless otherwise specified. The term “current
2924 position” refers to the position between the cursor and the character
2925 preceding the cursor. A “word” is a sequence of letters, digits, and
2926 underscore characters or a sequence of non-letter, non-digit, non-under‐
2927 score, and non-whitespace characters (e.g. “ab2*&^” contains two words)
2928 and a “big-word” is a sequence of non-whitespace characters.
2929 Special mksh vi commands:
2931 The following commands are not in, or are different from, the normal vi
2933 file editor:
2934 [n]_ Insert a space followed by the nth big-word from the last
2936 command in the history at the current position and enter
2937 insert mode; if n is not specified, the last word is
2938 inserted.
2939 # Insert the comment character (‘#’) at the start of the cur‐
2941 rent line and return the line to the shell (equivalent to
2942 I#^J).
2943 [n]g Like G, except if n is not specified, it goes to the most
2945 recent remembered line.
2946 [n]v Edit line n using the vi(1) editor; if n is not specified,
2948 the current line is edited. The actual command executed is
2949 fc -e ${VISUAL:-${EDITOR:-vi}} n.
2950 * and ^X Command or file name expansion is applied to the current big-
2952 word (with an appended ‘*’ if the word contains no file glob‐
2953 bing characters) – the big-word is replaced with the result‐
2954 ing words. If the current big-word is the first on the line
2955 or follows one of the characters ‘;’, ‘|’, ‘&’, ‘(’, or ‘)’,
2956 and does not contain a slash (‘/’), then command expansion is
2957 done; otherwise file name expansion is done. Command expan‐
2958 sion will match the big-word against all aliases, functions,
2959 and built-in commands as well as any executable files found
2960 by searching the directories in the PATH parameter. File
2961 name expansion matches the big-word against the files in the
2962 current directory. After expansion, the cursor is placed
2963 just past the last word and the editor is in insert mode.
2964 [n]\, [n]^F, [n]⟨tab⟩, and [n]⟨esc⟩
2966 Command/file name completion. Replace the current big-word
2967 with the longest unique match obtained after performing com‐
2968 mand and file name expansion. ⟨tab⟩ is only recognised if
2969 the vi-tabcomplete option is set, while ⟨esc⟩ is only recog‐
2970 nised if the vi-esccomplete option is set (see set -o). If n
2971 is specified, the nth possible completion is selected (as
2972 reported by the command/file name enumeration command).
2973 = and ^E Command/file name enumeration. List all the commands or
2975 files that match the current big-word.
2976 ^V Display the version of mksh. The current edit buffer is
2978 restored as soon as a key is pressed. The restoring keypress
2979 is ignored.
2980 @c Macro expansion. Execute the commands found in the alias c.
2982 Intra-line movement commands:
2984 [n]h and [n]^H
2986 Move left n characters.
2987 [n]l and [n]⟨space⟩
2989 Move right n characters.
2990 0 Move to column 0.
2992 ^ Move to the first non-whitespace character.
2994 [n]| Move to column n.
2996 $ Move to the last character.
2998 [n]b Move back n words.
3000 [n]B Move back n big-words.
3002 [n]e Move forward to the end of the word, n times.
3004 [n]E Move forward to the end of the big-word, n times.
3006 [n]w Move forward n words.
3008 [n]W Move forward n big-words.
3010 % Find match. The editor looks forward for the nearest parenthe‐
3012 sis, bracket, or brace and then moves the cursor to the matching
3013 parenthesis, bracket, or brace.
3014 [n]fc Move forward to the nth occurrence of the character c.
3016 [n]Fc Move backward to the nth occurrence of the character c.
3018 [n]tc Move forward to just before the nth occurrence of the character
3020 c.
3021 [n]Tc Move backward to just before the nth occurrence of the character
3023 c.
3024 [n]; Repeats the last f, F, t, or T command.
3026 [n], Repeats the last f, F, t, or T command, but moves in the opposite
3028 direction.
3029 Inter-line movement commands:
3031 [n]j, [n]+, and [n]^N
3033 Move to the nth next line in the history.
3034 [n]k, [n]-, and [n]^P
3036 Move to the nth previous line in the history.
3037 [n]G Move to line n in the history; if n is not specified, the number
3039 of the first remembered line is used.
3040 [n]g Like G, except if n is not specified, it goes to the most recent
3042 remembered line.
3043 [n]/string
3045 Search backward through the history for the nth line containing
3046 string; if string starts with ‘^’, the remainder of the string
3047 must appear at the start of the history line for it to match.
3048 [n]?string
3050 Same as /, except it searches forward through the history.
3051 [n]n Search for the nth occurrence of the last search string; the
3053 direction of the search is the same as the last search.
3054 [n]N Search for the nth occurrence of the last search string; the
3056 direction of the search is the opposite of the last search.
3057 Edit commands
3059 [n]a Append text n times; goes into insert mode just after the current
3061 position. The append is only replicated if command mode is re-
3062 entered i.e. ⟨esc⟩ is used.
3063 [n]A Same as a, except it appends at the end of the line.
3065 [n]i Insert text n times; goes into insert mode at the current posi‐
3067 tion. The insertion is only replicated if command mode is re-
3068 entered i.e. ⟨esc⟩ is used.
3069 [n]I Same as i, except the insertion is done just before the first
3071 non-blank character.
3072 [n]s Substitute the next n characters (i.e. delete the characters and
3074 go into insert mode).
3075 S Substitute whole line. All characters from the first non-blank
3077 character to the end of the line are deleted and insert mode is
3078 entered.
3079 [n]cmove-cmd
3081 Change from the current position to the position resulting from n
3082 move-cmds (i.e. delete the indicated region and go into insert
3083 mode); if move-cmd is c, the line starting from the first non-
3084 blank character is changed.
3085 C Change from the current position to the end of the line (i.e.
3087 delete to the end of the line and go into insert mode).
3088 [n]x Delete the next n characters.
3090 [n]X Delete the previous n characters.
3092 D Delete to the end of the line.
3094 [n]dmove-cmd
3096 Delete from the current position to the position resulting from n
3097 move-cmds; move-cmd is a movement command (see above) or d, in
3098 which case the current line is deleted.
3099 [n]rc Replace the next n characters with the character c.
3101 [n]R Replace. Enter insert mode but overwrite existing characters
3103 instead of inserting before existing characters. The replacement
3104 is repeated n times.
3105 [n]~ Change the case of the next n characters.
3107 [n]ymove-cmd
3109 Yank from the current position to the position resulting from n
3110 move-cmds into the yank buffer; if move-cmd is y, the whole line
3111 is yanked.
3112 Y Yank from the current position to the end of the line.
3114 [n]p Paste the contents of the yank buffer just after the current
3116 position, n times.
3117 [n]P Same as p, except the buffer is pasted at the current position.
3119 Miscellaneous vi commands
3121 ^J and ^M
3123 The current line is read, parsed, and executed by the shell.
3124 ^L and ^R
3126 Redraw the current line.
3127 [n]. Redo the last edit command n times.
3129 u Undo the last edit command.
3131 U Undo all changes that have been made to the current line.
3133 intr and quit
3135 The interrupt and quit terminal characters cause the current line
3136 to be deleted and a new prompt to be printed.
3137
3139 ~/.mkshrc User mkshrc profile (non-privileged interactive
3140 shells); see Startup files. The location can be
3141 changed at compile time (for embedded systems); AOSP
3142 Android builds use /system/etc/mkshrc.
3143 ~/.profile User profile (non-privileged login shells); see
3144 Startup files near the top of this manual.
3145 /etc/profile System profile (login shells); see Startup files.
3146 /etc/shells Shell database.
3147 /etc/suid_profile Suid profile (privileged shells); see Startup files.
3148 Note: On Android, /system/etc/ contains the system and suid profile.
3150
3152 awk(1), cat(1), ed(1), getopt(1), printf(1), sed(1), sh(1), stty(1),
3153 dup(2), execve(2), getgid(2), getuid(2), mknod(2), mkfifo(2), open(2),
3154 pipe(2), rename(2), wait(2), getopt(3), nl_langinfo(3), setlocale(3),
3155 signal(3), system(3), tty(4), shells(5), environ(7), script(7), utf-8(7),
3156 mknod(8)
3157 http://docsrv.sco.com:507/en/man/html.C/sh.C.html
3159 Morris Bolsky, The KornShell Command and Programming Language, Prentice
3161 Hall PTR, xvi + 356 pages, 1989, ISBN 978-0-13-516972-8 (0-13-516972-0).
3162 Morris I. Bolsky and David G. Korn, The New KornShell Command and
3164 Programming Language (2nd Edition), Prentice Hall PTR, xvi + 400 pages,
3165 1995, ISBN 978-0-13-182700-4 (0-13-182700-6).
3166 Stephen G. Kochan and Patrick H. Wood, UNIX Shell Programming, Hayden,
3168 Revised Edition, xi + 490 pages, 1990, ISBN 978-0-672-48448-3
3169 (0-672-48448-X).
3170 IEEE Inc., IEEE Standard for Information Technology – Portable Operating
3172 System Interface (POSIX), IEEE Press, Part 2: Shell and Utilities,
3173 xvii + 1195 pages, 1993, ISBN 978-1-55937-255-8 (1-55937-255-9).
3174 Bill Rosenblatt, Learning the Korn Shell, O'Reilly, 360 pages, 1993, ISBN
3176 978-1-56592-054-5 (1-56592-054-6).
3177 Bill Rosenblatt and Arnold Robbins, Learning the Korn Shell, Second
3179 Edition, O'Reilly, 432 pages, 2002, ISBN 978-0-596-00195-7
3180 (0-596-00195-9).
3181 Barry Rosenberg, KornShell Programming Tutorial, Addison-Wesley
3183 Professional, xxi + 324 pages, 1991, ISBN 978-0-201-56324-5
3184 (0-201-56324-X).
3185
3187 The MirBSD Korn Shell is developed by Thorsten Glaser <tg@mirbsd.org> and
3188 currently maintained as part of The MirOS Project. This shell is based
3189 upon the Public Domain Korn SHell. The developer of mksh recognises the
3190 efforts of the pdksh authors, who had dedicated their work into Public
3191 Domain, our users, and all contributors, such as the Debian and OpenBSD
3192 projects. See the documentation, CVS, and web site for details.
3193
3195 mksh only supports the Unicode BMP (Basic Multilingual Plane). It has a
3196 different scope model from AT&T UNIX ksh, which leads to subtile differ‐
3197 ences in semantics for identical builtins.
3198 The parts of a pipeline, like below, are executed in subshells. Thus,
3200 variable assignments inside them fail. Use co-processes instead.
3201 foo | bar | read baz # will not change $baz
3203 foo | bar |& read -p baz # will, however, do so
3204
3206 Suspending (using ^Z) pipelines like the one below will only suspend the
3207 currently running part of the pipeline; in this example, “fubar” is imme‐
3208 diately printed on suspension (but not later after an fg).
3209 $ /bin/sleep 666 && echo fubar
3211 This document attempts to describe mksh R40c and up, compiled without any
3213 options impacting functionality, such as MKSH_SMALL, for an operating
3214 environment supporting all of its advanced needs. Please report bugs in
3215 mksh to the MirOS mailing list at ⟨miros-discuss@mirbsd.org⟩ or in the
3216 #!/bin/mksh (or #ksh) IRC channel at irc.freenode.net:6667.
3217MirBSD November 19, 2011 MirBSD