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ZSHEXPN(1)                           General Commands Manual                           ZSHEXPN(1)



NAME
       zshexpn - zsh expansion and substitution

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

       History Expansion
              This is performed only in interactive shells.

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

       Process Substitution
       Parameter Expansion
       Command Substitution
       Arithmetic Expansion
       Brace Expansion
              These five are performed in one step in left-to-right fashion.  After these  expan-
              sions, 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 com-
              patibility with sh and ksh.  In that case filename expansion is  performed  immedi-
              ately after alias expansion, preceding the set of five expansions mentioned above.

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

       The following sections explain the types of expansion in detail.

HISTORY EXPANSION
       History  expansion allows you to use words from previous command lines in the command line
       you are typing.  This simplifies spelling corrections and the  repetition  of  complicated
       commands or arguments.  Immediately before execution, each command is saved in the history
       list, the size of which is controlled by the HISTSIZE parameter.  The one most recent com-
       mand  is  always retained in any case.  Each saved command in the history list is called a
       history event and is assigned a number, beginning with 1 (one) when the shell  starts  up.
       The  history  number that you may see in your prompt (see EXPANSION OF PROMPT SEQUENCES in
       zshmisc(1)) is the number that is to be assigned to the next command.

   Overview
       A history expansion begins with the first character of the histchars parameter,  which  is
       `!'  by  default,  and  may  occur anywhere on the command line; history expansions do not
       nest.  The `!' can be escaped with `\' or can be enclosed between a pair of single  quotes
       ('')  to  suppress  its special meaning.  Double quotes will not work for this.  Following
       this history character is an optional event designator (see the  section  `Event  Designa-
       tors')  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 previ-
       ous 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  modi-
       fiers   (see   the  section  `Modifiers')  may  follow  the  final  `^'.   In  particular,
       `^foo^bar^:G' performs a global substitution.

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

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

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

       !      Start  a  history  expansion, except when followed by a blank, newline, `=' or `('.
              If followed immediately by a word designator (see the section `Word  Designators'),
              this  forms  a  history  reference with no event designator (see the section `Over-
              view').

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

       !n     Refer to command-line n.

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

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

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

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

       !{...} Insulate a history reference from adjacent characters (if necessary).

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

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

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

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

       a      Turn  a file name into an absolute path:  prepends the current directory, if neces-
              sary, and resolves any use of `..' and `.' in the path.  Note that the  transforma-
              tion 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 resolu-
              tion 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  defi-
              nition  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 exten-
              sion are not altered.  A filename extension is a `.'  followed  by  any  number  of
              characters  (including  zero) that are neither `.' nor `/' and that continue to the
              end of the string.  For  example,  the  extension  of  `foo.orig.c'  is  `.c',  and
              `dir.c/foo' has no extension.

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

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

              See further notes on this form of substitution below.

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

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

       u      Convert the words to all uppercase.

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

       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 omit-
       ted.  Note the same record of the last l and r is maintained across all  forms  of  expan-
       sion.

       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  sub-
       stitution  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  pat-
       terns  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  substi-
       tuted.  The % or # may be quoted with two backslashes.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       The  = form is useful as both the /dev/fd and the named pipe implementation of <(...) have
       drawbacks.  In the former case, some programmes may automatically close the file  descrip-
       tor  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  sec-
       ond  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 sys-
       tems  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 (pro-
       vided 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 com-
       mand, the parent shell does not wait for process to finish and hence an  immediately  fol-
       lowing  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 par-
       ent 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  com-
       pletion.

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

              (mycmd =(myoutput)) &!

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

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

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

       outputs something resembling the following

              File /tmp/zsh6nU0kS:
              This be the verse

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

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

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

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

       ${name}
              The value, if any, of the parameter name is substituted.  The braces  are  required
              if the expansion is to be followed by a letter, digit, or underscore that is not to
              be interpreted as part of name.  In addition, more complicated forms  of  substitu-
              tion  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 appear-
              ing  after  the  name, or any of the characters `^', `=', `~', `#' or `+' appearing
              before the name, all of which work with or without braces.

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

       ${+name}
              If name is the name of a set parameter `1' is substituted, otherwise `0' is substi-
              tuted.

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

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

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

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

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

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

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

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

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

       ${name:|arrayname}
              If arrayname is the name (N.B., not contents) of an array variable, then  any  ele-
              ments  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 expres-
              sion.

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

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

              If offset is non-negative, then if the variable name is  a  scalar  substitute  the
              contents  starting offset characters from the first character of the string, and if
              name is an array substitute elements starting offset elements from the  first  ele-
              ment.   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  charac-
              ters where appropriate.

              offset and length undergo the same set of shell substitutions as for scalar assign-
              ment; 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  syn-
              tax) 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  indi-
              cates  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 substi-
              tute 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 unread-
              able); 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 off-
              set 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  posi-
              tional  parameter  array  is effectively extended by prepending $0.  Hence ${*:0:1}
              substitutes $0 and ${*:1:1} substitutes $1.

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

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

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

              For example,

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

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

       ${#spec}
              If  spec  is one of the above substitutions, substitute the length in characters of
              the result instead of the result itself.  If spec is an array  expression,  substi-
              tute  the  number  of  elements of the result.  Note that `^', `=', and `~', below,
              must appear to the left of `#' when these forms are combined.

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

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

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

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

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

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

       If a ${...} type parameter expression or a $(...) type command  substitution  is  used  in
       place  of  name above, it is expanded first and the result is used as if it were the value
       of name.  Thus it is possible to perform nested operations:   ${${foo#head}%tail}  substi-
       tutes  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 expres-
       sion as described in Array Parameters in zshparam(1).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       L      Convert all letters in the result to lower case.

       n      Sort decimal integers numerically; if the first differing 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  parame-
              ter 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  back-
              slashes;  unprintable or invalid characters are quoted using the $'\NNN' form, with
              separate quotes for each octet.

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

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

       Q      Remove one level of quotes from the resulting words.

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

              local  for local parameters

              left   for left justified parameters

              right_blanks
                     for right justified parameters with leading blanks

              right_zeros
                     for right justified parameters with leading zeros

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

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

              readonly
                     for readonly parameters

              tag    for tagged parameters

              export for exported parameters

              unique for arrays which keep only the first occurrence of duplicated values

              hide   for parameters with the `hide' flag

              special
                     for special parameters defined by the shell

       u      Expand only the first occurrence of each unique word.

       U      Convert all letters in the result to upper case.

       v      Used  with  k,  substitute (as two consecutive words) both the key and the value of
              each associative array element.  Used with subscripts, force values to  be  substi-
              tuted 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  spe-
              cially  but  as  ordinary  strings, similar to interactive shells with the INTERAC-
              TIVE_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 sin-
              gle words in the result use nested expansions as in `${${(z)foo}[2]}'. Likewise, to
              remove the quotes in the resulting words use `${(Q)${(z)foo}}'.

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

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

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

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

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

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

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

              If  the  MULTIBYTE option is in effect, the flag m may also be given, in which case
              widths will be used for the calculation of padding; otherwise 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  mecha-
              nism 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 charac-
              ters themselves have non-zero width (true in certain alphabets).

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

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

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

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

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

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

       Z:opts:
              As  z  but takes a combination of option letters between a following pair of delim-
              iter characters.  With no options the effect is identical to z.  (Z+c+) causes com-
              ments  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  con-
              verted to semicolons.  Options are combined within the same set of delimiters, e.g.
              (Z+Cn+).

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

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

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

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

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

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

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

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

       M      Include the matched portion in the result.

       N      Include the length of the match in the result.

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

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

       1. Nested substitution
              If  multiple  nested  ${...}  forms are present, substitution is performed from the
              inside outwards.  At each level, the substitution takes account of whether the cur-
              rent  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  substi-
              tution,  arithmetic expansion and filename expansion (i.e. leading ~ and =).  Thus,
              for example, ${${:-=cat}:h} expands to the directory where the cat program resides.
              (Explanation:  the internal substitution has no parameter but a default value =cat,
              which is expanded by filename expansion to a full path; the outer substitution then
              applies the modifier :h and takes the directory part of the path.)

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

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

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

       5. Double-quoted joining
              If the value after this process is an array, and the substitution appears in double
              quotes, and no (@) flag is present at the current level, the words of the value are
              joined  with the first character of the parameter $IFS, by default a space, between
              each word (single word arrays are not modified).  If the (j) flag is present,  that
              is used for joining instead of $IFS.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       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  gen-
       eration  takes  place.   In  particular,  note that this is liable to produce a `no match'
       error if either of the two expressions does not match;  this  is  to  be  contrasted  with
       */(foo|bar), which is treated as a single pattern but otherwise has similar effects.

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

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

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

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

   Dynamic named directories
       If the function zsh_directory_name exists, or the shell variable  zsh_directory_name_func-
       tions  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 termi-
       nates 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 can-
       didate  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 exam-
       ple,   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 ele-
       ments of the array zsh_directory_name_functions,  if  it  exists,  in  order  to  complete
       dynamic  names  for  directories.  The code for this should be as for any other completion
       function as described in zshcompsys(1).

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

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

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

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

       In certain circumstances (in prompts, for instance), when the shell  prints  a  path,  the
       path  is checked to see if it has a named directory as its prefix.  If so, then the prefix
       portion is replaced with a `~' followed by the name of the directory.  The shortest way of
       referring to the directory is used, with ties broken in favour of using a named directory,
       except when the directory is / itself.  The parameters $PWD and $OLDPWD are never abbrevi-
       ated in this fashion.

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

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

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

FILENAME GENERATION
       If a word contains an unquoted instance of one of the characters `*', `(', `|', `<',  `[',
       or  `?',  it  is  regarded as a pattern for filename generation, unless the GLOB option is
       unset.  If the EXTENDED_GLOB option is set, the `^' and `#' characters also denote a  pat-
       tern; 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 match-
       ing 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 charac-
              ters, 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 combina-
              tions, including any modifications due to local language settings, see ctype(3):

              [:alnum:]
                     The character is alphanumeric

              [:alpha:]
                     The character is alphabetic

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

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

              [:cntrl:]
                     The character is a control character

              [:digit:]
                     The character is a decimal digit

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

              [:lower:]
                     The character is a lowercase letter

              [:print:]
                     The character is printable

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

              [:space:]
                     The character is whitespace

              [:upper:]
                     The character is an uppercase letter

              [:xdigit:]
                     The character is a hexadecimal digit

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       x#     (Requires EXTENDED_GLOB to be set.)  Matches zero or more occurrences of  the  pat-
              tern  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  there-
              fore 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 `(...)#'.)

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

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

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

   Precedence
       The  precedence of the operators given above is (highest) `^', `/', `~', `|' (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 out-
       side parentheses in a filename pattern.

   Globbing Flags
       There are various flags which affect any text to their right up to the end of the  enclos-
       ing  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  corre-
              sponding  to the first parenthesised group, and so on.  These arrays are not other-
              wise 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  paren-
              thesised groups; only the first nine active parentheses can be referenced.

              For example,

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

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

              Backreferences work with all forms of pattern matching other than filename  genera-
              tion,  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 parenthe-
              ses  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  nec-
              essary  to  match  the complete segment: for example, use `X((ab|cd)#)Y' to match a
              whole string of either `ab' or `cd'  between  `X'  and  `Y',  using  the  value  of
              $match[1] rather than $match[2].

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

              Pattern matching with backreferences is slightly slower than without.

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

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

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

              For example,

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

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

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

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

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

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

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

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

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

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

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

       For  example,  the  test  string fooxx can be matched by the pattern (#i)FOOXX, but not by
       (#l)FOOXX, (#i)FOO(#I)XX or ((#i)FOOX)X.  The string (#ia2)readme specifies  case-insensi-
       tive 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  sepa-
       rately  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  sepa-
       rately  for the excluded part and must be activated separately.  Thus, (#a1)README~READ_ME
       matches READ.ME but not READ_ME, as the trailing READ_ME is matched without approximation.
       However,  (#a1)README~(#a1)READ_ME  does  not match any pattern of the form READ?ME as all
       such forms are now excluded.

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

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

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

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

              ls (*/)#bar

       or

              ls **/bar

       does a recursive directory search for files named `bar' (potentially  including  the  file
       `bar'  in  the current directory).  This form does not follow symbolic links; the alterna-
       tive 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  paren-
       theses.   The  qualifiers  specify  which filenames that otherwise match the given pattern
       will be inserted in the argument list.

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

       If the option EXTENDED_GLOB is set, a different syntax for glob qualifiers  is  available,
       namely  `(#qx)'  where x is any of the same glob qualifiers used in the other format.  The
       qualifiers must still appear at the end of the pattern.  However, with this syntax  multi-
       ple  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.

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

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

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

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

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

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

              lists  all  files  in the directory that have been modified more recently than ref-
              file.

       ddev   files on the device dev

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

       U      files owned by the effective user ID

       G      files owned by the effective group ID

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

       gid    like uid but with group IDs or names

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

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

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

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

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

              If  this  flag  is  directly followed by a `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  descend-
              ing  order, following any symbolic links.  Unless oN is used, multiple order speci-
              fiers 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 opera-
              tors, oe and o+ may be repeated, but note that the maximum number of sort operators
              of any kind that may appear in any glob expression is 12.

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

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

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

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

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

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

              ls *(-/)

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

              ls *(%W)

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

              ls *(W,X)

       lists all files in the current directory that are world-writable or world-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 start-
       ing  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  ordi-
       nary qualifier `.' is applied first, then the colon modifiers in order from left to right.
       So if EXTENDED_GLOB is set and the base pattern matches the regular file builtin.pro,  the
       shell will print `shmiltin.shmo'.



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