1ZSHEXPN(1)                  General Commands Manual                 ZSHEXPN(1)
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3
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NAME

6       zshexpn - zsh expansion and substitution
7

DESCRIPTION

9       The  following types of expansions are performed in the indicated order
10       in five steps:
11
12       History Expansion
13              This is performed only in interactive shells.
14
15       Alias Expansion
16              Aliases are expanded immediately  before  the  command  line  is
17              parsed as explained under Aliasing in zshmisc(1).
18
19       Process Substitution
20       Parameter Expansion
21       Command Substitution
22       Arithmetic Expansion
23       Brace Expansion
24              These  five  are  performed  in  left-to-right fashion.  On each
25              argument, any of the five steps that are  needed  are  performed
26              one  after  the  other.   Hence,  for  example, all the parts of
27              parameter expansion are completed before command substitution is
28              started.   After  these  expansions, all unquoted occurrences of
29              the characters `\',`'' and `"' are removed.
30
31       Filename Expansion
32              If the SH_FILE_EXPANSION option is set, the order  of  expansion
33              is  modified  for  compatibility  with sh and ksh.  In that case
34              filename expansion is performed immediately after  alias  expan‐
35              sion, preceding the set of five expansions mentioned above.
36
37       Filename Generation
38              This expansion, commonly referred to as globbing, is always done
39              last.
40
41       The following sections explain the types of expansion in detail.
42

HISTORY EXPANSION

44       History expansion allows you to use words from previous  command  lines
45       in  the  command line you are typing.  This simplifies spelling correc‐
46       tions and the repetition of complicated commands or arguments.
47
48       Immediately before execution, each command  is  saved  in  the  history
49       list,  the  size of which is controlled by the HISTSIZE parameter.  The
50       one most recent command is always retained in  any  case.   Each  saved
51       command in the history list is called a history event and is assigned a
52       number, beginning with 1 (one) when the shell starts up.   The  history
53       number  that  you  may  see  in  your  prompt  (see EXPANSION OF PROMPT
54       SEQUENCES in zshmisc(1)) is the number that is to be  assigned  to  the
55       next command.
56
57   Overview
58       A  history  expansion  begins with the first character of the histchars
59       parameter, which is `!' by default, and may occur anywhere on the  com‐
60       mand line, including inside double quotes (but not inside single quotes
61       '...' or C-style quotes $'...' nor when escaped with a backslash).
62
63       The first character is followed by an optional  event  designator  (see
64       the  section  `Event Designators') and then an optional word designator
65       (the section `Word Designators'); if neither of  these  designators  is
66       present, no history expansion occurs.
67
68       Input  lines  containing  history  expansions  are  echoed  after being
69       expanded, but before any other expansions take  place  and  before  the
70       command  is executed.  It is this expanded form that is recorded as the
71       history event for later references.
72
73       History expansions do not nest.
74
75       By default, a history reference with no event designator refers to  the
76       same  event as any preceding history reference on that command line; if
77       it is the only history reference in a command, it refers to the  previ‐
78       ous  command.   However,  if the option CSH_JUNKIE_HISTORY is set, then
79       every history reference with no event specification  always  refers  to
80       the previous command.
81
82       For  example,  `!' is the event designator for the previous command, so
83       `!!:1' always refers to the first word of  the  previous  command,  and
84       `!!$'  always  refers  to  the last word of the previous command.  With
85       CSH_JUNKIE_HISTORY set, then `!:1' and `!$' function in the same manner
86       as  `!!:1'  and `!!$', respectively.  Conversely, if CSH_JUNKIE_HISTORY
87       is unset, then `!:1' and `!$'  refer  to  the  first  and  last  words,
88       respectively, of the same event referenced by the nearest other history
89       reference preceding them on the current command line, or to the  previ‐
90       ous command if there is no preceding reference.
91
92       The  character  sequence  `^foo^bar'  (where `^' is actually the second
93       character of the histchars parameter) repeats the last command, replac‐
94       ing  the string foo with bar.  More precisely, the sequence `^foo^bar^'
95       is synonymous with `!!:s^foo^bar^', hence other modifiers (see the sec‐
96       tion   `Modifiers')   may   follow   the  final  `^'.   In  particular,
97       `^foo^bar^:G' performs a global substitution.
98
99       If the shell encounters the character sequence `!"' in the  input,  the
100       history  mechanism  is temporarily disabled until the current list (see
101       zshmisc(1)) is fully parsed.  The `!"' is removed from the  input,  and
102       any subsequent `!' characters have no special significance.
103
104       A  less convenient but more comprehensible form of command history sup‐
105       port is provided by the fc builtin.
106
107   Event Designators
108       An event designator is a reference to a command-line entry in the  his‐
109       tory  list.   In  the list below, remember that the initial `!' in each
110       item may be changed to  another  character  by  setting  the  histchars
111       parameter.
112
113       !      Start a history expansion, except when followed by a blank, new‐
114              line, `=' or `('.  If followed immediately by a word  designator
115              (see  the section `Word Designators'), this forms a history ref‐
116              erence with no event designator (see the section `Overview').
117
118       !!     Refer to  the  previous  command.   By  itself,  this  expansion
119              repeats the previous command.
120
121       !n     Refer to command-line n.
122
123       !-n    Refer to the current command-line minus n.
124
125       !str   Refer to the most recent command starting with str.
126
127       !?str[?]
128              Refer  to  the most recent command containing str.  The trailing
129              `?' is necessary if this reference is to be followed by a  modi‐
130              fier  or  followed by any text that is not to be considered part
131              of str.
132
133       !#     Refer to the current command line typed in so far.  The line  is
134              treated  as  if  it  were  complete up to and including the word
135              before the one with the `!#' reference.
136
137       !{...} Insulate a history reference from adjacent characters (if neces‐
138              sary).
139
140   Word Designators
141       A word designator indicates which word or words of a given command line
142       are to be included in a history reference.  A `:' usually separates the
143       event  specification  from the word designator.  It may be omitted only
144       if the word designator begins with a `^', `$', `*', `-' or  `%'.   Word
145       designators include:
146
147       0      The first input word (command).
148       n      The nth argument.
149       ^      The first argument.  That is, 1.
150       $      The last argument.
151       %      The word matched by (the most recent) ?str search.
152       x-y    A range of words; x defaults to 0.
153       *      All the arguments, or a null value if there are none.
154       x*     Abbreviates `x-$'.
155       x-     Like `x*' but omitting word $.
156
157       Note  that  a  `%' word designator works only when used in one of `!%',
158       `!:%' or `!?str?:%', and only when used after a !? expansion  (possibly
159       in  an  earlier  command).  Anything else results in an error, although
160       the error may not be the most obvious one.
161
162   Modifiers
163       After the optional word designator, you can add a sequence  of  one  or
164       more  of  the following modifiers, each preceded by a `:'.  These modi‐
165       fiers also work on the result  of  filename  generation  and  parameter
166       expansion, except where noted.
167
168       a      Turn  a  file  name into an absolute path:  prepends the current
169              directory, if necessary; remove `.' path  segments;  and  remove
170              `..'  path  segments  and  the segments that immediately precede
171              them.
172
173              This transformation is agnostic about what is in the filesystem,
174              i.e.  is  on  the logical, not the physical directory.  It takes
175              place in the same manner as when changing directories when  nei‐
176              ther of the options CHASE_DOTS or CHASE_LINKS is set.  For exam‐
177              ple,   `/before/here/../after'   is   always   transformed    to
178              `/before/after',  regardless of whether `/before/here' exists or
179              what kind of object (dir, file, symlink, etc.) it is.
180
181       A      Turn a file name into an absolute path as the `a' modifier does,
182              and  then  pass the result through the realpath(3) library func‐
183              tion to resolve symbolic links.
184
185              Note: on systems that do not have a  realpath(3)  library  func‐
186              tion,  symbolic  links are not resolved, so on those systems `a'
187              and `A' are equivalent.
188
189              Note: foo:A and realpath(foo) are different on some inputs.  For
190              realpath(foo) semantics, see the `P` modifier.
191
192       c      Resolve  a  command  name into an absolute path by searching the
193              command path given by the PATH variable.  This does not work for
194              commands  containing  directory parts.  Note also that this does
195              not usually work as a glob qualifier unless a file of  the  same
196              name is found in the current directory.
197
198       e      Remove  all but the part of the filename extension following the
199              `.'; see  the  definition  of  the  filename  extension  in  the
200              description  of  the  r  modifier below.  Note that according to
201              that definition the result will be empty if the string ends with
202              a `.'.
203
204       h      Remove  a  trailing  pathname component, leaving the head.  This
205              works like `dirname'.
206
207       l      Convert the words to all lowercase.
208
209       p      Print the new command but do not execute it.   Only  works  with
210              history expansion.
211
212       P      Turn  a  file name into an absolute path, like realpath(3).  The
213              resulting path will be absolute, have neither `.' nor `..'  com‐
214              ponents,  and  refer  to  the  same directory entry as the input
215              filename.
216
217              Unlike realpath(3), non-existent trailing components are permit‐
218              ted and preserved.
219
220       q      Quote  the  substituted  words,  escaping further substitutions.
221              Works with history expansion and parameter expansion, though for
222              parameters  it  is  only  useful  if the resulting text is to be
223              re-evaluated such as by eval.
224
225       Q      Remove one level of quotes from the substituted words.
226
227       r      Remove a filename extension leaving the root name.  Strings with
228              no  filename extension are not altered.  A filename extension is
229              a `.' followed by any number of characters (including zero) that
230              are  neither  `.'  nor  `/'  and that continue to the end of the
231              string.  For example, the extension of `foo.orig.c' is `.c', and
232              `dir.c/foo' has no extension.
233
234       s/l/r[/]
235              Substitute r for l as described below.  The substitution is done
236              only for the first string that matches l.  For  arrays  and  for
237              filename  generation,  this applies to each word of the expanded
238              text.  See below for further notes on substitutions.
239
240              The forms `gs/l/r' and `s/l/r/:G' perform  global  substitution,
241              i.e. substitute every occurrence of r for l.  Note that the g or
242              :G must appear in exactly the position shown.
243
244              See further notes on this form of substitution below.
245
246       &      Repeat the previous s substitution.  Like  s,  may  be  preceded
247              immediately  by  a  g.  In parameter expansion the & must appear
248              inside braces, and in filename generation it must be quoted with
249              a backslash.
250
251       t      Remove  all leading pathname components, leaving the tail.  This
252              works like `basename'.
253
254       u      Convert the words to all uppercase.
255
256       x      Like q, but break into words at whitespace.  Does not work  with
257              parameter expansion.
258
259       The  s/l/r/  substitution  works  as follows.  By default the left-hand
260       side of substitutions are not patterns,  but  character  strings.   Any
261       character  can  be  used as the delimiter in place of `/'.  A backslash
262       quotes  the  delimiter  character.    The   character   `&',   in   the
263       right-hand-side  r,  is replaced by the text from the left-hand-side l.
264       The `&' can be quoted with a backslash.  A null  l  uses  the  previous
265       string  either from the previous l or from the contextual scan string s
266       from `!?s'.  You can omit the rightmost delimiter if a newline  immedi‐
267       ately  follows  r; the rightmost `?' in a context scan can similarly be
268       omitted.  Note the same record of the last l and r is maintained across
269       all forms of expansion.
270
271       Note that if a `&' is used within glob qualifiers an extra backslash is
272       needed as a & is a special character in this case.
273
274       Also note that the order of expansions affects the interpretation of  l
275       and r.  When used in a history expansion, which occurs before any other
276       expansions, l and r are treated as literal strings (except as explained
277       for  HIST_SUBST_PATTERN  below).  When used in parameter expansion, the
278       replacement of r into the parameter's value is done first, and then any
279       additional process, parameter, command, arithmetic, or brace references
280       are applied, which may evaluate those substitutions and expansions more
281       than once if l appears more than once in the starting value.  When used
282       in a glob qualifier, any substitutions or expansions are performed once
283       at  the  time  the qualifier is parsed, even before the `:s' expression
284       itself is divided into l and r sides.
285
286       If the option HIST_SUBST_PATTERN is set, l is treated as a  pattern  of
287       the  usual  form  described  in  the section FILENAME GENERATION below.
288       This can be used in all the places where modifiers are available; note,
289       however, that in globbing qualifiers parameter substitution has already
290       taken place, so parameters in the replacement string should  be  quoted
291       to  ensure  they are replaced at the correct time.  Note also that com‐
292       plicated patterns used in globbing qualifiers  may  need  the  extended
293       glob  qualifier notation (#q:s/.../.../) in order for the shell to rec‐
294       ognize the expression as a glob qualifier.  Further, note that bad pat‐
295       terns  in the substitution are not subject to the NO_BAD_PATTERN option
296       so will cause an error.
297
298       When HIST_SUBST_PATTERN is set, l may start with a # to  indicate  that
299       the  pattern  must  match at the start of the string to be substituted,
300       and a % may appear at the start or after an # to indicate that the pat‐
301       tern must match at the end of the string to be substituted.  The % or #
302       may be quoted with two backslashes.
303
304       For example, the following piece of filename generation code  with  the
305       EXTENDED_GLOB option:
306
307              print *.c(#q:s/#%(#b)s(*).c/'S${match[1]}.C'/)
308
309       takes  the  expansion  of  *.c  and  applies the glob qualifiers in the
310       (#q...) expression, which consists of a substitution modifier  anchored
311       to  the  start and end of each word (#%).  This turns on backreferences
312       ((#b)), so that the parenthesised subexpression  is  available  in  the
313       replacement string as ${match[1]}.  The replacement string is quoted so
314       that the parameter is not substituted before the start of filename gen‐
315       eration.
316
317       The  following  f, F, w and W modifiers work only with parameter expan‐
318       sion and filename generation.  They are listed here to provide a single
319       point of reference for all modifiers.
320
321       f      Repeats  the  immediately  (without  a colon) following modifier
322              until the resulting word doesn't change any more.
323
324       F:expr:
325              Like f, but repeats only n times if the expression  expr  evalu‐
326              ates  to  n.   Any  character can be used instead of the `:'; if
327              `(', `[', or `{' is used as the opening delimiter,  the  closing
328              delimiter should be ')', `]', or `}', respectively.
329
330       w      Makes  the  immediately  following modifier work on each word in
331              the string.
332
333       W:sep: Like w but words are considered to be the parts  of  the  string
334              that  are separated by sep. Any character can be used instead of
335              the `:'; opening parentheses are handled specially, see above.
336

PROCESS SUBSTITUTION

338       Each part  of  a  command  argument  that  takes  the  form  `<(list)',
339       `>(list)' or `=(list)' is subject to process substitution.  The expres‐
340       sion may be preceded or followed by other strings except that, to  pre‐
341       vent  clashes  with  commonly  occurring strings and patterns, the last
342       form must occur at the start of a command argument, and the  forms  are
343       only  expanded  when  first  parsing  command  or assignment arguments.
344       Process substitutions may be used following redirection  operators;  in
345       this case, the substitution must appear with no trailing string.
346
347       Note  that  `<<(list)'  is not a special syntax; it is equivalent to `<
348       <(list)', redirecting standard input from the result of process substi‐
349       tution.   Hence  all  the  following documentation applies.  The second
350       form (with the space) is recommended for clarity.
351
352       In the case of the < or > forms, the shell runs the commands in list as
353       a  subprocess of the job executing the shell command line.  If the sys‐
354       tem supports the /dev/fd mechanism, the command argument is the name of
355       the  device  file corresponding to a file descriptor; otherwise, if the
356       system supports named pipes (FIFOs), the command  argument  will  be  a
357       named  pipe.   If the form with > is selected then writing on this spe‐
358       cial file will provide input for list.  If < is  used,  then  the  file
359       passed  as  an  argument  will  be  connected to the output of the list
360       process.  For example,
361
362              paste <(cut -f1 file1) <(cut -f3 file2) |
363              tee >(process1) >(process2) >/dev/null
364
365       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
366       the  results  together,  and  sends  it  to  the processes process1 and
367       process2.
368
369       If =(...) is used instead of <(...), then the file passed as  an  argu‐
370       ment  will be the name of a temporary file containing the output of the
371       list process.  This may be used instead of the <  form  for  a  program
372       that expects to lseek (see lseek(2)) on the input file.
373
374       There is an optimisation for substitutions of the form =(<<<arg), where
375       arg is a single-word argument to the here-string redirection <<<.  This
376       form produces a file name containing the value of arg after any substi‐
377       tutions have been performed.  This is handled entirely within the  cur‐
378       rent  shell.   This  is  effectively  the  reverse  of the special form
379       $(<arg) which treats arg as a file name and replaces it with the file's
380       contents.
381
382       The = form is useful as both the /dev/fd and the named pipe implementa‐
383       tion of <(...) have drawbacks.  In the former case, some programmes may
384       automatically  close  the  file descriptor in question before examining
385       the file on the command line, particularly if  this  is  necessary  for
386       security  reasons such as when the programme is running setuid.  In the
387       second case, if the programme does not actually open the file, the sub‐
388       shell  attempting  to read from or write to the pipe will (in a typical
389       implementation, different operating systems may have  different  behav‐
390       iour)  block for ever and have to be killed explicitly.  In both cases,
391       the shell actually supplies the information using a pipe, so that  pro‐
392       grammes that expect to lseek (see lseek(2)) on the file will not work.
393
394       Also  note  that  the  previous example can be more compactly and effi‐
395       ciently written (provided the MULTIOS option is set) as:
396
397              paste <(cut -f1 file1) <(cut -f3 file2) \
398              > >(process1) > >(process2)
399
400       The shell uses pipes instead of  FIFOs  to  implement  the  latter  two
401       process substitutions in the above example.
402
403       There  is  an additional problem with >(process); when this is attached
404       to an external command, the parent shell does not wait for  process  to
405       finish  and  hence  an immediately following command cannot rely on the
406       results being complete.  The problem  and  solution  are  the  same  as
407       described  in the section MULTIOS in zshmisc(1).  Hence in a simplified
408       version of the example above:
409
410              paste <(cut -f1 file1) <(cut -f3 file2) > >(process)
411
412       (note that no MULTIOS are involved), process will be run asynchronously
413       as far as the parent shell is concerned.  The workaround is:
414
415              { paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)
416
417       The  extra  processes here are spawned from the parent shell which will
418       wait for their completion.
419
420       Another problem arises any time a job with a substitution that requires
421       a  temporary  file  is  disowned by the shell, including the case where
422       `&!' or `&|' appears at the end of a command containing a substitution.
423       In  that case the temporary file will not be cleaned up as the shell no
424       longer has any memory of the job.  A workaround is to use  a  subshell,
425       for example,
426
427              (mycmd =(myoutput)) &!
428
429       as  the forked subshell will wait for the command to finish then remove
430       the temporary file.
431
432       A general workaround to ensure a process substitution  endures  for  an
433       appropriate length of time is to pass it as a parameter to an anonymous
434       shell function (a piece of shell code  that  is  run  immediately  with
435       function scope).  For example, this code:
436
437              () {
438                 print File $1:
439                 cat $1
440              } =(print This be the verse)
441
442       outputs something resembling the following
443
444              File /tmp/zsh6nU0kS:
445              This be the verse
446
447       The  temporary file created by the process substitution will be deleted
448       when the function exits.
449

PARAMETER EXPANSION

451       The character `$' is used to introduce parameter expansions.  See  zsh‐
452       param(1) for a description of parameters, including arrays, associative
453       arrays, and subscript notation to access individual array elements.
454
455       Note in particular the fact that words of unquoted parameters  are  not
456       automatically  split  on  whitespace unless the option SH_WORD_SPLIT is
457       set; see references to this option below for more details.  This is  an
458       important difference from other shells.
459
460       In  the  expansions discussed below that require a pattern, the form of
461       the pattern is the same as that used for filename generation;  see  the
462       section  `Filename  Generation'.   Note that these patterns, along with
463       the replacement text of any substitutions, are  themselves  subject  to
464       parameter  expansion,  command  substitution, and arithmetic expansion.
465       In addition to the following operations, the colon modifiers  described
466       in  the  section  `Modifiers' in the section `History Expansion' can be
467       applied:  for example, ${i:s/foo/bar/} performs string substitution  on
468       the expansion of parameter $i.
469
470       In  the  following descriptions, `word' refers to a single word substi‐
471       tuted on the command line, not  necessarily  a  space  delimited  word.
472       With default options, after the assignments:
473
474              array=("first word" "second word")
475              scalar="only word"
476
477       then  $array substitutes two words, `first word' and `second word', and
478       $scalar substitutes a single word `only word'.  This may be modified by
479       explicit  or implicit word-splitting, however.  The full rules are com‐
480       plicated and are noted at the end.
481
482       ${name}
483              The value, if any, of the parameter name  is  substituted.   The
484              braces are required if the expansion is to be followed by a let‐
485              ter, digit, or underscore that is not to be interpreted as  part
486              of  name.   In  addition, more complicated forms of substitution
487              usually require the braces to be present; exceptions, which only
488              apply  if  the  option  KSH_ARRAYS is not set, are a single sub‐
489              script or any colon modifiers appearing after the name,  or  any
490              of the characters `^', `=', `~', `#' or `+' appearing before the
491              name, all of which work with or without braces.
492
493              If name is an array parameter, and the KSH_ARRAYS option is  not
494              set,  then the value of each element of name is substituted, one
495              element per word.  Otherwise, the expansion results in one  word
496              only;  with  KSH_ARRAYS,  this is the first element of an array.
497              No  field  splitting  is  done  on   the   result   unless   the
498              SH_WORD_SPLIT   option  is  set.   See  also  the  flags  =  and
499              s:string:.
500
501       ${+name}
502              If name is the name of a set parameter `1' is substituted,  oth‐
503              erwise `0' is substituted.
504
505       ${name-word}
506       ${name:-word}
507              If  name is set, or in the second form is non-null, then substi‐
508              tute its value; otherwise substitute word.  In the  second  form
509              name may be omitted, in which case word is always substituted.
510
511       ${name+word}
512       ${name:+word}
513              If  name is set, or in the second form is non-null, then substi‐
514              tute word; otherwise substitute nothing.
515
516       ${name=word}
517       ${name:=word}
518       ${name::=word}
519              In the first form, if name is unset then set it to word; in  the
520              second  form,  if name is unset or null then set it to word; and
521              in the third form, unconditionally set name  to  word.   In  all
522              forms, the value of the parameter is then substituted.
523
524       ${name?word}
525       ${name:?word}
526              In the first form, if name is set, or in the second form if name
527              is both set and non-null, then substitute its value;  otherwise,
528              print  word and exit from the shell.  Interactive shells instead
529              return to the prompt.  If word is omitted, then a standard  mes‐
530              sage is printed.
531
532       In  any of the above expressions that test a variable and substitute an
533       alternate word, note that you can use standard  shell  quoting  in  the
534       word   value   to  selectively  override  the  splitting  done  by  the
535       SH_WORD_SPLIT option and the = flag, but not splitting by the s:string:
536       flag.
537
538       In  the  following expressions, when name is an array and the substitu‐
539       tion is not quoted, or if the `(@)' flag or the name[@] syntax is used,
540       matching and replacement is performed on each array element separately.
541
542       ${name#pattern}
543       ${name##pattern}
544              If  the pattern matches the beginning of the value of name, then
545              substitute the value of name with the matched  portion  deleted;
546              otherwise,  just  substitute  the  value  of name.  In the first
547              form, the smallest matching pattern is preferred; in the  second
548              form, the largest matching pattern is preferred.
549
550       ${name%pattern}
551       ${name%%pattern}
552              If  the  pattern matches the end of the value of name, then sub‐
553              stitute the value of name with the matched portion deleted; oth‐
554              erwise,  just  substitute the value of name.  In the first form,
555              the smallest matching pattern is preferred; in the second  form,
556              the largest matching pattern is preferred.
557
558       ${name:#pattern}
559              If  the  pattern  matches the value of name, then substitute the
560              empty string; otherwise, just substitute the value of name.   If
561              name  is  an  array the matching array elements are removed (use
562              the `(M)' flag to remove the non-matched elements).
563
564       ${name:|arrayname}
565              If arrayname is the name (N.B., not contents) of an array  vari‐
566              able,  then any elements contained in arrayname are removed from
567              the substitution of name.  If the substitution is scalar, either
568              because  name  is a scalar variable or the expression is quoted,
569              the elements of arrayname are instead tested against the  entire
570              expression.
571
572       ${name:*arrayname}
573              Similar  to  the  preceding  substitution,  but  in the opposite
574              sense, so that entries present in both the original substitution
575              and as elements of arrayname are retained and others removed.
576
577       ${name:^arrayname}
578       ${name:^^arrayname}
579              Zips  two arrays, such that the output array is twice as long as
580              the shortest (longest for `:^^') of name and arrayname, with the
581              elements  alternatingly being picked from them. For `:^', if one
582              of the input arrays is longer, the output will stop when the end
583              of the shorter array is reached.  Thus,
584
585                     a=(1 2 3 4); b=(a b); print ${a:^b}
586
587              will  output  `1  a 2 b'.  For `:^^', then the input is repeated
588              until all of the longer array has been used  up  and  the  above
589              will output `1 a 2 b 3 a 4 b'.
590
591              Either  or  both inputs may be a scalar, they will be treated as
592              an array of length 1 with the scalar as  the  only  element.  If
593              either  array  is empty, the other array is output with no extra
594              elements inserted.
595
596              Currently the following code will output `a b' and  `1'  as  two
597              separate  elements,  which  can  be unexpected. The second print
598              provides a workaround which should continue to work if  this  is
599              changed.
600
601                     a=(a b); b=(1 2); print -l "${a:^b}"; print -l "${${a:^b}}"
602
603       ${name:offset}
604       ${name:offset:length}
605              This  syntax  gives effects similar to parameter subscripting in
606              the form $name[start,end], but is compatible with other  shells;
607              note  that  both  offset  and length are interpreted differently
608              from the components of a subscript.
609
610              If offset is non-negative, then if the variable name is a scalar
611              substitute  the  contents  starting  offset  characters from the
612              first character of the string, and if name is an  array  substi‐
613              tute  elements  starting offset elements from the first element.
614              If length is given, substitute that many characters or elements,
615              otherwise the entire rest of the scalar or array.
616
617              A positive offset is always treated as the offset of a character
618              or element in name from the first character or  element  of  the
619              array  (this  is  different from native zsh subscript notation).
620              Hence 0 refers to the first character or element  regardless  of
621              the setting of the option KSH_ARRAYS.
622
623              A negative offset counts backwards from the end of the scalar or
624              array, so that -1 corresponds to the last character or  element,
625              and so on.
626
627              When positive, length counts from the offset position toward the
628              end of the scalar or array.  When negative, length  counts  back
629              from  the  end.  If this results in a position smaller than off‐
630              set, a diagnostic is printed and nothing is substituted.
631
632              The option MULTIBYTE is obeyed, i.e. the offset and length count
633              multibyte characters where appropriate.
634
635              offset and length undergo the same set of shell substitutions as
636              for scalar assignment; in addition, they  are  then  subject  to
637              arithmetic evaluation.  Hence, for example
638
639                     print ${foo:3}
640                     print ${foo: 1 + 2}
641                     print ${foo:$(( 1 + 2))}
642                     print ${foo:$(echo 1 + 2)}
643
644              all  have the same effect, extracting the string starting at the
645              fourth character of $foo if  the  substitution  would  otherwise
646              return  a scalar, or the array starting at the fourth element if
647              $foo  would  return  an  array.   Note  that  with  the   option
648              KSH_ARRAYS  $foo  always returns a scalar (regardless of the use
649              of the offset syntax) and a form such as ${foo[*]:3} is required
650              to extract elements of an array named foo.
651
652              If  offset  is  negative, the - may not appear immediately after
653              the : as this indicates the ${name:-word} form of  substitution.
654              Instead,  a  space  may  be inserted before the -.  Furthermore,
655              neither offset nor length may begin with an alphabetic character
656              or  & as these are used to indicate history-style modifiers.  To
657              substitute a value from a variable, the recommended approach  is
658              to  precede it with a $ as this signifies the intention (parame‐
659              ter substitution can easily be rendered unreadable); however, as
660              arithmetic  substitution  is  performed,  the  expression ${var:
661              offs} does work, retrieving the offset from $offs.
662
663              For further compatibility with other shells there is  a  special
664              case  for  array offset 0.  This usually accesses the first ele‐
665              ment of the array.  However, if the substitution refers  to  the
666              positional parameter array, e.g. $@ or $*, then offset 0 instead
667              refers to $0, offset 1 refers to $1, and so on.  In other words,
668              the  positional  parameter  array  is  effectively  extended  by
669              prepending $0.  Hence ${*:0:1} substitutes $0 and ${*:1:1}  sub‐
670              stitutes $1.
671
672       ${name/pattern/repl}
673       ${name//pattern/repl}
674       ${name:/pattern/repl}
675              Replace  the  longest possible match of pattern in the expansion
676              of parameter name by string repl.  The first form replaces  just
677              the  first  occurrence, the second form all occurrences, and the
678              third form replaces only if pattern matches the  entire  string.
679              Both pattern and repl are subject to double-quoted substitution,
680              so that expressions like ${name/$opat/$npat} will work, but obey
681              the  usual rule that pattern characters in $opat are not treated
682              specially unless either the option GLOB_SUBST is set,  or  $opat
683              is instead substituted as ${~opat}.
684
685              The pattern may begin with a `#', in which case the pattern must
686              match at the start of the string, or `%', in which case it  must
687              match  at  the end of the string, or `#%' in which case the pat‐
688              tern must match the entire string.  The repl  may  be  an  empty
689              string,  in  which  case  the final `/' may also be omitted.  To
690              quote the final `/' in other cases it should be  preceded  by  a
691              single backslash; this is not necessary if the `/' occurs inside
692              a substituted parameter.  Note also that the `#',  `%'  and  `#%
693              are  not  active  if  they occur inside a substituted parameter,
694              even at the start.
695
696              If, after quoting rules apply, ${name} expands to an array,  the
697              replacements  act  on  each element individually.  Note also the
698              effect of the I and S parameter expansion flags below;  however,
699              the flags M, R, B, E and N are not useful.
700
701              For example,
702
703                     foo="twinkle twinkle little star" sub="t*e" rep="spy"
704                     print ${foo//${~sub}/$rep}
705                     print ${(S)foo//${~sub}/$rep}
706
707              Here, the `~' ensures that the text of $sub is treated as a pat‐
708              tern rather than a plain string.  In the first case, the longest
709              match for t*e is substituted and the result is `spy star', while
710              in the second case, the  shortest  matches  are  taken  and  the
711              result is `spy spy lispy star'.
712
713       ${#spec}
714              If spec is one of the above substitutions, substitute the length
715              in characters of the result instead of the  result  itself.   If
716              spec  is  an array expression, substitute the number of elements
717              of the result.  This has the side-effect that joining is skipped
718              even  in quoted forms, which may affect other sub-expressions in
719              spec.  Note that `^', `=', and `~', below, must  appear  to  the
720              left of `#' when these forms are combined.
721
722              If the option POSIX_IDENTIFIERS is not set, and spec is a simple
723              name, then the braces are optional; this is true even  for  spe‐
724              cial  parameters  so  e.g.  $#-  and  $#* take the length of the
725              string $- and the array $* respectively.   If  POSIX_IDENTIFIERS
726              is set, then braces are required for the # to be treated in this
727              fashion.
728
729       ${^spec}
730              Turn on the RC_EXPAND_PARAM option for the evaluation  of  spec;
731              if  the  `^'  is doubled, turn it off.  When this option is set,
732              array expansions of the form foo${xx}bar, where the parameter xx
733              is  set  to  (a  b  c),  are  substituted  with `fooabar foobbar
734              foocbar' instead of the default `fooa b  cbar'.   Note  that  an
735              empty array will therefore cause all arguments to be removed.
736
737              Internally, each such expansion is converted into the equivalent
738              list   for   brace    expansion.     E.g.,    ${^var}    becomes
739              {$var[1],$var[2],...}, and is processed as described in the sec‐
740              tion `Brace Expansion' below: note, however, the expansion  hap‐
741              pens  immediately,  with  any explicit brace expansion happening
742              later.  If word splitting is also  in  effect  the  $var[N]  may
743              themselves be split into different list elements.
744
745       ${=spec}
746              Perform  word splitting using the rules for SH_WORD_SPLIT during
747              the evaluation of spec, but regardless of whether the  parameter
748              appears  in  double  quotes; if the `=' is doubled, turn it off.
749              This forces parameter expansions to be split into separate words
750              before  substitution, using IFS as a delimiter.  This is done by
751              default in most other shells.
752
753              Note that splitting is applied to word in the  assignment  forms
754              of  spec  before  the  assignment  to  name  is performed.  This
755              affects the result of array assignments with the A flag.
756
757       ${~spec}
758              Turn on the GLOB_SUBST option for the evaluation of spec; if the
759              `~'  is  doubled,  turn  it  off.   When this option is set, the
760              string resulting from the expansion will  be  interpreted  as  a
761              pattern anywhere that is possible, such as in filename expansion
762              and filename generation and pattern-matching contexts  like  the
763              right hand side of the `=' and `!=' operators in conditions.
764
765              In  nested  substitutions, note that the effect of the ~ applies
766              to the result of the current level of substitution.  A surround‐
767              ing  pattern  operation on the result may cancel it.  Hence, for
768              example, if the parameter foo is set to  *,  ${~foo//\*/*.c}  is
769              substituted  by  the pattern *.c, which may be expanded by file‐
770              name  generation,  but  ${${~foo}//\*/*.c}  substitutes  to  the
771              string *.c, which will not be further expanded.
772
773       If  a ${...} type parameter expression or a $(...) type command substi‐
774       tution is used in place of name above, it is  expanded  first  and  the
775       result is used as if it were the value of name.  Thus it is possible to
776       perform nested operations:  ${${foo#head}%tail} substitutes  the  value
777       of  $foo  with both `head' and `tail' deleted.  The form with $(...) is
778       often useful in combination with the  flags  described  next;  see  the
779       examples  below.   Each  name or nested ${...} in a parameter expansion
780       may also be followed by a subscript expression as  described  in  Array
781       Parameters in zshparam(1).
782
783       Note  that double quotes may appear around nested expressions, in which
784       case  only  the  part  inside  is  treated  as  quoted;  for   example,
785       ${(f)"$(foo)"}  quotes  the  result  of $(foo), but the flag `(f)' (see
786       below) is applied using the rules for unquoted expansions.   Note  fur‐
787       ther that quotes are themselves nested in this context; for example, in
788       "${(@f)"$(foo)"}", there are two sets of quotes,  one  surrounding  the
789       whole  expression,  the  other  (redundant)  surrounding  the $(foo) as
790       before.
791
792   Parameter Expansion Flags
793       If the opening brace is directly followed by  an  opening  parenthesis,
794       the  string  up  to the matching closing parenthesis will be taken as a
795       list of flags.  In cases where repeating a flag is meaningful, the rep‐
796       etitions need not be consecutive; for example, `(q%q%q)' means the same
797       thing as the more readable `(%%qqq)'.  The  following  flags  are  sup‐
798       ported:
799
800       #      Evaluate  the  resulting words as numeric expressions and output
801              the characters corresponding to  the  resulting  integer.   Note
802              that  this  form  is entirely distinct from use of the # without
803              parentheses.
804
805              If the MULTIBYTE option is set and the number  is  greater  than
806              127  (i.e.  not  an  ASCII character) it is treated as a Unicode
807              character.
808
809       %      Expand all % escapes in the resulting words in the same  way  as
810              in prompts (see EXPANSION OF PROMPT SEQUENCES in zshmisc(1)). If
811              this flag is given twice, full prompt expansion is done  on  the
812              resulting words, depending on the setting of the PROMPT_PERCENT,
813              PROMPT_SUBST and PROMPT_BANG options.
814
815       @      In double quotes, array elements are put  into  separate  words.
816              E.g.,   `"${(@)foo}"'   is   equivalent   to  `"${foo[@]}"'  and
817              `"${(@)foo[1,2]}"' is the same as `"$foo[1]"  "$foo[2]"'.   This
818              is  distinct  from field splitting by the f, s or z flags, which
819              still applies within each array element.
820
821       A      Convert the substitution into an array expression,  even  if  it
822              otherwise  would be scalar.  This has lower precedence than sub‐
823              scripting, so one level of nested expansion is required in order
824              that  subscripts apply to array elements.  Thus ${${(A)name}[1]}
825              yields the full value of name when name is scalar.
826
827              This assigns an array parameter with `${...=...}', `${...:=...}'
828              or  `${...::=...}'.   If  this  flag  is  repeated (as in `AA'),
829              assigns an associative  array  parameter.   Assignment  is  made
830              before  sorting  or  padding;  if field splitting is active, the
831              word part is split before assignment.  The name part  may  be  a
832              subscripted  range  for ordinary arrays; when assigning an asso‐
833              ciative array, the word part must be converted to an array,  for
834              example by using `${(AA)=name=...}' to activate field splitting.
835
836              Surrounding  context  such  as  additional nesting or use of the
837              value in a scalar assignment may cause the array  to  be  joined
838              back into a single string again.
839
840       a      Sort  in  array  index  order;  when  combined  with `O' sort in
841              reverse array index order.  Note that `a' is  therefore  equiva‐
842              lent  to the default but `Oa' is useful for obtaining an array's
843              elements in reverse order.
844
845       b      Quote with backslashes only characters that are special to  pat‐
846              tern  matching. This is useful when the contents of the variable
847              are to be tested using GLOB_SUBST, including the ${~...} switch.
848
849              Quoting using one of the q family of flags  does  not  work  for
850              this  purpose  since  quotes  are  not stripped from non-pattern
851              characters by GLOB_SUBST.  In other words,
852
853                     pattern=${(q)str}
854                     [[ $str = ${~pattern} ]]
855
856              works if $str is `a*b' but not if it is `a b', whereas
857
858                     pattern=${(b)str}
859                     [[ $str = ${~pattern} ]]
860
861              is always true for any possible value of $str.
862
863       c      With ${#name}, count the total number of characters in an array,
864              as  if  the elements were concatenated with spaces between them.
865              This is not a true join of the array, so other expressions  used
866              with  this  flag may have an effect on the elements of the array
867              before it is counted.
868
869       C      Capitalize the resulting words.  `Words' in this case refers  to
870              sequences  of  alphanumeric characters separated by non-alphanu‐
871              merics, not to words that result from field splitting.
872
873       D      Assume the string or  array  elements  contain  directories  and
874              attempt  to  substitute the leading part of these by names.  The
875              remainder of the path (the whole of it if the leading  part  was
876              not  substituted) is then quoted so that the whole string can be
877              used as a shell argument.  This is the reverse of `~'  substitu‐
878              tion:  see the section FILENAME EXPANSION below.
879
880       e      Perform  single  word  shell expansions, namely parameter expan‐
881              sion, command substitution  and  arithmetic  expansion,  on  the
882              result. Such expansions can be nested but too deep recursion may
883              have unpredictable effects.
884
885       f      Split the result of the expansion at newlines. This is a  short‐
886              hand for `ps:\n:'.
887
888       F      Join  the words of arrays together using newline as a separator.
889              This is a shorthand for `pj:\n:'.
890
891       g:opts:
892              Process escape sequences like the echo builtin when  no  options
893              are  given (g::).  With the o option, octal escapes don't take a
894              leading zero.  With the c option, sequences like `^X'  are  also
895              processed.   With  the  e  option,  processes `\M-t' and similar
896              sequences like the print builtin.  With both  of  the  o  and  e
897              options,  behaves  like the print builtin except that in none of
898              these modes is `\c' interpreted.
899
900       i      Sort case-insensitively.  May be combined with `n' or `O'.
901
902       k      If name refers to an  associative  array,  substitute  the  keys
903              (element  names)  rather  than the values of the elements.  Used
904              with subscripts (including ordinary arrays),  force  indices  or
905              keys to be substituted even if the subscript form refers to val‐
906              ues.  However, this flag may  not  be  combined  with  subscript
907              ranges.   With  the KSH_ARRAYS option a subscript `[*]' or `[@]'
908              is needed to operate on the whole array, as usual.
909
910       L      Convert all letters in the result to lower case.
911
912       n      Sort decimal integers numerically; if the first differing  char‐
913              acters  of  two test strings are not digits, sorting is lexical.
914              Integers with more initial zeroes are sorted before  those  with
915              fewer  or  none.   Hence  the  array `foo1 foo02 foo2 foo3 foo20
916              foo23' is sorted into the order shown.  May be combined with `i'
917              or `O'.
918
919       o      Sort  the resulting words in ascending order; if this appears on
920              its own the sorting is lexical and  case-sensitive  (unless  the
921              locale renders it case-insensitive).  Sorting in ascending order
922              is the default for other forms of sorting, so this is ignored if
923              combined with `a', `i' or `n'.
924
925       O      Sort  the  resulting words in descending order; `O' without `a',
926              `i' or `n' sorts in reverse lexical order.  May be combined with
927              `a', `i' or `n' to reverse the order of sorting.
928
929       P      This forces the value of the parameter name to be interpreted as
930              a further parameter name, whose value will be used where  appro‐
931              priate.   Note  that flags set with one of the typeset family of
932              commands (in particular case transformations) are not applied to
933              the value of name used in this fashion.
934
935              If  used  with  a  nested parameter or command substitution, the
936              result of that will be taken as a parameter  name  in  the  same
937              way.   For  example,  if  you  have `foo=bar' and `bar=baz', the
938              strings ${(P)foo}, ${(P)${foo}}, and ${(P)$(echo bar)}  will  be
939              expanded to `baz'.
940
941              Likewise, if the reference is itself nested, the expression with
942              the flag is treated as if  it  were  directly  replaced  by  the
943              parameter name.  It is an error if this nested substitution pro‐
944              duces an array  with  more  than  one  word.   For  example,  if
945              `name=assoc'  where the parameter assoc is an associative array,
946              then `${${(P)name}[elt]}' refers to the element of the  associa‐
947              tive subscripted `elt'.
948
949       q      Quote  characters that are special to the shell in the resulting
950              words with backslashes; unprintable or  invalid  characters  are
951              quoted  using  the  $'\NNN'  form, with separate quotes for each
952              octet.
953
954              If this flag is given twice, the resulting words are  quoted  in
955              single  quotes  and  if  it  is given three times, the words are
956              quoted in double quotes; in these forms no special  handling  of
957              unprintable  or invalid characters is attempted.  If the flag is
958              given four times, the words are quoted in single quotes preceded
959              by  a  $.  Note that in all three of these forms quoting is done
960              unconditionally, even if  this  does  not  change  the  way  the
961              resulting string would be interpreted by the shell.
962
963              If a q- is given (only a single q may appear), a minimal form of
964              single quoting is used that only quotes the string if needed  to
965              protect  special characters.  Typically this form gives the most
966              readable output.
967
968              If a q+ is given, an extended form of  minmal  quoting  is  used
969              that  causes unprintable characters to be rendered using $'...'.
970              This quoting is similar to that used by the output of values  by
971              the typeset family of commands.
972
973       Q      Remove one level of quotes from the resulting words.
974
975       t      Use  a  string  describing  the  type of the parameter where the
976              value of the parameter would usually appear.  This  string  con‐
977              sists  of keywords separated by hyphens (`-'). The first keyword
978              in the string  describes  the  main  type,  it  can  be  one  of
979              `scalar',  `array',  `integer',  `float'  or  `association'. The
980              other keywords describe the type in more detail:
981
982              local  for local parameters
983
984              left   for left justified parameters
985
986              right_blanks
987                     for right justified parameters with leading blanks
988
989              right_zeros
990                     for right justified parameters with leading zeros
991
992              lower  for parameters whose value is converted to all lower case
993                     when it is expanded
994
995              upper  for parameters whose value is converted to all upper case
996                     when it is expanded
997
998              readonly
999                     for readonly parameters
1000
1001              tag    for tagged parameters
1002
1003              export for exported parameters
1004
1005              unique for arrays which keep only the first occurrence of dupli‐
1006                     cated values
1007
1008              hide   for parameters with the `hide' flag
1009
1010              hideval
1011                     for parameters with the `hideval' flag
1012
1013              special
1014                     for special parameters defined by the shell
1015
1016       u      Expand only the first occurrence of each unique word.
1017
1018       U      Convert all letters in the result to upper case.
1019
1020       v      Used  with k, substitute (as two consecutive words) both the key
1021              and the value of each associative array element.  Used with sub‐
1022              scripts,  force  values  to be substituted even if the subscript
1023              form refers to indices or keys.
1024
1025       V      Make any special characters in the resulting words visible.
1026
1027       w      With ${#name}, count words in arrays or strings; the s flag  may
1028              be used to set a word delimiter.
1029
1030       W      Similar  to  w  with  the  difference  that  empty words between
1031              repeated delimiters are also counted.
1032
1033       X      With this flag, parsing errors occurring with the  Q,  e  and  #
1034              flags  or  the  pattern matching forms such as `${name#pattern}'
1035              are reported.  Without the flag, errors are silently ignored.
1036
1037       z      Split the result of the expansion into words using shell parsing
1038              to  find  the words, i.e. taking into account any quoting in the
1039              value.  Comments are  not  treated  specially  but  as  ordinary
1040              strings, similar to interactive shells with the INTERACTIVE_COM‐
1041              MENTS option unset (however, see the Z flag  below  for  related
1042              options)
1043
1044              Note  that  this  is  done  very late, even later than the `(s)'
1045              flag. So to access single words in the result use nested  expan‐
1046              sions as in `${${(z)foo}[2]}'. Likewise, to remove the quotes in
1047              the resulting words use `${(Q)${(z)foo}}'.
1048
1049       0      Split the result of the expansion on  null  bytes.   This  is  a
1050              shorthand for `ps:\0:'.
1051
1052       The following flags (except p) are followed by one or more arguments as
1053       shown.  Any character, or the matching pairs `(...)', `{...}', `[...]',
1054       or  `<...>',  may  be  used in place of a colon as delimiters, but note
1055       that when a flag takes more than one argument, a matched pair of delim‐
1056       iters must surround each argument.
1057
1058       p      Recognize  the  same  escape  sequences  as the print builtin in
1059              string arguments to any of the flags described below that follow
1060              this argument.
1061
1062              Alternatively,  with  this option string arguments may be in the
1063              form $var in which case the value of  the  variable  is  substi‐
1064              tuted.   Note  this form is strict; the string argument does not
1065              undergo general parameter expansion.
1066
1067              For example,
1068
1069                     sep=:
1070                     val=a:b:c
1071                     print ${(ps.$sep.)val}
1072
1073              splits the variable on a :.
1074
1075       ~      Strings inserted into the expansion by any of  the  flags  below
1076              are to be treated as patterns.  This applies to the string argu‐
1077              ments of flags that follow ~ within the same set of parentheses.
1078              Compare with ~ outside parentheses, which forces the entire sub‐
1079              stituted string to be treated as a pattern.  Hence, for example,
1080
1081                     [[ "?" = ${(~j.|.)array} ]]
1082
1083              treats `|' as a pattern and succeeds if and only if $array  con‐
1084              tains  the  string  `?' as an element.  The ~ may be repeated to
1085              toggle the behaviour; its effect only lasts to the  end  of  the
1086              parenthesised group.
1087
1088       j:string:
1089              Join  the  words of arrays together using string as a separator.
1090              Note that this occurs before field splitting  by  the  s:string:
1091              flag or the SH_WORD_SPLIT option.
1092
1093       l:expr::string1::string2:
1094              Pad  the  resulting  words on the left.  Each word will be trun‐
1095              cated if required and placed in a field expr characters wide.
1096
1097              The arguments :string1: and :string2: are optional; neither, the
1098              first, or both may be given.  Note that the same pairs of delim‐
1099              iters must be used for each of the three arguments.   The  space
1100              to  the  left will be filled with string1 (concatenated as often
1101              as needed) or spaces if string1 is not given.  If  both  string1
1102              and  string2 are given, string2 is inserted once directly to the
1103              left of each word, truncated if  necessary,  before  string1  is
1104              used to produce any remaining padding.
1105
1106              If either of string1 or string2 is present but empty, i.e. there
1107              are two delimiters together at that point, the  first  character
1108              of $IFS is used instead.
1109
1110              If  the  MULTIBYTE  option  is in effect, the flag m may also be
1111              given, in which case widths will be used for the calculation  of
1112              padding;  otherwise  individual multibyte characters are treated
1113              as occupying one unit of width.
1114
1115              If the MULTIBYTE option is not  in  effect,  each  byte  in  the
1116              string is treated as occupying one unit of width.
1117
1118              Control  characters are always assumed to be one unit wide; this
1119              allows the mechanism to be used for  generating  repetitions  of
1120              control characters.
1121
1122       m      Only  useful together with one of the flags l or r or with the #
1123              length operator when the MULTIBYTE option is in effect.  Use the
1124              character  width  reported by the system in calculating how much
1125              of the string it occupies or the overall length of  the  string.
1126              Most printable characters have a width of one unit, however cer‐
1127              tain Asian character sets and certain special effects use  wider
1128              characters; combining characters have zero width.  Non-printable
1129              characters are arbitrarily counted as zero width; how they would
1130              actually be displayed will vary.
1131
1132              If  the  m  is repeated, the character either counts zero (if it
1133              has zero width), else one.  For printable character strings this
1134              has  the  effect of counting the number of glyphs (visibly sepa‐
1135              rate characters), except for the case where combining characters
1136              themselves have non-zero width (true in certain alphabets).
1137
1138       r:expr::string1::string2:
1139              As  l, but pad the words on the right and insert string2 immedi‐
1140              ately to the right of the string to be padded.
1141
1142              Left and right padding may be used together.  In this  case  the
1143              strategy  is  to  apply  left padding to the first half width of
1144              each of the resulting words, and right  padding  to  the  second
1145              half.   If  the string to be padded has odd width the extra pad‐
1146              ding is applied on the left.
1147
1148       s:string:
1149              Force field splitting at the  separator  string.   Note  that  a
1150              string  of  two  or  more characters means that all of them must
1151              match in sequence; this differs from the  treatment  of  two  or
1152              more  characters  in the IFS parameter.  See also the = flag and
1153              the SH_WORD_SPLIT option.  An empty string may also be given  in
1154              which case every character will be a separate element.
1155
1156              For  historical  reasons,  the  usual behaviour that empty array
1157              elements are retained  inside  double  quotes  is  disabled  for
1158              arrays generated by splitting; hence the following:
1159
1160                     line="one::three"
1161                     print -l "${(s.:.)line}"
1162
1163              produces  two  lines  of output for one and three and elides the
1164              empty field.  To override this behaviour, supply the `(@)'  flag
1165              as well, i.e.  "${(@s.:.)line}".
1166
1167       Z:opts:
1168              As z but takes a combination of option letters between a follow‐
1169              ing pair of delimiter characters.  With no options the effect is
1170              identical to z.  (Z+c+) causes comments to be parsed as a string
1171              and retained; any field in the resulting array beginning with an
1172              unquoted comment character is a comment.  (Z+C+) causes comments
1173              to be parsed and removed.  The rule for  comments  is  standard:
1174              anything  between  a  word  starting with the third character of
1175              $HISTCHARS, default #, up to the  next  newline  is  a  comment.
1176              (Z+n+) causes unquoted newlines to be treated as ordinary white‐
1177              space, else they are treated as if they are  shell  code  delim‐
1178              iters  and converted to semicolons.  Options are combined within
1179              the same set of delimiters, e.g. (Z+Cn+).
1180
1181       _:flags:
1182              The underscore (_) flag is reserved for future use.  As of  this
1183              revision of zsh, there are no valid flags; anything following an
1184              underscore, other than an empty pair of delimiters,  is  treated
1185              as an error, and the flag itself has no effect.
1186
1187       The  following  flags  are meaningful with the ${...#...} or ${...%...}
1188       forms.  The S and I flags may also be used with the ${.../...} forms.
1189
1190       S      Search substrings as well as beginnings or ends;  with  #  start
1191              from  the beginning and with % start from the end of the string.
1192              With  substitution  via  ${.../...}  or  ${...//...},  specifies
1193              non-greedy matching, i.e. that the shortest instead of the long‐
1194              est match should be replaced.
1195
1196       I:expr:
1197              Search the exprth match (where  expr  evaluates  to  a  number).
1198              This only applies when searching for substrings, either with the
1199              S flag, or with ${.../...} (only the  exprth  match  is  substi‐
1200              tuted)  or  ${...//...} (all matches from the exprth on are sub‐
1201              stituted).  The default is to take the first match.
1202
1203              The exprth match is counted such that there  is  either  one  or
1204              zero matches from each starting position in the string, although
1205              for global substitution matches  overlapping  previous  replace‐
1206              ments  are  ignored.  With the ${...%...} and ${...%%...} forms,
1207              the starting position for the match moves backwards from the end
1208              as the index increases, while with the other forms it moves for‐
1209              ward from the start.
1210
1211              Hence with the string
1212                     which switch is the right switch for Ipswich?
1213              substitutions of the form ${(SI:N:)string#w*ch} as  N  increases
1214              from  1  will  match  and  remove  `which', `witch', `witch' and
1215              `wich'; the form using `##' will match and remove `which  switch
1216              is the right switch for Ipswich', `witch is the right switch for
1217              Ipswich', `witch for Ipswich' and `wich'.  The  form  using  `%'
1218              will  remove  the same matches as for `#', but in reverse order,
1219              and the form using `%%' will remove the same matches as for `##'
1220              in reverse order.
1221
1222       B      Include the index of the beginning of the match in the result.
1223
1224       E      Include the index one character past the end of the match in the
1225              result (note this is inconsistent with other uses  of  parameter
1226              index).
1227
1228       M      Include the matched portion in the result.
1229
1230       N      Include the length of the match in the result.
1231
1232       R      Include the unmatched portion in the result (the Rest).
1233
1234   Rules
1235       Here  is  a  summary  of  the rules for substitution; this assumes that
1236       braces are present around the substitution, i.e. ${...}.  Some particu‐
1237       lar  examples  are  given  below.   Note that the Zsh Development Group
1238       accepts no responsibility for any brain damage which may  occur  during
1239       the reading of the following rules.
1240
1241       1. Nested substitution
1242              If  multiple  nested  ${...}  forms are present, substitution is
1243              performed from the inside outwards.  At each level, the  substi‐
1244              tution takes account of whether the current value is a scalar or
1245              an array, whether the whole substitution is  in  double  quotes,
1246              and  what  flags  are supplied to the current level of substitu‐
1247              tion, just as if the nested  substitution  were  the  outermost.
1248              The  flags are not propagated up to enclosing substitutions; the
1249              nested substitution will return either a scalar or an  array  as
1250              determined by the flags, possibly adjusted for quoting.  All the
1251              following steps take place where applicable  at  all  levels  of
1252              substitution.
1253
1254              Note  that,  unless the `(P)' flag is present, the flags and any
1255              subscripts apply directly to the value of the  nested  substitu‐
1256              tion;  for  example, the expansion ${${foo}} behaves exactly the
1257              same as ${foo}.  When the `(P)' flag is present in a nested sub‐
1258              stitution, the other substitution rules are applied to the value
1259              before it is interpreted as a name, so ${${(P)foo}}  may  differ
1260              from ${(P)foo}.
1261
1262              At  each  nested  level  of  substitution, the substituted words
1263              undergo all forms of single-word substitution (i.e. not filename
1264              generation),  including  command substitution, arithmetic expan‐
1265              sion and filename expansion (i.e. leading ~ and =).   Thus,  for
1266              example,  ${${:-=cat}:h}  expands to the directory where the cat
1267              program resides.  (Explanation: the internal substitution has no
1268              parameter  but  a default value =cat, which is expanded by file‐
1269              name expansion to a  full  path;  the  outer  substitution  then
1270              applies  the  modifier  :h  and  takes the directory part of the
1271              path.)
1272
1273       2. Internal parameter flags
1274              Any parameter flags set by one of the  typeset  family  of  com‐
1275              mands,  in particular the -L, -R, -Z, -u and -l options for pad‐
1276              ding and capitalization, are applied directly to  the  parameter
1277              value.  Note these flags are options to the command, e.g. `type‐
1278              set -Z'; they are not the same as the flags used within  parame‐
1279              ter substitutions.
1280
1281              At the outermost level of substitution, the `(P)' flag (rule 4.)
1282              ignores these transformations and uses the unmodified  value  of
1283              the  parameter  as the name to be replaced.  This is usually the
1284              desired behavior because padding may make  the  value  syntacti‐
1285              cally illegal as a parameter name, but if capitalization changes
1286              are desired, use the ${${(P)foo}} form (rule 25.).
1287
1288       3. Parameter subscripting
1289              If the value is a raw parameter reference with a subscript, such
1290              as  ${var[3]}, the effect of subscripting is applied directly to
1291              the parameter.  Subscripts are evaluated left to  right;  subse‐
1292              quent  subscripts  apply to the scalar or array value yielded by
1293              the previous subscript.  Thus if var is an  array,  ${var[1][2]}
1294              is the second character of the first word, but ${var[2,4][2]} is
1295              the entire third word (the second word of the range of words two
1296              through  four  of the original array).  Any number of subscripts
1297              may appear.  Flags such as  `(k)'  and  `(v)'  which  alter  the
1298              result of subscripting are applied.
1299
1300       4. Parameter name replacement
1301              At  the  outermost  level  of  nesting  only,  the `(P)' flag is
1302              applied.  This treats the value  so  far  as  a  parameter  name
1303              (which  may  include  a  subscript expression) and replaces that
1304              with the corresponding value.  This replacement occurs later  if
1305              the `(P)' flag appears in a nested substitution.
1306
1307              If  the  value  so far names a parameter that has internal flags
1308              (rule 2.), those internal flags are applied  to  the  new  value
1309              after replacement.
1310
1311       5. Double-quoted joining
1312              If  the  value after this process is an array, and the substitu‐
1313              tion appears in double quotes, and neither an `(@)' flag  nor  a
1314              `#'  length operator is present at the current level, then words
1315              of the value are joined with the first character of the  parame‐
1316              ter  $IFS,  by  default  a space, between each word (single word
1317              arrays are not modified).  If the `(j)' flag is present, that is
1318              used for joining instead of $IFS.
1319
1320       6. Nested subscripting
1321              Any  remaining  subscripts  (i.e.  of a nested substitution) are
1322              evaluated at this point, based on whether the value is an  array
1323              or  a scalar.  As with 3., multiple subscripts can appear.  Note
1324              that ${foo[2,4][2]} is thus equivalent to ${${foo[2,4]}[2]}  and
1325              also  to "${${(@)foo[2,4]}[2]}" (the nested substitution returns
1326              an array in both cases), but  not  to  "${${foo[2,4]}[2]}"  (the
1327              nested substitution returns a scalar because of the quotes).
1328
1329       7. Modifiers
1330              Any  modifiers, as specified by a trailing `#', `%', `/' (possi‐
1331              bly doubled) or by a set of modifiers of the  form  `:...'  (see
1332              the section `Modifiers' in the section `History Expansion'), are
1333              applied to the words of the value at this level.
1334
1335       8. Character evaluation
1336              Any `(#)' flag is applied, evaluating the result so far  numeri‐
1337              cally as a character.
1338
1339       9. Length
1340              Any  initial  `#' modifier, i.e. in the form ${#var}, is used to
1341              evaluate the length of the expression so far.
1342
1343       10. Forced joining
1344              If the `(j)' flag is present, or no `(j)' flag  is  present  but
1345              the  string is to be split as given by rule 11., and joining did
1346              not take place at rule 5., any words in  the  value  are  joined
1347              together  using  the given string or the first character of $IFS
1348              if none.  Note that the `(F)' flag implicitly supplies a  string
1349              for joining in this manner.
1350
1351       11. Simple word splitting
1352              If one of the `(s)' or `(f)' flags are present, or the `=' spec‐
1353              ifier was present (e.g. ${=var}), the word is  split  on  occur‐
1354              rences  of  the  specified string, or (for = with neither of the
1355              two flags present) any of the characters in $IFS.
1356
1357              If no `(s)', `(f)' or `=' was given, but the word is not  quoted
1358              and the option SH_WORD_SPLIT is set, the word is split on occur‐
1359              rences of any of the characters in $IFS.  Note this  step,  too,
1360              takes place at all levels of a nested substitution.
1361
1362       12. Case modification
1363              Any  case  modification  from  one  of the flags `(L)', `(U)' or
1364              `(C)' is applied.
1365
1366       13. Escape sequence replacement
1367              First any replacements from the `(g)' flag are  performed,  then
1368              any  prompt-style  formatting  from the `(%)' family of flags is
1369              applied.
1370
1371       14. Quote application
1372              Any quoting or unquoting using `(q)' and `(Q)' and related flags
1373              is applied.
1374
1375       15. Directory naming
1376              Any directory name substitution using `(D)' flag is applied.
1377
1378       16. Visibility enhancement
1379              Any  modifications  to  make  characters visible using the `(V)'
1380              flag are applied.
1381
1382       17. Lexical word splitting
1383              If the '(z)' flag or one of the  forms  of  the  '(Z)'  flag  is
1384              present,  the  word is split as if it were a shell command line,
1385              so that quotation marks and other  metacharacters  are  used  to
1386              decide  what constitutes a word.  Note this form of splitting is
1387              entirely distinct from that described by rule 11.: it  does  not
1388              use $IFS, and does not cause forced joining.
1389
1390       18. Uniqueness
1391              If the result is an array and the `(u)' flag was present, dupli‐
1392              cate elements are removed from the array.
1393
1394       19. Ordering
1395              If the result is still an array and one of the  `(o)'  or  `(O)'
1396              flags was present, the array is reordered.
1397
1398       20. RC_EXPAND_PARAM
1399              At  this  point the decision is made whether any resulting array
1400              elements are to be combined element by element with  surrounding
1401              text,  as  given by either the RC_EXPAND_PARAM option or the `^'
1402              flag.
1403
1404       21. Re-evaluation
1405              Any `(e)' flag is  applied  to  the  value,  forcing  it  to  be
1406              re-examined  for  new parameter substitutions, but also for com‐
1407              mand and arithmetic substitutions.
1408
1409       22. Padding
1410              Any padding of the value by the `(l.fill.)' or `(r.fill.)' flags
1411              is applied.
1412
1413       23. Semantic joining
1414              In  contexts where expansion semantics requires a single word to
1415              result, all words are rejoined with the first character  of  IFS
1416              between.   So  in  `${(P)${(f)lines}}'  the value of ${lines} is
1417              split at newlines, but then must  be  joined  again  before  the
1418              `(P)' flag can be applied.
1419
1420              If a single word is not required, this rule is skipped.
1421
1422       24. Empty argument removal
1423              If  the  substitution  does  not  appear  in  double quotes, any
1424              resulting zero-length argument, whether from a scalar or an ele‐
1425              ment  of an array, is elided from the list of arguments inserted
1426              into the command line.
1427
1428              Strictly speaking, the removal happens later as the same happens
1429              with other forms of substitution; the point to note here is sim‐
1430              ply that it occurs after any of the above parameter operations.
1431
1432       25. Nested parameter name replacement
1433              If the `(P)' flag is present and rule 4. has  not  applied,  the
1434              value so far is treated as a parameter name (which may include a
1435              subscript expression) and replaced with the corresponding value,
1436              with internal flags (rule 2.) applied to the new value.
1437
1438   Examples
1439       The  flag  f  is  useful  to split a double-quoted substitution line by
1440       line.  For example, ${(f)"$(<file)"} substitutes the contents  of  file
1441       divided  so  that each line is an element of the resulting array.  Com‐
1442       pare this with the effect of $(<file) alone, which divides the file  up
1443       by words, or the same inside double quotes, which makes the entire con‐
1444       tent of the file a single string.
1445
1446       The following illustrates the rules for  nested  parameter  expansions.
1447       Suppose that $foo contains the array (bar baz):
1448
1449       "${(@)${foo}[1]}"
1450              This  produces  the  result  b.   First,  the inner substitution
1451              "${foo}", which has no array (@) flag, produces  a  single  word
1452              result "bar baz".  The outer substitution "${(@)...[1]}" detects
1453              that this is a scalar, so that (despite the `(@)' flag) the sub‐
1454              script picks the first character.
1455
1456       "${${(@)foo}[1]}"
1457              This produces the result `bar'.  In this case, the inner substi‐
1458              tution "${(@)foo}" produces the array `(bar  baz)'.   The  outer
1459              substitution "${...[1]}" detects that this is an array and picks
1460              the first word.  This is similar to the simple case "${foo[1]}".
1461
1462       As an example of the rules for word splitting and joining, suppose $foo
1463       contains the array `(ax1 bx1)'.  Then
1464
1465       ${(s/x/)foo}
1466              produces the words `a', `1 b' and `1'.
1467
1468       ${(j/x/s/x/)foo}
1469              produces `a', `1', `b' and `1'.
1470
1471       ${(s/x/)foo%%1*}
1472              produces  `a'  and ` b' (note the extra space).  As substitution
1473              occurs before either joining or splitting, the operation   first
1474              generates  the  modified  array (ax bx), which is joined to give
1475              "ax bx", and then split to give `a', ` b'  and  `'.   The  final
1476              empty string will then be elided, as it is not in double quotes.
1477

COMMAND SUBSTITUTION

1479       A  command  enclosed  in  parentheses  preceded  by a dollar sign, like
1480       `$(...)', or quoted with grave accents, like ``...`', is replaced  with
1481       its  standard  output, with any trailing newlines deleted.  If the sub‐
1482       stitution is not enclosed in double quotes, the output is  broken  into
1483       words using the IFS parameter.
1484
1485       The  substitution `$(cat foo)' may be replaced by the faster `$(<foo)'.
1486       In this case foo undergoes  single  word  shell  expansions  (parameter
1487       expansion,  command  substitution  and  arithmetic  expansion), but not
1488       filename generation.
1489
1490       If the option GLOB_SUBST is set, the result  of  any  unquoted  command
1491       substitution,  including  the  special form just mentioned, is eligible
1492       for filename generation.
1493

ARITHMETIC EXPANSION

1495       A string of the form `$[exp]' or `$((exp))'  is  substituted  with  the
1496       value  of the arithmetic expression exp.  exp is subjected to parameter
1497       expansion, command substitution and arithmetic expansion before  it  is
1498       evaluated.  See the section `Arithmetic Evaluation'.
1499

BRACE EXPANSION

1501       A  string  of the form `foo{xx,yy,zz}bar' is expanded to the individual
1502       words `fooxxbar', `fooyybar' and `foozzbar'.   Left-to-right  order  is
1503       preserved.   This  construct  may  be  nested.  Commas may be quoted in
1504       order to include them literally in a word.
1505
1506       An expression of the form `{n1..n2}', where n1 and n2 are integers,  is
1507       expanded to every number between n1 and n2 inclusive.  If either number
1508       begins with a zero, all the resulting numbers will be padded with lead‐
1509       ing  zeroes to that minimum width, but for negative numbers the - char‐
1510       acter is also included in the width.  If the numbers are in  decreasing
1511       order the resulting sequence will also be in decreasing order.
1512
1513       An  expression  of  the  form  `{n1..n2..n3}', where n1, n2, and n3 are
1514       integers, is expanded as above, but only  every  n3th  number  starting
1515       from n1 is output.  If n3 is negative the numbers are output in reverse
1516       order, this is slightly different from simply swapping n1 and n2 in the
1517       case  that  the  step n3 doesn't evenly divide the range.  Zero padding
1518       can be specified in any of the three  numbers,  specifying  it  in  the
1519       third  can  be  useful to pad for example `{-99..100..01}' which is not
1520       possible to specify by putting a 0 on either of the first  two  numbers
1521       (i.e. pad to two characters).
1522
1523       An  expression of the form `{c1..c2}', where c1 and c2 are single char‐
1524       acters (which may be multibyte characters), is expanded to every  char‐
1525       acter in the range from c1 to c2 in whatever character sequence is used
1526       internally.  For characters with code points below 128 this is US ASCII
1527       (this is the only case most users will need).  If any intervening char‐
1528       acter is not printable, appropriate quotation  is  used  to  render  it
1529       printable.   If  the  character  sequence is reversed, the output is in
1530       reverse order, e.g. `{d..a}' is substituted as `d c b a'.
1531
1532       If a brace expression matches none of  the  above  forms,  it  is  left
1533       unchanged,  unless  the  option  BRACE_CCL  (an abbreviation for `brace
1534       character class') is set.  In that case, it is expanded to  a  list  of
1535       the  individual  characters between the braces sorted into the order of
1536       the characters in the ASCII character set (multibyte characters are not
1537       currently  handled).   The  syntax  is similar to a [...] expression in
1538       filename generation: `-' is treated specially  to  denote  a  range  of
1539       characters,  but `^' or `!' as the first character is treated normally.
1540       For example, `{abcdef0-9}' expands to 16 words 0 1 2 3 4 5 6 7 8 9 a  b
1541       c d e f.
1542
1543       Note  that  brace  expansion  is not part of filename generation (glob‐
1544       bing); an expression such as */{foo,bar} is  split  into  two  separate
1545       words  */foo and */bar before filename generation takes place.  In par‐
1546       ticular, note that this is liable to produce  a  `no  match'  error  if
1547       either  of the two expressions does not match; this is to be contrasted
1548       with */(foo|bar), which is treated as a single  pattern  but  otherwise
1549       has similar effects.
1550
1551       To  combine brace expansion with array expansion, see the ${^spec} form
1552       described in the section Parameter Expansion above.
1553

FILENAME EXPANSION

1555       Each word is checked to see if it begins with an unquoted `~'.   If  it
1556       does,  then the word up to a `/', or the end of the word if there is no
1557       `/', is checked to see if it can be substituted  in  one  of  the  ways
1558       described  here.   If  so,  then  the  `~'  and the checked portion are
1559       replaced with the appropriate substitute value.
1560
1561       A `~' by itself is replaced by the value of $HOME.  A `~' followed by a
1562       `+'  or  a  `-'  is  replaced by current or previous working directory,
1563       respectively.
1564
1565       A `~' followed by a number is replaced by the directory at  that  posi‐
1566       tion  in  the directory stack.  `~0' is equivalent to `~+', and `~1' is
1567       the top of the stack.  `~+' followed by a number  is  replaced  by  the
1568       directory at that position in the directory stack.  `~+0' is equivalent
1569       to `~+', and `~+1' is the top of the stack.  `~-' followed by a  number
1570       is replaced by the directory that many positions from the bottom of the
1571       stack.  `~-0' is the bottom  of  the  stack.   The  PUSHD_MINUS  option
1572       exchanges  the  effects  of  `~+' and `~-' where they are followed by a
1573       number.
1574
1575   Dynamic named directories
1576       If the  function  zsh_directory_name  exists,  or  the  shell  variable
1577       zsh_directory_name_functions  exists  and contains an array of function
1578       names, then the functions are used to implement dynamic directory  nam‐
1579       ing.   The  functions are tried in order until one returns status zero,
1580       so it is important that functions test whether they can handle the case
1581       in question and return an appropriate status.
1582
1583       A  `~'  followed  by  a  string  namstr  in unquoted square brackets is
1584       treated specially as a dynamic directory name.   Note  that  the  first
1585       unquoted  closing  square  bracket always terminates namstr.  The shell
1586       function is passed two arguments: the string n (for name)  and  namstr.
1587       It  should  either set the array reply to a single element which is the
1588       directory corresponding to the name and return status  zero  (executing
1589       an  assignment  as  the  last  statement  is usually sufficient), or it
1590       should return status non-zero.  In the former case the element of reply
1591       is used as the directory; in the latter case the substitution is deemed
1592       to have failed.  If all functions fail and the option NOMATCH  is  set,
1593       an error results.
1594
1595       The  functions defined as above are also used to see if a directory can
1596       be turned into a name, for example when printing the directory stack or
1597       when expanding %~ in prompts.  In this case each function is passed two
1598       arguments: the string d (for directory) and the candidate  for  dynamic
1599       naming.   The  function  should  either  return non-zero status, if the
1600       directory cannot be named by the function, or it should set  the  array
1601       reply to consist of two elements: the first is the dynamic name for the
1602       directory (as would appear within `~[...]'), and the second is the pre‐
1603       fix  length of the directory to be replaced.  For example, if the trial
1604       directory  is   /home/myname/src/zsh   and   the   dynamic   name   for
1605       /home/myname/src (which has 16 characters) is s, then the function sets
1606
1607              reply=(s 16)
1608
1609       The  directory  name so returned is compared with possible static names
1610       for parts of the directory path, as described below; it is used if  the
1611       prefix  length  matched (16 in the example) is longer than that matched
1612       by any static name.
1613
1614       It is not a requirement that a function implements both n and d  calls;
1615       for  example,  it  might  be  appropriate  for certain dynamic forms of
1616       expansion not to be contracted to names.  In that case  any  call  with
1617       the first argument d should cause a non-zero status to be returned.
1618
1619       The  completion system calls `zsh_directory_name c' followed by equiva‐
1620       lent calls to elements of the array zsh_directory_name_functions, if it
1621       exists,  in  order to complete dynamic names for directories.  The code
1622       for this should be as for any other completion function as described in
1623       zshcompsys(1).
1624
1625       As a working example, here is a function that expands any dynamic names
1626       beginning with the string p: to directories  below  /home/pws/perforce.
1627       In  this  simple  case a static name for the directory would be just as
1628       effective.
1629
1630              zsh_directory_name() {
1631                emulate -L zsh
1632                setopt extendedglob
1633                local -a match mbegin mend
1634                if [[ $1 = d ]]; then
1635                  # turn the directory into a name
1636                  if [[ $2 = (#b)(/home/pws/perforce/)([^/]##)* ]]; then
1637                    typeset -ga reply
1638                    reply=(p:$match[2] $(( ${#match[1]} + ${#match[2]} )) )
1639                  else
1640                    return 1
1641                  fi
1642                elif [[ $1 = n ]]; then
1643                  # turn the name into a directory
1644                  [[ $2 != (#b)p:(?*) ]] && return 1
1645                  typeset -ga reply
1646                  reply=(/home/pws/perforce/$match[1])
1647                elif [[ $1 = c ]]; then
1648                  # complete names
1649                  local expl
1650                  local -a dirs
1651                  dirs=(/home/pws/perforce/*(/:t))
1652                  dirs=(p:${^dirs})
1653                  _wanted dynamic-dirs expl 'dynamic directory' compadd -S\] -a dirs
1654                  return
1655                else
1656                  return 1
1657                fi
1658                return 0
1659              }
1660
1661   Static named directories
1662       A `~' followed by anything not already covered consisting of any number
1663       of  alphanumeric  characters  or underscore (`_'), hyphen (`-'), or dot
1664       (`.') is looked up as a named directory, and replaced by the  value  of
1665       that  named  directory  if found.  Named directories are typically home
1666       directories for users on the system.  They may also be defined  if  the
1667       text  after the `~' is the name of a string shell parameter whose value
1668       begins with a `/'.  Note that trailing slashes will be removed from the
1669       path to the directory (though the original parameter is not modified).
1670
1671       It  is  also  possible to define directory names using the -d option to
1672       the hash builtin.
1673
1674       When the shell prints a path (e.g. when expanding %~ in prompts or when
1675       printing  the  directory stack), the path is checked to see if it has a
1676       named directory as its prefix.  If  so,  then  the  prefix  portion  is
1677       replaced with a `~' followed by the name of the directory.  The shorter
1678       of the two ways of referring to the directory is used, i.e. either  the
1679       directory  name or the full path; the name is used if they are the same
1680       length.  The parameters $PWD and $OLDPWD are never abbreviated in  this
1681       fashion.
1682
1683   `=' expansion
1684       If a word begins with an unquoted `=' and the EQUALS option is set, the
1685       remainder of the word is taken as the name of a command.  If a  command
1686       exists  by  that name, the word is replaced by the full pathname of the
1687       command.
1688
1689   Notes
1690       Filename expansion is performed on the right hand side of  a  parameter
1691       assignment,  including  those  appearing  after commands of the typeset
1692       family.  In this case, the  right  hand  side  will  be  treated  as  a
1693       colon-separated list in the manner of the PATH parameter, so that a `~'
1694       or an `=' following a `:' is eligible for expansion.  All  such  behav‐
1695       iour  can be disabled by quoting the `~', the `=', or the whole expres‐
1696       sion (but not simply the colon); the EQUALS option is also respected.
1697
1698       If the option MAGIC_EQUAL_SUBST is set, any unquoted shell argument  in
1699       the form `identifier=expression' becomes eligible for file expansion as
1700       described in the  previous  paragraph.   Quoting  the  first  `='  also
1701       inhibits this.
1702

FILENAME GENERATION

1704       If  a  word contains an unquoted instance of one of the characters `*',
1705       `(', `|', `<', `[', or `?', it is regarded as a  pattern  for  filename
1706       generation,  unless  the  GLOB  option  is unset.  If the EXTENDED_GLOB
1707       option is set, the `^' and `#' characters also denote a pattern; other‐
1708       wise they are not treated specially by the shell.
1709
1710       The  word  is  replaced  with a list of sorted filenames that match the
1711       pattern.  If no matching pattern is found, the  shell  gives  an  error
1712       message,  unless the NULL_GLOB option is set, in which case the word is
1713       deleted; or unless the NOMATCH option is unset, in which case the  word
1714       is left unchanged.
1715
1716       In  filename  generation, the character `/' must be matched explicitly;
1717       also, a `.' must be matched explicitly at the beginning of a pattern or
1718       after  a  `/', unless the GLOB_DOTS option is set.  No filename genera‐
1719       tion pattern matches the files `.' or `..'.  In other instances of pat‐
1720       tern matching, the `/' and `.' are not treated specially.
1721
1722   Glob Operators
1723       *      Matches any string, including the null string.
1724
1725       ?      Matches any character.
1726
1727       [...]  Matches  any  of  the enclosed characters.  Ranges of characters
1728              can be specified by separating two characters by a `-'.   A  `-'
1729              or  `]' may be matched by including it as the first character in
1730              the list.  There are also several named classes  of  characters,
1731              in  the  form `[:name:]' with the following meanings.  The first
1732              set use the macros provided by the operating system to test  for
1733              the  given  character  combinations, including any modifications
1734              due to local language settings, see ctype(3):
1735
1736              [:alnum:]
1737                     The character is alphanumeric
1738
1739              [:alpha:]
1740                     The character is alphabetic
1741
1742              [:ascii:]
1743                     The character is 7-bit, i.e. is a  single-byte  character
1744                     without the top bit set.
1745
1746              [:blank:]
1747                     The character is a blank character
1748
1749              [:cntrl:]
1750                     The character is a control character
1751
1752              [:digit:]
1753                     The character is a decimal digit
1754
1755              [:graph:]
1756                     The  character is a printable character other than white‐
1757                     space
1758
1759              [:lower:]
1760                     The character is a lowercase letter
1761
1762              [:print:]
1763                     The character is printable
1764
1765              [:punct:]
1766                     The character is printable but neither  alphanumeric  nor
1767                     whitespace
1768
1769              [:space:]
1770                     The character is whitespace
1771
1772              [:upper:]
1773                     The character is an uppercase letter
1774
1775              [:xdigit:]
1776                     The character is a hexadecimal digit
1777
1778              Another  set of named classes is handled internally by the shell
1779              and is not sensitive to the locale:
1780
1781              [:IDENT:]
1782                     The character is allowed to form part of a shell  identi‐
1783                     fier, such as a parameter name
1784
1785              [:IFS:]
1786                     The  character  is used as an input field separator, i.e.
1787                     is contained in the IFS parameter
1788
1789              [:IFSSPACE:]
1790                     The character is an IFS white space  character;  see  the
1791                     documentation for IFS in the zshparam(1) manual page.
1792
1793              [:INCOMPLETE:]
1794                     Matches  a byte that starts an incomplete multibyte char‐
1795                     acter.  Note that there may be a sequence  of  more  than
1796                     one bytes that taken together form the prefix of a multi‐
1797                     byte character.  To test  for  a  potentially  incomplete
1798                     byte sequence, use the pattern `[[:INCOMPLETE:]]*'.  This
1799                     will never match a sequence starting with a valid  multi‐
1800                     byte character.
1801
1802              [:INVALID:]
1803                     Matches  a  byte  that  does  not start a valid multibyte
1804                     character.  Note this may be a continuation  byte  of  an
1805                     incomplete multibyte character as any part of a multibyte
1806                     string consisting of  invalid  and  incomplete  multibyte
1807                     characters is treated as single bytes.
1808
1809              [:WORD:]
1810                     The  character is treated as part of a word; this test is
1811                     sensitive to the value of the WORDCHARS parameter
1812
1813              Note that the square brackets are additional to those  enclosing
1814              the  whole  set  of characters, so to test for a single alphanu‐
1815              meric character you need `[[:alnum:]]'.   Named  character  sets
1816              can be used alongside other types, e.g. `[[:alpha:]0-9]'.
1817
1818       [^...]
1819       [!...] Like [...], except that it matches any character which is not in
1820              the given set.
1821
1822       <[x]-[y]>
1823              Matches any number in the range x to y,  inclusive.   Either  of
1824              the  numbers  may be omitted to make the range open-ended; hence
1825              `<->' matches any number.  To match individual digits, the [...]
1826              form is more efficient.
1827
1828              Be  careful  when  using other wildcards adjacent to patterns of
1829              this form; for example, <0-9>* will actually  match  any  number
1830              whatsoever  at  the  start of the string, since the `<0-9>' will
1831              match the first digit, and the `*' will match any others.   This
1832              is  a  trap  for the unwary, but is in fact an inevitable conse‐
1833              quence of the rule that the longest possible match  always  suc‐
1834              ceeds.   Expressions  such  as  `<0-9>[^[:digit:]]*' can be used
1835              instead.
1836
1837       (...)  Matches the enclosed pattern.  This is used  for  grouping.   If
1838              the  KSH_GLOB  option  is  set, then a `@', `*', `+', `?' or `!'
1839              immediately preceding the `(' is treated specially, as  detailed
1840              below.  The  option SH_GLOB prevents bare parentheses from being
1841              used in this way, though the KSH_GLOB option is still available.
1842
1843              Note that grouping cannot extend over multiple  directories:  it
1844              is  an error to have a `/' within a group (this only applies for
1845              patterns used in filename generation).  There is one  exception:
1846              a group of the form (pat/)# appearing as a complete path segment
1847              can match a sequence of directories.  For example, foo/(a*/)#bar
1848              matches foo/bar, foo/any/bar, foo/any/anyother/bar, and so on.
1849
1850       x|y    Matches  either x or y.  This operator has lower precedence than
1851              any other.  The `|' character must  be  within  parentheses,  to
1852              avoid  interpretation as a pipeline.  The alternatives are tried
1853              in order from left to right.
1854
1855       ^x     (Requires EXTENDED_GLOB to be set.)  Matches anything except the
1856              pattern x.  This has a higher precedence than `/', so `^foo/bar'
1857              will search directories in `.' except `./foo' for a  file  named
1858              `bar'.
1859
1860       x~y    (Requires EXTENDED_GLOB to be set.)  Match anything that matches
1861              the pattern x but does not match y.  This has  lower  precedence
1862              than  any  operator except `|', so `*/*~foo/bar' will search for
1863              all files in all directories in `.'  and then exclude  `foo/bar'
1864              if there was such a match.  Multiple patterns can be excluded by
1865              `foo~bar~baz'.  In the exclusion pattern (y), `/'  and  `.'  are
1866              not treated specially the way they usually are in globbing.
1867
1868       x#     (Requires EXTENDED_GLOB to be set.)  Matches zero or more occur‐
1869              rences of the pattern x.  This  operator  has  high  precedence;
1870              `12#'  is  equivalent to `1(2#)', rather than `(12)#'.  It is an
1871              error for an unquoted `#' to follow something  which  cannot  be
1872              repeated;  this includes an empty string, a pattern already fol‐
1873              lowed by `##', or parentheses when part of  a  KSH_GLOB  pattern
1874              (for  example,  `!(foo)#'  is  invalid  and  must be replaced by
1875              `*(!(foo))').
1876
1877       x##    (Requires EXTENDED_GLOB to be set.)  Matches one or more  occur‐
1878              rences  of  the  pattern  x.  This operator has high precedence;
1879              `12##' is equivalent to `1(2##)', rather than `(12)##'.  No more
1880              than  two  active `#' characters may appear together.  (Note the
1881              potential clash with glob qualifiers in the form `1(2##)'  which
1882              should therefore be avoided.)
1883
1884   ksh-like Glob Operators
1885       If  the KSH_GLOB option is set, the effects of parentheses can be modi‐
1886       fied by a preceding `@', `*', `+', `?' or `!'.  This character need not
1887       be unquoted to have special effects, but the `(' must be.
1888
1889       @(...) Match the pattern in the parentheses.  (Like `(...)'.)
1890
1891       *(...) Match  any  number  of occurrences.  (Like `(...)#', except that
1892              recursive directory searching is not supported.)
1893
1894       +(...) Match at least one occurrence.   (Like  `(...)##',  except  that
1895              recursive directory searching is not supported.)
1896
1897       ?(...) Match zero or one occurrence.  (Like `(|...)'.)
1898
1899       !(...) Match   anything  but  the  expression  in  parentheses.   (Like
1900              `(^(...))'.)
1901
1902   Precedence
1903       The precedence of the operators given above is (highest) `^', `/', `~',
1904       `|'  (lowest);  the remaining operators are simply treated from left to
1905       right as part of a string, with `#' and `##' applying to  the  shortest
1906       possible  preceding unit (i.e. a character, `?', `[...]', `<...>', or a
1907       parenthesised expression).  As mentioned above, a `/' used as a  direc‐
1908       tory  separator  may not appear inside parentheses, while a `|' must do
1909       so; in patterns used in other contexts than  filename  generation  (for
1910       example,  in  case statements and tests within `[[...]]'), a `/' is not
1911       special; and `/' is also not special  after  a  `~'  appearing  outside
1912       parentheses in a filename pattern.
1913
1914   Globbing Flags
1915       There  are various flags which affect any text to their right up to the
1916       end of the enclosing group or to the end of the pattern;  they  require
1917       the  EXTENDED_GLOB  option. All take the form (#X) where X may have one
1918       of the following forms:
1919
1920       i      Case insensitive:  upper or lower case characters in the pattern
1921              match upper or lower case characters.
1922
1923       l      Lower  case  characters in the pattern match upper or lower case
1924              characters; upper case characters  in  the  pattern  still  only
1925              match upper case characters.
1926
1927       I      Case  sensitive:  locally negates the effect of i or l from that
1928              point on.
1929
1930       b      Activate backreferences for parenthesised groups in the pattern;
1931              this  does not work in filename generation.  When a pattern with
1932              a set of active parentheses is matched, the strings  matched  by
1933              the  groups  are  stored in the array $match, the indices of the
1934              beginning of the matched parentheses in the array  $mbegin,  and
1935              the  indices  of the end in the array $mend, with the first ele‐
1936              ment of each array  corresponding  to  the  first  parenthesised
1937              group, and so on.  These arrays are not otherwise special to the
1938              shell.  The indices use the same convention  as  does  parameter
1939              substitution,  so that elements of $mend and $mbegin may be used
1940              in subscripts; the KSH_ARRAYS  option  is  respected.   Sets  of
1941              globbing flags are not considered parenthesised groups; only the
1942              first nine active parentheses can be referenced.
1943
1944              For example,
1945
1946                     foo="a string with a message"
1947                     if [[ $foo = (a|an)' '(#b)(*)' '* ]]; then
1948                       print ${foo[$mbegin[1],$mend[1]]}
1949                     fi
1950
1951              prints `string with a'.  Note  that  the  first  parenthesis  is
1952              before the (#b) and does not create a backreference.
1953
1954              Backreferences  work  with  all  forms of pattern matching other
1955              than filename generation, but note that when performing  matches
1956              on  an  entire array, such as ${array#pattern}, or a global sub‐
1957              stitution, such as ${param//pat/repl}, only  the  data  for  the
1958              last  match  remains  available.  In the case of global replace‐
1959              ments this may still be useful.  See the example for the m  flag
1960              below.
1961
1962              The  numbering  of  backreferences strictly follows the order of
1963              the opening parentheses  from  left  to  right  in  the  pattern
1964              string,  although  sets of parentheses may be nested.  There are
1965              special rules for parentheses followed by `#' or `##'.  Only the
1966              last match of the parenthesis is remembered: for example, in `[[
1967              abab =  (#b)([ab])#  ]]',  only  the  final  `b'  is  stored  in
1968              match[1].   Thus extra parentheses may be necessary to match the
1969              complete segment: for example, use  `X((ab|cd)#)Y'  to  match  a
1970              whole  string  of either `ab' or `cd' between `X' and `Y', using
1971              the value of $match[1] rather than $match[2].
1972
1973              If the match fails none of the parameters is altered, so in some
1974              cases  it  may  be  necessary to initialise them beforehand.  If
1975              some of the backreferences fail to match  --  which  happens  if
1976              they are in an alternate branch which fails to match, or if they
1977              are followed by # and matched zero times  --  then  the  matched
1978              string is set to the empty string, and the start and end indices
1979              are set to -1.
1980
1981              Pattern matching with backreferences  is  slightly  slower  than
1982              without.
1983
1984       B      Deactivate  backreferences,  negating  the  effect of the b flag
1985              from that point on.
1986
1987       cN,M   The flag (#cN,M) can be used anywhere that the # or ## operators
1988              can  be  used  except in the expressions `(*/)#' and `(*/)##' in
1989              filename generation, where `/' has special meaning; it cannot be
1990              combined  with  other  globbing  flags  and  a bad pattern error
1991              occurs if it is misplaced.  It is equivalent to the  form  {N,M}
1992              in  regular  expressions.   The  previous  character or group is
1993              required to match between N and M times,  inclusive.   The  form
1994              (#cN) requires exactly N matches; (#c,M) is equivalent to speci‐
1995              fying N as 0; (#cN,) specifies that there is no maximum limit on
1996              the number of matches.
1997
1998       m      Set  references to the match data for the entire string matched;
1999              this is similar to backreferencing and does not work in filename
2000              generation.   The  flag must be in effect at the end of the pat‐
2001              tern, i.e. not local to a group. The parameters $MATCH,  $MBEGIN
2002              and  $MEND  will be set to the string matched and to the indices
2003              of the beginning and end of the string, respectively.   This  is
2004              most  useful in parameter substitutions, as otherwise the string
2005              matched is obvious.
2006
2007              For example,
2008
2009                     arr=(veldt jynx grimps waqf zho buck)
2010                     print ${arr//(#m)[aeiou]/${(U)MATCH}}
2011
2012              forces all the matches (i.e. all vowels) into uppercase,  print‐
2013              ing `vEldt jynx grImps wAqf zhO bUck'.
2014
2015              Unlike backreferences, there is no speed penalty for using match
2016              references, other than the extra substitutions required for  the
2017              replacement strings in cases such as the example shown.
2018
2019       M      Deactivate the m flag, hence no references to match data will be
2020              created.
2021
2022       anum   Approximate matching: num  errors  are  allowed  in  the  string
2023              matched by the pattern.  The rules for this are described in the
2024              next subsection.
2025
2026       s, e   Unlike the other flags, these have only a local effect, and each
2027              must  appear  on  its own:  `(#s)' and `(#e)' are the only valid
2028              forms.  The `(#s)' flag succeeds only at the start of  the  test
2029              string, and the `(#e)' flag succeeds only at the end of the test
2030              string; they correspond to  `^'  and  `$'  in  standard  regular
2031              expressions.  They are useful for matching path segments in pat‐
2032              terns other than those in filename generation (where  path  seg‐
2033              ments  are  in  any  case  treated  separately).   For  example,
2034              `*((#s)|/)test((#e)|/)*' matches a path segment `test' in any of
2035              the   following   strings:   test,  test/at/start,  at/end/test,
2036              in/test/middle.
2037
2038              Another  use  is  in   parameter   substitution;   for   example
2039              `${array/(#s)A*Z(#e)}'  will  remove  only  elements of an array
2040              which match the complete pattern `A*Z'.  There are other ways of
2041              performing many operations of this type, however the combination
2042              of the substitution operations `/' and `//' with the `(#s)'  and
2043              `(#e)' flags provides a single simple and memorable method.
2044
2045              Note that assertions of the form `(^(#s))' also work, i.e. match
2046              anywhere except at the start of the string, although this  actu‐
2047              ally  means  `anything except a zero-length portion at the start
2048              of  the  string';  you  need  to  use  `(""~(#s))'  to  match  a
2049              zero-length portion of the string not at the start.
2050
2051       q      A  `q' and everything up to the closing parenthesis of the glob‐
2052              bing flags are ignored by the pattern matching  code.   This  is
2053              intended  to support the use of glob qualifiers, see below.  The
2054              result is that the pattern `(#b)(*).c(#q.)' can be used both for
2055              globbing and for matching against a string.  In the former case,
2056              the `(#q.)' will be treated as a glob qualifier and  the  `(#b)'
2057              will  not be useful, while in the latter case the `(#b)' is use‐
2058              ful for backreferences and the `(#q.)' will  be  ignored.   Note
2059              that colon modifiers in the glob qualifiers are also not applied
2060              in ordinary pattern matching.
2061
2062       u      Respect the current locale in determining the presence of multi‐
2063              byte  characters  in  a pattern, provided the shell was compiled
2064              with MULTIBYTE_SUPPORT.  This overrides  the  MULTIBYTE  option;
2065              the  default  behaviour  is  taken  from the option.  Compare U.
2066              (Mnemonic: typically multibyte characters are  from  Unicode  in
2067              the UTF-8 encoding, although any extension of ASCII supported by
2068              the system library may be used.)
2069
2070       U      All characters are considered to be a  single  byte  long.   The
2071              opposite of u.  This overrides the MULTIBYTE option.
2072
2073       For  example,  the  test  string  fooxx  can  be matched by the pattern
2074       (#i)FOOXX, but not by (#l)FOOXX,  (#i)FOO(#I)XX  or  ((#i)FOOX)X.   The
2075       string  (#ia2)readme specifies case-insensitive matching of readme with
2076       up to two errors.
2077
2078       When using the ksh syntax for grouping both KSH_GLOB and  EXTENDED_GLOB
2079       must  be  set  and  the left parenthesis should be preceded by @.  Note
2080       also that the flags do not affect letters inside [...] groups, in other
2081       words  (#i)[a-z]  still  matches only lowercase letters.  Finally, note
2082       that when examining whole paths case-insensitively every directory must
2083       be  searched  for  all files which match, so that a pattern of the form
2084       (#i)/foo/bar/... is potentially slow.
2085
2086   Approximate Matching
2087       When matching approximately, the shell keeps  a  count  of  the  errors
2088       found,  which  cannot exceed the number specified in the (#anum) flags.
2089       Four types of error are recognised:
2090
2091       1.     Different characters, as in fooxbar and fooybar.
2092
2093       2.     Transposition of characters, as in banana and abnana.
2094
2095       3.     A character missing in the target string, as  with  the  pattern
2096              road and target string rod.
2097
2098       4.     An extra character appearing in the target string, as with stove
2099              and strove.
2100
2101       Thus, the pattern (#a3)abcd matches dcba, with the errors occurring  by
2102       using  the first rule twice and the second once, grouping the string as
2103       [d][cb][a] and [a][bc][d].
2104
2105       Non-literal parts of the pattern must match exactly, including  charac‐
2106       ters  in  character  ranges:  hence (#a1)???  matches strings of length
2107       four, by applying rule 4 to an empty  part  of  the  pattern,  but  not
2108       strings  of  length  two, since all the ? must match.  Other characters
2109       which must match exactly are initial  dots  in  filenames  (unless  the
2110       GLOB_DOTS option is set), and all slashes in filenames, so that a/bc is
2111       two errors from ab/c (the slash cannot be transposed with another char‐
2112       acter).   Similarly,  errors  are counted separately for non-contiguous
2113       strings in the pattern, so that (ab|cd)ef is two errors from aebf.
2114
2115       When using exclusion  via  the  ~  operator,  approximate  matching  is
2116       treated entirely separately for the excluded part and must be activated
2117       separately.  Thus, (#a1)README~READ_ME matches READ.ME but not READ_ME,
2118       as  the  trailing  READ_ME  is matched without approximation.  However,
2119       (#a1)README~(#a1)READ_ME does not match any pattern of the form READ?ME
2120       as all such forms are now excluded.
2121
2122       Apart  from exclusions, there is only one overall error count; however,
2123       the maximum errors allowed may be altered  locally,  and  this  can  be
2124       delimited  by  grouping.  For example, (#a1)cat((#a0)dog)fox allows one
2125       error in total, which may not occur in the dog section, and the pattern
2126       (#a1)cat(#a0)dog(#a1)fox  is  equivalent.  Note that the point at which
2127       an error is first found is the crucial one for establishing whether  to
2128       use   approximation;  for  example,  (#a1)abc(#a0)xyz  will  not  match
2129       abcdxyz, because the error occurs at the `x',  where  approximation  is
2130       turned off.
2131
2132       Entire   path   segments   may   be   matched  approximately,  so  that
2133       `(#a1)/foo/d/is/available/at/the/bar' allows one error in any path seg‐
2134       ment.   This  is  much  less efficient than without the (#a1), however,
2135       since every directory in the  path  must  be  scanned  for  a  possible
2136       approximate  match.   It is best to place the (#a1) after any path seg‐
2137       ments which are known to be correct.
2138
2139   Recursive Globbing
2140       A pathname component of the form `(foo/)#' matches a path consisting of
2141       zero or more directories matching the pattern foo.
2142
2143       As  a  shorthand, `**/' is equivalent to `(*/)#'; note that this there‐
2144       fore matches files in the current directory as well as  subdirectories.
2145       Thus:
2146
2147              ls (*/)#bar
2148
2149       or
2150
2151              ls **/bar
2152
2153       does  a  recursive  directory search for files named `bar' (potentially
2154       including the file `bar' in the current directory).  This form does not
2155       follow  symbolic links; the alternative form `***/' does, but is other‐
2156       wise identical.  Neither of these can be combined with other  forms  of
2157       globbing  within the same path segment; in that case, the `*' operators
2158       revert to their usual effect.
2159
2160       Even shorter forms are available when  the  option  GLOB_STAR_SHORT  is
2161       set.   In  that  case  if no / immediately follows a ** or *** they are
2162       treated as if both a / plus a further * are present.  Hence:
2163
2164              setopt GLOBSTARSHORT
2165              ls **.c
2166
2167       is equivalent to
2168
2169              ls **/*.c
2170
2171   Glob Qualifiers
2172       Patterns used for filename generation may end in a list  of  qualifiers
2173       enclosed  in  parentheses.  The qualifiers specify which filenames that
2174       otherwise match the given pattern will  be  inserted  in  the  argument
2175       list.
2176
2177       If the option BARE_GLOB_QUAL is set, then a trailing set of parentheses
2178       containing no `|' or `(' characters (or `~' if it is special) is  taken
2179       as  a set of glob qualifiers.  A glob subexpression that would normally
2180       be taken as glob qualifiers, for example `(^x)', can be  forced  to  be
2181       treated  as  part  of  the glob pattern by doubling the parentheses, in
2182       this case producing `((^x))'.
2183
2184       If the option EXTENDED_GLOB is set, a different syntax for glob  quali‐
2185       fiers  is  available,  namely  `(#qx)'  where x is any of the same glob
2186       qualifiers used in the other format.  The qualifiers must still  appear
2187       at  the  end  of  the pattern.  However, with this syntax multiple glob
2188       qualifiers may be chained together.  They are treated as a logical  AND
2189       of  the  individual sets of flags.  Also, as the syntax is unambiguous,
2190       the expression will be treated as glob  qualifiers  just  as  long  any
2191       parentheses contained within it are balanced; appearance of `|', `(' or
2192       `~' does not negate the effect.  Note that qualifiers  will  be  recog‐
2193       nised  in  this form even if a bare glob qualifier exists at the end of
2194       the pattern, for example `*(#q*)(.)' will recognise executable  regular
2195       files if both options are set; however, mixed syntax should probably be
2196       avoided for the sake of clarity.  Note that within conditions using the
2197       `[[' form the presence of a parenthesised expression (#q...) at the end
2198       of a string indicates that globbing should be performed; the expression
2199       may include glob qualifiers, but it is also valid if it is simply (#q).
2200       This does not apply to the right hand side of pattern  match  operators
2201       as the syntax already has special significance.
2202
2203       A qualifier may be any one of the following:
2204
2205       /      directories
2206
2207       F      `full'  (i.e.  non-empty)  directories.   Note that the opposite
2208              sense (^F) expands to empty directories and all non-directories.
2209              Use (/^F) for empty directories.
2210
2211       .      plain files
2212
2213       @      symbolic links
2214
2215       =      sockets
2216
2217       p      named pipes (FIFOs)
2218
2219       *      executable plain files (0100 or 0010 or 0001)
2220
2221       %      device files (character or block special)
2222
2223       %b     block special files
2224
2225       %c     character special files
2226
2227       r      owner-readable files (0400)
2228
2229       w      owner-writable files (0200)
2230
2231       x      owner-executable files (0100)
2232
2233       A      group-readable files (0040)
2234
2235       I      group-writable files (0020)
2236
2237       E      group-executable files (0010)
2238
2239       R      world-readable files (0004)
2240
2241       W      world-writable files (0002)
2242
2243       X      world-executable files (0001)
2244
2245       s      setuid files (04000)
2246
2247       S      setgid files (02000)
2248
2249       t      files with the sticky bit (01000)
2250
2251       fspec  files with access rights matching spec. This spec may be a octal
2252              number optionally preceded by a `=', a `+', or a `-'. If none of
2253              these  characters is given, the behavior is the same as for `='.
2254              The octal number describes the mode bits to be expected, if com‐
2255              bined  with  a  `=',  the  value given must match the file-modes
2256              exactly, with a `+', at least the bits in the given number  must
2257              be set in the file-modes, and with a `-', the bits in the number
2258              must not be set. Giving a `?' instead of a octal digit  anywhere
2259              in  the  number  ensures  that  the  corresponding  bits  in the
2260              file-modes are not checked, this is only useful  in  combination
2261              with `='.
2262
2263              If the qualifier `f' is followed by any other character anything
2264              up to the next matching character (`[', `{', and `<' match  `]',
2265              `}',  and  `>' respectively, any other character matches itself)
2266              is taken as a list of comma-separated sub-specs.  Each  sub-spec
2267              may  be  either  an octal number as described above or a list of
2268              any of the characters `u', `g', `o', and `a', followed by a `=',
2269              a  `+',  or  a  `-', followed by a list of any of the characters
2270              `r', `w', `x', `s', and `t', or an octal digit. The  first  list
2271              of  characters specify which access rights are to be checked. If
2272              a `u' is given, those for the owner of the file are used,  if  a
2273              `g'  is  given,  those  of the group are checked, a `o' means to
2274              test those of other users, and the `a' says to  test  all  three
2275              groups. The `=', `+', and `-' again says how the modes are to be
2276              checked and have the same meaning as  described  for  the  first
2277              form  above.  The  second  list of characters finally says which
2278              access rights are to be expected: `r' for read access,  `w'  for
2279              write  access,  `x'  for  the  right  to execute the file (or to
2280              search a directory), `s' for the setuid and setgid bits, and `t'
2281              for the sticky bit.
2282
2283              Thus,  `*(f70?)'  gives  the files for which the owner has read,
2284              write, and execute permission, and for which other group members
2285              have  no rights, independent of the permissions for other users.
2286              The pattern `*(f-100)' gives all files for which the owner  does
2287              not  have  execute  permission,  and `*(f:gu+w,o-rx:)' gives the
2288              files for which the owner and the other  members  of  the  group
2289              have  at least write permission, and for which other users don't
2290              have read or execute permission.
2291
2292       estring
2293       +cmd   The string will be executed as shell code.  The filename will be
2294              included in the list if and only if the code returns a zero sta‐
2295              tus (usually the status of the last command).
2296
2297              In the first form, the first character after  the  `e'  will  be
2298              used as a separator and anything up to the next matching separa‐
2299              tor will be taken  as the string; `[', `{', and `<'  match  `]',
2300              `}',  and  `>',  respectively, while any other character matches
2301              itself. Note that expansions must be quoted  in  the  string  to
2302              prevent  them  from  being  expanded  before  globbing  is done.
2303              string is then executed as shell code.  The string  globqual  is
2304              appended  to  the  array zsh_eval_context the duration of execu‐
2305              tion.
2306
2307              During the execution of  string  the  filename  currently  being
2308              tested is available in the parameter REPLY; the parameter may be
2309              altered to a string to be inserted into the list instead of  the
2310              original  filename.  In addition, the parameter reply may be set
2311              to an array or a string, which overrides the value of REPLY.  If
2312              set  to  an  array, the latter is inserted into the command line
2313              word by word.
2314
2315              For  example,  suppose  a  directory  contains  a  single   file
2316              `lonely'.   Then  the expression `*(e:'reply=(${REPLY}{1,2})':)'
2317              will cause the words `lonely1' and `lonely2' to be inserted into
2318              the command line.  Note the quoting of string.
2319
2320              The  form  +cmd  has  the  same effect, but no delimiters appear
2321              around cmd.  Instead, cmd is taken as the  longest  sequence  of
2322              characters  following the + that are alphanumeric or underscore.
2323              Typically cmd will be the name of a shell function that contains
2324              the appropriate test.  For example,
2325
2326                     nt() { [[ $REPLY -nt $NTREF ]] }
2327                     NTREF=reffile
2328                     ls -l *(+nt)
2329
2330              lists  all  files  in the directory that have been modified more
2331              recently than reffile.
2332
2333       ddev   files on the device dev
2334
2335       l[-|+]ct
2336              files having a link count less than ct (-), greater than ct (+),
2337              or equal to ct
2338
2339       U      files owned by the effective user ID
2340
2341       G      files owned by the effective group ID
2342
2343       uid    files  owned  by  user ID id if that is a number.  Otherwise, id
2344              specifies a user name: the character after the `u' will be taken
2345              as  a  separator and the string between it and the next matching
2346              separator will be taken as a user name.  The starting separators
2347              `[',  `{', and `<' match the final separators `]', `}', and `>',
2348              respectively; any other character matches itself.  The  selected
2349              files  are  those  owned by this user.  For example, `u:foo:' or
2350              `u[foo]' selects files owned by user `foo'.
2351
2352       gid    like uid but with group IDs or names
2353
2354       a[Mwhms][-|+]n
2355              files accessed exactly n days ago.  Files  accessed  within  the
2356              last  n  days  are  selected  using a negative value for n (-n).
2357              Files accessed more than n days ago are selected by a positive n
2358              value  (+n).  Optional unit specifiers `M', `w', `h', `m' or `s'
2359              (e.g. `ah5') cause the check to be performed with months (of  30
2360              days), weeks, hours, minutes or seconds instead of days, respec‐
2361              tively.  An explicit `d' for days is also allowed.
2362
2363              Any fractional part of the difference between  the  access  time
2364              and  the current part in the appropriate units is ignored in the
2365              comparison.  For  instance,  `echo  *(ah-5)'  would  echo  files
2366              accessed  within the last five hours, while `echo *(ah+5)' would
2367              echo files accessed at least six hours ago,  as  times  strictly
2368              between five and six hours are treated as five hours.
2369
2370       m[Mwhms][-|+]n
2371              like  the  file  access  qualifier, except that it uses the file
2372              modification time.
2373
2374       c[Mwhms][-|+]n
2375              like the file access qualifier, except that  it  uses  the  file
2376              inode change time.
2377
2378       L[+|-]n
2379              files less than n bytes (-), more than n bytes (+), or exactly n
2380              bytes in length.
2381
2382              If this flag is directly followed by a size specifier `k' (`K'),
2383              `m'  (`M'),  or  `p' (`P') (e.g. `Lk-50') the check is performed
2384              with kilobytes, megabytes, or blocks  (of  512  bytes)  instead.
2385              (On  some  systems additional specifiers are available for giga‐
2386              bytes, `g' or `G', and terabytes, `t' or `T'.) If a size  speci‐
2387              fier  is  used  a  file is regarded as "exactly" the size if the
2388              file size rounded up to the next unit is equal to the test size.
2389              Hence `*(Lm1)' matches files from 1 byte up to 1 Megabyte inclu‐
2390              sive.  Note also that the set of files "less than" the test size
2391              only  includes  files  that  would  not match the equality test;
2392              hence `*(Lm-1)' only matches files of zero size.
2393
2394       ^      negates all qualifiers following it
2395
2396       -      toggles between making the qualifiers  work  on  symbolic  links
2397              (the default) and the files they point to
2398
2399       M      sets the MARK_DIRS option for the current pattern
2400
2401       T      appends a trailing qualifier mark to the filenames, analogous to
2402              the LIST_TYPES option, for the current pattern (overrides M)
2403
2404       N      sets the NULL_GLOB option for the current pattern
2405
2406       D      sets the GLOB_DOTS option for the current pattern
2407
2408       n      sets the NUMERIC_GLOB_SORT option for the current pattern
2409
2410       Yn     enables short-circuit mode: the pattern will expand to at most n
2411              filenames.   If  more  than  n  matches  exist, only the first n
2412              matches in directory traversal order will be considered.
2413
2414              Implies oN when no oc qualifier is used.
2415
2416       oc     specifies how the names of the files should be sorted. If c is n
2417              they are sorted by name; if it is L they are sorted depending on
2418              the size (length) of the files; if l they are sorted by the num‐
2419              ber  of  links; if a, m, or c they are sorted by the time of the
2420              last access, modification, or inode change respectively;  if  d,
2421              files  in  subdirectories  appear  before  those  in the current
2422              directory at each level of the search -- this is  best  combined
2423              with  other  criteria,  for  example `odon' to sort on names for
2424              files within the same directory; if N, no sorting is  performed.
2425              Note  that a, m, and c compare the age against the current time,
2426              hence the first name in the list is the youngest file. Also note
2427              that  the  modifiers ^ and - are used, so `*(^-oL)' gives a list
2428              of all files sorted by file size in descending order,  following
2429              any  symbolic  links.   Unless oN is used, multiple order speci‐
2430              fiers may occur to resolve ties.
2431
2432              The default sorting is n (by name) unless the Y  glob  qualifier
2433              is used, in which case it is N (unsorted).
2434
2435              oe  and  o+  are  special cases; they are each followed by shell
2436              code, delimited as for the e glob qualifier and the + glob qual‐
2437              ifier  respectively  (see above).  The code is executed for each
2438              matched file with the parameter REPLY set to  the  name  of  the
2439              file  on  entry  and globsort appended to zsh_eval_context.  The
2440              code should modify the parameter  REPLY  in  some  fashion.   On
2441              return,  the  value of the parameter is used instead of the file
2442              name as the string on which to sort.  Unlike other  sort  opera‐
2443              tors,  oe and o+ may be repeated, but note that the maximum num‐
2444              ber of sort operators of any kind that may appear  in  any  glob
2445              expression is 12.
2446
2447       Oc     like  `o',  but  sorts in descending order; i.e. `*(^oc)' is the
2448              same as `*(Oc)' and `*(^Oc)' is the same as `*(oc)';  `Od'  puts
2449              files in the current directory before those in subdirectories at
2450              each level of the search.
2451
2452       [beg[,end]]
2453              specifies which of the matched filenames should be  included  in
2454              the  returned  list.  The  syntax  is the same as for array sub‐
2455              scripts. beg and the optional end may  be  mathematical  expres‐
2456              sions. As in parameter subscripting they may be negative to make
2457              them count from the last  match  backward.  E.g.:  `*(-OL[1,3])'
2458              gives a list of the names of the three largest files.
2459
2460       Pstring
2461              The  string  will  be prepended to each glob match as a separate
2462              word.  string is delimited in the same way as arguments to the e
2463              glob  qualifier described above.  The qualifier can be repeated;
2464              the words are prepended separately so that the resulting command
2465              line contains the words in the same order they were given in the
2466              list of glob qualifiers.
2467
2468              A typical use for this is to prepend an option before all occur‐
2469              rences  of a file name; for example, the pattern `*(P:-f:)' pro‐
2470              duces the command line arguments `-f file1 -f file2 ...'
2471
2472              If the modifier ^  is  active,  then  string  will  be  appended
2473              instead of prepended.  Prepending and appending is done indepen‐
2474              dently so both can be used on  the  same  glob  expression;  for
2475              example  by writing `*(P:foo:^P:bar:^P:baz:)' which produces the
2476              command line arguments `foo baz file1 bar ...'
2477
2478       More than one of these lists can be combined, separated by commas.  The
2479       whole  list  matches  if at least one of the sublists matches (they are
2480       `or'ed, the qualifiers in the sublists are `and'ed).  Some  qualifiers,
2481       however,  affect  all  matches generated, independent of the sublist in
2482       which they are given.  These are the qualifiers  `M',  `T',  `N',  `D',
2483       `n', `o', `O' and the subscripts given in brackets (`[...]').
2484
2485       If  a  `:' appears in a qualifier list, the remainder of the expression
2486       in parenthesis is interpreted as a modifier  (see  the  section  `Modi‐
2487       fiers'  in  the  section  `History  Expansion').  Each modifier must be
2488       introduced by a separate `:'.  Note also that the result after  modifi‐
2489       cation  does not have to be an existing file.  The name of any existing
2490       file can be followed by a modifier of the  form  `(:...)'  even  if  no
2491       actual  filename  generation is performed, although note that the pres‐
2492       ence of the parentheses causes the entire expression to be subjected to
2493       any global pattern matching options such as NULL_GLOB. Thus:
2494
2495              ls *(-/)
2496
2497       lists all directories and symbolic links that point to directories, and
2498
2499              ls *(-@)
2500
2501       lists all broken symbolic links, and
2502
2503              ls *(%W)
2504
2505       lists all world-writable device files in the current directory, and
2506
2507              ls *(W,X)
2508
2509       lists  all  files  in  the current directory that are world-writable or
2510       world-executable, and
2511
2512              echo /tmp/foo*(u0^@:t)
2513
2514       outputs the basename of all root-owned files beginning with the  string
2515       `foo' in /tmp, ignoring symlinks, and
2516
2517              ls *.*~(lex|parse).[ch](^D^l1)
2518
2519       lists  all  files  having a link count of one whose names contain a dot
2520       (but not those starting with  a  dot,  since  GLOB_DOTS  is  explicitly
2521       switched off) except for lex.c, lex.h, parse.c and parse.h.
2522
2523              print b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)
2524
2525       demonstrates  how  colon  modifiers and other qualifiers may be chained
2526       together.  The ordinary qualifier `.' is applied first, then the  colon
2527       modifiers  in order from left to right.  So if EXTENDED_GLOB is set and
2528       the base pattern matches the regular file builtin.pro, the  shell  will
2529       print `shmiltin.shmo'.
2530
2531
2532
2533zsh 5.7.1                      February 3, 2019                     ZSHEXPN(1)
Impressum