1MKSH(1) BSD General Commands Manual MKSH(1)
2
4 mksh, sh — MirBSD Korn shell
5
7 mksh [-+abCefhiklmnprUuvXx] [-T [!]tty | -] [-+o option] [-c string | -s
8 | 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. At times, this
15 manual page may give scripting advice; while it sometimes does take por‐
16 table shell scripting or various standards into account all information
17 is first and foremost presented with mksh in mind and should be taken as
18 such.
19 I use Android, OS/2, etc. so what...?
21 Please refer to: http://www.mirbsd.org/mksh-faq.htm#sowhatismksh
22 Invocation
24 Most builtins can be called directly, for example if a link points from
25 its name to the shell; not all make sense, have been tested or work at
26 all though.
27 The options are as follows:
29 -c string mksh will execute the command(s) contained in string.
31 -i Interactive shell. A shell that reads commands from standard
33 input is “interactive” if this option is used or if both stan‐
34 dard input and standard error are attached to a tty(4). An
35 interactive shell has job control enabled, ignores the SIGINT,
36 SIGQUIT and SIGTERM signals, and prints prompts before reading
37 input (see the PS1 and PS2 parameters). It also processes the
38 ENV parameter or the mkshrc file (see below). For non-inter‐
39 active shells, the trackall option is on by default (see the
40 set command below).
41 -l Login shell. If the basename the shell is called with (i.e.
43 argv[0]) starts with ‘-’ or if this option is used, the shell
44 is assumed to be a login shell; see Startup files below.
45 -p Privileged shell. A shell is “privileged” if the real user ID
47 or group ID does not match the effective user ID or group ID
48 (see getuid(2) and getgid(2)). Clearing the privileged option
49 causes the shell to set its effective user ID (group ID) to
50 its initial real user ID (group ID). For further implica‐
51 tions, see Startup files. If the shell is privileged and this
52 flag is not explicitly set, the “privileged” option is cleared
53 automatically after processing the startup files.
54 -r Restricted shell. A shell is “restricted” if the basename the
56 shell is called with (i.e. argv[0]) starts with ‘r’ or if this
57 option is used. The following restrictions come into effect
58 after the shell processes any profile and ENV files:
59 · The cd (and chdir) command is disabled.
61 · The SHELL, ENV and PATH parameters cannot be changed.
62 · Command names can't be specified with absolute or relative
63 paths.
64 · The -p option of the built-in command command can't be
65 used.
66 · Redirections that create files can't be used (i.e. “>”,
67 “>|”, “>>”, “<>”).
68 -s The shell reads commands from standard input; all non-option
70 arguments are positional parameters.
71 -T name Spawn mksh on the tty(4) device given. The paths name,
73 /dev/ttyCname and /dev/ttyname are attempted in order. Unless
74 name begins with an exclamation mark (‘!’), this is done in a
75 subshell and returns immediately. If name is a dash (‘-’),
76 detach from controlling terminal (daemonise) instead.
77 In addition to the above, the options described in the set built-in com‐
79 mand can also be used on the command line: both [-+abCefhkmnuvXx] and
80 [-+o option] can be used for single letter or long options, respectively.
81 If neither the -c nor the -s option is specified, the first non-option
83 argument specifies the name of a file the shell reads commands from. If
84 there are no non-option arguments, the shell reads commands from the
85 standard input. The name of the shell (i.e. the contents of $0) is
86 determined as follows: if the -c option is used and there is a non-option
87 argument, it is used as the name; if commands are being read from a file,
88 the file is used as the name; otherwise, the basename the shell was
89 called with (i.e. argv[0]) is used.
90 The exit status of the shell is 127 if the command file specified on the
92 command line could not be opened, or non-zero if a fatal syntax error
93 occurred during the execution of a script. In the absence of fatal
94 errors, the exit status is that of the last command executed, or zero if
95 no command is executed.
96 Startup files
98 For the actual location of these files, see FILES. A login shell pro‐
99 cesses the system profile first. A privileged shell then processes the
100 suid profile. A non-privileged login shell processes the user profile
101 next. A non-privileged interactive shell checks the value of the ENV
102 parameter after subjecting it to parameter, command, arithmetic and tilde
103 (‘~’) substitution; if unset or empty, the user mkshrc profile is pro‐
104 cessed; otherwise, if a file whose name is the substitution result
105 exists, it is processed; non-existence is silently ignored. A privileged
106 shell then drops privileges if neither was the -p option given on the
107 command line nor set during execution of the startup files.
108 Command syntax
110 The shell begins parsing its input by removing any backslash-newline com‐
111 binations, then breaking it into words. Words (which are sequences of
112 characters) are delimited by unquoted whitespace characters (space, tab
113 and newline) or meta-characters (‘<’, ‘>’, ‘|’, ‘;’, ‘(’, ‘)’ and ‘&’).
114 Aside from delimiting words, spaces and tabs are ignored, while newlines
115 usually delimit commands. The meta-characters are used in building the
116 following tokens: “<”, “<&”, “<<”, “<<<”, “>”, “>&”, “>>”, “&>”, etc. are
117 used to specify redirections (see Input/output redirection below); “|” is
118 used to create pipelines; “|&” is used to create co-processes (see
119 Co-processes below); “;” is used to separate commands; “&” is used to
120 create asynchronous pipelines; “&&” and “||” are used to specify condi‐
121 tional execution; “;;”, “;&” and “;|” are used in case statements; “((
122 ... ))” is used in arithmetic expressions; and lastly, “( ... )” is used
123 to create subshells.
124 Whitespace and meta-characters can be quoted individually using a back‐
126 slash (‘\’), or in groups using double (‘"’) or single (“'”) quotes.
127 Note that the following characters are also treated specially by the
128 shell and must be quoted if they are to represent themselves: ‘\’, ‘"’,
129 “'”, ‘#’, ‘$’, ‘`’, ‘~’, ‘{’, ‘}’, ‘*’, ‘?’ and ‘[’. The first three of
130 these are the above mentioned quoting characters (see Quoting below);
131 ‘#’, if used at the beginning of a word, introduces a comment – every‐
132 thing after the ‘#’ up to the nearest newline is ignored; ‘$’ is used to
133 introduce parameter, command and arithmetic substitutions (see
134 Substitution below); ‘`’ introduces an old-style command substitution
135 (see Substitution below); ‘~’ begins a directory expansion (see Tilde
136 expansion below); ‘{’ and ‘}’ delimit csh(1)-style alternations (see
137 Brace expansion below); and finally, ‘*’, ‘?’ and ‘[’ are used in file
138 name generation (see File name patterns below).
139 As words and tokens are parsed, the shell builds commands, of which there
141 are two basic types: simple-commands, typically programmes that are exe‐
142 cuted, and compound-commands, such as for and if statements, grouping
143 constructs and function definitions.
144 A simple-command consists of some combination of parameter assignments
146 (see Parameters below), input/output redirections (see Input/output
147 redirections below) and command words; the only restriction is that
148 parameter assignments come before any command words. The command words,
149 if any, define the command that is to be executed and its arguments. The
150 command may be a shell built-in command, a function or an external com‐
151 mand (i.e. a separate executable file that is located using the PATH
152 parameter; see Command execution below). Note that all command con‐
153 structs have an exit status: for external commands, this is related to
154 the status returned by wait(2) (if the command could not be found, the
155 exit status is 127; if it could not be executed, the exit status is 126);
156 the exit status of other command constructs (built-in commands, func‐
157 tions, compound-commands, pipelines, lists, etc.) are all well-defined
158 and are described where the construct is described. The exit status of a
159 command consisting only of parameter assignments is that of the last com‐
160 mand substitution performed during the parameter assignment or 0 if there
161 were no command substitutions.
162 Commands can be chained together using the “|” token to form pipelines,
164 in which the standard output of each command but the last is piped (see
165 pipe(2)) to the standard input of the following command. The exit status
166 of a pipeline is that of its last command, unless the pipefail option is
167 set (see there). All commands of a pipeline are executed in separate
168 subshells; this is allowed by POSIX but differs from both variants of
169 AT&T UNIX ksh, where all but the last command were executed in subshells;
170 see the read builtin's description for implications and workarounds. A
171 pipeline may be prefixed by the “!” reserved word which causes the exit
172 status of the pipeline to be logically complemented: if the original sta‐
173 tus was 0, the complemented status will be 1; if the original status was
174 not 0, the complemented status will be 0.
175 Lists of commands can be created by separating pipelines by any of the
177 following tokens: “&&”, “||”, “&”, “|&” and “;”. The first two are for
178 conditional execution: “cmd1 && cmd2” executes cmd2 only if the exit sta‐
179 tus of cmd1 is zero; “||” is the opposite – cmd2 is executed only if the
180 exit status of cmd1 is non-zero. “&&” and “||” have equal precedence
181 which is higher than that of “&”, “|&” and “;”, which also have equal
182 precedence. Note that the “&&” and “||” operators are
183 "left-associative". For example, both of these commands will print only
184 "bar":
185 $ false && echo foo || echo bar
187 $ true || echo foo && echo bar
188 The “&” token causes the preceding command to be executed asynchronously;
190 that is, the shell starts the command but does not wait for it to com‐
191 plete (the shell does keep track of the status of asynchronous commands;
192 see Job control below). When an asynchronous command is started when job
193 control is disabled (i.e. in most scripts), the command is started with
194 signals SIGINT and SIGQUIT ignored and with input redirected from
195 /dev/null (however, redirections specified in the asynchronous command
196 have precedence). The “|&” operator starts a co-process which is a spe‐
197 cial kind of asynchronous process (see Co-processes below). Note that a
198 command must follow the “&&” and “||” operators, while it need not follow
199 “&”, “|&” or “;”. The exit status of a list is that of the last command
200 executed, with the exception of asynchronous lists, for which the exit
201 status is 0.
202 Compound commands are created using the following reserved words. These
204 words are only recognised if they are unquoted and if they are used as
205 the first word of a command (i.e. they can't be preceded by parameter
206 assignments or redirections):
207 case else function then ! (
209 do esac if time [[ ((
210 done fi in until {
211 elif for select while }
212 In the following compound command descriptions, command lists (denoted as
214 list) that are followed by reserved words must end with a semicolon, a
215 newline or a (syntactically correct) reserved word. For example, the
216 following are all valid:
217 $ { echo foo; echo bar; }
219 $ { echo foo; echo bar<newline>}
220 $ { { echo foo; echo bar; } }
221 This is not valid:
223 $ { echo foo; echo bar }
225 case word in [[(] pattern [| pattern] ...) list <terminator>] ... esac
227 The case statement attempts to match word against a specified
228 pattern; the list associated with the first successfully matched
229 pattern is executed. Patterns used in case statements are the same
230 as those used for file name patterns except that the restrictions
231 regarding ‘.’ and ‘/’ are dropped. Note that any unquoted space
232 before and after a pattern is stripped; any space within a pattern
233 must be quoted. Both the word and the patterns are subject to
234 parameter, command and arithmetic substitution, as well as tilde
235 substitution.
236 For historical reasons, open and close braces may be used instead
238 of in and esac, for example: “case $foo { (ba[rz]|blah) date ;; }”
239 The list <terminator>s are:
241 “;;” Terminate after the list.
243 “;&” Fall through into the next list.
245 “;|” Evaluate the remaining pattern-list tuples.
247 The exit status of a case statement is that of the executed list;
249 if no list is executed, the exit status is zero.
250 for name [in word ...] ; do list; done
252 For each word in the specified word list, the parameter name is set
253 to the word and list is executed. The exit status of a for state‐
254 ment is the last exit status of list; if list is never executed,
255 the exit status is zero. If in is not used to specify a word list,
256 the positional parameters ($1, $2, etc.) are used instead; in this
257 case, use a newline instead of the semicolon (‘;’) for portability.
258 For historical reasons, open and close braces may be used instead
259 of do and done, as in “for i; { echo $i; }” (not portable).
260 function name { list; }
262 Defines the function name (see Functions below). All redirections
263 specified after a function definition are performed whenever the
264 function is executed, not when the function definition is executed.
265 name() command
267 Mostly the same as function (see above and Functions below). Most
268 amounts of space and tab after name will be ignored.
269 function name() { list; }
271 bashism for name() { list; } (the function keyword is ignored).
272 if list; then list; [elif list; then list;] ... [else list;] fi
274 If the exit status of the first list is zero, the second list is
275 executed; otherwise, the list following the elif, if any, is exe‐
276 cuted with similar consequences. If all the lists following the if
277 and elifs fail (i.e. exit with non-zero status), the list following
278 the else is executed. The exit status of an if statement is that
279 of whatever non-conditional (not the first) list that is executed;
280 if no non-conditional list is executed, the exit status is zero.
281 select name [in word ...]; do list; done
283 The select statement provides an automatic method of presenting the
284 user with a menu and selecting from it. An enumerated list of the
285 specified words is printed on standard error, followed by a prompt
286 (PS3: normally “#? ”). A number corresponding to one of the enu‐
287 merated words is then read from standard input, name is set to the
288 selected word (or unset if the selection is not valid), REPLY is
289 set to what was read (leading and trailing space is stripped), and
290 list is executed. If a blank line (i.e. zero or more IFS octets)
291 is entered, the menu is reprinted without executing list.
292 When list completes, the enumerated list is printed if REPLY is
294 empty, the prompt is printed, and so on. This process continues
295 until an end-of-file is read, an interrupt is received, or a break
296 statement is executed inside the loop. The exit status of a select
297 statement is zero if a break statement is used to exit the loop,
298 non-zero otherwise. If “in word ...” is omitted, the positional
299 parameters are used. For historical reasons, open and close braces
300 may be used instead of do and done, as in: “select i; { echo $i; }”
301 time [-p] [pipeline]
303 The Command execution section describes the time reserved word.
304 until list; do list; done
306 This works like while (see below), except that the body list is
307 executed only while the exit status of the first list is non-zero.
308 while list; do list; done
310 A while is a pre-checked loop. Its body list is executed as often
311 as the exit status of the first list is zero. The exit status of a
312 while statement is the last exit status of the list in the body of
313 the loop; if the body is not executed, the exit status is zero.
314 [[ expression ]]
316 Similar to the test and [ ... ] commands (described later), with
317 the following exceptions:
318 · Field splitting and globbing are not performed on arguments.
320 · The -a (AND) and -o (OR) operators are replaced, respectively,
322 with “&&” and “||”.
323 · Operators (e.g. “-f”, “=”, “!”) must be unquoted.
325 · Parameter, command and arithmetic substitutions are performed
327 as expressions are evaluated and lazy expression evaluation is
328 used for the “&&” and “||” operators. This means that in the
329 following statement, $(<foo) is evaluated if and only if the
330 file foo exists and is readable:
331 $ [[ -r foo && $(<foo) = b*r ]]
333 · The second operand of the “=” and “!=” expressions is a pattern
335 (e.g. the comparison [[ foobar = f*r ]] succeeds). This even
336 works indirectly, while quoting forces literal interpretation:
337 $ bar=foobar; baz='f*r' # or: baz='f+(o)b?r'
339 $ [[ $bar = $baz ]]; echo $? # 0
340 $ [[ $bar = "$baz" ]]; echo $? # 1
341 { list; }
343 Compound construct; list is executed, but not in a subshell.
344 Note that “{” and “}” are reserved words, not meta-characters.
345 (list)
347 Execute list in a subshell, forking. There is no implicit way to
348 pass environment changes from a subshell back to its parent.
349 (( expression ))
351 The arithmetic expression expression is evaluated; equivalent to
352 ‘let "expression"’ in a compound construct.
353 See the let command and Arithmetic expressions below.
354 Quoting
356 Quoting is used to prevent the shell from treating characters or words
357 specially. There are three methods of quoting. First, ‘\’ quotes the
358 following character, unless it is at the end of a line, in which case
359 both the ‘\’ and the newline are stripped. Second, a single quote (“'”)
360 quotes everything up to the next single quote (this may span lines).
361 Third, a double quote (‘"’) quotes all characters, except ‘$’, ‘\’ and
362 ‘`’, up to the next unescaped double quote. ‘$’ and ‘`’ inside double
363 quotes have their usual meaning (i.e. parameter, arithmetic or command
364 substitution) except no field splitting is carried out on the results of
365 double-quoted substitutions, and the old-style form of command substitu‐
366 tion has backslash-quoting for double quotes enabled. If a ‘\’ inside a
367 double-quoted string is followed by ‘"’, ‘$’, ‘\’ or ‘`’, only the ‘\’ is
368 removed, i.e. the combination is replaced by the second character; if it
369 is followed by a newline, both the ‘\’ and the newline are stripped; oth‐
370 erwise, both the ‘\’ and the character following are unchanged.
371 If a single-quoted string is preceded by an unquoted ‘$’, C style back‐
373 slash expansion (see below) is applied (even single quote characters
374 inside can be escaped and do not terminate the string then); the expanded
375 result is treated as any other single-quoted string. If a double-quoted
376 string is preceded by an unquoted ‘$’, the ‘$’ is simply ignored.
377 Backslash expansion
379 In places where backslashes are expanded, certain C and AT&T UNIX ksh or
380 GNU bash style escapes are translated. These include “\a”, “\b”, “\f”,
381 “\n”, “\r”, “\t”, “\U########”, “\u####” and “\v”. For “\U########” and
382 “\u####”, ‘#’ means a hexadecimal digit (up to 4 or 8); these translate a
383 Universal Coded Character Set codepoint to UTF-8 (see CAVEATS on UCS lim‐
384 itations). Furthermore, “\E” and “\e” expand to the escape character.
385 In the print builtin mode, octal sequences must have the optional up to
387 three octal digits ‘#’ prefixed with the digit zero (“\0###”); hexadeci‐
388 mal sequences “\x##” are limited to up to two hexadecimal digits ‘#’;
389 both octal and hexadecimal sequences convert to raw octets; “\%”, where
390 ‘%’ is none of the above, translates to \% (backslashes are retained).
391 In C style mode, raw octet-yielding octal sequences “\###” must not have
393 the one up to three octal digits prefixed with the digit zero; hexadeci‐
394 mal sequences “\x##” greedily eat up as many hexadecimal digits ‘#’ as
395 they can and terminate with the first non-xdigit; below \x100 these pro‐
396 duce raw octets; above, they are equivalent to “\U#”. The sequence
397 “\c%”, where ‘%’ is any octet, translates to Ctrl-%, that is, “\c?”
398 becomes DEL, everything else is bitwise ANDed with 0x9F. “\%”, where ‘%’
399 is none of the above, translates to %: backslashes are trimmed even
400 before newlines.
401 Aliases
403 There are two types of aliases: normal command aliases and tracked
404 aliases. Command aliases are normally used as a short hand for a long or
405 often used command. The shell expands command aliases (i.e. substitutes
406 the alias name for its value) when it reads the first word of a command.
407 An expanded alias is re-processed to check for more aliases. If a com‐
408 mand alias ends in a space or tab, the following word is also checked for
409 alias expansion. The alias expansion process stops when a word that is
410 not an alias is found, when a quoted word is found, or when an alias word
411 that is currently being expanded is found. Aliases are specifically an
412 interactive feature: while they do happen to work in scripts and on the
413 command line in some cases, aliases are expanded during lexing, so their
414 use must be in a separate command tree from their definition; otherwise,
415 the alias will not be found. Noticeably, command lists (separated by
416 semicolon, in command substitutions also by newline) may be one same
417 parse tree.
418 The following command aliases are defined automatically by the shell:
420 autoload='\\builtin typeset -fu'
422 functions='\\builtin typeset -f'
423 hash='\\builtin alias -t'
424 history='\\builtin fc -l'
425 integer='\\builtin typeset -i'
426 local='\\builtin typeset'
427 login='\\builtin exec login'
428 nameref='\\builtin typeset -n'
429 nohup='nohup '
430 r='\\builtin fc -e -'
431 type='\\builtin whence -v'
432 Tracked aliases allow the shell to remember where it found a particular
434 command. The first time the shell does a path search for a command that
435 is marked as a tracked alias, it saves the full path of the command. The
436 next time the command is executed, the shell checks the saved path to see
437 that it is still valid, and if so, avoids repeating the path search.
438 Tracked aliases can be listed and created using alias -t. Note that
439 changing the PATH parameter clears the saved paths for all tracked
440 aliases. If the trackall option is set (i.e. set -o trackall or set -h),
441 the shell tracks all commands. This option is set automatically for non-
442 interactive shells. For interactive shells, only the following commands
443 are automatically tracked: cat(1), cc(1), chmod(1), cp(1), date(1),
444 ed(1), emacs(1), grep(1), ls(1), make(1), mv(1), pr(1), rm(1), sed(1),
445 sh(1), vi(1) and who(1).
446 Substitution
448 The first step the shell takes in executing a simple-command is to per‐
449 form substitutions on the words of the command. There are three kinds of
450 substitution: parameter, command and arithmetic. Parameter substitu‐
451 tions, which are described in detail in the next section, take the form
452 $name or ${...}; command substitutions take the form $(command) or (dep‐
453 recated) `command` or (executed in the current environment) ${ command;}
454 and strip trailing newlines; and arithmetic substitutions take the form
455 $((expression)). Parsing the current-environment command substitution
456 requires a space, tab or newline after the opening brace and that the
457 closing brace be recognised as a keyword (i.e. is preceded by a newline
458 or semicolon). They are also called funsubs (function substitutions) and
459 behave like functions in that local and return work, and in that exit
460 terminates the parent shell; shell options are shared.
461 Another variant of substitution are the valsubs (value substitutions)
463 ${|command;} which are also executed in the current environment, like
464 funsubs, but share their I/O with the parent; instead, they evaluate to
465 whatever the, initially empty, expression-local variable REPLY is set to
466 within the commands.
467 If a substitution appears outside of double quotes, the results of the
469 substitution are generally subject to word or field splitting according
470 to the current value of the IFS parameter. The IFS parameter specifies a
471 list of octets which are used to break a string up into several words;
472 any octets from the set space, tab and newline that appear in the IFS
473 octets are called “IFS whitespace”. Sequences of one or more IFS white‐
474 space octets, in combination with zero or one non-IFS whitespace octets,
475 delimit a field. As a special case, leading and trailing IFS whitespace
476 is stripped (i.e. no leading or trailing empty field is created by it);
477 leading or trailing non-IFS whitespace does create an empty field.
478 Example: If IFS is set to “<space>:” and VAR is set to
480 “<space>A<space>:<space><space>B::D”, the substitution for $VAR results
481 in four fields: “A”, “B”, “” (an empty field) and “D”. Note that if the
482 IFS parameter is set to the empty string, no field splitting is done; if
483 it is unset, the default value of space, tab and newline is used.
484 Also, note that the field splitting applies only to the immediate result
486 of the substitution. Using the previous example, the substitution for
487 $VAR:E results in the fields: “A”, “B”, “” and “D:E”, not “A”, “B”, “”,
488 “D” and “E”. This behavior is POSIX compliant, but incompatible with
489 some other shell implementations which do field splitting on the word
490 which contained the substitution or use IFS as a general whitespace
491 delimiter.
492 The results of substitution are, unless otherwise specified, also subject
494 to brace expansion and file name expansion (see the relevant sections
495 below).
496 A command substitution is replaced by the output generated by the speci‐
498 fied command which is run in a subshell. For $(command) and ${|command;}
499 and ${ command;} substitutions, normal quoting rules are used when
500 command is parsed; however, for the deprecated `command` form, a ‘\’ fol‐
501 lowed by any of ‘$’, ‘`’ or ‘\’ is stripped (as is ‘"’ when the substitu‐
502 tion is part of a double-quoted string); a backslash ‘\’ followed by any
503 other character is unchanged. As a special case in command substitu‐
504 tions, a command of the form <file is interpreted to mean substitute the
505 contents of file. Note that $(<foo) has the same effect as $(cat foo).
506 Note that some shells do not use a recursive parser for command substitu‐
508 tions, leading to failure for certain constructs; to be portable, use as
509 workaround “x=$(cat) <<\EOF” (or the newline-keeping “x=<<\EOF” exten‐
510 sion) instead to merely slurp the string. IEEE Std 1003.1 (“POSIX.1”)
511 recommends using case statements of the form x=$(case $foo in (bar) echo
512 $bar ;; (*) echo $baz ;; esac) instead, which would work but not serve as
513 example for this portability issue.
514 x=$(case $foo in bar) echo $bar ;; *) echo $baz ;; esac)
516 # above fails to parse on old shells; below is the workaround
517 x=$(eval $(cat)) <<\EOF
518 case $foo in bar) echo $bar ;; *) echo $baz ;; esac
519 EOF
520 Arithmetic substitutions are replaced by the value of the specified
522 expression. For example, the command print $((2+3*4)) displays 14. See
523 Arithmetic expressions for a description of an expression.
524 Parameters
526 Parameters are shell variables; they can be assigned values and their
527 values can be accessed using a parameter substitution. A parameter name
528 is either one of the special single punctuation or digit character param‐
529 eters described below, or a letter followed by zero or more letters or
530 digits (‘_’ counts as a letter). The latter form can be treated as
531 arrays by appending an array index of the form [expr] where expr is an
532 arithmetic expression. Array indices in mksh are limited to the range 0
533 through 4294967295, inclusive. That is, they are a 32-bit unsigned inte‐
534 ger.
535 Parameter substitutions take the form $name, ${name} or ${name[expr]}
537 where name is a parameter name. Substitutions of an an array in scalar
538 context, i.e. without an expr in the latter form mentioned above, expand
539 the element with the key “0”. Substitution of all array elements with
540 ${name[*]} and ${name[@]} works equivalent to $* and $@ for positional
541 parameters. If substitution is performed on a parameter (or an array
542 parameter element) that is not set, an empty string is substituted unless
543 the nounset option (set -u) is set, in which case an error occurs.
544 Parameters can be assigned values in a number of ways. First, the shell
546 implicitly sets some parameters like “#”, “PWD” and “$”; this is the only
547 way the special single character parameters are set. Second, parameters
548 are imported from the shell's environment at startup. Third, parameters
549 can be assigned values on the command line: for example, FOO=bar sets the
550 parameter “FOO” to “bar”; multiple parameter assignments can be given on
551 a single command line and they can be followed by a simple-command, in
552 which case the assignments are in effect only for the duration of the
553 command (such assignments are also exported; see below for the implica‐
554 tions of this). Note that both the parameter name and the ‘=’ must be
555 unquoted for the shell to recognise a parameter assignment. The con‐
556 struct FOO+=baz is also recognised; the old and new values are string-
557 concatenated with no separator. The fourth way of setting a parameter is
558 with the export, readonly and typeset commands; see their descriptions in
559 the Command execution section. Fifth, for and select loops set parame‐
560 ters as well as the getopts, read and set -A commands. Lastly, parame‐
561 ters can be assigned values using assignment operators inside arithmetic
562 expressions (see Arithmetic expressions below) or using the ${name=value}
563 form of the parameter substitution (see below).
564 Parameters with the export attribute (set using the export or typeset -x
566 commands, or by parameter assignments followed by simple commands) are
567 put in the environment (see environ(7)) of commands run by the shell as
568 name=value pairs. The order in which parameters appear in the environ‐
569 ment of a command is unspecified. When the shell starts up, it extracts
570 parameters and their values from its environment and automatically sets
571 the export attribute for those parameters.
572 Modifiers can be applied to the ${name} form of parameter substitution:
574 ${name:-word}
576 If name is set and not empty, it is substituted; otherwise, word
577 is substituted.
578 ${name:+word}
580 If name is set and not empty, word is substituted; otherwise,
581 nothing is substituted.
582 ${name:=word}
584 If name is set and not empty, it is substituted; otherwise, it is
585 assigned word and the resulting value of name is substituted.
586 ${name:?word}
588 If name is set and not empty, it is substituted; otherwise, word
589 is printed on standard error (preceded by name:) and an error
590 occurs (normally causing termination of a shell script, function,
591 or a script sourced using the “.” built-in). If word is omitted,
592 the string “parameter null or not set” is used instead.
593 Note that, for all of the above, word is actually considered quoted, and
595 special parsing rules apply. The parsing rules also differ on whether
596 the expression is double-quoted: word then uses double-quoting rules,
597 except for the double quote itself (‘"’) and the closing brace, which, if
598 backslash escaped, gets quote removal applied.
599 In the above modifiers, the ‘:’ can be omitted, in which case the condi‐
601 tions only depend on name being set (as opposed to set and not empty).
602 If word is needed, parameter, command, arithmetic and tilde substitution
603 are performed on it; if word is not needed, it is not evaluated.
604 The following forms of parameter substitution can also be used:
606 ${#name}
608 The number of positional parameters if name is “*”, “@” or not
609 specified; otherwise the length (in characters) of the string
610 value of parameter name.
611 ${#name[*]}
613 ${#name[@]}
614 The number of elements in the array name.
615 ${%name}
617 The width (in screen columns) of the string value of parameter
618 name, or -1 if ${name} contains a control character.
619 ${!name}
621 The name of the variable referred to by name. This will be name
622 except when name is a name reference (bound variable), created by
623 the nameref command (which is an alias for typeset -n). name
624 cannot be one of most special parameters (see below).
625 ${!name[*]}
627 ${!name[@]}
628 The names of indices (keys) in the array name.
629 ${name#pattern}
631 ${name##pattern}
632 If pattern matches the beginning of the value of parameter name,
633 the matched text is deleted from the result of substitution. A
634 single ‘#’ results in the shortest match, and two of them result
635 in the longest match.
636 ${name%pattern}
638 ${name%%pattern}
639 Like ${...#...} but deletes from the end of the value.
640 ${name/pattern/string}
642 ${name/#pattern/string}
643 ${name/%pattern/string}
644 ${name//pattern/string}
645 The longest match of pattern in the value of parameter name is
646 replaced with string (deleted if string is empty; the trailing
647 slash (‘/’) may be omitted in that case). A leading slash fol‐
648 lowed by ‘#’ or ‘%’ causes the pattern to be anchored at the
649 beginning or end of the value, respectively; empty unanchored
650 patterns cause no replacement; a single leading slash or use of a
651 pattern that matches the empty string causes the replacement to
652 happen only once; two leading slashes cause all occurrences of
653 matches in the value to be replaced. May be slow on long
654 strings.
655 ${name@/pattern/string}
657 The same as ${name//pattern/string}, except that both pattern and
658 string are expanded anew for each iteration. Use with KSH_MATCH.
659 ${name:pos:len}
661 The first len characters of name, starting at position pos, are
662 substituted. Both pos and :len are optional. If pos is nega‐
663 tive, counting starts at the end of the string; if it is omitted,
664 it defaults to 0. If len is omitted or greater than the length
665 of the remaining string, all of it is substituted. Both pos and
666 len are evaluated as arithmetic expressions.
667 ${name@#}
669 The hash (using the BAFH algorithm) of the expansion of name.
670 This is also used internally for the shell's hashtables.
671 ${name@Q}
673 A quoted expression safe for re-entry, whose value is the value
674 of the name parameter, is substituted.
675 Note that pattern may need extended globbing pattern (@(...)), single
677 ('...') or double ("...") quote escaping unless -o sh is set.
678 The following special parameters are implicitly set by the shell and can‐
680 not be set directly using assignments:
681 ! Process ID of the last background process started. If no back‐
683 ground processes have been started, the parameter is not set.
684 # The number of positional parameters ($1, $2, etc.).
686 $ The PID of the shell or, if it is a subshell, the PID of the
688 original shell. Do NOT use this mechanism for generating tempo‐
689 rary file names; see mktemp(1) instead.
690 - The concatenation of the current single letter options (see the
692 set command below for a list of options).
693 ? The exit status of the last non-asynchronous command executed.
695 If the last command was killed by a signal, $? is set to 128 plus
696 the signal number, but at most 255.
697 0 The name of the shell, determined as follows: the first argument
699 to mksh if it was invoked with the -c option and arguments were
700 given; otherwise the file argument, if it was supplied; or else
701 the basename the shell was invoked with (i.e. argv[0]). $0 is
702 also set to the name of the current script or the name of the
703 current function, if it was defined with the function keyword
704 (i.e. a Korn shell style function).
705 1 .. 9 The first nine positional parameters that were supplied to the
707 shell, function, or script sourced using the “.” built-in. Fur‐
708 ther positional parameters may be accessed using ${number}.
709 * All positional parameters (except 0), i.e. $1, $2, $3, ...
711 If used outside of double quotes, parameters are separate words
712 (which are subjected to word splitting); if used within double
713 quotes, parameters are separated by the first character of the
714 IFS parameter (or the empty string if IFS is unset.
715 @ Same as $*, unless it is used inside double quotes, in which case
717 a separate word is generated for each positional parameter. If
718 there are no positional parameters, no word is generated. "$@"
719 can be used to access arguments, verbatim, without losing empty
720 arguments or splitting arguments with spaces (IFS, actually).
721 The following parameters are set and/or used by the shell:
723 _ (underscore) When an external command is executed by the
725 shell, this parameter is set in the environment of the new
726 process to the path of the executed command. In interactive
727 use, this parameter is also set in the parent shell to the
728 last word of the previous command.
729 BASHPID The PID of the shell or subshell.
731 CDPATH Like PATH, but used to resolve the argument to the cd built-
733 in command. Note that if CDPATH is set and does not contain
734 “.” or an empty string element, the current directory is not
735 searched. Also, the cd built-in command will display the
736 resulting directory when a match is found in any search path
737 other than the empty path.
738 COLUMNS Set to the number of columns on the terminal or window. If
740 never unset and not imported, always set dynamically; unless
741 the value as reported by stty(1) is non-zero and sane enough
742 (minimum is 12x3), defaults to 80; similar for LINES. This
743 parameter is used by the interactive line editing modes and
744 by the select, set -o and kill -l commands to format infor‐
745 mation columns. Importing from the environment or unsetting
746 this parameter removes the binding to the actual terminal
747 size in favour of the provided value.
748 ENV If this parameter is found to be set after any profile files
750 are executed, the expanded value is used as a shell startup
751 file. It typically contains function and alias definitions.
752 EPOCHREALTIME
754 Time since the epoch, as returned by gettimeofday(2), for‐
755 matted as decimal tv_sec followed by a dot (‘.’) and tv_usec
756 padded to exactly six decimal digits.
757 EXECSHELL If set, this parameter is assumed to contain the shell that
759 is to be used to execute commands that execve(2) fails to
760 execute and which do not start with a “#!shell” sequence.
761 FCEDIT The editor used by the fc command (see below).
763 FPATH Like PATH, but used when an undefined function is executed
765 to locate the file defining the function. It is also
766 searched when a command can't be found using PATH. See
767 Functions below for more information.
768 HISTFILE The name of the file used to store command history. When
770 assigned to or unset, the file is opened, history is trun‐
771 cated then loaded from the file; subsequent new commands
772 (possibly consisting of several lines) are appended once
773 they successfully compiled. Also, several invocations of
774 the shell will share history if their HISTFILE parameters
775 all point to the same file.
776 Note: If HISTFILE is unset or empty, no history file is
778 used. This is different from AT&T UNIX ksh.
779 HISTSIZE The number of commands normally stored for history. The
781 default is 2047. The maximum is 65535.
782 HOME The default directory for the cd command and the value sub‐
784 stituted for an unqualified ~ (see Tilde expansion below).
785 IFS Internal field separator, used during substitution and by
787 the read command, to split values into distinct arguments;
788 normally set to space, tab and newline. See Substitution
789 above for details.
790 Note: This parameter is not imported from the environment
792 when the shell is started.
793 KSHEGID The effective group id of the shell at startup.
795 KSHGID The real group id of the shell at startup.
797 KSHUID The real user id of the shell at startup.
799 KSH_MATCH The last matched string. In a future version, this will be
801 an indexed array, with indexes 1 and up capturing matching
802 groups. Set by string comparisons (= and !=) in double-
803 bracket test expressions when a match is found (when !=
804 returns false), by case when a match is encountered, and by
805 the substitution operations ${x#pat}, ${x##pat}, ${x%pat},
806 ${x%%pat}, ${x/pat/rpl}, ${x/#pat/rpl}, ${x/%pat/rpl},
807 ${x//pat/rpl}, and ${x@/pat/rpl}. See the end of the Emacs
808 editing mode documentation for an example.
809 KSH_VERSION The name and version of the shell (read-only). See also the
811 version commands in Emacs editing mode and Vi editing mode
812 sections, below.
813 LINENO The line number of the function or shell script that is cur‐
815 rently being executed.
816 LINES Set to the number of lines on the terminal or window.
818 Defaults to 24; always set, unless imported or unset. See
819 COLUMNS.
820 OLDPWD The previous working directory. Unset if cd has not suc‐
822 cessfully changed directories since the shell started or if
823 the shell doesn't know where it is.
824 OPTARG When using getopts, it contains the argument for a parsed
826 option, if it requires one.
827 OPTIND The index of the next argument to be processed when using
829 getopts. Assigning 1 to this parameter causes getopts to
830 process arguments from the beginning the next time it is
831 invoked.
832 PATH A colon (semicolon on OS/2) separated list of directories
834 that are searched when looking for commands and files
835 sourced using the “.” command (see below). An empty string
836 resulting from a leading or trailing (semi)colon, or two
837 adjacent ones, is treated as a “.” (the current directory).
838 PATHSEP A colon (semicolon on OS/2), for the user's convenience.
840 PGRP The process ID of the shell's process group leader.
842 PIPESTATUS An array containing the errorlevel (exit status) codes, one
844 by one, of the last pipeline run in the foreground.
845 PPID The process ID of the shell's parent.
847 PS1 The primary prompt for interactive shells. Parameter, com‐
849 mand and arithmetic substitutions are performed, and ‘!’ is
850 replaced with the current command number (see the fc command
851 below). A literal ‘!’ can be put in the prompt by placing
852 “!!” in PS1.
853 The default prompt is “$ ” for non-root users, “# ” for
855 root. If mksh is invoked by root and PS1 does not contain a
856 ‘#’ character, the default value will be used even if PS1
857 already exists in the environment.
858 The mksh distribution comes with a sample dot.mkshrc con‐
860 taining a sophisticated example, but you might like the fol‐
861 lowing one (note that ${HOSTNAME:=$(hostname)} and the root-
862 vs-user distinguishing clause are (in this example) executed
863 at PS1 assignment time, while the $USER and $PWD are escaped
864 and thus will be evaluated each time a prompt is displayed):
865 PS1='${USER:=$(id -un)}'"@${HOSTNAME:=$(hostname)}:\$PWD $(
867 if (( USER_ID )); then print \$; else print \#; fi) "
868 Note that since the command-line editors try to figure out
870 how long the prompt is (so they know how far it is to the
871 edge of the screen), escape codes in the prompt tend to mess
872 things up. You can tell the shell not to count certain
873 sequences (such as escape codes) by prefixing your prompt
874 with a character (such as Ctrl-A) followed by a carriage
875 return and then delimiting the escape codes with this char‐
876 acter. Any occurrences of that character in the prompt are
877 not printed. By the way, don't blame me for this hack; it's
878 derived from the original ksh88(1), which did print the
879 delimiter character so you were out of luck if you did not
880 have any non-printing characters.
881 Since backslashes and other special characters may be inter‐
883 preted by the shell, to set PS1 either escape the backslash
884 itself or use double quotes. The latter is more practical.
885 This is a more complex example, avoiding to directly enter
886 special characters (for example with ^V in the emacs editing
887 mode), which embeds the current working directory, in
888 reverse video (colour would work, too), in the prompt
889 string:
890 x=$(print \\001) # otherwise unused char
892 PS1="$x$(print \\r)$x$(tput so)$x\$PWD$x$(tput se)$x> "
893 Due to a strong suggestion from David G. Korn, mksh now also
895 supports the following form:
896 PS1=$'\1\r\1\e[7m\1$PWD\1\e[0m\1> '
898 PS2 Secondary prompt string, by default “> ”, used when more
900 input is needed to complete a command.
901 PS3 Prompt used by the select statement when reading a menu
903 selection. The default is “#? ”.
904 PS4 Used to prefix commands that are printed during execution
906 tracing (see the set -x command below). Parameter, command
907 and arithmetic substitutions are performed before it is
908 printed. The default is “+ ”. You may want to set it to
909 “[$EPOCHREALTIME] ” instead, to include timestamps.
910 PWD The current working directory. May be unset or empty if the
912 shell doesn't know where it is.
913 RANDOM Each time RANDOM is referenced, it is assigned a number
915 between 0 and 32767 from a Linear Congruential PRNG first.
916 REPLY Default parameter for the read command if no names are
918 given. Also used in select loops to store the value that is
919 read from standard input.
920 SECONDS The number of seconds since the shell started or, if the
922 parameter has been assigned an integer value, the number of
923 seconds since the assignment plus the value that was
924 assigned.
925 TMOUT If set to a positive integer in an interactive shell, it
927 specifies the maximum number of seconds the shell will wait
928 for input after printing the primary prompt (PS1). If the
929 time is exceeded, the shell exits.
930 TMPDIR The directory temporary shell files are created in. If this
932 parameter is not set or does not contain the absolute path
933 of a writable directory, temporary files are created in
934 /tmp.
935 USER_ID The effective user id of the shell at startup.
937 Tilde expansion
939 Tilde expansion, which is done in parallel with parameter substitution,
940 is applied to words starting with an unquoted ‘~’. In parameter assign‐
941 ments (such as those preceding a simple-command or those occurring in the
942 arguments of a declaration utility), tilde expansion is done after any
943 assignment (i.e. after the equals sign) or after an unquoted colon (‘:’);
944 login names are also delimited by colons. The Korn shell, except in
945 POSIX mode, always expands tildes after unquoted equals signs, not just
946 in assignment context (see below), and enables tab completion for tildes
947 after all unquoted colons during command line editing.
948 The characters following the tilde, up to the first ‘/’, if any, are
950 assumed to be a login name. If the login name is empty, ‘+’ or ‘-’, the
951 simplified value of the HOME, PWD or OLDPWD parameter is substituted,
952 respectively. Otherwise, the password file is searched for the login
953 name, and the tilde expression is substituted with the user's home direc‐
954 tory. If the login name is not found in the password file or if any
955 quoting or parameter substitution occurs in the login name, no substitu‐
956 tion is performed.
957 The home directory of previously expanded login names are cached and re-
959 used. The alias -d command may be used to list, change and add to this
960 cache (e.g. alias -d fac=/usr/local/facilities; cd ~fac/bin).
961 Brace expansion (alternation)
963 Brace expressions take the following form:
964 prefix{str1,...,strN}suffix
966 The expressions are expanded to N words, each of which is the concatena‐
968 tion of prefix, stri and suffix (e.g. “a{c,b{X,Y},d}e” expands to four
969 words: “ace”, “abXe”, “abYe” and “ade”). As noted in the example, brace
970 expressions can be nested and the resulting words are not sorted. Brace
971 expressions must contain an unquoted comma (‘,’) for expansion to occur
972 (e.g. {} and {foo} are not expanded). Brace expansion is carried out
973 after parameter substitution and before file name generation.
974 File name patterns
976 A file name pattern is a word containing one or more unquoted ‘?’, ‘*’,
977 ‘+’, ‘@’ or ‘!’ characters or “[...]” sequences. Once brace expansion
978 has been performed, the shell replaces file name patterns with the sorted
979 names of all the files that match the pattern (if no files match, the
980 word is left unchanged). The pattern elements have the following mean‐
981 ing:
982 ? Matches any single character.
984 * Matches any sequence of octets.
986 [...] Matches any of the octets inside the brackets. Ranges of octets
988 can be specified by separating two octets by a ‘-’ (e.g. “[a0-9]”
989 matches the letter ‘a’ or any digit). In order to represent
990 itself, a ‘-’ must either be quoted or the first or last octet in
991 the octet list. Similarly, a ‘]’ must be quoted or the first
992 octet in the list if it is to represent itself instead of the end
993 of the list. Also, a ‘!’ appearing at the start of the list has
994 special meaning (see below), so to represent itself it must be
995 quoted or appear later in the list.
996 [!...] Like [...], except it matches any octet not inside the brackets.
998 *(pattern|...|pattern)
1000 Matches any string of octets that matches zero or more occur‐
1001 rences of the specified patterns. Example: The pattern
1002 *(foo|bar) matches the strings “”, “foo”, “bar”, “foobarfoo”,
1003 etc.
1004 +(pattern|...|pattern)
1006 Matches any string of octets that matches one or more occurrences
1007 of the specified patterns. Example: The pattern +(foo|bar)
1008 matches the strings “foo”, “bar”, “foobar”, etc.
1009 ?(pattern|...|pattern)
1011 Matches the empty string or a string that matches one of the
1012 specified patterns. Example: The pattern ?(foo|bar) only matches
1013 the strings “”, “foo” and “bar”.
1014 @(pattern|...|pattern)
1016 Matches a string that matches one of the specified patterns.
1017 Example: The pattern @(foo|bar) only matches the strings “foo”
1018 and “bar”.
1019 !(pattern|...|pattern)
1021 Matches any string that does not match one of the specified pat‐
1022 terns. Examples: The pattern !(foo|bar) matches all strings
1023 except “foo” and “bar”; the pattern !(*) matches no strings; the
1024 pattern !(?)* matches all strings (think about it).
1025 Note that complicated globbing, especially with alternatives, is slow;
1027 using separate comparisons may (or may not) be faster.
1028 Note that mksh (and pdksh) never matches “.” and “..”, but AT&T UNIX ksh,
1030 Bourne sh and GNU bash do.
1031 Note that none of the above pattern elements match either a period (‘.’)
1033 at the start of a file name or a slash (‘/’), even if they are explicitly
1034 used in a [...] sequence; also, the names “.” and “..” are never matched,
1035 even by the pattern “.*”.
1036 If the markdirs option is set, any directories that result from file name
1038 generation are marked with a trailing ‘/’.
1039 Input/output redirection
1041 When a command is executed, its standard input, standard output and stan‐
1042 dard error (file descriptors 0, 1 and 2, respectively) are normally
1043 inherited from the shell. Three exceptions to this are commands in pipe‐
1044 lines, for which standard input and/or standard output are those set up
1045 by the pipeline, asynchronous commands created when job control is dis‐
1046 abled, for which standard input is initially set to /dev/null, and com‐
1047 mands for which any of the following redirections have been specified:
1048 >file Standard output is redirected to file. If file does not
1050 exist, it is created; if it does exist, is a regular file,
1051 and the noclobber option is set, an error occurs; otherwise,
1052 the file is truncated. Note that this means the command cmd
1053 <foo >foo will open foo for reading and then truncate it when
1054 it opens it for writing, before cmd gets a chance to actually
1055 read foo.
1056 >|file Same as >, except the file is truncated, even if the
1058 noclobber option is set.
1059 >>file Same as >, except if file exists it is appended to instead of
1061 being truncated. Also, the file is opened in append mode, so
1062 writes always go to the end of the file (see open(2)).
1063 <file Standard input is redirected from file, which is opened for
1065 reading.
1066 <>file Same as <, except the file is opened for reading and writing.
1068 <<marker After reading the command line containing this kind of redi‐
1070 rection (called a “here document”), the shell copies lines
1071 from the command source into a temporary file until a line
1072 matching marker is read. When the command is executed, stan‐
1073 dard input is redirected from the temporary file. If marker
1074 contains no quoted characters, the contents of the temporary
1075 file are processed as if enclosed in double quotes each time
1076 the command is executed, so parameter, command and arithmetic
1077 substitutions are performed, along with backslash (‘\’)
1078 escapes for ‘$’, ‘`’, ‘\’ and “\newline”, but not for ‘"’.
1079 If multiple here documents are used on the same command line,
1080 they are saved in order.
1081 If no marker is given, the here document ends at the next <<
1083 and substitution will be performed. If marker is only a set
1084 of either single “''” or double ‘""’ quotes with nothing in
1085 between, the here document ends at the next empty line and
1086 substitution will not be performed.
1087 <<-marker Same as <<, except leading tabs are stripped from lines in
1089 the here document.
1090 <<<word Same as <<, except that word is the here document. This is
1092 called a here string.
1093 <&fd Standard input is duplicated from file descriptor fd. fd can
1095 be a single digit, indicating the number of an existing file
1096 descriptor; the letter ‘p’, indicating the file descriptor
1097 associated with the output of the current co-process; or the
1098 character ‘-’, indicating standard input is to be closed.
1099 >&fd Same as <&, except the operation is done on standard output.
1101 &>file Same as >file 2>&1. This is a deprecated (legacy) GNU bash
1103 extension supported by mksh which also supports the preceding
1104 explicit fd digit, for example, 3&>file is the same as 3>file
1105 2>&3 in mksh but a syntax error in GNU bash.
1106 &>|file, &>>file, &>&fd
1108 Same as >|file, >>file or >&fd, followed by 2>&1, as above.
1109 These are mksh extensions.
1110 In any of the above redirections, the file descriptor that is redirected
1112 (i.e. standard input or standard output) can be explicitly given by pre‐
1113 ceding the redirection with a single digit. Parameter, command and
1114 arithmetic substitutions, tilde substitutions, and, if the shell is
1115 interactive, file name generation are all performed on the file, marker
1116 and fd arguments of redirections. Note, however, that the results of any
1117 file name generation are only used if a single file is matched; if multi‐
1118 ple files match, the word with the expanded file name generation charac‐
1119 ters is used. Note that in restricted shells, redirections which can
1120 create files cannot be used.
1121 For simple-commands, redirections may appear anywhere in the command; for
1123 compound-commands (if statements, etc.), any redirections must appear at
1124 the end. Redirections are processed after pipelines are created and in
1125 the order they are given, so the following will print an error with a
1126 line number prepended to it:
1127 $ cat /foo/bar 2>&1 >/dev/null | pr -n -t
1129 File descriptors created by I/O redirections are private to the shell.
1131 Arithmetic expressions
1133 Integer arithmetic expressions can be used with the let command, inside
1134 $((...)) expressions, inside array references (e.g. name[expr]), as
1135 numeric arguments to the test command, and as the value of an assignment
1136 to an integer parameter. Warning: This also affects implicit conversion
1137 to integer, for example as done by the let command. Never use unchecked
1138 user input, e.g. from the environment, in an arithmetic context!
1139 Expressions are calculated using signed arithmetic and the mksh_ari_t
1141 type (a 32-bit signed integer), unless they begin with a sole ‘#’ charac‐
1142 ter, in which case they use mksh_uari_t (a 32-bit unsigned integer).
1143 Expressions may contain alpha-numeric parameter identifiers, array refer‐
1145 ences and integer constants and may be combined with the following C
1146 operators (listed and grouped in increasing order of precedence):
1147 Unary operators:
1149 + - ! ~ ++ --
1151 Binary operators:
1153 ,
1155 = += -= *= /= %= <<= >>= ^<= ^>= &= ^= |=
1156 ||
1157 &&
1158 |
1159 ^
1160 &
1161 == !=
1162 < <= > >=
1163 << >> ^< ^>
1164 + -
1165 * / %
1166 Ternary operators:
1168 ?: (precedence is immediately higher than assignment)
1170 Grouping operators:
1172 ( )
1174 Integer constants and expressions are calculated using an exactly 32-bit
1176 wide, signed or unsigned, type with silent wraparound on integer over‐
1177 flow. Integer constants may be specified with arbitrary bases using the
1178 notation base#number, where base is a decimal integer specifying the base
1179 (up to 36), and number is a number in the specified base. Additionally,
1180 base-16 integers may be specified by prefixing them with “0x”
1181 (case-insensitive) in all forms of arithmetic expressions, except as
1182 numeric arguments to the test built-in utility. Prefixing numbers with a
1183 sole digit zero (“0”) does not cause interpretation as octal (except in
1184 POSIX mode, as required by the standard), as that's unsafe to do.
1185 As a special mksh extension, numbers to the base of one are treated as
1187 either (8-bit transparent) ASCII or Universal Coded Character Set code‐
1188 points, depending on the shell's utf8-mode flag (current setting). The
1189 AT&T UNIX ksh93 syntax of “'x'” instead of “1#x” is also supported. Note
1190 that NUL bytes (integral value of zero) cannot be used. An unset or
1191 empty parameter evaluates to 0 in integer context. If ‘x’ isn't com‐
1192 prised of exactly one valid character, the behaviour is undefined (usu‐
1193 ally, the shell aborts with a parse error, but rarely, it succeeds, e.g.
1194 on the sequence C2 20); users of this feature (as opposed to read -a)
1195 must validate the input first. See CAVEATS for UTF-8 mode handling.
1196 The operators are evaluated as follows:
1198 unary +
1200 Result is the argument (included for completeness).
1201 unary -
1203 Negation.
1204 ! Logical NOT; the result is 1 if argument is zero, 0 if not.
1206 ~ Arithmetic (bit-wise) NOT.
1208 ++ Increment; must be applied to a parameter (not a literal or
1210 other expression). The parameter is incremented by 1.
1211 When used as a prefix operator, the result is the incre‐
1212 mented value of the parameter; when used as a postfix oper‐
1213 ator, the result is the original value of the parameter.
1214 -- Similar to ++, except the parameter is decremented by 1.
1216 , Separates two arithmetic expressions; the left-hand side is
1218 evaluated first, then the right. The result is the value
1219 of the expression on the right-hand side.
1220 = Assignment; the variable on the left is set to the value on
1222 the right.
1223 += -= *= /= %= <<= >>= ^<= ^>= &= ^= |=
1225 Assignment operators. <var><op>=<expr> is the same as
1226 <var>=<var><op><expr>, with any operator precedence in
1227 <expr> preserved. For example, “var1 *= 5 + 3” is the same
1228 as specifying “var1 = var1 * (5 + 3)”.
1229 || Logical OR; the result is 1 if either argument is non-zero,
1231 0 if not. The right argument is evaluated only if the left
1232 argument is zero.
1233 && Logical AND; the result is 1 if both arguments are non-
1235 zero, 0 if not. The right argument is evaluated only if
1236 the left argument is non-zero.
1237 | Arithmetic (bit-wise) OR.
1239 ^ Arithmetic (bit-wise) XOR (exclusive-OR).
1241 & Arithmetic (bit-wise) AND.
1243 == Equal; the result is 1 if both arguments are equal, 0 if
1245 not.
1246 != Not equal; the result is 0 if both arguments are equal, 1
1248 if not.
1249 < Less than; the result is 1 if the left argument is less
1251 than the right, 0 if not.
1252 <= > >=
1254 Less than or equal, greater than, greater than or equal.
1255 See <.
1256 << >> Shift left (right); the result is the left argument with
1258 its bits arithmetically (signed operation) or logically
1259 (unsigned expression) shifted left (right) by the amount
1260 given in the right argument.
1261 ^< ^> Rotate left (right); the result is similar to shift, except
1263 that the bits shifted out at one end are shifted in at the
1264 other end, instead of zero or sign bits.
1265 + - * /
1267 Addition, subtraction, multiplication and division.
1268 % Remainder; the result is the symmetric remainder of the
1270 division of the left argument by the right. To get the
1271 mathematical modulus of “a mod b”, use the formula “(a % b
1272 + b) % b”.
1273 <arg1>?<arg2>:<arg3>
1275 If <arg1> is non-zero, the result is <arg2>; otherwise the
1276 result is <arg3>. The non-result argument is not evalu‐
1277 ated.
1278 Co-processes
1280 A co-process (which is a pipeline created with the “|&” operator) is an
1281 asynchronous process that the shell can both write to (using print -p)
1282 and read from (using read -p). The input and output of the co-process
1283 can also be manipulated using >&p and <&p redirections, respectively.
1284 Once a co-process has been started, another can't be started until the
1285 co-process exits, or until the co-process's input has been redirected
1286 using an exec n>&p redirection. If a co-process's input is redirected in
1287 this way, the next co-process to be started will share the output with
1288 the first co-process, unless the output of the initial co-process has
1289 been redirected using an exec n<&p redirection.
1290 Some notes concerning co-processes:
1292 · The only way to close the co-process's input (so the co-process reads
1294 an end-of-file) is to redirect the input to a numbered file descrip‐
1295 tor and then close that file descriptor: exec 3>&p; exec 3>&-
1296 · In order for co-processes to share a common output, the shell must
1298 keep the write portion of the output pipe open. This means that end-
1299 of-file will not be detected until all co-processes sharing the co-
1300 process's output have exited (when they all exit, the shell closes
1301 its copy of the pipe). This can be avoided by redirecting the output
1302 to a numbered file descriptor (as this also causes the shell to close
1303 its copy). Note that this behaviour is slightly different from the
1304 original Korn shell which closes its copy of the write portion of the
1305 co-process output when the most recently started co-process (instead
1306 of when all sharing co-processes) exits.
1307 · print -p will ignore SIGPIPE signals during writes if the signal is
1309 not being trapped or ignored; the same is true if the co-process
1310 input has been duplicated to another file descriptor and print -un is
1311 used.
1312 Functions
1314 Functions are defined using either Korn shell function function-name syn‐
1315 tax or the Bourne/POSIX shell function-name() syntax (see below for the
1316 difference between the two forms). Functions are like .‐scripts (i.e.
1317 scripts sourced using the “.” built-in) in that they are executed in the
1318 current environment. However, unlike .‐scripts, shell arguments (i.e.
1319 positional parameters $1, $2, etc.) are never visible inside them. When
1320 the shell is determining the location of a command, functions are
1321 searched after special built-in commands, before builtins and the PATH is
1322 searched.
1323 An existing function may be deleted using unset -f function-name. A list
1325 of functions can be obtained using typeset +f and the function defini‐
1326 tions can be listed using typeset -f. The autoload command (which is an
1327 alias for typeset -fu) may be used to create undefined functions: when an
1328 undefined function is executed, the shell searches the path specified in
1329 the FPATH parameter for a file with the same name as the function which,
1330 if found, is read and executed. If after executing the file the named
1331 function is found to be defined, the function is executed; otherwise, the
1332 normal command search is continued (i.e. the shell searches the regular
1333 built-in command table and PATH). Note that if a command is not found
1334 using PATH, an attempt is made to autoload a function using FPATH (this
1335 is an undocumented feature of the original Korn shell).
1336 Functions can have two attributes, “trace” and “export”, which can be set
1338 with typeset -ft and typeset -fx, respectively. When a traced function
1339 is executed, the shell's xtrace option is turned on for the function's
1340 duration. The “export” attribute of functions is currently not used.
1341 Since functions are executed in the current shell environment, parameter
1343 assignments made inside functions are visible after the function com‐
1344 pletes. If this is not the desired effect, the typeset command can be
1345 used inside a function to create a local parameter. Note that AT&T UNIX
1346 ksh93 uses static scoping (one global scope, one local scope per func‐
1347 tion) and allows local variables only on Korn style functions, whereas
1348 mksh uses dynamic scoping (nested scopes of varying locality). Note that
1349 special parameters (e.g. $$, $!) can't be scoped in this way.
1350 The exit status of a function is that of the last command executed in the
1352 function. A function can be made to finish immediately using the return
1353 command; this may also be used to explicitly specify the exit status.
1354 Note that when called in a subshell, return will only exit that subshell
1355 and will not cause the original shell to exit a running function (see the
1356 while...read loop FAQ).
1357 Functions defined with the function reserved word are treated differently
1359 in the following ways from functions defined with the () notation:
1360 · The $0 parameter is set to the name of the function (Bourne-style
1362 functions leave $0 untouched).
1363 · OPTIND is saved/reset and restored on entry and exit from the func‐
1365 tion so getopts can be used properly both inside and outside the
1366 function (Bourne-style functions leave OPTIND untouched, so using
1367 getopts inside a function interferes with using getopts outside the
1368 function).
1369 · Shell options (set -o) have local scope, i.e. changes inside a func‐
1371 tion are reset upon its exit.
1372 In the future, the following differences may also be added:
1374 · A separate trap/signal environment will be used during the execution
1376 of functions. This will mean that traps set inside a function will
1377 not affect the shell's traps and signals that are not ignored in the
1378 shell (but may be trapped) will have their default effect in a func‐
1379 tion.
1380 · The EXIT trap, if set in a function, will be executed after the func‐
1382 tion returns.
1383 Command execution
1385 After evaluation of command-line arguments, redirections and parameter
1386 assignments, the type of command is determined: a special built-in com‐
1387 mand, a function, a normal builtin or the name of a file to execute found
1388 using the PATH parameter. The checks are made in the above order. Spe‐
1389 cial built-in commands differ from other commands in that the PATH param‐
1390 eter is not used to find them, an error during their execution can cause
1391 a non-interactive shell to exit, and parameter assignments that are spec‐
1392 ified before the command are kept after the command completes. Regular
1393 built-in commands are different only in that the PATH parameter is not
1394 used to find them.
1395 POSIX special built-in utilities:
1397 ., :, break, continue, eval, exec, exit, export, readonly, return, set,
1399 shift, times, trap, unset
1400 Additional mksh commands keeping assignments:
1402 source, typeset
1404 All other builtins are not special; these are at least:
1406 [, alias, bg, bind, builtin, cat, cd, command, echo, false, fc, fg,
1408 getopts, jobs, kill, let, print, pwd, read, realpath, rename, sleep,
1409 suspend, test, true, ulimit, umask, unalias, wait, whence
1410 Once the type of command has been determined, any command-line parameter
1412 assignments are performed and exported for the duration of the command.
1413 The following describes the special and regular built-in commands and
1415 builtin-like reserved words, as well as some optional utilities:
1416 . file [arg ...]
1418 (keeps assignments, special) This is called the “dot” command.
1419 Execute the commands in file in the current environment. The file
1420 is searched for in the directories of PATH. If arguments are
1421 given, the positional parameters may be used to access them while
1422 file is being executed. If no arguments are given, the positional
1423 parameters are those of the environment the command is used in.
1424 : [...]
1426 (keeps assignments, special) The null command.
1427 Exit status is set to zero.
1428 Lb64decode [string]
1430 (dot.mkshrc function) Decode string or standard input to binary.
1431 Lb64encode [string]
1433 (dot.mkshrc function) Encode string or standard input as base64.
1434 Lbafh_init
1436 Lbafh_add [string]
1437 Lbafh_finish
1438 (dot.mkshrc functions) Implement the Better Avalance for the Jenk‐
1439 ins Hash. This is the same hash mksh currently uses internally.
1440 After calling Lbafh_init, call Lbafh_add multiple times until all
1441 input is read, then call Lbafh_finish, which writes the result to
1442 the unsigned integer Lbafh_v variable for your consumption.
1443 Lstripcom [file ...]
1445 (dot.mkshrc function) Same as cat but strips any empty lines and
1446 comments (from any ‘#’ character onwards, no escapes) and reduces
1447 any amount of whitespace to one space character.
1448 [ expression ]
1450 (regular) See test.
1451 alias [-d | -t [-r] | -+x] [-p] [+] [name [=value] ...]
1453 (regular) Without arguments, alias lists all aliases. For any
1454 name without a value, the existing alias is listed. Any name with
1455 a value defines an alias; see Aliases above.
1456 [][A-Za-z0-9_!%+,.@:-] are valid in names, except they may not
1457 begin with a plus or hyphen-minus, and [[ is not a valid alias
1458 name.
1459 When listing aliases, one of two formats is used. Normally,
1461 aliases are listed as name=value, where value is quoted as neces‐
1462 sary. If options were preceded with ‘+’, or a lone ‘+’ is given
1463 on the command line, only name is printed.
1464 The -d option causes directory aliases which are used in tilde
1466 expansion to be listed or set (see Tilde expansion above).
1467 With -p, each alias is listed with the string “alias ” prefixed.
1469 The -t option indicates that tracked aliases are to be listed/set
1471 (values given with the command are ignored for tracked aliases).
1472 The -r option indicates that all tracked aliases are to be reset.
1474 The -x option sets (+x clears) the export attribute of an alias,
1476 or, if no names are given, lists the aliases with the export
1477 attribute (exporting an alias has no effect).
1478 autoload
1480 (built-in alias) See Functions above.
1481 bg [job ...]
1483 (regular, needs job control) Resume the specified stopped job(s)
1484 in the background. If no jobs are specified, %+ is assumed. See
1485 Job control below for more information.
1486 bind -l
1488 (regular) The names of editing commands strings can be bound to
1489 are listed. See Emacs editing mode for more information.
1490 bind [string ...]
1492 The current bindings, for string, if given, else all, are listed.
1493 Note: Default prefix bindings (1=Esc, 2=^X, 3=NUL) assumed.
1494 bind string=[editing-command] [...]
1496 bind -m string=substitute [...]
1497 To string, which should consist of a control character optionally
1498 preceded by one of the three prefix characters and optionally suc‐
1499 ceeded by a tilde character, the editing-command is bound so that
1500 future input of the string will immediately invoke that editing
1501 command. If a tilde postfix is given, a tilde trailing the con‐
1502 trol character is ignored. If -m (macro) is given, future input
1503 of the string will be replaced by the given NUL-terminated
1504 substitute string, wherein prefix/control/tilde characters mapped
1505 to editing commands (but not those mapped to other macros) will be
1506 processed.
1507 Prefix and control characters may be written using caret notation,
1509 i.e. ^Z represents Ctrl-Z. Use a backslash to escape the caret,
1510 an equals sign or another backslash. Note that, although only
1511 three prefix characters (usually Esc, ^X and NUL) are supported,
1512 some multi-character sequences can be supported.
1513 break [level]
1515 (keeps assignments, special) Exit the levelth inner-most for,
1516 select, until or while loop. level defaults to 1.
1517 builtin [--] command [arg ...]
1519 (regular) Execute the built-in command command.
1520 \builtin command [arg ...]
1522 (regular, decl-forwarder) Same as builtin. Additionally acts as
1523 declaration utility forwarder, i.e. this is a declaration utility
1524 (see Tilde expansion) iff command is a declaration utility.
1525 cat [-u] [file ...]
1527 (defer with flags) Copy files in command line order to standard
1528 output. If a file is a single dash (“-”) or absent, read from
1529 standard input. For direct builtin calls, the POSIX -u option is
1530 supported as a no-op. For calls from shell, if any options are
1531 given, an external cat(1) utility is preferred over the builtin.
1532 cd [-L] [dir]
1534 cd -P [-e] [dir]
1535 chdir [-eLP] [dir]
1536 (regular) Set the working directory to dir. If the parameter
1537 CDPATH is set, it lists the search path for the directory contain‐
1538 ing dir. An unset or empty path means the current directory. If
1539 dir is found in any component of the CDPATH search path other than
1540 an unset or empty path, the name of the new working directory will
1541 be written to standard output. If dir is missing, the home direc‐
1542 tory HOME is used. If dir is “-”, the previous working directory
1543 is used (see the OLDPWD parameter).
1544 If the -L option (logical path) is used or if the physical option
1546 isn't set (see the set command below), references to “..” in dir
1547 are relative to the path used to get to the directory. If the -P
1548 option (physical path) is used or if the physical option is set,
1549 “..” is relative to the filesystem directory tree. The PWD and
1550 OLDPWD parameters are updated to reflect the current and old work‐
1551 ing directory, respectively. If the -e option is set for physical
1552 filesystem traversal and PWD could not be set, the exit code is 1;
1553 greater than 1 if an error occurred, 0 otherwise.
1554 cd [-eLP] old new
1556 chdir [-eLP] old new
1557 (regular) The string new is substituted for old in the current
1558 directory, and the shell attempts to change to the new directory.
1559 cls (dot.mkshrc alias) Reinitialise the display (hard reset).
1561 command [-pVv] cmd [arg ...]
1563 (regular, decl-forwarder) If neither the -v nor -V option is
1564 given, cmd is executed exactly as if command had not been speci‐
1565 fied, with two exceptions: firstly, cmd cannot be a shell func‐
1566 tion; and secondly, special built-in commands lose their special‐
1567 ness (i.e. redirection and utility errors do not cause the shell
1568 to exit, and command assignments are not permanent).
1569 If the -p option is given, a default search path, whose actual
1571 value is system-dependent, is used instead of the current PATH.
1572 If the -v option is given, instead of executing cmd, information
1574 about what would be executed is given for each argument. For
1575 builtins, functions and keywords, their names are simply printed;
1576 for aliases, a command that defines them is printed; for utilities
1577 found by searching the PATH parameter, the full path of the com‐
1578 mand is printed. If no command is found (i.e. the path search
1579 fails), nothing is printed and command exits with a non-zero sta‐
1580 tus. The -V option is like the -v option, but more verbose.
1581 continue [level]
1583 (keeps assignments, special) Jumps to the beginning of the levelth
1584 inner-most for, select, until or while loop. level defaults to 1.
1585 dirs [-lnv]
1587 (dot.mkshrc function) Print the directory stack. -l causes tilde
1588 expansion to occur in the output. -n causes line wrapping before
1589 80 columns, whereas -v causes numbered vertical output.
1590 doch (dot.mkshrc alias) Execute the last command with sudo(8).
1592 echo [-Een] [arg ...]
1594 (regular) Warning: this utility is not portable; use the standard
1595 Korn shell built-in utility print in new code instead.
1596 Print arguments, separated by spaces, followed by a newline, to
1598 standard output. The newline is suppressed if any of the argu‐
1599 ments contain the backslash sequence “\c”. See the print command
1600 below for a list of other backslash sequences that are recognised.
1601 The options are provided for compatibility with BSD shell scripts.
1603 The -E option suppresses backslash interpretation, -e enables it
1604 (normally default), -n suppresses the trailing newline, and any‐
1605 thing else causes the word to be printed as argument instead.
1606 If the posix or sh option is set or this is a direct builtin call
1608 or print -R, only the first argument is treated as an option, and
1609 only if it is exactly “-n”. Backslash interpretation is disabled.
1610 enable [-anps] [name ...]
1612 (dot.mkshrc function) Hide and unhide built-in utilities, aliases
1613 and functions and those defined in dot.mkshrc.
1614 If no name is given or the -p option is used, builtins are printed
1616 (behind the string “enable ”, followed by “-n ” if the builtin is
1617 currently disabled), otherwise, they are disabled (if -n is given)
1618 or re-enabled.
1619 When printing, only enabled builtins are printed by default; the
1621 -a options prints all builtins, while -n prints only disabled
1622 builtins instead; -s limits the list to POSIX special builtins.
1623 eval command ...
1625 (keeps assignments, special) The arguments are concatenated, with
1626 a space between each, to form a single string which the shell then
1627 parses and executes in the current execution environment.
1628 exec [-a argv0] [-c] [command [arg ...]]
1630 (keeps assignments, special) The command (with arguments) is exe‐
1631 cuted without forking, fully replacing the shell process; this is
1632 absolute, i.e. exec never returns, even if the command is not
1633 found. The -a option permits setting a different argv[0] value,
1634 and -c clears the environment before executing the child process,
1635 except for the _ parameter and direct assignments.
1636 If no command is given except for I/O redirection, the I/O redi‐
1638 rection is permanent and the shell is not replaced. Any file
1639 descriptors greater than 2 which are opened or dup(2)'d in this
1640 way are not made available to other executed commands (i.e. com‐
1641 mands that are not built-in to the shell). Note that the Bourne
1642 shell differs here; it does pass these file descriptors on.
1643 exit [status]
1645 (keeps assignments, special) The shell or subshell exits with the
1646 specified errorlevel (or the current value of the $? parameter).
1647 export [-p] [parameter[=value]]
1649 (keeps assignments, special, decl-util) Sets the export attribute
1650 of the named parameters. Exported parameters are passed in the
1651 environment to executed commands. If values are specified, the
1652 named parameters are also assigned. This is a declaration util‐
1653 ity.
1654 If no parameters are specified, all parameters with the export
1656 attribute set are printed one per line: either their names, or, if
1657 a “-” with no option letter is specified, name=value pairs, or,
1658 with the -p option, export commands suitable for re-entry.
1659 extproc
1661 (OS/2) Null command required for shebang-like functionality.
1662 false (regular) A command that exits with a non-zero status.
1664 fc [-e editor | -l [-n]] [-r] [first [last]]
1666 (regular) first and last select commands from the history. Com‐
1667 mands can be selected by history number (negative numbers go back‐
1668 wards from the current, most recent, line) or a string specifying
1669 the most recent command starting with that string. The -l option
1670 lists the command on standard output, and -n inhibits the default
1671 command numbers. The -r option reverses the order of the list.
1672 Without -l, the selected commands are edited by the editor speci‐
1673 fied with the -e option or, if no -e is specified, the editor
1674 specified by the FCEDIT parameter (if this parameter is not set,
1675 /bin/ed is used), and the result is executed by the shell.
1676 fc -e - | -s [-g] [old=new] [prefix]
1678 (regular) Re-execute the selected command (the previous command by
1679 default) after performing the optional substitution of old with
1680 new. If -g is specified, all occurrences of old are replaced with
1681 new. The meaning of -e - and -s is identical: re-execute the
1682 selected command without invoking an editor. This command is usu‐
1683 ally accessed with the predefined: alias r='fc -e -'
1684 fg [job ...]
1686 (regular, needs job control) Resume the specified job(s) in the
1687 foreground. If no jobs are specified, %+ is assumed.
1688 See Job control below for more information.
1689 functions [name ...]
1691 (built-in alias) Display the function definition commands corre‐
1692 sponding to the listed, or all defined, functions.
1693 getopts optstring name [arg ...]
1695 (regular) Used by shell procedures to parse the specified argu‐
1696 ments (or positional parameters, if no arguments are given) and to
1697 check for legal options. Options that do not take arguments may
1698 be grouped in a single argument. If an option takes an argument
1699 and the option character is not the last character of the word it
1700 is found in, the remainder of the word is taken to be the option's
1701 argument; otherwise, the next word is the option's argument.
1702 optstring contains the option letters to be recognised. If a let‐
1704 ter is followed by a colon, the option takes an argument.
1705 Each time getopts is invoked, it places the next option in the
1707 shell parameter name. If the option was introduced with a ‘+’,
1708 the character placed in name is prefixed with a ‘+’. If the
1709 option takes an argument, it is placed in the shell parameter
1710 OPTARG.
1711 When an illegal option or a missing option argument is encoun‐
1713 tered, a question mark or a colon is placed in name (indicating an
1714 illegal option or missing argument, respectively) and OPTARG is
1715 set to the option letter that caused the problem. Furthermore,
1716 unless optstring begins with a colon, a question mark is placed in
1717 name, OPTARG is unset and a diagnostic is shown on standard error.
1718 getopts records the index of the argument to be processed by the
1720 next call in OPTIND. When the end of the options is encountered,
1721 getopts returns a non-zero exit status. Options end at the first
1722 argument that does not start with a ‘-’ (non-option argument) or
1723 when a “--” argument is encountered.
1724 Option parsing can be reset by setting OPTIND to 1 (this is done
1726 automatically whenever the shell or a shell procedure is invoked).
1727 Warning: Changing the value of the shell parameter OPTIND to a
1729 value other than 1 or parsing different sets of arguments without
1730 resetting OPTIND may lead to unexpected results.
1731 hash [-r] [name ...]
1733 (built-in alias) Without arguments, any hashed executable command
1734 paths are listed. The -r option causes all hashed commands to be
1735 removed from the cache. Each name is searched as if it were a
1736 command name and added to the cache if it is an executable com‐
1737 mand.
1738 hd [file ...]
1740 (dot.mkshrc alias or function) Hexdump stdin or arguments legibly.
1741 history [-nr] [first [last]]
1743 (built-in alias) Same as fc -l (see above).
1744 integer [flags] [name [=value] ...]
1746 (built-in alias) Same as typeset -i (see below).
1747 jobs [-lnp] [job ...]
1749 (regular) Display information about the specified job(s); if no
1750 jobs are specified, all jobs are displayed. The -n option causes
1751 information to be displayed only for jobs that have changed state
1752 since the last notification. If the -l option is used, the
1753 process ID of each process in a job is also listed. The -p option
1754 causes only the process group of each job to be printed. See Job
1755 control below for the format of job and the displayed job.
1756 kill [-s signame | -signum | -signame] { job | pid | pgrp } ...
1758 (regular) Send the specified signal to the specified jobs, process
1759 IDs or process groups. If no signal is specified, the TERM signal
1760 is sent. If a job is specified, the signal is sent to the job's
1761 process group. See Job control below for the format of job.
1762 kill -l [exit-status ...]
1764 (regular) Print the signal name corresponding to exit-status. If
1765 no arguments are specified, a list of all the signals with their
1766 numbers and a short description of each are printed.
1767 let [expression ...]
1769 (regular) Each expression is evaluated (see Arithmetic expressions
1770 above). If all expressions evaluate successfully, the exit status
1771 is 0 (1) if the last expression evaluated to non-zero (zero). If
1772 an error occurs during the parsing or evaluation of an expression,
1773 the exit status is greater than 1. Since expressions may need to
1774 be quoted, (( expr )) is syntactic sugar for:
1775 { \\builtin let 'expr'; }
1776 local [flags] [name [=value] ...]
1778 (built-in alias) Same as typeset (see below).
1779 mknod [-m mode] name b|c major minor
1781 mknod [-m mode] name p
1782 (optional) Create a device special file. The file type may be one
1783 of b (block type device), c (character type device) or p (named
1784 pipe, FIFO). The file created may be modified according to its
1785 mode (via the -m option), major (major device number), and minor
1786 (minor device number). This is not normally part of mksh; how‐
1787 ever, distributors may have added this as builtin as a speed hack.
1788 nameref [flags] [name [=value] ...]
1790 (built-in alias) Same as typeset -n (see below).
1791 popd [-lnv] [+n]
1793 (dot.mkshrc function) Pops the directory stack and returns to the
1794 new top directory. The flags are as in dirs (see above). A
1795 numeric argument +n selects the entry in the stack to discard.
1796 print [-AcelNnprsu[n] | -R [-n]] [argument ...]
1798 (regular) Print the specified argument(s) on the standard output,
1799 separated by spaces, terminated with a newline. The escapes men‐
1800 tioned in Backslash expansion above, as well as “\c”, which is
1801 equivalent to using the -n option, are interpreted.
1802 The options are as follows:
1804 -A Each argument is arithmetically evaluated; the character
1806 corresponding to the resulting value is printed. Empty
1807 arguments separate input words.
1808 -c The output is printed columnised, line by line, similar to
1810 how the rs(1) utility, tab completion, the kill -l built-in
1811 utility and the select statement do.
1812 -e Restore backslash expansion after a previous -r.
1814 -l Change the output word separator to newline.
1816 -N Change the output word and line separator to ASCII NUL.
1818 -n Do not print the trailing line separator.
1820 -p Print to the co-process (see Co-processes above).
1822 -r Inhibit backslash expansion.
1824 -s Print to the history file instead of standard output.
1826 -u[n] Print to the file descriptor n (defaults to 1 if omitted)
1828 instead of standard output.
1829 The -R option mostly emulates the BSD echo(1) command which does
1831 not expand backslashes and interprets its first argument as option
1832 only if it is exactly “-n” (to suppress the trailing newline).
1833 printf format [arguments ...]
1835 (optional, defer always) If compiled in, format and print the
1836 arguments, supporting the bare POSIX-mandated minimum. If an
1837 external utility of the same name is found, it is deferred to,
1838 unless run as direct builtin call or from the builtin utility.
1839 pushd [-lnv]
1841 (dot.mkshrc function) Rotate the top two elements of the directory
1842 stack. The options are the same as for dirs (see above), and
1843 pushd changes to the topmost directory stack entry after acting.
1844 pushd [-lnv] +n
1846 (dot.mkshrc function) Rotate the element number n to the top.
1847 pushd [-lnv] name
1849 (dot.mkshrc function) Push name on top of the stack.
1850 pwd [-LP]
1852 (regular) Print the present working directory. If no options are
1853 given, pwd behaves as if the -P option (print physical path) was
1854 used if the physical shell option is set, the -L option (print
1855 logical path) otherwise. The logical path is the path used to cd
1856 to the current directory; the physical path is determined from the
1857 filesystem (by following “..” directories to the root directory).
1858 r [-g] [old=new] [prefix]
1860 (built-in alias) Same as fc -e - (see above).
1861 read [-A | -a] [-d x] [-N z | -n z] [-p | -u[n]] [-t n] [-rs] [p ...]
1863 (regular) Reads a line of input, separates the input into fields
1864 using the IFS parameter (see Substitution above) or other speci‐
1865 fied means, and assigns each field to the specified parameters p.
1866 If no parameters are specified, the REPLY parameter is used to
1867 store the result. If there are more parameters than fields, the
1868 extra parameters are set to the empty string or 0; if there are
1869 more fields than parameters, the last parameter is assigned the
1870 remaining fields (including the word separators).
1871 The options are as follows:
1873 -A Store the result into the parameter p (or REPLY) as array
1875 of words. Only no or one parameter is accepted.
1876 -a Store the result, without applying IFS word splitting, into
1878 the parameter p (or REPLY) as array of characters (wide
1879 characters if the utf8-mode option is enacted, octets oth‐
1880 erwise); the codepoints are encoded as decimal numbers by
1881 default. Only no or one parameter is accepted.
1882 -d x Use the first byte of x, NUL if empty, instead of the ASCII
1884 newline character to delimit input lines.
1885 -N z Instead of reading till end-of-line, read exactly z bytes.
1887 Upon EOF, a partial read is returned with exit status 1.
1888 After timeout, a partial read is returned with an exit sta‐
1889 tus as if SIGALRM were caught.
1890 -n z Instead of reading till end-of-line, read up to z bytes but
1892 return as soon as any bytes are read, e.g. from a slow ter‐
1893 minal device, or if EOF or a timeout occurs.
1894 -p Read from the currently active co-process (see Co-processes
1896 above for details) instead of from a file descriptor.
1897 -u[n] Read from the file descriptor number n (defaults to 0, i.e.
1899 standard input).
1900 The argument must immediately follow the option character.
1901 -t n Interrupt reading after n seconds (specified as positive
1903 decimal value with an optional fractional part). The exit
1904 status of read is the same as if SIGALRM were caught if the
1905 timeout occurred, but partial reads may still be returned.
1906 -r Normally, read strips backslash-newline sequences and any
1908 remaining backslashes from input. This option enables raw
1909 mode, in which backslashes are retained and ignored.
1910 -s The input line is saved to the history.
1912 If the input is a terminal, both the -N and -n options set it into
1914 raw mode; they read an entire file if -1 is passed as z argument.
1915 The first parameter may have a question mark and a string appended
1917 to it, in which case the string is used as a prompt (printed to
1918 standard error before any input is read) if the input is a tty(4)
1919 (e.g. read nfoo?'number of foos: ').
1920 If no input is read or a timeout occurred, read exits with a non-
1922 zero status.
1923 readonly [-p] [parameter [=value] ...]
1925 (keeps assignments, special, decl-util) Sets the read-only
1926 attribute of the named parameters. If values are given, parame‐
1927 ters are assigned these before disallowing writes. Once a parame‐
1928 ter is made read-only, it cannot be unset and its value cannot be
1929 changed.
1930 If no parameters are specified, the names of all parameters with
1932 the read-only attribute are printed one per line, unless the -p
1933 option is used, in which case readonly commands defining all read-
1934 only parameters, including their values, are printed.
1935 realpath [--] name
1937 (defer with flags) Resolves an absolute pathname corresponding to
1938 name. If the resolved pathname either exists or can be created
1939 immediately, realpath returns 0 and prints the resolved pathname,
1940 otherwise or if an error occurs, it issues a diagnostic and
1941 returns nonzero. If name ends with a slash (‘/’), resolving to an
1942 extant non-directory is also treated as error.
1943 rename [--] from to
1945 (defer always) Renames the file from to to. Both must be complete
1946 pathnames and on the same device. Intended for emergency situa‐
1947 tions (where /bin/mv becomes unusable); directly calls rename(2).
1948 return [status]
1950 (keeps assignments, special) Returns from a function or . script
1951 with errorlevel status. If no status is given, the exit status of
1952 the last executed command is used. If used outside of a function
1953 or . script, it has the same effect as exit. Note that mksh
1954 treats both profile and ENV files as . scripts, while the original
1955 Korn shell only treated profiles as . scripts.
1956 rot13 (dot.mkshrc alias) ROT13-encrypts/-decrypts stdin to stdout.
1958 set [-+abCefhiklmnprsUuvXx] [-+o option] [-+A name] [--] [arg ...]
1960 (keeps assignments, special) The set command can be used to show
1961 all shell parameters (like typeset -), set (-) or clear (+) shell
1962 options, set an array parameter or the positional parameters.
1963 Options can be changed using the -+o option syntax, where option
1965 is the long name of an option, or using the -+letter syntax, where
1966 letter is the option's single letter name (not all options have a
1967 single letter name). The following table lists short (if extant)
1968 and long names along with a description of what each option does:
1969 -A name
1971 Sets the elements of the array parameter name to arg ...
1972 If -A is used, the array is reset (i.e. emptied) first; if +A
1974 is used, the first N elements are set (where N is the number
1975 of arguments); the rest are left untouched. If name ends
1976 with a ‘+’, the array is appended to instead.
1977 An alternative syntax for the command set -A foo -- a b c;
1979 set -A foo+ -- d e which is compatible to GNU bash and also
1980 supported by AT&T UNIX ksh93 is: foo=(a b c); foo+=(d e)
1981 -a | -o allexport
1983 All new parameters are created with the export attribute.
1984 -b | -o notify
1986 Print job notification messages asynchronously instead of
1987 just before the prompt. Only used with job control (-m).
1988 -C | -o noclobber
1990 Prevent > redirection from overwriting existing files.
1991 Instead, >| must be used to force an overwrite. Note: This
1992 is not safe to use for creation of temporary files or lock‐
1993 files due to a TOCTOU in a check allowing one to redirect
1994 output to /dev/null or other device files even in noclobber
1995 mode.
1996 -e | -o errexit
1998 Exit (after executing the ERR trap) as soon as an error
1999 occurs or a command fails (i.e. exits with a non-zero sta‐
2000 tus). This does not apply to commands whose exit status is
2001 explicitly tested by a shell construct such as !, if, until
2002 or while statements. For &&, || and pipelines (but mind -o
2003 pipefail), only the status of the last command is tested.
2004 -f | -o noglob
2006 Do not expand file name patterns.
2007 -h | -o trackall
2009 Create tracked aliases for all executed commands (see Aliases
2010 above). Enabled by default for non-interactive shells.
2011 -i | -o interactive
2013 The shell is an interactive shell. This option can only be
2014 used when the shell is invoked. See above for details.
2015 -k | -o keyword
2017 Parameter assignments are recognised anywhere in a command.
2018 -l | -o login
2020 The shell is a login shell. This option can only be used
2021 when the shell is invoked. See above for what this means.
2022 -m | -o monitor
2024 Enable job control (default for interactive shells).
2025 -n | -o noexec
2027 Do not execute any commands. Useful for checking the syntax
2028 of scripts. Ignored if reading commands from a tty.
2029 -p | -o privileged
2031 The shell is a privileged shell. It is set automatically if,
2032 when the shell starts, the real UID or GID does not match the
2033 effective UID (EUID) or GID (EGID), respectively. See above
2034 for a description of what this means.
2035 If the shell is privileged, setting this flag after startup
2037 files have been processed let it go full setuid and/or set‐
2038 gid. Clearing this flag makes the shell drop privileges.
2039 Changing this flag resets the groups vector.
2040 -r | -o restricted
2042 The shell is a restricted shell. This option can only be
2043 used when the shell is invoked. See above for what this
2044 means.
2045 -s | -o stdin
2047 If used when the shell is invoked, commands are read from
2048 standard input. Set automatically if the shell is invoked
2049 with no arguments.
2050 When -s is used with the set command it causes the specified
2052 arguments to be sorted ASCIIbetically before assigning them
2053 to the positional parameters (or to array name, with -A).
2054 -U | -o utf8-mode
2056 Enable UTF-8 support in the Emacs editing mode and internal
2057 string handling functions. This flag is disabled by default,
2058 but can be enabled by setting it on the shell command line;
2059 is enabled automatically for interactive shells if requested
2060 at compile time, your system supports setlocale(LC_CTYPE, "")
2061 and optionally nl_langinfo(CODESET), or the LC_ALL, LC_CTYPE
2062 or LANG environment variables, and at least one of these
2063 returns something that matches “UTF-8” or “utf8” case-insen‐
2064 sitively; for direct builtin calls depending on the aforemen‐
2065 tioned environment variables; or for stdin or scripts, if the
2066 input begins with a UTF-8 Byte Order Mark.
2067 In near future, locale tracking will be implemented, which
2069 means that set -+U is changed whenever one of the POSIX
2070 locale-related environment variables changes.
2071 -u | -o nounset
2073 Referencing of an unset parameter, other than “$@” or “$*”,
2074 is treated as an error, unless one of the ‘-’, ‘+’ or ‘=’
2075 modifiers is used.
2076 -v | -o verbose
2078 Write shell input to standard error as it is read.
2079 -X | -o markdirs
2081 Mark directories with a trailing ‘/’ during globbing.
2082 -x | -o xtrace
2084 Print commands when they are executed, preceded by PS4.
2085 -o bgnice
2087 Background jobs are run with lower priority.
2088 -o braceexpand
2090 Enable brace expansion. This is enabled by default.
2091 -o emacs
2093 Enable BRL emacs-like command-line editing (interactive
2094 shells only); see Emacs editing mode. Enabled by default.
2095 -o gmacs
2097 Enable gmacs-like command-line editing (interactive shells
2098 only). Currently identical to emacs editing except that
2099 transpose-chars (^T) acts slightly differently.
2100 -o ignoreeof
2102 The shell will not (easily) exit when end-of-file is read;
2103 exit must be used. To avoid infinite loops, the shell will
2104 exit if EOF is read 13 times in a row.
2105 -o inherit-xtrace
2107 Do not reset -o xtrace upon entering functions (default).
2108 -o nohup
2110 Do not kill running jobs with a SIGHUP signal when a login
2111 shell exits. Currently set by default, but this may change
2112 in the future to be compatible with AT&T UNIX ksh, which
2113 doesn't have this option, but does send the SIGHUP signal.
2114 -o nolog
2116 No effect. In the original Korn shell, this prevented func‐
2117 tion definitions from being stored in the history file.
2118 -o physical
2120 Causes the cd and pwd commands to use “physical” (i.e. the
2121 filesystem's) “..” directories instead of “logical” directo‐
2122 ries (i.e. the shell handles “..”, which allows the user to
2123 be oblivious of symbolic links to directories). Clear by
2124 default. Note that setting this option does not affect the
2125 current value of the PWD parameter; only the cd command
2126 changes PWD. See cd and pwd above for more details.
2127 -o pipefail
2129 Make the exit status of a pipeline the rightmost non-zero
2130 errorlevel, or zero if all commands exited with zero.
2131 -o posix
2133 Behave closer to the standards (see POSIX mode for details).
2134 Automatically enabled if the basename of the shell invocation
2135 begins with “sh” and this autodetection feature is compiled
2136 in (not in MirBSD; commonly used for lksh only). As a side
2137 effect, setting this flag turns off the braceexpand and
2138 utf8-mode flags, which can be turned back on manually, and
2139 (unless both are enabled at the same time) sh mode.
2140 -o sh
2142 Enable /bin/sh (kludge) mode (see SH mode). Automatically
2143 enabled if the basename of the shell invocation begins with
2144 “sh” and this autodetection feature is compiled in (rather
2145 uncommon). As a side effect, setting this flag turns off
2146 braceexpand mode, which can be turned back on manually, and
2147 posix mode (unless both are enabled at the same time).
2148 -o vi
2150 Enable vi(1)-like command-line editing (interactive shells
2151 only). See Vi editing mode for documentation and limita‐
2152 tions.
2153 -o vi-esccomplete
2155 In vi command-line editing, do command and file name comple‐
2156 tion when Esc (^[) is entered in command mode.
2157 -o vi-tabcomplete
2159 In vi command-line editing, do command and file name comple‐
2160 tion when Tab (^I) is entered in insert mode (default).
2161 -o viraw
2163 No effect. In the original Korn shell, unless viraw was set,
2164 the vi command-line mode would let the tty(4) driver do the
2165 work until Esc was entered. mksh is always in viraw mode.
2166 These options can also be used upon invocation of the shell. The
2168 current set of options (with single letter names) can be found in
2169 the parameter “$-”. set -o with no option name will list all the
2170 options and whether each is on or off; set +o will print the long
2171 names of all options that are currently on. In a future version,
2172 set +o will behave POSIX compliant and print commands to restore
2173 the current options instead.
2174 Remaining arguments, if any, are positional parameters and are
2176 assigned, in order, to the positional parameters (i.e. $1, $2,
2177 etc.). If options end with “--” and there are no remaining argu‐
2178 ments, all positional parameters are cleared. For unknown histor‐
2179 ical reasons, a lone “-” option is treated specially – it clears
2180 both the -v and -x options. If no options or arguments are given,
2181 the values of all parameters are printed (suitably quoted).
2182 setenv [name [value]]
2184 (dot.mkshrc function) Without arguments, display the names and
2185 values of all exported parameters. Otherwise, set name's export
2186 attribute, and its value to value (empty string if none given).
2187 shift [number]
2189 (keeps assignments, special) The positional parameters number+1,
2190 number+2, etc. (number defaults to 1) are renamed to 1, 2, etc.
2191 sleep seconds
2193 (regular, needs select(2)) Suspends execution for a minimum of the
2194 seconds (specified as positive decimal value with an optional
2195 fractional part). Signal delivery may continue execution earlier.
2196 smores [file ...]
2198 (dot.mkshrc function) Simple pager: <Enter> next; ‘q’+<Enter> quit
2199 source file [arg ...]
2201 (keeps assignments) Like . (“dot”), except that the current work‐
2202 ing directory is appended to the search path. (GNU bash
2203 extension)
2204 suspend
2206 (needs job control and getsid(2)) Stops the shell as if it had
2207 received the suspend character from the terminal.
2208 It is not possible to suspend a login shell unless the parent
2210 process is a member of the same terminal session but is a member
2211 of a different process group. As a general rule, if the shell was
2212 started by another shell or via su(1), it can be suspended.
2213 test expression
2215 [ expression ]
2216 (regular) test evaluates the expression and exits with status code
2217 0 if true, 1 if false, or greater than 1 if there was an error.
2218 It is often used as the condition command of if and while state‐
2219 ments. All file expressions, except -h and -L, follow symbolic
2220 links.
2221 The following basic expressions are available:
2223 -a file file exists.
2225 -b file file is a block special device.
2227 -c file file is a character special device.
2229 -d file file is a directory.
2231 -e file file exists.
2233 -f file file is a regular file.
2235 -G file file's group is the shell's effective group ID.
2237 -g file file's mode has the setgid bit set.
2239 -H file file is a context dependent directory (only
2241 useful on HP-UX).
2242 -h file file is a symbolic link.
2244 -k file file's mode has the sticky(7) bit set.
2246 -L file file is a symbolic link.
2248 -O file file's owner is the shell's effective user ID.
2250 -p file file is a named pipe (FIFO).
2252 -r file file exists and is readable.
2254 -S file file is a unix(4)-domain socket.
2256 -s file file is not empty.
2258 -t fd File descriptor fd is a tty(4) device.
2260 -u file file's mode has the setuid bit set.
2262 -w file file exists and is writable.
2264 -x file file exists and is executable.
2266 file1 -nt file2 file1 is newer than file2 or file1 exists and
2268 file2 does not.
2269 file1 -ot file2 file1 is older than file2 or file2 exists and
2271 file1 does not.
2272 file1 -ef file2 file1 is the same file as file2.
2274 string string has non-zero length.
2276 -n string string is not empty.
2278 -z string string is empty.
2280 -v name The shell parameter name is set.
2282 -o option Shell option is set (see the set command above
2284 for a list of options). As a non-standard
2285 extension, if the option starts with a ‘!’, the
2286 test is negated; the test always fails if
2287 option doesn't exist (so [ -o foo -o -o !foo ]
2288 returns true if and only if option foo exists).
2289 The same can be achieved with [ -o ?foo ] like
2290 in AT&T UNIX ksh93. option can also be the
2291 short flag prefixed with either ‘-’ or ‘+’ (no
2292 logical negation), for example “-x” or “+x”
2293 instead of “xtrace”.
2294 string = string Strings are equal. In double brackets, pattern
2296 matching (R59+ using extglobs) occurs if the
2297 right-hand string isn't quoted.
2298 string == string Same as ‘=’ (deprecated).
2300 string != string Strings are not equal. See ‘=’ regarding pat‐
2302 tern matching.
2303 string > string First string operand is greater than second
2305 string operand.
2306 string < string First string operand is less than second string
2308 operand.
2309 number -eq number Numbers compare equal.
2311 number -ne number Numbers compare not equal.
2313 number -ge number Numbers compare greater than or equal.
2315 number -gt number Numbers compare greater than.
2317 number -le number Numbers compare less than or equal.
2319 number -lt number Numbers compare less than.
2321 The above basic expressions, in which unary operators have prece‐
2323 dence over binary operators, may be combined with the following
2324 operators (listed in increasing order of precedence):
2325 expr -o expr Logical OR.
2327 expr -a expr Logical AND.
2328 ! expr Logical NOT.
2329 ( expr ) Grouping.
2330 Note that a number actually may be an arithmetic expression, such
2332 as a mathematical term or the name of an integer variable:
2333 x=1; [ "x" -eq 1 ] evaluates to true
2335 Note that some special rules are applied (courtesy of POSIX) if
2337 the number of arguments to test or inside the brackets [ ... ] is
2338 less than five: if leading “!” arguments can be stripped such that
2339 only one to three arguments remain, then the lowered comparison is
2340 executed; (thanks to XSI) parentheses \( ... \) lower four- and
2341 three-argument forms to two- and one-argument forms, respectively;
2342 three-argument forms ultimately prefer binary operations, followed
2343 by negation and parenthesis lowering; two- and four-argument forms
2344 prefer negation followed by parenthesis; the one-argument form
2345 always implies -n. To assume this is not necessarily portable.
2346 Note: A common mistake is to use “if [ $foo = bar ]” which fails
2348 if parameter “foo” is empty or unset, if it has embedded spaces
2349 (i.e. IFS octets) or if it is a unary operator like “!” or “-n”.
2350 Use tests like “if [ x"$foo" = x"bar" ]” instead, or the double-
2351 bracket operator (see [[ above): “if [[ $foo = bar ]]” or, to
2352 avoid pattern matching, “if [[ $foo = "$bar" ]]”; the [[ ... ]]
2353 construct is not only more secure to use but also often faster.
2354 time [-p] [pipeline]
2356 (reserved word) If a pipeline is given, the times used to execute
2357 the pipeline are reported. If no pipeline is given, then the user
2358 and system time used by the shell itself, and all the commands it
2359 has run since it was started, are reported.
2360 The times reported are the real time (elapsed time from start to
2362 finish), the user CPU time (time spent running in user mode), and
2363 the system CPU time (time spent running in kernel mode).
2364 Times are reported to standard error; the format of the output is:
2366 0m0.03s real 0m0.02s user 0m0.01s system
2368 If the -p option is given (which is only permitted if pipeline is
2370 a simple command), the output is slightly longer:
2371 real 0.03
2373 user 0.02
2374 sys 0.01
2375 Simple redirections of standard error do not affect time's output:
2377 $ time sleep 1 2>afile
2379 $ { time sleep 1; } 2>afile
2380 Times for the first command do not go to “afile”, but those of the
2382 second command do.
2383 times (keeps assignments, special) Print the accumulated user and system
2385 times (see above) used both by the shell and by processes that the
2386 shell started which have exited. The format of the output is:
2387 0m0.01s 0m0.00s
2389 0m0.04s 0m0.02s
2390 trap n [signal ...]
2392 (keeps assignments, special) If the first operand is a decimal
2393 unsigned integer, this resets all specified signals to the default
2394 action, i.e. is the same as calling trap with a dash (“-”) as
2395 handler, followed by the arguments (interpreted as signals).
2396 trap [handler signal ...]
2398 (keeps assignments, special) Sets a trap handler that is to be
2399 executed when any of the specified signals are received. handler
2400 is either an empty string, indicating the signals are to be
2401 ignored, a dash (“-”), indicating that the default action is to be
2402 taken for the signals (see signal(3)), or a string comprised of
2403 shell commands to be executed at the first opportunity (i.e. when
2404 the current command completes or before printing the next PS1
2405 prompt) after receipt of one of the signals. signal is the name,
2406 possibly prefixed with “SIG”, of a signal (e.g. PIPE, ALRM or
2407 SIGINT) or the number of the signal (see the kill -l command
2408 above).
2409 There are two special signals: EXIT (also known as 0), which is
2411 executed when the shell is about to exit, and ERR, which is exe‐
2412 cuted after an error occurs; an error is something that would
2413 cause the shell to exit if the set -e or set -o errexit option
2414 were set. EXIT handlers are executed in the environment of the
2415 last executed command. The original Korn shell's DEBUG trap and
2416 handling of ERR and EXIT in functions are not yet implemented.
2417 Note that, for non-interactive shells, the trap handler cannot be
2419 changed for signals that were ignored when the shell started.
2420 With no arguments, the current state of the traps that have been
2422 set since the shell started is shown as a series of trap commands.
2423 Note that the output of trap cannot be usefully captured or piped
2424 to another process (an artifact of the fact that traps are cleared
2425 when subprocesses are created).
2426 true (regular) A command that exits with a zero status.
2428 type name ...
2430 (built-in alias) Reveal how name would be interpreted as command.
2431 typeset [-+aglpnrtUux] [-L[n] | -R[n] | -Z[n]] [-i[n]] [name [=value]
2433 ...]
2434 typeset -f [-tux] [name ...]
2435 (keeps assignments, decl-util) Display or set attributes of shell
2436 parameters or functions. With no name arguments, parameter
2437 attributes are shown; if no options are used, the current
2438 attributes of all parameters are printed as typeset commands; if
2439 an option is given (or “-” with no option letter), all parameters
2440 and their values with the specified attributes are printed; if
2441 options are introduced with ‘+’ (or “+” alone), only names are
2442 printed.
2443 If any name arguments are given, the attributes of the so named
2445 parameters are set (-) or cleared (+); inside a function, this
2446 will cause the parameters to be created (and set to “” if no value
2447 is given) in the local scope (except if -g is used). Values for
2448 parameters may optionally be specified. For name[*], the change
2449 affects all elements of the array, and no value may be specified.
2450 When -f is used, typeset operates on the attributes of functions.
2452 As with parameters, if no name arguments are given, functions are
2453 listed with their values (i.e. definitions) unless options are
2454 introduced with ‘+’, in which case only the names are displayed.
2455 -a Indexed array attribute.
2457 -f Function mode. Display or set shell functions and their
2459 attributes, instead of shell parameters.
2460 -g “global” mode. Do not cause named parameters to be cre‐
2462 ated in the local scope when called inside a function.
2463 -i[n] Integer attribute. n specifies the base to use when
2465 stringifying the integer (if not specified, the base given
2466 in the first assignment is used). Parameters with this
2467 attribute may be assigned arithmetic expressions for val‐
2468 ues.
2469 -L[n] Left justify attribute. n specifies the field width. If
2471 n is not specified, the current width of the parameter (or
2472 the width of its first assigned value) is used. Leading
2473 whitespace (and digit zeros, if used with the -Z option)
2474 is stripped. If necessary, values are either truncated or
2475 padded with space to fit the field width.
2476 -l Lower case attribute. All upper case ASCII characters in
2478 values are converted to lower case. (In the original Korn
2479 shell, this parameter meant “long integer” when used with
2480 the -i option.)
2481 -n Create a bound variable (name reference): any access to
2483 the variable name will access the variable value in the
2484 current scope (this is different from AT&T UNIX ksh93!)
2485 instead. Also different from AT&T UNIX ksh93 is that
2486 value is lazily evaluated at the time name is accessed.
2487 This can be used by functions to access variables whose
2488 names are passed as parameters, instead of resorting to
2489 eval.
2490 -p Print complete typeset commands that can be used to re-
2492 create the attributes and values of parameters.
2493 -R[n] Right justify attribute. n specifies the field width. If
2495 n is not specified, the current width of the parameter (or
2496 the width of its first assigned value) is used. Trailing
2497 whitespace is stripped. If necessary, values are either
2498 stripped of leading characters or padded with space to fit
2499 the field width.
2500 -r Read-only attribute. Parameters with this attribute may
2502 not be assigned to or unset. Once this attribute is set,
2503 it cannot be turned off.
2504 -t Tag attribute. This attribute has no meaning to the shell
2506 for parameters and is provided for application use.
2507 For functions, -t is the trace attribute. When functions
2509 with the trace attribute are executed, the -o xtrace (-x)
2510 shell option is temporarily turned on.
2511 -U Unsigned integer attribute. Integers are printed as
2513 unsigned values (combined with the -i option).
2514 -u Upper case attribute. All lower case ASCII characters in
2516 values are converted to upper case. (In the original Korn
2517 shell, this parameter meant “unsigned integer” when used
2518 with the -i option which meant upper case letters would
2519 never be used for bases greater than 10. See -U above.)
2520 For functions, -u is the undefined attribute, used with
2522 FPATH. See Functions above for the implications of this.
2523 -x Export attribute. Parameters are placed in the environ‐
2525 ment of any executed commands. Functions cannot be
2526 exported for security reasons (“shellshock”).
2527 -Z[n] Zero fill attribute. If not combined with -L, this is the
2529 same as -R, except zero padding is used instead of space
2530 padding. For integers, the number is padded, not the
2531 base.
2532 If any of the -i, -L, -l, -R, -U, -u or -Z options are changed,
2534 all others from this set are cleared, unless they are also given
2535 on the same command line.
2536 ulimit [-aBCcdefHilMmnOPpqrSsTtVvwx] [value]
2538 (regular) Display or set process limits. If no options are used,
2539 the file size limit (-f) is assumed. value, if specified, may be
2540 either an arithmetic expression or the word “unlimited”. The lim‐
2541 its affect the shell and any processes created by the shell after
2542 a limit is imposed. Note that systems may not allow some limits
2543 to be increased once they are set. Also note that the types of
2544 limits available are system dependent – some systems have only the
2545 -f limit, or not even that, or can set only the soft limits, etc.
2546 -a Display all limits (soft limits unless -H is used).
2548 -B n Set the socket buffer size to n kibibytes.
2550 -C n Set the number of cached threads to n.
2552 -c n Impose a size limit of n blocks on the size of core dumps.
2554 -d n Limit the size of the data area to n kibibytes.
2556 -e n Set the maximum niceness to n.
2558 -f n Impose a size limit of n blocks on files written by the
2560 shell and its child processes (any size may be read).
2561 -H Set the hard limit only (the default is to set both hard
2563 and soft limits). With -a, display all hard limits.
2564 -i n Set the number of pending signals to n.
2566 -l n Impose a limit of n kibibytes on the amount of locked
2568 (wired) physical memory.
2569 -M n Set the AIO locked memory to n kibibytes.
2571 -m n Impose a limit of n kibibytes on the amount of physical
2573 memory used.
2574 -n n Impose a limit of n file descriptors that can be open at
2576 once.
2577 -O n Set the number of AIO operations to n.
2579 -P n Limit the number of threads per process to n.
2581 This option mostly matches AT&T UNIX ksh93's -T;
2583 on AIX, see -r as used by its ksh though.
2584 -p n Impose a limit of n processes that can be run by the user
2586 (uid) at any one time.
2587 -q n Limit the size of POSIX message queues to n bytes.
2589 -r n (AIX) Limit the number of threads per process to n.
2591 (Linux) Set the maximum real-time priority to n.
2592 -S Set the soft limit only (the default is to set both hard
2594 and soft limits). With -a, display soft limits (default).
2595 -s n Limit the size of the stack area to n kibibytes.
2597 -T n Impose a time limit of n real seconds (“humantime”) to be
2599 used by each process.
2600 -t n Impose a time limit of n CPU seconds spent in user mode to
2602 be used by each process.
2603 -V n Set the number of vnode monitors on Haiku to n.
2605 -v n Impose a limit of n kibibytes on the amount of virtual mem‐
2607 ory (address space) used.
2608 -w n Limit the amount of swap space used to at most n kibibytes.
2610 -x n Set the maximum number of file locks to n.
2612 As far as ulimit is concerned, a block is 512 bytes.
2614 umask [-S] [mask]
2616 (regular) Display or set the file permission creation mask or
2617 umask (see umask(2)). If the -S option is used, the mask dis‐
2618 played or set is symbolic; otherwise, it is an octal number.
2619 Symbolic masks are like those used by chmod(1). When used, they
2621 describe what permissions may be made available (as opposed to
2622 octal masks in which a set bit means the corresponding bit is to
2623 be cleared). For example, “ug=rwx,o=” sets the mask so files will
2624 not be readable, writable or executable by “others”, and is equiv‐
2625 alent (on most systems) to the octal mask “007”.
2626 unalias [-adt] [name ...]
2628 (regular) The aliases for the given names are removed. If the -a
2629 option is used, all aliases are removed. If the -t or -d options
2630 are used, the indicated operations are carried out on tracked or
2631 directory aliases, respectively.
2632 unset [-fv] parameter ...
2634 (keeps assignments, special) Unset the named parameters (-v, the
2635 default) or functions (-f). With parameter[*], attributes are
2636 retained, only values are unset. The exit status is non-zero if
2637 any of the parameters are read-only, zero otherwise (not porta‐
2638 ble).
2639 wait [job ...]
2641 (regular) Wait for the specified job(s) to finish. The exit sta‐
2642 tus of wait is that of the last specified job; if the last job is
2643 killed by a signal, the exit status is 128 + the signal number
2644 (see kill -l exit-status above); if the last specified job cannot
2645 be found (because it never existed or had already finished), the
2646 exit status is 127. See Job control below for the format of job.
2647 wait will return if a signal for which a trap has been set is
2648 received or if a SIGHUP, SIGINT or SIGQUIT signal is received.
2649 If no jobs are specified, wait waits for all currently running
2651 jobs (if any) to finish and exits with a zero status. If job mon‐
2652 itoring is enabled, the completion status of jobs is printed (this
2653 is not the case when jobs are explicitly specified).
2654 whence [-pv] [name ...]
2656 (regular) Without the -v option, it is the same as command -v,
2657 except aliases are printed as their definition only. With the -v
2658 option, it is exactly identical to command -V. In either case,
2659 with the -p option the search is restricted to the (current) PATH.
2660 which [-a] [name ...]
2662 (dot.mkshrc function) Without -a, behaves like whence -p (does a
2663 PATH search for each name printing the resulting pathname if
2664 found); with -a, matches in all PATH components are printed, i.e.
2665 the search is not stopped after a match. If no name was matched,
2666 the exit status is 2; if every name was matched, it is zero, oth‐
2667 erwise it is 1. No diagnostics are produced on failure to match.
2668 Job control
2670 Job control refers to the shell's ability to monitor and control jobs
2671 which are processes or groups of processes created for commands or pipe‐
2672 lines. At a minimum, the shell keeps track of the status of the back‐
2673 ground (i.e. asynchronous) jobs that currently exist; this information
2674 can be displayed using the jobs commands. If job control is fully
2675 enabled (using set -m or set -o monitor), as it is for interactive
2676 shells, the processes of a job are placed in their own process group.
2677 Foreground jobs can be stopped by typing the suspend character from the
2678 terminal (normally ^Z); jobs can be restarted in either the foreground or
2679 background using the commands fg and bg.
2680 Note that only commands that create processes (e.g. asynchronous com‐
2682 mands, subshell commands and non-built-in, non-function commands) can be
2683 stopped; commands like read cannot be.
2684 When a job is created, it is assigned a job number. For interactive
2686 shells, this number is printed inside “[...]”, followed by the process
2687 IDs of the processes in the job when an asynchronous command is run. A
2688 job may be referred to in the bg, fg, jobs, kill and wait commands either
2689 by the process ID of the last process in the command pipeline (as stored
2690 in the $! parameter) or by prefixing the job number with a percent sign
2691 (‘%’). Other percent sequences can also be used to refer to jobs:
2692 %+ | %% | % The most recently stopped job or, if there are no stopped
2694 jobs, the oldest running job.
2695 %- The job that would be the %+ job if the latter did not
2697 exist.
2698 %n The job with job number n.
2700 %?string The job with its command containing the string string (an
2702 error occurs if multiple jobs are matched).
2703 %string The job with its command starting with the string string
2705 (an error occurs if multiple jobs are matched).
2706 When a job changes state (e.g. a background job finishes or foreground
2708 job is stopped), the shell prints the following status information:
2709 [number] flag status command
2711 where...
2713 number is the job number of the job;
2715 flag is the ‘+’ or ‘-’ character if the job is the %+ or %- job,
2717 respectively, or space if it is neither;
2718 status indicates the current state of the job and can be:
2720 Done [number]
2722 The job exited. number is the exit status of the job
2723 which is omitted if the status is zero.
2724 Running The job has neither stopped nor exited (note that
2726 running does not necessarily mean consuming CPU
2727 time – the process could be blocked waiting for some
2728 event).
2729 Stopped [signal]
2731 The job was stopped by the indicated signal (if no
2732 signal is given, the job was stopped by SIGTSTP).
2733 signal-description [“core dumped”]
2735 The job was killed by a signal (e.g. memory fault,
2736 hangup); use kill -l for a list of signal descrip‐
2737 tions. The “core dumped” message indicates the
2738 process created a core file.
2739 command is the command that created the process. If there are multiple
2741 processes in the job, each process will have a line showing its
2742 command and possibly its status, if it is different from the
2743 status of the previous process.
2744 When an attempt is made to exit the shell while there are jobs in the
2746 stopped state, the shell warns the user that there are stopped jobs and
2747 does not exit. If another attempt is immediately made to exit the shell,
2748 the stopped jobs are sent a SIGHUP signal and the shell exits. Simi‐
2749 larly, if the nohup option is not set and there are running jobs when an
2750 attempt is made to exit a login shell, the shell warns the user and does
2751 not exit. If another attempt is immediately made to exit the shell, the
2752 running jobs are sent a SIGHUP signal and the shell exits.
2753 Terminal state
2755 The state of the controlling terminal can be modified by a command exe‐
2756 cuted in the foreground, whether or not job control is enabled, but the
2757 modified terminal state is only kept past the job's lifetime and used for
2758 later command invocations if the command exits successfully (i.e. with an
2759 exit status of 0). When such a job is momentarily stopped or restarted,
2760 the terminal state is saved and restored, respectively, but it will not
2761 be kept afterwards. In interactive mode, when line editing is enabled,
2762 the terminal state is saved before being reconfigured by the shell for
2763 the line editor, then restored before running a command.
2764 POSIX mode
2766 Entering set -o posix mode will cause mksh to behave even more POSIX com‐
2767 pliant in places where the defaults or opinions differ. Note that mksh
2768 will still operate with unsigned 32-bit arithmetic; use lksh if arith‐
2769 metic on the host long data type, complete with ISO C Undefined Behav‐
2770 iour, is required; refer to the lksh(1) manual page for details. Most
2771 other historic, AT&T UNIX ksh-compatible or opinionated differences can
2772 be disabled by using this mode; these are:
2773 · The incompatible GNU bash I/O redirection &>file is not supported.
2775 · File descriptors created by I/O redirections are inherited by child
2777 processes.
2778 · Numbers with a leading digit zero are interpreted as octal.
2780 · The echo builtin does not interpret backslashes and only supports the
2782 exact option -n.
2783 · Alias expansion with a trailing space only reruns on command words.
2785 · Tilde expansion follows POSIX instead of Korn shell rules.
2787 · The exit status of fg is always 0.
2789 · kill -l only lists signal names, all in one line.
2791 · getopts does not accept options with a leading ‘+’.
2793 · exec skips builtins, functions and other commands and uses a PATH
2795 search to determine the utility to execute.
2796 SH mode
2798 Compatibility mode; intended for use with legacy scripts that cannot eas‐
2799 ily be fixed; the changes are as follows:
2800 · The incompatible GNU bash I/O redirection &>file is not supported.
2802 · File descriptors created by I/O redirections are inherited by child
2804 processes.
2805 · The echo builtin does not interpret backslashes and only supports the
2807 exact option -n, unless built with -DMKSH_MIDNIGHTBSD01ASH_COMPAT.
2808 · The substitution operations ${x#pat}, ${x##pat}, ${x%pat}, and
2810 ${x%%pat} wrongly do not require a parenthesis to be escaped and do
2811 not parse extglobs.
2812 · The getopt construct from lksh(1) passes through the errorlevel.
2814 · sh -c eats a leading -- if built with -DMKSH_MIDNIGHTBSD01ASH_COMPAT.
2816 Interactive input line editing
2818 The shell supports three modes of reading command lines from a tty(4) in
2819 an interactive session, controlled by the emacs, gmacs and vi options (at
2820 most one of these can be set at once). The default is emacs. Editing
2821 modes can be set explicitly using the set built-in. If none of these
2822 options are enabled, the shell simply reads lines using the normal tty(4)
2823 driver. If the emacs or gmacs option is set, the shell allows emacs-like
2824 editing of the command; similarly, if the vi option is set, the shell
2825 allows vi-like editing of the command. These modes are described in
2826 detail in the following sections.
2827 In these editing modes, if a line is longer than the screen width (see
2829 the COLUMNS parameter), a ‘>’, ‘+’ or ‘<’ character is displayed in the
2830 last column indicating that there are more characters after, before and
2831 after, or before the current position, respectively. The line is
2832 scrolled horizontally as necessary.
2833 Completed lines are pushed into the history, unless they begin with an
2835 IFS octet or IFS white space or are the same as the previous line.
2836 Emacs editing mode
2838 When the emacs option is set, interactive input line editing is enabled.
2839 Warning: This mode is slightly different from the emacs mode in the orig‐
2840 inal Korn shell. In this mode, various editing commands (typically bound
2841 to one or more control characters) cause immediate actions without wait‐
2842 ing for a newline. Several editing commands are bound to particular con‐
2843 trol characters when the shell is invoked; these bindings can be changed
2844 using the bind command.
2845 The following is a list of available editing commands. Each description
2847 starts with the name of the command, suffixed with a colon; an [n] (if
2848 the command can be prefixed with a count); and any keys the command is
2849 bound to by default, written using caret notation e.g. the ASCII Esc
2850 character is written as ^[. These control sequences are not case sensi‐
2851 tive. A count prefix for a command is entered using the sequence ^[n,
2852 where n is a sequence of 1 or more digits. Unless otherwise specified,
2853 if a count is omitted, it defaults to 1.
2854 Note that editing command names are used only with the bind command.
2856 Furthermore, many editing commands are useful only on terminals with a
2857 visible cursor. The user's tty(4) characters (e.g. ERASE) are bound to
2858 reasonable substitutes and override the default bindings; their customary
2859 values are shown in parentheses below. The default bindings were chosen
2860 to resemble corresponding Emacs key bindings:
2861 abort: INTR (^C), ^G
2863 Abort the current command, save it to the history, empty the line
2864 buffer and set the exit state to interrupted.
2865 auto-insert: [n]
2867 Simply causes the character to appear as literal input. Most
2868 ordinary characters are bound to this.
2869 backward-char: [n] ^B, ^XD, ANSI-CurLeft, PC-CurLeft
2871 Moves the cursor backward n characters.
2872 backward-word: [n] ^[b, ANSI-Ctrl-CurLeft, ANSI-Alt-CurLeft
2874 Moves the cursor backward to the beginning of the word; words
2875 consist of alphanumerics, underscore (‘_’) and dollar sign (‘$’)
2876 characters.
2877 beginning-of-history: ^[<
2879 Moves to the beginning of the history.
2880 beginning-of-line: ^A, ANSI-Home, PC-Home
2882 Moves the cursor to the beginning of the edited input line.
2883 capitalise-word: [n] ^[C, ^[c
2885 Uppercase the first ASCII character in the next n words, leaving
2886 the cursor past the end of the last word.
2887 clear-screen: ^[^L
2889 Prints a compile-time configurable sequence to clear the screen
2890 and home the cursor, redraws the last line of the prompt string
2891 and the currently edited input line. The default sequence works
2892 for almost all standard terminals.
2893 comment: ^[#
2895 If the current line does not begin with a comment character, one
2896 is added at the beginning of the line and the line is entered (as
2897 if return had been pressed); otherwise, the existing comment
2898 characters are removed and the cursor is placed at the beginning
2899 of the line.
2900 complete: ^[^[
2902 Automatically completes as much as is unique of the command name
2903 or the file name containing the cursor. If the entire remaining
2904 command or file name is unique, a space is printed after its com‐
2905 pletion, unless it is a directory name in which case ‘/’ is
2906 appended. If there is no command or file name with the current
2907 partial word as its prefix, a bell character is output (usually
2908 causing a beep to be sounded).
2909 complete-command: ^X^[
2911 Automatically completes as much as is unique of the command name
2912 having the partial word up to the cursor as its prefix, as in the
2913 complete command above.
2914 complete-file: ^[^X
2916 Automatically completes as much as is unique of the file name
2917 having the partial word up to the cursor as its prefix, as in the
2918 complete command described above.
2919 complete-list: ^I, ^[=
2921 Complete as much as is possible of the current word and list the
2922 possible completions for it. If only one completion is possible,
2923 match as in the complete command above. Note that ^I is usually
2924 generated by the Tab (tabulator) key.
2925 delete-char-backward: [n] ERASE (^H), ^?, ^H
2927 Deletes n characters before the cursor.
2928 delete-char-forward: [n] ANSI-Del, PC-Del
2930 Deletes n characters after the cursor.
2931 delete-word-backward: [n] Pfx1+ERASE (^[^H), WERASE (^W), ^[^?, ^[^H, ^[h
2933 Deletes n words before the cursor.
2934 delete-word-forward: [n] ^[d
2936 Deletes characters after the cursor up to the end of n words.
2937 down-history: [n] ^N, ^XB, ANSI-CurDown, PC-CurDown
2939 Scrolls the history buffer forward n lines (later). Each input
2940 line originally starts just after the last entry in the history
2941 buffer, so down-history is not useful until either
2942 search-history, search-history-up or up-history has been per‐
2943 formed.
2944 downcase-word: [n] ^[L, ^[l
2946 Lowercases the next n words.
2947 edit-line: [n] ^Xe
2949 Edit line n or the current line, if not specified, interactively.
2950 The actual command executed is fc -e ${VISUAL:-${EDITOR:-vi}} n.
2951 end-of-history: ^[>
2953 Moves to the end of the history.
2954 end-of-line: ^E, ANSI-End, PC-End
2956 Moves the cursor to the end of the input line.
2957 eot: ^_
2959 Acts as an end-of-file; this is useful because edit-mode input
2960 disables normal terminal input canonicalisation.
2961 eot-or-delete: [n] EOF (^D)
2963 If alone on a line, same as eot, otherwise, delete-char-forward.
2964 error: (not bound)
2966 Error (ring the bell).
2967 evaluate-region: ^[^E
2969 Evaluates the text between the mark and the cursor position (the
2970 entire line if no mark is set) as function substitution (if it
2971 cannot be parsed, the editing state is unchanged and the bell is
2972 rung to signal an error); $? is updated accordingly.
2973 exchange-point-and-mark: ^X^X
2975 Places the cursor where the mark is and sets the mark to where
2976 the cursor was.
2977 expand-file: ^[*
2979 Appends a ‘*’ to the current word and replaces the word with the
2980 result of performing file globbing on the word. If no files
2981 match the pattern, the bell is rung.
2982 forward-char: [n] ^F, ^XC, ANSI-CurRight, PC-CurRight
2984 Moves the cursor forward n characters.
2985 forward-word: [n] ^[f, ANSI-Ctrl-CurRight, ANSI-Alt-CurRight
2987 Moves the cursor forward to the end of the nth word.
2988 goto-history: [n] ^[g
2990 Goes to history number n.
2991 kill-line: KILL (^U)
2993 Deletes the entire input line.
2994 kill-region: ^W
2996 Deletes the input between the cursor and the mark.
2997 kill-to-eol: [n] ^K
2999 Deletes the input from the cursor to the end of the line if n is
3000 not specified; otherwise deletes characters between the cursor
3001 and column n.
3002 list: ^[?
3004 Prints a sorted, columnated list of command names or file names
3005 (if any) that can complete the partial word containing the cur‐
3006 sor. Directory names have ‘/’ appended to them.
3007 list-command: ^X?
3009 Prints a sorted, columnated list of command names (if any) that
3010 can complete the partial word containing the cursor.
3011 list-file: ^X^Y
3013 Prints a sorted, columnated list of file names (if any) that can
3014 complete the partial word containing the cursor. File type indi‐
3015 cators are appended as described under list above.
3016 newline: ^J, ^M
3018 Causes the current input line to be processed by the shell. The
3019 current cursor position may be anywhere on the line.
3020 newline-and-next: ^O
3022 Causes the current input line to be processed by the shell, and
3023 the next line from history becomes the current line. This is
3024 only useful after an up-history, search-history or
3025 search-history-up.
3026 no-op: QUIT (^\)
3028 This does nothing.
3029 prefix-1: ^[
3031 Introduces a 2-character command sequence.
3032 prefix-2: ^X, ^[[, ^[O
3034 Introduces a multi-character command sequence.
3035 prev-hist-word: [n] ^[., ^[_
3037 The last word or, if given, the nth word (zero-based) of the pre‐
3038 vious (on repeated execution, second-last, third-last, etc.) com‐
3039 mand is inserted at the cursor. Use of this editing command
3040 trashes the mark.
3041 quote: ^^, ^V
3043 The following character is taken literally rather than as an
3044 editing command.
3045 quote-region: ^[Q
3047 Escapes the text between the mark and the cursor position (the
3048 entire line if no mark is set) into a shell command argument.
3049 redraw: ^L
3051 Reprints the last line of the prompt string and the current input
3052 line on a new line.
3053 search-character-backward: [n] ^[^]
3055 Search backward in the current line for the nth occurrence of the
3056 next character typed.
3057 search-character-forward: [n] ^]
3059 Search forward in the current line for the nth occurrence of the
3060 next character typed.
3061 search-history: ^R
3063 Enter incremental search mode. The internal history list is
3064 searched backwards for commands matching the input. An initial
3065 ‘^’ in the search string anchors the search. The escape key will
3066 leave search mode. Other commands, including sequences of escape
3067 as prefix-1 followed by a prefix-1 or prefix-2 key will be exe‐
3068 cuted after leaving search mode. The abort (^G) command will
3069 restore the input line before search started. Successive
3070 search-history commands continue searching backward to the next
3071 previous occurrence of the pattern. The history buffer retains
3072 only a finite number of lines; the oldest are discarded as neces‐
3073 sary.
3074 search-history-up: ANSI-PgUp, PC-PgUp
3076 Search backwards through the history buffer for commands whose
3077 beginning match the portion of the input line before the cursor.
3078 When used on an empty line, this has the same effect as
3079 up-history.
3080 search-history-down: ANSI-PgDn, PC-PgDn
3082 Search forwards through the history buffer for commands whose
3083 beginning match the portion of the input line before the cursor.
3084 When used on an empty line, this has the same effect as
3085 down-history. This is only useful after an up-history,
3086 search-history or search-history-up.
3087 set-mark-command: ^[<space>
3089 Set the mark at the cursor position.
3090 transpose-chars: ^T
3092 If at the end of line or, if the gmacs option is set, this
3093 exchanges the two previous characters; otherwise, it exchanges
3094 the previous and current characters and moves the cursor one
3095 character to the right.
3096 up-history: [n] ^P, ^XA, ANSI-CurUp, PC-CurUp
3098 Scrolls the history buffer backward n lines (earlier).
3099 upcase-word: [n] ^[U, ^[u
3101 Uppercase the next n words.
3102 version: ^[^V
3104 Display the version of mksh. The current edit buffer is restored
3105 as soon as a key is pressed. The restoring keypress is pro‐
3106 cessed, unless it is a space.
3107 yank: ^Y
3109 Inserts the most recently killed text string at the current cur‐
3110 sor position.
3111 yank-pop: ^[y
3113 Immediately after a yank, replaces the inserted text string with
3114 the next previously killed text string.
3115 The tab completion escapes characters the same way as the following code:
3117 print -nr -- "${x@/[\"-\$\&-*:-?[\\\`\{-\}${IFS-$' \t\n'}]/\\$KSH_MATCH}"
3119 Vi editing mode
3121 Note: The vi command-line editing mode has not yet been brought up to the
3122 same quality and feature set as the emacs mode. It is 8-bit clean but
3123 specifically does not support UTF-8 or MBCS.
3124 The vi command-line editor in mksh has basically the same commands as the
3126 vi(1) editor with the following exceptions:
3127 · You start out in insert mode.
3129 · There are file name and command completion commands: =, \, *, ^X, ^E,
3131 ^F and, optionally, <Tab> and <Esc>.
3132 · The _ command is different (in mksh, it is the last argument command;
3134 in vi(1) it goes to the start of the current line).
3135 · The / and G commands move in the opposite direction to the j command.
3137 · Commands which don't make sense in a single line editor are not
3139 available (e.g. screen movement commands and ex(1)-style colon (:)
3140 commands).
3141 Like vi(1), there are two modes: “insert” mode and “command” mode. In
3143 insert mode, most characters are simply put in the buffer at the current
3144 cursor position as they are typed; however, some characters are treated
3145 specially. In particular, the following characters are taken from cur‐
3146 rent tty(4) settings (see stty(1)) and have their usual meaning (normal
3147 values are in parentheses): kill (^U), erase (^?), werase (^W), eof (^D),
3148 intr (^C) and quit (^\). In addition to the above, the following charac‐
3149 ters are also treated specially in insert mode:
3150 ^E Command and file name enumeration (see below).
3152 ^F Command and file name completion (see below). If used twice in
3154 a row, the list of possible completions is displayed; if used a
3155 third time, the completion is undone.
3156 ^H Erases previous character.
3158 ^J | ^M End of line. The current line is read, parsed and executed by
3160 the shell.
3161 ^V Literal next. The next character typed is not treated specially
3163 (can be used to insert the characters being described here).
3164 ^X Command and file name expansion (see below).
3166 <Esc> Puts the editor in command mode (see below).
3168 <Tab> Optional file name and command completion (see ^F above),
3170 enabled with set -o vi-tabcomplete.
3171 In command mode, each character is interpreted as a command. Characters
3173 that don't correspond to commands, are illegal combinations of commands,
3174 or are commands that can't be carried out, all cause beeps. In the fol‐
3175 lowing command descriptions, an [n] indicates the command may be prefixed
3176 by a number (e.g. 10l moves right 10 characters); if no number prefix is
3177 used, n is assumed to be 1 unless otherwise specified. The term “current
3178 position” refers to the position between the cursor and the character
3179 preceding the cursor. A “word” is a sequence of letters, digits and
3180 underscore characters or a sequence of non-letter, non-digit, non-under‐
3181 score and non-whitespace characters (e.g. “ab2*&^” contains two words)
3182 and a “big-word” is a sequence of non-whitespace characters.
3183 Special mksh vi commands:
3185 The following commands are not in, or are different from, the normal vi
3187 file editor:
3188 [n]_ Insert a space followed by the nth big-word from the last
3190 command in the history at the current position and enter
3191 insert mode; if n is not specified, the last word is
3192 inserted.
3193 # Insert the comment character (‘#’) at the start of the cur‐
3195 rent line and return the line to the shell (equivalent to
3196 I#^J).
3197 [n]g Like G, except if n is not specified, it goes to the most
3199 recent remembered line.
3200 [n]v Edit line n using the vi(1) editor; if n is not specified,
3202 the current line is edited. The actual command executed is
3203 fc -e ${VISUAL:-${EDITOR:-vi}} n.
3204 * and ^X Command or file name expansion is applied to the current big-
3206 word (with an appended ‘*’ if the word contains no file glob‐
3207 bing characters) – the big-word is replaced with the result‐
3208 ing words. If the current big-word is the first on the line
3209 or follows one of the characters ‘;’, ‘|’, ‘&’, ‘(’ or ‘)’
3210 and does not contain a slash (‘/’), then command expansion is
3211 done; otherwise file name expansion is done. Command expan‐
3212 sion will match the big-word against all aliases, functions
3213 and built-in commands as well as any executable files found
3214 by searching the directories in the PATH parameter. File
3215 name expansion matches the big-word against the files in the
3216 current directory. After expansion, the cursor is placed
3217 just past the last word and the editor is in insert mode.
3218 [n]\, [n]^F, [n]<Tab>, and [n]<Esc>
3220 Command/file name completion. Replace the current big-word
3221 with the longest unique match obtained after performing com‐
3222 mand and file name expansion. <Tab> is only recognised if
3223 the vi-tabcomplete option is set, while <Esc> is only recog‐
3224 nised if the vi-esccomplete option is set (see set -o). If n
3225 is specified, the nth possible completion is selected (as
3226 reported by the command/file name enumeration command).
3227 = and ^E Command/file name enumeration. List all the commands or
3229 files that match the current big-word.
3230 ^V Display the version of mksh. The current edit buffer is
3232 restored as soon as a key is pressed. The restoring keypress
3233 is ignored.
3234 @c Macro expansion. Execute the commands found in the alias _c.
3236 Intra-line movement commands:
3238 [n]h and [n]^H
3240 Move left n characters.
3241 [n]l and [n]<space>
3243 Move right n characters.
3244 0 Move to column 0.
3246 ^ Move to the first non-whitespace character.
3248 [n]| Move to column n.
3250 $ Move to the last character.
3252 [n]b Move back n words.
3254 [n]B Move back n big-words.
3256 [n]e Move forward to the end of the word, n times.
3258 [n]E Move forward to the end of the big-word, n times.
3260 [n]w Move forward n words.
3262 [n]W Move forward n big-words.
3264 % Find match. The editor looks forward for the nearest parenthe‐
3266 sis, bracket or brace and then moves the cursor to the matching
3267 parenthesis, bracket or brace.
3268 [n]fc Move forward to the nth occurrence of the character c.
3270 [n]Fc Move backward to the nth occurrence of the character c.
3272 [n]tc Move forward to just before the nth occurrence of the character
3274 c.
3275 [n]Tc Move backward to just before the nth occurrence of the character
3277 c.
3278 [n]; Repeats the last f, F, t or T command.
3280 [n], Repeats the last f, F, t or T command, but moves in the opposite
3282 direction.
3283 Inter-line movement commands:
3285 [n]j, [n]+, and [n]^N
3287 Move to the nth next line in the history.
3288 [n]k, [n]-, and [n]^P
3290 Move to the nth previous line in the history.
3291 [n]G Move to line n in the history; if n is not specified, the number
3293 of the first remembered line is used.
3294 [n]g Like G, except if n is not specified, it goes to the most recent
3296 remembered line.
3297 [n]/string
3299 Search backward through the history for the nth line containing
3300 string; if string starts with ‘^’, the remainder of the string
3301 must appear at the start of the history line for it to match.
3302 [n]?string
3304 Same as /, except it searches forward through the history.
3305 [n]n Search for the nth occurrence of the last search string; the
3307 direction of the search is the same as the last search.
3308 [n]N Search for the nth occurrence of the last search string; the
3310 direction of the search is the opposite of the last search.
3311 ANSI-CurUp, PC-PgUp
3313 Take the characters from the beginning of the line to the current
3314 cursor position as search string and do a history search, back‐
3315 wards, for lines beginning with this string; keep the cursor
3316 position. This works only in insert mode and keeps it enabled.
3317 ANSI-CurDown, PC-PgDn
3319 Take the characters from the beginning of the line to the current
3320 cursor position as search string and do a history search, for‐
3321 wards, for lines beginning with this string; keep the cursor
3322 position. This works only in insert mode and keeps it enabled.
3323 Edit commands
3325 [n]a Append text n times; goes into insert mode just after the current
3327 position. The append is only replicated if command mode is re-
3328 entered i.e. <Esc> is used.
3329 [n]A Same as a, except it appends at the end of the line.
3331 [n]i Insert text n times; goes into insert mode at the current posi‐
3333 tion. The insertion is only replicated if command mode is re-
3334 entered i.e. <Esc> is used.
3335 [n]I Same as i, except the insertion is done just before the first
3337 non-blank character.
3338 [n]s Substitute the next n characters (i.e. delete the characters and
3340 go into insert mode).
3341 S Substitute whole line. All characters from the first non-blank
3343 character to the end of the line are deleted and insert mode is
3344 entered.
3345 [n]cmove-cmd
3347 Change from the current position to the position resulting from n
3348 move-cmds (i.e. delete the indicated region and go into insert
3349 mode); if move-cmd is c, the line starting from the first non-
3350 blank character is changed.
3351 C Change from the current position to the end of the line (i.e.
3353 delete to the end of the line and go into insert mode).
3354 [n]x Delete the next n characters.
3356 [n]X Delete the previous n characters.
3358 D Delete to the end of the line.
3360 [n]dmove-cmd
3362 Delete from the current position to the position resulting from n
3363 move-cmds; move-cmd is a movement command (see above) or d, in
3364 which case the current line is deleted.
3365 [n]rc Replace the next n characters with the character c.
3367 [n]R Replace. Enter insert mode but overwrite existing characters
3369 instead of inserting before existing characters. The replacement
3370 is repeated n times.
3371 [n]~ Change the case of the next n characters.
3373 [n]ymove-cmd
3375 Yank from the current position to the position resulting from n
3376 move-cmds into the yank buffer; if move-cmd is y, the whole line
3377 is yanked.
3378 Y Yank from the current position to the end of the line.
3380 [n]p Paste the contents of the yank buffer just after the current
3382 position, n times.
3383 [n]P Same as p, except the buffer is pasted at the current position.
3385 Miscellaneous vi commands
3387 ^J and ^M
3389 The current line is read, parsed and executed by the shell.
3390 ^L and ^R
3392 Redraw the current line.
3393 [n]. Redo the last edit command n times.
3395 u Undo the last edit command.
3397 U Undo all changes that have been made to the current line.
3399 PC Home, End, Del and cursor keys
3401 They move as expected, both in insert and command mode.
3402 intr and quit
3404 The interrupt and quit terminal characters cause the current line
3405 to be removed to the history and a new prompt to be printed.
3406
3408 ~/.mkshrc User mkshrc profile (non-privileged interactive
3409 shells); see Startup files. The location can be
3410 changed at compile time (e.g. for embedded systems);
3411 AOSP Android builds use /system/etc/mkshrc.
3412 ~/.profile User profile (non-privileged login shells); see
3413 Startup files near the top of this manual.
3414 /etc/profile System profile (login shells); see Startup files.
3415 /etc/shells Shell database.
3416 /etc/suid_profile Privileged shells' profile (sugid); see Startup files.
3417 Note: On Android, /system/etc/ contains the system and suid profile.
3419
3421 awk(1), cat(1), ed(1), getopt(1), lksh(1), sed(1), sh(1), stty(1),
3422 dup(2), execve(2), getgid(2), getuid(2), mknod(2), mkfifo(2), open(2),
3423 pipe(2), rename(2), wait(2), getopt(3), nl_langinfo(3), setlocale(3),
3424 signal(3), system(3), tty(4), shells(5), environ(7), script(7), utf-8(7),
3425 mknod(8)
3426 The FAQ at http://www.mirbsd.org/mksh-faq.htm or in the mksh.faq file.
3428 http://www.mirbsd.org/ksh-chan.htm
3430 Morris Bolsky, The KornShell Command and Programming Language, Prentice
3432 Hall PTR, xvi + 356 pages, 1989, ISBN 978-0-13-516972-8 (0-13-516972-0).
3433 Morris I. Bolsky and David G. Korn, The New KornShell Command and
3435 Programming Language (2nd Edition), Prentice Hall PTR, xvi + 400 pages,
3436 1995, ISBN 978-0-13-182700-4 (0-13-182700-6).
3437 Stephen G. Kochan and Patrick H. Wood, UNIX Shell Programming, Sams, 3rd
3439 Edition, xiii + 437 pages, 2003, ISBN 978-0-672-32490-1 (0-672-32490-3).
3440 IEEE Inc., IEEE Standard for Information Technology – Portable Operating
3442 System Interface (POSIX), IEEE Press, Part 2: Shell and Utilities,
3443 xvii + 1195 pages, 1993, ISBN 978-1-55937-255-8 (1-55937-255-9).
3444 Bill Rosenblatt, Learning the Korn Shell, O'Reilly, 360 pages, 1993, ISBN
3446 978-1-56592-054-5 (1-56592-054-6).
3447 Bill Rosenblatt and Arnold Robbins, Learning the Korn Shell, Second
3449 Edition, O'Reilly, 432 pages, 2002, ISBN 978-0-596-00195-7
3450 (0-596-00195-9).
3451 Barry Rosenberg, KornShell Programming Tutorial, Addison-Wesley
3453 Professional, xxi + 324 pages, 1991, ISBN 978-0-201-56324-5
3454 (0-201-56324-X).
3455
3457 The MirBSD Korn Shell is developed by mirabilos <m@mirbsd.org> as part of
3458 The MirOS Project. This shell is based on the public domain 7th edition
3459 Bourne shell clone by Charles Forsyth, who kindly agreed to, in countries
3460 where the Public Domain status of the work may not be valid, grant a
3461 copyright licence to the general public to deal in the work without
3462 restriction and permission to sublicence derivatives under the terms of
3463 any (OSI approved) Open Source licence, and parts of the BRL shell by
3464 Doug A. Gwyn, Doug Kingston, Ron Natalie, Arnold Robbins, Lou Salkind and
3465 others. The first release of pdksh was created by Eric Gisin, and it was
3466 subsequently maintained by John R. MacMillan, Simon J. Gerraty and
3467 Michael Rendell. The effort of several projects, such as Debian and
3468 OpenBSD, and other contributors including our users, to improve the shell
3469 is appreciated. See the documentation, website and source code (CVS) for
3470 details.
3471 mksh-os2 is developed by KO Myung-Hun <komh@chollian.net>.
3473 mksh-w32 is developed by Michael Langguth <lan@scalaris.com>.
3475 mksh/z/OS is contributed by Daniel Richard G. <skunk@iSKUNK.ORG>.
3477 The BSD daemon is Copyright © Marshall Kirk McKusick. The complete
3479 legalese is at: http://www.mirbsd.org/TaC-mksh.txt
3480
3482 mksh provides a consistent, clear interface normally. This may deviate
3483 from POSIX in historic or opinionated places. set -o posix (see POSIX
3484 mode for details) will make the shell more conformant, but mind the FAQ
3485 (see SEE ALSO), especially regarding locales. mksh (but not lksh) pro‐
3486 vides a consistent 32-bit integer arithmetic implementation, both signed
3487 and unsigned, with sign of the result of a remainder operation and wrap‐
3488 around defined, even (defying POSIX) on 36-bit and 64-bit systems.
3489 mksh currently uses OPTU-16 internally, which is the same as UTF-8 and
3491 CESU-8 with 0000..FFFD being valid codepoints; raw octets are mapped into
3492 the PUA range EF80..EFFF, which is assigned by CSUR for this purpose.
3493
3495 Suspending (using ^Z) pipelines like the one below will only suspend the
3496 currently running part of the pipeline; in this example, “fubar” is imme‐
3497 diately printed on suspension (but not later after an fg).
3498 $ /bin/sleep 666 && echo fubar
3500 The truncation process involved when changing HISTFILE does not free old
3502 history entries (leaks memory) and leaks old entries into the new history
3503 if their line numbers are not overwritten by same-number entries from the
3504 persistent history file; truncating the on-disc file to HISTSIZE lines
3505 has always been broken and prone to history file corruption when multiple
3506 shells are accessing the file; the rollover process for the in-memory
3507 portion of the history is slow, should use memmove(3).
3508 This document attempts to describe mksh R59 and up, compiled without any
3510 options impacting functionality, such as MKSH_SMALL, when not called as
3511 /bin/sh which, on some systems only, enables set -o posix or set -o sh
3512 automatically (whose behaviour differs across targets), for an operating
3513 environment supporting all of its advanced needs.
3514 Please report bugs in mksh to the public development mailing list at
3516 <miros-mksh@mirbsd.org> (please note the EU-DSGVO/GDPR notice on
3517 http://www.mirbsd.org/rss.htm#lists and in the SMTP banner!) or in the
3518 #!/bin/mksh (or #ksh) IRC channel at irc.freenode.net (Port 6697 SSL,
3519 6667 unencrypted), or at: https://launchpad.net/mksh
3520MirBSD April 14, 2020 MirBSD