Provided by: zsh_4.3.4-24ubuntu1_i386 bug

NAME

       zshparam - zsh parameters

DESCRIPTION

       A  parameter  has  a name, a value, and a number of attributes.  A name
       may be any sequence of alphanumeric characters and underscores, or  the
       single  characters ‘*’, ‘@’, ‘#’, ‘?’, ‘-’, ‘$’, or ‘!’.  The value may
       be a scalar (a string), an integer, an array (indexed numerically),  or
       an  associative array (an unordered set of name-value pairs, indexed by
       name).  To declare the type of a parameter, or to assign  a  scalar  or
       integer value to a parameter, use the typeset builtin.

       The  value  of  a  scalar  or integer parameter may also be assigned by
       writing:

              name=value

       If the integer attribute, -i, is set for name, the value is subject  to
       arithmetic  evaluation.   Furthermore,  by  replacing  ‘=’ with ‘+=’, a
       parameter can  be  added  or  appended  to.   See  the  section  ‘Array
       Parameters’ for additional forms of assignment.

       To  refer to the value of a parameter, write ‘$name’ or ‘${name}’.  See
       Parameter Expansion in zshexpn(1) for complete details.

       In the parameter lists that follow, the mark ‘<S>’ indicates  that  the
       parameter  is  special.   Special  parameters  cannot  have  their type
       changed or their readonly  attribute  turned  off,  and  if  a  special
       parameter  is  unset, then later recreated, the special properties will
       be retained.  ‘<Z>’ indicates that the parameter does  not  exist  when
       the shell initializes in sh or ksh emulation mode.

ARRAY PARAMETERS

       To assign an array value, write one of:

              set -A name value ...
              name=(value ...)

       If  no  parameter  name exists, an ordinary array parameter is created.
       If the parameter name exists and is a scalar, it is replaced by  a  new
       array.  Ordinary array parameters may also be explicitly declared with:

              typeset -a name

       Associative arrays must be declared before assignment, by using:

              typeset -A name

       When name refers to an associative array, the list in an assignment  is
       interpreted as alternating keys and values:

              set -A name key value ...
              name=(key value ...)

       Every  key  must  have a value in this case.  Note that this assigns to
       the entire array, deleting any elements that do not appear in the list.

       To create an empty array (including associative arrays), use one of:

              set -A name
              name=()

   Array Subscripts
       Individual  elements  of an array may be selected using a subscript.  A
       subscript of the form ‘[exp]’ selects the single element exp, where exp
       is  an  arithmetic  expression  which  will  be  subject  to arithmetic
       expansion as if it were surrounded by  ‘$((...))’.   The  elements  are
       numbered beginning with 1, unless the KSH_ARRAYS option is set in which
       case they are numbered from zero.

       Subscripts may be used inside braces used to delimit a parameter  name,
       thus  ‘${foo[2]}’ is equivalent to ‘$foo[2]’.  If the KSH_ARRAYS option
       is set, the braced form is  the  only  one  that  works,  as  bracketed
       expressions otherwise are not treated as subscripts.

       The  same  subscripting  syntax  is used for associative arrays, except
       that no arithmetic expansion is applied to exp.  However,  the  parsing
       rules  for  arithmetic  expressions  still apply, which affects the way
       that certain special characters must be protected from  interpretation.
       See Subscript Parsing below for details.

       A  subscript of the form ‘[*]’ or ‘[@]’ evaluates to all elements of an
       array; there is no difference between the two except when  they  appear
       within  double  quotes.   ‘"$foo[*]"’  evaluates  to  ‘"$foo[1] $foo[2]
       ..."’, whereas ‘"$foo[@]"’ evaluates to ‘"$foo[1]" "$foo[2]" ...’.  For
       associative  arrays,  ‘[*]’  or ‘[@]’ evaluate to all the values, in no
       particular order.  Note that this does not substitute the keys; see the
       documentation  for  the  ‘k’  flag  under  Parameter Expansion Flags in
       zshexpn(1) for complete details.  When an array parameter is referenced
       as  ‘$name’  (with no subscript) it evaluates to ‘$name[*]’, unless the
       KSH_ARRAYS option is set in which case  it  evaluates  to  ‘${name[0]}’
       (for  an  associative array, this means the value of the key ‘0’, which
       may not exist even if there are values for other keys).

       A subscript of the form ‘[exp1,exp2]’ selects all elements in the range
       exp1  to  exp2, inclusive. (Associative arrays are unordered, and so do
       not support ranges.) If one of the subscripts evaluates to  a  negative
       number, say -n, then the nth element from the end of the array is used.
       Thus ‘$foo[-3]’ is the third element from the end of the array foo, and
       ‘$foo[1,-1]’ is the same as ‘$foo[*]’.

       Subscripting  may  also be performed on non-array values, in which case
       the subscripts specify a substring to be extracted.   For  example,  if
       FOO is set to ‘foobar’, then ‘echo $FOO[2,5]’ prints ‘ooba’.

   Array Element Assignment
       A subscript may be used on the left side of an assignment like so:

              name[exp]=value

       In  this  form  of  assignment the element or range specified by exp is
       replaced by the expression on the right side.  An  array  (but  not  an
       associative  array) may be created by assignment to a range or element.
       Arrays do not nest, so assigning a parenthesized list of values  to  an
       element  or range changes the number of elements in the array, shifting
       the other elements  to  accommodate  the  new  values.   (This  is  not
       supported for associative arrays.)

       This syntax also works as an argument to the typeset command:

              typeset "name[exp]"=value

       The  value  may  not  be  a  parenthesized  list  in  this  case;  only
       single-element assignments may be made with typeset.  Note that  quotes
       are  necessary  in  this  case  to  prevent  the  brackets  from  being
       interpreted as filename generation operators.   The  noglob  precommand
       modifier could be used instead.

       To delete an element of an ordinary array, assign ‘()’ to that element.
       To delete an element of an associative array, use the unset command:

              unset "name[exp]"

   Subscript Flags
       If the opening bracket, or the comma  in  a  range,  in  any  subscript
       expression  is  directly followed by an opening parenthesis, the string
       up to the matching closing one is considered to be a list of flags,  as
       in ‘name[(flags)exp]’.

       The  flags s, n and b take an argument; the delimiter is shown below as
       ‘:’, but  any  character,  or  the  matching  pairs  ‘(...)’,  ‘{...}’,
       ‘[...]’, or ‘<...>’, may be used.

       The flags currently understood are:

       w      If  the  parameter  subscripted is a scalar then this flag makes
              subscripting work on words instead of characters.   The  default
              word separator is whitespace.

       s:string:
              This  gives  the string that separates words (for use with the w
              flag).  The delimiter character : is arbitrary; see above.

       p      Recognize the same escape sequences as the print builtin in  the
              string argument of a subsequent ‘s’ flag.

       f      If  the  parameter  subscripted is a scalar then this flag makes
              subscripting work on lines  instead  of  characters,  i.e.  with
              elements  separated  by  newlines.   This  is  a  shorthand  for
              ‘pws:\n:’.

       r      Reverse subscripting: if this flag is given, the exp is taken as
              a  pattern  and  the result is the first matching array element,
              substring or word (if the parameter is an  array,  if  it  is  a
              scalar,  or  if  it  is  a  scalar  and  the  ‘w’ flag is given,
              respectively).  The subscript used is the number of the matching
              element, so that pairs of subscripts such as ‘$foo[(r)??,3]’ and
              ‘$foo[(r)??,(r)f*]’ are possible if  the  parameter  is  not  an
              associative  array.   If  the parameter is an associative array,
              only the value part of each pair is compared to the pattern, and
              the result is that value.

              If  a  search  through an ordinary array failed, the search sets
              the subscript to one past  the  end  of  the  array,  and  hence
              ${array[(r)pattern]} will substitute the empty string.  Thus the
              success of a search can be tested by using  the  (i)  flag,  for
              example (assuming the option KSH_ARRAYS is not in effect):

                     [[ ${array[(i)pattern]} -le ${#array} ]]

              If KSH_ARRAYS is in effect, the -le should be replaced by -lt.

              Note that in subscripts with both ‘r’ and ‘R’ pattern characters
              are active  even  if  they  were  substituted  for  a  parameter
              (regardless  of  the  setting  of GLOB_SUBST which controls this
              feature in normal pattern matching).  It is therefore  necessary
              to  quote pattern characters for an exact string match.  Given a
              string in $key, and assuming the EXTENDED_GLOB  option  is  set,
              the  following  is  sufficient  to  match an element of an array
              $array containing exactly the value of $key:

                     key2=${key//(#m)[\][()\\*?#<>~^]/\\$MATCH}
                     print ${array[(R)$key2]}

       R      Like ‘r’, but gives the last  match.   For  associative  arrays,
              gives  all  possible  matches.  May  be  used  for  assigning to
              ordinary array elements, but not for  assigning  to  associative
              arrays.

              Note  that  this  flag  can give odd results on failure.  For an
              ordinary array the item substituted  is  that  corresponding  to
              subscript 0.  If the option KSH_ARRAYS is not in effect, this is
              the same as the element corresponding to subscript  1,  although
              the  form  ${array[(I)pattern]}  will evaluate to 0 for a failed
              match.  If the option KSH_ARRAYS is in effect, the subscript  is
              still  0 for a failed match; this cannot be distinguished from a
              successful  match  without  testing  ${array[0]}   against   the
              pattern.

       i      Like ‘r’, but gives the index of the match instead; this may not
              be combined with a second argument.  On  the  left  side  of  an
              assignment,  behaves  like ‘r’.  For associative arrays, the key
              part of each pair is compared to  the  pattern,  and  the  first
              matching key found is the result.

              See ‘r’ for discussion of subscripts of failed matches.

       I      Like ‘i’, but gives the index of the last match, or all possible
              matching keys in an associative array.

              See ‘R’ for discussion of subscripts of failed matches.

       k      If used in a subscript on an associative array, this flag causes
              the  keys  to  be interpreted as patterns, and returns the value
              for the first key found where exp is matched by the  key.   This
              flag  does  not  work  on  the  left side of an assignment to an
              associative  array  element.   If  used  on  another   type   of
              parameter, this behaves like ‘r’.

       K      On  an associative array this is like ‘k’ but returns all values
              where exp is matched by the keys.  On other types of  parameters
              this has the same effect as ‘R’.

       n:expr:
              If  combined  with ‘r’, ‘R’, ‘i’ or ‘I’, makes them give the nth
              or nth last match (if  expr  evaluates  to  n).   This  flag  is
              ignored  when the array is associative.  The delimiter character
              : is arbitrary; see above.

       b:expr:
              If combined with ‘r’, ‘R’, ‘i’ or ‘I’, makes them begin  at  the
              nth  or  nth last element, word, or character (if expr evaluates
              to n).  This flag is ignored when the array is associative.  The
              delimiter character : is arbitrary; see above.

       e      This  flag has no effect and for ordinary arrays is retained for
              backward compatibility only.  For associative arrays, this  flag
              can  be  used  to force * or @ to be interpreted as a single key
              rather than as a reference to all values.  This flag may be used
              on the left side of an assignment.

       See  Parameter  Expansion  Flags  (zshexpn(1))  for  additional ways to
       manipulate the results of array subscripting.

   Subscript Parsing
       This discussion applies mainly to associative array key strings and  to
       patterns used for reverse subscripting (the ‘r’, ‘R’, ‘i’, etc. flags),
       but it may also affect parameter substitutions that appear as  part  of
       an arithmetic expression in an ordinary subscript.

       It  is  possible  to  avoid  the  use  of  subscripts in assignments to
       associative array elements by using the syntax:

                 aa+=(key with "*strange*" characters’ ’value string)

       This adds a new key/value pair if the key is not already  present,  and
       replaces the value for the existing key if it is.

       The  basic rule to remember when writing a subscript expression is that
       all text between the opening ‘[’ and the closing ‘]’ is interpreted  as
       if  it  were in double quotes (see zshmisc(1)).  However, unlike double
       quotes which normally cannot nest,  subscript  expressions  may  appear
       inside  double-quoted strings or inside other subscript expressions (or
       both!), so the rules have two important differences.

       The first difference is that brackets (‘[’  and  ‘]’)  must  appear  as
       balanced  pairs in a subscript expression unless they are preceded by a
       backslash (‘\’).  Therefore, within a subscript expression (and  unlike
       true  double-quoting) the sequence ‘\[’ becomes ‘[’, and similarly ‘\]’
       becomes ‘]’.  This applies even in  cases  where  a  backslash  is  not
       normally  required;  for  example,  the  pattern  ‘[^[]’  (to match any
       character other than an open bracket) should be written  ‘[^\[]’  in  a
       reverse-subscript  pattern.   However,  note  that  ‘\[^\[\]’  and even
       ‘\[^[]’ mean the same thing, because backslashes  are  always  stripped
       when they appear before brackets!

       The  same rule applies to parentheses (‘(’ and ‘)’) and braces (‘{’ and
       ‘}’): they must appear either  in  balanced  pairs  or  preceded  by  a
       backslash,  and  backslashes  that  protect  parentheses  or braces are
       removed during parsing.  This is because parameter  expansions  may  be
       surrounded  balanced  braces,  and  subscript  flags  are introduced by
       balanced parenthesis.

       The second difference is that a double-quote (‘"’) may appear  as  part
       of  a  subscript  expression without being preceded by a backslash, and
       therefore that the two characters ‘\"’ remain as two characters in  the
       subscript (in true double-quoting, ‘\"’ becomes ‘"’).  However, because
       of the standard shell quoting rules, any double-quotes that appear must
       occur  in balanced pairs unless preceded by a backslash.  This makes it
       more difficult to write a subscript expression  that  contains  an  odd
       number  of  double-quote characters, but the reason for this difference
       is  so  that  when  a  subscript   expression   appears   inside   true
       double-quotes, one can still write ‘\"’ (rather than ‘\\\"’) for ‘"’.

       To  use  an  odd number of double quotes as a key in an assignment, use
       the typeset builtin and an enclosing pair of double quotes; to refer to
       the value of that key, again use double quotes:

              typeset -A aa
              typeset "aa[one\"two\"three\"quotes]"=QQQ
              print "$aa[one\"two\"three\"quotes]"

       It  is  important  to  note that the quoting rules do not change when a
       parameter expansion with a subscript is nested inside another subscript
       expression.  That is, it is not necessary to use additional backslashes
       within the inner subscript expression; they are removed only once, from
       the  innermost  subscript  outwards.  Parameters are also expanded from
       the innermost subscript first, as each expansion is encountered left to
       right in the outer expression.

       A  further complication arises from a way in which subscript parsing is
       not different from double quote parsing.  As  in  true  double-quoting,
       the  sequences ‘\*’, and ‘\@’ remain as two characters when they appear
       in a subscript  expression.   To  use  a  literal  ‘*’  or  ‘@’  as  an
       associative array key, the ‘e’ flag must be used:

              typeset -A aa
              aa[(e)*]=star
              print $aa[(e)*]

       A   last  detail  must  be  considered  when  reverse  subscripting  is
       performed.  Parameters appearing in the subscript expression are  first
       expanded  and then the complete expression is interpreted as a pattern.
       This has two effects: first, parameters behave as if GLOB_SUBST were on
       (and  it  cannot  be  turned  off); second, backslashes are interpreted
       twice, once when parsing the array subscript and again when parsing the
       pattern.    In   a  reverse  subscript,  it’s  necessary  to  use  four
       backslashes to cause a single  backslash  to  match  literally  in  the
       pattern.   For  complex  patterns,  it  is  often easiest to assign the
       desired pattern to a parameter and then refer to that parameter in  the
       subscript,  because  then the backslashes, brackets, parentheses, etc.,
       are seen only when the complete expression is converted to  a  pattern.
       To  match  the  value  of a parameter literally in a reverse subscript,
       rather than as a pattern, use ‘${(q)name}’ (see  zshexpn(1))  to  quote
       the expanded value.

       Note  that  the  ‘k’  and  ‘K’  flags  are  reverse subscripting for an
       ordinary array, but are not reverse  subscripting  for  an  associative
       array!   (For  an  associative  array, the keys in the array itself are
       interpreted as patterns by those flags; the subscript is a plain string
       in that case.)

       One final note, not directly related to subscripting: the numeric names
       of positional parameters (described below) are parsed specially, so for
       example   ‘$2foo’  is  equivalent  to  ‘${2}foo’.   Therefore,  to  use
       subscript syntax to extract a substring from  a  positional  parameter,
       the  expansion  must  be surrounded by braces; for example, ‘${2[3,5]}’
       evaluates  to  the  third  through  fifth  characters  of  the   second
       positional  parameter,  but  ‘$2[3,5]’  is  the entire second parameter
       concatenated with the filename generation pattern ‘[3,5]’.

POSITIONAL PARAMETERS

       The positional parameters provide access to the command-line  arguments
       of a shell function, shell script, or the shell itself; see the section
       ‘Invocation’, and also the section ‘Functions’.  The parameter n, where
       n  is  a  number, is the nth positional parameter.  The parameters *, @
       and argv are arrays containing  all  the  positional  parameters;  thus
       ‘$argv[n]’, etc., is equivalent to simply ‘$n’.

       Positional parameters may be changed after the shell or function starts
       by using the set builtin, by assigning to the argv array, or by  direct
       assignment  of  the  form  ‘n=value’  where  n  is  the  number  of the
       positional parameter to be changed.   This  also  creates  (with  empty
       values)  any  of  the  positions  from  1 to n that do not already have
       values.  Note that, because the positional parameters form an array, an
       array  assignment  of  the form ‘n=(value ...)’ is allowed, and has the
       effect of shifting all the values at positions greater  than  n  by  as
       many positions as necessary to accommodate the new values.

LOCAL PARAMETERS

       Shell   function   executions  delimit  scopes  for  shell  parameters.
       (Parameters are dynamically scoped.)   The  typeset  builtin,  and  its
       alternative  forms  declare,  integer,  local  and  readonly  (but  not
       export), can be used to declare a  parameter  as  being  local  to  the
       innermost scope.

       When  a  parameter  is  read  or  assigned  to,  the innermost existing
       parameter of that name is used.  (That is, the  local  parameter  hides
       any  less-local  parameter.)   However,  assigning  to  a  non-existent
       parameter, or declaring a new parameter with export, causes  it  to  be
       created in the outermost scope.

       Local parameters disappear when their scope ends.  unset can be used to
       delete a parameter while it is still in scope; any outer  parameter  of
       the same name remains hidden.

       Special  parameters  may  also be made local; they retain their special
       attributes unless either the existing or  the  newly-created  parameter
       has  the  -h (hide) attribute.  This may have unexpected effects: there
       is no default value, so if there is no  assignment  at  the  point  the
       variable  is  made  local, it will be set to an empty value (or zero in
       the case of integers).  The following:

              typeset PATH=/new/directory:$PATH

       is valid for temporarily allowing the shell or programmes  called  from
       it to find the programs in /new/directory inside a function.

       Note  that  the  restriction  in  older  versions  of  zsh  that  local
       parameters were never exported has been removed.

PARAMETERS SET BY THE SHELL

       The following parameters are automatically set by the shell:

       ! <S>  The process ID of the last command  started  in  the  background
              with &, or put into the background with the bg builtin.

       # <S>  The  number of positional parameters in decimal.  Note that some
              confusion may occur with the syntax  $#param  which  substitutes
              the  length  of  param.   Use  ${#}  to resolve ambiguities.  In
              particular, the sequence ‘$#-...’ in an arithmetic expression is
              interpreted as the length of the parameter -, q.v.

       ARGC <S> <Z>
              Same as #.

       $ <S>  The  process  ID  of  this  shell.  Note that this indicates the
              original shell started by invoking  zsh;  all  processes  forked
              from  the  shells  without  executing  a  new  program,  such as
              subshells started by (...), substitute the same value.

       - <S>  Flags supplied to the shell on  invocation  or  by  the  set  or
              setopt commands.

       * <S>  An array containing the positional parameters.

       argv <S> <Z>
              Same  as  *.   Assigning  to  argv  changes the local positional
              parameters, but argv is not itself a local parameter.   Deleting
              argv  with unset in any function deletes it everywhere, although
              only the innermost positional parameter array is deleted  (so  *
              and @ in other scopes are not affected).

       @ <S>  Same as argv[@], even when argv is not set.

       ? <S>  The exit status returned by the last command.

       0 <S>  The   name   used   to   invoke   the  current  shell.   If  the
              FUNCTION_ARGZERO option is set, this is set temporarily within a
              shell function to the name of the function, and within a sourced
              script to the name of the script.

       status <S> <Z>
              Same as ?.

       pipestatus <S> <Z>
              An array containing the exit statuses returned by  all  commands
              in the last pipeline.

       _ <S>  The last argument of the previous command.  Also, this parameter
              is set in the environment of every command executed to the  full
              pathname of the command.

       CPUTYPE
              The  machine  type  (microprocessor  class or machine model), as
              determined at run time.

       EGID <S>
              The effective group ID  of  the  shell  process.   If  you  have
              sufficient  privileges, you may change the effective group ID of
              the  shell  process  by  assigning  to  this  parameter.    Also
              (assuming sufficient privileges), you may start a single command
              with a different effective group ID by ‘(EGID=gid; command)EUID <S>
              The effective user  ID  of  the  shell  process.   If  you  have
              sufficient  privileges,  you may change the effective user ID of
              the  shell  process  by  assigning  to  this  parameter.    Also
              (assuming sufficient privileges), you may start a single command
              with a different effective user ID by ‘(EUID=uid; command)ERRNO <S>
              The value of errno (see errno(3)) as set by  the  most  recently
              failed  system  call.   This  value  is  system dependent and is
              intended for debugging purposes.  It is  also  useful  with  the
              zsh/system  module  which  allows the number to be turned into a
              name or message.

       GID <S>
              The real group ID of the shell process.  If you have  sufficient
              privileges,  you may change the group ID of the shell process by
              assigning  to  this  parameter.    Also   (assuming   sufficient
              privileges),  you  may  start a single command under a different
              group ID by ‘(GID=gid; command)HISTCMD
              The current history line number  in  an  interactive  shell,  in
              other words the line number for the command that caused $HISTCMD
              to be read.

       HOST   The current hostname.

       LINENO <S>
              The line number of the current line within the  current  script,
              sourced  file,  or  shell function being executed, whichever was
              started most recently.  Note that in the case of shell functions
              the  line  number  refers  to the function as it appeared in the
              original  definition,  not  necessarily  as  displayed  by   the
              functions builtin.

       LOGNAME
              If  the  corresponding variable is not set in the environment of
              the shell, it is initialized to the login name corresponding  to
              the current login session. This parameter is exported by default
              but this can be disabled using the typeset builtin.

       MACHTYPE
              The machine type (microprocessor class  or  machine  model),  as
              determined at compile time.

       OLDPWD The  previous  working  directory.   This  is set when the shell
              initializes and whenever the directory changes.

       OPTARG <S>
              The value of the last option argument processed by  the  getopts
              command.

       OPTIND <S>
              The  index  of the last option argument processed by the getopts
              command.

       OSTYPE The operating system, as determined at compile time.

       PPID <S>
              The process ID of the parent of the shell.  As for $$, the value
              indicates  the  parent of the original shell and does not change
              in subshells.

       PWD    The present working directory.   This  is  set  when  the  shell
              initializes and whenever the directory changes.

       RANDOM <S>
              A  pseudo-random  integer  from 0 to 32767, newly generated each
              time this parameter is referenced.  The random number  generator
              can be seeded by assigning a numeric value to RANDOM.

              The   values   of   RANDOM   form   an  intentionally-repeatable
              pseudo-random sequence; subshells  that  reference  RANDOM  will
              result  in  identical  pseudo-random  values unless the value of
              RANDOM is referenced or seeded in the parent  shell  in  between
              subshell invocations.

       SECONDS <S>
              The number of seconds since shell invocation.  If this parameter
              is assigned a value, then the value returned upon reference will
              be  the value that was assigned plus the number of seconds since
              the assignment.

              Unlike  other  special  parameters,  the  type  of  the  SECONDS
              parameter  can  be  changed  using  the  typeset  command.  Only
              integer and one of the floating point types  are  allowed.   For
              example, ‘typeset -F SECONDS’ causes the value to be reported as
              a floating point number.  The precision is six  decimal  places,
              although not all places may be useful.

       SHLVL <S>
              Incremented by one each time a new shell is started.

       signals
              An array containing the names of the signals.

       TRY_BLOCK_ERROR <S>
              In an always block, indicates whether the preceding list of code
              caused an error.  The  value  is  1  to  indicate  an  error,  0
              otherwise.   It may be reset, clearing the error condition.  See
              Complex Commands in zshmisc(1)

       TTY    The name of the tty associated with the shell, if any.

       TTYIDLE <S>
              The idle time of the tty associated with the shell in seconds or
              -1 if there is no such tty.

       UID <S>
              The  real  user ID of the shell process.  If you have sufficient
              privileges, you may change the user ID of the shell by assigning
              to  this  parameter.  Also (assuming sufficient privileges), you
              may start  a  single  command  under  a  different  user  ID  by
              ‘(UID=uid; command)USERNAME <S>
              The  username  corresponding  to  the  real user ID of the shell
              process.  If you have sufficient privileges, you may change  the
              username  (and  also  the  user ID and group ID) of the shell by
              assigning  to  this  parameter.    Also   (assuming   sufficient
              privileges),  you  may  start a single command under a different
              username (and user ID  and  group  ID)  by  ‘(USERNAME=username;
              command)VENDOR The vendor, as determined at compile time.

       ZSH_NAME
              Expands  to  the  basename  of  the  command used to invoke this
              instance of zsh.

       ZSH_VERSION
              The version number of this zsh.

PARAMETERS USED BY THE SHELL

       The following parameters are used by the shell.

       In cases where there are two parameters with an  upper-  and  lowercase
       form  of the same name, such as path and PATH, the lowercase form is an
       array and the uppercase form is a scalar with the elements of the array
       joined  together  by  colons.   These  are  similar  to tied parameters
       created via ‘typeset -T’.  The normal use for the colon-separated  form
       is  for exporting to the environment, while the array form is easier to
       manipulate within the shell.  Note that unsetting either  of  the  pair
       will  unset  the  other;  they  retain  their  special  properties when
       recreated, and recreating one of the pair will recreate the other.

       ARGV0  If exported, its value  is  used  as  the  argv[0]  of  external
              commands.    Usually   used   in  constructs  like  ‘ARGV0=emacs
              nethack’.

       BAUD   The rate in bits per second at which data reaches the  terminal.
              The line editor will use this value in order to compensate for a
              slow  terminal  by  delaying  updates  to  the   display   until
              necessary.   If  the parameter is unset or the value is zero the
              compensation mechanism is turned off.  The parameter is not  set
              by default.

              This parameter may be profitably set in some circumstances, e.g.
              for slow modems dialing into a communications server,  or  on  a
              slow  wide  area  network.  It should be set to the baud rate of
              the slowest part of the link for best performance.

       cdpath <S> <Z> (CDPATH <S>)
              An array (colon-separated list) of  directories  specifying  the
              search path for the cd command.

       COLUMNS <S>
              The  number  of  columns  for  this  terminal session.  Used for
              printing select lists and for the line editor.

       DIRSTACKSIZE
              The maximum size of the directory  stack.   If  the  stack  gets
              larger  than  this, it will be truncated automatically.  This is
              useful with the AUTO_PUSHD option.

       ENV    If the ENV environment variable is set when zsh is invoked as sh
              or ksh, $ENV is sourced after the profile scripts.  The value of
              ENV is subjected to parameter expansion,  command  substitution,
              and arithmetic expansion before being interpreted as a pathname.
              Note that ENV is not used unless zsh is emulating sh or ksh.

       FCEDIT The default editor for the fc builtin.  If FCEDIT  is  not  set,
              the  parameter  EDITOR  is  used;  if  that is not set either, a
              builtin default, usually vi, is used.

       fignore <S> <Z> (FIGNORE <S>)
              An array (colon separated list) containing the suffixes of files
              to   be   ignored   during  filename  completion.   However,  if
              completion only generates files with suffixes in this list, then
              these files are completed anyway.

       fpath <S> <Z> (FPATH <S>)
              An  array  (colon  separated list) of directories specifying the
              search path for function definitions.   This  path  is  searched
              when  a  function  with  the  -u attribute is referenced.  If an
              executable file is found, then it is read and  executed  in  the
              current environment.

       histchars <S>
              Three  characters  used  by  the  shell’s  history  and  lexical
              analysis mechanism.  The first character signals the start of  a
              history  expansion  (default ‘!’).  The second character signals
              the start of a quick history substitution  (default  ‘^’).   The
              third character is the comment character (default ‘#’).

              The  characters  must be in the ASCII character set; any attempt
              to set histchars to characters with a  locale-dependent  meaning
              will be rejected with an error message.

       HISTCHARS <S> <Z>
              Same as histchars.  (Deprecated.)

       HISTFILE
              The file to save the history in when an interactive shell exits.
              If unset, the history is not saved.

       HISTSIZE <S>
              The maximum number of events  stored  in  the  internal  history
              list.   If  you  use  the HIST_EXPIRE_DUPS_FIRST option, setting
              this value larger than the  SAVEHIST  size  will  give  you  the
              difference as a cushion for saving duplicated history events.

       HOME <S>
              The  default  argument  for  the  cd  command.   This is not set
              automatically by the shell in sh, ksh or csh emulation,  but  it
              is  typically  present  in  the  environment  anyway,  and if it
              becomes set it has its usual special behaviour.

       IFS <S>
              Internal field separators (by default space,  tab,  newline  and
              NUL),  that are used to separate words which result from command
              or parameter expansion and words read by the read builtin.   Any
              characters  from  the  set space, tab and newline that appear in
              the IFS are called IFS white space.  One or more IFS white space
              characters  or  one  non-IFS white space character together with
              any adjacent IFS white space character delimit a field.   If  an
              IFS  white  space  character  appears twice consecutively in the
              IFS, this character is treated as if it were not  an  IFS  white
              space character.

       KEYTIMEOUT
              The  time the shell waits, in hundredths of seconds, for another
              key to be pressed when reading bound multi-character  sequences.

       LANG <S>
              This  variable  determines  the locale category for any category
              not specifically selected via a variable starting with ‘LC_’.

       LC_ALL <S>
              This variable overrides the value of the ‘LANG’ variable and the
              value of any of the other variables starting with ‘LC_’.

       LC_COLLATE <S>
              This  variable  determines  the  locale  category  for character
              collation information within ranges in  glob  brackets  and  for
              sorting.

       LC_CTYPE <S>
              This  variable  determines  the  locale  category  for character
              handling functions.

       LC_MESSAGES <S>
              This variable determines the language in which  messages  should
              be written.  Note that zsh does not use message catalogs.

       LC_NUMERIC <S>
              This  variable affects the decimal point character and thousands
              separator character for the formatted input/output functions and
              string conversion functions.  Note that zsh ignores this setting
              when parsing floating point mathematical expressions.

       LC_TIME <S>
              This variable determines the locale category for date  and  time
              formatting in prompt escape sequences.

       LINES <S>
              The  number  of  lines  for  this  terminal  session.   Used for
              printing select lists and for the line editor.

       LISTMAX
              In the line editor, the number of matches to list without asking
              first.  If  the  value is negative, the list will be shown if it
              spans at most as many lines as given by the absolute value.   If
              set to zero, the shell asks only if the top of the listing would
              scroll off the screen.

       LOGCHECK
              The interval in seconds between checks for login/logout activity
              using the watch parameter.

       MAIL   If  this  parameter  is  set  and mailpath is not set, the shell
              looks for mail in the specified file.

       MAILCHECK
              The interval in seconds between checks for new mail.

       mailpath <S> <Z> (MAILPATH <S>)
              An array (colon-separated list) of filenames to  check  for  new
              mail.  Each filename can be followed by a ‘?’ and a message that
              will be printed.  The message will undergo parameter  expansion,
              command  substitution and arithmetic expansion with the variable
              $_ defined as the name  of  the  file  that  has  changed.   The
              default  message  is  ‘You  have  new mail’.  If an element is a
              directory instead of a file the  shell  will  recursively  check
              every file in every subdirectory of the element.

       manpath <S> <Z> (MANPATH <S> <Z>)
              An  array  (colon-separated list) whose value is not used by the
              shell.  The manpath array can be useful, however, since  setting
              it also sets MANPATH, and vice versa.

       module_path <S> <Z> (MODULE_PATH <S>)
              An  array  (colon-separated  list)  of directories that zmodload
              searches for dynamically loadable modules.  This is  initialized
              to          a         standard         pathname,         usually
              ‘/usr/local/lib/zsh/$ZSH_VERSION’.  (The  ‘/usr/local/lib’  part
              varies   from   installation  to  installation.)   For  security
              reasons, any value set in the  environment  when  the  shell  is
              started will be ignored.

              These parameters only exist if the installation supports dynamic
              module loading.

       NULLCMD <S>
              The command name to assume if a redirection is specified with no
              command.   Defaults to cat.  For sh/ksh behavior, change this to
              :.  For csh-like behavior, unset this parameter; the shell  will
              print an error message if null commands are entered.

       path <S> <Z> (PATH <S>)
              An  array  (colon-separated  list)  of directories to search for
              commands.  When this parameter is set, each directory is scanned
              and all files found are put in a hash table.

       POSTEDIT <S>
              This  string  is  output  whenever  the  line  editor exits.  It
              usually contains termcap strings to reset the terminal.

       PROMPT <S> <Z>
       PROMPT2 <S> <Z>
       PROMPT3 <S> <Z>
       PROMPT4 <S> <Z>
              Same as PS1, PS2, PS3 and PS4, respectively.

       prompt <S> <Z>
              Same as PS1.

       PS1 <S>
              The primary prompt string, printed before  a  command  is  read.
              the  default  is  ‘%m%#  ’.   It  undergoes  a  special  form of
              expansion  before  being  displayed;  see  the  section  ‘Prompt
              Expansion’.

       PS2 <S>
              The   secondary  prompt,  printed  when  the  shell  needs  more
              information to complete a command.  It is expanded in  the  same
              way  as  PS1.   The  default is ‘%_> ’, which displays any shell
              constructs  or  quotation  marks  which  are   currently   being
              processed.

       PS3 <S>
              Selection  prompt  used within a select loop.  It is expanded in
              the same way as PS1.  The default is ‘?# ’.

       PS4 <S>
              The execution  trace  prompt.   Default  is  ‘+%N:%i>  ’,  which
              displays  the  name  of the current shell structure and the line
              number within it.  In sh or ksh emulation, the default is ‘+  ’.

       psvar <S> <Z> (PSVAR <S>)
              An  array  (colon-separated list) whose first nine values can be
              used in PROMPT strings.  Setting psvar also sets PSVAR, and vice
              versa.

       READNULLCMD <S>
              The  command  name  to  assume  if a single input redirection is
              specified with no command.  Defaults to more.

       REPORTTIME
              If  nonnegative,  commands  whose  combined  user   and   system
              execution  times  (measured  in  seconds)  are greater than this
              value have timing statistics printed for them.

       REPLY  This parameter is reserved by convention to pass  string  values
              between  shell  scripts and shell builtins in situations where a
              function call or redirection are impossible or undesirable.  The
              read  builtin  and the select complex command may set REPLY, and
              filename generation  both  sets  and  examines  its  value  when
              evaluating  certain expressions.  Some modules also employ REPLY
              for similar purposes.

       reply  As REPLY, but for array values rather than strings.

       RPROMPT <S>
       RPS1 <S>
              This prompt is displayed on the right-hand side  of  the  screen
              when  the  primary  prompt is being displayed on the left.  This
              does not work  if  the  SINGLELINEZLE  option  is  set.   It  is
              expanded in the same way as PS1.

       RPROMPT2 <S>
       RPS2 <S>
              This  prompt  is  displayed on the right-hand side of the screen
              when the secondary prompt is being displayed on the left.   This
              does  not  work  if  the  SINGLELINEZLE  option  is  set.  It is
              expanded in the same way as PS2.

       SAVEHIST
              The maximum number of history events  to  save  in  the  history
              file.

       SPROMPT <S>
              The  prompt  used  for  spelling  correction.  The sequence ‘%R’
              expands  to  the  string   which   presumably   needs   spelling
              correction,  and  ‘%r’  expands to the proposed correction.  All
              other prompt escapes are also allowed.

       STTY   If this parameter is set in a command’s environment,  the  shell
              runs  the  stty  command  with  the  value  of this parameter as
              arguments in order to set up the terminal before  executing  the
              command. The modes apply only to the command, and are reset when
              it finishes or is suspended. If the  command  is  suspended  and
              continued  later  with  the  fg or wait builtins it will see the
              modes specified by STTY, as if  it  were  not  suspended.   This
              (intentionally)  does  not apply if the command is continued via
              ‘kill -CONT’.  STTY is ignored if the  command  is  run  in  the
              background,  or if it is in the environment of the shell but not
              explicitly assigned to in the input line.  This  avoids  running
              stty  at  every  external  command by accidentally exporting it.
              Also  note  that  STTY  should  not  be  used  for  window  size
              specifications; these will not be local to the command.

       TERM <S>
              The  type  of  terminal  in  use.   This is used when looking up
              termcap  sequences.   An  assignment  to  TERM  causes  zsh   to
              re-initialize  the  terminal,  even if the value does not change
              (e.g.,  ‘TERM=$TERM’).   It  is  necessary  to  make   such   an
              assignment  upon  any change to the terminal definition database
              or terminal type in order for the new settings to take effect.

       TIMEFMT
              The format of process time reports with the time  keyword.   The
              default is ‘%E real  %U user  %S system  %P %J’.  Recognizes the
              following escape sequences, although not all may be available on
              all systems, and some that are available may not be useful:

              %%     A ‘%’.
              %U     CPU seconds spent in user mode.
              %S     CPU seconds spent in kernel mode.
              %E     Elapsed time in seconds.
              %P     The CPU percentage, computed as (100*%U+%S)/%E.
              %W     Number of times the process was swapped.
              %X     The average amount in (shared) text space used in Kbytes.
              %D     The average amount in (unshared) data/stack space used in
                     Kbytes.
              %K     The total space used (%X+%D) in Kbytes.
              %M     The  maximum memory the process had in use at any time in
                     Kbytes.
              %F     The number of  major  page  faults  (page  needed  to  be
                     brought from disk).
              %R     The number of minor page faults.
              %I     The number of input operations.
              %O     The number of output operations.
              %r     The number of socket messages received.
              %s     The number of socket messages sent.
              %k     The number of signals received.
              %w     Number of voluntary context switches (waits).
              %c     Number of involuntary context switches.
              %J     The name of this job.

              A  star  may  be  inserted  between  the  percent sign and flags
              printing  time.   This  cause  the  time  to   be   printed   in
              ‘hh:mm:ss.ttt’  format  (hours  and  minutes are only printed if
              they are not zero).

       TMOUT  If this parameter is nonzero, the shell  will  receive  an  ALRM
              signal  if  a command is not entered within the specified number
              of seconds after issuing  a  prompt.  If  there  is  a  trap  on
              SIGALRM,  it will be executed and a new alarm is scheduled using
              the value of the TMOUT parameter after executing the  trap.   If
              no  trap  is  set, and the idle time of the terminal is not less
              than  the  value  of  the  TMOUT  parameter,   zsh   terminates.
              Otherwise  a  new  alarm is scheduled to TMOUT seconds after the
              last keypress.

       TMPPREFIX
              A pathname prefix which the shell will  use  for  all  temporary
              files.   Note  that  this should include an initial part for the
              file name as well  as  any  directory  names.   The  default  is
              ‘/tmp/zsh’.

       watch <S> <Z> (WATCH <S>)
              An  array  (colon-separated  list)  of  login/logout  events  to
              report.   If  it  contains  the  single  word  ‘all’,  then  all
              login/logout  events  are  reported.   If it contains the single
              word ‘notme’, then all events are reported as with ‘all’  except
              $USERNAME.   An entry in this list may consist of a username, an
              ‘@’ followed by a remote hostname, and a ‘%’ followed by a  line
              (tty).   Any  or  all  of  these components may be present in an
              entry; if a login/logout  event  matches  all  of  them,  it  is
              reported.

       WATCHFMT
              The  format  of  login/logout  reports if the watch parameter is
              set.  Default is  ‘%n  has  %a  %l  from  %m’.   Recognizes  the
              following escape sequences:

              %n     The name of the user that logged in/out.

              %a     The observed action, i.e. "logged on" or "logged off".

              %l     The line (tty) the user is logged in on.

              %M     The full hostname of the remote host.

              %m     The hostname up to the first ‘.’.  If only the IP address
                     is available or the utmp field contains the  name  of  an
                     X-windows display, the whole name is printed.

                     NOTE:  The  ‘%m’ and ‘%M’ escapes will work only if there
                     is a host  name  field  in  the  utmp  on  your  machine.
                     Otherwise they are treated as ordinary strings.

              %S (%s)
                     Start (stop) standout mode.

              %U (%u)
                     Start (stop) underline mode.

              %B (%b)
                     Start (stop) boldface mode.

              %t
              %@     The time, in 12-hour, am/pm format.

              %T     The time, in 24-hour format.

              %w     The date in ‘day-dd’ format.

              %W     The date in ‘mm/dd/yy’ format.

              %D     The date in ‘yy-mm-dd’ format.

              %(x:true-text:false-text)
                     Specifies  a ternary expression.  The character following
                     the x  is  arbitrary;  the  same  character  is  used  to
                     separate the text for the "true" result from that for the
                     "false"  result.   Both  the  separator  and  the   right
                     parenthesis  may  be  escaped  with a backslash.  Ternary
                     expressions may be nested.

                     The test character x may be any one of ‘l’, ‘n’,  ‘m’  or
                     ‘M’,  which indicate a ‘true’ result if the corresponding
                     escape sequence would return a non-empty value; or it may
                     be  ‘a’,  which  indicates a ‘true’ result if the watched
                     user has logged in, or ‘false’  if  he  has  logged  out.
                     Other  characters evaluate to neither true nor false; the
                     entire expression is omitted in this case.

                     If the result is ‘true’, then the true-text is  formatted
                     according  to  the  rules  above  and  printed,  and  the
                     false-text is skipped.   If  ‘false’,  the  true-text  is
                     skipped  and  the  false-text  is  formatted and printed.
                     Either or both of the branches may  be  empty,  but  both
                     separators must be present in any case.

       WORDCHARS <S>
              A  list of non-alphanumeric characters considered part of a word
              by the line editor.

       ZBEEP  If set, this gives a string of characters, which can use all the
              same  codes  as  the bindkey command as described in the zsh/zle
              module entry in  zshmodules(1),  that  will  be  output  to  the
              terminal instead of beeping.  This may have a visible instead of
              an audible effect; for example, the string ‘\e[?5h\e[?5l’  on  a
              vt100 or xterm will have the effect of flashing reverse video on
              and off (if you usually use reverse video, you  should  use  the
              string  ‘\e[?5l\e[?5h’ instead).  This takes precedence over the
              NOBEEP option.

       ZDOTDIR
              The directory to search for shell startup files  (.zshrc,  etc),
              if not $HOME.