Provided by: zsh-common_5.1.1-1ubuntu2.3_all bug

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  performed  immediately  after  alias  expansion,
              preceding the set of five expansions mentioned above.

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

       The following sections explain the types of expansion in detail.

HISTORY EXPANSION

       History expansion allows you to use words from previous command lines in the command line you are typing.
       This simplifies spelling 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 expansions do not nest.  The `!' can be escaped with
       `\' or can be enclosed between a pair of single quotes ('') to  suppress  its  special  meaning.   Double
       quotes will not work for this.  Following this history character is an optional event designator (see the
       section `Event Designators') and then an optional word designator (the section  `Word  Designators');  if
       neither of these designators is present, no history expansion occurs.

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

       By  default,  a  history  reference  with  no  event designator refers to the same event as any preceding
       history reference on that command line; if it is the only history reference in a command,  it  refers  to
       the  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  mechanism  is  temporarily
       disabled  until  the  current list (see zshmisc(1)) is fully parsed.  The `!"' is removed from the input,
       and any subsequent `!' characters have no special significance.

       A less convenient but more comprehensible form of command history support is provided 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 previous command.

       !n     Refer to command-line n.

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

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

       !?str[?]
              Refer to the most recent command containing str.  The trailing `?' is necessary if this  reference
              is to be followed by a 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 command).  Anything else results in an error, although
       the error may not be the most obvious one.

   Modifiers
       After the optional word designator, you can add a sequence of one or more  of  the  following  modifiers,
       each  preceded  by  a  `:'.  These 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 systems do).

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

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

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

       l      Convert the words to all lowercase.

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

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

       Q      Remove one level of quotes from the substituted words.

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

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

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

              See further notes on this form of substitution below.

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

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

       u      Convert the words to all uppercase.

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

       The  s/l/r/  substitution  works  as  follows.   By  default  the left-hand side of substitutions are not
       patterns, but character strings.  Any character can be  used  as  the  delimiter  in  place  of  `/'.   A
       backslash  quotes  the  delimiter character.  The character `&', in the right-hand-side r, is replaced by
       the text from the left-hand-side l.  The `&' can be quoted with a backslash.  A null l uses the  previous
       string  either  from  the  previous  l or from the contextual scan string s from `!?s'.  You can omit the
       rightmost delimiter if a newline 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 qualifiers an extra backslash is needed as a & is a special
       character in this case.

       Also note that the order of expansions affects the interpretation of l and r.  When  used  in  a  history
       expansion,  which  occurs  before any other expansions, l and r are treated as literal strings (except as
       explained for HIST_SUBST_PATTERN below).  When used in parameter expansion, the replacement of r into the
       parameter's  value  is  done  first,  and then any additional process, parameter, command, arithmetic, or
       brace references are applied, which may evaluate those substitutions and expansions more than once  if  l
       appears  more  than  once  in  the  starting  value.  When used in a glob qualifier, any substitutions or
       expansions are performed once at the time the qualifier is parsed, even before the `:s' expression itself
       is divided into l and r sides.

       If  the  option  HIST_SUBST_PATTERN  is set, l is treated as a pattern of the usual form described in the
       section FILENAME GENERATION below.  This can be used in all the places  where  modifiers  are  available;
       note,  however, that in globbing qualifiers parameter substitution has already taken place, so parameters
       in the replacement string should be quoted to ensure they are replaced at the correct  time.   Note  also
       that  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  substitution  are not subject to the NO_BAD_PATTERN option so will cause an
       error.

       When HIST_SUBST_PATTERN is set, l may start with a # to indicate that the pattern must match at the start
       of  the  string  to  be  substituted,  and a % may appear at the start or after an # to indicate that the
       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...) expression, which consists of a
       substitution modifier anchored to the start and end of each word  (#%).   This  turns  on  backreferences
       ((#b)),  so  that  the parenthesised subexpression is available in the replacement string as ${match[1]}.
       The replacement string is quoted so that the parameter is not substituted before the  start  of  filename
       generation.

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

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

       F:expr:
              Like f, but repeats only n times if the expression expr 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 `}', respectively.

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

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

PROCESS SUBSTITUTION

       Each part of a command argument that takes the form `<(list)',  `>(list)'  or  `=(list)'  is  subject  to
       process  substitution.   The  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 subprocess 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  corresponding  to a file descriptor; otherwise, if the system supports named pipes
       (FIFOs), the command argument will be a named pipe.  If the form with > is selected then writing on  this
       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, particularly if this is necessary for security reasons such as when the
       programme is running setuid.  In the second case, if the programme does not actually open the  file,  the
       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 substitutions in the above
       example.

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

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

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

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

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

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

              (mycmd =(myoutput)) &!

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

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

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

       outputs something resembling the following

              File /tmp/zsh6nU0kS:
              This be the verse

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

PARAMETER EXPANSION

       The  character  `$'  is  used  to  introduce  parameter expansions.  See 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 Generation'.  Note  that  these  patterns,  along
       with  the  replacement  text of any substitutions, are themselves subject to parameter expansion, command
       substitution, and arithmetic expansion.  In addition to the following  operations,  the  colon  modifiers
       described  in  the  section  `Modifiers' in the section `History Expansion' can be applied:  for example,
       ${i:s/foo/bar/} performs string substitution on the expansion of parameter $i.

       ${name}
              The value, if any, of the parameter name is substituted.  The braces are required if the expansion
              is to be followed by a letter, digit, or underscore that is not to be interpreted as part of name.
              In addition, more complicated forms of substitution usually require  the  braces  to  be  present;
              exceptions,  which  only  apply if the option KSH_ARRAYS is not set, are a single 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, unconditionally set name to word.  In all forms,
              the value of the parameter is then substituted.

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

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

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

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

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

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

       ${name:^arrayname}
       ${name:^^arrayname}
              Zips two arrays, such that the output array is twice as long as the shortest (longest  for  `:^^')
              of name and arrayname, with the elements alternatingly being picked from them. For `:^', if one of
              the input arrays is longer, the output will stop when the end of the  shorter  array  is  reached.
              Thus,

                     a=(1 2 3 4); b=(a b); print ${a:^b}

              will  output  `1  a 2 b'.  For `:^^', then the input is repeated until all of the longer array has
              been used up and the above will output `1 a 2 b 3 a 4 b'.

              Either or both inputs may be a scalar, they will be treated as an  array  of  length  1  with  the
              scalar  as  the  only  element.  If either array is empty, the other array is output with no extra
              elements inserted.

              Currently the following code will output `a b' and `1' as two  separate  elements,  which  can  be
              unexpected.  The  second  print  provides  a  workaround  which should continue to work if this is
              changed.

                     a=(a b); b=(1 2); print -l "${a:^b}"; print -l "${${a:^b}}"

       ${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 nothing is substituted.

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

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

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

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

              If offset is negative, the - may not  appear  immediately  after  the  :  as  this  indicates  the
              ${name:-word}  form of substitution.  Instead, a space may be inserted before the -.  Furthermore,
              neither offset nor length may begin with an alphabetic  character  or  &  as  these  are  used  to
              indicate history-style modifiers.  To substitute a value from a variable, the recommended approach
              is to precede it with a $ as this signifies the intention (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 double-quoted substitution, so that expressions  like  ${name/$opat/$npat}
              will  work,  but  note  the  usual rule that pattern characters in $opat are not treated specially
              unless either the option GLOB_SUBST is set, or $opat is instead substituted as ${~opat}.

              The pattern may begin with a `#', in which case the pattern must match at the start of the string,
              or  `%',  in  which case it must match at the end of the string, or `#%' in which case the 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 substituted parameter.  Note also that
              the  `#',  `%'  and  `#%  are not active if they occur inside a substituted parameter, even at the
              start.

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

              For example,

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

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

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

              If the option POSIX_IDENTIFIERS is not set, and spec  is  a  simple  name,  then  the  braces  are
              optional;  this  is  true  even  for special parameters so e.g. $#- and $#* take the length of the
              string $- and the array $* respectively.  If POSIX_IDENTIFIERS is set, then  braces  are  required
              for the # to be treated in this fashion.

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

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

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

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

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

              In nested substitutions, note that the effect of the ~ applies to the result of the current  level
              of  substitution.   A  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 following flags are supported:

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

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

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

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

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

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

       b      Quote  with  backslashes only characters that are special to pattern matching. This is useful when
              the contents of the variable are to be tested using GLOB_SUBST, including the ${~...} switch.

              Quoting using one of the q family of flags does not work for this purpose  since  quotes  are  not
              stripped from non-pattern characters by GLOB_SUBST.  In other words,

                     pattern=${(q)str}
                     [[ $str = ${~pattern} ]]

              works if $str is `a*b' but not if it is `a b', whereas

                     pattern=${(b)str}
                     [[ $str = ${~pattern} ]]

              is always true for any possible value of $str.

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

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

       D      Assume the string or array elements contain directories and attempt to substitute the leading part
              of  these  by  names.   The  remainder  of  the  path (the whole of it if the leading part was not
              substituted) 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 subscript 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 initial zeroes are sorted before those with fewer
              or  none.  Hence the array `foo1 foo02 foo2 foo3 foo20 foo23' is sorted into the order shown.  May
              be combined with `i' or `O'.

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

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

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

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

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

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

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

       Q      Remove one level of quotes from the resulting words.

       t      Use  a  string describing the type of the parameter where the value of the parameter would usually
              appear. This string 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

              hideval
                     for parameters with the `hideval' 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 delimiters are also counted.

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

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

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

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

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

              Alternatively, with this option string arguments may be in the form $var in which case  the  value
              of  the  variable  is substituted.  Note this form is strict; the string argument does not undergo
              general parameter expansion.

              For example,

                     sep=:
                     val=a:b:c
                     print ${(ps.$sep.)val}

              splits the variable on a :.

       ~      Strings inserted into the expansion by any of the flags below are to be treated as patterns.  This
              applies  to  the  string  arguments  of  flags  that  follow ~ within the same set of parentheses.
              Compare with ~ outside parentheses, which forces the entire substituted string to be treated as  a
              pattern.  Hence, for example,

                     [[ "?" = ${(~j.|.)array} ]]

              treats  `|' as a pattern and succeeds if and only if $array contains the string `?' as an element.
              The ~ 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  either  of  string1 or string2 is present but empty, i.e. there are two delimiters together at
              that point, the first character of $IFS is used instead.

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

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

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

       m      Only useful together with one of the flags l or r or with the # length operator when the MULTIBYTE
              option  is  in  effect.  Use the character width reported by the system in calculating how much of
              the string it occupies or the overall length of the string.   Most  printable  characters  have  a
              width  of  one  unit,  however  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 certain 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.
              With no options the effect is identical to z.  (Z+c+) causes comments to be parsed as a string and
              retained; any field in the resulting array beginning with  an  unquoted  comment  character  is  a
              comment.   (Z+C+)  causes  comments  to be parsed and removed.  The rule for comments is standard:
              anything between a word starting with the third character of $HISTCHARS, default #, up to the next
              newline  is a comment.  (Z+n+) causes unquoted newlines to be treated as ordinary whitespace, else
              they are treated as if they are shell code delimiters and converted to  semicolons.   Options  are
              combined within the same set of delimiters, e.g. (Z+Cn+).

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

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

       S      Search substrings as well as beginnings or ends; with # start from the beginning and with %  start
              from the end of the string.  With substitution via ${.../...} or ${...//...}, specifies non-greedy
              matching, i.e. that the shortest instead of the 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 substitution 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 substitution  will  return  either  a
              scalar  or  an array as determined by the flags, possibly adjusted for quoting.  All the following
              steps take place where applicable at all levels of substitution.  Note that, unless the `(P)' flag
              is  present,  the flags and any subscripts apply directly to the value of the nested substitution;
              for example, the expansion ${${foo}} behaves exactly the same as ${foo}.

              At each nested level of substitution, the substituted  words  undergo  all  forms  of  single-word
              substitution  (i.e. not filename generation), including command substitution, arithmetic expansion
              and filename expansion (i.e. leading ~ and =).  Thus, for example, ${${:-=cat}:h} expands  to  the
              directory where the cat program resides.  (Explanation: the internal substitution has no parameter
              but a default value =cat, which is expanded by 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 particular the L, R, Z, u and
              l flags for padding and capitalization, are applied directly to the parameter value.   Note  these
              flags  are  options  to  the  command,  e.g. `typeset -Z'; they are not the same as the flags used
              within parameter substitutions.

       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.  Flags such as (k) and (v) which alter the result of
              subscripting are applied.

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

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

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

       7. Modifiers
              Any  modifiers,  as  specified  by  a  trailing  `#',  `%',  `/' (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 character.

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

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

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

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

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

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

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

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

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

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

       18. Uniqueness
              If  the result is an array and the `(u)' flag was present, 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. RC_EXPAND_PARAM
              At this point the decision is made whether any resulting array elements are to be combined element
              by element with surrounding text, as given by either the RC_EXPAND_PARAM option or the `^' flag.

       21. 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.

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

       23. 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.

       24. 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  example,  ${(f)"$(<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 generation.

ARITHMETIC EXPANSION

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

BRACE EXPANSION

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

       An expression of the form `{n1..n2}', where n1 and n2 are integers, is expanded to every  number  between
       n1  and n2 inclusive.  If either number begins with a zero, all the resulting numbers will be padded with
       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 characters).

       An expression of the form `{c1..c2}', where c1 and c2 are  single  characters  (which  may  be  multibyte
       characters),  is expanded to every character in the range from c1 to c2 in whatever character sequence is
       used internally.  For characters with code points below 128 this is US ASCII (this is the only case  most
       users will need).  If any intervening character is not printable, appropriate quotation is used to render
       it printable.  If the character sequence is reversed, the output is in reverse order,  e.g.  `{d..a}'  is
       substituted as `d c b a'.

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

       Note  that  brace  expansion  is  not  part  of  filename  generation  (globbing);  an expression 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 produce a `no match' error if either of the two expressions does
       not match; this is to be contrasted with */(foo|bar), which is treated as a single pattern but  otherwise
       has similar effects.

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

FILENAME EXPANSION

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

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

       A `~' followed by a number is replaced by the directory at that 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_directory_name_functions exists and
       contains an array of function names, then the functions 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
       characters) is s, then the function sets

              reply=(s 16)

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

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

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

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

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

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

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

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

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

   Notes
       Filename expansion is performed on the right  hand  side  of  a  parameter  assignment,  including  those
       appearing  after  commands of the typeset family.  In this case, the right hand side will be treated as a
       colon-separated list in the manner of the PATH parameter, so that a `~' or an  `='  following  a  `:'  is
       eligible  for  expansion.   All  such 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 `#' characters 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 specially.

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

       ?      Matches any character.

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

              [:alnum:]
                     The character is alphanumeric

              [:alpha:]
                     The character is alphabetic

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

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

              [:cntrl:]
                     The character is a control character

              [:digit:]
                     The character is a decimal digit

              [:graph:]
                     The character is a printable character other than 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.

              [:INCOMPLETE:]
                     Matches  a  byte  that  starts an incomplete multibyte character.  Note that there may be a
                     sequence of more than one bytes  that  taken  together  form  the  prefix  of  a  multibyte
                     character.    To  test  for  a  potentially  incomplete  byte  sequence,  use  the  pattern
                     `[[:INCOMPLETE:]]*'.  This will never match a sequence  starting  with  a  valid  multibyte
                     character.

              [:INVALID:]
                     Matches  a  byte  that  does  not  start  a  valid multibyte character.  Note this may be a
                     continuation byte of an incomplete multibyte character as any part of  a  multibyte  string
                     consisting of invalid and incomplete multibyte characters is treated as single bytes.

              [: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 filename generation).  There is  one  exception:   a
              group  of  the  form  (pat/)#  appearing  as  a  complete  path  segment  can  match a sequence of
              directories.  For example, foo/(a*/)#bar matches foo/bar, foo/any/bar,  foo/any/anyother/bar,  and
              so on.

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

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

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

       x#     (Requires EXTENDED_GLOB to be set.)  Matches zero or more 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 preceding `@', `*', `+',
       `?' or `!'.  This character need not be unquoted to have special effects, but the `(' must be.

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

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

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

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

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

   Precedence
       The precedence of the operators given above is (highest) `^',  `/',  `~',  `|'  (lowest);  the  remaining
       operators  are  simply  treated from left to right as part of a string, with `#' and `##' applying to the
       shortest  possible  preceding  unit  (i.e.  a  character,  `?',  `[...]',  `<...>',  or  a  parenthesised
       expression).   As mentioned above, a `/' used as a 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 parentheses is matched, the strings matched by
              the groups are stored in the array $match, the indices of the beginning of the matched parentheses
              in  the  array  $mbegin,  and the indices of the end in the array $mend, with the first element 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 backreferences fail to match -- which happens if they
              are in an alternate branch which fails to match, or if they are followed by  #  and  matched  zero
              times -- then the matched string is set to the empty string, and the start and end indices are set
              to -1.

              Pattern matching with backreferences is slightly slower than without.

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

       cN,M   The flag (#cN,M) can be used anywhere that the # or  ##  operators  can  be  used  except  in  the
              expressions  `(*/)#' and `(*/)##' in filename generation, where `/' has special meaning; it cannot
              be combined with other globbing flags and a bad pattern error occurs if it is  misplaced.   It  is
              equivalent  to the form {N,M} in regular expressions.  The previous character or group is required
              to match between N and M times, inclusive.  The form (#cN) requires exactly N matches;  (#c,M)  is
              equivalent  to 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 similar 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 standard 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 characters in a pattern,
              provided the shell was compiled with MULTIBYTE_SUPPORT.  This overrides the MULTIBYTE option;  the
              default behaviour is taken from the option.  Compare U.  (Mnemonic: typically multibyte characters
              are from Unicode in the UTF-8 encoding, although any extension of ASCII supported  by  the  system
              library may be used.)

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

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

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

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

       1.     Different characters, as in fooxbar and fooybar.

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

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

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

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

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

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

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

       Entire  path  segments may be matched approximately, so that `(#a1)/foo/d/is/available/at/the/bar' allows
       one error in any path 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 qualifiers.   A  glob  subexpression  that
       would  normally  be  taken as glob qualifiers, for example `(^x)', can be forced to be treated as part of
       the glob pattern by doubling the parentheses, in this case producing `((^x))'.

       If the option EXTENDED_GLOB is set, a different syntax for glob 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.  However, with this syntax multiple glob  qualifiers  may  be  chained  together.
       They  are  treated as a logical AND of the individual sets of flags.  Also, as the syntax is unambiguous,
       the expression will be treated as glob qualifiers just as long any parentheses contained  within  it  are
       balanced;  appearance  of  `|',  `('  or  `~'  does  not negate the effect.  Note that qualifiers will be
       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.  Note  that  within  conditions  using  the  `[['  form  the
       presence  of  a parenthesised expression (#q...) at the end of a string indicates that globbing should be
       performed; the expression may include glob qualifiers, but it is also valid if it is simply  (#q).   This
       does  not  apply  to  the  right  hand  side of pattern match operators as the syntax already has special
       significance.

       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 or 0010 or 0001)

       %      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 number ensures that the corresponding bits in the file-modes are not
              checked, this is only useful in combination with `='.

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

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

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

              In  the  first form, the first character after the `e' will be used as a separator and anything up
              to the next matching 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 available in  the  parameter
              REPLY;  the  parameter  may  be  altered  to  a string to be inserted into the list instead of the
              original filename.  In addition, the parameter reply may be set to an array  or  a  string,  which
              overrides  the  value  of REPLY.  If set to an array, the latter is inserted into the command line
              word by word.

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

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

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

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

       ddev   files on the device dev

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

       U      files owned by the effective user ID

       G      files owned by the effective group ID

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

       gid    like uid but with group IDs or names

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

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

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

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

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

              If this flag is directly followed by a size specifier `k' (`K'), `m' (`M'),  or  `p'  (`P')  (e.g.
              `Lk-50')  the check is performed with kilobytes, megabytes, or blocks (of 512 bytes) instead.  (On
              some systems additional specifiers are available for gigabytes, `g' or `G', and terabytes, `t'  or
              `T'.)  If  a  size  specifier  is  used  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

       Yn     enables  short-circuit  mode:  the  pattern  will  expand  to at most n filenames.  If more than n
              matches exist, only the first n matches in directory traversal order will be considered.

              Implies oN when no oc qualifier is used.

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

              The  default  sorting  is  n  (by name) unless the Y glob qualifier is used, in which case it is N
              (unsorted).

              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_context.  The code should modify the parameter REPLY in some fashion.  On return, the
              value of the parameter is used instead of the file name as the string on which  to  sort.   Unlike
              other  sort  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 ...'

              If  the  modifier  ^ is active, then string will be appended instead of prepended.  Prepending and
              appending is done independently so both can be used on the same glob expression;  for  example  by
              writing  `*(P:foo:^P:bar:^P:baz:)'  which  produces  the command line arguments `foo baz file1 bar
              ...'

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

       If  a `:' appears in a qualifier list, the remainder of the expression in parenthesis is interpreted as a
       modifier (see the section `Modifiers' in  the  section  `History  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 *(-@)

       lists all broken symbolic links, and

              ls *(%W)

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

              ls *(W,X)

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

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

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

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

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

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

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