zshexpn man page on Manjaro

Man page or keyword search:  
man Server   11224 pages
apropos Keyword Search (all sections)
Output format
Manjaro logo
[printable version]

ZSHEXPN(1)							    ZSHEXPN(1)

NAME
       zshexpn - zsh expansion and substitution

DESCRIPTION
       The  following types of expansions are performed in the indicated order
       in five steps:

       History Expansion
	      This is performed only in interactive shells.

       Alias Expansion
	      Aliases are expanded immediately	before	the  command  line  is
	      parsed as explained under Aliasing in zshmisc(1).

       Process Substitution
       Parameter Expansion
       Command Substitution
       Arithmetic Expansion
       Brace Expansion
	      These  five  are performed in one step in left-to-right fashion.
	      After these expansions, all unquoted occurrences of the  charac‐
	      ters `\', `'' and `"' are removed.

       Filename Expansion
	      If  the  SH_FILE_EXPANSION option is set, the order of expansion
	      is modified for compatibility with sh and	 ksh.	In  that  case
	      filename	expansion  is performed immediately after alias expan‐
	      sion, preceding the set of five expansions mentioned above.

       Filename Generation
	      This expansion, commonly referred to as globbing, is always done
	      last.

       The following sections explain the types of expansion in detail.

HISTORY EXPANSION
       History	expansion  allows you to use words from previous command lines
       in the command line you are typing.  This simplifies  spelling  correc‐
       tions and the repetition of complicated commands or arguments.

       Immediately  before  execution,	each  command  is saved in the history
       list, the size of which is controlled by the HISTSIZE  parameter.   The
       one  most  recent  command  is always retained in any case.  Each saved
       command in the history list is called a history event and is assigned a
       number,	beginning  with 1 (one) when the shell starts up.  The history
       number that you may  see	 in  your  prompt  (see	 EXPANSION  OF	PROMPT
       SEQUENCES  in  zshmisc(1))  is the number that is to be assigned to the
       next command.

   Overview
       A history expansion begins with the first character  of	the  histchars
       parameter,  which is `!' by default, and may occur anywhere on the com‐
       mand line; history expansions do not nest.  The `!' can be escaped with
       `\' or can be enclosed between a pair of single quotes ('') to suppress
       its special meaning.  Double quotes will not work for this.   Following
       this history character is an optional event designator (see the section
       `Event Designators') and then an optional word designator (the  section
       `Word  Designators');  if  neither  of these designators is present, no
       history expansion occurs.

       Input lines  containing	history	 expansions  are  echoed  after	 being
       expanded,  but  before  any  other expansions take place and before the
       command is executed.  It is this expanded form that is recorded as  the
       history event for later references.

       By  default, a history reference with no event designator refers to the
       same event as any preceding history reference on that command line;  if
       it  is the only history reference in a command, it refers to the previ‐
       ous command.  However, if the option CSH_JUNKIE_HISTORY	is  set,  then
       every  history  reference  with no event specification always refers to
       the previous command.

       For example, `!' is the event designator for the previous  command,  so
       `!!:1'  always  refers  to  the first word of the previous command, and
       `!!$' always refers to the last word of	the  previous  command.	  With
       CSH_JUNKIE_HISTORY set, then `!:1' and `!$' function in the same manner
       as `!!:1' and `!!$', respectively.  Conversely,	if  CSH_JUNKIE_HISTORY
       is  unset,  then	 `!:1'	and  `!$'  refer  to the first and last words,
       respectively, of the same event referenced by the nearest other history
       reference  preceding them on the current command line, or to the previ‐
       ous command if there is no preceding reference.

       The character sequence `^foo^bar' (where `^'  is	 actually  the	second
       character of the histchars parameter) repeats the last command, replac‐
       ing the string foo with bar.  More precisely, the sequence  `^foo^bar^'
       is synonymous with `!!:s^foo^bar^', hence other modifiers (see the sec‐
       tion  `Modifiers')  may	follow	the   final   `^'.    In   particular,
       `^foo^bar^:G' performs a global substitution.

       If  the	shell encounters the character sequence `!"' in the input, the
       history mechanism is temporarily disabled until the current  list  (see
       zshmisc(1))  is	fully parsed.  The `!"' is removed from the input, and
       any subsequent `!' characters have no special significance.

       A less convenient but more comprehensible form of command history  sup‐
       port is provided by the fc builtin.

   Event Designators
       An  event designator is a reference to a command-line entry in the his‐
       tory list.  In the list below, remember that the initial	 `!'  in  each
       item  may  be  changed  to  another  character by setting the histchars
       parameter.

       !      Start a history expansion, except when followed by a blank, new‐
	      line,  `=' or `('.  If followed immediately by a word designator
	      (see the section `Word Designators'), this forms a history  ref‐
	      erence with no event designator (see the section `Overview').

       !!     Refer  to	 the  previous	command.   By  itself,	this expansion
	      repeats the previous command.

       !n     Refer to command-line n.

       !-n    Refer to the current command-line minus n.

       !str   Refer to the most recent command starting with str.

       !?str[?]
	      Refer to the most recent command containing str.	 The  trailing
	      `?'  is necessary if this reference is to be followed by a modi‐
	      fier or followed by any text that is not to be  considered  part
	      of str.

       !#     Refer  to the current command line typed in so far.  The line is
	      treated as if it were complete up	 to  and  including  the  word
	      before the one with the `!#' reference.

       !{...} Insulate a history reference from adjacent characters (if neces‐
	      sary).

   Word Designators
       A word designator indicates which word or words of a given command line
       are to be included in a history reference.  A `:' usually separates the
       event specification from the word designator.  It may be	 omitted  only
       if  the	word designator begins with a `^', `$', `*', `-' or `%'.  Word
       designators include:

       0      The first input word (command).
       n      The nth argument.
       ^      The first argument.  That is, 1.
       $      The last argument.
       %      The word matched by (the most recent) ?str search.
       x-y    A range of words; x defaults to 0.
       *      All the arguments, or a null value if there are none.
       x*     Abbreviates `x-$'.
       x-     Like `x*' but omitting word $.

       Note that a `%' word designator works only when used in	one  of	 `!%',
       `!:%'  or `!?str?:%', and only when used after a !? expansion (possibly
       in an earlier command).	Anything else results in  an  error,  although
       the error may not be the most obvious one.

   Modifiers
       After  the  optional  word designator, you can add a sequence of one or
       more of the following modifiers, each preceded by a `:'.	  These	 modi‐
       fiers  also  work  on  the  result of filename generation and parameter
       expansion, except where noted.

       a      Turn a file name into an absolute path:	prepends  the  current
	      directory, if necessary, and resolves any use of `..' and `.' in
	      the path.	 Note that the transformation takes place even if  the
	      file or any intervening directories do not exist.

       A      As  `a',	but also resolve use of symbolic links where possible.
	      Note that resolution of `..' occurs before  resolution  of  sym‐
	      bolic  links.   This  call is equivalent to a unless your system
	      has the realpath system call (modern systems do).

       c      Resolve a command name into an absolute path  by	searching  the
	      command path given by the PATH variable.	This does not work for
	      commands containing directory parts.  Note also that  this  does
	      not  usually  work as a glob qualifier unless a file of the same
	      name is found in the current directory.

       e      Remove all but the part of the filename extension following  the
	      `.';  see	 the  definition  of  the  filename  extension	in the
	      description of the r modifier below.   Note  that	 according  to
	      that definition the result will be empty if the string ends with
	      a `.'.

       h      Remove a trailing pathname component, leaving  the  head.	  This
	      works like `dirname'.

       l      Convert the words to all lowercase.

       p      Print  the  new  command but do not execute it.  Only works with
	      history expansion.

       q      Quote the substituted  words,  escaping  further	substitutions.
	      Works with history expansion and parameter expansion, though for
	      parameters it is only useful if the  resulting  text  is	to  be
	      re-evaluated such as by eval.

       Q      Remove one level of quotes from the substituted words.

       r      Remove a filename extension leaving the root name.  Strings with
	      no filename extension are not altered.  A filename extension  is
	      a `.' followed by any number of characters (including zero) that
	      are neither `.' nor `/' and that continue	 to  the  end  of  the
	      string.  For example, the extension of `foo.orig.c' is `.c', and
	      `dir.c/foo' has no extension.

       s/l/r[/]
	      Substitute r for l as described below.  The substitution is done
	      only  for	 the  first string that matches l.  For arrays and for
	      filename generation, this applies to each word of	 the  expanded
	      text.  See below for further notes on substitutions.

	      The  forms  `gs/l/r' and `s/l/r/:G' perform global substitution,
	      i.e. substitute every occurrence of r for l.  Note that the g or
	      :G must appear in exactly the position shown.

	      See further notes on this form of substitution below.

       &      Repeat  the  previous  s	substitution.  Like s, may be preceded
	      immediately by a g.  In parameter expansion the  &  must	appear
	      inside braces, and in filename generation it must be quoted with
	      a backslash.

       t      Remove all leading pathname components, leaving the tail.	  This
	      works like `basename'.

       u      Convert the words to all uppercase.

       x      Like  q, but break into words at whitespace.  Does not work with
	      parameter expansion.

       The s/l/r/ substitution works as follows.   By  default	the  left-hand
       side  of	 substitutions	are  not patterns, but character strings.  Any
       character can be used as the delimiter in place of  `/'.	  A  backslash
       quotes	the   delimiter	  character.	The   character	 `&',  in  the
       right-hand-side r, is replaced by the text from the  left-hand-side  l.
       The  `&'	 can  be  quoted with a backslash.  A null l uses the previous
       string either from the previous l or from the contextual scan string  s
       from  `!?s'.  You can omit the rightmost delimiter if a newline immedi‐
       ately follows r; the rightmost `?' in a context scan can	 similarly  be
       omitted.	 Note the same record of the last l and r is maintained across
       all forms of expansion.

       Note that if a `&' is used within glob qualifers an extra backslash  is
       needed as a & is a special character in this case.

       If  the	option HIST_SUBST_PATTERN is set, l is treated as a pattern of
       the usual form described in  the	 section  FILENAME  GENERATION	below.
       This can be used in all the places where modifiers are available; note,
       however, that in globbing qualifiers parameter substitution has already
       taken  place,  so parameters in the replacement string should be quoted
       to ensure they are replaced at the correct time.	 Note also  that  com‐
       plicated	 patterns  used	 in  globbing qualifiers may need the extended
       glob qualifier notation (#q:s/.../.../) in order for the shell to  rec‐
       ognize the expression as a glob qualifier.  Further, note that bad pat‐
       terns in the substitution are not subject to the NO_BAD_PATTERN	option
       so will cause an error.

       When  HIST_SUBST_PATTERN	 is set, l may start with a # to indicate that
       the pattern must match at the start of the string  to  be  substituted,
       and a % may appear at the start or after an # to indicate that the pat‐
       tern must match at the end of the string to be substituted.  The % or #
       may be quoted with two backslashes.

       For  example,  the following piece of filename generation code with the
       EXTENDED_GLOB option:

	      print *.c(#q:s/#%(#b)s(*).c/'S${match[1]}.C'/)

       takes the expansion of *.c and  applies	the  glob  qualifiers  in  the
       (#q...)	expression, which consists of a substitution modifier anchored
       to the start and end of each word (#%).	This turns  on	backreferences
       ((#b)),	so  that  the  parenthesised subexpression is available in the
       replacement string as ${match[1]}.  The replacement string is quoted so
       that the parameter is not substituted before the start of filename gen‐
       eration.

       The following f, F, w and W modifiers work only with  parameter	expan‐
       sion and filename generation.  They are listed here to provide a single
       point of reference for all modifiers.

       f      Repeats the immediately (without	a  colon)  following  modifier
	      until the resulting word doesn't change any more.

       F:expr:
	      Like  f,	but repeats only n times if the expression expr evalu‐
	      ates to n.  Any character can be used instead  of	 the  `:';  if
	      `(',  `[',  or `{' is used as the opening delimiter, the closing
	      delimiter should be ')', `]', or `}', respectively.

       w      Makes the immediately following modifier work on	each  word  in
	      the string.

       W:sep: Like  w  but  words are considered to be the parts of the string
	      that are separated by sep. Any character can be used instead  of
	      the `:'; opening parentheses are handled specially, see above.

PROCESS SUBSTITUTION
       Each  part  of  a  command  argument  that  takes  the  form `<(list)',
       `>(list)' or `=(list)' is subject to process substitution.  The expres‐
       sion  may be preceded or followed by other strings except that, to pre‐
       vent clashes with commonly occurring strings  and  patterns,  the  last
       form  must  occur at the start of a command argument, and the forms are
       only expanded when  first  parsing  command  or	assignment  arguments.
       Process	substitutions  may be used following redirection operators; in
       this case, the substitution must appear with no trailing string.

       In the case of the < or > forms, the shell runs the commands in list as
       a  subprocess of the job executing the shell command line.  If the sys‐
       tem supports the /dev/fd mechanism, the command argument is the name of
       the  device  file corresponding to a file descriptor; otherwise, if the
       system supports named pipes (FIFOs), the command	 argument  will	 be  a
       named  pipe.   If the form with > is selected then writing on this spe‐
       cial file will provide input for list.  If < is	used,  then  the  file
       passed  as  an  argument	 will  be  connected to the output of the list
       process.	 For example,

	      paste <(cut -f1 file1) <(cut -f3 file2) |
	      tee >(process1) >(process2) >/dev/null

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the  results  together,	and  sends  it	to  the processes process1 and
       process2.

       If =(...) is used instead of <(...), then the file passed as  an	 argu‐
       ment  will be the name of a temporary file containing the output of the
       list process.  This may be used instead of the <	 form  for  a  program
       that expects to lseek (see lseek(2)) on the input file.

       There is an optimisation for substitutions of the form =(<<<arg), where
       arg is a single-word argument to the here-string redirection <<<.  This
       form produces a file name containing the value of arg after any substi‐
       tutions have been performed.  This is handled entirely within the  cur‐
       rent  shell.   This  is	effectively  the  reverse  of the special form
       $(<arg) which treats arg as a file name and replaces it with the file's
       contents.

       The = form is useful as both the /dev/fd and the named pipe implementa‐
       tion of <(...) have drawbacks.  In the former case, some programmes may
       automatically  close  the  file descriptor in question before examining
       the file on the command line, particularly if  this  is	necessary  for
       security	 reasons such as when the programme is running setuid.	In the
       second case, if the programme does not actually open the file, the sub‐
       shell  attempting  to read from or write to the pipe will (in a typical
       implementation, different operating systems may have  different	behav‐
       iour)  block for ever and have to be killed explicitly.	In both cases,
       the shell actually supplies the information using a pipe, so that  pro‐
       grammes that expect to lseek (see lseek(2)) on the file will not work.

       Also  note  that	 the  previous example can be more compactly and effi‐
       ciently written (provided the MULTIOS option is set) as:

	      paste <(cut -f1 file1) <(cut -f3 file2) \
	      > >(process1) > >(process2)

       The shell uses pipes instead of	FIFOs  to  implement  the  latter  two
       process substitutions in the above example.

       There  is  an additional problem with >(process); when this is attached
       to an external command, the parent shell does not wait for  process  to
       finish  and  hence  an immediately following command cannot rely on the
       results being complete.	The problem  and  solution  are	 the  same  as
       described  in the section MULTIOS in zshmisc(1).	 Hence in a simplified
       version of the example above:

	      paste <(cut -f1 file1) <(cut -f3 file2) > >(process)

       (note that no MULTIOS are involved), process will be run asynchronously
       as far as the parent shell is concerned.	 The workaround is:

	      { paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)

       The  extra  processes here are spawned from the parent shell which will
       wait for their completion.

       Another problem arises any time a job with a substitution that requires
       a  temporary  file  is  disowned by the shell, including the case where
       `&!' or `&|' appears at the end of a command containing a  subsitution.
       In  that case the temporary file will not be cleaned up as the shell no
       longer has any memory of the job.  A workaround is to use  a  subshell,
       for example,

	      (mycmd =(myoutput)) &!

       as  the forked subshell will wait for the command to finish then remove
       the temporary file.

       A general workaround to ensure a process substitution  endures  for  an
       appropriate length of time is to pass it as a parameter to an anonymous
       shell function (a piece of shell code  that  is	run  immediately  with
       function scope).	 For example, this code:

	      () {
		 print File $1:
		 cat $1
	      } =(print This be the verse)

       outputs something resembling the following

	      File /tmp/zsh6nU0kS:
	      This be the verse

       The  temporary file created by the process substitution will be deleted
       when the function exits.

PARAMETER EXPANSION
       The character `$' is used to introduce parameter expansions.  See  zsh‐
       param(1) for a description of parameters, including arrays, associative
       arrays, and subscript notation to access individual array elements.

       Note in particular the fact that words of unquoted parameters  are  not
       automatically  split  on	 whitespace unless the option SH_WORD_SPLIT is
       set; see references to this option below for more details.  This is  an
       important difference from other shells.

       In  the	expansions discussed below that require a pattern, the form of
       the pattern is the same as that used for filename generation;  see  the
       section	`Filename  Generation'.	  Note that these patterns, along with
       the replacement text of any substitutions, are  themselves  subject  to
       parameter  expansion,  command  substitution, and arithmetic expansion.
       In addition to the following operations, the colon modifiers  described
       in  the	section	 `Modifiers' in the section `History Expansion' can be
       applied:	 for example, ${i:s/foo/bar/} performs string substitution  on
       the expansion of parameter $i.

       ${name}
	      The  value,  if  any, of the parameter name is substituted.  The
	      braces are required if the expansion is to be followed by a let‐
	      ter,  digit, or underscore that is not to be interpreted as part
	      of name.	In addition, more complicated  forms  of  substitution
	      usually require the braces to be present; exceptions, which only
	      apply if the option KSH_ARRAYS is not set,  are  a  single  sub‐
	      script  or  any colon modifiers appearing after the name, or any
	      of the characters `^', `=', `~', `#' or `+' appearing before the
	      name, all of which work with or without braces.

	      If  name is an array parameter, and the KSH_ARRAYS option is not
	      set, then the value of each element of name is substituted,  one
	      element  per word.  Otherwise, the expansion results in one word
	      only; with KSH_ARRAYS, this is the first element	of  an	array.
	      No   field   splitting   is   done  on  the  result  unless  the
	      SH_WORD_SPLIT  option  is	 set.	See  also  the	flags  =   and
	      s:string:.

       ${+name}
	      If  name is the name of a set parameter `1' is substituted, oth‐
	      erwise `0' is substituted.

       ${name-word}
       ${name:-word}
	      If name is set, or in the second form is non-null, then  substi‐
	      tute  its	 value; otherwise substitute word.  In the second form
	      name may be omitted, in which case word is always substituted.

       ${name+word}
       ${name:+word}
	      If name is set, or in the second form is non-null, then  substi‐
	      tute word; otherwise substitute nothing.

       ${name=word}
       ${name:=word}
       ${name::=word}
	      In  the first form, if name is unset then set it to word; in the
	      second form, if name is unset or null then set it to  word;  and
	      in  the  third  form,  unconditionally set name to word.	In all
	      forms, the value of the parameter is then substituted.

       ${name?word}
       ${name:?word}
	      In the first form, if name is set, or in the second form if name
	      is  both set and non-null, then substitute its value; otherwise,
	      print word and exit from the shell.  Interactive shells  instead
	      return  to the prompt.  If word is omitted, then a standard mes‐
	      sage is printed.

       In any of the above expressions that test a variable and substitute  an
       alternate  word,	 note  that  you can use standard shell quoting in the
       word  value  to	selectively  override  the  splitting  done   by   the
       SH_WORD_SPLIT option and the = flag, but not splitting by the s:string:
       flag.

       In the following expressions, when name is an array and	the  substitu‐
       tion is not quoted, or if the `(@)' flag or the name[@] syntax is used,
       matching and replacement is performed on each array element separately.

       ${name#pattern}
       ${name##pattern}
	      If the pattern matches the beginning of the value of name,  then
	      substitute  the  value of name with the matched portion deleted;
	      otherwise, just substitute the value  of	name.	In  the	 first
	      form,  the smallest matching pattern is preferred; in the second
	      form, the largest matching pattern is preferred.

       ${name%pattern}
       ${name%%pattern}
	      If the pattern matches the end of the value of name,  then  sub‐
	      stitute the value of name with the matched portion deleted; oth‐
	      erwise, just substitute the value of name.  In the  first	 form,
	      the  smallest matching pattern is preferred; in the second form,
	      the largest matching pattern is preferred.

       ${name:#pattern}
	      If the pattern matches the value of name,	 then  substitute  the
	      empty  string; otherwise, just substitute the value of name.  If
	      name is an array the matching array elements  are	 removed  (use
	      the `(M)' flag to remove the non-matched elements).

       ${name:|arrayname}
	      If  arrayname is the name (N.B., not contents) of an array vari‐
	      able, then any elements contained in arrayname are removed  from
	      the substitution of name.	 If the substitution is scalar, either
	      because name is a scalar variable or the expression  is  quoted,
	      the  elements of arrayname are instead tested against the entire
	      expression.

       ${name:*arrayname}
	      Similar to the preceding subsitution, but in the opposite sense,
	      so that entries present in both the original substitution and as
	      elements of arrayname are retained and others removed.

       ${name:offset}
       ${name:offset:length}
	      This syntax gives effects similar to parameter  subscripting  in
	      the  form $name[start,end], but is compatible with other shells;
	      note that both offset and	 length	 are  interpreted  differently
	      from the components of a subscript.

	      If offset is non-negative, then if the variable name is a scalar
	      substitute the contents  starting	 offset	 characters  from  the
	      first  character	of the string, and if name is an array substi‐
	      tute elements starting offset elements from the  first  element.
	      If length is given, substitute that many characters or elements,
	      otherwise the entire rest of the scalar or array.

	      A positive offset is always treated as the offset of a character
	      or  element  in  name from the first character or element of the
	      array (this is different from native  zsh	 subscript  notation).
	      Hence  0	refers to the first character or element regardless of
	      the setting of the option KSH_ARRAYS.

	      A negative offset counts backwards from the end of the scalar or
	      array,  so that -1 corresponds to the last character or element,
	      and so on.

	      When positive, length counts from the offset position toward the
	      end  of  the scalar or array.  When negative, length counts back
	      from the end.  If this results in a position smaller  than  off‐
	      set, a diagnostic is printed and nothing is substituted.

	      The option MULTIBYTE is obeyed, i.e. the offset and length count
	      multibyte characters where appropriate.

	      offset and length undergo the same set of shell substitutions as
	      for  scalar  assignment;	in  addition, they are then subject to
	      arithmetic evaluation.  Hence, for example

		     print ${foo:3}
		     print ${foo: 1 + 2}
		     print ${foo:$(( 1 + 2))}
		     print ${foo:$(echo 1 + 2)}

	      all have the same effect, extracting the string starting at  the
	      fourth  character	 of  $foo  if  the  substution would otherwise
	      return a scalar, or the array starting at the fourth element  if
	      $foo   would  return  an	array.	 Note  that  with  the	option
	      KSH_ARRAYS $foo always returns a scalar (regardless of  the  use
	      of  the  offset syntax) and a form such as $foo[*]:3 is required
	      to extract elements of an array named foo.

	      If offset is negative, the - may not  appear  immediately	 after
	      the  : as this indicates the ${name:-word} form of substitution.
	      Instead, a space may be inserted	before	the  -.	  Furthermore,
	      neither offset nor length may begin with an alphabetic character
	      or & as these are used to indicate history-style modifiers.   To
	      substitute  a value from a variable, the recommended approach is
	      to precede it with a $ as this signifies the intention  (parame‐
	      ter substitution can easily be rendered unreadable); however, as
	      arithmetic substitution  is  performed,  the  expression	${var:
	      offs} does work, retrieving the offset from $offs.

	      For  further  compatibility with other shells there is a special
	      case for array offset 0.	This usually  accesses	to  the	 first
	      element  of  the array.  However, if the substitution refers the
	      positional parameter array, e.g. $@ or $*, then offset 0 instead
	      refers to $0, offset 1 refers to $1, and so on.  In other words,
	      the  positional  parameter  array	 is  effectively  extended  by
	      prepending  $0.  Hence ${*:0:1} substitutes $0 and ${*:1:1} sub‐
	      stitutes $1.

       ${name/pattern/repl}
       ${name//pattern/repl}
	      Replace the longest possible match of pattern in	the  expansion
	      of  parameter name by string repl.  The first form replaces just
	      the first occurrence, the second	form  all  occurrences.	  Both
	      pattern  and  repl are subject to double-quoted substitution, so
	      that expressions like ${name/$opat/$npat} will  work,  but  note
	      the  usual rule that pattern characters in $opat are not treated
	      specially unless either the option GLOB_SUBST is set,  or	 $opat
	      is instead substituted as ${~opat}.

	      The pattern may begin with a `#', in which case the pattern must
	      match at the start of the string, or `%', in which case it  must
	      match  at	 the end of the string, or `#%' in which case the pat‐
	      tern must match the entire string.  The repl  may	 be  an	 empty
	      string,  in  which  case	the final `/' may also be omitted.  To
	      quote the final `/' in other cases it should be  preceded	 by  a
	      single backslash; this is not necessary if the `/' occurs inside
	      a substituted parameter.	Note also that the `#',	 `%'  and  `#%
	      are  not	active	if  they occur inside a substituted parameter,
	      even at the start.

	      The first `/' may be preceded by a `:', in which case the	 match
	      will  only succeed if it matches the entire word.	 Note also the
	      effect of the I and S parameter expansion flags below;  however,
	      the flags M, R, B, E and N are not useful.

	      For example,

		     foo="twinkle twinkle little star" sub="t*e" rep="spy"
		     print ${foo//${~sub}/$rep}
		     print ${(S)foo//${~sub}/$rep}

	      Here, the `~' ensures that the text of $sub is treated as a pat‐
	      tern rather than a plain string.	In the first case, the longest
	      match for t*e is substituted and the result is `spy star', while
	      in the second case, the  shortest	 matches  are  taken  and  the
	      result is `spy spy lispy star'.

       ${#spec}
	      If spec is one of the above substitutions, substitute the length
	      in characters of the result instead of the  result  itself.   If
	      spec  is	an array expression, substitute the number of elements
	      of the result.  This has the side-effect that joining is skipped
	      even  in quoted forms, which may affect other sub-expressions in
	      spec.  Note that `^', `=', and `~', below, must  appear  to  the
	      left of `#' when these forms are combined.

       ${^spec}
	      Turn  on	the RC_EXPAND_PARAM option for the evaluation of spec;
	      if the `^' is doubled, turn it off.  When this  option  is  set,
	      array expansions of the form foo${xx}bar, where the parameter xx
	      is set to	 (a  b	c),  are  substituted  with  `fooabar  foobbar
	      foocbar'	instead	 of  the  default `fooa b cbar'.  Note that an
	      empty array will therefore cause all arguments to be removed.

	      Internally, each such expansion is converted into the equivalent
	      list    for    brace    expansion.     E.g.,   ${^var}   becomes
	      {$var[1],$var[2],...}, and is processed as described in the sec‐
	      tion  `Brace  Expansion'	below.	 If  word splitting is also in
	      effect the $var[N] may themselves be split into  different  list
	      elements.

       ${=spec}
	      Perform  word splitting using the rules for SH_WORD_SPLIT during
	      the evaluation of spec, but regardless of whether the  parameter
	      appears  in  double  quotes; if the `=' is doubled, turn it off.
	      This forces parameter expansions to be split into separate words
	      before  substitution, using IFS as a delimiter.  This is done by
	      default in most other shells.

	      Note that splitting is applied to word in the  assignment	 forms
	      of  spec	before	the  assignment	 to  name  is performed.  This
	      affects the result of array assignments with the A flag.

       ${~spec}
	      Turn on the GLOB_SUBST option for the evaluation of spec; if the
	      `~'  is  doubled,	 turn  it  off.	  When this option is set, the
	      string resulting from the expansion will	be  interpreted	 as  a
	      pattern anywhere that is possible, such as in filename expansion
	      and filename generation and pattern-matching contexts  like  the
	      right hand side of the `=' and `!=' operators in conditions.

	      In  nested  substitutions, note that the effect of the ~ applies
	      to the result of the current level of substitution.  A surround‐
	      ing  pattern  operation on the result may cancel it.  Hence, for
	      example, if the parameter foo is set to  *,  ${~foo//\*/*.c}  is
	      substituted  by  the pattern *.c, which may be expanded by file‐
	      name  generation,	 but  ${${~foo}//\*/*.c}  substitutes  to  the
	      string *.c, which will not be further expanded.

       If  a ${...} type parameter expression or a $(...) type command substi‐
       tution is used in place of name above, it is  expanded  first  and  the
       result is used as if it were the value of name.	Thus it is possible to
       perform nested operations:  ${${foo#head}%tail} substitutes  the	 value
       of  $foo	 with both `head' and `tail' deleted.  The form with $(...) is
       often useful in combination with the  flags  described  next;  see  the
       examples	 below.	  Each	name or nested ${...} in a parameter expansion
       may also be followed by a subscript expression as  described  in	 Array
       Parameters in zshparam(1).

       Note  that double quotes may appear around nested expressions, in which
       case  only  the	part  inside  is  treated  as  quoted;	for   example,
       ${(f)"$(foo)"}  quotes  the  result  of $(foo), but the flag `(f)' (see
       below) is applied using the rules for unquoted expansions.   Note  fur‐
       ther that quotes are themselves nested in this context; for example, in
       "${(@f)"$(foo)"}", there are two sets of quotes,	 one  surrounding  the
       whole  expression,  the	other  (redundant)  surrounding	 the $(foo) as
       before.

   Parameter Expansion Flags
       If the opening brace is directly followed by  an	 opening  parenthesis,
       the  string  up	to the matching closing parenthesis will be taken as a
       list of flags.  In cases where repeating a flag is meaningful, the rep‐
       etitions need not be consecutive; for example, `(q%q%q)' means the same
       thing as the more readable `(%%qqq)'.  The  following  flags  are  sup‐
       ported:

       #      Evaluate	the  resulting words as numeric expressions and output
	      the characters corresponding to  the  resulting  integer.	  Note
	      that  this  form	is entirely distinct from use of the # without
	      parentheses.

	      If the MULTIBYTE option is set and the number  is	 greater  than
	      127  (i.e.  not  an  ASCII character) it is treated as a Unicode
	      character.

       %      Expand all % escapes in the resulting words in the same  way  as
	      in prompts (see EXPANSION OF PROMPT SEQUENCES in zshmisc(1)). If
	      this flag is given twice, full prompt expansion is done  on  the
	      resulting words, depending on the setting of the PROMPT_PERCENT,
	      PROMPT_SUBST and PROMPT_BANG options.

       @      In double quotes, array elements are put	into  separate	words.
	      E.g.,   `"${(@)foo}"'   is   equivalent	to  `"${foo[@]}"'  and
	      `"${(@)foo[1,2]}"' is the same as `"$foo[1]"  "$foo[2]"'.	  This
	      is  distinct  from field splitting by the f, s or z flags, which
	      still applies within each array element.

       A      Create an array parameter with  `${...=...}',  `${...:=...}'  or
	      `${...::=...}'.	If  this flag is repeated (as in `AA'), create
	      an associative array parameter.  Assignment is made before sort‐
	      ing  or  padding; if field splitting is active, the word part is
	      split before assignment.	The name part  may  be	a  subscripted
	      range for ordinary arrays; the word part must be converted to an
	      array, for example by using `${(AA)=name=...}' to activate field
	      splitting, when creating an associative array.

       a      Sort  in	array  index  order;  when  combined  with `O' sort in
	      reverse array index order.  Note that `a' is  therefore  equiva‐
	      lent  to the default but `Oa' is useful for obtaining an array's
	      elements in reverse order.

       c      With ${#name}, count the total number of characters in an array,
	      as  if  the elements were concatenated with spaces between them.
	      This is not a true join of the array, so other expressions  used
	      with  this  flag may have an effect on the elements of the array
	      before it is counted.

       C      Capitalize the resulting words.  `Words' in this case refers  to
	      sequences	 of  alphanumeric characters separated by non-alphanu‐
	      merics, not to words that result from field splitting.

       D      Assume the string or  array  elements  contain  directories  and
	      attempt  to  substitute the leading part of these by names.  The
	      remainder of the path (the whole of it if the leading  part  was
	      not  subsituted)	is then quoted so that the whole string can be
	      used as a shell argument.	 This is the reverse of `~'  substitu‐
	      tion:  see the section FILENAME EXPANSION below.

       e      Perform parameter expansion, command substitution and arithmetic
	      expansion on the result. Such expansions can be nested  but  too
	      deep recursion may have unpredictable effects.

       f      Split  the result of the expansion at newlines. This is a short‐
	      hand for `ps:\n:'.

       F      Join the words of arrays together using newline as a  separator.
	      This is a shorthand for `pj:\n:'.

       g:opts:
	      Process  escape  sequences like the echo builtin when no options
	      are given (g::).	With the o option, octal escapes don't take  a
	      leading  zero.   With the c option, sequences like `^X' are also
	      processed.  With the e  option,  processes  `\M-t'  and  similar
	      sequences	 like  the  print  builtin.   With both of the o and e
	      options, behaves like the print builtin except that in  none  of
	      these modes is `\c' interpreted.

       i      Sort case-insensitively.	May be combined with `n' or `O'.

       k      If  name	refers	to  an	associative array, substitute the keys
	      (element names) rather than the values of	 the  elements.	  Used
	      with  subscripts	(including  ordinary arrays), force indices or
	      keys to be substituted even if the subscript form refers to val‐
	      ues.   However,  this  flag  may	not be combined with subscript
	      ranges.

       L      Convert all letters in the result to lower case.

       n      Sort decimal integers numerically; if the first differing	 char‐
	      acters  of  two test strings are not digits, sorting is lexical.
	      Integers with more initial zeroes are sorted before  those  with
	      fewer  or	 none.	 Hence	the  array `foo1 foo02 foo2 foo3 foo20
	      foo23' is sorted into the order shown.  May be combined with `i'
	      or `O'.

       o      Sort  the resulting words in ascending order; if this appears on
	      its own the sorting is lexical and  case-sensitive  (unless  the
	      locale renders it case-insensitive).  Sorting in ascending order
	      is the default for other forms of sorting, so this is ignored if
	      combined with `a', `i' or `n'.

       O      Sort  the	 resulting words in descending order; `O' without `a',
	      `i' or `n' sorts in reverse lexical order.  May be combined with
	      `a', `i' or `n' to reverse the order of sorting.

       P      This forces the value of the parameter name to be interpreted as
	      a further parameter name, whose value will be used where	appro‐
	      priate.	Note  that flags set with one of the typeset family of
	      commands (in particular case transformations) are not applied to
	      the value of name used in this fashion.

	      If  used	with  a	 nested parameter or command substitution, the
	      result of that will be taken as a parameter  name	 in  the  same
	      way.   For  example,  if	you  have `foo=bar' and `bar=baz', the
	      strings ${(P)foo}, ${(P)${foo}}, and ${(P)$(echo bar)}  will  be
	      expanded to `baz'.

       q      Quote  characters that are special to the shell in the resulting
	      words with backslashes; unprintable or  invalid  characters  are
	      quoted  using  the  $'\NNN'  form, with separate quotes for each
	      octet.

	      If this flag is given twice, the resulting words are  quoted  in
	      single  quotes  and  if  it  is given three times, the words are
	      quoted in double quotes; in these forms no special  handling  of
	      unprintable  or invalid characters is attempted.	If the flag is
	      given four times, the words are quoted in single quotes preceded
	      by  a  $.	 Note that in all three of these forms quoting is done
	      unconditionally, even if	this  does  not	 change	 the  way  the
	      resulting string would be interpreted by the shell.

	      If a q- is given (only a single q may appear), a minimal form of
	      single quoting is used that only quotes the string if needed  to
	      protect  special characters.  Typically this form gives the most
	      readable output.

       Q      Remove one level of quotes from the resulting words.

       t      Use a string describing the type	of  the	 parameter  where  the
	      value  of	 the  parameter would usually appear. This string con‐
	      sists of keywords separated by hyphens (`-'). The first  keyword
	      in  the  string  describes  the  main  type,  it	can  be one of
	      `scalar', `array',  `integer',  `float'  or  `association'.  The
	      other keywords describe the type in more detail:

	      local  for local parameters

	      left   for left justified parameters

	      right_blanks
		     for right justified parameters with leading blanks

	      right_zeros
		     for right justified parameters with leading zeros

	      lower  for parameters whose value is converted to all lower case
		     when it is expanded

	      upper  for parameters whose value is converted to all upper case
		     when it is expanded

	      readonly
		     for readonly parameters

	      tag    for tagged parameters

	      export for exported parameters

	      unique for arrays which keep only the first occurrence of dupli‐
		     cated values

	      hide   for parameters with the `hide' flag

	      special
		     for special parameters defined by the shell

       u      Expand only the first occurrence of each unique word.

       U      Convert all letters in the result to upper case.

       v      Used with k, substitute (as two consecutive words) both the  key
	      and the value of each associative array element.	Used with sub‐
	      scripts, force values to be substituted even  if	the  subscript
	      form refers to indices or keys.

       V      Make any special characters in the resulting words visible.

       w      With  ${#name}, count words in arrays or strings; the s flag may
	      be used to set a word delimiter.

       W      Similar to w  with  the  difference  that	 empty	words  between
	      repeated delimiters are also counted.

       X      With  this  flag,	 parsing  errors occurring with the Q, e and #
	      flags or the pattern matching forms  such	 as  `${name#pattern}'
	      are reported.  Without the flag, errors are silently ignored.

       z      Split the result of the expansion into words using shell parsing
	      to find the words, i.e. taking into account any quoting  in  the
	      value.   Comments	 are  not  treated  specially  but as ordinary
	      strings, similar to interactive shells with the INTERACTIVE_COM‐
	      MENTS  option  unset  (however, see the Z flag below for related
	      options)

	      Note that this is done very late,	 even  later  than  the	 `(s)'
	      flag.  So to access single words in the result use nested expan‐
	      sions as in `${${(z)foo}[2]}'. Likewise, to remove the quotes in
	      the resulting words use `${(Q)${(z)foo}}'.

       0      Split  the  result  of  the  expansion on null bytes.  This is a
	      shorthand for `ps:\0:'.

       The following flags (except p) are followed by one or more arguments as
       shown.  Any character, or the matching pairs `(...)', `{...}', `[...]',
       or `<...>', may be used in place of a colon  as	delimiters,  but  note
       that when a flag takes more than one argument, a matched pair of delim‐
       iters must surround each argument.

       p      Recognize the same escape sequences  as  the  print  builtin  in
	      string arguments to any of the flags described below that follow
	      this argument.

       ~      Force string arguments to any of the  flags  below  that	follow
	      within  the parentheses to be treated as patterns.  Compare with
	      a ~ outside parentheses, which  forces  the  entire  substituted
	      string to be treated as a pattern.  Hence, for example,
	      [[ "?" = ${(~j.|.)array} ]]
       with  the  EXTENDED_GLOB option set succeeds if and only if $array con‐
       tains the string `?' as an element.  The argument may  be  repeated  to
       toggle the behaviour; its effect only lasts to the end of the parenthe‐
       sised group.

       j:string:
	      Join the words of arrays together using string as	 a  separator.
	      Note  that  this	occurs before field splitting by the s:string:
	      flag or the SH_WORD_SPLIT option.

       l:expr::string1::string2:
	      Pad the resulting words on the left.  Each word  will  be	 trun‐
	      cated if required and placed in a field expr characters wide.

	      The arguments :string1: and :string2: are optional; neither, the
	      first, or both may be given.  Note that the same pairs of delim‐
	      iters  must  be used for each of the three arguments.  The space
	      to the left will be filled with string1 (concatenated  as	 often
	      as  needed)  or spaces if string1 is not given.  If both string1
	      and string2 are given, string2 is inserted once directly to  the
	      left  of	each  word,  truncated if necessary, before string1 is
	      used to produce any remaining padding.

	      If the MULTIBYTE option is in effect, the flag  m	 may  also  be
	      given,  in which case widths will be used for the calculation of
	      padding; otherwise individual multibyte characters  are  treated
	      as occupying one unit of width.

	      If  the  MULTIBYTE  option  is  not  in effect, each byte in the
	      string is treated as occupying one unit of width.

	      Control characters are always assumed to be one unit wide;  this
	      allows  the  mechanism  to be used for generating repetitions of
	      control characters.

       m      Only useful together with one of the flags l or r or with the  #
	      length operator when the MULTIBYTE option is in effect.  Use the
	      character width reported by the system in calculating  how  much
	      of  the  string it occupies or the overall length of the string.
	      Most printable characters have a width of one unit, however cer‐
	      tain  Asian character sets and certain special effects use wider
	      characters; combining characters have zero width.	 Non-printable
	      characters are arbitrarily counted as zero width; how they would
	      actually be displayed will vary.

	      If the m is repeated, the character either counts	 zero  (if  it
	      has zero width), else one.  For printable character strings this
	      has the effect of counting the number of glyphs  (visibly	 sepa‐
	      rate characters), except for the case where combining characters
	      themselves have non-zero width (true in certain alphabets).

       r:expr::string1::string2:
	      As l, but pad the words on the right and insert string2  immedi‐
	      ately to the right of the string to be padded.

	      Left  and	 right padding may be used together.  In this case the
	      strategy is to apply left padding to the	first  half  width  of
	      each  of	the  resulting	words, and right padding to the second
	      half.  If the string to be padded has odd width the  extra  pad‐
	      ding is applied on the left.

       s:string:
	      Force  field  splitting  at  the	separator string.  Note that a
	      string of two or more characters means that  all	of  them  must
	      match  in	 sequence;  this  differs from the treatment of two or
	      more characters in the IFS parameter.  See also the =  flag  and
	      the  SH_WORD_SPLIT option.  An empty string may also be given in
	      which case every character will be a separate element.

	      For historical reasons, the usual	 behaviour  that  empty	 array
	      elements	are  retained  inside  double  quotes  is disabled for
	      arrays generated by splitting; hence the following:

		     line="one::three"
		     print -l "${(s.:.)line}"

	      produces two lines of output for one and three  and  elides  the
	      empty  field.  To override this behaviour, supply the "(@)" flag
	      as well, i.e.  "${(@s.:.)line}".

       Z:opts:
	      As z but takes a combination of option letters between a follow‐
	      ing pair of delimiter characters.	 With no options the effect is
	      identical to z.  (Z+c+) causes comments to be parsed as a string
	      and retained; any field in the resulting array beginning with an
	      unquoted comment character is a comment.	(Z+C+) causes comments
	      to  be  parsed  and removed.  The rule for comments is standard:
	      anything between a word starting with  the  third	 character  of
	      $HISTCHARS,  default  #,	up  to	the next newline is a comment.
	      (Z+n+) causes unquoted newlines to be treated as ordinary white‐
	      space,  else  they  are treated as if they are shell code delim‐
	      iters and converted to semicolons.  Options are combined	within
	      the same set of delimiters, e.g. (Z+Cn+).

       _:flags:
	      The  underscore (_) flag is reserved for future use.  As of this
	      revision of zsh, there are no valid flags; anything following an
	      underscore,  other  than an empty pair of delimiters, is treated
	      as an error, and the flag itself has no effect.

       The following flags are meaningful with the  ${...#...}	or  ${...%...}
       forms.  The S and I flags may also be used with the ${.../...} forms.

       S      Search  substrings  as  well as beginnings or ends; with # start
	      from the beginning and with % start from the end of the  string.
	      With  substitution  via  ${.../...}  or  ${...//...},  specifies
	      non-greedy matching, i.e. that the shortest instead of the long‐
	      est match should be replaced.

       I:expr:
	      Search  the  exprth  match  (where  expr evaluates to a number).
	      This only applies when searching for substrings, either with the
	      S	 flag,	or  with  ${.../...} (only the exprth match is substi‐
	      tuted) or ${...//...} (all matches from the exprth on  are  sub‐
	      stituted).  The default is to take the first match.

	      The  exprth  match  is  counted such that there is either one or
	      zero matches from each starting position in the string, although
	      for  global  substitution	 matches overlapping previous replace‐
	      ments are ignored.  With the ${...%...} and  ${...%%...}	forms,
	      the starting position for the match moves backwards from the end
	      as the index increases, while with the other forms it moves for‐
	      ward from the start.

	      Hence with the string
		     which switch is the right switch for Ipswich?
	      substitutions  of	 the form ${(SI:N:)string#w*ch} as N increases
	      from 1 will match	 and  remove  `which',	`witch',  `witch'  and
	      `wich';  the form using `##' will match and remove `which switch
	      is the right switch for Ipswich', `witch is the right switch for
	      Ipswich',	 `witch	 for  Ipswich'	and `wich'. The form using `%'
	      will remove the same matches as for `#', but in  reverse	order,
	      and the form using `%%' will remove the same matches as for `##'
	      in reverse order.

       B      Include the index of the beginning of the match in the result.

       E      Include the index of the end of the match in the result.

       M      Include the matched portion in the result.

       N      Include the length of the match in the result.

       R      Include the unmatched portion in the result (the Rest).

   Rules
       Here is a summary of the rules  for  substitution;  this	 assumes  that
       braces are present around the substitution, i.e. ${...}.	 Some particu‐
       lar examples are given below.  Note  that  the  Zsh  Development	 Group
       accepts	no  responsibility for any brain damage which may occur during
       the reading of the following rules.

       1. Nested substitution
	      If multiple nested ${...} forms  are  present,  substitution  is
	      performed	 from the inside outwards.  At each level, the substi‐
	      tution takes account of whether the current value is a scalar or
	      an  array,  whether  the whole substitution is in double quotes,
	      and what flags are supplied to the current  level	 of  substitu‐
	      tion,  just  as  if  the nested substitution were the outermost.
	      The flags are not propagated up to enclosing substitutions;  the
	      nested  substitution  will return either a scalar or an array as
	      determined by the flags, possibly adjusted for quoting.  All the
	      following	 steps	take  place  where applicable at all levels of
	      substitution.  Note that, unless the `(P)' flag is present,  the
	      flags  and  any  subscripts  apply  directly to the value of the
	      nested  substitution;  for  example,  the	 expansion   ${${foo}}
	      behaves exactly the same as ${foo}.

	      At  each	nested	level  of  substitution, the substituted words
	      undergo all forms of single-word substitution (i.e. not filename
	      generation),  including  command substitution, arithmetic expan‐
	      sion and filename expansion (i.e. leading ~ and =).   Thus,  for
	      example,	${${:-=cat}:h}	expands to the directory where the cat
	      program resides.	(Explanation: the internal substitution has no
	      parameter	 but  a default value =cat, which is expanded by file‐
	      name expansion to a  full	 path;	the  outer  substitution  then
	      applies  the  modifier  :h  and  takes the directory part of the
	      path.)

       2. Internal parameter flags
	      Any parameter flags set by one of the  typeset  family  of  com‐
	      mands,  in particular the L, R, Z, u and l flags for padding and
	      capitalization, are applied directly  to	the  parameter	value.
	      Note  these flags are options to the command, e.g. `typeset -Z';
	      they are not the same as the flags used within parameter substi‐
	      tutions.

       3. Parameter subscripting
	      If the value is a raw parameter reference with a subscript, such
	      as ${var[3]}, the effect of subscripting is applied directly  to
	      the  parameter.	Subscripts are evaluated left to right; subse‐
	      quent subscripts apply to the scalar or array value  yielded  by
	      the  previous  subscript.	 Thus if var is an array, ${var[1][2]}
	      is the second character of the first word, but ${var[2,4][2]} is
	      the entire third word (the second word of the range of words two
	      through four of the original array).  Any number	of  subscripts
	      may appear.  Flags such as (k) and (v) which alter the result of
	      subscripting are applied.

       4. Parameter name replacement
	      The effect of any (P) flag, which treats the value so far	 as  a
	      parameter	 name and replaces it with the corresponding value, is
	      applied.

       5. Double-quoted joining
	      If the value after this process is an array, and	the  substitu‐
	      tion  appears  in double quotes, and neither an (@) flag nor a #
	      length operator is present at the current level, then  words  of
	      the  value  are joined with the first character of the parameter
	      $IFS, by default a space, between each word (single word	arrays
	      are not modified).  If the (j) flag is present, that is used for
	      joining instead of $IFS.

       6. Nested subscripting
	      Any remaining subscripts (i.e. of	 a  nested  substitution)  are
	      evaluated	 at this point, based on whether the value is an array
	      or a scalar.  As with 3., multiple subscripts can appear.	  Note
	      that  ${foo[2,4][2]} is thus equivalent to ${${foo[2,4]}[2]} and
	      also to "${${(@)foo[2,4]}[2]}" (the nested substitution  returns
	      an  array	 in  both  cases), but not to "${${foo[2,4]}[2]}" (the
	      nested substitution returns a scalar because of the quotes).

       7. Modifiers
	      Any modifiers, as specified by a trailing `#', `%', `/'  (possi‐
	      bly  doubled) or by a set of modifiers of the form :... (see the
	      section `Modifiers' in the  section  `History  Expansion'),  are
	      applied to the words of the value at this level.

       8. Character evaluation
	      Any  (#)	flag  is applied, evaluating the result so far numeri‐
	      cally as a character.

       9. Length
	      Any initial # modifier, i.e. in the form	${#var},  is  used  to
	      evaluate the length of the expression so far.

       10. Forced joining
	      If  the  `(j)'  flag is present, or no `(j)' flag is present but
	      the string is to be split as given by rule 11., and joining  did
	      not  take	 place	at  step 5., any words in the value are joined
	      together using the given string or the first character  of  $IFS
	      if  none.	 Note that the `(F)' flag implicitly supplies a string
	      for joining in this manner.

       11. Simple word splitting
	      If one of the `(s)' or `(f)' flags are present, or the `=' spec‐
	      ifier  was  present  (e.g. ${=var}), the word is split on occur‐
	      rences of the specified string, or (for = with  neither  of  the
	      two flags present) any of the characters in $IFS.

	      If  no `(s)', `(f)' or `=' was given, but the word is not quoted
	      and the option SH_WORD_SPLIT is set, the word is split on occur‐
	      rences  of  any of the characters in $IFS.  Note this step, too,
	      takes place at all levels of a nested substitution.

       12. Case modification
	      Any case modification from one of the flags (L), (U) or  (C)  is
	      applied.

       13. Escape sequence replacement
	      First any replacements from the (g) flag are performed, then any
	      prompt-style formatting from the (%) family of flags is applied.

       14. Quote application
	      Any quoting or unquoting using (q) and (Q) and related flags  is
	      applied.

       15. Directory naming
	      Any directory name substitution using (D) flag is applied.

       16. Visibility enhancement
	      Any  modifications to make characters visible using the (V) flag
	      are applied.

       17. Lexical word splitting
	      If the '(z)' flag or one of the  forms  of  the  '(Z)'  flag  is
	      present,	the  word is split as if it were a shell command line,
	      so that quotation marks and other	 metacharacters	 are  used  to
	      decide  what constitutes a word.	Note this form of splitting is
	      entirely distinct from that described by rule 11.: it  does  not
	      use $IFS, and does not cause forced joining.

       18. Uniqueness
	      If the result is an array and the `(u)' flag was present, dupli‐
	      cate elements are removed from the array.

       19. Ordering
	      If the result is still an array and one of the  `(o)'  or	 `(O)'
	      flags was present, the array is reordered.

       20. Re-evaluation
	      Any  `(e)'  flag	is  applied  to	 the  value,  forcing it to be
	      re-examined for new parameter substitutions, but also  for  com‐
	      mand and arithmetic substitutions.

       21. Padding
	      Any padding of the value by the `(l.fill.)' or `(r.fill.)' flags
	      is applied.

       22. Semantic joining
	      In contexts where expansion semantics requires a single word  to
	      result,  all  words are rejoined with the first character of IFS
	      between.	So in `${(P)${(f)lines}}' the  value  of  ${lines}  is
	      split  at	 newlines,  but then must be joined again before the P
	      flag can be applied.

	      If a single word is not required, this rule is skipped.

       23. Empty argument removal
	      If the substitution  does	 not  appear  in  double  quotes,  any
	      resulting zero-length argument, whether from a scalar or an ele‐
	      ment of an array, is elided from the list of arguments  inserted
	      into the command line.

	      Strictly speaking, the removal happens later as the same happens
	      with other forms of substitution; the point to note here is sim‐
	      ply that it occurs after any of the above parameter operations.

   Examples
       The  flag  f  is	 useful	 to split a double-quoted substitution line by
       line.  For example, ${(f)"$(<file)"} substitutes the contents  of  file
       divided	so  that each line is an element of the resulting array.  Com‐
       pare this with the effect of $(<file) alone, which divides the file  up
       by words, or the same inside double quotes, which makes the entire con‐
       tent of the file a single string.

       The following illustrates the rules for	nested	parameter  expansions.
       Suppose that $foo contains the array (bar baz):

       "${(@)${foo}[1]}"
	      This  produces  the  result  b.	First,	the inner substitution
	      "${foo}", which has no array (@) flag, produces  a  single  word
	      result "bar baz".	 The outer substitution "${(@)...[1]}" detects
	      that this is a scalar, so that (despite the `(@)' flag) the sub‐
	      script picks the first character.

       "${${(@)foo}[1]}"
	      This produces the result `bar'.  In this case, the inner substi‐
	      tution "${(@)foo}" produces the array `(bar  baz)'.   The	 outer
	      substitution "${...[1]}" detects that this is an array and picks
	      the first word.  This is similar to the simple case "${foo[1]}".

       As an example of the rules for word splitting and joining, suppose $foo
       contains the array `(ax1 bx1)'.	Then

       ${(s/x/)foo}
	      produces the words `a', `1 b' and `1'.

       ${(j/x/s/x/)foo}
	      produces `a', `1', `b' and `1'.

       ${(s/x/)foo%%1*}
	      produces	`a'  and ` b' (note the extra space).  As substitution
	      occurs before either joining or splitting, the operation	 first
	      generates	 the  modified	array (ax bx), which is joined to give
	      "ax bx", and then split to give `a', ` b'	 and  `'.   The	 final
	      empty string will then be elided, as it is not in double quotes.

COMMAND SUBSTITUTION
       A  command  enclosed  in	 parentheses  preceded	by a dollar sign, like
       `$(...)', or quoted with grave accents, like ``...`', is replaced  with
       its  standard  output, with any trailing newlines deleted.  If the sub‐
       stitution is not enclosed in double quotes, the output is  broken  into
       words  using  the  IFS parameter.  The substitution `$(cat foo)' may be
       replaced by the equivalent but faster `$(<foo)'.	 In  either  case,  if
       the  option GLOB_SUBST is set, the output is eligible for filename gen‐
       eration.

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

BRACE EXPANSION
       A  string  of the form `foo{xx,yy,zz}bar' is expanded to the individual
       words `fooxxbar', `fooyybar' and `foozzbar'.   Left-to-right  order  is
       preserved.   This  construct  may  be  nested.  Commas may be quoted in
       order to include them literally in a word.

       An expression of the form `{n1..n2}', where n1 and n2 are integers,  is
       expanded to every number between n1 and n2 inclusive.  If either number
       begins with a zero, all the resulting numbers will be padded with lead‐
       ing  zeroes to that minimum width, but for negative numbers the - char‐
       acter is also included in the width.  If the numbers are in  decreasing
       order the resulting sequence will also be in decreasing order.

       An  expression  of  the	form  `{n1..n2..n3}', where n1, n2, and n3 are
       integers, is expanded as above, but only	 every	n3th  number  starting
       from n1 is output.  If n3 is negative the numbers are output in reverse
       order, this is slightly different from simply swapping n1 and n2 in the
       case  that  the	step n3 doesn't evenly divide the range.  Zero padding
       can be specified in any of the three  numbers,  specifying  it  in  the
       third  can  be  useful to pad for example `{-99..100..01}' which is not
       possible to specify by putting a 0 on either of the first  two  numbers
       (i.e. pad to two characters).

       If  a  brace  expression	 matches  none	of the above forms, it is left
       unchanged, unless the option  BRACE_CCL	(an  abbreviation  for	`brace
       character  class')  is  set.  In that case, it is expanded to a list of
       the individual characters between the braces sorted into the  order  of
       the characters in the ASCII character set (multibyte characters are not
       currently handled).  The syntax is similar to  a	 [...]	expression  in
       filename	 generation:  `-'  is  treated	specially to denote a range of
       characters, but `^' or `!' as the first character is treated  normally.
       For  example, `{abcdef0-9}' expands to 16 words 0 1 2 3 4 5 6 7 8 9 a b
       c d e f.

       Note that brace expansion is not part  of  filename  generation	(glob‐
       bing);  an  expression  such  as */{foo,bar} is split into two separate
       words */foo and */bar before filename generation takes place.  In  par‐
       ticular,	 note  that  this  is  liable to produce a `no match' error if
       either of the two expressions does not match; this is to be  contrasted
       with  */(foo|bar),  which  is treated as a single pattern but otherwise
       has similar effects.

       To combine brace expansion with array expansion, see the ${^spec}  form
       described in the section Parameter Expansion above.

FILENAME EXPANSION
       Each  word  is checked to see if it begins with an unquoted `~'.	 If it
       does, then the word up to a `/', or the end of the word if there is  no
       `/',  is	 checked  to  see  if it can be substituted in one of the ways
       described here.	If so, then  the  `~'  and  the	 checked  portion  are
       replaced with the appropriate substitute value.

       A `~' by itself is replaced by the value of $HOME.  A `~' followed by a
       `+' or a `-' is replaced by  current  or	 previous  working  directory,
       respectively.

       A  `~'  followed by a number is replaced by the directory at that posi‐
       tion in the directory stack.  `~0' is equivalent to `~+', and  `~1'  is
       the  top	 of  the  stack.  `~+' followed by a number is replaced by the
       directory at that position in the directory stack.  `~+0' is equivalent
       to  `~+', and `~+1' is the top of the stack.  `~-' followed by a number
       is replaced by the directory that many positions from the bottom of the
       stack.	`~-0'  is  the	bottom	of  the stack.	The PUSHD_MINUS option
       exchanges the effects of `~+' and `~-' where they  are  followed	 by  a
       number.

   Dynamic named directories
       If  the	function  zsh_directory_name  exists,  or  the	shell variable
       zsh_directory_name_functions exists and contains an array  of  function
       names,  then the functions are used to implement dynamic directory nam‐
       ing.  The functions are tried in order until one returns	 status	 zero,
       so it is important that functions test whether they can handle the case
       in question and return an appropriate status.

       A `~' followed by a  string  namstr  in	unquoted  square  brackets  is
       treated	specially  as  a  dynamic directory name.  Note that the first
       unquoted closing square bracket always terminates  namstr.   The	 shell
       function	 is  passed two arguments: the string n (for name) and namstr.
       It should either set the array reply to a single element which  is  the
       directory  corresponding	 to the name and return status zero (executing
       an assignment as the last  statement  is	 usually  sufficient),	or  it
       should return status non-zero.  In the former case the element of reply
       is used as the directory; in the latter case the substitution is deemed
       to  have	 failed.  If all functions fail and the option NOMATCH is set,
       an error results.

       The functions defined as above are also used to see if a directory  can
       be turned into a name, for example when printing the directory stack or
       when expanding %~ in prompts.  In this case each function is passed two
       arguments:  the	string d (for directory) and the candidate for dynamic
       naming.	The function should either  return  non-zero  status,  if  the
       directory  cannot  be named by the function, or it should set the array
       reply to consist of two elements: the first is the dynamic name for the
       directory (as would appear within `~[...]'), and the second is the pre‐
       fix length of the directory to be replaced.  For example, if the	 trial
       directory   is	/home/myname/src/zsh   and   the   dynamic   name  for
       /home/myname/src (which has 16 characters) is s, then the function sets

	      reply=(s 16)

       The directory name so returned is compared with possible	 static	 names
       for  parts of the directory path, as described below; it is used if the
       prefix length matched (16 in the example) is longer than	 that  matched
       by any static name.

       It  is not a requirement that a function implements both n and d calls;
       for example, it might be	 appropriate  for  certain  dynamic  forms  of
       expansion  not  to  be contracted to names.  In that case any call with
       the first argument d should cause a non-zero status to be returned.

       The completion system calls `zsh_directory_name c' followed by  equiva‐
       lent calls to elements of the array zsh_directory_name_functions, if it
       exists, in order to complete dynamic names for directories.   The  code
       for this should be as for any other completion function as described in
       zshcompsys(1).

       As a working example, here is a function that expands any dynamic names
       beginning  with	the string p: to directories below /home/pws/perforce.
       In this simple case a static name for the directory would  be  just  as
       effective.

	      zsh_directory_name() {
		emulate -L zsh
		setopt extendedglob
		local -a match mbegin mend
		if [[ $1 = d ]]; then
		  # turn the directory into a name
		  if [[ $2 = (#b)(/home/pws/perforce/)([^/]##)* ]]; then
		    typeset -ga reply
		    reply=(p:$match[2] $(( ${#match[1]} + ${#match[2]} )) )
		  else
		    return 1
		  fi
		elif [[ $1 = n ]]; then
		  # turn the name into a directory
		  [[ $2 != (#b)p:(?*) ]] && return 1
		  typeset -ga reply
		  reply=(/home/pws/perforce/$match[1])
		elif [[ $1 = c ]]; then
		  # complete names
		  local expl
		  local -a dirs
		  dirs=(/home/pws/perforce/*(/:t))
		  dirs=(p:${^dirs})
		  _wanted dynamic-dirs expl 'dynamic directory' compadd -S\] -a dirs
		  return
		else
		  return 1
		fi
		return 0
	      }

   Static named directories
       A `~' followed by anything not already covered consisting of any number
       of alphanumeric characters or underscore (`_'), hyphen  (`-'),  or  dot
       (`.')  is  looked up as a named directory, and replaced by the value of
       that named directory if found.  Named directories  are  typically  home
       directories  for	 users on the system.  They may also be defined if the
       text after the `~' is the name of a string shell parameter whose	 value
       begins with a `/'.  Note that trailing slashes will be removed from the
       path to the directory (though the original parameter is not modified).

       It is also possible to define directory names using the	-d  option  to
       the hash builtin.

       When the shell prints a path (e.g. when expanding %~ in prompts or when
       printing the directory stack), the path is checked to see if it	has  a
       named  directory	 as  its  prefix.   If	so, then the prefix portion is
       replaced with a `~' followed by the name of the directory.  The shorter
       of  the two ways of referring to the directory is used, i.e. either the
       directory name or the full path; the name is used if they are the  same
       length.	 The parameters $PWD and $OLDPWD are never abbreviated in this
       fashion.

   `=' expansion
       If a word begins with an unquoted `=' and the EQUALS option is set, the
       remainder  of the word is taken as the name of a command.  If a command
       exists by that name, the word is replaced by the full pathname  of  the
       command.

   Notes
       Filename	 expansion  is performed on the right hand side of a parameter
       assignment, including those appearing after  commands  of  the  typeset
       family.	 In  this  case,  the  right  hand  side  will be treated as a
       colon-separated list in the manner of the PATH parameter, so that a `~'
       or  an  `=' following a `:' is eligible for expansion.  All such behav‐
       iour can be disabled by quoting the `~', the `=', or the whole  expres‐
       sion (but not simply the colon); the EQUALS option is also respected.

       If  the option MAGIC_EQUAL_SUBST is set, any unquoted shell argument in
       the form `identifier=expression' becomes eligible for file expansion as
       described  in  the  previous  paragraph.	  Quoting  the	first `=' also
       inhibits this.

FILENAME GENERATION
       If a word contains an unquoted instance of one of the  characters  `*',
       `(',  `|',  `<',	 `[', or `?', it is regarded as a pattern for filename
       generation, unless the GLOB option  is  unset.	If  the	 EXTENDED_GLOB
       option is set, the `^' and `#' characters also denote a pattern; other‐
       wise they are not treated specially by the shell.

       The word is replaced with a list of sorted  filenames  that  match  the
       pattern.	  If  no  matching  pattern is found, the shell gives an error
       message, unless the NULL_GLOB option is set, in which case the word  is
       deleted;	 or unless the NOMATCH option is unset, in which case the word
       is left unchanged.

       In filename generation, the character `/' must be  matched  explicitly;
       also, a `.' must be matched explicitly at the beginning of a pattern or
       after a `/', unless the GLOB_DOTS option is set.	 No  filename  genera‐
       tion pattern matches the files `.' or `..'.  In other instances of pat‐
       tern matching, the `/' and `.' are not treated specially.

   Glob Operators
       *      Matches any string, including the null string.

       ?      Matches any character.

       [...]  Matches any of the enclosed characters.	Ranges	of  characters
	      can  be  specified by separating two characters by a `-'.	 A `-'
	      or `]' may be matched by including it as the first character  in
	      the  list.   There are also several named classes of characters,
	      in the form `[:name:]' with the following meanings.   The	 first
	      set  use the macros provided by the operating system to test for
	      the given character combinations,	 including  any	 modifications
	      due to local language settings, see ctype(3):

	      [:alnum:]
		     The character is alphanumeric

	      [:alpha:]
		     The character is alphabetic

	      [:ascii:]
		     The  character  is 7-bit, i.e. is a single-byte character
		     without the top bit set.

	      [:blank:]
		     The character is either space or tab

	      [:cntrl:]
		     The character is a control character

	      [:digit:]
		     The character is a decimal digit

	      [:graph:]
		     The character is a printable character other than	white‐
		     space

	      [:lower:]
		     The character is a lowercase letter

	      [:print:]
		     The character is printable

	      [:punct:]
		     The  character  is printable but neither alphanumeric nor
		     whitespace

	      [:space:]
		     The character is whitespace

	      [:upper:]
		     The character is an uppercase letter

	      [:xdigit:]
		     The character is a hexadecimal digit

	      Another set of named classes is handled internally by the	 shell
	      and is not sensitive to the locale:

	      [:IDENT:]
		     The  character is allowed to form part of a shell identi‐
		     fier, such as a parameter name

	      [:IFS:]
		     The character is used as an input field  separator,  i.e.
		     is contained in the IFS parameter

	      [:IFSSPACE:]
		     The  character  is	 an IFS white space character; see the
		     documentation for IFS in the zshparam(1) manual page.

	      [:WORD:]
		     The character is treated as part of a word; this test  is
		     sensitive to the value of the WORDCHARS parameter

	      Note  that the square brackets are additional to those enclosing
	      the whole set of characters, so to test for  a  single  alphanu‐
	      meric  character	you  need `[[:alnum:]]'.  Named character sets
	      can be used alongside other types, e.g. `[[:alpha:]0-9]'.

       [^...]
       [!...] Like [...], except that it matches any character which is not in
	      the given set.

       <[x]-[y]>
	      Matches  any  number  in the range x to y, inclusive.  Either of
	      the numbers may be omitted to make the range  open-ended;	 hence
	      `<->' matches any number.	 To match individual digits, the [...]
	      form is more efficient.

	      Be careful when using other wildcards adjacent  to  patterns  of
	      this  form;  for	example, <0-9>* will actually match any number
	      whatsoever at the start of the string, since  the	 `<0-9>'  will
	      match  the first digit, and the `*' will match any others.  This
	      is a trap for the unwary, but is in fact	an  inevitable	conse‐
	      quence  of  the rule that the longest possible match always suc‐
	      ceeds.  Expressions such as  `<0-9>[^[:digit:]]*'	 can  be  used
	      instead.

       (...)  Matches  the  enclosed  pattern.	This is used for grouping.  If
	      the KSH_GLOB option is set, then a `@', `*',  `+',  `?'  or  `!'
	      immediately  preceding the `(' is treated specially, as detailed
	      below. The option SH_GLOB prevents bare parentheses  from	 being
	      used in this way, though the KSH_GLOB option is still available.

	      Note  that  grouping cannot extend over multiple directories: it
	      is an error to have a `/' within a group (this only applies  for
	      patterns	used in filename generation).  There is one exception:
	      a group of the form (pat/)# appearing as a complete path segment
	      can match a sequence of directories.  For example, foo/(a*/)#bar
	      matches foo/bar, foo/any/bar, foo/any/anyother/bar, and so on.

       x|y    Matches either x or y.  This operator has lower precedence  than
	      any  other.   The	 `|'  character must be within parentheses, to
	      avoid interpretation as a pipeline.

       ^x     (Requires EXTENDED_GLOB to be set.)  Matches anything except the
	      pattern x.  This has a higher precedence than `/', so `^foo/bar'
	      will search directories in `.' except `./foo' for a  file	 named
	      `bar'.

       x~y    (Requires EXTENDED_GLOB to be set.)  Match anything that matches
	      the pattern x but does not match y.  This has  lower  precedence
	      than  any	 operator except `|', so `*/*~foo/bar' will search for
	      all files in all directories in `.'  and then exclude  `foo/bar'
	      if there was such a match.  Multiple patterns can be excluded by
	      `foo~bar~baz'.  In the exclusion pattern (y), `/'	 and  `.'  are
	      not treated specially the way they usually are in globbing.

       x#     (Requires EXTENDED_GLOB to be set.)  Matches zero or more occur‐
	      rences of the pattern x.	This  operator	has  high  precedence;
	      `12#'  is	 equivalent to `1(2#)', rather than `(12)#'.  It is an
	      error for an unquoted `#' to follow something  which  cannot  be
	      repeated;	 this includes an empty string, a pattern already fol‐
	      lowed by `##', or parentheses when part of  a  KSH_GLOB  pattern
	      (for  example,  `!(foo)#'	 is  invalid  and  must be replaced by
	      `*(!(foo))').

       x##    (Requires EXTENDED_GLOB to be set.)  Matches one or more	occur‐
	      rences  of  the  pattern	x.  This operator has high precedence;
	      `12##' is equivalent to `1(2##)', rather than `(12)##'.  No more
	      than  two	 active `#' characters may appear together.  (Note the
	      potential clash with glob qualifiers in the form `1(2##)'	 which
	      should therefore be avoided.)

   ksh-like Glob Operators
       If  the KSH_GLOB option is set, the effects of parentheses can be modi‐
       fied by a preceding `@', `*', `+', `?' or `!'.  This character need not
       be unquoted to have special effects, but the `(' must be.

       @(...) Match the pattern in the parentheses.  (Like `(...)'.)

       *(...) Match  any  number  of occurrences.  (Like `(...)#', except that
	      recursive directory searching is not supported.)

       +(...) Match at least one occurrence.   (Like  `(...)##',  except  that
	      recursive directory searching is not supported..)

       ?(...) Match zero or one occurrence.  (Like `(|...)'.)

       !(...) Match   anything	but  the  expression  in  parentheses.	 (Like
	      `(^(...))'.)

   Precedence
       The precedence of the operators given above is (highest) `^', `/', `~',
       `|'  (lowest);  the remaining operators are simply treated from left to
       right as part of a string, with `#' and `##' applying to	 the  shortest
       possible	 preceding unit (i.e. a character, `?', `[...]', `<...>', or a
       parenthesised expression).  As mentioned above, a `/' used as a	direc‐
       tory  separator	may not appear inside parentheses, while a `|' must do
       so; in patterns used in other contexts than  filename  generation  (for
       example,	 in  case statements and tests within `[[...]]'), a `/' is not
       special; and `/' is also not special  after  a  `~'  appearing  outside
       parentheses in a filename pattern.

   Globbing Flags
       There  are various flags which affect any text to their right up to the
       end of the enclosing group or to the end of the pattern;	 they  require
       the  EXTENDED_GLOB  option. All take the form (#X) where X may have one
       of the following forms:

       i      Case insensitive:	 upper or lower case characters in the pattern
	      match upper or lower case characters.

       l      Lower  case  characters in the pattern match upper or lower case
	      characters; upper case characters	 in  the  pattern  still  only
	      match upper case characters.

       I      Case  sensitive:	locally negates the effect of i or l from that
	      point on.

       b      Activate backreferences for parenthesised groups in the pattern;
	      this  does not work in filename generation.  When a pattern with
	      a set of active parentheses is matched, the strings  matched  by
	      the  groups  are	stored in the array $match, the indices of the
	      beginning of the matched parentheses in the array	 $mbegin,  and
	      the  indices  of the end in the array $mend, with the first ele‐
	      ment of each array  corresponding	 to  the  first	 parenthesised
	      group, and so on.	 These arrays are not otherwise special to the
	      shell.  The indices use the same convention  as  does  parameter
	      substitution,  so that elements of $mend and $mbegin may be used
	      in subscripts; the KSH_ARRAYS  option  is	 respected.   Sets  of
	      globbing flags are not considered parenthesised groups; only the
	      first nine active parentheses can be referenced.

	      For example,

		     foo="a string with a message"
		     if [[ $foo = (a|an)' '(#b)(*)' '* ]]; then
		       print ${foo[$mbegin[1],$mend[1]]}
		     fi

	      prints `string with a'.  Note  that  the	first  parenthesis  is
	      before the (#b) and does not create a backreference.

	      Backreferences  work  with  all  forms of pattern matching other
	      than filename generation, but note that when performing  matches
	      on  an  entire array, such as ${array#pattern}, or a global sub‐
	      stitution, such as ${param//pat/repl}, only  the	data  for  the
	      last  match  remains  available.	In the case of global replace‐
	      ments this may still be useful.  See the example for the m  flag
	      below.

	      The  numbering  of  backreferences strictly follows the order of
	      the opening parentheses  from  left  to  right  in  the  pattern
	      string,  although	 sets of parentheses may be nested.  There are
	      special rules for parentheses followed by `#' or `##'.  Only the
	      last match of the parenthesis is remembered: for example, in `[[
	      abab =  (#b)([ab])#  ]]',	 only  the  final  `b'	is  stored  in
	      match[1].	  Thus extra parentheses may be necessary to match the
	      complete segment: for example, use  `X((ab|cd)#)Y'  to  match  a
	      whole  string  of either `ab' or `cd' between `X' and `Y', using
	      the value of $match[1] rather than $match[2].

	      If the match fails none of the parameters is altered, so in some
	      cases  it	 may  be  necessary to initialise them beforehand.  If
	      some of the backreferences fail to match	--  which  happens  if
	      they are in an alternate branch which fails to match, or if they
	      are followed by # and matched zero times	--  then  the  matched
	      string is set to the empty string, and the start and end indices
	      are set to -1.

	      Pattern matching with backreferences  is	slightly  slower  than
	      without.

       B      Deactivate  backreferences,  negating  the  effect of the b flag
	      from that point on.

       cN,M   The flag (#cN,M) can be used anywhere that the # or ## operators
	      can  be  used  except in the expressions `(*/)#' and `(*/)##' in
	      filename generation, where `/' has special meaning; it cannot be
	      combined	with  other  globbing  flags  and  a bad pattern error
	      occurs if it is misplaced.  It is equivalent to the  form	 {N,M}
	      in  regular  expressions.	  The  previous	 character or group is
	      required to match between N and M times,	inclusive.   The  form
	      (#cN) requires exactly N matches; (#c,M) is equivalent to speci‐
	      fying N as 0; (#cN,) specifies that there is no maximum limit on
	      the number of matches.

       m      Set  references to the match data for the entire string matched;
	      this is similar to backreferencing and does not work in filename
	      generation.   The	 flag must be in effect at the end of the pat‐
	      tern, i.e. not local to a group. The parameters $MATCH,  $MBEGIN
	      and  $MEND  will be set to the string matched and to the indices
	      of the beginning and end of the string, respectively.   This  is
	      most  useful in parameter substitutions, as otherwise the string
	      matched is obvious.

	      For example,

		     arr=(veldt jynx grimps waqf zho buck)
		     print ${arr//(#m)[aeiou]/${(U)MATCH}}

	      forces all the matches (i.e. all vowels) into uppercase,	print‐
	      ing `vEldt jynx grImps wAqf zhO bUck'.

	      Unlike backreferences, there is no speed penalty for using match
	      references, other than the extra substitutions required for  the
	      replacement strings in cases such as the example shown.

       M      Deactivate the m flag, hence no references to match data will be
	      created.

       anum   Approximate matching: num	 errors	 are  allowed  in  the	string
	      matched by the pattern.  The rules for this are described in the
	      next subsection.

       s, e   Unlike the other flags, these have only a local effect, and each
	      must  appear  on	its own:  `(#s)' and `(#e)' are the only valid
	      forms.  The `(#s)' flag succeeds only at the start of  the  test
	      string, and the `(#e)' flag succeeds only at the end of the test
	      string; they correspond to  `^'  and  `$'	 in  standard  regular
	      expressions.  They are useful for matching path segments in pat‐
	      terns other than those in filename generation (where  path  seg‐
	      ments  are  in  any  case	 treated  separately).	 For  example,
	      `*((#s)|/)test((#e)|/)*' matches a path segment `test' in any of
	      the   following	strings:   test,  test/at/start,  at/end/test,
	      in/test/middle.

	      Another  use  is	in   parameter	 substitution;	 for   example
	      `${array/(#s)A*Z(#e)}'  will  remove  only  elements of an array
	      which match the complete pattern `A*Z'.  There are other ways of
	      performing many operations of this type, however the combination
	      of the substitution operations `/' and `//' with the `(#s)'  and
	      `(#e)' flags provides a single simple and memorable method.

	      Note that assertions of the form `(^(#s))' also work, i.e. match
	      anywhere except at the start of the string, although this	 actu‐
	      ally  means  `anything except a zero-length portion at the start
	      of  the  string';	 you  need  to	use  `(""~(#s))'  to  match  a
	      zero-length portion of the string not at the start.

       q      A	 `q' and everything up to the closing parenthesis of the glob‐
	      bing flags are ignored by the pattern matching  code.   This  is
	      intended	to support the use of glob qualifiers, see below.  The
	      result is that the pattern `(#b)(*).c(#q.)' can be used both for
	      globbing and for matching against a string.  In the former case,
	      the `(#q.)' will be treated as a glob qualifier and  the	`(#b)'
	      will  not be useful, while in the latter case the `(#b)' is use‐
	      ful for backreferences and the `(#q.)' will  be  ignored.	  Note
	      that colon modifiers in the glob qualifiers are also not applied
	      in ordinary pattern matching.

       u      Respect the current locale in determining the presence of multi‐
	      byte  characters	in  a pattern, provided the shell was compiled
	      with MULTIBYTE_SUPPORT.  This overrides  the  MULTIBYTE  option;
	      the  default  behaviour  is  taken  from the option.  Compare U.
	      (Mnemonic: typically multibyte characters are  from  Unicode  in
	      the UTF-8 encoding, although any extension of ASCII supported by
	      the system library may be used.)

       U      All characters are considered to be a  single  byte  long.   The
	      opposite of u.  This overrides the MULTIBYTE option.

       For  example,  the  test	 string	 fooxx	can  be matched by the pattern
       (#i)FOOXX, but not by (#l)FOOXX,	 (#i)FOO(#I)XX	or  ((#i)FOOX)X.   The
       string  (#ia2)readme specifies case-insensitive matching of readme with
       up to two errors.

       When using the ksh syntax for grouping both KSH_GLOB and	 EXTENDED_GLOB
       must  be	 set  and  the left parenthesis should be preceded by @.  Note
       also that the flags do not affect letters inside [...] groups, in other
       words  (#i)[a-z]	 still	matches only lowercase letters.	 Finally, note
       that when examining whole paths case-insensitively every directory must
       be  searched  for  all files which match, so that a pattern of the form
       (#i)/foo/bar/... is potentially slow.

   Approximate Matching
       When matching approximately, the shell keeps  a	count  of  the	errors
       found,  which  cannot exceed the number specified in the (#anum) flags.
       Four types of error are recognised:

       1.     Different characters, as in fooxbar and fooybar.

       2.     Transposition of characters, as in banana and abnana.

       3.     A character missing in the target string, as  with  the  pattern
	      road and target string rod.

       4.     An extra character appearing in the target string, as with stove
	      and strove.

       Thus, the pattern (#a3)abcd matches dcba, with the errors occurring  by
       using  the first rule twice and the second once, grouping the string as
       [d][cb][a] and [a][bc][d].

       Non-literal parts of the pattern must match exactly, including  charac‐
       ters  in	 character  ranges:  hence (#a1)???  matches strings of length
       four, by applying rule 4 to an empty  part  of  the  pattern,  but  not
       strings	of  length  two, since all the ? must match.  Other characters
       which must match exactly are initial  dots  in  filenames  (unless  the
       GLOB_DOTS option is set), and all slashes in filenames, so that a/bc is
       two errors from ab/c (the slash cannot be transposed with another char‐
       acter).	 Similarly,  errors  are counted separately for non-contiguous
       strings in the pattern, so that (ab|cd)ef is two errors from aebf.

       When using exclusion  via  the  ~  operator,  approximate  matching  is
       treated entirely separately for the excluded part and must be activated
       separately.  Thus, (#a1)README~READ_ME matches READ.ME but not READ_ME,
       as  the	trailing  READ_ME  is matched without approximation.  However,
       (#a1)README~(#a1)READ_ME does not match any pattern of the form READ?ME
       as all such forms are now excluded.

       Apart  from exclusions, there is only one overall error count; however,
       the maximum errors allowed may be altered  locally,  and	 this  can  be
       delimited  by  grouping.	 For example, (#a1)cat((#a0)dog)fox allows one
       error in total, which may not occur in the dog section, and the pattern
       (#a1)cat(#a0)dog(#a1)fox	 is  equivalent.  Note that the point at which
       an error is first found is the crucial one for establishing whether  to
       use   approximation;  for  example,  (#a1)abc(#a0)xyz  will  not	 match
       abcdxyz, because the error occurs at the `x',  where  approximation  is
       turned off.

       Entire	path   segments	  may	be   matched  approximately,  so  that
       `(#a1)/foo/d/is/available/at/the/bar' allows one error in any path seg‐
       ment.   This  is	 much  less efficient than without the (#a1), however,
       since every directory in the  path  must	 be  scanned  for  a  possible
       approximate  match.   It is best to place the (#a1) after any path seg‐
       ments which are known to be correct.

   Recursive Globbing
       A pathname component of the form `(foo/)#' matches a path consisting of
       zero or more directories matching the pattern foo.

       As  a  shorthand, `**/' is equivalent to `(*/)#'; note that this there‐
       fore matches files in the current directory as well as  subdirectories.
       Thus:

	      ls (*/)#bar

       or

	      ls **/bar

       does  a	recursive  directory search for files named `bar' (potentially
       including the file `bar' in the current directory).  This form does not
       follow  symbolic links; the alternative form `***/' does, but is other‐
       wise identical.	Neither of these can be combined with other  forms  of
       globbing	 within the same path segment; in that case, the `*' operators
       revert to their usual effect.

   Glob Qualifiers
       Patterns used for filename generation may end in a list	of  qualifiers
       enclosed	 in  parentheses.  The qualifiers specify which filenames that
       otherwise match the given pattern will  be  inserted  in	 the  argument
       list.

       If the option BARE_GLOB_QUAL is set, then a trailing set of parentheses
       containing no `|' or `(' characters (or `~' if it is special) is	 taken
       as  a set of glob qualifiers.  A glob subexpression that would normally
       be taken as glob qualifiers, for example `(^x)', can be	forced	to  be
       treated	as  part  of  the glob pattern by doubling the parentheses, in
       this case producing `((^x))'.

       If the option EXTENDED_GLOB is set, a different syntax for glob	quali‐
       fiers  is  available,  namely  `(#qx)'  where x is any of the same glob
       qualifiers used in the other format.  The qualifiers must still	appear
       at  the	end  of	 the pattern.  However, with this syntax multiple glob
       qualifiers may be chained together.  They are treated as a logical  AND
       of  the	individual sets of flags.  Also, as the syntax is unambiguous,
       the expression will be treated as glob  qualifiers  just	 as  long  any
       parentheses contained within it are balanced; appearance of `|', `(' or
       `~' does not negate the effect.	Note that qualifiers  will  be	recog‐
       nised  in  this form even if a bare glob qualifier exists at the end of
       the pattern, for example `*(#q*)(.)' will recognise executable  regular
       files if both options are set; however, mixed syntax should probably be
       avoided for the sake of clarity.

       A qualifier may be any one of the following:

       /      directories

       F      `full' (i.e. non-empty) directories.   Note  that	 the  opposite
	      sense (^F) expands to empty directories and all non-directories.
	      Use (/^F) for empty directories.

       .      plain files

       @      symbolic links

       =      sockets

       p      named pipes (FIFOs)

       *      executable plain files (0100)

       %      device files (character or block special)

       %b     block special files

       %c     character special files

       r      owner-readable files (0400)

       w      owner-writable files (0200)

       x      owner-executable files (0100)

       A      group-readable files (0040)

       I      group-writable files (0020)

       E      group-executable files (0010)

       R      world-readable files (0004)

       W      world-writable files (0002)

       X      world-executable files (0001)

       s      setuid files (04000)

       S      setgid files (02000)

       t      files with the sticky bit (01000)

       fspec  files with access rights matching spec. This spec may be a octal
	      number optionally preceded by a `=', a `+', or a `-'. If none of
	      these characters is given, the behavior is the same as for  `='.
	      The octal number describes the mode bits to be expected, if com‐
	      bined with a `=', the value  given  must	match  the  file-modes
	      exactly,	with a `+', at least the bits in the given number must
	      be set in the file-modes, and with a `-', the bits in the number
	      must  not be set. Giving a `?' instead of a octal digit anywhere
	      in the  number  ensures  that  the  corresponding	 bits  in  the
	      file-modes  are  not checked, this is only useful in combination
	      with `='.

	      If the qualifier `f' is followed by any other character anything
	      up  to the next matching character (`[', `{', and `<' match `]',
	      `}', and `>' respectively, any other character  matches  itself)
	      is  taken	 as a list of comma-separated sub-specs. Each sub-spec
	      may be either an octal number as described above or  a  list  of
	      any of the characters `u', `g', `o', and `a', followed by a `=',
	      a `+', or a `-', followed by a list of  any  of  the  characters
	      `r',  `w',  `x', `s', and `t', or an octal digit. The first list
	      of characters specify which access rights are to be checked.  If
	      a	 `u'  is given, those for the owner of the file are used, if a
	      `g' is given, those of the group are checked,  a	`o'  means  to
	      test  those  of  other users, and the `a' says to test all three
	      groups. The `=', `+', and `-' again says how the modes are to be
	      checked  and  have  the  same meaning as described for the first
	      form above. The second list of  characters  finally  says	 which
	      access  rights  are to be expected: `r' for read access, `w' for
	      write access, `x' for the right  to  execute  the	 file  (or  to
	      search a directory), `s' for the setuid and setgid bits, and `t'
	      for the sticky bit.

	      Thus, `*(f70?)' gives the files for which the  owner  has	 read,
	      write, and execute permission, and for which other group members
	      have no rights, independent of the permissions for other	users.
	      The  pattern `*(f-100)' gives all files for which the owner does
	      not have execute permission,  and	 `*(f:gu+w,o-rx:)'  gives  the
	      files  for  which	 the  owner and the other members of the group
	      have at least write permission, and for which other users	 don't
	      have read or execute permission.

       estring
       +cmd   The string will be executed as shell code.  The filename will be
	      included in the list if and only if the code returns a zero sta‐
	      tus (usually the status of the last command).

	      In  the  first  form,  the first character after the `e' will be
	      used as a separator and anything up to the next matching separa‐
	      tor  will	 be taken  as the string; `[', `{', and `<' match `]',
	      `}', and `>', respectively, while any  other  character  matches
	      itself.  Note  that  expansions  must be quoted in the string to
	      prevent them  from  being	 expanded  before  globbing  is	 done.
	      string  is  then executed as shell code.	The string globqual is
	      appended to the array zsh_eval_context the  duration  of	execu‐
	      tion.

	      During  the  execution  of  string  the filename currently being
	      tested is available in the parameter REPLY; the parameter may be
	      altered  to a string to be inserted into the list instead of the
	      original filename.  In addition, the parameter reply may be  set
	      to an array or a string, which overrides the value of REPLY.  If
	      set to an array, the latter is inserted into  the	 command  line
	      word by word.

	      For   example,  suppose  a  directory  contains  a  single  file
	      `lonely'.	 Then the  expression  `*(e:'reply=(${REPLY}{1,2})':)'
	      will cause the words `lonely1' and `lonely2' to be inserted into
	      the command line.	 Note the quoting of string.

	      The form +cmd has the same  effect,  but	no  delimiters	appear
	      around  cmd.   Instead,  cmd is taken as the longest sequence of
	      characters following the + that are alphanumeric or  underscore.
	      Typically cmd will be the name of a shell function that contains
	      the appropriate test.  For example,

		     nt() { [[ $REPLY -nt $NTREF ]] }
		     NTREF=reffile
		     ls -l *(+nt)

	      lists all files in the directory that have  been	modified  more
	      recently than reffile.

       ddev   files on the device dev

       l[-|+]ct
	      files having a link count less than ct (-), greater than ct (+),
	      or equal to ct

       U      files owned by the effective user ID

       G      files owned by the effective group ID

       uid    files owned by user ID id if that is a  number.	Otherwise,  id
	      specifies a user name: the character after the `u' will be taken
	      as a separator and the string between it and the	next  matching
	      separator will be taken as a user name.  The starting separators
	      `[', `{', and `<' match the final separators `]', `}', and  `>',
	      respectively;  any other character matches itself.  The selected
	      files are those owned by this user.  For	example,  `u:foo:'  or
	      `u[foo]' selects files owned by user `foo'.

       gid    like uid but with group IDs or names

       a[Mwhms][-|+]n
	      files  accessed  exactly	n days ago.  Files accessed within the
	      last n days are selected using a	negative  value	 for  n	 (-n).
	      Files accessed more than n days ago are selected by a positive n
	      value (+n).  Optional unit specifiers `M', `w', `h', `m' or  `s'
	      (e.g.  `ah5') cause the check to be performed with months (of 30
	      days), weeks, hours, minutes or seconds instead of days, respec‐
	      tively.  An explicit `d' for days is also allowed.

	      Any  fractional  part  of the difference between the access time
	      and the current part in the appropriate units is ignored in  the
	      comparison.   For	 instance,  `echo  *(ah-5)'  would  echo files
	      accessed within the last five hours, while `echo *(ah+5)'	 would
	      echo  files  accessed  at least six hours ago, as times strictly
	      between five and six hours are treated as five hours.

       m[Mwhms][-|+]n
	      like the file access qualifier, except that  it  uses  the  file
	      modification time.

       c[Mwhms][-|+]n
	      like  the	 file  access  qualifier, except that it uses the file
	      inode change time.

       L[+|-]n
	      files less than n bytes (-), more than n bytes (+), or exactly n
	      bytes in length.

	      If  this flag is directly followed by a `k' (`K'), `m' (`M'), or
	      `p' (`P') (e.g. `Lk-50') the check is performed with  kilobytes,
	      megabytes,  or  blocks  (of  512 bytes) instead.	In this case a
	      file is regarded as "exactly" the size if the file size  rounded
	      up  to  the next unit is equal to the test size.	Hence `*(Lm1)'
	      matches files from 1 byte up to 1 Megabyte inclusive.  Note also
	      that  the	 set  of files "less than" the test size only includes
	      files that would not match the equality  test;  hence  `*(Lm-1)'
	      only matches files of zero size.

       ^      negates all qualifiers following it

       -      toggles  between	making	the  qualifiers work on symbolic links
	      (the default) and the files they point to

       M      sets the MARK_DIRS option for the current pattern

       T      appends a trailing qualifier mark to the filenames, analogous to
	      the LIST_TYPES option, for the current pattern (overrides M)

       N      sets the NULL_GLOB option for the current pattern

       D      sets the GLOB_DOTS option for the current pattern

       n      sets the NUMERIC_GLOB_SORT option for the current pattern

       oc     specifies how the names of the files should be sorted. If c is n
	      they are sorted by name (the default);  if  it  is  L  they  are
	      sorted  depending	 on  the size (length) of the files; if l they
	      are sorted by the number of links; if a, m, or c they are sorted
	      by  the  time  of the last access, modification, or inode change
	      respectively; if d, files in subdirectories appear before	 those
	      in  the current directory at each level of the search -- this is
	      best combined with other criteria, for example `odon' to sort on
	      names  for  files within the same directory; if N, no sorting is
	      performed.  Note that a, m, and c compare the  age  against  the
	      current  time,  hence the first name in the list is the youngest
	      file. Also note  that  the  modifiers  ^	and  -	are  used,  so
	      `*(^-oL)'	 gives	a  list	 of  all  files sorted by file size in
	      descending order, following any symbolic links.	Unless	oN  is
	      used, multiple order specifiers may occur to resolve ties.

	      oe  and  o+  are	special cases; they are each followed by shell
	      code, delimited as for the e glob qualifier and the + glob qual‐
	      ifier  respectively  (see above).	 The code is executed for each
	      matched file with the parameter REPLY set to  the	 name  of  the
	      file  on	entry  and globsort appended to zsh_eval_context.  The
	      code should modify the parameter	REPLY  in  some	 fashion.   On
	      return,  the  value of the parameter is used instead of the file
	      name as the string on which to sort.  Unlike other  sort	opera‐
	      tors,  oe and o+ may be repeated, but note that the maximum num‐
	      ber of sort operators of any kind that may appear	 in  any  glob
	      expression is 12.

       Oc     like  `o',  but  sorts in descending order; i.e. `*(^oc)' is the
	      same as `*(Oc)' and `*(^Oc)' is the same as `*(oc)';  `Od'  puts
	      files in the current directory before those in subdirectories at
	      each level of the search.

       [beg[,end]]
	      specifies which of the matched filenames should be  included  in
	      the  returned  list.  The	 syntax	 is the same as for array sub‐
	      scripts. beg and the optional end may  be	 mathematical  expres‐
	      sions. As in parameter subscripting they may be negative to make
	      them count from the last	match  backward.  E.g.:	 `*(-OL[1,3])'
	      gives a list of the names of the three largest files.

       Pstring
	      The  string  will	 be prepended to each glob match as a separate
	      word.  string is delimited in the same way as arguments to the e
	      glob  qualifier described above.	The qualifier can be repeated;
	      the words are prepended separately so that the resulting command
	      line contains the words in the same order they were given in the
	      list of glob qualifiers.

	      A typical use for this is to prepend an option before all occur‐
	      rences  of a file name; for example, the pattern `*(P:-f:)' pro‐
	      duces the command line arguments `-f file1 -f file2 ...'

       More than one of these lists can be combined, separated by commas.  The
       whole  list  matches  if at least one of the sublists matches (they are
       `or'ed, the qualifiers in the sublists are `and'ed).  Some  qualifiers,
       however,	 affect	 all  matches generated, independent of the sublist in
       which they are given.  These are the qualifiers	`M',  `T',  `N',  `D',
       `n', `o', `O' and the subscripts given in brackets (`[...]').

       If  a  `:' appears in a qualifier list, the remainder of the expression
       in parenthesis is interpreted as a modifier  (see  the  section	`Modi‐
       fiers'  in  the	section	 `History  Expansion').	 Each modifier must be
       introduced by a separate `:'.  Note also that the result after  modifi‐
       cation  does not have to be an existing file.  The name of any existing
       file can be followed by a modifier of  the  form	 `(:..)'  even	if  no
       actual  filename	 generation is performed, although note that the pres‐
       ence of the parentheses causes the entire expression to be subjected to
       any global pattern matching options such as NULL_GLOB. Thus:

	      ls *(-/)

       lists all directories and symbolic links that point to directories, and

	      ls *(%W)

       lists all world-writable device files in the current directory, and

	      ls *(W,X)

       lists  all  files  in  the current directory that are world-writable or
       world-executable, and

	      echo /tmp/foo*(u0^@:t)

       outputs the basename of all root-owned files beginning with the	string
       `foo' in /tmp, ignoring symlinks, and

	      ls *.*~(lex|parse).[ch](^D^l1)

       lists  all  files  having a link count of one whose names contain a dot
       (but not those starting with  a	dot,  since  GLOB_DOTS	is  explicitly
       switched off) except for lex.c, lex.h, parse.c and parse.h.

	      print b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)

       demonstrates  how  colon	 modifiers and other qualifiers may be chained
       together.  The ordinary qualifier `.' is applied first, then the	 colon
       modifiers  in order from left to right.	So if EXTENDED_GLOB is set and
       the base pattern matches the regular file builtin.pro, the  shell  will
       print `shmiltin.shmo'.

zsh 5.0.5			January 5, 2014			    ZSHEXPN(1)
[top]

List of man pages available for Manjaro

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net