1ZSHMISC(1)                  General Commands Manual                 ZSHMISC(1)
2
3
4

NAME

6       zshmisc - everything and then some
7

SIMPLE COMMANDS & PIPELINES

9       A  simple  command is a sequence of optional parameter assignments fol‐
10       lowed by  blank-separated  words,  with  optional  redirections  inter‐
11       spersed.  The first word is the command to be executed, and the remain‐
12       ing words, if any, are arguments to the command.  If a command name  is
13       given,  the parameter assignments modify the environment of the command
14       when it is executed.  The value of a simple command is its exit status,
15       or 128 plus the signal number if terminated by a signal.  For example,
16
17              echo foo
18
19       is a simple command with arguments.
20
21       A  pipeline  is  either  a simple command, or a sequence of two or more
22       simple commands where each command is separated from the next by `|' or
23       `|&'.   Where commands are separated by `|', the standard output of the
24       first command is connected to the standard input of the next.  `|&'  is
25       shorthand for `2>&1 |', which connects both the standard output and the
26       standard error of the command to the standard input of the  next.   The
27       value  of a pipeline is the value of the last command, unless the pipe‐
28       line is preceded by `!' in which case the value is the logical  inverse
29       of the value of the last command.  For example,
30
31              echo foo | sed 's/foo/bar/'
32
33       is  a  pipeline,  where  the output (`foo' plus a newline) of the first
34       command will be passed to the input of the second.
35
36       If a pipeline is preceded by `coproc', it is executed as a coprocess; a
37       two-way pipe is established between it and the parent shell.  The shell
38       can read from or write to the coprocess by means of the `>&p' and `<&p'
39       redirection  operators  or  with  `print -p' and `read -p'.  A pipeline
40       cannot be preceded by both `coproc' and `!'.  If job control is active,
41       the coprocess can be treated in other than input and output as an ordi‐
42       nary background job.
43
44       A sublist is either a single pipeline, or a sequence  of  two  or  more
45       pipelines separated by `&&' or `||'.  If two pipelines are separated by
46       `&&', the second pipeline  is  executed  only  if  the  first  succeeds
47       (returns  a  zero status).  If two pipelines are separated by `||', the
48       second is executed only if the first fails (returns a nonzero  status).
49       Both  operators  have  equal  precedence and are left associative.  The
50       value of the sublist is the value of the last pipeline  executed.   For
51       example,
52
53              dmesg | grep panic && print yes
54
55       is a sublist consisting of two pipelines, the second just a simple com‐
56       mand which will be executed if and only if the grep command  returns  a
57       zero  status.   If it does not, the value of the sublist is that return
58       status, else it is the status returned by the print  (almost  certainly
59       zero).
60
61       A list is a sequence of zero or more sublists, in which each sublist is
62       terminated by `;', `&', `&|', `&!', or a newline.  This terminator  may
63       optionally  be  omitted from the last sublist in the list when the list
64       appears as a complex command inside `(...)' or `{...}'.  When a sublist
65       is  terminated  by  `;'  or  newline,  the shell waits for it to finish
66       before executing the next sublist.  If a sublist  is  terminated  by  a
67       `&',  `&|',  or `&!', the shell executes the last pipeline in it in the
68       background, and does not wait for it to  finish  (note  the  difference
69       from  other  shells which execute the whole sublist in the background).
70       A backgrounded pipeline returns a status of zero.
71
72       More generally, a list can be seen as a set of any shell commands what‐
73       soever,  including the complex commands below; this is implied wherever
74       the word `list' appears in later descriptions.  For example,  the  com‐
75       mands in a shell function form a special sort of list.
76

PRECOMMAND MODIFIERS

78       A  simple  command may be preceded by a precommand modifier, which will
79       alter how the  command  is  interpreted.   These  modifiers  are  shell
80       builtin  commands  with  the exception of nocorrect which is a reserved
81       word.
82
83       -      The command is executed with a  `-'  prepended  to  its  argv[0]
84              string.
85
86       builtin
87              The  command  word is taken to be the name of a builtin command,
88              rather than a shell function or external command.
89
90       command [ -pvV ]
91              The command word is taken to be the name of an external command,
92              rather than a shell function or builtin.   If the POSIX_BUILTINS
93              option is set, builtins will also be executed but  certain  spe‐
94              cial  properties  of  them  are suppressed. The -p flag causes a
95              default path to be searched instead of that in $path.  With  the
96              -v flag, command is similar to whence and with -V, it is equiva‐
97              lent to whence -v.
98
99       exec [ -cl ] [ -a argv0 ]
100              The following command together with  any  arguments  is  run  in
101              place of the current process, rather than as a sub-process.  The
102              shell does not fork and is replaced.  The shell does not  invoke
103              TRAPEXIT,  nor  does  it  source zlogout files.  The options are
104              provided for compatibility with other shells.
105
106              The -c option clears the environment.
107
108              The -l option is equivalent to the  -  precommand  modifier,  to
109              treat  the  replacement command as a login shell; the command is
110              executed with a - prepended to its argv[0]  string.   This  flag
111              has no effect if used together with the -a option.
112
113              The  -a  option is used to specify explicitly the argv[0] string
114              (the name of the command as seen by the process  itself)  to  be
115              used  by  the  replacement command and is directly equivalent to
116              setting a value for the ARGV0 environment variable.
117
118       nocorrect
119              Spelling correction is not done on any of the words.  This  must
120              appear  before  any  other  precommand modifier, as it is inter‐
121              preted immediately, before any  parsing  is  done.   It  has  no
122              effect in non-interactive shells.
123
124       noglob Filename  generation  (globbing)  is not performed on any of the
125              words.
126

COMPLEX COMMANDS

128       A complex command in zsh is one of the following:
129
130       if list then list [ elif list then list ] ... [ else list ] fi
131              The if list is executed, and if it returns a zero  exit  status,
132              the then list is executed.  Otherwise, the elif list is executed
133              and if its status is zero, the then list is executed.   If  each
134              elif list returns nonzero status, the else list is executed.
135
136       for name ... [ in word ... ] term do list done
137              where  term  is  at  least one newline or ;.  Expand the list of
138              words, and set the parameter name to each of them in turn,  exe‐
139              cuting list each time.  If the in word is omitted, use the posi‐
140              tional parameters instead of the words.
141
142              More than one parameter name  can  appear  before  the  list  of
143              words.  If N names are given, then on each execution of the loop
144              the next N words are assigned to the  corresponding  parameters.
145              If  there  are  more  names  than remaining words, the remaining
146              parameters are each set to the empty string.  Execution  of  the
147              loop ends when there is no remaining word to assign to the first
148              name.  It is only possible for in to appear as the first name in
149              the  list,  else  it  will  be treated as marking the end of the
150              list.
151
152       for (( [expr1] ; [expr2] ; [expr3] )) do list done
153              The arithmetic expression expr1 is evaluated first (see the sec‐
154              tion  `Arithmetic Evaluation').  The arithmetic expression expr2
155              is repeatedly evaluated until it  evaluates  to  zero  and  when
156              non-zero,  list  is executed and the arithmetic expression expr3
157              evaluated.  If any expression is omitted, then it behaves as  if
158              it evaluated to 1.
159
160       while list do list done
161              Execute  the  do  list  as long as the while list returns a zero
162              exit status.
163
164       until list do list done
165              Execute the do list as long as until list returns a nonzero exit
166              status.
167
168       repeat word do list done
169              word  is expanded and treated as an arithmetic expression, which
170              must evaluate to a number n.  list is then executed n times.
171
172              The repeat syntax is disabled by default when the  shell  starts
173              in  a  mode emulating another shell.  It can be enabled with the
174              command `enable -r repeat'
175
176       case word in [ [(] pattern [ | pattern ] ... ) list  (;;|;&|;|)  ]  ...
177       esac
178              Execute  the list associated with the first pattern that matches
179              word, if any.  The form of the patterns is the same as that used
180              for filename generation.  See the section `Filename Generation'.
181
182              If  the  list that is executed is terminated with ;& rather than
183              ;;, the following list is also executed.  The rule for the  ter‐
184              minator of the following list ;;, ;& or ;| is applied unless the
185              esac is reached.
186
187              If the list that is executed is terminated  with  ;|  the  shell
188              continues  to scan the patterns looking for the next match, exe‐
189              cuting the corresponding list, and applying  the  rule  for  the
190              corresponding  terminator  ;;,  ;& or ;|.  Note that word is not
191              re-expanded; all applicable patterns are tested  with  the  same
192              word.
193
194       select name [ in word ... term ] do list done
195              where  term  is one or more newline or ; to terminate the words.
196              Print the set of words, each preceded by a number.   If  the  in
197              word  is  omitted,  use  the positional parameters.  The PROMPT3
198              prompt is printed and a line is read from the line editor if the
199              shell is interactive and that is active, or else standard input.
200              If this line consists of the number of one of the listed  words,
201              then the parameter name is set to the word corresponding to this
202              number.  If this line is empty, the selection  list  is  printed
203              again.   Otherwise,  the  value  of the parameter name is set to
204              null.  The contents of the line  read  from  standard  input  is
205              saved  in the parameter REPLY.  list is executed for each selec‐
206              tion until a break or end-of-file is encountered.
207
208       ( list )
209              Execute list in a subshell.  Traps set by the trap  builtin  are
210              reset to their default values while executing list.
211
212       { list }
213              Execute list.
214
215       { try-list } always { always-list }
216              First  execute  try-list.   Regardless of errors, or break, con‐
217              tinue, or return commands encountered within  try-list,  execute
218              always-list.   Execution  then  continues from the result of the
219              execution of try-list; in other words, any error, or break, con‐
220              tinue,  or  return  command  is treated in the normal way, as if
221              always-list were not  present.   The  two  chunks  of  code  are
222              referred to as the `try block' and the `always block'.
223
224              Optional  newlines  or  semicolons  may appear after the always;
225              note, however, that they may not appear  between  the  preceding
226              closing brace and the always.
227
228              An `error' in this context is a condition such as a syntax error
229              which causes the shell to abort execution of the  current  func‐
230              tion,  script,  or  list.   Syntax  errors encountered while the
231              shell is parsing the code do not cause  the  always-list  to  be
232              executed.   For  example, an erroneously constructed if block in
233              try-list would cause the shell to abort during parsing, so  that
234              always-list  would not be executed, while an erroneous substitu‐
235              tion such as ${*foo*} would cause a run-time error, after  which
236              always-list would be executed.
237
238              An  error  condition  can  be  tested and reset with the special
239              integer variable TRY_BLOCK_ERROR.  Outside  an  always-list  the
240              value  is  irrelevant,  but  it  is  initialised  to -1.  Inside
241              always-list, the  value  is  1  if  an  error  occurred  in  the
242              try-list,  else  0.   If  TRY_BLOCK_ERROR is set to 0 during the
243              always-list, the error  condition  caused  by  the  try-list  is
244              reset,  and  shell execution continues normally after the end of
245              always-list.  Altering the value during the try-list is not use‐
246              ful (unless this forms part of an enclosing always block).
247
248              Regardless  of TRY_BLOCK_ERROR, after the end of always-list the
249              normal shell status $? is the value returned  from  always-list.
250              This   will   be  non-zero  if  there  was  an  error,  even  if
251              TRY_BLOCK_ERROR was set to zero.
252
253              The following executes the given code, ignoring  any  errors  it
254              causes.   This is an alternative to the usual convention of pro‐
255              tecting code by executing it in a subshell.
256
257                     {
258                         # code which may cause an error
259                       } always {
260                         # This code is executed regardless of the error.
261                         (( TRY_BLOCK_ERROR = 0 ))
262                     }
263                     # The error condition has been reset.
264
265              An exit command (or a return command executed at  the  outermost
266              function  level  of  a  script) encountered in try-list does not
267              cause the execution of always-list.  Instead,  the  shell  exits
268              immediately after any EXIT trap has been executed.
269
270       function word ... [ () ] [ term ] { list }
271       word ... () [ term ] { list }
272       word ... () [ term ] command
273              where term is one or more newline or ;.  Define a function which
274              is referenced by any one of word.  Normally, only  one  word  is
275              provided;  multiple  words  are  usually only useful for setting
276              traps.  The body of the function is the list between the  {  and
277              }.  See the section `Functions'.
278
279              If  the  option  SH_GLOB  is  set  for  compatibility with other
280              shells, then whitespace may appear between between the left  and
281              right  parentheses  when there is a single word;  otherwise, the
282              parentheses will be treated as forming  a  globbing  pattern  in
283              that case.
284
285       time [ pipeline ]
286              The  pipeline is executed, and timing statistics are reported on
287              the standard error in the form specified by the TIMEFMT  parame‐
288              ter.   If  pipeline is omitted, print statistics about the shell
289              process and its children.
290
291       [[ exp ]]
292              Evaluates the conditional expression exp and return a zero  exit
293              status if it is true.  See the section `Conditional Expressions'
294              for a description of exp.
295

ALTERNATE FORMS FOR COMPLEX COMMANDS

297       Many of  zsh's  complex  commands  have  alternate  forms.   These  are
298       non-standard  and  are  likely not to be obvious even to seasoned shell
299       programmers; they should not be used anywhere that portability of shell
300       code is a concern.
301
302       The short versions below only work if sublist is of the form `{ list }'
303       or if the SHORT_LOOPS option is set.  For the if, while and until  com‐
304       mands, in both these cases the test part of the loop must also be suit‐
305       ably delimited, such as by `[[ ... ]]' or `(( ... ))', else the end  of
306       the  test will not be recognized.  For the for, repeat, case and select
307       commands no such special form for the arguments is necessary,  but  the
308       other  condition (the special form of sublist or use of the SHORT_LOOPS
309       option) still applies.
310
311       if list { list } [ elif list { list } ] ... [ else { list } ]
312              An alternate form of if.  The rules mean that
313
314                     if [[ -o ignorebraces ]] {
315                       print yes
316                     }
317
318              works, but
319
320                     if true {  # Does not work!
321                       print yes
322                     }
323
324              does not, since the test is not suitably delimited.
325
326       if list sublist
327              A short form of the alternate `if'.  The same limitations on the
328              form of list apply as for the previous form.
329
330       for name ... ( word ... ) sublist
331              A short form of for.
332
333       for name ... [ in word ... ] term sublist
334              where  term is at least one newline or ;.  Another short form of
335              for.
336
337       for (( [expr1] ; [expr2] ; [expr3] )) sublist
338              A short form of the arithmetic for command.
339
340       foreach name ... ( word ... ) list end
341              Another form of for.
342
343       while list { list }
344              An alternative form of while.  Note the limitations on the  form
345              of list mentioned above.
346
347       until list { list }
348              An  alternative form of until.  Note the limitations on the form
349              of list mentioned above.
350
351       repeat word sublist
352              This is a short form of repeat.
353
354       case word { [ [(] pattern [ | pattern ] ... ) list (;;|;&|;|) ] ... }
355              An alternative form of case.
356
357       select name [ in word term ] sublist
358              where term is at least one  newline  or  ;.   A  short  form  of
359              select.
360

RESERVED WORDS

362       The  following  words are recognized as reserved words when used as the
363       first word of a command unless quoted or disabled using disable -r:
364
365       do done esac then elif else fi for case if while function  repeat  time
366       until select coproc nocorrect foreach end ! [[ { }
367
368       Additionally,  `}'  is  recognized  in  any  position  if  neither  the
369       IGNORE_BRACES option nor the IGNORE_CLOSE_BRACES option is set.
370

ERRORS

372       Certain errors are treated as fatal by the  shell:  in  an  interactive
373       shell,  they  cause  control  to  return  to the command line, and in a
374       non-interactive shell they cause the shell to  be  aborted.   In  older
375       versions  of  zsh,  a  non-interactive shell running a script would not
376       abort completely, but would resume execution at the next command to  be
377       read  from the script, skipping the remainder of any functions or shell
378       constructs such as loops or conditions; this somewhat illogical  behav‐
379       iour can be recovered by setting the option CONTINUE_ON_ERROR.
380
381       Fatal errors found in non-interactive shells include:
382       Failure to parse shell options passed when invoking the shell
383       Failure to change options with the set builtin
384       Parse errors of all sorts, including failures to parse
385              mathematical expressions
386       Failures to set or modify variable behaviour with typeset,
387              local, declare, export, integer, float
388       Execution of incorrectly positioned loop control structures
389              (continue, break)
390       Attempts to use regular expression with no regular expression
391              module available
392       Disallowed operations when the RESTRICTED options is set
393       Failure to create a pipe needed for a pipeline
394       Failure to create a multio
395       Failure to autoload a module needed for a declared shell feature
396       Errors creating command or process substitutions
397       Syntax errors in glob qualifiers
398       File generation errors where not caught by the option BAD_PATTERN
399       All bad patterns used for matching within case statements
400       File generation failures where not caused by NO_MATCH or
401       All file generation errors where the pattern was used to create a
402              multio
403       Memory errors where detected by the shell
404       Invalid subscripts to shell variables
405       Attempts to assign read-only variables
406       Logical errors with variables such as assignment to the wrong type
407       Use of invalid variable names
408       Errors in variable substitution syntax
409       Failure to convert characters in $'...' expressions
410              similar options
411
412       If  the POSIX_BUILTINS option is set, more errors associated with shell
413       builtin commands are treated as fatal, as specified by the POSIX  stan‐
414       dard.
415

COMMENTS

417       In  non-interactive  shells, or in interactive shells with the INTERAC‐
418       TIVE_COMMENTS option set, a word beginning with the third character  of
419       the  histchars  parameter (`#' by default) causes that word and all the
420       following characters up to a newline to be ignored.
421

ALIASING

423       Every token in the shell input is checked to see if there is  an  alias
424       defined  for  it.  If so, it is replaced by the text of the alias if it
425       is in command position (if it could be the first word of a simple  com‐
426       mand),  or  if the alias is global.  If the text ends with a space, the
427       next word in the shell input is treated as though it  were  in  command
428       position  for  purposes  of alias expansion.  An alias is defined using
429       the alias builtin; global aliases may be defined using the -g option to
430       that builtin.
431
432       Alias  expansion  is done on the shell input before any other expansion
433       except history expansion.  Therefore, if an alias is  defined  for  the
434       word  foo,  alias expansion may be avoided by quoting part of the word,
435       e.g. \foo.  Any form of quoting works, although  there  is  nothing  to
436       prevent  an  alias  being  defined  for the quoted form such as \foo as
437       well.  For use with completion, which would remove an initial backslash
438       followed  by  a character that isn't special, it may be more convenient
439       to quote the word by starting with a single quote, i.e.  'foo;  comple‐
440       tion will automatically add the trailing single quote.
441
442       There is a commonly encountered problem with aliases illustrated by the
443       following code:
444
445              alias echobar='echo bar'; echobar
446
447       This prints a message that the command  echobar  could  not  be  found.
448       This happens because aliases are expanded when the code is read in; the
449       entire line is read in one go, so that when echobar is executed  it  is
450       too late to expand the newly defined alias.  This is often a problem in
451       shell scripts, functions, and code executed with `source' or `.'.  Con‐
452       sequently,  use  of  functions  rather  than  aliases is recommended in
453       non-interactive code.
454
455       Note also the unhelpful interaction of  aliases  and  function  defini‐
456       tions:
457
458              alias func='noglob func'
459              func() {
460                  echo Do something with $*
461              }
462
463       Because  aliases  are expanded in function definitions, this causes the
464       following command to be executed:
465
466              noglob func() {
467                  echo Do something with $*
468              }
469
470       which defines noglob as well as func as functions with the body  given.
471       To  avoid this, either quote the name func or use the alternative func‐
472       tion definition form `function func'.  Ensuring the  alias  is  defined
473       after  the function works but is problematic if the code fragment might
474       be re-executed.
475

QUOTING

477       A character may be quoted (that is, made to stand for itself)  by  pre‐
478       ceding it with a `\'.  `\' followed by a newline is ignored.
479
480       A string enclosed between `$'' and `'' is processed the same way as the
481       string arguments of the print builtin, and the resulting string is con‐
482       sidered to be entirely quoted.  A literal `'' character can be included
483       in the string by using the `\'' escape.
484
485       All characters enclosed between a pair of single quotes  ('')  that  is
486       not  preceded by a `$' are quoted.  A single quote cannot appear within
487       single quotes unless the option RC_QUOTES is set, in which case a  pair
488       of single quotes are turned into a single quote.  For example,
489
490              print ''''
491
492       outputs  nothing  apart from a newline if RC_QUOTES is not set, but one
493       single quote if it is set.
494
495       Inside double quotes (""), parameter and  command  substitution  occur,
496       and `\' quotes the characters `\', ``', `"', and `$'.
497

REDIRECTION

499       If  a  command is followed by & and job control is not active, then the
500       default standard input for the command is  the  empty  file  /dev/null.
501       Otherwise,  the environment for the execution of a command contains the
502       file descriptors of the invoking  shell  as  modified  by  input/output
503       specifications.
504
505       The following may appear anywhere in a simple command or may precede or
506       follow a complex command.  Expansion occurs before  word  or  digit  is
507       used except as noted below.  If the result of substitution on word pro‐
508       duces more than one filename,  redirection  occurs  for  each  separate
509       filename in turn.
510
511       < word Open file word for reading as standard input.
512
513       <> word
514              Open  file  word  for reading and writing as standard input.  If
515              the file does not exist then it is created.
516
517       > word Open file word for writing as standard output.  If the file does
518              not exist then it is created.  If the file exists, and the CLOB‐
519              BER option is unset, this causes  an  error;  otherwise,  it  is
520              truncated to zero length.
521
522       >| word
523       >! word
524              Same  as  >, except that the file is truncated to zero length if
525              it exists, even if CLOBBER is unset.
526
527       >> word
528              Open file word for writing in append mode  as  standard  output.
529              If  the  file  does  not exist, and the CLOBBER option is unset,
530              this causes an error; otherwise, the file is created.
531
532       >>| word
533       >>! word
534              Same as >>, except that the file  is  created  if  it  does  not
535              exist, even if CLOBBER is unset.
536
537       <<[-] word
538              The  shell  input is read up to a line that is the same as word,
539              or to an end-of-file.  No parameter expansion, command substitu‐
540              tion or filename generation is performed on word.  The resulting
541              document, called a here-document, becomes the standard input.
542
543              If any character of word is quoted with single or double  quotes
544              or a `\', no interpretation is placed upon the characters of the
545              document.  Otherwise, parameter and command substitution occurs,
546              `\'  followed  by  a newline is removed, and `\' must be used to
547              quote the characters `\', `$', ``' and the  first  character  of
548              word.
549
550              Note  that  word itself does not undergo shell expansion.  Back‐
551              quotes in word do not have  their  usual  effect;  instead  they
552              behave  similarly  to  double quotes, except that the backquotes
553              themselves are passed through unchanged.  (This  information  is
554              given for completeness and it is not recommended that backquotes
555              be used.)  Quotes in the form $'...' have their standard  effect
556              of expanding backslashed references to special characters.
557
558              If <<- is used, then all leading tabs are stripped from word and
559              from the document.
560
561       <<< word
562              Perform shell expansion on word and pass the result to  standard
563              input.  This is known as a here-string.  Compare the use of word
564              in here-documents above,  where  word  does  not  undergo  shell
565              expansion.
566
567       <& number
568       >& number
569              The  standard  input/output  is  duplicated from file descriptor
570              number (see dup2(2)).
571
572       <& -
573       >& -   Close the standard input/output.
574
575       <& p
576       >& p   The input/output from/to the coprocess is moved to the  standard
577              input/output.
578
579       >& word
580       &> word
581              (Except  where `>& word' matches one of the above syntaxes; `&>'
582              can always be used to avoid  this  ambiguity.)   Redirects  both
583              standard  output  and  standard error (file descriptor 2) in the
584              manner of `> word'.  Note that  this  does  not  have  the  same
585              effect as `> word 2>&1' in the presence of multios (see the sec‐
586              tion below).
587
588       >&| word
589       >&! word
590       &>| word
591       &>! word
592              Redirects both standard output and standard error (file descrip‐
593              tor 2) in the manner of `>| word'.
594
595       >>& word
596       &>> word
597              Redirects both standard output and standard error (file descrip‐
598              tor 2) in the manner of `>> word'.
599
600       >>&| word
601       >>&! word
602       &>>| word
603       &>>! word
604              Redirects both standard output and standard error (file descrip‐
605              tor 2) in the manner of `>>| word'.
606
607       If  one  of  the above is preceded by a digit, then the file descriptor
608       referred to is that specified by the digit instead of the default 0  or
609       1.   The order in which redirections are specified is significant.  The
610       shell evaluates each redirection in  terms  of  the  (file  descriptor,
611       file) association at the time of evaluation.  For example:
612
613              ... 1>fname 2>&1
614
615       first associates file descriptor 1 with file fname.  It then associates
616       file descriptor 2 with the file associated with file descriptor 1 (that
617       is,  fname).  If the order of redirections were reversed, file descrip‐
618       tor 2 would be associated with the terminal (assuming file descriptor 1
619       had  been)  and  then  file  descriptor 1 would be associated with file
620       fname.
621
622       The `|&' command separator described in Simple Commands & Pipelines  in
623       zshmisc(1) is a shorthand for `2>&1 |'.
624
625       The  various  forms of process substitution, `<(list)', and `=(list())'
626       for input and `>(list)' for output, are often used together with  redi‐
627       rection.   For example, if word in an output redirection is of the form
628       `>(list)' then the output is piped to the command represented by  list.
629       See Process Substitution in zshexpn(1).
630

OPENING FILE DESCRIPTORS USING PARAMETERS

632       When  the shell is parsing arguments to a command, and the shell option
633       IGNORE_BRACES is not set, a different form of redirection  is  allowed:
634       instead  of  a digit before the operator there is a valid shell identi‐
635       fier enclosed in braces.  The shell will open  a  new  file  descriptor
636       that is guaranteed to be at least 10 and set the parameter named by the
637       identifier to the file descriptor opened.   No  whitespace  is  allowed
638       between the closing brace and the redirection character.  For example:
639
640              ... {myfd}>&1
641
642       This opens a new file descriptor that is a duplicate of file descriptor
643       1 and sets the parameter myfd to the number  of  the  file  descriptor,
644       which  will  be at least 10.  The new file descriptor can be written to
645       using the syntax >&$myfd.
646
647       The syntax {varid}>&-, for example {myfd}>&-, may be used  to  close  a
648       file  descriptor opened in this fashion.  Note that the parameter given
649       by varid must previously be set to a file descriptor in this case.
650
651       It is an error to open or close a file descriptor in this fashion  when
652       the  parameter  is  readonly.   However,  it is not an error to read or
653       write a file descriptor using <&$param or >&$param if  param  is  read‐
654       only.
655
656       If  the option CLOBBER is unset, it is an error to open a file descrip‐
657       tor using a parameter that is already set to an  open  file  descriptor
658       previously allocated by this mechanism.  Unsetting the parameter before
659       using it for allocating a file descriptor avoids the error.
660
661       Note that this mechanism merely allocates or closes a file  descriptor;
662       it does not perform any redirections from or to it.  It is usually con‐
663       venient to allocate a file descriptor prior to use as  an  argument  to
664       exec.   The  syntax  does not in any case work when used around complex
665       commands such as parenthesised subshells or loops,  where  the  opening
666       brace  is  interpreted  as part of a command list to be executed in the
667       current shell.
668
669       The following shows a typical sequence of allocation, use, and  closing
670       of a file descriptor:
671
672              integer myfd
673              exec {myfd}>~/logs/mylogfile.txt
674              print This is a log message. >&$myfd
675              exec {myfd}>&-
676
677       Note  that  the  expansion  of  the  variable in the expression >&$myfd
678       occurs at the point the redirection  is  opened.   This  is  after  the
679       expansion  of  command arguments and after any redirections to the left
680       on the command line have been processed.
681

MULTIOS

683       If the user tries to open a file descriptor for writing more than once,
684       the  shell opens the file descriptor as a pipe to a process that copies
685       its input to all the specified outputs, similar to  tee,  provided  the
686       MULTIOS option is set, as it is by default.  Thus:
687
688              date >foo >bar
689
690       writes  the date to two files, named `foo' and `bar'.  Note that a pipe
691       is an implicit redirection; thus
692
693              date >foo | cat
694
695       writes the date to the file `foo', and also pipes it to cat.
696
697       If the MULTIOS option is set, the word after a redirection operator  is
698       also subjected to filename generation (globbing).  Thus
699
700              : > *
701
702       will  truncate  all files in the current directory, assuming there's at
703       least one.  (Without the MULTIOS option, it would create an empty  file
704       called `*'.)  Similarly, you can do
705
706              echo exit 0 >> *.sh
707
708       If the user tries to open a file descriptor for reading more than once,
709       the shell opens the file descriptor as a pipe to a process that  copies
710       all  the specified inputs to its output in the order specified, similar
711       to cat, provided the MULTIOS option is set.  Thus
712
713              sort <foo <fubar
714
715       or even
716
717              sort <f{oo,ubar}
718
719       is equivalent to `cat foo fubar | sort'.
720
721       Expansion of the redirection argument occurs at the point the redirect‐
722       ion  is  opened,  at the point described above for the expansion of the
723       variable in >&$myfd.
724
725       Note that a pipe is an implicit redirection; thus
726
727              cat bar | sort <foo
728
729       is equivalent to `cat bar foo | sort' (note the order of the inputs).
730
731       If the MULTIOS option is unset, each redirection replaces the  previous
732       redirection for that file descriptor.  However, all files redirected to
733       are actually opened, so
734
735              echo foo > bar > baz
736
737       when MULTIOS is unset will truncate bar, and write `foo' into baz.
738
739       There is a problem when an output multio is  attached  to  an  external
740       program.  A simple example shows this:
741
742              cat file >file1 >file2
743              cat file1 file2
744
745       Here,  it  is  possible that the second `cat' will not display the full
746       contents of file1  and  file2  (i.e.  the  original  contents  of  file
747       repeated twice).
748
749       The  reason  for  this  is  that  the multios are spawned after the cat
750       process is forked from the parent shell, so the parent shell  does  not
751       wait for the multios to finish writing data.  This means the command as
752       shown can exit before file1 and file2 are  completely  written.   As  a
753       workaround,  it  is possible to run the cat process as part of a job in
754       the current shell:
755
756              { cat file } >file >file2
757
758       Here, the {...} job will pause to wait for both files to be written.
759

REDIRECTIONS WITH NO COMMAND

761       When a simple command consists of one or more redirection operators and
762       zero or more parameter assignments, but no command name, zsh can behave
763       in several ways.
764
765       If the parameter NULLCMD is not set or the option CSH_NULLCMD  is  set,
766       an error is caused.  This is the csh behavior and CSH_NULLCMD is set by
767       default when emulating csh.
768
769       If the option SH_NULLCMD is set, the builtin `:' is inserted as a  com‐
770       mand  with  the given redirections.  This is the default when emulating
771       sh or ksh.
772
773       Otherwise, if the parameter NULLCMD is set, its value will be used as a
774       command  with  the given redirections.  If both NULLCMD and READNULLCMD
775       are set, then the value of the latter will be used instead of  that  of
776       the  former  when the redirection is an input.  The default for NULLCMD
777       is `cat' and for READNULLCMD is `more'. Thus
778
779              < file
780
781       shows the contents of file on standard output, with paging if that is a
782       terminal.  NULLCMD and READNULLCMD may refer to shell functions.
783

COMMAND EXECUTION

785       If a command name contains no slashes, the shell attempts to locate it.
786       If there exists a shell function by that name, the function is  invoked
787       as  described  in  the  section  `Functions'.   If there exists a shell
788       builtin by that name, the builtin is invoked.
789
790       Otherwise, the shell searches each element of  $path  for  a  directory
791       containing  an  executable  file by that name.  If the search is unsuc‐
792       cessful, the shell prints an error message and returns a  nonzero  exit
793       status.
794
795       If  execution  fails  because the file is not in executable format, and
796       the file is not a directory, it  is  assumed  to  be  a  shell  script.
797       /bin/sh  is  spawned to execute it.  If the program is a file beginning
798       with `#!', the remainder of the first line specifies an interpreter for
799       the program.  The shell will execute the specified interpreter on oper‐
800       ating systems that do not handle this executable format in the kernel.
801
802       If no external command is found but a  function  command_not_found_han‐
803       dler  exists  the  shell  executes  this function with all command line
804       arguments.  The function should return status zero if  it  successfully
805       handled  the  command,  or non-zero status if it failed.  In the latter
806       case the standard handling is applied: `command not found'  is  printed
807       to  standard  error and the shell exits with status 127.  Note that the
808       handler is executed in a subshell forked to execute  an  external  com‐
809       mand,  hence  changes  to  directories,  shell parameters, etc. have no
810       effect on the main shell.
811

FUNCTIONS

813       Shell functions are defined with the function reserved word or the spe‐
814       cial  syntax  `funcname  ()'.   Shell  functions are read in and stored
815       internally.  Alias names are resolved when the function is read.  Func‐
816       tions  are  executed  like  commands with the arguments passed as posi‐
817       tional parameters.  (See the section `Command Execution'.)
818
819       Functions execute in the same process as the caller and share all files
820       and  present  working  directory  with  the caller.  A trap on EXIT set
821       inside a function is executed after the function completes in the envi‐
822       ronment of the caller.
823
824       The return builtin is used to return from function calls.
825
826       Function  identifiers  can be listed with the functions builtin.  Func‐
827       tions can be undefined with the unfunction builtin.
828

AUTOLOADING FUNCTIONS

830       A function can be marked as undefined using the  autoload  builtin  (or
831       `functions  -u'  or `typeset -fu').  Such a function has no body.  When
832       the function is first executed, the shell searches for  its  definition
833       using the elements of the fpath variable.  Thus to define functions for
834       autoloading, a typical sequence is:
835
836              fpath=(~/myfuncs $fpath)
837              autoload myfunc1 myfunc2 ...
838
839       The usual alias expansion during reading  will  be  suppressed  if  the
840       autoload builtin or its equivalent is given the option -U. This is rec‐
841       ommended for the use of functions supplied with the  zsh  distribution.
842       Note  that  for functions precompiled with the zcompile builtin command
843       the flag -U must be provided when the .zwc file is created, as the cor‐
844       responding information is compiled into the latter.
845
846       For  each  element  in fpath, the shell looks for three possible files,
847       the newest of which is used to load the definition for the function:
848
849       element.zwc
850              A file created with  the  zcompile  builtin  command,  which  is
851              expected  to  contain  the  definitions for all functions in the
852              directory named element.  The file is treated in the same manner
853              as  a  directory  containing files for functions and is searched
854              for the definition of the function.   If the definition  is  not
855              found,  the  search for a definition proceeds with the other two
856              possibilities described below.
857
858              If element already includes a .zwc extension (i.e. the extension
859              was  explicitly  given by the user), element is searched for the
860              definition of the function without comparing its age to that  of
861              other  files;  in  fact, there does not need to be any directory
862              named element without the suffix.   Thus  including  an  element
863              such as `/usr/local/funcs.zwc' in fpath will speed up the search
864              for functions, with the  disadvantage  that  functions  included
865              must  be  explicitly recompiled by hand before the shell notices
866              any changes.
867
868       element/function.zwc
869              A file created with zcompile, which is expected to  contain  the
870              definition  for function.  It may include other function defini‐
871              tions as well, but those are neither loaded nor executed; a file
872              found  in  this way is searched only for the definition of func‐
873              tion.
874
875       element/function
876              A file of zsh command text, taken to be the definition for func‐
877              tion.
878
879       In  summary, the order of searching is, first, in the parents of direc‐
880       tories in fpath for the newer of  either  a  compiled  directory  or  a
881       directory  in fpath; second, if more than one of these contains a defi‐
882       nition for the function that is sought, the leftmost in  the  fpath  is
883       chosen;  and  third, within a directory, the newer of either a compiled
884       function or an ordinary function definition is used.
885
886       If the KSH_AUTOLOAD option is set, or the file contains only  a  simple
887       definition of the function, the file's contents will be executed.  This
888       will normally define the function in question,  but  may  also  perform
889       initialization, which is executed in the context of the function execu‐
890       tion, and may therefore define local parameters.  It is an error if the
891       function is not defined by loading the file.
892
893       Otherwise,  the  function body (with no surrounding `funcname() {...}')
894       is taken to be the complete contents of the file.  This form allows the
895       file  to be used directly as an executable shell script.  If processing
896       of the file results in the  function  being  re-defined,  the  function
897       itself  is  not re-executed.  To force the shell to perform initializa‐
898       tion and then call the function defined, the file should  contain  ini‐
899       tialization code (which will be executed then discarded) in addition to
900       a complete function definition (which will be retained  for  subsequent
901       calls to the function), and a call to the shell function, including any
902       arguments, at the end.
903
904       For example, suppose the autoload file func contains
905
906              func() { print This is func; }
907              print func is initialized
908
909       then `func; func' with KSH_AUTOLOAD set will produce both  messages  on
910       the  first  call, but only the message `This is func' on the second and
911       subsequent calls.  Without KSH_AUTOLOAD set, it will produce  the  ini‐
912       tialization  message  on  the  first call, and the other message on the
913       second and subsequent calls.
914
915       It is also possible  to  create  a  function  that  is  not  marked  as
916       autoloaded,  but  which loads its own definition by searching fpath, by
917       using `autoload -X' within a shell function.  For example, the  follow‐
918       ing are equivalent:
919
920              myfunc() {
921                autoload -X
922              }
923              myfunc args...
924
925       and
926
927              unfunction myfunc   # if myfunc was defined
928              autoload myfunc
929              myfunc args...
930
931       In  fact,  the  functions  command outputs `builtin autoload -X' as the
932       body of an autoloaded function.  This is done so that
933
934              eval "$(functions)"
935
936       produces a reasonable result.  A true autoloaded function can be  iden‐
937       tified  by  the  presence  of  the  comment  `# undefined' in the body,
938       because all comments are discarded from defined functions.
939
940       To load the definition of an autoloaded function myfunc without execut‐
941       ing myfunc, use:
942
943              autoload +X myfunc
944

ANONYMOUS FUNCTIONS

946       If  no  name  is given for a function, it is `anonymous' and is handled
947       specially.  Either form of function definition may be used: a `()' with
948       no  preceding  name, or a `function' with an immediately following open
949       brace.  The function is executed immediately at the point of definition
950       and  is  not  stored  for  future  use.   The  function  name is set to
951       `(anon)'.
952
953       Arguments to the function may be specified as words following the clos‐
954       ing  brace  defining the function, hence if there are none no arguments
955       (other than $0) are set.  This is a difference from the way other func‐
956       tions  are  parsed: normal function definitions may be followed by cer‐
957       tain keywords such as `else' or `fi', which will be  treated  as  argu‐
958       ments  to anonymous functions, so that a newline or semicolon is needed
959       to force keyword interpretation.
960
961       Note also that the argument list of any enclosing script or function is
962       hidden  (as  would  be  the  case for any other function called at this
963       point).
964
965       Redirections may be applied to the anonymous function in the same  man‐
966       ner  as  to a current-shell structure enclosed in braces.  The main use
967       of anonymous functions is to provide a scope for local variables.  This
968       is  particularly  convenient  in start-up files as these do not provide
969       their own local variable scope.
970
971       For example,
972
973              variable=outside
974              function {
975                local variable=inside
976                print "I am $variable with arguments $*"
977              } this and that
978              print "I am $variable"
979
980       outputs the following:
981
982              I am inside with arguments this and that
983              I am outside
984
985       Note that function definitions with arguments that expand  to  nothing,
986       for  example `name=; function $name { ... }', are not treated as anony‐
987       mous functions.  Instead, they are treated as normal  function  defini‐
988       tions where the definition is silently discarded.
989

SPECIAL FUNCTIONS

991       Certain functions, if defined, have special meaning to the shell.
992
993   Hook Functions
994       For the functions below, it is possible to define an array that has the
995       same name as the function with `_functions' appended.  Any  element  in
996       such an array is taken as the name of a function to execute; it is exe‐
997       cuted in the same context and with the  same  arguments  as  the  basic
998       function.   For example, if $chpwd_functions is an array containing the
999       values `mychpwd', `chpwd_save_dirstack', then  the  shell  attempts  to
1000       execute  the functions `chpwd', `mychpwd' and `chpwd_save_dirstack', in
1001       that order.  Any function that does not exist is silently  ignored.   A
1002       function  found  by  this mechanism is referred to elsewhere as a `hook
1003       function'.  An error in any function causes subsequent functions not to
1004       be  run.  Note further that an error in a precmd hook causes an immedi‐
1005       ately following periodic function not to run (though it may run at  the
1006       next opportunity).
1007
1008       chpwd  Executed whenever the current working directory is changed.
1009
1010       periodic
1011              If  the parameter PERIOD is set, this function is executed every
1012              $PERIOD seconds, just before a prompt.  Note  that  if  multiple
1013              functions  are  defined  using the array periodic_functions only
1014              one period is applied to the complete set of functions, and  the
1015              scheduled time is not reset if the list of functions is altered.
1016              Hence the set of functions is always called together.
1017
1018       precmd Executed before each prompt.  Note that precommand functions are
1019              not  re-executed  simply because the command line is redrawn, as
1020              happens, for example, when a notification about an  exiting  job
1021              is displayed.
1022
1023       preexec
1024              Executed  just  after a command has been read and is about to be
1025              executed.  If the history mechanism is active (and the line  was
1026              not discarded from the history buffer), the string that the user
1027              typed is passed as the first argument, otherwise it is an  empty
1028              string.   The  actual  command  that will be executed (including
1029              expanded aliases) is passed in two different forms:  the  second
1030              argument  is  a single-line, size-limited version of the command
1031              (with things like function bodies elided);  the  third  argument
1032              contains the full text that is being executed.
1033
1034       zshaddhistory
1035              Executed  when  a  history line has been read interactively, but
1036              before it is executed.  The sole argument is the  complete  his‐
1037              tory  line  (so  that  any  terminating  newline  will  still be
1038              present).
1039
1040              If any of the hook functions return a non-zero value the history
1041              line will not be saved, although it lingers in the history until
1042              the next line is executed allow you to reuse or edit it  immedi‐
1043              ately.
1044
1045              A  hook function may call `fc -p ...' to switch the history con‐
1046              text so that the history is saved in a different file  from  the
1047              that  in  the  global  HISTFILE parameter.  This is handled spe‐
1048              cially: the history context is automatically restored after  the
1049              processing of the history line is finished.
1050
1051              The  following  example  function first adds the history line to
1052              the normal history with the newline stripped,  which is  usually
1053              the  correct behaviour.  Then it switches the history context so
1054              that the line will be written to a history file in  the  current
1055              directory.
1056
1057                     zshaddhistory() {
1058                       print -sr -- ${1%%$'\n'}
1059                       fc -p .zsh_local_history
1060                     }
1061
1062       zshexit
1063              Executed at the point where the main shell is about to exit nor‐
1064              mally.  This is not called by exiting subshells,  nor  when  the
1065              exec  precommand  modifier  is  used before an external command.
1066              Also, unlike TRAPEXIT, it is not called when functions exit.
1067
1068   Trap Functions
1069       The functions below are treated specially but do not have corresponding
1070       hook arrays.
1071
1072       TRAPNAL
1073              If defined and non-null, this function will be executed whenever
1074              the shell catches a signal SIGNAL, where NAL is a signal name as
1075              specified  for  the  kill  builtin.   The  signal number will be
1076              passed as the first parameter to the function.
1077
1078              If a function of this form is defined and null,  the  shell  and
1079              processes spawned by it will ignore SIGNAL.
1080
1081              The return status from the function is handled specially.  If it
1082              is zero, the signal is assumed to have been handled, and  execu‐
1083              tion  continues  normally.   Otherwise, the shell will behave as
1084              interrupted except  that  the  return  status  of  the  trap  is
1085              retained.
1086
1087              Programs  terminated  by  uncaught  signals typically return the
1088              status 128 plus the signal number.  Hence the  following  causes
1089              the  handler for SIGINT to print a message, then mimic the usual
1090              effect of the signal.
1091
1092                     TRAPINT() {
1093                       print "Caught SIGINT, aborting."
1094                       return $(( 128 + $1 ))
1095                     }
1096
1097              The functions TRAPZERR, TRAPDEBUG and TRAPEXIT  are  never  exe‐
1098              cuted inside other traps.
1099
1100       TRAPDEBUG
1101              If  the  option  DEBUG_BEFORE_CMD  is set (as it is by default),
1102              executed before each command; otherwise executed after each com‐
1103              mand.  See the description of the trap builtin in zshbuiltins(1)
1104              for details of additional features provided in debug traps.
1105
1106       TRAPEXIT
1107              Executed when the shell exits,  or  when  the  current  function
1108              exits  if  defined  inside  a  function.  The value of $? at the
1109              start of execution is the exit status of the shell or the return
1110              status of the function exiting.
1111
1112       TRAPZERR
1113              Executed  whenever  a  command has a non-zero exit status.  How‐
1114              ever, the function is not executed if the command occurred in  a
1115              sublist  followed  by  `&&' or `||'; only the final command in a
1116              sublist of this type causes the trap to be executed.  The  func‐
1117              tion TRAPERR acts the same as TRAPZERR on systems where there is
1118              no SIGERR (this is the usual case).
1119
1120       The functions beginning `TRAP' may alternatively be  defined  with  the
1121       trap  builtin:   this  may be preferable for some uses.  Setting a trap
1122       with one form removes any trap of the other form for the  same  signal;
1123       removing  a  trap in either form removes all traps for the same signal.
1124       The forms
1125
1126              TRAPNAL() {
1127               # code
1128              }
1129
1130       ('function traps') and
1131
1132              trap '
1133               # code
1134              ' NAL
1135
1136       ('list traps') are equivalent in most ways, the  exceptions  being  the
1137       following:
1138
1139       ·      Function  traps  have  all  the  properties of normal functions,
1140              appearing in the list of functions and being called  with  their
1141              own  function context rather than the context where the trap was
1142              triggered.
1143
1144       ·      The return status from function  traps  is  special,  whereas  a
1145              return from a list trap causes the surrounding context to return
1146              with the given status.
1147
1148       ·      Function traps are not reset  within  subshells,  in  accordance
1149              with  zsh  behaviour;  list  traps are reset, in accordance with
1150              POSIX behaviour.
1151

JOBS

1153       If the MONITOR option is set, an interactive  shell  associates  a  job
1154       with  each  pipeline.  It keeps a table of current jobs, printed by the
1155       jobs command, and assigns them small integer numbers.  When  a  job  is
1156       started  asynchronously  with  `&', the shell prints a line to standard
1157       error which looks like:
1158
1159              [1] 1234
1160
1161       indicating that the job which was started asynchronously was job number
1162       1 and had one (top-level) process, whose process ID was 1234.
1163
1164       If  a  job  is  started with `&|' or `&!', then that job is immediately
1165       disowned.  After startup, it does not have a place in  the  job  table,
1166       and is not subject to the job control features described here.
1167
1168       If  you are running a job and wish to do something else you may hit the
1169       key ^Z (control-Z) which sends a TSTP signal to the current job:   this
1170       key  may  be redefined by the susp option of the external stty command.
1171       The shell will then normally indicate  that  the  job  has  been  `sus‐
1172       pended',  and  print another prompt.  You can then manipulate the state
1173       of this job, putting it in the background with the bg command,  or  run
1174       some  other  commands  and  then eventually bring the job back into the
1175       foreground with the foreground command fg.  A ^Z takes  effect  immedi‐
1176       ately  and is like an interrupt in that pending output and unread input
1177       are discarded when it is typed.
1178
1179       A job being run in the background will suspend if it tries to read from
1180       the terminal.
1181
1182       Note  that  if  the  job running in the foreground is a shell function,
1183       then suspending it will have the effect of causing the shell  to  fork.
1184       This  is  necessary  to  separate the function's state from that of the
1185       parent shell performing the job control, so that the latter can  return
1186       to  the  command  line prompt.  As a result, even if fg is used to con‐
1187       tinue the job the function will no longer be part of the parent  shell,
1188       and any variables set by the function will not be visible in the parent
1189       shell.  Thus the behaviour is different from the case where  the  func‐
1190       tion  was  never suspended.  Zsh is different from many other shells in
1191       this regard.
1192
1193       The same behaviour is found when the shell is  executing  code  as  the
1194       right  hand  side  of a pipeline or any complex shell construct such as
1195       if, for, etc., in order that the entire block of code can be managed as
1196       a  single job.  Background jobs are normally allowed to produce output,
1197       but this can be disabled by giving the command `stty tostop'.   If  you
1198       set this tty option, then background jobs will suspend when they try to
1199       produce output like they do when they try to read input.
1200
1201       When a command is suspended and continued later with  the  fg  or  wait
1202       builtins,  zsh  restores tty modes that were in effect when it was sus‐
1203       pended.  This (intentionally) does not apply if the command is  contin‐
1204       ued via `kill -CONT', nor when it is continued with bg.
1205
1206       There  are  several  ways  to refer to jobs in the shell.  A job can be
1207       referred to by the process ID of any process of the job or  by  one  of
1208       the following:
1209
1210       %number
1211              The job with the given number.
1212       %string
1213              Any job whose command line begins with string.
1214       %?string
1215              Any job whose command line contains string.
1216       %%     Current job.
1217       %+     Equivalent to `%%'.
1218       %-     Previous job.
1219
1220       The shell learns immediately whenever a process changes state.  It nor‐
1221       mally informs you whenever a job becomes blocked  so  that  no  further
1222       progress  is possible.  If the NOTIFY option is not set, it waits until
1223       just before it prints a prompt before it informs you.  All such notifi‐
1224       cations  are  sent directly to the terminal, not to the standard output
1225       or standard error.
1226
1227       When the monitor mode is on, each background job that  completes  trig‐
1228       gers any trap set for CHLD.
1229
1230       When  you  try  to leave the shell while jobs are running or suspended,
1231       you will be warned that `You have suspended (running) jobs'.   You  may
1232       use  the  jobs command to see what they are.  If you do this or immedi‐
1233       ately try to exit again, the shell will not warn you a second time; the
1234       suspended  jobs will be terminated, and the running jobs will be sent a
1235       SIGHUP signal, if the HUP option is set.
1236
1237       To avoid having the shell terminate the running jobs,  either  use  the
1238       nohup command (see nohup(1)) or the disown builtin.
1239

SIGNALS

1241       The INT and QUIT signals for an invoked command are ignored if the com‐
1242       mand is followed by `&' and the MONITOR  option  is  not  active.   The
1243       shell  itself  always ignores the QUIT signal.  Otherwise, signals have
1244       the values inherited by the shell from its parent (but see the  TRAPNAL
1245       special functions in the section `Functions').
1246

ARITHMETIC EVALUATION

1248       The  shell  can  perform  integer and floating point arithmetic, either
1249       using the builtin let, or via a substitution of the form $((...)).  For
1250       integers,  the  shell is usually compiled to use 8-byte precision where
1251       this is available, otherwise precision is 4 bytes.  This can be tested,
1252       for example, by giving the command `print - $(( 12345678901 ))'; if the
1253       number appears unchanged, the precision is at least 8 bytes.   Floating
1254       point  arithmetic  always  uses  the `double' type with whatever corre‐
1255       sponding precision is provided by the compiler and the library.
1256
1257       The let builtin command takes arithmetic expressions as arguments; each
1258       is  evaluated  separately.   Since many of the arithmetic operators, as
1259       well as spaces, require quoting, an alternative form is  provided:  for
1260       any command which begins with a `((', all the characters until a match‐
1261       ing `))' are treated as a quoted expression  and  arithmetic  expansion
1262       performed  as  for  an  argument  of let.  More precisely, `((...))' is
1263       equivalent to `let "..."'.  The return status is 0  if  the  arithmetic
1264       value of the expression is non-zero, 1 if it is zero, and 2 if an error
1265       occurred.
1266
1267       For example, the following statement
1268
1269              (( val = 2 + 1 ))
1270
1271       is equivalent to
1272
1273              let "val = 2 + 1"
1274
1275       both assigning the value 3 to the shell variable val  and  returning  a
1276       zero status.
1277
1278       Integers can be in bases other than 10.  A leading `0x' or `0X' denotes
1279       hexadecimal.  Integers may also be of the form `base#n', where base  is
1280       a decimal number between two and thirty-six representing the arithmetic
1281       base and n is a number in that base (for example,  `16#ff'  is  255  in
1282       hexadecimal).   The base# may also be omitted, in which case base 10 is
1283       used.  For backwards compatibility the form `[base]n' is also accepted.
1284
1285       An integer expression or a base given in the form `base#n' may  contain
1286       underscores  (`_')  after  the leading digit for visual guidance; these
1287       are ignored in computation.   Examples  are  1_000_000  or  0xffff_ffff
1288       which are equivalent to 1000000 and 0xffffffff respectively.
1289
1290       It is also possible to specify a base to be used for output in the form
1291       `[#base]', for example `[#16]'.  This is used  when  outputting  arith‐
1292       metical  substitutions  or  when assigning to scalar parameters, but an
1293       explicitly defined integer or floating  point  parameter  will  not  be
1294       affected.   If  an  integer variable is implicitly defined by an arith‐
1295       metic expression, any base specified in this way will  be  set  as  the
1296       variable's  output  arithmetic  base  as if the option `-i base' to the
1297       typeset builtin had been used.  The expression has no precedence and if
1298       it occurs more than once in a mathematical expression, the last encoun‐
1299       tered is used.  For clarity it is recommended that  it  appear  at  the
1300       beginning of an expression.  As an example:
1301
1302              typeset -i 16 y
1303              print $(( [#8] x = 32, y = 32 ))
1304              print $x $y
1305
1306       outputs first `8#40', the rightmost value in the given output base, and
1307       then `8#40 16#20', because y has been explicitly declared to have  out‐
1308       put base 16, while x (assuming it does not already exist) is implicitly
1309       typed by the arithmetic evaluation, where it acquires the  output  base
1310       8.
1311
1312       If  the  C_BASES  option  is set, hexadecimal numbers in the standard C
1313       format, for example 0xFF instead of the usual `16#FF'.  If  the  option
1314       OCTAL_ZEROES  is also set (it is not by default), octal numbers will be
1315       treated similarly and hence appear as `077' instead  of  `8#77'.   This
1316       option  has no effect on the output of bases other than hexadecimal and
1317       octal, and these formats are always understood on input.
1318
1319       When an output base is specified using the `[#base]' syntax, an  appro‐
1320       priate  base prefix will be output if necessary, so that the value out‐
1321       put is valid syntax for input.   If  the  #  is  doubled,  for  example
1322       `[##16]', then no base prefix is output.
1323
1324       Floating  point  constants  are recognized by the presence of a decimal
1325       point or an exponent.  The decimal point may be the first character  of
1326       the  constant, but the exponent character e or E may not, as it will be
1327       taken for a parameter name.  All numeric parts (before  and  after  the
1328       decimal  point  and  in the exponent) may contain underscores after the
1329       leading digit for visual guidance; these are ignored in computation.
1330
1331       An arithmetic expression uses nearly the same syntax and  associativity
1332       of expressions as in C.
1333
1334       In  the native mode of operation, the following operators are supported
1335       (listed in decreasing order of precedence):
1336
1337       + - ! ~ ++ --
1338              unary plus/minus, logical NOT, complement, {pre,post}{in,de}cre‐
1339              ment
1340       << >>  bitwise shift left, right
1341       &      bitwise AND
1342       ^      bitwise XOR
1343       |      bitwise OR
1344       **     exponentiation
1345       * / %  multiplication, division, modulus (remainder)
1346       + -    addition, subtraction
1347       < > <= >=
1348              comparison
1349       == !=  equality and inequality
1350       &&     logical AND
1351       || ^^  logical OR, XOR
1352       ? :    ternary operator
1353       = += -= *= /= %= &= ^= |= <<= >>= &&= ||= ^^= **=
1354              assignment
1355       ,      comma operator
1356
1357       The  operators  `&&',  `||', `&&=', and `||=' are short-circuiting, and
1358       only one of the latter two expressions in a ternary operator is  evalu‐
1359       ated.  Note the precedence of the bitwise AND, OR, and XOR operators.
1360
1361       With the option C_PRECEDENCES the precedences (but no other properties)
1362       of the operators are altered to be the same as those in most other lan‐
1363       guages that support the relevant operators:
1364
1365       + - ! ~ ++ --
1366              unary plus/minus, logical NOT, complement, {pre,post}{in,de}cre‐
1367              ment
1368       **     exponentiation
1369       * / %  multiplication, division, modulus (remainder)
1370       + -    addition, subtraction
1371       << >>  bitwise shift left, right
1372       < > <= >=
1373              comparison
1374       == !=  equality and inequality
1375       &      bitwise AND
1376       ^      bitwise XOR
1377       |      bitwise OR
1378       &&     logical AND
1379       ^^     logical XOR
1380       ||     logical OR
1381       ? :    ternary operator
1382       = += -= *= /= %= &= ^= |= <<= >>= &&= ||= ^^= **=
1383              assignment
1384       ,      comma operator
1385
1386       Note the precedence of exponentiation in both cases is  below  that  of
1387       unary operators, hence `-3**2' evaluates as `9', not -9.  Use parenthe‐
1388       ses where necessary: `-(3**2)'.  This is for compatibility  with  other
1389       shells.
1390
1391       Mathematical  functions  can  be  called  with the syntax `func(args)',
1392       where the function decides if the  args  is  used  as  a  string  or  a
1393       comma-separated  list  of  arithmetic  expressions. The shell currently
1394       defines no mathematical functions by default, but the module  zsh/math‐
1395       func may be loaded with the zmodload builtin to provide standard float‐
1396       ing point mathematical functions.
1397
1398       An expression of the form `##x' where x is any character sequence  such
1399       as  `a',  `^A',  or  `\M-\C-x' gives the value of this character and an
1400       expression of the form `#foo' gives the value of the first character of
1401       the  contents  of the parameter foo.  Character values are according to
1402       the character set used in the current locale; for  multibyte  character
1403       handling the option MULTIBYTE must be set.  Note that this form is dif‐
1404       ferent from `$#foo', a standard parameter substitution which gives  the
1405       length of the parameter foo.  `#\' is accepted instead of `##', but its
1406       use is deprecated.
1407
1408       Named parameters and subscripted  arrays  can  be  referenced  by  name
1409       within  an  arithmetic expression without using the parameter expansion
1410       syntax.  For example,
1411
1412              ((val2 = val1 * 2))
1413
1414       assigns twice the value of $val1 to the parameter named val2.
1415
1416       An internal integer representation of a named parameter can  be  speci‐
1417       fied  with  the integer builtin.  Arithmetic evaluation is performed on
1418       the value of each assignment to a named parameter declared  integer  in
1419       this  manner.   Assigning a floating point number to an integer results
1420       in rounding down to the next integer.
1421
1422       Likewise, floating  point  numbers  can  be  declared  with  the  float
1423       builtin; there are two types, differing only in their output format, as
1424       described for the typeset builtin.  The output format can  be  bypassed
1425       by using arithmetic substitution instead of the parameter substitution,
1426       i.e. `${float}' uses  the  defined  format,  but  `$((float))'  uses  a
1427       generic floating point format.
1428
1429       Promotion of integer to floating point values is performed where neces‐
1430       sary.  In addition, if any operator which  requires  an  integer  (`~',
1431       `&',  `|',  `^', `%', `<<', `>>' and their equivalents with assignment)
1432       is given a floating point argument, it will be silently rounded down to
1433       the next integer.
1434
1435       Scalar variables can hold integer or floating point values at different
1436       times; there is no memory of the numeric type in this case.
1437
1438       If a variable is first assigned in a numeric context without previously
1439       being  declared,  it  will  be implicitly typed as integer or float and
1440       retain that type either until the type is explicitly changed  or  until
1441       the  end  of  the  scope.   This can have unforeseen consequences.  For
1442       example, in the loop
1443
1444              for (( f = 0; f < 1; f += 0.1 )); do
1445              # use $f
1446              done
1447
1448       if f has not already been declared, the first assignment will cause  it
1449       to  be created as an integer, and consequently the operation `f += 0.1'
1450       will always cause the result to be truncated to zero, so that the  loop
1451       will  fail.  A simple fix would be to turn the initialization into `f =
1452       0.0'.  It is therefore best to declare numeric variables with  explicit
1453       types.
1454

CONDITIONAL EXPRESSIONS

1456       A  conditional  expression is used with the [[ compound command to test
1457       attributes of files and to compare strings.   Each  expression  can  be
1458       constructed  from  one or more of the following unary or binary expres‐
1459       sions:
1460
1461       -a file
1462              true if file exists.
1463
1464       -b file
1465              true if file exists and is a block special file.
1466
1467       -c file
1468              true if file exists and is a character special file.
1469
1470       -d file
1471              true if file exists and is a directory.
1472
1473       -e file
1474              true if file exists.
1475
1476       -f file
1477              true if file exists and is a regular file.
1478
1479       -g file
1480              true if file exists and has its setgid bit set.
1481
1482       -h file
1483              true if file exists and is a symbolic link.
1484
1485       -k file
1486              true if file exists and has its sticky bit set.
1487
1488       -n string
1489              true if length of string is non-zero.
1490
1491       -o option
1492              true if option named option is on.  option may be a single char‐
1493              acter,  in  which  case it is a single letter option name.  (See
1494              the section `Specifying Options'.)
1495
1496       -p file
1497              true if file exists and is a FIFO special file (named pipe).
1498
1499       -r file
1500              true if file exists and is readable by current process.
1501
1502       -s file
1503              true if file exists and has size greater than zero.
1504
1505       -t fd  true if file descriptor number fd is open and associated with  a
1506              terminal device.  (note: fd is not optional)
1507
1508       -u file
1509              true if file exists and has its setuid bit set.
1510
1511       -w file
1512              true if file exists and is writable by current process.
1513
1514       -x file
1515              true  if  file  exists and is executable by current process.  If
1516              file exists and is a directory, then  the  current  process  has
1517              permission to search in the directory.
1518
1519       -z string
1520              true if length of string is zero.
1521
1522       -L file
1523              true if file exists and is a symbolic link.
1524
1525       -O file
1526              true  if  file  exists  and is owned by the effective user ID of
1527              this process.
1528
1529       -G file
1530              true if file exists and its group matches the effective group ID
1531              of this process.
1532
1533       -S file
1534              true if file exists and is a socket.
1535
1536       -N file
1537              true  if  file  exists and its access time is not newer than its
1538              modification time.
1539
1540       file1 -nt file2
1541              true if file1 exists and is newer than file2.
1542
1543       file1 -ot file2
1544              true if file1 exists and is older than file2.
1545
1546       file1 -ef file2
1547              true if file1 and file2 exist and refer to the same file.
1548
1549       string = pattern
1550       string == pattern
1551              true if string matches pattern.  The `==' form is the  preferred
1552              one.   The  `=' form is for backward compatibility and should be
1553              considered obsolete.
1554
1555       string != pattern
1556              true if string does not match pattern.
1557
1558       string =~ regexp
1559              true if string matches the regular expression  regexp.   If  the
1560              option  RE_MATCH_PCRE  is set regexp is tested as a PCRE regular
1561              expression using the zsh/pcre module, else it  is  tested  as  a
1562              POSIX  extended  regular  expression using the zsh/regex module.
1563              Upon successful match, some variables will be updated; no  vari‐
1564              ables are changed if the matching fails.
1565
1566              If the option BASH_REMATCH is not set the scalar parameter MATCH
1567              is set to the substring that matched the pattern and the integer
1568              parameters  MBEGIN  and  MEND to the index of the start and end,
1569              respectively, of the match in string, such  that  if  string  is
1570              contained in variable var the expression `${var[$MBEGIN,$MEND]}'
1571              is identical to `$MATCH'.  The setting of the option  KSH_ARRAYS
1572              is  respected.   Likewise,  the  array  match is set to the sub‐
1573              strings that matched parenthesised subexpressions and the arrays
1574              mbegin  and  mend to the indices of the start and end positions,
1575              respectively, of the substrings within string.  The  arrays  are
1576              not  set  if  there  were no parenthesised subexpresssions.  For
1577              example, if the string `a short string' is matched  against  the
1578              regular   expression   `s(...)t',   then  (assuming  the  option
1579              KSH_ARRAYS is not set) MATCH, MBEGIN and MEND are `short', 3 and
1580              7,  respectively,  while match, mbegin and mend are single entry
1581              arrays containing the strings `hor', `4' and `6, respectively.
1582
1583              If the option BASH_REMATCH is set the array BASH_REMATCH is  set
1584              to  the  substring that matched the pattern followed by the sub‐
1585              strings that matched  parenthesised  subexpressions  within  the
1586              pattern.
1587
1588       string1 < string2
1589              true  if  string1  comes  before string2 based on ASCII value of
1590              their characters.
1591
1592       string1 > string2
1593              true if string1 comes after string2  based  on  ASCII  value  of
1594              their characters.
1595
1596       exp1 -eq exp2
1597              true if exp1 is numerically equal to exp2.  Note that for purely
1598              numeric comparisons use of the ((...)) builtin described in  the
1599              section  `ARITHMETIC  EVALUATION' is more convenient than condi‐
1600              tional expressions.
1601
1602       exp1 -ne exp2
1603              true if exp1 is numerically not equal to exp2.
1604
1605       exp1 -lt exp2
1606              true if exp1 is numerically less than exp2.
1607
1608       exp1 -gt exp2
1609              true if exp1 is numerically greater than exp2.
1610
1611       exp1 -le exp2
1612              true if exp1 is numerically less than or equal to exp2.
1613
1614       exp1 -ge exp2
1615              true if exp1 is numerically greater than or equal to exp2.
1616
1617       ( exp )
1618              true if exp is true.
1619
1620       ! exp  true if exp is false.
1621
1622       exp1 && exp2
1623              true if exp1 and exp2 are both true.
1624
1625       exp1 || exp2
1626              true if either exp1 or exp2 is true.
1627
1628       Normal shell expansion is performed on the  file,  string  and  pattern
1629       arguments, but the result of each expansion is constrained to be a sin‐
1630       gle word, similar to the effect of double quotes.  Filename  generation
1631       is  not performed on any form of argument to conditions.  However, pat‐
1632       tern metacharacters are active for the pattern arguments; the  patterns
1633       are the same as those used for filename generation, see zshexpn(1), but
1634       there is no special behaviour of `/' nor  initial  dots,  and  no  glob
1635       qualifiers are allowed.
1636
1637       In  each  of the above expressions, if file is of the form `/dev/fd/n',
1638       where n is an integer, then the test applied to  the  open  file  whose
1639       descriptor  number is n, even if the underlying system does not support
1640       the /dev/fd directory.
1641
1642       In the forms which do numeric comparison, the expressions  exp  undergo
1643       arithmetic expansion as if they were enclosed in $((...)).
1644
1645       For example, the following:
1646
1647              [[ ( -f foo || -f bar ) && $report = y* ]] && print File exists.
1648
1649       tests if either file foo or file bar exists, and if so, if the value of
1650       the parameter report begins with `y';  if  the  complete  condition  is
1651       true, the message `File exists.' is printed.
1652

EXPANSION OF PROMPT SEQUENCES

1654       Prompt  sequences  undergo  a  special form of expansion.  This type of
1655       expansion is also available using the -P option to the print builtin.
1656
1657       If the PROMPT_SUBST option is set, the prompt string is first subjected
1658       to  parameter expansion, command substitution and arithmetic expansion.
1659       See zshexpn(1).
1660
1661       Certain escape sequences may be recognised in the prompt string.
1662
1663       If the PROMPT_BANG option is set, a `!' in the prompt  is  replaced  by
1664       the  current  history  event  number.  A literal `!' may then be repre‐
1665       sented as `!!'.
1666
1667       If the PROMPT_PERCENT option is  set,  certain  escape  sequences  that
1668       start  with  `%'  are  expanded.  Many escapes are followed by a single
1669       character, although some of these take  an  optional  integer  argument
1670       that  should  appear  between  the  `%'  and  the next character of the
1671       sequence.  More complicated escape sequences are available  to  provide
1672       conditional expansion.
1673

SIMPLE PROMPT ESCAPES

1675   Special characters
1676       %%     A `%'.
1677
1678       %)     A `)'.
1679
1680   Login information
1681       %l     The line (tty) the user is logged in on, without `/dev/' prefix.
1682              If the name starts with `/dev/tty', that prefix is stripped.
1683
1684       %M     The full machine hostname.
1685
1686       %m     The hostname up to the first `.'.  An integer may follow the `%'
1687              to  specify  how  many  components  of the hostname are desired.
1688              With a negative integer, trailing components of the hostname are
1689              shown.
1690
1691       %n     $USERNAME.
1692
1693       %y     The line (tty) the user is logged in on, without `/dev/' prefix.
1694              This does not treat `/dev/tty' names specially.
1695
1696   Shell state
1697       %#     A `#' if the shell is running with privileges,  a  `%'  if  not.
1698              Equivalent  to `%(!.#.%%)'.  The definition of `privileged', for
1699              these purposes, is that either the effective user  ID  is  zero,
1700              or,  if  POSIX.1e  capabilities are supported, that at least one
1701              capability is raised in  either  the  Effective  or  Inheritable
1702              capability vectors.
1703
1704       %?     The  return  status of the last command executed just before the
1705              prompt.
1706
1707       %_     The status of the parser, i.e. the shell constructs  (like  `if'
1708              and  `for') that have been started on the command line. If given
1709              an integer number that many strings will  be  printed;  zero  or
1710              negative  or  no integer means print as many as there are.  This
1711              is most useful in prompts PS2 for continuation lines and PS4 for
1712              debugging  with  the  XTRACE  option; in the latter case it will
1713              also work non-interactively.
1714
1715       %d
1716       /      Current working directory.  If an integer follows  the  `%',  it
1717              specifies a number of trailing components of the current working
1718              directory to show; zero means the whole path.  A negative  inte‐
1719              ger  specifies leading components, i.e. %-1d specifies the first
1720              component.
1721
1722       %~     As %d and %/, but if the current working directory has  a  named
1723              directory as its prefix, that part is replaced by a `~' followed
1724              by the name of the directory.  If it  starts  with  $HOME,  that
1725              part is replaced by a `~'.
1726
1727       %h
1728       %!     Current history event number.
1729
1730       %i     The  line number currently being executed in the script, sourced
1731              file, or shell function given by %N.  This is  most  useful  for
1732              debugging as part of $PS4.
1733
1734       %I     The  line  number currently being executed in the file %x.  This
1735              is similar to %i, but the line number is always a line number in
1736              the file where the code was defined, even if the code is a shell
1737              function.
1738
1739       %j     The number of jobs.
1740
1741       %L     The current value of $SHLVL.
1742
1743       %N     The name of the script, sourced file, or shell function that zsh
1744              is currently executing, whichever was started most recently.  If
1745              there is none, this is equivalent to the parameter $0.  An inte‐
1746              ger may follow the `%' to specify a number of trailing path com‐
1747              ponents to show; zero means the full path.  A  negative  integer
1748              specifies leading components.
1749
1750       %x     The  name of the file containing the source code currently being
1751              executed.  This behaves as %N except that function and eval com‐
1752              mand  names  are  not  shown,  instead  the file where they were
1753              defined.
1754
1755       %c
1756       %.
1757       %C     Trailing component of the current working directory.  An integer
1758              may  follow the `%' to get more than one component.  Unless `%C'
1759              is used, tilde contraction is performed first.  These are depre‐
1760              cated  as %c and %C are equivalent to %1~ and %1/, respectively,
1761              while explicit positive integers have the same effect as for the
1762              latter two sequences.
1763
1764   Date and time
1765       %D     The date in yy-mm-dd format.
1766
1767       %T     Current time of day, in 24-hour format.
1768
1769       %t
1770       %@     Current time of day, in 12-hour, am/pm format.
1771
1772       %*     Current time of day in 24-hour format, with seconds.
1773
1774       %w     The date in day-dd format.
1775
1776       %W     The date in mm/dd/yy format.
1777
1778       %D{string}
1779              string  is  formatted  using  the  strftime function.  See strf‐
1780              time(3) for more details.  Various zsh extensions  provide  num‐
1781              bers  with  no  leading  zero or space if the number is a single
1782              digit:
1783
1784              %f     a day of the month
1785              %K     the hour of the day on the 24-hour clock
1786              %L     the hour of the day on the 12-hour clock
1787
1788              The GNU extension that a `-' between the % and the format  char‐
1789              acter  causes  a leading zero or space to be stripped is handled
1790              directly by the shell for the format characters d, f, H,  k,  l,
1791              m, M, S and y; any other format characters are provided to strf‐
1792              time() with any leading `-', present, so the handling is  system
1793              dependent.  Further GNU extensions are not supported at present.
1794
1795   Visual effects
1796       %B (%b)
1797              Start (stop) boldface mode.
1798
1799       %E     Clear to end of line.
1800
1801       %U (%u)
1802              Start (stop) underline mode.
1803
1804       %S (%s)
1805              Start (stop) standout mode.
1806
1807       %F (%f)
1808              Start  (stop)  using a different foreground colour, if supported
1809              by the terminal.  The colour may be specified two  ways:  either
1810              as  a  numeric  argument,  as normal, or by a sequence in braces
1811              following the %F, for example %F{red}.  In the latter  case  the
1812              values  allowed  are  as  described  for  the  fg  zle_highlight
1813              attribute; see Character Highlighting in zshzle(1).  This  means
1814              that numeric colours are allowed in the second format also.
1815
1816       %K (%k)
1817              Start (stop) using a different bacKground colour.  The syntax is
1818              identical to that for %F and %f.
1819
1820       %{...%}
1821              Include a string as  a  literal  escape  sequence.   The  string
1822              within  the braces should not change the cursor position.  Brace
1823              pairs can nest.
1824
1825              A positive numeric argument between the % and the {  is  treated
1826              as described for %G below.
1827
1828       %G     Within  a  %{...%} sequence, include a `glitch': that is, assume
1829              that a single character width will be output.   This  is  useful
1830              when  outputting  characters  that otherwise cannot be correctly
1831              handled by the shell, such as the  alternate  character  set  on
1832              some  terminals.   The  characters  in  question can be included
1833              within a %{...%} sequence together with the  appropriate  number
1834              of  %G  sequences  to  indicate  the  correct width.  An integer
1835              between the `%' and `G' indicates a character width  other  than
1836              one.   Hence  %{seq%2G%} outputs seq and assumes it takes up the
1837              width of two standard characters.
1838
1839              Multiple uses of %G accumulate in the obvious fashion; the posi‐
1840              tion  of  the %G is unimportant.  Negative integers are not han‐
1841              dled.
1842
1843              Note that when prompt truncation is in use it  is  advisable  to
1844              divide  up  output  into  single  characters within each %{...%}
1845              group so that the correct truncation point can be found.
1846

CONDITIONAL SUBSTRINGS IN PROMPTS

1848       %v     The value of the first element of  the  psvar  array  parameter.
1849              Following  the  `%'  with  an  integer gives that element of the
1850              array.  Negative integers count from the end of the array.
1851
1852       %(x.true-text.false-text)
1853              Specifies a ternary expression.  The character following  the  x
1854              is  arbitrary;  the  same character is used to separate the text
1855              for the `true' result from that for the  `false'  result.   This
1856              separator  may  not appear in the true-text, except as part of a
1857              %-escape sequence.  A `)' may appear in the false-text as  `%)'.
1858              true-text  and  false-text  may  both contain arbitrarily-nested
1859              escape sequences, including further ternary expressions.
1860
1861              The left parenthesis may be preceded or followed by  a  positive
1862              integer  n,  which defaults to zero.  A negative integer will be
1863              multiplied by -1.  The test character x may be any of  the  fol‐
1864              lowing:
1865
1866              !      True if the shell is running with privileges.
1867              #      True if the effective uid of the current process is n.
1868              ?      True if the exit status of the last command was n.
1869              _      True if at least n shell constructs were started.
1870              C
1871              /      True if the current absolute path has at least n elements
1872                     relative to the root directory, hence / is counted  as  0
1873                     elements.
1874              c
1875              .
1876              ~      True if the current path, with prefix replacement, has at
1877                     least n elements relative to the root directory, hence  /
1878                     is counted as 0 elements.
1879              D      True if the month is equal to n (January = 0).
1880              d      True if the day of the month is equal to n.
1881              g      True if the effective gid of the current process is n.
1882              j      True if the number of jobs is at least n.
1883              L      True if the SHLVL parameter is at least n.
1884              l      True  if  at least n characters have already been printed
1885                     on the current line.
1886              S      True if the SECONDS parameter is at least n.
1887              T      True if the time in hours is equal to n.
1888              t      True if the time in minutes is equal to n.
1889              v      True if the array psvar has at least n elements.
1890              V      True  if  element  n  of  the  array  psvar  is  set  and
1891                     non-empty.
1892              w      True if the day of the week is equal to n (Sunday = 0).
1893
1894       %<string<
1895       %>string>
1896       %[xstring]
1897              Specifies  truncation  behaviour for the remainder of the prompt
1898              string.   The  third,  deprecated,   form   is   equivalent   to
1899              `%xstringx',  i.e.  x  may be `<' or `>'.  The numeric argument,
1900              which in the third form may appear immediately  after  the  `[',
1901              specifies  the  maximum  permitted length of the various strings
1902              that can be displayed in the prompt.  The string  will  be  dis‐
1903              played  in  place  of  the truncated portion of any string; note
1904              this does not undergo prompt expansion.
1905
1906              The forms with `<' truncate at the left of the string,  and  the
1907              forms  with  `>' truncate at the right of the string.  For exam‐
1908              ple, if  the  current  directory  is  `/home/pike',  the  prompt
1909              `%8<..<%/'  will expand to `..e/pike'.  In this string, the ter‐
1910              minating character (`<', `>' or `]'), or in fact any  character,
1911              may be quoted by a preceding `\'; note when using print -P, how‐
1912              ever, that this must be doubled as the string is also subject to
1913              standard  print  processing,  in  addition  to  any  backslashes
1914              removed by a double quoted string:  the worst case is  therefore
1915              `print -P "%<\\\\<<..."'.
1916
1917              If the string is longer than the specified truncation length, it
1918              will appear in full, completely replacing the truncated string.
1919
1920              The part of the prompt string to be truncated runs to the end of
1921              the  string,  or  to  the end of the next enclosing group of the
1922              `%(' construct, or to the next  truncation  encountered  at  the
1923              same  grouping  level  (i.e. truncations inside a `%(' are sepa‐
1924              rate), which ever comes first.  In particular, a truncation with
1925              argument  zero  (e.g.  `%<<')  marks the end of the range of the
1926              string to be truncated while turning off truncation  from  there
1927              on.  For  example,  the  prompt  '%10<...<%~%<<%# ' will print a
1928              truncated representation of the current directory, followed by a
1929              `%'  or  `#', followed by a space.  Without the `%<<', those two
1930              characters would be included in the string to be truncated.
1931
1932
1933
1934zsh 5.0.2                      December 21, 2012                    ZSHMISC(1)
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