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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 characters '\', ''' 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  per-
              formed  immediately  after alias expansion, preceding the set of five expan-
              sions 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  com-
       mand  line you are typing.  This simplifies spelling corrections 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 command line; history expan-
       sions 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 previous 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 previous 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, replacing the string foo with
       bar.  More precisely, the sequence '^foo^bar^' is synonymous with  '!!:s^foo^bar^',
       hence  other  modifiers (see the section '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 mech-
       anism  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 support is pro-
       vided by the fc builtin.

   Event Designators
       An event designator is a reference to a command-line entry in the history 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, newline, '='  or
              '('.   If  followed  immediately by a word designator (see the section 'Word
              Designators'), this forms a history reference with no event designator  (see
              the section 'Overview').

       !!     Refer to the previous command.  By itself, this expansion repeats the previ-
              ous 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 neces-
              sary  if  this  reference is to be followed by a modifier 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 necessary).

   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  com-
       mand).   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 modifiers 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 symbolic links.  This call is
              equivalent to a unless your system has the realpath system call (modern sys-
              tems 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 quali-
              fier 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 expan-
              sion.

       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. substi-
              tute 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  file-
              name 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 substi-
       tutions are not patterns, but character strings.  Any character can be used as  the
       delimiter  in place of '/'.  A backslash quotes the delimiter character.  The char-
       acter  '&',  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 pre-
       vious string either from the previous l or from the contextual scan string  s  from
       '!?s'.   You  can  omit the rightmost delimiter if a newline immediately 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  quali-
       fiers parameter substitution has already taken place, so parameters in the replace-
       ment string should be quoted to ensure they are replaced at the correct time.  Note
       also  that  complicated  patterns used in globbing qualifiers may need the extended
       glob qualifier notation (#q:s/.../.../) in order for the  shell  to  recognize  the
       expression  as  a glob qualifier.  Further, note that bad patterns in the substitu-
       tion 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 pattern 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...)  expres-
       sion,  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 replace-
       ment string is quoted so that the parameter is not substituted before the start  of
       filename generation.

       The  following f, F, w and W modifiers work only with parameter expansion and file-
       name 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 evaluates to n.  Any
              character can be used instead of the ':'; if '(', '[', or '{' is used as the
              opening delimiter, the closing delimiter should be ')', ']', or '}', respec-
              tively.

       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 sepa-
              rated by sep. Any character can be used instead of the ':';  opening  paren-
              theses 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 expression may  be  preceded  or
       followed  by  other strings except that, to prevent 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 subpro-
       cess of the job executing the shell command  line.   If  the  system  supports  the
       /dev/fd  mechanism, the command argument is the name of the device file correspond-
       ing 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 special 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 argument 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 substitutions have been performed.  This
       is  handled  entirely within the current 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 implementation 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, par-
       ticularly 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 subshell attempting to read from or write to the pipe will (in a  typical
       implementation, different operating systems may have different behaviour) block for
       ever and have to be killed explicitly.  In both cases, the shell actually  supplies
       the  information  using  a  pipe,  so  that  programmes  that  expect to lseek (see
       lseek(2)) on the file will not work.

       Also note that the previous example can be more compactly and  efficiently  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 substitu-
       tions in the above example.

       There is an additional problem with >(process); when this is attached to an  exter-
       nal  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 prob-
       lem  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  tempo-
       rary file.


PARAMETER EXPANSION
       The character '$' is used to introduce parameter expansions.  See zshparam(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 Genera-
       tion'.  Note that these patterns, along with the replacement text of any  substitu-
       tions,  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  expan-
       sion 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 letter,  digit,  or  under-
              score that is not to be interpreted as part of name.  In addition, more com-
              plicated forms of substitution usually require the  braces  to  be  present;
              exceptions, which only apply if the option KSH_ARRAYS is not set, are a sin-
              gle subscript 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, otherwise '0' is
              substituted.

       ${name-word}
       ${name:-word}
              If name is set, or in the second  form  is  non-null,  then  substitute  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  substitute  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,  uncon-
              ditionally  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 message 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  substitution  is  not
       quoted,  or  if the '(@)' flag or the name[@] syntax is used, matching and replace-
       ment 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 substi-
              tute 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 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 pre-
              ferred; 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: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 substitute 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 offset, a diagnostic is printed and noth-
              ing 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 char-
              acter 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 his-
              tory-style modifiers.  To substitute a value from  a  variable,  the  recom-
              mended  approach  is  to precede it with a $ as this signifies the intention
              (parameter 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} substitutes $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 dou-
              ble-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 pattern 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  substi-
              tuted 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 pattern rather
              than a plain string.  In the first case, the longest match for t*e  is  sub-
              stituted  and the result is 'spy star', while in the second case, the short-
              est matches are taken and the result is 'spy spy lispy star'.

       ${#spec}
              If spec is one of the above substitutions, substitute the length in  charac-
              ters  of  the  result  instead  of  the  result itself.  If spec is an array
              expression, substitute the number of elements of the result.  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 pro-
              cessed as described in the section 'Brace Expansion' below.  If word  split-
              ting  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  evalua-
              tion  of  spec,  but  regardless  of whether the parameter appears in double
              quotes; if the '=' is doubled, turn it off.  This  forces  parameter  expan-
              sions  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 dou-
              bled,  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 con-
              texts 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 surrounding  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  filename generation, but ${${~foo}//\*/*.c} substitutes to the
              string *.c, which will not be further expanded.

       If a ${...} type parameter expression or a $(...) type command substitution 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  $(foo),  but the flag '(f)' (see below) is applied using the rules for unquoted
       expansions.  Note further that quotes are themselves nested in  this  context;  for
       example,  in  "${(@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 repetitions need not be consecutive;  for
       example,  '(q%q%q)'  means the same thing as the more readable '(%%qqq)'.  The fol-
       lowing flags are supported:

       #      Evaluate the resulting words as numeric expressions and output  the  charac-
              ters  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
              '${...::=...}'.  If this flag is repeated (as in 'AA'), create  an  associa-
              tive  array  parameter.   Assignment is made before sorting or padding.  The
              name part may be a subscripted range for ordinary arrays; the word part must
              be  converted  to an array, for example by using '${(AA)=name=...}' to acti-
              vate 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 equivalent 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.

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

       D      Assume  the string or array elements contain directories and attempt to sub-
              stitute 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
              '~' substitution:  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 shorthand 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  sub-
              script  form  refers to values.  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 characters of  two
              test  strings  are not digits, sorting is lexical.   Integers with more ini-
              tial 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 appropriate.  Note that flags
              set with one of the typeset family of commands (in particular case transfor-
              mations) 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 consists 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 duplicated 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 subscripts, 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  delim-
              iters 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_COMMENTS option unset.

              Note that this is done very late, as for the '(s)' flag. So to access single
              words   in   the   result,   one   has   to  use  nested  expansions  as  in
              '${${(z)foo}[2]}'. Likewise, to remove the quotes in the resulting words one
              would do: '${(Q)${(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 delimiters 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 contains the
       string '?' as an element.  The argument may be repeated to  toggle  the  behaviour;
       its effect only lasts to the end of the parenthesised 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 truncated 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 delimiters 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 individ-
              ual 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 oper-
              ator  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 certain 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 separate characters), except for the
              case where combining characters themselves have non-zero width (true in cer-
              tain alphabets).

       r:expr::string1::string2:
              As  l,  but pad the words on the right and insert string2 immediately 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 padding 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 following pair of
              delimiter characters.  (Z+c+) causes comments to be parsed as a  string  and
              retained;  any  field in the resulting array beginning with an unquoted com-
              ment character is a comment.   (Z+C+)  causes  comments  to  be  parsed  and
              removed.   The rule for comments is standard: anything between a word start-
              ing with the third character of $HISTCHARS, default #, up to the  next  new-
              line  is  a comment.  (Z+n+) causes unquoted newlines to be treated as ordi-
              nary whitespace, else they are treated as if they are shell code  delimiters
              and converted to semicolons.

       _: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 longest 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  substituted)  or  ${...//...}  (all
              matches  from  the  exprth  on are substituted).  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 replacements 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
              forward 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 particular 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 substitution takes account of
              whether the current value is a scalar or an array, whether the whole substi-
              tution is in double quotes, and what flags are supplied to the current level
              of substitution, just as if the nested substitution were the outermost.  The
              flags are not propagated up to enclosing substitutions; the nested substitu-
              tion 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  expansion  and  filename expansion (i.e.
              leading ~ and =).  Thus, for example, ${${:-=cat}:h} expands to  the  direc-
              tory where the cat program resides.  (Explanation: the internal substitution
              has no parameter but a default value =cat, which  is  expanded  by  filename
              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 commands, in partic-
              ular  the L, R, Z, u and l flags for padding and capitalization, are applied
              directly to the parameter value.

       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; subsequent 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.

       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 substitution appears in
              double quotes, and no (@) flag is present at the current level, the 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 substi-
              tution 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 '#', '%', '/' (possibly 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 numerically as a char-
              acter.

       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 rules 16. or 17., 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. Case modification
              Any case modification from one of the flags (L), (U) or (C) is applied.

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

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

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

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

       16. Forced Splitting
              If one of the '(s)', '(f)' or '(z)' flags are present, or the '='  specifier
              was  present  (e.g. ${=var}), the word is split on occurrences of the speci-
              fied string, or (for = with neither of the two flags  present)  any  of  the
              characters in $IFS.

       17. Shell Word Splitting
              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 occurrences of any of  the
              characters  in  $IFS.   Note  this step, too, takes place at all levels of a
              nested substitution.

       18. Uniqueness
              If the result is an array and the '(u)' flag was present, duplicate 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 command 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 element 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 simply 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 exam-
       ple, ${(f)"$(<file)"} substitutes the contents of file divided so that each line is
       an element of the resulting array.  Compare this with the effect of $(<file) alone,
       which  divides  the file up by words, or the same inside double quotes, which makes
       the entire content 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 subscript picks the first character.

       "${${(@)foo}[1]}"
              This produces the result  'bar'.   In  this  case,  the  inner  substitution
              "${(@)foo}"   produces  the  array  '(bar  baz)'.   The  outer  substitution
              "${...[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  '$(...)',  or
       quoted with grave accents, like ''...'', is replaced with its standard output, with
       any trailing newlines deleted.  If the  substitution  is  not  enclosed  in  double
       quotes,  the output is broken into words using the IFS parameter.  The substitution
       '$(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 genera-
       tion.

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 sub-
       stitution and arithmetic expansion before it is evaluated.  See the section 'Arith-
       metic 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 leading zeroes to that minimum width, but
       for negative numbers the - character 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 char-
       acters).

       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 char-
       acters  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 (globbing); an expres-
       sion  such  as  */{foo,bar} is split into two separate words */foo and */bar before
       filename generation takes place.  In particular, note that this is liable  to  pro-
       duce 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  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  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_direc-
       tory_name_functions  exists and contains an array of function names, then the func-
       tions are used to implement dynamic directory naming.  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 prefix 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  char-
       acters) 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 equivalent calls  to
       elements  of the array zsh_directory_name_functions, if it exists, in order to com-
       plete 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 alphanu-
       meric 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.

       In certain circumstances (in prompts, for instance), when the shell prints a  path,
       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  shortest way of referring to the directory is used, with ties broken in favour
       of using a named directory, except when the directory is / itself.  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 behaviour can be disabled by quoting the '~', the '=', or the whole expression
       (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 '#'  charac-
       ters  also denote a pattern; otherwise 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 generation pattern matches the files '.' or
       '..'.  In other instances of pattern matching, the '/' and '.' are not treated spe-
       cially.

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

       ?      Matches any character.

       [...]  Matches  any of the enclosed characters.  Ranges of characters can be speci-
              fied 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 mean-
              ings.  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 whitespace

              [: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 identifier, 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 alphanumeric 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  consequence  of  the rule that the longest possible match always
              succeeds.  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 file-
              name 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 occurrences 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 followed 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 occurrences 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 modified by a pre-
       ceding '@', '*', '+', '?' or '!'.  This character need not be unquoted to have spe-
       cial effects, but the '(' must be.

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

       *(...) Match any number of occurrences.  (Like '(...)#'.)

       +(...) Match at least one occurrence.  (Like '(...)##'.)

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

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

   Precedence
       The  precedence  of the operators given above is (highest) '^', '/', '~', '|' (low-
       est); 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 directory 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 paren-
              theses 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 substitution, such as ${param//pat/repl},
              only the data for the last match remains available.  In the case  of  global
              replacements  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 backrefer-
              ences 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 specifying 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 sim-
              ilar to backreferencing and does not work in filename generation.  The  flag
              must  be in effect at the end of the pattern, 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, printing '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  stan-
              dard  regular  expressions.   They  are useful for matching path segments in
              patterns other than those in filename generation (where path segments 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  actually  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 globbing 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
              useful 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 multibyte  charac-
              ters  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 Uni-
              code 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-insensi-
       tively every directory must be searched for all files which match, so that  a  pat-
       tern 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 tar-
              get 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 characters in char-
       acter 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 character).  Sim-
       ilarly, 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/avail-
       able/at/the/bar' allows one error in any path segment.  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
       segments 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 therefore 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 otherwise 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 quali-
       fiers.  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  qualifiers  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.   How-
       ever,  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 recognised 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 combined 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  num-
              ber  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 '>' respec-
              tively, any other character matches itself) is taken as a list of comma-sep-
              arated  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,  inde-
              pendent 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 status (usually  the  status
              of the last command).

              In the first form, the first character after the 'e' will be used as a sepa-
              rator and anything up to the next matching separator 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 execution.

              During the execution of string the filename currently being tested is avail-
              able 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,
              respectively.

              Any  fractional  part of the difference between the access time and the cur-
              rent 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 com-
              bined 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 qualifier 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_con-
              text.  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 operators,  oe  and  o+  may  be
              repeated,  but  note  that  the maximum number 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 subscripts. beg and the optional
              end may be mathematical expressions. 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 occurrences  of  a
              file  name;  for  example,  the pattern '*(P:-f:)' produces 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  parenthe-
       sis  is interpreted as a modifier (see the section 'Modifiers' in the section 'His-
       tory Expansion').  Each modifier must be introduced by a separate ':'.   Note  also
       that  the result after modification 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 presence 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-exe-
       cutable, 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'.



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