Provided by: zsh-common_5.1.1-1ubuntu2_all bug

NAME

       zshexpn - zsh expansion and substitution

DESCRIPTION

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

       History Expansion
              This is performed only in interactive shells.

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

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

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

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

       The following sections explain the types of expansion in detail.

HISTORY EXPANSION

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

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

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

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

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

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

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

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

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

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

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

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

       !n     Refer to command-line n.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       l      Convert the words to all lowercase.

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

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

       Q      Remove one level of quotes from the substituted words.

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

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

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

              See further notes on this form of substitution below.

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

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

       u      Convert the words to all uppercase.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

PROCESS SUBSTITUTION

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              (mycmd =(myoutput)) &!

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

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

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

       outputs something resembling the following

              File /tmp/zsh6nU0kS:
              This be the verse

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

PARAMETER EXPANSION

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              For example,

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              is always true for any possible value of $str.

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

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

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

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

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

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

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

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

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

       L      Convert all letters in the result to lower case.

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

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

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

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

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

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

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

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

       Q      Remove one level of quotes from the resulting words.

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

              local  for local parameters

              left   for left justified parameters

              right_blanks
                     for right justified parameters with leading blanks

              right_zeros
                     for right justified parameters with leading zeros

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

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

              readonly
                     for readonly parameters

              tag    for tagged parameters

              export for exported parameters

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

              hide   for parameters with the `hide' flag

              hideval
                     for parameters with the `hideval' flag

              special
                     for special parameters defined by the shell

       u      Expand only the first occurrence of each unique word.

       U      Convert all letters in the result to upper case.

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

       V      Make any special characters in the resulting words visible.

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

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

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

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

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

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

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

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

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

              For example,

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

              splits the variable on a :.

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

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

              treats `|' as a pattern and succeeds if and only if $array contains the string  `?'
              as  an  element.   The  ~  may be repeated to toggle the behaviour; its effect only
              lasts to the end of the parenthesised group.

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

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

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

              If either of string1 or string2 is present but empty, i.e. there are two delimiters
              together at that point, the first character of $IFS is used instead.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       M      Include the matched portion in the result.

       N      Include the length of the match in the result.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       20. RC_EXPAND_PARAM
              At  this  point the decision is made whether any resulting array elements are to be
              combined element  by  element  with  surrounding  text,  as  given  by  either  the
              RC_EXPAND_PARAM option or the `^' flag.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

COMMAND SUBSTITUTION

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

ARITHMETIC EXPANSION

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

BRACE EXPANSION

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

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

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

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

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

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

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

FILENAME EXPANSION

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

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

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

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

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

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

              reply=(s 16)

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

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

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

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

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

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

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

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

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

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

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

FILENAME GENERATION

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

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

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

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

       ?      Matches any character.

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

              [:alnum:]
                     The character is alphanumeric

              [:alpha:]
                     The character is alphabetic

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

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

              [:cntrl:]
                     The character is a control character

              [:digit:]
                     The character is a decimal digit

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

              [:lower:]
                     The character is a lowercase letter

              [:print:]
                     The character is printable

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

              [:space:]
                     The character is whitespace

              [:upper:]
                     The character is an uppercase letter

              [:xdigit:]
                     The character is a hexadecimal digit

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              For example,

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

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

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

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

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

              Pattern matching with backreferences is slightly slower than without.

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

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

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

              For example,

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       1.     Different characters, as in fooxbar and fooybar.

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

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

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

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

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

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

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

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

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

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

              ls (*/)#bar

       or

              ls **/bar

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

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

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

       If the option EXTENDED_GLOB is set, a different syntax for glob qualifiers  is  available,
       namely  `(#qx)'  where x is any of the same glob qualifiers used in the other format.  The
       qualifiers must still appear at the  end  of  the  pattern.   However,  with  this  syntax
       multiple  glob  qualifiers  may be chained together.  They are treated as a logical AND of
       the individual sets of flags.  Also, as the syntax is unambiguous, the expression will  be
       treated  as glob qualifiers just as long any parentheses contained within it are balanced;
       appearance of `|', `(' or `~' does not negate the effect.  Note that  qualifiers  will  be
       recognised  in  this  form even if a bare glob qualifier exists at the end of the pattern,
       for example `*(#q*)(.)' will recognise executable regular files if both options  are  set;
       however,  mixed  syntax  should  probably  be  avoided for the sake of clarity.  Note that
       within conditions using the `[[' form the presence of a parenthesised  expression  (#q...)
       at  the  end  of  a string indicates that globbing should be performed; the expression may
       include glob qualifiers, but it is also valid if it is simply (#q).  This does  not  apply
       to  the  right  hand  side  of  pattern  match operators as the syntax already has special
       significance.

       A qualifier may be any one of the following:

       /      directories

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

       .      plain files

       @      symbolic links

       =      sockets

       p      named pipes (FIFOs)

       *      executable plain files (0100 or 0010 or 0001)

       %      device files (character or block special)

       %b     block special files

       %c     character special files

       r      owner-readable files (0400)

       w      owner-writable files (0200)

       x      owner-executable files (0100)

       A      group-readable files (0040)

       I      group-writable files (0020)

       E      group-executable files (0010)

       R      world-readable files (0004)

       W      world-writable files (0002)

       X      world-executable files (0001)

       s      setuid files (04000)

       S      setgid files (02000)

       t      files with the sticky bit (01000)

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

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

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

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

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

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

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

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

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

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

       ddev   files on the device dev

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

       U      files owned by the effective user ID

       G      files owned by the effective group ID

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

       gid    like uid but with group IDs or names

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

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

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

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

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

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

       ^      negates all qualifiers following it

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

       M      sets the MARK_DIRS option for the current pattern

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

       N      sets the NULL_GLOB option for the current pattern

       D      sets the GLOB_DOTS option for the current pattern

       n      sets the NUMERIC_GLOB_SORT option for the current pattern

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

              Implies oN when no oc qualifier is used.

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

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

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

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

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

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

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

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

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

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

              ls *(-/)

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

              ls *(-@)

       lists all broken symbolic links, and

              ls *(%W)

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

              ls *(W,X)

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

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

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

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

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

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

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