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       zshexpn - zsh expansion and substitution


       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

       The following sections explain the types of expansion in detail.


       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.

       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

       !      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

       !!     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.

              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

   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.

       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.

              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 qualifers an extra backslash is
       needed as a & is a special character in this case.

       If the option HIST_SUBST_PATTERN is set, l is treated as a  pattern  of
       the  usual  form  described  in  the section FILENAME GENERATION below.
       This can be used in all the places where modifiers are available; note,
       however, that in globbing qualifiers parameter substitution has already
       taken place, so parameters in the replacement string should  be  quoted
       to  ensure  they  are  replaced  at  the  correct time.  Note also that
       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

       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.

              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.


       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

       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

       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  subsitution.
       In  that case the temporary file will not be cleaned up as the shell no
       longer has any memory of the job.  A workaround is to use  a  subshell,
       for example,

              (mycmd =(myoutput)) &!

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

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

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

       outputs something resembling the following

              File /tmp/zsh6nU0kS:
              This be the verse

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


       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

       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.

              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

              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

              If  name  is  the  name  of  a set parameter `1' is substituted,
              otherwise `0' is substituted.

              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

              If  name  is  set,  or  in  the  second  form  is non-null, then
              substitute word; otherwise substitute nothing.

              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.

              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:

       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

              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.

              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.

              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).

              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.

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

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

              If offset is negative, the - may not  appear  immediately  after
              the  : as this indicates the ${name:-word} form of substitution.
              Instead, a space may be inserted  before  the  -.   Furthermore,
              neither offset nor length may begin with an alphabetic character
              or & as these are used to indicate history-style modifiers.   To
              substitute  a value from a variable, the recommended approach is
              to  precede  it  with  a  $  as  this  signifies  the  intention
              (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.

              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'.

              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.

              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

              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.

              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

       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

   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

       #      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

              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

       %      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.

       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

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

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

              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

       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

              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

                     for right justified parameters with leading blanks

                     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

                     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

                     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::'.

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

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

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

              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.

              Pad the  resulting  words  on  the  left.   Each  word  will  be
              truncated  if  required  and  placed  in a field expr characters

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

              If  the  MULTIBYTE  option  is in effect, the flag m may also be
              given, in which case widths will be used for the calculation  of
              padding;  otherwise  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

              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.

              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:

                     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}".

              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+).

              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.

              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).

       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

       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

       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

       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

       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

       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

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

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

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

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

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

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

       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):

              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.

              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

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

              produces the words `a', `1 b' and `1'.

              produces `a', `1', `b' and `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.


       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


       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'.


       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

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

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

       Note  that  brace  expansion  is  not  part  of   filename   generation
       (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.


       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,

       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

   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

              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]} )) )
                    return 1
                elif [[ $1 = n ]]; then
                  # turn the name into a directory
                  [[ $2 != (#b)p:(?*) ]] && return 1
                  typeset -ga reply
                elif [[ $1 = c ]]; then
                  # complete names
                  local expl
                  local -a dirs
                  _wanted dynamic-dirs expl 'dynamic directory' compadd -S\] -a dirs
                  return 1
                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

   `=' 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

       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

       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.


       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):

                     The character is alphanumeric

                     The character is alphabetic

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

                     The character is either space or tab

                     The character is a control character

                     The character is a decimal digit

                     The   character  is  a  printable  character  other  than

                     The character is a lowercase letter

                     The character is printable

                     The character is printable but neither  alphanumeric  nor

                     The character is whitespace

                     The character is an uppercase letter

                     The character is a hexadecimal digit

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

                     The  character  is  allowed  to  form  part  of  a  shell
                     identifier, such as a parameter name

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

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

                     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.

              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

       (...)  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

       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

       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]]}

              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

       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

       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,

              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


              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

       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.

       A qualifier may be any one of the following:

       /      directories

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

       .      plain files

       @      symbolic links

       =      sockets

       p      named pipes (FIFOs)

       *      executable plain files (0100)

       %      device files (character or block special)

       %b     block special files

       %c     character special files

       r      owner-readable files (0400)

       w      owner-writable files (0200)

       x      owner-executable files (0100)

       A      group-readable files (0040)

       I      group-writable files (0020)

       E      group-executable files (0010)

       R      world-readable files (0004)

       W      world-writable files (0002)

       X      world-executable files (0001)

       s      setuid files (04000)

       S      setgid files (02000)

       t      files with the sticky bit (01000)

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

       +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 ]] }
                     ls -l *(+nt)

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

       ddev   files on the device dev

              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

              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.

              like the file access qualifier, except that  it  uses  the  file
              modification time.

              like  the  file  access  qualifier, except that it uses the file
              inode change time.

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

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

       ^      negates all qualifiers following it

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

       M      sets the MARK_DIRS option for the current pattern

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

       N      sets the NULL_GLOB option for the current pattern

       D      sets the GLOB_DOTS option for the current pattern

       n      sets the NUMERIC_GLOB_SORT option for the current pattern

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

              oe  and  o+  are  special cases; they are each followed by shell
              code, delimited as for the e  glob  qualifier  and  the  +  glob
              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.

              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

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

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

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

       If a `:' appears in a qualifier list, the remainder of  the  expression
       in   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.

              ls *(-/)

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

              ls *(%W)

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

              ls *(W,X)

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

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

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

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

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

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

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

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