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 see the FAQ at the end of this document.
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 real user ID (group ID). For further implications, see
51 Startup files. If the shell is privileged and this flag is
52 not explicitly set, the “privileged” option is cleared auto‐
53 matically after processing the startup files.
54 -r Restricted shell. A shell is “restricted” if this option is
56 used. The following restrictions come into effect after the
57 shell processes any profile and ENV files:
58 · The cd (and chdir) command is disabled.
60 · The SHELL, ENV and PATH parameters cannot be changed.
61 · Command names can't be specified with absolute or relative
62 paths.
63 · The -p option of the built-in command command can't be
64 used.
65 · Redirections that create files can't be used (i.e. “>”,
66 “>|”, “>>”, “<>”).
67 -s The shell reads commands from standard input; all non-option
69 arguments are positional parameters.
70 -T name Spawn mksh on the tty(4) device given. The paths name,
72 /dev/ttyCname and /dev/ttyname are attempted in order. Unless
73 name begins with an exclamation mark (‘!’), this is done in a
74 subshell and returns immediately. If name is a dash (‘-’),
75 detach from controlling terminal (daemonise) instead.
76 In addition to the above, the options described in the set built-in com‐
78 mand can also be used on the command line: both [-+abCefhkmnuvXx] and
79 [-+o option] can be used for single letter or long options, respectively.
80 If neither the -c nor the -s option is specified, the first non-option
82 argument specifies the name of a file the shell reads commands from. If
83 there are no non-option arguments, the shell reads commands from the
84 standard input. The name of the shell (i.e. the contents of $0) is
85 determined as follows: if the -c option is used and there is a non-option
86 argument, it is used as the name; if commands are being read from a file,
87 the file is used as the name; otherwise, the basename the shell was
88 called with (i.e. argv[0]) is used.
89 The exit status of the shell is 127 if the command file specified on the
91 command line could not be opened, or non-zero if a fatal syntax error
92 occurred during the execution of a script. In the absence of fatal
93 errors, the exit status is that of the last command executed, or zero if
94 no command is executed.
95 Startup files
97 For the actual location of these files, see FILES. A login shell pro‐
98 cesses the system profile first. A privileged shell then processes the
99 suid profile. A non-privileged login shell processes the user profile
100 next. A non-privileged interactive shell checks the value of the ENV
101 parameter after subjecting it to parameter, command, arithmetic and tilde
102 (‘~’) substitution; if unset or empty, the user mkshrc profile is pro‐
103 cessed; otherwise, if a file whose name is the substitution result
104 exists, it is processed; non-existence is silently ignored. A privileged
105 shell then drops privileges if neither was the -p option given on the
106 command line nor set during execution of the startup files.
107 Command syntax
109 The shell begins parsing its input by removing any backslash-newline com‐
110 binations, then breaking it into words. Words (which are sequences of
111 characters) are delimited by unquoted whitespace characters (space, tab
112 and newline) or meta-characters (‘<’, ‘>’, ‘|’, ‘;’, ‘(’, ‘)’ and ‘&’).
113 Aside from delimiting words, spaces and tabs are ignored, while newlines
114 usually delimit commands. The meta-characters are used in building the
115 following tokens: “<”, “<&”, “<<”, “<<<”, “>”, “>&”, “>>”, “&>”, etc. are
116 used to specify redirections (see Input/output redirection below); “|” is
117 used to create pipelines; “|&” is used to create co-processes (see
118 Co-processes below); “;” is used to separate commands; “&” is used to
119 create asynchronous pipelines; “&&” and “||” are used to specify condi‐
120 tional execution; “;;”, “;&” and “;|” are used in case statements; “((
121 ... ))” is used in arithmetic expressions; and lastly, “( ... )” is used
122 to create subshells.
123 Whitespace and meta-characters can be quoted individually using a back‐
125 slash (‘\’), or in groups using double (‘"’) or single (“'”) quotes.
126 Note that the following characters are also treated specially by the
127 shell and must be quoted if they are to represent themselves: ‘\’, ‘"’,
128 “'”, ‘#’, ‘$’, ‘`’, ‘~’, ‘{’, ‘}’, ‘*’, ‘?’ and ‘[’. The first three of
129 these are the above mentioned quoting characters (see Quoting below);
130 ‘#’, if used at the beginning of a word, introduces a comment – every‐
131 thing after the ‘#’ up to the nearest newline is ignored; ‘$’ is used to
132 introduce parameter, command and arithmetic substitutions (see
133 Substitution below); ‘`’ introduces an old-style command substitution
134 (see Substitution below); ‘~’ begins a directory expansion (see Tilde
135 expansion below); ‘{’ and ‘}’ delimit csh(1)-style alternations (see
136 Brace expansion below); and finally, ‘*’, ‘?’ and ‘[’ are used in file
137 name generation (see File name patterns below).
138 As words and tokens are parsed, the shell builds commands, of which there
140 are two basic types: simple-commands, typically programmes that are exe‐
141 cuted, and compound-commands, such as for and if statements, grouping
142 constructs and function definitions.
143 A simple-command consists of some combination of parameter assignments
145 (see Parameters below), input/output redirections (see Input/output
146 redirections below) and command words; the only restriction is that
147 parameter assignments come before any command words. The command words,
148 if any, define the command that is to be executed and its arguments. The
149 command may be a shell built-in command, a function or an external com‐
150 mand (i.e. a separate executable file that is located using the PATH
151 parameter; see Command execution below). Note that all command con‐
152 structs have an exit status: for external commands, this is related to
153 the status returned by wait(2) (if the command could not be found, the
154 exit status is 127; if it could not be executed, the exit status is 126);
155 the exit status of other command constructs (built-in commands, func‐
156 tions, compound-commands, pipelines, lists, etc.) are all well-defined
157 and are described where the construct is described. The exit status of a
158 command consisting only of parameter assignments is that of the last com‐
159 mand substitution performed during the parameter assignment or 0 if there
160 were no command substitutions.
161 Commands can be chained together using the “|” token to form pipelines,
163 in which the standard output of each command but the last is piped (see
164 pipe(2)) to the standard input of the following command. The exit status
165 of a pipeline is that of its last command, unless the pipefail option is
166 set (see there). All commands of a pipeline are executed in separate
167 subshells; this is allowed by POSIX but differs from both variants of
168 AT&T UNIX ksh, where all but the last command were executed in subshells;
169 see the read builtin's description for implications and workarounds. A
170 pipeline may be prefixed by the “!” reserved word which causes the exit
171 status of the pipeline to be logically complemented: if the original sta‐
172 tus was 0, the complemented status will be 1; if the original status was
173 not 0, the complemented status will be 0.
174 Lists of commands can be created by separating pipelines by any of the
176 following tokens: “&&”, “||”, “&”, “|&” and “;”. The first two are for
177 conditional execution: “cmd1 && cmd2” executes cmd2 only if the exit sta‐
178 tus of cmd1 is zero; “||” is the opposite – cmd2 is executed only if the
179 exit status of cmd1 is non-zero. “&&” and “||” have equal precedence
180 which is higher than that of “&”, “|&” and “;”, which also have equal
181 precedence. Note that the “&&” and “||” operators are
182 "left-associative". For example, both of these commands will print only
183 "bar":
184 $ false && echo foo || echo bar
186 $ true || echo foo && echo bar
187 The “&” token causes the preceding command to be executed asynchronously;
189 that is, the shell starts the command but does not wait for it to com‐
190 plete (the shell does keep track of the status of asynchronous commands;
191 see Job control below). When an asynchronous command is started when job
192 control is disabled (i.e. in most scripts), the command is started with
193 signals SIGINT and SIGQUIT ignored and with input redirected from
194 /dev/null (however, redirections specified in the asynchronous command
195 have precedence). The “|&” operator starts a co-process which is a spe‐
196 cial kind of asynchronous process (see Co-processes below). Note that a
197 command must follow the “&&” and “||” operators, while it need not follow
198 “&”, “|&” or “;”. The exit status of a list is that of the last command
199 executed, with the exception of asynchronous lists, for which the exit
200 status is 0.
201 Compound commands are created using the following reserved words. These
203 words are only recognised if they are unquoted and if they are used as
204 the first word of a command (i.e. they can't be preceded by parameter
205 assignments or redirections):
206 case else function then ! (
208 do esac if time [[ ((
209 done fi in until {
210 elif for select while }
211 In the following compound command descriptions, command lists (denoted as
213 list) that are followed by reserved words must end with a semicolon, a
214 newline or a (syntactically correct) reserved word. For example, the
215 following are all valid:
216 $ { echo foo; echo bar; }
218 $ { echo foo; echo bar<newline>}
219 $ { { echo foo; echo bar; } }
220 This is not valid:
222 $ { echo foo; echo bar }
224 (list)
226 Execute list in a subshell. There is no implicit way to pass envi‐
227 ronment changes from a subshell back to its parent.
228 { list; }
230 Compound construct; list is executed, but not in a subshell. Note
231 that “{” and “}” are reserved words, not meta-characters.
232 case word in [[(] pattern [| pattern] ...) list terminator] ... esac
234 The case statement attempts to match word against a specified
235 pattern; the list associated with the first successfully matched
236 pattern is executed. Patterns used in case statements are the same
237 as those used for file name patterns except that the restrictions
238 regarding ‘.’ and ‘/’ are dropped. Note that any unquoted space
239 before and after a pattern is stripped; any space within a pattern
240 must be quoted. Both the word and the patterns are subject to
241 parameter, command and arithmetic substitution, as well as tilde
242 substitution.
243 For historical reasons, open and close braces may be used instead
245 of in and esac e.g. case $foo { *) echo bar ;; }.
246 The list terminators are:
248 “;;” Terminate after the list.
250 “;&” Fall through into the next list.
252 “;|” Evaluate the remaining pattern-list tuples.
254 The exit status of a case statement is that of the executed list;
256 if no list is executed, the exit status is zero.
257 for name [in word ...]; do list; done
259 For each word in the specified word list, the parameter name is set
260 to the word and list is executed. If in is not used to specify a
261 word list, the positional parameters ($1, $2, etc.) are used
262 instead. For historical reasons, open and close braces may be used
263 instead of do and done e.g. for i; { echo $i; }. The exit status
264 of a for statement is the last exit status of list; if list is
265 never executed, the exit status is zero.
266 if list; then list; [elif list; then list;] ... [else list;] fi
268 If the exit status of the first list is zero, the second list is
269 executed; otherwise, the list following the elif, if any, is exe‐
270 cuted with similar consequences. If all the lists following the if
271 and elifs fail (i.e. exit with non-zero status), the list following
272 the else is executed. The exit status of an if statement is that
273 of non-conditional list that is executed; if no non-conditional
274 list is executed, the exit status is zero.
275 select name [in word ...]; do list; done
277 The select statement provides an automatic method of presenting the
278 user with a menu and selecting from it. An enumerated list of the
279 specified word(s) is printed on standard error, followed by a
280 prompt (PS3: normally “#? ”). A number corresponding to one of the
281 enumerated words is then read from standard input, name is set to
282 the selected word (or unset if the selection is not valid), REPLY
283 is set to what was read (leading/trailing space is stripped), and
284 list is executed. If a blank line (i.e. zero or more IFS octets)
285 is entered, the menu is reprinted without executing list.
286 When list completes, the enumerated list is printed if REPLY is
288 empty, the prompt is printed, and so on. This process continues
289 until an end-of-file is read, an interrupt is received, or a break
290 statement is executed inside the loop. If “in word ...” is omit‐
291 ted, the positional parameters are used (i.e. $1, $2, etc.). For
292 historical reasons, open and close braces may be used instead of do
293 and done e.g. select i; { echo $i; }. The exit status of a select
294 statement is zero if a break statement is used to exit the loop,
295 non-zero otherwise.
296 until list; do list; done
298 This works like while, except that the body is executed only while
299 the exit status of the first list is non-zero.
300 while list; do list; done
302 A while is a pre-checked loop. Its body is executed as often as
303 the exit status of the first list is zero. The exit status of a
304 while statement is the last exit status of the list in the body of
305 the loop; if the body is not executed, the exit status is zero.
306 function name { list; }
308 Defines the function name (see Functions below). Note that redi‐
309 rections specified after a function definition are performed when‐
310 ever the function is executed, not when the function definition is
311 executed.
312 name() command
314 Mostly the same as function (see Functions below). Whitespace
315 (space or tab) after name will be ignored most of the time.
316 function name() { list; }
318 The same as name() (bashism). The function keyword is ignored.
319 time [-p] [pipeline]
321 The Command execution section describes the time reserved word.
322 (( expression ))
324 The arithmetic expression expression is evaluated; equivalent to
325 “let "expression"” (see Arithmetic expressions and the let command,
326 below) in a compound construct.
327 [[ expression ]]
329 Similar to the test and [ ... ] commands (described later), with
330 the following exceptions:
331 · Field splitting and file name generation are not performed on
333 arguments.
334 · The -a (AND) and -o (OR) operators are replaced with “&&” and
336 “||”, respectively.
337 · Operators (e.g. “-f”, “=”, “!”) must be unquoted.
339 · Parameter, command and arithmetic substitutions are performed
341 as expressions are evaluated and lazy expression evaluation is
342 used for the “&&” and “||” operators. This means that in the
343 following statement, $(<foo) is evaluated if and only if the
344 file foo exists and is readable:
345 $ [[ -r foo && $(<foo) = b*r ]]
347 · The second operand of the “!=” and “=” expressions are a subset
349 of patterns (e.g. the comparison [[ foobar = f*r ]] succeeds).
350 This even works indirectly:
351 $ bar=foobar; baz='f*r'
353 $ [[ $bar = $baz ]]; echo $?
354 $ [[ $bar = "$baz" ]]; echo $?
355 Perhaps surprisingly, the first comparison succeeds, whereas
357 the second doesn't. This does not apply to all extglob
358 metacharacters, currently.
359 Quoting
361 Quoting is used to prevent the shell from treating characters or words
362 specially. There are three methods of quoting. First, ‘\’ quotes the
363 following character, unless it is at the end of a line, in which case
364 both the ‘\’ and the newline are stripped. Second, a single quote (“'”)
365 quotes everything up to the next single quote (this may span lines).
366 Third, a double quote (‘"’) quotes all characters, except ‘$’, ‘\’ and
367 ‘`’, up to the next unescaped double quote. ‘$’ and ‘`’ inside double
368 quotes have their usual meaning (i.e. parameter, arithmetic or command
369 substitution) except no field splitting is carried out on the results of
370 double-quoted substitutions, and the old-style form of command substitu‐
371 tion has backslash-quoting for double quotes enabled. If a ‘\’ inside a
372 double-quoted string is followed by ‘"’, ‘$’, ‘\’ or ‘`’, only the ‘\’ is
373 removed, i.e. the combination is replaced by the second character; if it
374 is followed by a newline, both the ‘\’ and the newline are stripped; oth‐
375 erwise, both the ‘\’ and the character following are unchanged.
376 If a single-quoted string is preceded by an unquoted ‘$’, C style back‐
378 slash expansion (see below) is applied (even single quote characters
379 inside can be escaped and do not terminate the string then); the expanded
380 result is treated as any other single-quoted string. If a double-quoted
381 string is preceded by an unquoted ‘$’, the ‘$’ is simply ignored.
382 Backslash expansion
384 In places where backslashes are expanded, certain C and AT&T UNIX ksh or
385 GNU bash style escapes are translated. These include “\a”, “\b”, “\f”,
386 “\n”, “\r”, “\t”, “\U########”, “\u####” and “\v”. For “\U########” and
387 “\u####”, “#” means a hexadecimal digit, of which there may be none up to
388 four or eight; these escapes translate a Unicode codepoint to UTF-8.
389 Furthermore, “\E” and “\e” expand to the escape character.
390 In the print builtin mode, “\"”, “\'” and “\?” are explicitly excluded;
392 octal sequences must have the none up to three octal digits “#” prefixed
393 with the digit zero (“\0###”); hexadecimal sequences “\x##” are limited
394 to none up to two hexadecimal digits “#”; both octal and hexadecimal
395 sequences convert to raw octets; “\#”, where # is none of the above,
396 translates to \# (backslashes are retained).
397 Backslash expansion in the C style mode slightly differs: octal sequences
399 “\###” must have no digit zero prefixing the one up to three octal digits
400 “#” and yield raw octets; hexadecimal sequences “\x#*” greedily eat up as
401 many hexadecimal digits “#” as they can and terminate with the first non-
402 hexadecimal digit; these translate a Unicode codepoint to UTF-8. The
403 sequence “\c#”, where “#” is any octet, translates to Ctrl-# (which basi‐
404 cally means, “\c?” becomes DEL, everything else is bitwise ANDed with
405 0x1F). Finally, “\#”, where # is none of the above, translates to # (has
406 the backslash trimmed), even if it is a newline.
407 Aliases
409 There are two types of aliases: normal command aliases and tracked
410 aliases. Command aliases are normally used as a short hand for a long or
411 often used command. The shell expands command aliases (i.e. substitutes
412 the alias name for its value) when it reads the first word of a command.
413 An expanded alias is re-processed to check for more aliases. If a com‐
414 mand alias ends in a space or tab, the following word is also checked for
415 alias expansion. The alias expansion process stops when a word that is
416 not an alias is found, when a quoted word is found, or when an alias word
417 that is currently being expanded is found. Aliases are specifically an
418 interactive feature: while they do happen to work in scripts and on the
419 command line in some cases, aliases are expanded during lexing, so their
420 use must be in a separate command tree from their definition; otherwise,
421 the alias will not be found. Noticeably, command lists (separated by
422 semicolon, in command substitutions also by newline) may be one same
423 parse tree.
424 The following command aliases are defined automatically by the shell:
426 autoload='\\builtin typeset -fu'
428 functions='\\builtin typeset -f'
429 hash='\\builtin alias -t'
430 history='\\builtin fc -l'
431 integer='\\builtin typeset -i'
432 local='\\builtin typeset'
433 login='\\builtin exec login'
434 nameref='\\builtin typeset -n'
435 nohup='nohup '
436 r='\\builtin fc -e -'
437 type='\\builtin whence -v'
438 Tracked aliases allow the shell to remember where it found a particular
440 command. The first time the shell does a path search for a command that
441 is marked as a tracked alias, it saves the full path of the command. The
442 next time the command is executed, the shell checks the saved path to see
443 that it is still valid, and if so, avoids repeating the path search.
444 Tracked aliases can be listed and created using alias -t. Note that
445 changing the PATH parameter clears the saved paths for all tracked
446 aliases. If the trackall option is set (i.e. set -o trackall or set -h),
447 the shell tracks all commands. This option is set automatically for non-
448 interactive shells. For interactive shells, only the following commands
449 are automatically tracked: cat(1), cc(1), chmod(1), cp(1), date(1),
450 ed(1), emacs(1), grep(1), ls(1), make(1), mv(1), pr(1), rm(1), sed(1),
451 sh(1), vi(1) and who(1).
452 Substitution
454 The first step the shell takes in executing a simple-command is to per‐
455 form substitutions on the words of the command. There are three kinds of
456 substitution: parameter, command and arithmetic. Parameter substitu‐
457 tions, which are described in detail in the next section, take the form
458 $name or ${...}; command substitutions take the form $(command) or (dep‐
459 recated) `command` or (executed in the current environment) ${ command;}
460 and strip trailing newlines; and arithmetic substitutions take the form
461 $((expression)). Parsing the current-environment command substitution
462 requires a space, tab or newline after the opening brace and that the
463 closing brace be recognised as a keyword (i.e. is preceded by a newline
464 or semicolon). They are also called funsubs (function substitutions) and
465 behave like functions in that local and return work, and in that exit
466 terminates the parent shell; shell options are shared.
467 Another variant of substitution are the valsubs (value substitutions)
469 ${|command;} which are also executed in the current environment, like
470 funsubs, but share their I/O with the parent; instead, they evaluate to
471 whatever the, initially empty, expression-local variable REPLY is set to
472 within the commands.
473 If a substitution appears outside of double quotes, the results of the
475 substitution are generally subject to word or field splitting according
476 to the current value of the IFS parameter. The IFS parameter specifies a
477 list of octets which are used to break a string up into several words;
478 any octets from the set space, tab and newline that appear in the IFS
479 octets are called “IFS whitespace”. Sequences of one or more IFS white‐
480 space octets, in combination with zero or one non-IFS whitespace octets,
481 delimit a field. As a special case, leading and trailing IFS whitespace
482 is stripped (i.e. no leading or trailing empty field is created by it);
483 leading or trailing non-IFS whitespace does create an empty field.
484 Example: If IFS is set to “<space>:” and VAR is set to
486 “<space>A<space>:<space><space>B::D”, the substitution for $VAR results
487 in four fields: “A”, “B”, “” (an empty field) and “D”. Note that if the
488 IFS parameter is set to the empty string, no field splitting is done; if
489 it is unset, the default value of space, tab and newline is used.
490 Also, note that the field splitting applies only to the immediate result
492 of the substitution. Using the previous example, the substitution for
493 $VAR:E results in the fields: “A”, “B”, “” and “D:E”, not “A”, “B”, “”,
494 “D” and “E”. This behavior is POSIX compliant, but incompatible with
495 some other shell implementations which do field splitting on the word
496 which contained the substitution or use IFS as a general whitespace
497 delimiter.
498 The results of substitution are, unless otherwise specified, also subject
500 to brace expansion and file name expansion (see the relevant sections
501 below).
502 A command substitution is replaced by the output generated by the speci‐
504 fied command which is run in a subshell. For $(command) and ${|command;}
505 and ${ command;} substitutions, normal quoting rules are used when
506 command is parsed; however, for the deprecated `command` form, a ‘\’ fol‐
507 lowed by any of ‘$’, ‘`’ or ‘\’ is stripped (as is ‘"’ when the substitu‐
508 tion is part of a double-quoted string); a backslash ‘\’ followed by any
509 other character is unchanged. As a special case in command substitu‐
510 tions, a command of the form <file is interpreted to mean substitute the
511 contents of file. Note that $(<foo) has the same effect as $(cat foo).
512 Note that some shells do not use a recursive parser for command substitu‐
514 tions, leading to failure for certain constructs; to be portable, use as
515 workaround “x=$(cat) <<\EOF” (or the newline-keeping “x=<<\EOF” exten‐
516 sion) instead to merely slurp the string. IEEE Std 1003.1 (“POSIX.1”)
517 recommends using case statements of the form x=$(case $foo in (bar) echo
518 $bar ;; (*) echo $baz ;; esac) instead, which would work but not serve as
519 example for this portability issue.
520 x=$(case $foo in bar) echo $bar ;; *) echo $baz ;; esac)
522 # above fails to parse on old shells; below is the workaround
523 x=$(eval $(cat)) <<\EOF
524 case $foo in bar) echo $bar ;; *) echo $baz ;; esac
525 EOF
526 Arithmetic substitutions are replaced by the value of the specified
528 expression. For example, the command print $((2+3*4)) displays 14. See
529 Arithmetic expressions for a description of an expression.
530 Parameters
532 Parameters are shell variables; they can be assigned values and their
533 values can be accessed using a parameter substitution. A parameter name
534 is either one of the special single punctuation or digit character param‐
535 eters described below, or a letter followed by zero or more letters or
536 digits (‘_’ counts as a letter). The latter form can be treated as
537 arrays by appending an array index of the form [expr] where expr is an
538 arithmetic expression. Array indices in mksh are limited to the range 0
539 through 4294967295, inclusive. That is, they are a 32-bit unsigned inte‐
540 ger.
541 Parameter substitutions take the form $name, ${name} or ${name[expr]}
543 where name is a parameter name. Substitution of all array elements with
544 ${name[*]} and ${name[@]} works equivalent to $* and $@ for positional
545 parameters. If substitution is performed on a parameter (or an array
546 parameter element) that is not set, an empty string is substituted unless
547 the nounset option (set -u) is set, in which case an error occurs.
548 Parameters can be assigned values in a number of ways. First, the shell
550 implicitly sets some parameters like “#”, “PWD” and “$”; this is the only
551 way the special single character parameters are set. Second, parameters
552 are imported from the shell's environment at startup. Third, parameters
553 can be assigned values on the command line: for example, FOO=bar sets the
554 parameter “FOO” to “bar”; multiple parameter assignments can be given on
555 a single command line and they can be followed by a simple-command, in
556 which case the assignments are in effect only for the duration of the
557 command (such assignments are also exported; see below for the implica‐
558 tions of this). Note that both the parameter name and the ‘=’ must be
559 unquoted for the shell to recognise a parameter assignment. The con‐
560 struct FOO+=baz is also recognised; the old and new values are immedi‐
561 ately concatenated. The fourth way of setting a parameter is with the
562 export, global, readonly and typeset commands; see their descriptions in
563 the Command execution section. Fifth, for and select loops set parame‐
564 ters as well as the getopts, read and set -A commands. Lastly, parame‐
565 ters can be assigned values using assignment operators inside arithmetic
566 expressions (see Arithmetic expressions below) or using the ${name=value}
567 form of the parameter substitution (see below).
568 Parameters with the export attribute (set using the export or typeset -x
570 commands, or by parameter assignments followed by simple commands) are
571 put in the environment (see environ(7)) of commands run by the shell as
572 name=value pairs. The order in which parameters appear in the environ‐
573 ment of a command is unspecified. When the shell starts up, it extracts
574 parameters and their values from its environment and automatically sets
575 the export attribute for those parameters.
576 Modifiers can be applied to the ${name} form of parameter substitution:
578 ${name:-word}
580 If name is set and not empty, it is substituted; otherwise, word
581 is substituted.
582 ${name:+word}
584 If name is set and not empty, word is substituted; otherwise,
585 nothing is substituted.
586 ${name:=word}
588 If name is set and not empty, it is substituted; otherwise, it is
589 assigned word and the resulting value of name is substituted.
590 ${name:?word}
592 If name is set and not empty, it is substituted; otherwise, word
593 is printed on standard error (preceded by name:) and an error
594 occurs (normally causing termination of a shell script, function,
595 or a script sourced using the “.” built-in). If word is omitted,
596 the string “parameter null or not set” is used instead.
597 Note that, for all of the above, word is actually considered quoted, and
599 special parsing rules apply. The parsing rules also differ on whether
600 the expression is double-quoted: word then uses double-quoting rules,
601 except for the double quote itself (‘"’) and the closing brace, which, if
602 backslash escaped, gets quote removal applied.
603 In the above modifiers, the ‘:’ can be omitted, in which case the condi‐
605 tions only depend on name being set (as opposed to set and not empty).
606 If word is needed, parameter, command, arithmetic and tilde substitution
607 are performed on it; if word is not needed, it is not evaluated.
608 The following forms of parameter substitution can also be used (if name
610 is an array, the element with the key “0” will be substituted in scalar
611 context):
612 ${#name}
614 The number of positional parameters if name is “*”, “@” or not
615 specified; otherwise the length (in characters) of the string
616 value of parameter name.
617 ${#name[*]}
619 ${#name[@]}
620 The number of elements in the array name.
621 ${%name}
623 The width (in screen columns) of the string value of parameter
624 name, or -1 if ${name} contains a control character.
625 ${!name}
627 The name of the variable referred to by name. This will be name
628 except when name is a name reference (bound variable), created by
629 the nameref command (which is an alias for typeset -n). name
630 cannot be one of most special parameters (see below).
631 ${!name[*]}
633 ${!name[@]}
634 The names of indices (keys) in the array name.
635 ${name#pattern}
637 ${name##pattern}
638 If pattern matches the beginning of the value of parameter name,
639 the matched text is deleted from the result of substitution. A
640 single ‘#’ results in the shortest match, and two of them result
641 in the longest match. Cannot be applied to a vector (${*} or
642 ${@} or ${array[*]} or ${array[@]}).
643 ${name%pattern}
645 ${name%%pattern}
646 Like ${...#...} substitution, but it deletes from the end of the
647 value. Cannot be applied to a vector.
648 ${name/pattern/string}
650 ${name/#pattern/string}
651 ${name/%pattern/string}
652 ${name//pattern/string}
653 The longest match of pattern in the value of parameter name is
654 replaced with string (deleted if string is empty; the trailing
655 slash (‘/’) may be omitted in that case). A leading slash fol‐
656 lowed by ‘#’ or ‘%’ causes the pattern to be anchored at the
657 beginning or end of the value, respectively; empty unanchored
658 patterns cause no replacement; a single leading slash or use of a
659 pattern that matches the empty string causes the replacement to
660 happen only once; two leading slashes cause all occurrences of
661 matches in the value to be replaced. Cannot be applied to a vec‐
662 tor. Inefficiently implemented, may be slow.
663 ${name@/pattern/string}
665 The same as ${name//pattern/string}, except that both pattern and
666 string are expanded anew for each iteration.
667 ${name:pos:len}
669 The first len characters of name, starting at position pos, are
670 substituted. Both pos and :len are optional. If pos is nega‐
671 tive, counting starts at the end of the string; if it is omitted,
672 it defaults to 0. If len is omitted or greater than the length
673 of the remaining string, all of it is substituted. Both pos and
674 len are evaluated as arithmetic expressions. Currently, pos must
675 start with a space, opening parenthesis or digit to be recog‐
676 nised. Cannot be applied to a vector.
677 ${name@#}
679 The hash (using the BAFH algorithm) of the expansion of name.
680 This is also used internally for the shell's hashtables.
681 ${name@Q}
683 A quoted expression safe for re-entry, whose value is the value
684 of the name parameter, is substituted.
685 Note that pattern may need extended globbing pattern (@(...)), single
687 ('...') or double ("...") quote escaping unless -o sh is set.
688 The following special parameters are implicitly set by the shell and can‐
690 not be set directly using assignments:
691 ! Process ID of the last background process started. If no back‐
693 ground processes have been started, the parameter is not set.
694 # The number of positional parameters ($1, $2, etc.).
696 $ The PID of the shell or, if it is a subshell, the PID of the
698 original shell. Do NOT use this mechanism for generating tempo‐
699 rary file names; see mktemp(1) instead.
700 - The concatenation of the current single letter options (see the
702 set command below for a list of options).
703 ? The exit status of the last non-asynchronous command executed.
705 If the last command was killed by a signal, $? is set to 128 plus
706 the signal number, but at most 255.
707 0 The name of the shell, determined as follows: the first argument
709 to mksh if it was invoked with the -c option and arguments were
710 given; otherwise the file argument, if it was supplied; or else
711 the basename the shell was invoked with (i.e. argv[0]). $0 is
712 also set to the name of the current script or the name of the
713 current function, if it was defined with the function keyword
714 (i.e. a Korn shell style function).
715 1 .. 9 The first nine positional parameters that were supplied to the
717 shell, function, or script sourced using the “.” built-in. Fur‐
718 ther positional parameters may be accessed using ${number}.
719 * All positional parameters (except 0), i.e. $1, $2, $3, ...
721 If used outside of double quotes, parameters are separate words
722 (which are subjected to word splitting); if used within double
723 quotes, parameters are separated by the first character of the
724 IFS parameter (or the empty string if IFS is unset.
725 @ Same as $*, unless it is used inside double quotes, in which case
727 a separate word is generated for each positional parameter. If
728 there are no positional parameters, no word is generated. "$@"
729 can be used to access arguments, verbatim, without losing empty
730 arguments or splitting arguments with spaces (IFS, actually).
731 The following parameters are set and/or used by the shell:
733 _ (underscore) When an external command is executed by the
735 shell, this parameter is set in the environment of the new
736 process to the path of the executed command. In interactive
737 use, this parameter is also set in the parent shell to the
738 last word of the previous command.
739 BASHPID The PID of the shell or subshell.
741 CDPATH Like PATH, but used to resolve the argument to the cd built-
743 in command. Note that if CDPATH is set and does not contain
744 “.” or an empty string element, the current directory is not
745 searched. Also, the cd built-in command will display the
746 resulting directory when a match is found in any search path
747 other than the empty path.
748 COLUMNS Set to the number of columns on the terminal or window.
750 Always set, defaults to 80, unless the value as reported by
751 stty(1) is non-zero and sane enough (minimum is 12x3); simi‐
752 lar for LINES. This parameter is used by the interactive
753 line editing modes and by the select, set -o and kill -l
754 commands to format information columns. Importing from the
755 environment or unsetting this parameter removes the binding
756 to the actual terminal size in favour of the provided value.
757 ENV If this parameter is found to be set after any profile files
759 are executed, the expanded value is used as a shell startup
760 file. It typically contains function and alias definitions.
761 EPOCHREALTIME
763 Time since the epoch, as returned by gettimeofday(2), for‐
764 matted as decimal tv_sec followed by a dot (‘.’) and tv_usec
765 padded to exactly six decimal digits.
766 EXECSHELL If set, this parameter is assumed to contain the shell that
768 is to be used to execute commands that execve(2) fails to
769 execute and which do not start with a “#!shell” sequence.
770 FCEDIT The editor used by the fc command (see below).
772 FPATH Like PATH, but used when an undefined function is executed
774 to locate the file defining the function. It is also
775 searched when a command can't be found using PATH. See
776 Functions below for more information.
777 HISTFILE The name of the file used to store command history. When
779 assigned to or unset, the file is opened, history is trun‐
780 cated then loaded from the file; subsequent new commands
781 (possibly consisting of several lines) are appended once
782 they successfully compiled. Also, several invocations of
783 the shell will share history if their HISTFILE parameters
784 all point to the same file.
785 Note: If HISTFILE is unset or empty, no history file is
787 used. This is different from AT&T UNIX ksh.
788 HISTSIZE The number of commands normally stored for history. The
790 default is 2047. Do not set this value to insanely high
791 values such as 1000000000 because mksh can then not allocate
792 enough memory for the history and will not start.
793 HOME The default directory for the cd command and the value sub‐
795 stituted for an unqualified ~ (see Tilde expansion below).
796 IFS Internal field separator, used during substitution and by
798 the read command, to split values into distinct arguments;
799 normally set to space, tab and newline. See Substitution
800 above for details.
801 Note: This parameter is not imported from the environment
803 when the shell is started.
804 KSHEGID The effective group id of the shell.
806 KSHGID The real group id of the shell.
808 KSHUID The real user id of the shell.
810 KSH_MATCH The last matched string. In a future version, this will be
812 an indexed array, with indexes 1 and up capturing matching
813 groups. Set by string comparisons (== and !=) in double-
814 bracket test expressions when a match is found (when !=
815 returns false), by case when a match is encountered, and by
816 the substitution operations ${x#pat}, ${x##pat}, ${x%pat},
817 ${x%%pat}, ${x/pat/rpl}, ${x/#pat/rpl}, ${x/%pat/rpl},
818 ${x//pat/rpl}, and ${x@/pat/rpl}. See the end of the Emacs
819 editing mode documentation for an example.
820 KSH_VERSION The name and version of the shell (read-only). See also the
822 version commands in Emacs editing mode and Vi editing mode
823 sections, below.
824 LINENO The line number of the function or shell script that is cur‐
826 rently being executed.
827 LINES Set to the number of lines on the terminal or window.
829 Always set, defaults to 24. See COLUMNS.
830 OLDPWD The previous working directory. Unset if cd has not suc‐
832 cessfully changed directories since the shell started or if
833 the shell doesn't know where it is.
834 OPTARG When using getopts, it contains the argument for a parsed
836 option, if it requires one.
837 OPTIND The index of the next argument to be processed when using
839 getopts. Assigning 1 to this parameter causes getopts to
840 process arguments from the beginning the next time it is
841 invoked.
842 PATH A colon (semicolon on OS/2) separated list of directories
844 that are searched when looking for commands and files
845 sourced using the “.” command (see below). An empty string
846 resulting from a leading or trailing (semi)colon, or two
847 adjacent ones, is treated as a “.” (the current directory).
848 PATHSEP A colon (semicolon on OS/2), for the user's convenience.
850 PGRP The process ID of the shell's process group leader.
852 PIPESTATUS An array containing the errorlevel (exit status) codes, one
854 by one, of the last pipeline run in the foreground.
855 PPID The process ID of the shell's parent.
857 PS1 The primary prompt for interactive shells. Parameter, com‐
859 mand and arithmetic substitutions are performed, and ‘!’ is
860 replaced with the current command number (see the fc command
861 below). A literal ‘!’ can be put in the prompt by placing
862 “!!” in PS1.
863 The default prompt is “$ ” for non-root users, “# ” for
865 root. If mksh is invoked by root and PS1 does not contain a
866 ‘#’ character, the default value will be used even if PS1
867 already exists in the environment.
868 The mksh distribution comes with a sample dot.mkshrc con‐
870 taining a sophisticated example, but you might like the fol‐
871 lowing one (note that ${HOSTNAME:=$(hostname)} and the root-
872 vs-user distinguishing clause are (in this example) executed
873 at PS1 assignment time, while the $USER and $PWD are escaped
874 and thus will be evaluated each time a prompt is displayed):
875 PS1='${USER:=$(id -un)}'"@${HOSTNAME:=$(hostname)}:\$PWD $(
877 if (( USER_ID )); then print \$; else print \#; fi) "
878 Note that since the command-line editors try to figure out
880 how long the prompt is (so they know how far it is to the
881 edge of the screen), escape codes in the prompt tend to mess
882 things up. You can tell the shell not to count certain
883 sequences (such as escape codes) by prefixing your prompt
884 with a character (such as Ctrl-A) followed by a carriage
885 return and then delimiting the escape codes with this char‐
886 acter. Any occurrences of that character in the prompt are
887 not printed. By the way, don't blame me for this hack; it's
888 derived from the original ksh88(1), which did print the
889 delimiter character so you were out of luck if you did not
890 have any non-printing characters.
891 Since backslashes and other special characters may be inter‐
893 preted by the shell, to set PS1 either escape the backslash
894 itself or use double quotes. The latter is more practical.
895 This is a more complex example, avoiding to directly enter
896 special characters (for example with ^V in the emacs editing
897 mode), which embeds the current working directory, in
898 reverse video (colour would work, too), in the prompt
899 string:
900 x=$(print \\001) # otherwise unused char
902 PS1="$x$(print \\r)$x$(tput so)$x\$PWD$x$(tput se)$x> "
903 Due to a strong suggestion from David G. Korn, mksh now also
905 supports the following form:
906 PS1=$'\1\r\1\e[7m\1$PWD\1\e[0m\1> '
908 PS2 Secondary prompt string, by default “> ”, used when more
910 input is needed to complete a command.
911 PS3 Prompt used by the select statement when reading a menu
913 selection. The default is “#? ”.
914 PS4 Used to prefix commands that are printed during execution
916 tracing (see the set -x command below). Parameter, command
917 and arithmetic substitutions are performed before it is
918 printed. The default is “+ ”. You may want to set it to
919 “[$EPOCHREALTIME] ” instead, to include timestamps.
920 PWD The current working directory. May be unset or empty if the
922 shell doesn't know where it is.
923 RANDOM Each time RANDOM is referenced, it is assigned a number
925 between 0 and 32767 from a Linear Congruential PRNG first.
926 REPLY Default parameter for the read command if no names are
928 given. Also used in select loops to store the value that is
929 read from standard input.
930 SECONDS The number of seconds since the shell started or, if the
932 parameter has been assigned an integer value, the number of
933 seconds since the assignment plus the value that was
934 assigned.
935 TMOUT If set to a positive integer in an interactive shell, it
937 specifies the maximum number of seconds the shell will wait
938 for input after printing the primary prompt (PS1). If the
939 time is exceeded, the shell exits.
940 TMPDIR The directory temporary shell files are created in. If this
942 parameter is not set or does not contain the absolute path
943 of a writable directory, temporary files are created in
944 /tmp.
945 USER_ID The effective user id of the shell.
947 Tilde expansion
949 Tilde expansion, which is done in parallel with parameter substitution,
950 is applied to words starting with an unquoted ‘~’. In parameter assign‐
951 ments (such as those preceding a simple-command or those occurring in the
952 arguments of a declaration utility), tilde expansion is done after any
953 assignment (i.e. after the equals sign) or after an unquoted colon (‘:’);
954 login names are also delimited by colons. The Korn shell, except in
955 POSIX mode, always expands tildes after unquoted equals signs, not just
956 in assignment context (see below), and enables tab completion for tildes
957 after all unquoted colons during command line editing.
958 The characters following the tilde, up to the first ‘/’, if any, are
960 assumed to be a login name. If the login name is empty, ‘+’ or ‘-’, the
961 simplified value of the HOME, PWD or OLDPWD parameter is substituted,
962 respectively. Otherwise, the password file is searched for the login
963 name, and the tilde expression is substituted with the user's home direc‐
964 tory. If the login name is not found in the password file or if any
965 quoting or parameter substitution occurs in the login name, no substitu‐
966 tion is performed.
967 The home directory of previously expanded login names are cached and re-
969 used. The alias -d command may be used to list, change and add to this
970 cache (e.g. alias -d fac=/usr/local/facilities; cd ~fac/bin).
971 Brace expansion (alternation)
973 Brace expressions take the following form:
974 prefix{str1,...,strN}suffix
976 The expressions are expanded to N words, each of which is the concatena‐
978 tion of prefix, stri and suffix (e.g. “a{c,b{X,Y},d}e” expands to four
979 words: “ace”, “abXe”, “abYe” and “ade”). As noted in the example, brace
980 expressions can be nested and the resulting words are not sorted. Brace
981 expressions must contain an unquoted comma (‘,’) for expansion to occur
982 (e.g. {} and {foo} are not expanded). Brace expansion is carried out
983 after parameter substitution and before file name generation.
984 File name patterns
986 A file name pattern is a word containing one or more unquoted ‘?’, ‘*’,
987 ‘+’, ‘@’ or ‘!’ characters or “[...]” sequences. Once brace expansion
988 has been performed, the shell replaces file name patterns with the sorted
989 names of all the files that match the pattern (if no files match, the
990 word is left unchanged). The pattern elements have the following mean‐
991 ing:
992 ? Matches any single character.
994 * Matches any sequence of octets.
996 [...] Matches any of the octets inside the brackets. Ranges of octets
998 can be specified by separating two octets by a ‘-’ (e.g. “[a0-9]”
999 matches the letter ‘a’ or any digit). In order to represent
1000 itself, a ‘-’ must either be quoted or the first or last octet in
1001 the octet list. Similarly, a ‘]’ must be quoted or the first
1002 octet in the list if it is to represent itself instead of the end
1003 of the list. Also, a ‘!’ appearing at the start of the list has
1004 special meaning (see below), so to represent itself it must be
1005 quoted or appear later in the list.
1006 [!...] Like [...], except it matches any octet not inside the brackets.
1008 *(pattern|...|pattern)
1010 Matches any string of octets that matches zero or more occur‐
1011 rences of the specified patterns. Example: The pattern
1012 *(foo|bar) matches the strings “”, “foo”, “bar”, “foobarfoo”,
1013 etc.
1014 +(pattern|...|pattern)
1016 Matches any string of octets that matches one or more occurrences
1017 of the specified patterns. Example: The pattern +(foo|bar)
1018 matches the strings “foo”, “bar”, “foobar”, etc.
1019 ?(pattern|...|pattern)
1021 Matches the empty string or a string that matches one of the
1022 specified patterns. Example: The pattern ?(foo|bar) only matches
1023 the strings “”, “foo” and “bar”.
1024 @(pattern|...|pattern)
1026 Matches a string that matches one of the specified patterns.
1027 Example: The pattern @(foo|bar) only matches the strings “foo”
1028 and “bar”.
1029 !(pattern|...|pattern)
1031 Matches any string that does not match one of the specified pat‐
1032 terns. Examples: The pattern !(foo|bar) matches all strings
1033 except “foo” and “bar”; the pattern !(*) matches no strings; the
1034 pattern !(?)* matches all strings (think about it).
1035 Note that complicated globbing, especially with alternatives, is slow;
1037 using separate comparisons may (or may not) be faster.
1038 Note that mksh (and pdksh) never matches “.” and “..”, but AT&T UNIX ksh,
1040 Bourne sh and GNU bash do.
1041 Note that none of the above pattern elements match either a period (‘.’)
1043 at the start of a file name or a slash (‘/’), even if they are explicitly
1044 used in a [...] sequence; also, the names “.” and “..” are never matched,
1045 even by the pattern “.*”.
1046 If the markdirs option is set, any directories that result from file name
1048 generation are marked with a trailing ‘/’.
1049 Input/output redirection
1051 When a command is executed, its standard input, standard output and stan‐
1052 dard error (file descriptors 0, 1 and 2, respectively) are normally
1053 inherited from the shell. Three exceptions to this are commands in pipe‐
1054 lines, for which standard input and/or standard output are those set up
1055 by the pipeline, asynchronous commands created when job control is dis‐
1056 abled, for which standard input is initially set to /dev/null, and com‐
1057 mands for which any of the following redirections have been specified:
1058 >file Standard output is redirected to file. If file does not
1060 exist, it is created; if it does exist, is a regular file,
1061 and the noclobber option is set, an error occurs; otherwise,
1062 the file is truncated. Note that this means the command cmd
1063 <foo >foo will open foo for reading and then truncate it when
1064 it opens it for writing, before cmd gets a chance to actually
1065 read foo.
1066 >|file Same as >, except the file is truncated, even if the
1068 noclobber option is set.
1069 >>file Same as >, except if file exists it is appended to instead of
1071 being truncated. Also, the file is opened in append mode, so
1072 writes always go to the end of the file (see open(2)).
1073 <file Standard input is redirected from file, which is opened for
1075 reading.
1076 <>file Same as <, except the file is opened for reading and writing.
1078 <<marker After reading the command line containing this kind of redi‐
1080 rection (called a “here document”), the shell copies lines
1081 from the command source into a temporary file until a line
1082 matching marker is read. When the command is executed, stan‐
1083 dard input is redirected from the temporary file. If marker
1084 contains no quoted characters, the contents of the temporary
1085 file are processed as if enclosed in double quotes each time
1086 the command is executed, so parameter, command and arithmetic
1087 substitutions are performed, along with backslash (‘\’)
1088 escapes for ‘$’, ‘`’, ‘\’ and “\newline”, but not for ‘"’.
1089 If multiple here documents are used on the same command line,
1090 they are saved in order.
1091 If no marker is given, the here document ends at the next <<
1093 and substitution will be performed. If marker is only a set
1094 of either single “''” or double ‘""’ quotes with nothing in
1095 between, the here document ends at the next empty line and
1096 substitution will not be performed.
1097 <<-marker Same as <<, except leading tabs are stripped from lines in
1099 the here document.
1100 <<<word Same as <<, except that word is the here document. This is
1102 called a here string.
1103 <&fd Standard input is duplicated from file descriptor fd. fd can
1105 be a single digit, indicating the number of an existing file
1106 descriptor; the letter ‘p’, indicating the file descriptor
1107 associated with the output of the current co-process; or the
1108 character ‘-’, indicating standard input is to be closed.
1109 >&fd Same as <&, except the operation is done on standard output.
1111 &>file Same as >file 2>&1. This is a deprecated (legacy) GNU bash
1113 extension supported by mksh which also supports the preceding
1114 explicit fd digit, for example, 3&>file is the same as 3>file
1115 2>&3 in mksh but a syntax error in GNU bash.
1116 &>|file, &>>file, &>&fd
1118 Same as >|file, >>file or >&fd, followed by 2>&1, as above.
1119 These are mksh extensions.
1120 In any of the above redirections, the file descriptor that is redirected
1122 (i.e. standard input or standard output) can be explicitly given by pre‐
1123 ceding the redirection with a single digit. Parameter, command and
1124 arithmetic substitutions, tilde substitutions, and, if the shell is
1125 interactive, file name generation are all performed on the file, marker
1126 and fd arguments of redirections. Note, however, that the results of any
1127 file name generation are only used if a single file is matched; if multi‐
1128 ple files match, the word with the expanded file name generation charac‐
1129 ters is used. Note that in restricted shells, redirections which can
1130 create files cannot be used.
1131 For simple-commands, redirections may appear anywhere in the command; for
1133 compound-commands (if statements, etc.), any redirections must appear at
1134 the end. Redirections are processed after pipelines are created and in
1135 the order they are given, so the following will print an error with a
1136 line number prepended to it:
1137 $ cat /foo/bar 2>&1 >/dev/null | pr -n -t
1139 File descriptors created by I/O redirections are private to the shell.
1141 Arithmetic expressions
1143 Integer arithmetic expressions can be used with the let command, inside
1144 $((...)) expressions, inside array references (e.g. name[expr]), as
1145 numeric arguments to the test command, and as the value of an assignment
1146 to an integer parameter. Warning: This also affects implicit conversion
1147 to integer, for example as done by the let command. Never use unchecked
1148 user input, e.g. from the environment, in an arithmetic context!
1149 Expressions are calculated using signed arithmetic and the mksh_ari_t
1151 type (a 32-bit signed integer), unless they begin with a sole ‘#’ charac‐
1152 ter, in which case they use mksh_uari_t (a 32-bit unsigned integer).
1153 Expressions may contain alpha-numeric parameter identifiers, array refer‐
1155 ences and integer constants and may be combined with the following C
1156 operators (listed and grouped in increasing order of precedence):
1157 Unary operators:
1159 + - ! ~ ++ --
1161 Binary operators:
1163 ,
1165 = += -= *= /= %= <<= >>= ^<= ^>= &= ^= |=
1166 ||
1167 &&
1168 |
1169 ^
1170 &
1171 == !=
1172 < <= > >=
1173 << >> ^< ^>
1174 + -
1175 * / %
1176 Ternary operators:
1178 ?: (precedence is immediately higher than assignment)
1180 Grouping operators:
1182 ( )
1184 Integer constants and expressions are calculated using an exactly 32-bit
1186 wide, signed or unsigned, type with silent wraparound on integer over‐
1187 flow. Integer constants may be specified with arbitrary bases using the
1188 notation base#number, where base is a decimal integer specifying the base
1189 (up to 36), and number is a number in the specified base. Additionally,
1190 base-16 integers may be specified by prefixing them with “0x”
1191 (case-insensitive) in all forms of arithmetic expressions, except as
1192 numeric arguments to the test built-in utility. Prefixing numbers with a
1193 sole digit zero (“0”) does not cause interpretation as octal (except in
1194 POSIX mode, as required by the standard), as that's unsafe to do.
1195 As a special mksh extension, numbers to the base of one are treated as
1197 either (8-bit transparent) ASCII or Unicode codepoints, depending on the
1198 shell's utf8-mode flag (current setting). The AT&T UNIX ksh93 syntax of
1199 “'x'” instead of “1#x” is also supported. Note that NUL bytes (integral
1200 value of zero) cannot be used. An unset or empty parameter evaluates to
1201 0 in integer context. In Unicode mode, raw octets are mapped into the
1202 range EF80..EFFF as in OPTU-8, which is in the PUA and has been assigned
1203 by CSUR for this use. If more than one octet in ASCII mode, or a
1204 sequence of more than one octet not forming a valid and minimal CESU-8
1205 sequence is passed, the behaviour is undefined (usually, the shell aborts
1206 with a parse error, but rarely, it succeeds, e.g. on the sequence C2 20).
1207 That's why you should always use ASCII mode unless you know that the
1208 input is well-formed UTF-8 in the range of 0000..FFFD if you use this
1209 feature, as opposed to read -a.
1210 The operators are evaluated as follows:
1212 unary +
1214 Result is the argument (included for completeness).
1215 unary -
1217 Negation.
1218 ! Logical NOT; the result is 1 if argument is zero, 0 if not.
1220 ~ Arithmetic (bit-wise) NOT.
1222 ++ Increment; must be applied to a parameter (not a literal or
1224 other expression). The parameter is incremented by 1.
1225 When used as a prefix operator, the result is the incre‐
1226 mented value of the parameter; when used as a postfix oper‐
1227 ator, the result is the original value of the parameter.
1228 -- Similar to ++, except the parameter is decremented by 1.
1230 , Separates two arithmetic expressions; the left-hand side is
1232 evaluated first, then the right. The result is the value
1233 of the expression on the right-hand side.
1234 = Assignment; the variable on the left is set to the value on
1236 the right.
1237 += -= *= /= %= <<= >>= ^<= ^>= &= ^= |=
1239 Assignment operators. <var><op>=<expr> is the same as
1240 <var>=<var><op><expr>, with any operator precedence in
1241 <expr> preserved. For example, “var1 *= 5 + 3” is the same
1242 as specifying “var1 = var1 * (5 + 3)”.
1243 || Logical OR; the result is 1 if either argument is non-zero,
1245 0 if not. The right argument is evaluated only if the left
1246 argument is zero.
1247 && Logical AND; the result is 1 if both arguments are non-
1249 zero, 0 if not. The right argument is evaluated only if
1250 the left argument is non-zero.
1251 | Arithmetic (bit-wise) OR.
1253 ^ Arithmetic (bit-wise) XOR (exclusive-OR).
1255 & Arithmetic (bit-wise) AND.
1257 == Equal; the result is 1 if both arguments are equal, 0 if
1259 not.
1260 != Not equal; the result is 0 if both arguments are equal, 1
1262 if not.
1263 < Less than; the result is 1 if the left argument is less
1265 than the right, 0 if not.
1266 <= > >=
1268 Less than or equal, greater than, greater than or equal.
1269 See <.
1270 << >> Shift left (right); the result is the left argument with
1272 its bits arithmetically (signed operation) or logically
1273 (unsigned expression) shifted left (right) by the amount
1274 given in the right argument.
1275 ^< ^> Rotate left (right); the result is similar to shift, except
1277 that the bits shifted out at one end are shifted in at the
1278 other end, instead of zero or sign bits.
1279 + - * /
1281 Addition, subtraction, multiplication and division.
1282 % Remainder; the result is the symmetric remainder of the
1284 division of the left argument by the right. To get the
1285 mathematical modulus of “a mod b”, use the formula “(a % b
1286 + b) % b”.
1287 <arg1>?<arg2>:<arg3>
1289 If <arg1> is non-zero, the result is <arg2>; otherwise the
1290 result is <arg3>. The non-result argument is not evalu‐
1291 ated.
1292 Co-processes
1294 A co-process (which is a pipeline created with the “|&” operator) is an
1295 asynchronous process that the shell can both write to (using print -p)
1296 and read from (using read -p). The input and output of the co-process
1297 can also be manipulated using >&p and <&p redirections, respectively.
1298 Once a co-process has been started, another can't be started until the
1299 co-process exits, or until the co-process's input has been redirected
1300 using an exec n>&p redirection. If a co-process's input is redirected in
1301 this way, the next co-process to be started will share the output with
1302 the first co-process, unless the output of the initial co-process has
1303 been redirected using an exec n<&p redirection.
1304 Some notes concerning co-processes:
1306 · The only way to close the co-process's input (so the co-process reads
1308 an end-of-file) is to redirect the input to a numbered file descrip‐
1309 tor and then close that file descriptor: exec 3>&p; exec 3>&-
1310 · In order for co-processes to share a common output, the shell must
1312 keep the write portion of the output pipe open. This means that end-
1313 of-file will not be detected until all co-processes sharing the co-
1314 process's output have exited (when they all exit, the shell closes
1315 its copy of the pipe). This can be avoided by redirecting the output
1316 to a numbered file descriptor (as this also causes the shell to close
1317 its copy). Note that this behaviour is slightly different from the
1318 original Korn shell which closes its copy of the write portion of the
1319 co-process output when the most recently started co-process (instead
1320 of when all sharing co-processes) exits.
1321 · print -p will ignore SIGPIPE signals during writes if the signal is
1323 not being trapped or ignored; the same is true if the co-process
1324 input has been duplicated to another file descriptor and print -un is
1325 used.
1326 Functions
1328 Functions are defined using either Korn shell function function-name syn‐
1329 tax or the Bourne/POSIX shell function-name() syntax (see below for the
1330 difference between the two forms). Functions are like .‐scripts (i.e.
1331 scripts sourced using the “.” built-in) in that they are executed in the
1332 current environment. However, unlike .‐scripts, shell arguments (i.e.
1333 positional parameters $1, $2, etc.) are never visible inside them. When
1334 the shell is determining the location of a command, functions are
1335 searched after special built-in commands, before builtins and the PATH is
1336 searched.
1337 An existing function may be deleted using unset -f function-name. A list
1339 of functions can be obtained using typeset +f and the function defini‐
1340 tions can be listed using typeset -f. The autoload command (which is an
1341 alias for typeset -fu) may be used to create undefined functions: when an
1342 undefined function is executed, the shell searches the path specified in
1343 the FPATH parameter for a file with the same name as the function which,
1344 if found, is read and executed. If after executing the file the named
1345 function is found to be defined, the function is executed; otherwise, the
1346 normal command search is continued (i.e. the shell searches the regular
1347 built-in command table and PATH). Note that if a command is not found
1348 using PATH, an attempt is made to autoload a function using FPATH (this
1349 is an undocumented feature of the original Korn shell).
1350 Functions can have two attributes, “trace” and “export”, which can be set
1352 with typeset -ft and typeset -fx, respectively. When a traced function
1353 is executed, the shell's xtrace option is turned on for the function's
1354 duration. The “export” attribute of functions is currently not used. In
1355 the original Korn shell, exported functions are visible to shell scripts
1356 that are executed.
1357 Since functions are executed in the current shell environment, parameter
1359 assignments made inside functions are visible after the function com‐
1360 pletes. If this is not the desired effect, the typeset command can be
1361 used inside a function to create a local parameter. Note that AT&T UNIX
1362 ksh93 uses static scoping (one global scope, one local scope per func‐
1363 tion) and allows local variables only on Korn style functions, whereas
1364 mksh uses dynamic scoping (nested scopes of varying locality). Note that
1365 special parameters (e.g. $$, $!) can't be scoped in this way.
1366 The exit status of a function is that of the last command executed in the
1368 function. A function can be made to finish immediately using the return
1369 command; this may also be used to explicitly specify the exit status.
1370 Note that when called in a subshell, return will only exit that subshell
1371 and will not cause the original shell to exit a running function (see the
1372 while...read loop FAQ below).
1373 Functions defined with the function reserved word are treated differently
1375 in the following ways from functions defined with the () notation:
1376 · The $0 parameter is set to the name of the function (Bourne-style
1378 functions leave $0 untouched).
1379 · Parameter assignments preceding function calls are not kept in the
1381 shell environment (executing Bourne-style functions will keep assign‐
1382 ments).
1383 · OPTIND is saved/reset and restored on entry and exit from the func‐
1385 tion so getopts can be used properly both inside and outside the
1386 function (Bourne-style functions leave OPTIND untouched, so using
1387 getopts inside a function interferes with using getopts outside the
1388 function).
1389 · Shell options (set -o) have local scope, i.e. changes inside a func‐
1391 tion are reset upon its exit.
1392 In the future, the following differences may also be added:
1394 · A separate trap/signal environment will be used during the execution
1396 of functions. This will mean that traps set inside a function will
1397 not affect the shell's traps and signals that are not ignored in the
1398 shell (but may be trapped) will have their default effect in a func‐
1399 tion.
1400 · The EXIT trap, if set in a function, will be executed after the func‐
1402 tion returns.
1403 Command execution
1405 After evaluation of command-line arguments, redirections and parameter
1406 assignments, the type of command is determined: a special built-in com‐
1407 mand, a function, a normal builtin or the name of a file to execute found
1408 using the PATH parameter. The checks are made in the above order. Spe‐
1409 cial built-in commands differ from other commands in that the PATH param‐
1410 eter is not used to find them, an error during their execution can cause
1411 a non-interactive shell to exit, and parameter assignments that are spec‐
1412 ified before the command are kept after the command completes. Regular
1413 built-in commands are different only in that the PATH parameter is not
1414 used to find them.
1415 The original ksh and POSIX differ somewhat in which commands are consid‐
1417 ered special or regular.
1418 POSIX special built-in utilities:
1420 ., :, break, continue, eval, exec, exit, export, readonly, return, set,
1422 shift, times, trap, unset
1423 Additional mksh commands keeping assignments:
1425 global, source, typeset
1427 Builtins that are not special:
1429 [, alias, bg, bind, builtin, cat, cd, command, echo, false, fc, fg,
1431 getopts, jobs, kill, let, print, pwd, read, realpath, rename, sleep,
1432 suspend, test, true, ulimit, umask, unalias, wait, whence
1433 Once the type of command has been determined, any command-line parameter
1435 assignments are performed and exported for the duration of the command.
1436 The following describes the special and regular built-in commands and
1438 builtin-like reserved words:
1439 . file [arg ...]
1441 This is called the “dot” command. Execute the commands in file in
1442 the current environment. The file is searched for in the directo‐
1443 ries of PATH. If arguments are given, the positional parameters
1444 may be used to access them while file is being executed. If no
1445 arguments are given, the positional parameters are those of the
1446 environment the command is used in.
1447 : [...]
1449 The null command. Exit status is set to zero.
1450 [ expression ]
1452 See test.
1453 alias [-d | -t [-r] | +-x] [-p] [+] [name [=value] ...]
1455 Without arguments, alias lists all aliases. For any name without
1456 a value, the existing alias is listed. Any name with a value
1457 defines an alias; see Aliases above. [][A-Za-z0-9_!%,.@:-] are
1458 valid in names, except they may not begin with a hyphen-minus, and
1459 [[ is not a valid alias name.
1460 When listing aliases, one of two formats is used. Normally,
1462 aliases are listed as name=value, where value is quoted. If
1463 options were preceded with ‘+’, or a lone ‘+’ is given on the com‐
1464 mand line, only name is printed.
1465 The -d option causes directory aliases which are used in tilde
1467 expansion to be listed or set (see Tilde expansion above).
1468 If the -p option is used, each alias is prefixed with the string
1470 “alias ”.
1471 The -t option indicates that tracked aliases are to be listed/set
1473 (values specified on the command line are ignored for tracked
1474 aliases). The -r option indicates that all tracked aliases are to
1475 be reset.
1476 The -x option sets (+x clears) the export attribute of an alias,
1478 or, if no names are given, lists the aliases with the export
1479 attribute (exporting an alias has no effect).
1480 bg [job ...]
1482 Resume the specified stopped job(s) in the background. If no jobs
1483 are specified, %+ is assumed. See Job control below for more
1484 information.
1485 bind [-l]
1487 The current bindings are listed. If the -l flag is given, bind
1488 instead lists the names of the functions to which keys may be
1489 bound. See Emacs editing mode for more information.
1490 bind [-m] string=[substitute] ...
1492 bind string=[editing-command] ...
1493 The specified editing command is bound to the given string, which
1494 should consist of a control character optionally preceded by one
1495 of the two prefix characters and optionally succeeded by a tilde
1496 character. Future input of the string will cause the editing com‐
1497 mand to be immediately invoked. If the -m flag is given, the
1498 specified input string will afterwards be immediately replaced by
1499 the given substitute string which may contain editing commands but
1500 not other macros. If a tilde postfix is given, a tilde trailing
1501 the one or two prefices and the control character is ignored, any
1502 other trailing character will be processed afterwards.
1503 Control characters may be written using caret notation i.e. ^X
1505 represents Ctrl-X. The caret itself can be escaped by a back‐
1506 slash, which also escapes itself. Note that although only three
1507 prefix characters (usually ESC, ^X and NUL) are supported, some
1508 multi-character sequences can be supported.
1509 The following default bindings show how the arrow keys, the home,
1511 end and delete key on a BSD wsvt25, xterm-xfree86 or GNU screen
1512 terminal are bound (of course some escape sequences won't work out
1513 quite this nicely):
1514 bind '^X'=prefix-2
1516 bind '^[['=prefix-2
1517 bind '^XA'=up-history
1518 bind '^XB'=down-history
1519 bind '^XC'=forward-char
1520 bind '^XD'=backward-char
1521 bind '^X1~'=beginning-of-line
1522 bind '^X7~'=beginning-of-line
1523 bind '^XH'=beginning-of-line
1524 bind '^X4~'=end-of-line
1525 bind '^X8~'=end-of-line
1526 bind '^XF'=end-of-line
1527 bind '^X3~'=delete-char-forward
1528 break [level]
1530 Exit the levelth inner-most for, select, until or while loop.
1531 level defaults to 1.
1532 builtin [--] command [arg ...]
1534 Execute the built-in command command.
1535 \builtin command [arg ...]
1537 Same as builtin. Additionally acts as declaration utility for‐
1538 warder, i.e. this is a declaration utility (see Tilde expansion)
1539 iff command is a declaration utility.
1540 cat [-u] [file ...]
1542 Read files sequentially, in command line order, and write them to
1543 standard output. If a file is a single dash (“-”) or absent, read
1544 from standard input. For direct builtin calls, the POSIX -u
1545 option is supported as a no-op. For calls from shell, if any
1546 options are given, an external cat(1) utility is preferred over
1547 the builtin.
1548 cd [-L] [dir]
1550 cd -P [-e] [dir]
1551 chdir [-eLP] [dir]
1552 Set the working directory to dir. If the parameter CDPATH is set,
1553 it lists the search path for the directory containing dir. An
1554 unset or empty path means the current directory. If dir is found
1555 in any component of the CDPATH search path other than an unset or
1556 empty path, the name of the new working directory will be written
1557 to standard output. If dir is missing, the home directory HOME is
1558 used. If dir is “-”, the previous working directory is used (see
1559 the OLDPWD parameter).
1560 If the -L option (logical path) is used or if the physical option
1562 isn't set (see the set command below), references to “..” in dir
1563 are relative to the path used to get to the directory. If the -P
1564 option (physical path) is used or if the physical option is set,
1565 “..” is relative to the filesystem directory tree. The PWD and
1566 OLDPWD parameters are updated to reflect the current and old work‐
1567 ing directory, respectively. If the -e option is set for physical
1568 filesystem traversal and PWD could not be set, the exit code is 1;
1569 greater than 1 if an error occurred, 0 otherwise.
1570 cd [-eLP] old new
1572 chdir [-eLP] old new
1573 The string new is substituted for old in the current directory,
1574 and the shell attempts to change to the new directory.
1575 command [-pVv] cmd [arg ...]
1577 If neither the -v nor -V option is given, cmd is executed exactly
1578 as if command had not been specified, with two exceptions:
1579 firstly, cmd cannot be a shell function; and secondly, special
1580 built-in commands lose their specialness (i.e. redirection and
1581 utility errors do not cause the shell to exit, and command assign‐
1582 ments are not permanent). The declaration utility property is not
1583 reset.
1584 If the -p option is given, a default search path is used instead
1586 of the current value of PATH, the actual value of which is system
1587 dependent.
1588 If the -v option is given, instead of executing cmd, information
1590 about what would be executed is given (and the same is done for
1591 arg ...). For builtins, functions and keywords, their names are
1592 simply printed; for aliases, a command that defines them is
1593 printed; for utilities found by searching the PATH parameter, the
1594 full path of the command is printed. If no command is found (i.e.
1595 the path search fails), nothing is printed and command exits with
1596 a non-zero status. The -V option is like the -v option, except it
1597 is more verbose.
1598 continue [level]
1600 Jumps to the beginning of the levelth inner-most for, select,
1601 until or while loop. level defaults to 1.
1602 echo [-Een] [arg ...]
1604 Warning: this utility is not portable; use the Korn shell builtin
1605 print instead.
1606 Prints its arguments (separated by spaces) followed by a newline,
1608 to the standard output. The newline is suppressed if any of the
1609 arguments contain the backslash sequence “\c”. See the print com‐
1610 mand below for a list of other backslash sequences that are recog‐
1611 nised.
1612 The options are provided for compatibility with BSD shell scripts.
1614 The -n option suppresses the trailing newline, -e enables back‐
1615 slash interpretation (a no-op, since this is normally done), and
1616 -E suppresses backslash interpretation.
1617 If the posix or sh option is set or this is a direct builtin call
1619 or print -R, only the first argument is treated as an option, and
1620 only if it is exactly “-n”. Backslash interpretation is disabled.
1621 eval command ...
1623 The arguments are concatenated (with spaces between them) to form
1624 a single string which the shell then parses and executes in the
1625 current environment.
1626 exec [-a argv0] [-c] [command [arg ...]]
1628 The command is executed without forking, replacing the shell
1629 process. This is currently absolute, i.e. exec never returns,
1630 even if the command is not found. The -a option permits setting a
1631 different argv[0] value, and -c clears the environment before exe‐
1632 cuting the child process, except for the _ variable and direct
1633 assignments.
1634 If no command is given except for I/O redirection, the I/O redi‐
1636 rection is permanent and the shell is not replaced. Any file
1637 descriptors greater than 2 which are opened or dup(2)'d in this
1638 way are not made available to other executed commands (i.e. com‐
1639 mands that are not built-in to the shell). Note that the Bourne
1640 shell differs here; it does pass these file descriptors on.
1641 exit [status]
1643 The shell or subshell exits with the specified exit status. If
1644 status is not specified, the exit status is the current value of
1645 the $? parameter.
1646 export [-p] [parameter[=value]]
1648 Sets the export attribute of the named parameters. Exported
1649 parameters are passed in the environment to executed commands. If
1650 values are specified, the named parameters are also assigned.
1651 This is a declaration utility.
1652 If no parameters are specified, all parameters with the export
1654 attribute set are printed one per line; either their names, or, if
1655 a “-” with no option letter is specified, name=value pairs, or,
1656 with -p, export commands suitable for re-entry.
1657 false A command that exits with a non-zero status.
1659 fc [-e editor | -l [-n]] [-r] [first [last]]
1661 first and last select commands from the history. Commands can be
1662 selected by history number (negative numbers go backwards from the
1663 current, most recent, line) or a string specifying the most recent
1664 command starting with that string. The -l option lists the com‐
1665 mand on standard output, and -n inhibits the default command num‐
1666 bers. The -r option reverses the order of the list. Without -l,
1667 the selected commands are edited by the editor specified with the
1668 -e option or, if no -e is specified, the editor specified by the
1669 FCEDIT parameter (if this parameter is not set, /bin/ed is used),
1670 and then executed by the shell.
1671 fc -e - | -s [-g] [old=new] [prefix]
1673 Re-execute the selected command (the previous command by default)
1674 after performing the optional substitution of old with new. If -g
1675 is specified, all occurrences of old are replaced with new. The
1676 meaning of -e - and -s is identical: re-execute the selected com‐
1677 mand without invoking an editor. This command is usually accessed
1678 with the predefined: alias r='fc -e -'
1679 fg [job ...]
1681 Resume the specified job(s) in the foreground. If no jobs are
1682 specified, %+ is assumed. See Job control below for more informa‐
1683 tion.
1684 getopts optstring name [arg ...]
1686 Used by shell procedures to parse the specified arguments (or
1687 positional parameters, if no arguments are given) and to check for
1688 legal options. optstring contains the option letters that getopts
1689 is to recognise. If a letter is followed by a colon, the option
1690 is expected to have an argument. Options that do not take argu‐
1691 ments may be grouped in a single argument. If an option takes an
1692 argument and the option character is not the last character of the
1693 argument it is found in, the remainder of the argument is taken to
1694 be the option's argument; otherwise, the next argument is the
1695 option's argument.
1696 Each time getopts is invoked, it places the next option in the
1698 shell parameter name and the index of the argument to be processed
1699 by the next call to getopts in the shell parameter OPTIND. If the
1700 option was introduced with a ‘+’, the option placed in name is
1701 prefixed with a ‘+’. When an option requires an argument, getopts
1702 places it in the shell parameter OPTARG.
1703 When an illegal option or a missing option argument is encoun‐
1705 tered, a question mark or a colon is placed in name (indicating an
1706 illegal option or missing argument, respectively) and OPTARG is
1707 set to the option character that caused the problem. Furthermore,
1708 if optstring does not begin with a colon, a question mark is
1709 placed in name, OPTARG is unset, and an error message is printed
1710 to standard error.
1711 When the end of the options is encountered, getopts exits with a
1713 non-zero exit status. Options end at the first (non-option argu‐
1714 ment) argument that does not start with a ‘-’, or when a “--”
1715 argument is encountered.
1716 Option parsing can be reset by setting OPTIND to 1 (this is done
1718 automatically whenever the shell or a shell procedure is invoked).
1719 Warning: Changing the value of the shell parameter OPTIND to a
1721 value other than 1 or parsing different sets of arguments without
1722 resetting OPTIND may lead to unexpected results.
1723 global [+-aglpnrtUux] [-L[n] | -R[n] | -Z[n]] [-i[n]] [name [=value] ...]
1725 See typeset -g. Deprecated, will be removed from a future version
1726 of mksh.
1727 hash [-r] [name ...]
1729 Without arguments, any hashed executable command pathnames are
1730 listed. The -r option causes all hashed commands to be removed
1731 from the hash table. Each name is searched as if it were a com‐
1732 mand name and added to the hash table if it is an executable com‐
1733 mand.
1734 jobs [-lnp] [job ...]
1736 Display information about the specified job(s); if no jobs are
1737 specified, all jobs are displayed. The -n option causes informa‐
1738 tion to be displayed only for jobs that have changed state since
1739 the last notification. If the -l option is used, the process ID
1740 of each process in a job is also listed. The -p option causes
1741 only the process group of each job to be printed. See Job control
1742 below for the format of job and the displayed job.
1743 kill [-s signame | -signum | -signame] { job | pid | pgrp } ...
1745 Send the specified signal to the specified jobs, process IDs or
1746 process groups. If no signal is specified, the TERM signal is
1747 sent. If a job is specified, the signal is sent to the job's
1748 process group. See Job control below for the format of job.
1749 kill -l [exit-status ...]
1751 Print the signal name corresponding to exit-status. If no argu‐
1752 ments are specified, a list of all the signals with their numbers
1753 and a short description of each are printed.
1754 let [expression ...]
1756 Each expression is evaluated (see Arithmetic expressions above).
1757 If all expressions are successfully evaluated, the exit status is
1758 0 (1) if the last expression evaluated to non-zero (zero). If an
1759 error occurs during the parsing or evaluation of an expression,
1760 the exit status is greater than 1. Since expressions may need to
1761 be quoted, (( expr )) is syntactic sugar for:
1762 { \\builtin let 'expr'; }
1763 mknod [-m mode] name b|c major minor
1765 mknod [-m mode] name p
1766 Create a device special file. The file type may be b (block type
1767 device), c (character type device) or p (named pipe, FIFO). The
1768 file created may be modified according to its mode (via the -m
1769 option), major (major device number), and minor (minor device num‐
1770 ber). This is not normally part of mksh; however, distributors
1771 may have added this as builtin as a speed hack.
1772 print [-AcelNnprsu[n] | -R [-n]] [argument ...]
1774 Print the specified argument(s) on the standard output, separated
1775 by spaces, terminated with a newline. The escapes mentioned in
1776 Backslash expansion above, as well as “\c”, which is equivalent to
1777 using the -n option, are interpreted.
1778 The options are as follows:
1780 -A Each argument is arithmetically evaluated; the character
1782 corresponding to the resulting value is printed. Empty
1783 arguments separate input words.
1784 -c The output is printed columnised, line by line, similar to
1786 how the rs(1) utility, tab completion, the kill -l built-
1787 in utility and the select statement do.
1788 -e Restore backslash expansion after a previous -r.
1790 -l Change the output word separator to newline.
1792 -N Change the output word and line separator to ASCII NUL.
1794 -n Do not print the trailing line separator.
1796 -p Print to the co-process (see Co-processes above).
1798 -r Inhibit backslash expansion.
1800 -s Print to the history file instead of standard output.
1802 -u[n] Print to the file descriptor n (defaults to 1 if omitted)
1804 instead of standard output.
1805 The -R option mostly emulates the BSD echo(1) command which does
1807 not expand backslashes and interprets its first argument as option
1808 only if it is exactly “-n” (to suppress the trailing newline).
1809 pwd [-LP]
1811 Print the present working directory. If the -L option is used or
1812 if the physical option isn't set (see the set command below), the
1813 logical path is printed (i.e. the path used to cd to the current
1814 directory). If the -P option (physical path) is used or if the
1815 physical option is set, the path determined from the filesystem
1816 (by following “..” directories to the root directory) is printed.
1817 read [-A | -a] [-d x] [-N z | -n z] [-p | -u[n]] [-t n] [-rs] [p ...]
1819 Reads a line of input, separates the input into fields using the
1820 IFS parameter (see Substitution above), and assigns each field to
1821 the specified parameters p. If no parameters are specified, the
1822 REPLY parameter is used to store the result. With the -A and -a
1823 options, only no or one parameter is accepted. If there are more
1824 parameters than fields, the extra parameters are set to the empty
1825 string or 0; if there are more fields than parameters, the last
1826 parameter is assigned the remaining fields (including the word
1827 separators).
1828 The options are as follows:
1830 -A Store the result into the parameter p (or REPLY) as array
1832 of words.
1833 -a Store the result without word splitting into the parameter
1835 p (or REPLY) as array of characters (wide characters if the
1836 utf8-mode option is enacted, octets otherwise); the code‐
1837 points are encoded as decimal numbers by default.
1838 -d x Use the first byte of x, NUL if empty, instead of the ASCII
1840 newline character as input line delimiter.
1841 -N z Instead of reading till end-of-line, read exactly z bytes.
1843 Upon EOF, a partial read is returned with exit status 1.
1844 After timeout, a partial read is returned with an exit sta‐
1845 tus as if SIGALRM were caught.
1846 -n z Instead of reading till end-of-line, read up to z bytes but
1848 return as soon as any bytes are read, e.g. from a slow ter‐
1849 minal device, or if EOF or a timeout occurs.
1850 -p Read from the currently active co-process, see Co-processes
1852 above for details on this.
1853 -u[n] Read from the file descriptor n (defaults to 0, i.e. stan‐
1855 dard input). The argument must immediately follow the
1856 option character.
1857 -t n Interrupt reading after n seconds (specified as positive
1859 decimal value with an optional fractional part). The exit
1860 status of read is the same as if SIGALRM were caught if the
1861 timeout occurred, but partial reads may still be returned.
1862 -r Normally, the ASCII backslash character escapes the special
1864 meaning of the following character and is stripped from the
1865 input; read does not stop when encountering a backslash-
1866 newline sequence and does not store that newline in the
1867 result. This option enables raw mode, in which backslashes
1868 are not processed.
1869 -s The input line is saved to the history.
1871 If the input is a terminal, both the -N and -n options set it into
1873 raw mode; they read an entire file if -1 is passed as z argument.
1874 The first parameter may have a question mark and a string appended
1876 to it, in which case the string is used as a prompt (printed to
1877 standard error before any input is read) if the input is a tty(4)
1878 (e.g. read nfoo?'number of foos: ').
1879 If no input is read or a timeout occurred, read exits with a non-
1881 zero status.
1882 readonly [-p] [parameter [=value] ...]
1884 Sets the read-only attribute of the named parameters. This is a
1885 declaration utility. If values are given, parameters are set to
1886 them before setting the attribute. Once a parameter is made read-
1887 only, it cannot be unset and its value cannot be changed.
1888 If no parameters are specified, the names of all parameters with
1890 the read-only attribute are printed one per line, unless the -p
1891 option is used, in which case readonly commands defining all read-
1892 only parameters, including their values, are printed.
1893 realpath [--] name
1895 Prints the resolved absolute pathname corresponding to name. If
1896 name ends with a slash (‘/’), it's also checked for existence and
1897 whether it is a directory; otherwise, realpath returns 0 if the
1898 pathname either exists or can be created immediately, i.e. all but
1899 the last component exist and are directories. For calls from the
1900 shell, if any options are given, an external realpath(1) utility
1901 is preferred over the builtin.
1902 rename [--] from to
1904 Renames the file from to to. Both must be complete pathnames and
1905 on the same device. An external utility is preferred over this
1906 builtin, which is intended for emergency situations (where /bin/mv
1907 becomes unusable) and directly calls rename(2).
1908 return [status]
1910 Returns from a function or . script, with exit status status. If
1911 no status is given, the exit status of the last executed command
1912 is used. If used outside of a function or . script, it has the
1913 same effect as exit. Note that mksh treats both profile and ENV
1914 files as . scripts, while the original Korn shell only treats pro‐
1915 files as . scripts.
1916 set [+-abCefhiklmnprsUuvXx] [+-o option] [+-A name] [--] [arg ...]
1918 The set command can be used to set (-) or clear (+) shell options,
1919 set the positional parameters, or set an array parameter. Options
1920 can be changed using the +-o option syntax, where option is the
1921 long name of an option, or using the +-letter syntax, where letter
1922 is the option's single letter name (not all options have a single
1923 letter name). The following table lists both option letters (if
1924 they exist) and long names along with a description of what the
1925 option does:
1926 -A name
1928 Sets the elements of the array parameter name to arg ... If
1929 -A is used, the array is reset (i.e. emptied) first; if +A is
1930 used, the first N elements are set (where N is the number of
1931 arguments); the rest are left untouched.
1932 An alternative syntax for the command set -A foo -- a b c
1934 which is compatible to GNU bash and also supported by AT&T
1935 UNIX ksh93 is: foo=(a b c); foo+=(d e)
1936 -a | -o allexport
1938 All new parameters are created with the export attribute.
1939 -b | -o notify
1941 Print job notification messages asynchronously, instead of
1942 just before the prompt. Only used if job control is enabled
1943 (-m).
1944 -C | -o noclobber
1946 Prevent > redirection from overwriting existing files.
1947 Instead, >| must be used to force an overwrite. Note that
1948 this is not safe to use for creation of temporary files or
1949 lockfiles due to a TOCTOU in a check allowing one to redirect
1950 output to /dev/null or other device files even in noclobber
1951 mode.
1952 -e | -o errexit
1954 Exit (after executing the ERR trap) as soon as an error
1955 occurs or a command fails (i.e. exits with a non-zero sta‐
1956 tus). This does not apply to commands whose exit status is
1957 explicitly tested by a shell construct such as if, until,
1958 while or ! statements. For && or ||, only the status of the
1959 last command is tested.
1960 -f | -o noglob
1962 Do not expand file name patterns.
1963 -h | -o trackall
1965 Create tracked aliases for all executed commands (see Aliases
1966 above). Enabled by default for non-interactive shells.
1967 -i | -o interactive
1969 The shell is an interactive shell. This option can only be
1970 used when the shell is invoked. See above for a description
1971 of what this means.
1972 -k | -o keyword
1974 Parameter assignments are recognised anywhere in a command.
1975 -l | -o login
1977 The shell is a login shell. This option can only be used
1978 when the shell is invoked. See above for a description of
1979 what this means.
1980 -m | -o monitor
1982 Enable job control (default for interactive shells).
1983 -n | -o noexec
1985 Do not execute any commands. Useful for checking the syntax
1986 of scripts (ignored if interactive).
1987 -p | -o privileged
1989 The shell is a privileged shell. It is set automatically if,
1990 when the shell starts, the real UID or GID does not match the
1991 effective UID (EUID) or GID (EGID), respectively. See above
1992 for a description of what this means.
1993 -r | -o restricted
1995 The shell is a restricted shell. This option can only be
1996 used when the shell is invoked. See above for a description
1997 of what this means.
1998 -s | -o stdin
2000 If used when the shell is invoked, commands are read from
2001 standard input. Set automatically if the shell is invoked
2002 with no arguments.
2003 When -s is used with the set command it causes the specified
2005 arguments to be sorted before assigning them to the posi‐
2006 tional parameters (or to array name, if -A is used).
2007 -U | -o utf8-mode
2009 Enable UTF-8 support in the Emacs editing mode and internal
2010 string handling functions. This flag is disabled by default,
2011 but can be enabled by setting it on the shell command line;
2012 is enabled automatically for interactive shells if requested
2013 at compile time, your system supports setlocale(LC_CTYPE, "")
2014 and optionally nl_langinfo(CODESET), or the LC_ALL, LC_CTYPE
2015 or LANG environment variables, and at least one of these
2016 returns something that matches “UTF-8” or “utf8” case-insen‐
2017 sitively; for direct builtin calls depending on the aforemen‐
2018 tioned environment variables; or for stdin or scripts, if the
2019 input begins with a UTF-8 Byte Order Mark.
2020 In near future, locale tracking will be implemented, which
2022 means that set -+U is changed whenever one of the POSIX
2023 locale-related environment variables changes.
2024 -u | -o nounset
2026 Referencing of an unset parameter, other than “$@” or “$*”,
2027 is treated as an error, unless one of the ‘-’, ‘+’ or ‘=’
2028 modifiers is used.
2029 -v | -o verbose
2031 Write shell input to standard error as it is read.
2032 -X | -o markdirs
2034 Mark directories with a trailing ‘/’ during file name genera‐
2035 tion.
2036 -x | -o xtrace
2038 Print command trees when they are executed, preceded by the
2039 value of PS4.
2040 -o bgnice
2042 Background jobs are run with lower priority.
2043 -o braceexpand
2045 Enable brace expansion (a.k.a. alternation). This is enabled
2046 by default.
2047 -o emacs
2049 Enable BRL emacs-like command-line editing (interactive
2050 shells only); see Emacs editing mode.
2051 -o gmacs
2053 Enable gmacs-like command-line editing (interactive shells
2054 only). Currently identical to emacs editing except that
2055 transpose-chars (^T) acts slightly differently.
2056 -o ignoreeof
2058 The shell will not (easily) exit when end-of-file is read;
2059 exit must be used. To avoid infinite loops, the shell will
2060 exit if EOF is read 13 times in a row.
2061 -o inherit-xtrace
2063 Do not reset -o xtrace upon entering functions. This is
2064 enabled by default.
2065 -o nohup
2067 Do not kill running jobs with a SIGHUP signal when a login
2068 shell exits. Currently set by default, but this may change
2069 in the future to be compatible with AT&T UNIX ksh, which
2070 doesn't have this option, but does send the SIGHUP signal.
2071 -o nolog
2073 No effect. In the original Korn shell, this prevents func‐
2074 tion definitions from being stored in the history file.
2075 -o physical
2077 Causes the cd and pwd commands to use “physical” (i.e. the
2078 filesystem's) “..” directories instead of “logical” directo‐
2079 ries (i.e. the shell handles “..”, which allows the user to
2080 be oblivious of symbolic links to directories). Clear by
2081 default. Note that setting this option does not affect the
2082 current value of the PWD parameter; only the cd command
2083 changes PWD. See the cd and pwd commands above for more
2084 details.
2085 -o pipefail
2087 Make the exit status of a pipeline (before logically comple‐
2088 menting) the rightmost non-zero errorlevel, or zero if all
2089 commands exited with zero.
2090 -o posix
2092 Behave closer to the standards (see POSIX mode for details).
2093 Automatically enabled if the basename of the shell invocation
2094 begins with “sh” and this autodetection feature is compiled
2095 in (not in MirBSD). As a side effect, setting this flag
2096 turns off the braceexpand and utf8-mode flags, which can be
2097 turned back on manually, and sh mode (unless both are enabled
2098 at the same time).
2099 -o sh
2101 Enable /bin/sh (kludge) mode (see SH mode). Automatically
2102 enabled if the basename of the shell invocation begins with
2103 “sh” and this autodetection feature is compiled in (not in
2104 MirBSD). As a side effect, setting this flag turns off
2105 braceexpand mode, which can be turned back on manually, and
2106 posix mode (unless both are enabled at the same time).
2107 -o vi
2109 Enable vi(1)-like command-line editing (interactive shells
2110 only). See Vi editing mode for documentation and limita‐
2111 tions.
2112 -o vi-esccomplete
2114 In vi command-line editing, do command and file name comple‐
2115 tion when escape (^[) is entered in command mode.
2116 -o vi-tabcomplete
2118 In vi command-line editing, do command and file name comple‐
2119 tion when tab (^I) is entered in insert mode. This is the
2120 default.
2121 -o viraw
2123 No effect. In the original Korn shell, unless viraw was set,
2124 the vi command-line mode would let the tty(4) driver do the
2125 work until ESC (^[) was entered. mksh is always in viraw
2126 mode.
2127 These options can also be used upon invocation of the shell. The
2129 current set of options (with single letter names) can be found in
2130 the parameter “$-”. set -o with no option name will list all the
2131 options and whether each is on or off; set +o will print the long
2132 names of all options that are currently on. In a future version,
2133 set +o will behave POSIX compliant and print commands to restore
2134 the current options instead.
2135 Remaining arguments, if any, are positional parameters and are
2137 assigned, in order, to the positional parameters (i.e. $1, $2,
2138 etc.). If options end with “--” and there are no remaining argu‐
2139 ments, all positional parameters are cleared. If no options or
2140 arguments are given, the values of all names are printed. For
2141 unknown historical reasons, a lone “-” option is treated specially
2142 – it clears both the -v and -x options.
2143 shift [number]
2145 The positional parameters number+1, number+2, etc. are renamed to
2146 1, 2, etc. number defaults to 1.
2147 sleep seconds
2149 Suspends execution for a minimum of the seconds specified as posi‐
2150 tive decimal value with an optional fractional part. Signal
2151 delivery may continue execution earlier.
2152 source file [arg ...]
2154 Like . (“dot”), except that the current working directory is
2155 appended to the search path (GNU bash extension).
2156 suspend
2158 Stops the shell as if it had received the suspend character from
2159 the terminal. It is not possible to suspend a login shell unless
2160 the parent process is a member of the same terminal session but is
2161 a member of a different process group. As a general rule, if the
2162 shell was started by another shell or via su(1), it can be sus‐
2163 pended.
2164 test expression
2166 [ expression ]
2167 test evaluates the expression and returns zero status if true, 1
2168 if false, or greater than 1 if there was an error. It is normally
2169 used as the condition command of if and while statements. Sym‐
2170 bolic links are followed for all file expressions except -h and
2171 -L.
2172 The following basic expressions are available:
2174 -a file file exists.
2176 -b file file is a block special device.
2178 -c file file is a character special device.
2180 -d file file is a directory.
2182 -e file file exists.
2184 -f file file is a regular file.
2186 -G file file's group is the shell's effective group ID.
2188 -g file file's mode has the setgid bit set.
2190 -H file file is a context dependent directory (only
2192 useful on HP-UX).
2193 -h file file is a symbolic link.
2195 -k file file's mode has the sticky(8) bit set.
2197 -L file file is a symbolic link.
2199 -O file file's owner is the shell's effective user ID.
2201 -p file file is a named pipe (FIFO).
2203 -r file file exists and is readable.
2205 -S file file is a unix(4)-domain socket.
2207 -s file file is not empty.
2209 -t fd File descriptor fd is a tty(4) device.
2211 -u file file's mode has the setuid bit set.
2213 -w file file exists and is writable.
2215 -x file file exists and is executable.
2217 file1 -nt file2 file1 is newer than file2 or file1 exists and
2219 file2 does not.
2220 file1 -ot file2 file1 is older than file2 or file2 exists and
2222 file1 does not.
2223 file1 -ef file2 file1 is the same file as file2.
2225 string string has non-zero length.
2227 -n string string is not empty.
2229 -z string string is empty.
2231 -v name The shell parameter name is set.
2233 -o option Shell option is set (see the set command above
2235 for a list of options). As a non-standard
2236 extension, if the option starts with a ‘!’, the
2237 test is negated; the test always fails if
2238 option doesn't exist (so [ -o foo -o -o !foo ]
2239 returns true if and only if option foo exists).
2240 The same can be achieved with [ -o ?foo ] like
2241 in AT&T UNIX ksh93. option can also be the
2242 short flag led by either ‘-’ or ‘+’ (no logical
2243 negation), for example “-x” or “+x” instead of
2244 “xtrace”.
2245 string = string Strings are equal.
2247 string == string Strings are equal.
2249 string > string First string operand is greater than second
2251 string operand.
2252 string < string First string operand is less than second string
2254 operand.
2255 string != string Strings are not equal.
2257 number -eq number Numbers compare equal.
2259 number -ne number Numbers compare not equal.
2261 number -ge number Numbers compare greater than or equal.
2263 number -gt number Numbers compare greater than.
2265 number -le number Numbers compare less than or equal.
2267 number -lt number Numbers compare less than.
2269 The above basic expressions, in which unary operators have prece‐
2271 dence over binary operators, may be combined with the following
2272 operators (listed in increasing order of precedence):
2273 expr -o expr Logical OR.
2275 expr -a expr Logical AND.
2276 ! expr Logical NOT.
2277 ( expr ) Grouping.
2278 Note that a number actually may be an arithmetic expression, such
2280 as a mathematical term or the name of an integer variable:
2281 x=1; [ "x" -eq 1 ] evaluates to true
2283 Note that some special rules are applied (courtesy of POSIX) if
2285 the number of arguments to test or inside the brackets [ ... ] is
2286 less than five: if leading “!” arguments can be stripped such that
2287 only one to three arguments remain, then the lowered comparison is
2288 executed; (thanks to XSI) parentheses \( ... \) lower four- and
2289 three-argument forms to two- and one-argument forms, respectively;
2290 three-argument forms ultimately prefer binary operations, followed
2291 by negation and parenthesis lowering; two- and four-argument forms
2292 prefer negation followed by parenthesis; the one-argument form
2293 always implies -n.
2294 Note: A common mistake is to use “if [ $foo = bar ]” which fails
2296 if parameter “foo” is empty or unset, if it has embedded spaces
2297 (i.e. IFS octets) or if it is a unary operator like “!” or “-n”.
2298 Use tests like “if [ x"$foo" = x"bar" ]” instead, or the double-
2299 bracket operator “if [[ $foo = bar ]]” or, to avoid pattern match‐
2300 ing (see [[ above): “if [[ $foo = "$bar" ]]”
2301 The [[ ... ]] construct is not only more secure to use but also
2303 often faster.
2304 time [-p] [pipeline]
2306 If a pipeline is given, the times used to execute the pipeline are
2307 reported. If no pipeline is given, then the user and system time
2308 used by the shell itself, and all the commands it has run since it
2309 was started, are reported. The times reported are the real time
2310 (elapsed time from start to finish), the user CPU time (time spent
2311 running in user mode), and the system CPU time (time spent running
2312 in kernel mode). Times are reported to standard error; the format
2313 of the output is:
2314 0m0.00s real 0m0.00s user 0m0.00s system
2316 If the -p option is given the output is slightly longer:
2318 real 0.00
2320 user 0.00
2321 sys 0.00
2322 It is an error to specify the -p option unless pipeline is a sim‐
2324 ple command.
2325 Simple redirections of standard error do not affect the output of
2327 the time command:
2328 $ time sleep 1 2>afile
2330 $ { time sleep 1; } 2>afile
2331 Times for the first command do not go to “afile”, but those of the
2333 second command do.
2334 times Print the accumulated user and system times used both by the shell
2336 and by processes that the shell started which have exited. The
2337 format of the output is:
2338 0m0.00s 0m0.00s
2340 0m0.00s 0m0.00s
2341 trap n [signal ...]
2343 If the first operand is a decimal unsigned integer, this resets
2344 all specified signals to the default action, i.e. is the same as
2345 calling trap with a dash (“-”) as handler, followed by the argu‐
2346 ments (n [signal ...]), all of which are treated as signals.
2347 trap [handler signal ...]
2349 Sets a trap handler that is to be executed when any of the speci‐
2350 fied signals are received. handler is either an empty string,
2351 indicating the signals are to be ignored, a dash (“-”), indicating
2352 that the default action is to be taken for the signals (see
2353 signal(3)), or a string containing shell commands to be executed
2354 at the first opportunity (i.e. when the current command completes
2355 or before printing the next PS1 prompt) after receipt of one of
2356 the signals. signal is the name of a signal (e.g. PIPE or ALRM)
2357 or the number of the signal (see the kill -l command above).
2358 There are two special signals: EXIT (also known as 0), which is
2360 executed when the shell is about to exit, and ERR, which is exe‐
2361 cuted after an error occurs; an error is something that would
2362 cause the shell to exit if the set -e or set -o errexit option
2363 were set. EXIT handlers are executed in the environment of the
2364 last executed command.
2365 Note that, for non-interactive shells, the trap handler cannot be
2367 changed for signals that were ignored when the shell started.
2368 With no arguments, the current state of the traps that have been
2370 set since the shell started is shown as a series of trap commands.
2371 Note that the output of trap cannot be usefully piped to another
2372 process (an artifact of the fact that traps are cleared when sub‐
2373 processes are created).
2374 The original Korn shell's DEBUG trap and the handling of ERR and
2376 EXIT traps in functions are not yet implemented.
2377 true A command that exits with a zero value.
2379 typeset [+-aglpnrtUux] [-L[n] | -R[n] | -Z[n]] [-i[n]] [name [=value]
2381 ...]
2382 typeset -f [-tux] [name ...]
2383 Display or set parameter attributes. This is a declaration util‐
2384 ity. With no name arguments, parameter attributes are displayed;
2385 if no options are used, the current attributes of all parameters
2386 are printed as typeset commands; if an option is given (or “-”
2387 with no option letter), all parameters and their values with the
2388 specified attributes are printed; if options are introduced with
2389 ‘+’, parameter values are not printed.
2390 If name arguments are given, the attributes of the named parame‐
2392 ters are set (-) or cleared (+); inside a function, this will
2393 cause the parameters to be created (with no value) in the local
2394 scope (but see -g). Values for parameters may optionally be spec‐
2395 ified. For name[*], the change affects all elements of the array,
2396 and no value may be specified.
2397 When -f is used, typeset operates on the attributes of functions.
2399 As with parameters, if no name arguments are given, functions are
2400 listed with their values (i.e. definitions) unless options are
2401 introduced with ‘+’, in which case only the function names are
2402 reported.
2403 -a Indexed array attribute.
2405 -f Function mode. Display or set functions and their
2407 attributes, instead of parameters.
2408 -g Do not cause named parameters to be created in the local
2410 scope when called inside a function.
2411 -i[n] Integer attribute. n specifies the base to use when dis‐
2413 playing the integer (if not specified, the base given in
2414 the first assignment is used). Parameters with this
2415 attribute may be assigned values containing arithmetic
2416 expressions.
2417 -L[n] Left justify attribute. n specifies the field width. If
2419 n is not specified, the current width of a parameter (or
2420 the width of its first assigned value) is used. Leading
2421 whitespace (and zeros, if used with the -Z option) is
2422 stripped. If necessary, values are either truncated or
2423 space padded to fit the field width.
2424 -l Lower case attribute. All upper case ASCII characters in
2426 values are converted to lower case. (In the original Korn
2427 shell, this parameter meant “long integer” when used with
2428 the -i option.)
2429 -n Create a bound variable (name reference): any access to
2431 the variable name will access the variable value in the
2432 current scope (this is different from AT&T UNIX ksh93!)
2433 instead. Also different from AT&T UNIX ksh93 is that
2434 value is lazily evaluated at the time name is accessed.
2435 This can be used by functions to access variables whose
2436 names are passed as parameters, instead of using eval.
2437 -p Print complete typeset commands that can be used to re-
2439 create the attributes and values of parameters.
2440 -R[n] Right justify attribute. n specifies the field width. If
2442 n is not specified, the current width of a parameter (or
2443 the width of its first assigned value) is used. Trailing
2444 whitespace is stripped. If necessary, values are either
2445 stripped of leading characters or space padded to make
2446 them fit the field width.
2447 -r Read-only attribute. Parameters with this attribute may
2449 not be assigned to or unset. Once this attribute is set,
2450 it cannot be turned off.
2451 -t Tag attribute. Has no meaning to the shell; provided for
2453 application use.
2454 For functions, -t is the trace attribute. When functions
2456 with the trace attribute are executed, the xtrace (-x)
2457 shell option is temporarily turned on.
2458 -U Unsigned integer attribute. Integers are printed as
2460 unsigned values (combine with the -i option). This option
2461 is not in the original Korn shell.
2462 -u Upper case attribute. All lower case ASCII characters in
2464 values are converted to upper case. (In the original Korn
2465 shell, this parameter meant “unsigned integer” when used
2466 with the -i option which meant upper case letters would
2467 never be used for bases greater than 10. See the -U
2468 option.)
2469 For functions, -u is the undefined attribute. See
2471 Functions above for the implications of this.
2472 -x Export attribute. Parameters (or functions) are placed in
2474 the environment of any executed commands. Exported func‐
2475 tions are not yet implemented.
2476 -Z[n] Zero fill attribute. If not combined with -L, this is the
2478 same as -R, except zero padding is used instead of space
2479 padding. For integers, the number instead of the base is
2480 padded.
2481 If any of the -i, -L, -l, -R, -U, -u or -Z options are changed,
2483 all others from this set are cleared, unless they are also given
2484 on the same command line.
2485 ulimit [-aBCcdefHilMmnOPpqrSsTtVvw] [value]
2487 Display or set process limits. If no options are used, the file
2488 size limit (-f) is assumed. value, if specified, may be either an
2489 arithmetic expression or the word “unlimited”. The limits affect
2490 the shell and any processes created by the shell after a limit is
2491 imposed. Note that some systems may not allow limits to be
2492 increased once they are set. Also note that the types of limits
2493 available are system dependent – some systems have only the -f
2494 limit, or not even that, or can set only the soft limits
2495 -a Display all limits; unless -H is used, soft limits are dis‐
2497 played.
2498 -B n Set the socket buffer size to n kibibytes.
2500 -C n Set the number of cached threads to n.
2502 -c n Impose a size limit of n blocks on the size of core dumps.
2504 -d n Impose a size limit of n kibibytes on the size of the data
2506 area.
2507 -e n Set the maximum niceness to n.
2509 -f n Impose a size limit of n blocks on files written by the
2511 shell and its child processes (files of any size may be
2512 read).
2513 -H Set the hard limit only (the default is to set both hard
2515 and soft limits).
2516 -i n Set the number of pending signals to n.
2518 -l n Impose a limit of n kibibytes on the amount of locked
2520 (wired) physical memory.
2521 -M n Set the AIO locked memory to n kibibytes.
2523 -m n Impose a limit of n kibibytes on the amount of physical
2525 memory used.
2526 -n n Impose a limit of n file descriptors that can be open at
2528 once.
2529 -O n Set the number of AIO operations to n.
2531 -P n Limit the number of threads per process to n.
2533 -p n Impose a limit of n processes that can be run by the user
2535 at any one time.
2536 -q n Limit the size of POSIX message queues to n bytes.
2538 -r n Set the maximum real-time priority to n.
2540 -S Set the soft limit only (the default is to set both hard
2542 and soft limits).
2543 -s n Impose a size limit of n kibibytes on the size of the stack
2545 area.
2546 -T n Impose a time limit of n real seconds to be used by each
2548 process.
2549 -t n Impose a time limit of n CPU seconds spent in user mode to
2551 be used by each process.
2552 -V n Set the number of vnode monitors on Haiku to n.
2554 -v n Impose a limit of n kibibytes on the amount of virtual mem‐
2556 ory (address space) used.
2557 -w n Impose a limit of n kibibytes on the amount of swap space
2559 used.
2560 As far as ulimit is concerned, a block is 512 bytes.
2562 umask [-S] [mask]
2564 Display or set the file permission creation mask or umask (see
2565 umask(2)). If the -S option is used, the mask displayed or set is
2566 symbolic; otherwise, it is an octal number.
2567 Symbolic masks are like those used by chmod(1). When used, they
2569 describe what permissions may be made available (as opposed to
2570 octal masks in which a set bit means the corresponding bit is to
2571 be cleared). For example, “ug=rwx,o=” sets the mask so files will
2572 not be readable, writable or executable by “others”, and is equiv‐
2573 alent (on most systems) to the octal mask “007”.
2574 unalias [-adt] [name ...]
2576 The aliases for the given names are removed. If the -a option is
2577 used, all aliases are removed. If the -t or -d options are used,
2578 the indicated operations are carried out on tracked or directory
2579 aliases, respectively.
2580 unset [-fv] parameter ...
2582 Unset the named parameters (-v, the default) or functions (-f).
2583 With parameter[*], attributes are kept, only values are unset.
2584 The exit status is non-zero if any of the parameters have the
2586 read-only attribute set, zero otherwise.
2587 wait [job ...]
2589 Wait for the specified job(s) to finish. The exit status of wait
2590 is that of the last specified job; if the last job is killed by a
2591 signal, the exit status is 128 + the number of the signal (see
2592 kill -l exit-status above); if the last specified job can't be
2593 found (because it never existed or had already finished), the exit
2594 status of wait is 127. See Job control below for the format of
2595 job. wait will return if a signal for which a trap has been set
2596 is received or if a SIGHUP, SIGINT or SIGQUIT signal is received.
2597 If no jobs are specified, wait waits for all currently running
2599 jobs (if any) to finish and exits with a zero status. If job mon‐
2600 itoring is enabled, the completion status of jobs is printed (this
2601 is not the case when jobs are explicitly specified).
2602 whence [-pv] [name ...]
2604 Without the -v option, it is the same as command -v, except
2605 aliases are not printed as alias command. With the -v option, it
2606 is exactly the same as command -V. In either case, the -p option
2607 differs: the search path is not affected in whence, but the search
2608 is restricted to the path.
2609 Job control
2611 Job control refers to the shell's ability to monitor and control jobs
2612 which are processes or groups of processes created for commands or pipe‐
2613 lines. At a minimum, the shell keeps track of the status of the back‐
2614 ground (i.e. asynchronous) jobs that currently exist; this information
2615 can be displayed using the jobs commands. If job control is fully
2616 enabled (using set -m or set -o monitor), as it is for interactive
2617 shells, the processes of a job are placed in their own process group.
2618 Foreground jobs can be stopped by typing the suspend character from the
2619 terminal (normally ^Z), jobs can be restarted in either the foreground or
2620 background using the fg and bg commands, and the state of the terminal is
2621 saved or restored when a foreground job is stopped or restarted, respec‐
2622 tively.
2623 Note that only commands that create processes (e.g. asynchronous com‐
2625 mands, subshell commands and non-built-in, non-function commands) can be
2626 stopped; commands like read cannot be.
2627 When a job is created, it is assigned a job number. For interactive
2629 shells, this number is printed inside “[...]”, followed by the process
2630 IDs of the processes in the job when an asynchronous command is run. A
2631 job may be referred to in the bg, fg, jobs, kill and wait commands either
2632 by the process ID of the last process in the command pipeline (as stored
2633 in the $! parameter) or by prefixing the job number with a percent sign
2634 (‘%’). Other percent sequences can also be used to refer to jobs:
2635 %+ | %% | % The most recently stopped job or, if there are no stopped
2637 jobs, the oldest running job.
2638 %- The job that would be the %+ job if the latter did not
2640 exist.
2641 %n The job with job number n.
2643 %?string The job with its command containing the string string (an
2645 error occurs if multiple jobs are matched).
2646 %string The job with its command starting with the string string
2648 (an error occurs if multiple jobs are matched).
2649 When a job changes state (e.g. a background job finishes or foreground
2651 job is stopped), the shell prints the following status information:
2652 [number] flag status command
2654 where...
2656 number is the job number of the job;
2658 flag is the ‘+’ or ‘-’ character if the job is the %+ or %- job,
2660 respectively, or space if it is neither;
2661 status indicates the current state of the job and can be:
2663 Done [number]
2665 The job exited. number is the exit status of the job
2666 which is omitted if the status is zero.
2667 Running The job has neither stopped nor exited (note that
2669 running does not necessarily mean consuming CPU time
2670 – the process could be blocked waiting for some
2671 event).
2672 Stopped [signal]
2674 The job was stopped by the indicated signal (if no
2675 signal is given, the job was stopped by SIGTSTP).
2676 signal-description [“core dumped”]
2678 The job was killed by a signal (e.g. memory fault,
2679 hangup); use kill -l for a list of signal descrip‐
2680 tions. The “core dumped” message indicates the
2681 process created a core file.
2682 command is the command that created the process. If there are multiple
2684 processes in the job, each process will have a line showing its
2685 command and possibly its status, if it is different from the
2686 status of the previous process.
2687 When an attempt is made to exit the shell while there are jobs in the
2689 stopped state, the shell warns the user that there are stopped jobs and
2690 does not exit. If another attempt is immediately made to exit the shell,
2691 the stopped jobs are sent a SIGHUP signal and the shell exits. Simi‐
2692 larly, if the nohup option is not set and there are running jobs when an
2693 attempt is made to exit a login shell, the shell warns the user and does
2694 not exit. If another attempt is immediately made to exit the shell, the
2695 running jobs are sent a SIGHUP signal and the shell exits.
2696 POSIX mode
2698 Entering set -o posix mode will cause mksh to behave even more POSIX com‐
2699 pliant in places where the defaults or opinions differ. Note that mksh
2700 will still operate with unsigned 32-bit arithmetic; use lksh if arith‐
2701 metic on the host long data type, complete with ISO C Undefined Behav‐
2702 iour, is required; refer to the lksh(1) manual page for details. Most
2703 other historic, AT&T UNIX ksh-compatible or opinionated differences can
2704 be disabled by using this mode; these are:
2705 · The incompatible GNU bash I/O redirection &>file is not supported.
2707 · File descriptors created by I/O redirections are inherited by child
2709 processes.
2710 · Numbers with a leading digit zero are interpreted as octal.
2712 · The echo builtin does not interpret backslashes and only supports the
2714 exact option -n.
2715 · Alias expansion with a trailing space only reruns on command words.
2717 · Tilde expansion follows POSIX instead of Korn shell rules.
2719 · The exit status of fg is always 0.
2721 · kill -l only lists signal names, all in one line.
2723 · getopts does not accept options with a leading ‘+’.
2725 · exec skips builtins, functions and other commands and uses a PATH
2727 search to determine the utility to execute.
2728 SH mode
2730 Compatibility mode; intended for use with legacy scripts that cannot eas‐
2731 ily be fixed; the changes are as follows:
2732 · The incompatible GNU bash I/O redirection &>file is not supported.
2734 · File descriptors created by I/O redirections are inherited by child
2736 processes.
2737 · The echo builtin does not interpret backslashes and only supports the
2739 exact option -n, unless built with -DMKSH_MIDNIGHTBSD01ASH_COMPAT.
2740 · The substitution operations ${x#pat}, ${x##pat}, ${x%pat}, and
2742 ${x%%pat} wrongly do not require a parenthesis to be escaped and do
2743 not parse extglobs.
2744 · The getopt construct from lksh(1) passes through the errorlevel.
2746 · sh -c eats a leading -- if built with -DMKSH_MIDNIGHTBSD01ASH_COMPAT.
2748 Interactive input line editing
2750 The shell supports three modes of reading command lines from a tty(4) in
2751 an interactive session, controlled by the emacs, gmacs and vi options (at
2752 most one of these can be set at once). The default is emacs. Editing
2753 modes can be set explicitly using the set built-in. If none of these
2754 options are enabled, the shell simply reads lines using the normal tty(4)
2755 driver. If the emacs or gmacs option is set, the shell allows emacs-like
2756 editing of the command; similarly, if the vi option is set, the shell
2757 allows vi-like editing of the command. These modes are described in
2758 detail in the following sections.
2759 In these editing modes, if a line is longer than the screen width (see
2761 the COLUMNS parameter), a ‘>’, ‘+’ or ‘<’ character is displayed in the
2762 last column indicating that there are more characters after, before and
2763 after, or before the current position, respectively. The line is
2764 scrolled horizontally as necessary.
2765 Completed lines are pushed into the history, unless they begin with an
2767 IFS octet or IFS white space or are the same as the previous line.
2768 Emacs editing mode
2770 When the emacs option is set, interactive input line editing is enabled.
2771 Warning: This mode is slightly different from the emacs mode in the orig‐
2772 inal Korn shell. In this mode, various editing commands (typically bound
2773 to one or more control characters) cause immediate actions without wait‐
2774 ing for a newline. Several editing commands are bound to particular con‐
2775 trol characters when the shell is invoked; these bindings can be changed
2776 using the bind command.
2777 The following is a list of available editing commands. Each description
2779 starts with the name of the command, suffixed with a colon; an [n] (if
2780 the command can be prefixed with a count); and any keys the command is
2781 bound to by default, written using caret notation e.g. the ASCII ESC
2782 character is written as ^[. These control sequences are not case sensi‐
2783 tive. A count prefix for a command is entered using the sequence ^[n,
2784 where n is a sequence of 1 or more digits. Unless otherwise specified,
2785 if a count is omitted, it defaults to 1.
2786 Note that editing command names are used only with the bind command.
2788 Furthermore, many editing commands are useful only on terminals with a
2789 visible cursor. The user's tty(4) characters (e.g. ERASE) are bound to
2790 reasonable substitutes and override the default bindings; their customary
2791 values are shown in parentheses below. The default bindings were chosen
2792 to resemble corresponding Emacs key bindings:
2793 abort: INTR (^C), ^G
2795 Abort the current command, save it to the history, empty the line
2796 buffer and set the exit state to interrupted.
2797 auto-insert: [n]
2799 Simply causes the character to appear as literal input. Most
2800 ordinary characters are bound to this.
2801 backward-char: [n] ^B, ^XD, ANSI-CurLeft, PC-CurLeft
2803 Moves the cursor backward n characters.
2804 backward-word: [n] ^[b, ANSI-Ctrl-CurLeft, ANSI-Alt-CurLeft
2806 Moves the cursor backward to the beginning of the word; words
2807 consist of alphanumerics, underscore (‘_’) and dollar sign (‘$’)
2808 characters.
2809 beginning-of-history: ^[<
2811 Moves to the beginning of the history.
2812 beginning-of-line: ^A, ANSI-Home, PC-Home
2814 Moves the cursor to the beginning of the edited input line.
2815 capitalise-word: [n] ^[C, ^[c
2817 Uppercase the first ASCII character in the next n words, leaving
2818 the cursor past the end of the last word.
2819 clear-screen: ^[^L
2821 Prints a compile-time configurable sequence to clear the screen
2822 and home the cursor, redraws the last line of the prompt string
2823 and the currently edited input line. The default sequence works
2824 for almost all standard terminals.
2825 comment: ^[#
2827 If the current line does not begin with a comment character, one
2828 is added at the beginning of the line and the line is entered (as
2829 if return had been pressed); otherwise, the existing comment
2830 characters are removed and the cursor is placed at the beginning
2831 of the line.
2832 complete: ^[^[
2834 Automatically completes as much as is unique of the command name
2835 or the file name containing the cursor. If the entire remaining
2836 command or file name is unique, a space is printed after its com‐
2837 pletion, unless it is a directory name in which case ‘/’ is
2838 appended. If there is no command or file name with the current
2839 partial word as its prefix, a bell character is output (usually
2840 causing a beep to be sounded).
2841 complete-command: ^X^[
2843 Automatically completes as much as is unique of the command name
2844 having the partial word up to the cursor as its prefix, as in the
2845 complete command above.
2846 complete-file: ^[^X
2848 Automatically completes as much as is unique of the file name
2849 having the partial word up to the cursor as its prefix, as in the
2850 complete command described above.
2851 complete-list: ^I, ^[=
2853 Complete as much as is possible of the current word and list the
2854 possible completions for it. If only one completion is possible,
2855 match as in the complete command above. Note that ^I is usually
2856 generated by the TAB (tabulator) key.
2857 delete-char-backward: [n] ERASE (^H), ^?, ^H
2859 Deletes n characters before the cursor.
2860 delete-char-forward: [n] ANSI-Del, PC-Del
2862 Deletes n characters after the cursor.
2863 delete-word-backward: [n] Pfx1+ERASE (^[^H), WERASE (^W), ^[^?, ^[^H, ^[h
2865 Deletes n words before the cursor.
2866 delete-word-forward: [n] ^[d
2868 Deletes characters after the cursor up to the end of n words.
2869 down-history: [n] ^N, ^XB, ANSI-CurDown, PC-CurDown
2871 Scrolls the history buffer forward n lines (later). Each input
2872 line originally starts just after the last entry in the history
2873 buffer, so down-history is not useful until either
2874 search-history, search-history-up or up-history has been per‐
2875 formed.
2876 downcase-word: [n] ^[L, ^[l
2878 Lowercases the next n words.
2879 edit-line: [n] ^Xe
2881 Edit line n or the current line, if not specified, interactively.
2882 The actual command executed is fc -e ${VISUAL:-${EDITOR:-vi}} n.
2883 end-of-history: ^[>
2885 Moves to the end of the history.
2886 end-of-line: ^E, ANSI-End, PC-End
2888 Moves the cursor to the end of the input line.
2889 eot: ^_
2891 Acts as an end-of-file; this is useful because edit-mode input
2892 disables normal terminal input canonicalisation.
2893 eot-or-delete: [n] EOF (^D)
2895 If alone on a line, same as eot, otherwise, delete-char-forward.
2896 error: (not bound)
2898 Error (ring the bell).
2899 evaluate-region: ^[^E
2901 Evaluates the text between the mark and the cursor position (the
2902 entire line if no mark is set) as function substitution (if it
2903 cannot be parsed, the editing state is unchanged and the bell is
2904 rung to signal an error); $? is updated accordingly.
2905 exchange-point-and-mark: ^X^X
2907 Places the cursor where the mark is and sets the mark to where
2908 the cursor was.
2909 expand-file: ^[*
2911 Appends a ‘*’ to the current word and replaces the word with the
2912 result of performing file globbing on the word. If no files
2913 match the pattern, the bell is rung.
2914 forward-char: [n] ^F, ^XC, ANSI-CurRight, PC-CurRight
2916 Moves the cursor forward n characters.
2917 forward-word: [n] ^[f, ANSI-Ctrl-CurRight, ANSI-Alt-CurRight
2919 Moves the cursor forward to the end of the nth word.
2920 goto-history: [n] ^[g
2922 Goes to history number n.
2923 kill-line: KILL (^U)
2925 Deletes the entire input line.
2926 kill-region: ^W
2928 Deletes the input between the cursor and the mark.
2929 kill-to-eol: [n] ^K
2931 Deletes the input from the cursor to the end of the line if n is
2932 not specified; otherwise deletes characters between the cursor
2933 and column n.
2934 list: ^[?
2936 Prints a sorted, columnated list of command names or file names
2937 (if any) that can complete the partial word containing the cur‐
2938 sor. Directory names have ‘/’ appended to them.
2939 list-command: ^X?
2941 Prints a sorted, columnated list of command names (if any) that
2942 can complete the partial word containing the cursor.
2943 list-file: ^X^Y
2945 Prints a sorted, columnated list of file names (if any) that can
2946 complete the partial word containing the cursor. File type indi‐
2947 cators are appended as described under list above.
2948 newline: ^J, ^M
2950 Causes the current input line to be processed by the shell. The
2951 current cursor position may be anywhere on the line.
2952 newline-and-next: ^O
2954 Causes the current input line to be processed by the shell, and
2955 the next line from history becomes the current line. This is
2956 only useful after an up-history, search-history or
2957 search-history-up.
2958 no-op: QUIT (^\)
2960 This does nothing.
2961 prefix-1: ^[
2963 Introduces a 2-character command sequence.
2964 prefix-2: ^X, ^[[, ^[O
2966 Introduces a multi-character command sequence.
2967 prev-hist-word: [n] ^[., ^[_
2969 The last word or, if given, the nth word (zero-based) of the pre‐
2970 vious (on repeated execution, second-last, third-last, etc.) com‐
2971 mand is inserted at the cursor. Use of this editing command
2972 trashes the mark.
2973 quote: ^^, ^V
2975 The following character is taken literally rather than as an
2976 editing command.
2977 redraw: ^L
2979 Reprints the last line of the prompt string and the current input
2980 line on a new line.
2981 search-character-backward: [n] ^[^]
2983 Search backward in the current line for the nth occurrence of the
2984 next character typed.
2985 search-character-forward: [n] ^]
2987 Search forward in the current line for the nth occurrence of the
2988 next character typed.
2989 search-history: ^R
2991 Enter incremental search mode. The internal history list is
2992 searched backwards for commands matching the input. An initial
2993 ‘^’ in the search string anchors the search. The escape key will
2994 leave search mode. Other commands, including sequences of escape
2995 as prefix-1 followed by a prefix-1 or prefix-2 key will be exe‐
2996 cuted after leaving search mode. The abort (^G) command will
2997 restore the input line before search started. Successive
2998 search-history commands continue searching backward to the next
2999 previous occurrence of the pattern. The history buffer retains
3000 only a finite number of lines; the oldest are discarded as neces‐
3001 sary.
3002 search-history-up: ANSI-PgUp, PC-PgUp
3004 Search backwards through the history buffer for commands whose
3005 beginning match the portion of the input line before the cursor.
3006 When used on an empty line, this has the same effect as
3007 up-history.
3008 search-history-down: ANSI-PgDn, PC-PgDn
3010 Search forwards through the history buffer for commands whose
3011 beginning match the portion of the input line before the cursor.
3012 When used on an empty line, this has the same effect as
3013 down-history. This is only useful after an up-history,
3014 search-history or search-history-up.
3015 set-mark-command: ^[<space>
3017 Set the mark at the cursor position.
3018 transpose-chars: ^T
3020 If at the end of line or, if the gmacs option is set, this
3021 exchanges the two previous characters; otherwise, it exchanges
3022 the previous and current characters and moves the cursor one
3023 character to the right.
3024 up-history: [n] ^P, ^XA, ANSI-CurUp, PC-CurUp
3026 Scrolls the history buffer backward n lines (earlier).
3027 upcase-word: [n] ^[U, ^[u
3029 Uppercase the next n words.
3030 version: ^[^V
3032 Display the version of mksh. The current edit buffer is restored
3033 as soon as a key is pressed. The restoring keypress is pro‐
3034 cessed, unless it is a space.
3035 yank: ^Y
3037 Inserts the most recently killed text string at the current cur‐
3038 sor position.
3039 yank-pop: ^[y
3041 Immediately after a yank, replaces the inserted text string with
3042 the next previously killed text string.
3043 The tab completion escapes characters the same way as the following code:
3045 print -nr -- "${x@/[\"-\$\&-*:-?[\\\`{-\}${IFS-$' \t\n'}]/\\$KSH_MATCH}"
3047 Vi editing mode
3049 Note: The vi command-line editing mode is orphaned, yet still functional.
3050 It is 8-bit clean but specifically does not support UTF-8 or MBCS.
3051 The vi command-line editor in mksh has basically the same commands as the
3053 vi(1) editor with the following exceptions:
3054 · You start out in insert mode.
3056 · There are file name and command completion commands: =, \, *, ^X, ^E,
3058 ^F and, optionally, <tab> and <esc>.
3059 · The _ command is different (in mksh, it is the last argument command;
3061 in vi(1) it goes to the start of the current line).
3062 · The / and G commands move in the opposite direction to the j command.
3064 · Commands which don't make sense in a single line editor are not
3066 available (e.g. screen movement commands and ex(1)-style colon (:)
3067 commands).
3068 Like vi(1), there are two modes: “insert” mode and “command” mode. In
3070 insert mode, most characters are simply put in the buffer at the current
3071 cursor position as they are typed; however, some characters are treated
3072 specially. In particular, the following characters are taken from cur‐
3073 rent tty(4) settings (see stty(1)) and have their usual meaning (normal
3074 values are in parentheses): kill (^U), erase (^?), werase (^W), eof (^D),
3075 intr (^C) and quit (^\). In addition to the above, the following charac‐
3076 ters are also treated specially in insert mode:
3077 ^E Command and file name enumeration (see below).
3079 ^F Command and file name completion (see below). If used twice in
3081 a row, the list of possible completions is displayed; if used a
3082 third time, the completion is undone.
3083 ^H Erases previous character.
3085 ^J | ^M End of line. The current line is read, parsed and executed by
3087 the shell.
3088 ^V Literal next. The next character typed is not treated specially
3090 (can be used to insert the characters being described here).
3091 ^X Command and file name expansion (see below).
3093 <esc> Puts the editor in command mode (see below).
3095 <tab> Optional file name and command completion (see ^F above),
3097 enabled with set -o vi-tabcomplete.
3098 In command mode, each character is interpreted as a command. Characters
3100 that don't correspond to commands, are illegal combinations of commands,
3101 or are commands that can't be carried out, all cause beeps. In the fol‐
3102 lowing command descriptions, an [n] indicates the command may be prefixed
3103 by a number (e.g. 10l moves right 10 characters); if no number prefix is
3104 used, n is assumed to be 1 unless otherwise specified. The term “current
3105 position” refers to the position between the cursor and the character
3106 preceding the cursor. A “word” is a sequence of letters, digits and
3107 underscore characters or a sequence of non-letter, non-digit, non-under‐
3108 score and non-whitespace characters (e.g. “ab2*&^” contains two words)
3109 and a “big-word” is a sequence of non-whitespace characters.
3110 Special mksh vi commands:
3112 The following commands are not in, or are different from, the normal vi
3114 file editor:
3115 [n]_ Insert a space followed by the nth big-word from the last
3117 command in the history at the current position and enter
3118 insert mode; if n is not specified, the last word is
3119 inserted.
3120 # Insert the comment character (‘#’) at the start of the cur‐
3122 rent line and return the line to the shell (equivalent to
3123 I#^J).
3124 [n]g Like G, except if n is not specified, it goes to the most
3126 recent remembered line.
3127 [n]v Edit line n using the vi(1) editor; if n is not specified,
3129 the current line is edited. The actual command executed is
3130 fc -e ${VISUAL:-${EDITOR:-vi}} n.
3131 * and ^X Command or file name expansion is applied to the current big-
3133 word (with an appended ‘*’ if the word contains no file glob‐
3134 bing characters) – the big-word is replaced with the result‐
3135 ing words. If the current big-word is the first on the line
3136 or follows one of the characters ‘;’, ‘|’, ‘&’, ‘(’ or ‘)’
3137 and does not contain a slash (‘/’), then command expansion is
3138 done; otherwise file name expansion is done. Command expan‐
3139 sion will match the big-word against all aliases, functions
3140 and built-in commands as well as any executable files found
3141 by searching the directories in the PATH parameter. File
3142 name expansion matches the big-word against the files in the
3143 current directory. After expansion, the cursor is placed
3144 just past the last word and the editor is in insert mode.
3145 [n]\, [n]^F, [n]<tab>, and [n]<esc>
3147 Command/file name completion. Replace the current big-word
3148 with the longest unique match obtained after performing com‐
3149 mand and file name expansion. <tab> is only recognised if
3150 the vi-tabcomplete option is set, while <esc> is only recog‐
3151 nised if the vi-esccomplete option is set (see set -o). If n
3152 is specified, the nth possible completion is selected (as
3153 reported by the command/file name enumeration command).
3154 = and ^E Command/file name enumeration. List all the commands or
3156 files that match the current big-word.
3157 ^V Display the version of mksh. The current edit buffer is
3159 restored as soon as a key is pressed. The restoring keypress
3160 is ignored.
3161 @c Macro expansion. Execute the commands found in the alias c.
3163 Intra-line movement commands:
3165 [n]h and [n]^H
3167 Move left n characters.
3168 [n]l and [n]<space>
3170 Move right n characters.
3171 0 Move to column 0.
3173 ^ Move to the first non-whitespace character.
3175 [n]| Move to column n.
3177 $ Move to the last character.
3179 [n]b Move back n words.
3181 [n]B Move back n big-words.
3183 [n]e Move forward to the end of the word, n times.
3185 [n]E Move forward to the end of the big-word, n times.
3187 [n]w Move forward n words.
3189 [n]W Move forward n big-words.
3191 % Find match. The editor looks forward for the nearest parenthe‐
3193 sis, bracket or brace and then moves the cursor to the matching
3194 parenthesis, bracket or brace.
3195 [n]fc Move forward to the nth occurrence of the character c.
3197 [n]Fc Move backward to the nth occurrence of the character c.
3199 [n]tc Move forward to just before the nth occurrence of the character
3201 c.
3202 [n]Tc Move backward to just before the nth occurrence of the character
3204 c.
3205 [n]; Repeats the last f, F, t or T command.
3207 [n], Repeats the last f, F, t or T command, but moves in the opposite
3209 direction.
3210 Inter-line movement commands:
3212 [n]j, [n]+, and [n]^N
3214 Move to the nth next line in the history.
3215 [n]k, [n]-, and [n]^P
3217 Move to the nth previous line in the history.
3218 [n]G Move to line n in the history; if n is not specified, the number
3220 of the first remembered line is used.
3221 [n]g Like G, except if n is not specified, it goes to the most recent
3223 remembered line.
3224 [n]/string
3226 Search backward through the history for the nth line containing
3227 string; if string starts with ‘^’, the remainder of the string
3228 must appear at the start of the history line for it to match.
3229 [n]?string
3231 Same as /, except it searches forward through the history.
3232 [n]n Search for the nth occurrence of the last search string; the
3234 direction of the search is the same as the last search.
3235 [n]N Search for the nth occurrence of the last search string; the
3237 direction of the search is the opposite of the last search.
3238 ANSI-CurUp, PC-PgUp
3240 Take the characters from the beginning of the line to the current
3241 cursor position as search string and do a backwards history
3242 search for lines beginning with this string; keep the cursor
3243 position. This works only in insert mode and keeps it enabled.
3244 Edit commands
3246 [n]a Append text n times; goes into insert mode just after the current
3248 position. The append is only replicated if command mode is re-
3249 entered i.e. <esc> is used.
3250 [n]A Same as a, except it appends at the end of the line.
3252 [n]i Insert text n times; goes into insert mode at the current posi‐
3254 tion. The insertion is only replicated if command mode is re-
3255 entered i.e. <esc> is used.
3256 [n]I Same as i, except the insertion is done just before the first
3258 non-blank character.
3259 [n]s Substitute the next n characters (i.e. delete the characters and
3261 go into insert mode).
3262 S Substitute whole line. All characters from the first non-blank
3264 character to the end of the line are deleted and insert mode is
3265 entered.
3266 [n]cmove-cmd
3268 Change from the current position to the position resulting from n
3269 move-cmds (i.e. delete the indicated region and go into insert
3270 mode); if move-cmd is c, the line starting from the first non-
3271 blank character is changed.
3272 C Change from the current position to the end of the line (i.e.
3274 delete to the end of the line and go into insert mode).
3275 [n]x Delete the next n characters.
3277 [n]X Delete the previous n characters.
3279 D Delete to the end of the line.
3281 [n]dmove-cmd
3283 Delete from the current position to the position resulting from n
3284 move-cmds; move-cmd is a movement command (see above) or d, in
3285 which case the current line is deleted.
3286 [n]rc Replace the next n characters with the character c.
3288 [n]R Replace. Enter insert mode but overwrite existing characters
3290 instead of inserting before existing characters. The replacement
3291 is repeated n times.
3292 [n]~ Change the case of the next n characters.
3294 [n]ymove-cmd
3296 Yank from the current position to the position resulting from n
3297 move-cmds into the yank buffer; if move-cmd is y, the whole line
3298 is yanked.
3299 Y Yank from the current position to the end of the line.
3301 [n]p Paste the contents of the yank buffer just after the current
3303 position, n times.
3304 [n]P Same as p, except the buffer is pasted at the current position.
3306 Miscellaneous vi commands
3308 ^J and ^M
3310 The current line is read, parsed and executed by the shell.
3311 ^L and ^R
3313 Redraw the current line.
3314 [n]. Redo the last edit command n times.
3316 u Undo the last edit command.
3318 U Undo all changes that have been made to the current line.
3320 PC Home, End, Del and cursor keys
3322 They move as expected, both in insert and command mode.
3323 intr and quit
3325 The interrupt and quit terminal characters cause the current line
3326 to be removed to the history and a new prompt to be printed.
3327
3329 ~/.mkshrc User mkshrc profile (non-privileged interactive
3330 shells); see Startup files. The location can be
3331 changed at compile time (for embedded systems); AOSP
3332 Android builds use /system/etc/mkshrc.
3333 ~/.profile User profile (non-privileged login shells); see
3334 Startup files near the top of this manual.
3335 /etc/profile System profile (login shells); see Startup files.
3336 /etc/shells Shell database.
3337 /etc/suid_profile Suid profile (privileged shells); see Startup files.
3338 Note: On Android, /system/etc/ contains the system and suid profile.
3340
3342 awk(1), cat(1), ed(1), getopt(1), lksh(1), sed(1), sh(1), stty(1),
3343 dup(2), execve(2), getgid(2), getuid(2), mknod(2), mkfifo(2), open(2),
3344 pipe(2), rename(2), wait(2), getopt(3), nl_langinfo(3), setlocale(3),
3345 signal(3), system(3), tty(4), shells(5), environ(7), script(7), utf-8(7),
3346 mknod(8)
3347 http://www.mirbsd.org/ksh-chan.htm
3349 Morris Bolsky, The KornShell Command and Programming Language, Prentice
3351 Hall PTR, xvi + 356 pages, 1989, ISBN 978-0-13-516972-8 (0-13-516972-0).
3352 Morris I. Bolsky and David G. Korn, The New KornShell Command and
3354 Programming Language (2nd Edition), Prentice Hall PTR, xvi + 400 pages,
3355 1995, ISBN 978-0-13-182700-4 (0-13-182700-6).
3356 Stephen G. Kochan and Patrick H. Wood, UNIX Shell Programming, Sams, 3rd
3358 Edition, xiii + 437 pages, 2003, ISBN 978-0-672-32490-1 (0-672-32490-3).
3359 IEEE Inc., IEEE Standard for Information Technology – Portable Operating
3361 System Interface (POSIX), IEEE Press, Part 2: Shell and Utilities,
3362 xvii + 1195 pages, 1993, ISBN 978-1-55937-255-8 (1-55937-255-9).
3363 Bill Rosenblatt, Learning the Korn Shell, O'Reilly, 360 pages, 1993, ISBN
3365 978-1-56592-054-5 (1-56592-054-6).
3366 Bill Rosenblatt and Arnold Robbins, Learning the Korn Shell, Second
3368 Edition, O'Reilly, 432 pages, 2002, ISBN 978-0-596-00195-7
3369 (0-596-00195-9).
3370 Barry Rosenberg, KornShell Programming Tutorial, Addison-Wesley
3372 Professional, xxi + 324 pages, 1991, ISBN 978-0-201-56324-5
3373 (0-201-56324-X).
3374
3376 The MirBSD Korn Shell is developed by mirabilos <m@mirbsd.org> as part of
3377 The MirOS Project. This shell is based on the public domain 7th edition
3378 Bourne shell clone by Charles Forsyth, who kindly agreed to, in countries
3379 where the Public Domain status of the work may not be valid, grant a
3380 copyright licence to the general public to deal in the work without
3381 restriction and permission to sublicence derivatives under the terms of
3382 any (OSI approved) Open Source licence, and parts of the BRL shell by
3383 Doug A. Gwyn, Doug Kingston, Ron Natalie, Arnold Robbins, Lou Salkind and
3384 others. The first release of pdksh was created by Eric Gisin, and it was
3385 subsequently maintained by John R. MacMillan, Simon J. Gerraty and
3386 Michael Rendell. The effort of several projects, such as Debian and
3387 OpenBSD, and other contributors including our users, to improve the shell
3388 is appreciated. See the documentation, website and source code (CVS) for
3389 details.
3390 mksh-os2 is developed by KO Myung-Hun <komh@chollian.net>.
3392 mksh-w32 is developed by Michael Langguth <lan@scalaris.com>.
3394 mksh/z/OS is contributed by Daniel Richard G. <skunk@iSKUNK.ORG>.
3396 The BSD daemon is Copyright © Marshall Kirk McKusick. The complete
3398 legalese is at: http://www.mirbsd.org/TaC-mksh.txt
3399
3401 mksh provides a consistent 32-bit integer arithmetic implementation, both
3402 signed and unsigned, with sign of the result of a remainder operation and
3403 wraparound defined, even (defying POSIX) on 36-bit and 64-bit systems.
3404 mksh provides a consistent, clear interface normally. This may deviate
3406 from POSIX in historic or opinionated places. set -o posix (see POSIX
3407 mode for details) will cause the shell to behave more conformant.
3408 For the purpose of POSIX, mksh supports only the “C” locale. mksh's
3410 utf8-mode must be disabled in POSIX mode, and it only supports the Uni‐
3411 code BMP (Basic Multilingual Plane) and maps raw octets into the
3412 U+EF80..U+EFFF wide character range; compare Arithmetic expressions. The
3413 following POSIX sh-compatible code toggles the utf8-mode option dependent
3414 on the current POSIX locale for mksh to allow using the UTF-8 mode,
3415 within the constraints outlined above, in code portable across various
3416 shell implementations:
3417 case ${KSH_VERSION:-} in
3419 *MIRBSD KSH*|*LEGACY KSH*)
3420 case ${LC_ALL:-${LC_CTYPE:-${LANG:-}}} in
3421 *[Uu][Tt][Ff]8*|*[Uu][Tt][Ff]-8*) set -U ;;
3422 *) set +U ;;
3423 esac ;;
3424 esac
3425 In near future, (Unicode) locale tracking will be implemented though.
3426 See also the FAQ below.
3428
3430 Suspending (using ^Z) pipelines like the one below will only suspend the
3431 currently running part of the pipeline; in this example, “fubar” is imme‐
3432 diately printed on suspension (but not later after an fg).
3433 $ /bin/sleep 666 && echo fubar
3435 The truncation process involved when changing HISTFILE does not free old
3437 history entries (leaks memory) and leaks old entries into the new history
3438 if their line numbers are not overwritten by same-number entries from the
3439 persistent history file; truncating the on-disc file to HISTSIZE lines
3440 has always been broken and prone to history file corruption when multiple
3441 shells are accessing the file; the rollover process for the in-memory
3442 portion of the history is slow, should use memmove(3).
3443 This document attempts to describe mksh R56 and up, compiled without any
3445 options impacting functionality, such as MKSH_SMALL, when not called as
3446 /bin/sh which, on some systems only, enables set -o posix or set -o sh
3447 automatically (whose behaviour differs across targets), for an operating
3448 environment supporting all of its advanced needs.
3449 Please report bugs in mksh to the <miros-mksh@mirbsd.org> mailing list or
3451 in the #!/bin/mksh (or #ksh) IRC channel at irc.freenode.net (Port 6697
3452 SSL, 6667 unencrypted), or at: https://launchpad.net/mksh
3453
3455 This FAQ attempts to document some of the questions users of mksh or
3456 readers of this manual page may encounter.
3457 I'm an Android user, so what's mksh?
3459 mksh is a UNIX shell / command interpreter, similar to COMMAND.COM or
3460 CMD.EXE, which has been included with Android Open Source Project for a
3461 while now. Basically, it's a program that runs in a terminal (console
3462 window), takes user input and runs commands or scripts, which it can also
3463 be asked to do by other programs, even in the background. Any privilege
3464 pop-ups you might be encountering are thus not mksh issues but questions
3465 by some other program utilising it.
3466 I'm an OS/2 user, what do I need to know?
3468 Unlike the native command prompt, the current working directory is, for
3469 security reasons common on Unix systems which the shell is designed for,
3470 not in the search path at all; if you really need this, run the command
3471 PATH=.$PATHSEP$PATH or add that to a suitable initialisation file.
3472 There are two different newline modes for mksh-os2: standard (Unix) mode,
3474 in which only LF (0A hex) is supported as line separator, and "textmode",
3475 which also accepts ASCII newlines (CR+LF), like most other tools on OS/2,
3476 but creating an incompatibility with standard mksh. If you compiled mksh
3477 from source, you will get the standard Unix mode unless -T is added dur‐
3478 ing compilation; you will most likely have gotten this shell through
3479 komh's port on Hobbes, or from his OS/2 Factory on eComStation Korea,
3480 which uses "textmode", though. Most OS/2 users will want to use
3481 "textmode" unless they need absolute compatibility with Unix mksh.
3482 How do I start mksh on a specific terminal?
3484 Normally:
3485 mksh -T/dev/tty2
3486 However, if you want for it to return (e.g. for an embedded system rescue
3488 shell), use this on your real console device instead:
3489 mksh -T!/dev/ttyACM0
3490 mksh can also daemonise (send to the background):
3492 mksh -T- -c 'exec cdio lock'
3493 POSIX says...
3495 Run the shell in POSIX mode (and possibly lksh instead of mksh):
3496 set -o posix
3497 My prompt from <some other shell> does not work!
3499 Contact us on the mailing list or on IRC, we'll convert it for you.
3500 Something is going wrong with my while...read loop
3502 Most likely, you've encountered the problem in which the shell runs all
3503 parts of a pipeline as subshell. The inner loop will be executed in a
3504 subshell and variable changes cannot be propagated if run in a pipeline:
3505 bar | baz | while read foo; do ...; done
3507 Note that exit in the inner loop will only exit the subshell and not the
3509 original shell. Likewise, if the code is inside a function, return in
3510 the inner loop will only exit the subshell and won't terminate the func‐
3511 tion.
3512 Use co-processes instead:
3514 bar | baz |&
3516 while read -p foo; do ...; done
3517 exec 3>&p; exec 3>&-
3518 If read is run in a loop such as while read foo; do ...; done then lead‐
3520 ing whitespace will be removed (IFS) and backslashes processed. You
3521 might want to use while IFS= read -r foo; do ...; done for pristine I/O.
3522 Similarly, when using the -a option, use of the -r option might be pru‐
3523 dent (“read -raN-1 arr <file”); the same applies for NUL-terminated
3524 lines:
3525 find . -type f -print0 |& \
3527 while IFS= read -d '' -pr filename; do
3528 print -r -- "found <${filename#./}>"
3529 done
3530 What differences in function-local scopes are there?
3532 mksh has a different scope model from AT&T UNIX ksh, which leads to sub‐
3533 tle differences in semantics for identical builtins. This can cause
3534 issues with a nameref to suddenly point to a local variable by accident.
3535 GNU bash allows unsetting local variables; in mksh, doing so in a func‐
3537 tion allows back access to the global variable (actually the one in the
3538 next scope up) with the same name. The following code, when run before
3539 the function definitions, changes the behaviour of unset to behave like
3540 other shells (the alias can be removed after the definitions):
3541 case ${KSH_VERSION:-} in
3543 *MIRBSD KSH*|*LEGACY KSH*)
3544 function unset_compat {
3545 \\builtin typeset unset_compat_x
3546 for unset_compat_x in "$@"; do
3548 eval "\\\\builtin unset $unset_compat_x[*]"
3549 done
3550 }
3551 \\builtin alias unset=unset_compat
3552 ;;
3553 esac
3554 When a local variable is created (e.g. using local, typeset, integer,
3556 \\builtin typeset) it does not, like in other shells, inherit the value
3557 from the global (next scope up) variable with the same name; it is rather
3558 created without any value (unset but defined).
3559 I get an error in this regex comparison
3561 Use extglobs instead of regexes:
3562 [[ foo =~ (foo|bar).*baz ]] # becomes
3563 [[ foo = *@(foo|bar)*baz* ]] # instead
3564 Are there any extensions to avoid?
3566 GNU bash supports “&>” (and “|&”) to redirect both stdout and stderr in
3567 one go, but this breaks POSIX and Korn Shell syntax; use POSIX redirec‐
3568 tions instead:
3569 foo |& bar |& baz &>log # GNU bash
3570 foo 2>&1 | bar 2>&1 | baz >log 2>&1 # POSIX
3571 ^L (Ctrl-L) does not clear the screen
3573 Use ^[^L (Escape+Ctrl-L) or rebind it:
3574 bind '^L=clear-screen'
3575 ^U (Ctrl-U) clears the entire line
3577 If it should only delete the line up to the cursor, use:
3578 bind -m ^U='^[0^K'
3579 Cursor Up behaves differently from zsh
3581 Some shells make Cursor Up search in the history only for commands start‐
3582 ing with what was already entered. mksh separates the shortcuts: Cursor
3583 Up goes up one command and PgUp searches the history as described above.
3584 My question is not answered here!
3586 Check http://www.mirbsd.org/mksh-faq.htm which contains a collection of
3587 frequently asked questions about mksh in general, for packagers, etc.
3588 while these above are in user scope.
3589MirBSD August 16, 2017 MirBSD