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ZSHMISC(1)							    ZSHMISC(1)

NAME
       zshmisc - everything and then some

SIMPLE COMMANDS & PIPELINES
       A  simple  command is a sequence of optional parameter assignments fol‐
       lowed by	 blank-separated  words,  with	optional  redirections	inter‐
       spersed.	 The first word is the command to be executed, and the remain‐
       ing words, if any, are arguments to the command.	 If a command name  is
       given,  the parameter assignments modify the environment of the command
       when it is executed.  The value of a simple command is its exit status,
       or 128 plus the signal number if terminated by a signal.	 For example,

	      echo foo

       is a simple command with arguments.

       A  pipeline  is	either	a simple command, or a sequence of two or more
       simple commands where each command is separated from the next by `|' or
       `|&'.   Where commands are separated by `|', the standard output of the
       first command is connected to the standard input of the next.  `|&'  is
       shorthand for `2>&1 |', which connects both the standard output and the
       standard error of the command to the standard input of the  next.   The
       value  of a pipeline is the value of the last command, unless the pipe‐
       line is preceded by `!' in which case the value is the logical  inverse
       of the value of the last command.  For example,

	      echo foo | sed 's/foo/bar/'

       is  a  pipeline,	 where	the output (`foo' plus a newline) of the first
       command will be passed to the input of the second.

       If a pipeline is preceded by `coproc', it is executed as a coprocess; a
       two-way pipe is established between it and the parent shell.  The shell
       can read from or write to the coprocess by means of the `>&p' and `<&p'
       redirection  operators  or  with	 `print -p' and `read -p'.  A pipeline
       cannot be preceded by both `coproc' and `!'.  If job control is active,
       the coprocess can be treated in other than input and output as an ordi‐
       nary background job.

       A sublist is either a single pipeline, or a sequence  of	 two  or  more
       pipelines separated by `&&' or `||'.  If two pipelines are separated by
       `&&', the second pipeline  is  executed	only  if  the  first  succeeds
       (returns	 a  zero  value).  If two pipelines are separated by `||', the
       second is executed only if the first fails (returns a  nonzero  value).
       Both  operators	have  equal  precedence and are left associative.  The
       value of the sublist is the value of the last pipeline  executed.   For
       example,

	      dmesg | grep panic && print yes

       is a sublist consisting of two pipelines, the second just a simple com‐
       mand which will be executed if and only if the grep command  returns  a
       zero  value.   If  it does not, the value of the sublist is that return
       value, else it is the value returned by	the  print  (almost  certainly
       zero).

       A list is a sequence of zero or more sublists, in which each sublist is
       terminated by `;', `&', `&|', `&!', or a newline.  This terminator  may
       optionally  be  omitted from the last sublist in the list when the list
       appears as a complex command inside `(...)'  or `{...}'.	 When  a  sub‐
       list  is terminated by `;' or newline, the shell waits for it to finish
       before executing the next sublist.  If a sublist	 is  terminated	 by  a
       `&',  `&|',  or `&!', the shell executes the last pipeline in it in the
       background, and does not wait for it to	finish	(note  the  difference
       from  other  shells which execute the whole sublist in the background).
       A backgrounded pipeline returns a status of zero.

       More generally, a list can be seen as a set of any shell commands what‐
       soever,	including the complex commands below; this is implied wherever
       the word `list' appears in later descriptions.  For example,  the  com‐
       mands in a shell function form a special sort of list.

PRECOMMAND MODIFIERS
       A  simple  command may be preceded by a precommand modifier, which will
       alter how the  command  is  interpreted.	  These	 modifiers  are	 shell
       builtin	commands  with	the exception of nocorrect which is a reserved
       word.

       -      The command is executed with a  `-'  prepended  to  its  argv[0]
	      string.

       noglob Filename	generation  (globbing)	is not performed on any of the
	      words.

       nocorrect
	      Spelling correction is not done on any of the words.  This  must
	      appear  before  any  other  precommand modifier, as it is inter‐
	      preted immediately, before any  parsing  is  done.   It  has  no
	      effect in non-interactive shells.

       exec   The command is executed in the parent shell without forking.

       command
	      The command word is taken to be the name of an external command,
	      rather than a shell function or builtin.

       builtin
	      The command word is taken to be the name of a  builtin  command,
	      rather than a shell function or external command.

COMPLEX COMMANDS
       A complex command in zsh is one of the following:

       if list then list [ elif list then list ] ... [ else list ] fi
	      The  if  list is executed, and if it returns a zero exit status,
	      the then list is executed.  Otherwise, the elif list is executed
	      and  if  its  value is zero, the then list is executed.  If each
	      elif list returns nonzero, the else list is executed.

       for name [ in word ... term ] do list done
	      where term is at least one newline or ;.	 Expand	 the  list  of
	      words,  and set the parameter name to each of them in turn, exe‐
	      cuting list each time.  If the in word is omitted, use the posi‐
	      tional parameters instead of the words.

       for (( [expr1] ; [expr2] ; [expr3] )) do list done
	      The arithmetic expression expr1 is evaluated first (see the sec‐
	      tion `Arithmetic Evaluation').  The arithmetic expression	 expr2
	      is  repeatedly  evaluated	 until	it  evaluates to zero and when
	      non-zero, list is executed and the arithmetic  expression	 expr3
	      evaluated.   If any expression is omitted, then it behaves as if
	      it evaluated to 1.

       while list do list done
	      Execute the do list as long as the while	list  returns  a  zero
	      exit status.

       until list do list done
	      Execute the do list as long as until list returns a nonzero exit
	      status.

       repeat word do list done
	      word is expanded and treated as an arithmetic expression,	 which
	      must evaluate to a number n.  list is then executed n times.

       case word in [ [(] pattern [ | pattern ] ... ) list (;;|;&) ] ... esac
	      Execute  the list associated with the first pattern that matches
	      word, if any.  The form of the patterns is the same as that used
	      for filename generation.	See the section `Filename Generation'.
	      If the list that is executed is terminated with ;&  rather  than
	      ;;,  the	following list is also executed.  This continues until
	      either a list is terminated with ;; or the esac is reached.

       select name [ in word ... term ] do list done
	      where term is one or more newline or ; to terminate  the	words.
	      Print  the  set  of words, each preceded by a number.  If the in
	      word is omitted, use the	positional  parameters.	  The  PROMPT3
	      prompt is printed and a line is read from the line editor if the
	      shell is interactive and that is active, or else standard input.
	      If  this line consists of the number of one of the listed words,
	      then the parameter name is set to the word corresponding to this
	      number.	If  this  line is empty, the selection list is printed
	      again.  Otherwise, the value of the parameter  name  is  set  to
	      null.   The  contents  of	 the  line read from standard input is
	      saved in the parameter REPLY.  list is executed for each	selec‐
	      tion until a break or end-of-file is encountered.

       ( list )
	      Execute  list  in a subshell.  Traps set by the trap builtin are
	      reset to their default values while executing list.

       { list }
	      Execute list.

       function word ... [ () ] [ term ] { list }
       word ... () [ term ] { list }
       word ... () [ term ] command
	      where term is one or more newline or ;.  Define a function which
	      is  referenced  by  any one of word.  Normally, only one word is
	      provided; multiple words are usually  only  useful  for  setting
	      traps.   The  body of the function is the list between the { and
	      }.  See the section `Functions'.

	      If the option  SH_GLOB  is  set  for  compatibility  with	 other
	      shells,  then whitespace may appear between between the left and
	      right parentheses when there is a single word;   otherwise,  the
	      parentheses  will	 be  treated  as forming a globbing pattern in
	      that case.

       time [ pipeline ]
	      The pipeline is executed, and timing statistics are reported  on
	      the  standard error in the form specified by the TIMEFMT parame‐
	      ter.  If pipeline is omitted, print statistics about  the	 shell
	      process and its children.

       [[ exp ]]
	      Evaluates	 the conditional expression exp and return a zero exit
	      status if it is true.  See the section `Conditional Expressions'
	      for a description of exp.

ALTERNATE FORMS FOR COMPLEX COMMANDS
       Many  of zsh's complex commands have alternate forms.  These particular
       versions of complex commands should be considered deprecated and may be
       removed	in the future.	The versions in the previous section should be
       preferred instead.  The short versions below only work if sublist is of
       the form `{ list }' or if the SHORT_LOOPS option is set.	 In this case,
       the test part of the loop must also be suitably delimited, such	as  by
       `[[ ... ]]' or `(( ... ))', else the end of the test will not be recog‐
       nized.

       if list { list } [ elif list { list } ] ... [ else { list } ]
	      An alternate form of if.	The rules mean that

		     if [[ -o ignorebraces ]] {
		       print yes
		     }

	      works, but

		     if true {	# Does not work!
		       print yes
		     }

	      does not, since the test is not suitably delimited.

       if list sublist
	      A short form of the alternate `if'.

       for name ( word ... ) sublist
	      A short form of for.

       for name [ in word ... term ] sublist
	      where term is at least one newline or ;.	Another short form  of
	      for.

       for (( [expr1] ; [expr2] ; [expr3] )) sublist
	      A short form of the arithmetic for command.

       foreach name ( word ... ) list end
	      Another form of for.

       while list { list }
	      An alternative form of while.

       until list { list }
	      An alternative form of until.

       repeat word sublist
	      This is a short form of repeat.

       case word { [ [(] pattern [ | pattern ] ... ) list (;;|;&) ] ... }
	      An alternative form of case.

       select name [ in word term ] sublist
	      where  term  is  at  least  one  newline	or ;.  A short form of
	      select.

RESERVED WORDS
       The following words are recognized as reserved words when used  as  the
       first word of a command unless quoted or disabled using disable -r:

       do  done	 esac then elif else fi for case if while function repeat time
       until select coproc nocorrect foreach end ! [[ { }

       Additionally, `}' is recognized in any position	if  the	 IGNORE_BRACES
       option is not set.

COMMENTS
       In  noninteractive  shells,  or in interactive shells with the INTERAC‐
       TIVE_COMMENTS option set, a word beginning with the third character  of
       the  histchars  parameter (`#' by default) causes that word and all the
       following characters up to a newline to be ignored.

ALIASING
       Every token in the shell input is checked to see if there is  an	 alias
       defined	for  it.  If so, it is replaced by the text of the alias if it
       is in command position (if it could be the first word of a simple  com‐
       mand),  or  if the alias is global.  If the text ends with a space, the
       next word in the shell input is treated as though it  were  in  command
       position	 for  purposes	of alias expansion.  An alias is defined using
       the alias builtin; global aliases may be defined using the -g option to
       that builtin.

       Alias  expansion	 is done on the shell input before any other expansion
       except history expansion.  Therefore, if an alias is  defined  for  the
       word  foo,  alias expansion may be avoided by quoting part of the word,
       e.g. \foo.  But there is nothing to prevent an alias being defined  for
       \foo as well.

QUOTING
       A  character  may be quoted (that is, made to stand for itself) by pre‐
       ceding it with a `\'.  `\' followed by a newline is ignored.

       A string enclosed between `$'' and `'' is processed the same way as the
       string arguments of the print builtin, and the resulting string is con‐
       sidered to be entirely quoted.  A literal `'' character can be included
       in the string by using the `\'' escape.

       All  characters	enclosed  between a pair of single quotes ('') that is
       not preceded by a `$' are quoted.  A single quote cannot appear	within
       single  quotes unless the option RC_QUOTES is set, in which case a pair
       of single quotes are turned into a single quote.	 For example,

	      print ''''

       outputs nothing apart from a newline if RC_QUOTES is not set,  but  one
       single quote if it is set.

       Inside  double  quotes  (""), parameter and command substitution occur,
       and `\' quotes the characters `\', ``', `"', and `$'.

REDIRECTION
       If a command is followed by & and job control is not active,  then  the
       default	standard  input	 for  the command is the empty file /dev/null.
       Otherwise, the environment for the execution of a command contains  the
       file  descriptors  of  the  invoking  shell as modified by input/output
       specifications.

       The following may appear anywhere in a simple command or may precede or
       follow  a  complex  command.   Expansion occurs before word or digit is
       used except as noted below.  If the result of substitution on word pro‐
       duces  more  than  one  filename,  redirection occurs for each separate
       filename in turn.

       < word Open file word for reading as standard input.

       <> word
	      Open file word for reading and writing as	 standard  input.   If
	      the file does not exist then it is created.

       > word Open file word for writing as standard output.  If the file does
	      not exist then it is created.  If the file exists, and the CLOB‐
	      BER  option  is  unset,  this  causes an error; otherwise, it is
	      truncated to zero length.

       >| word
       >! word
	      Same as >, except that the file is truncated to zero  length  if
	      it exists, even if CLOBBER is unset.

       >> word
	      Open  file  word	for writing in append mode as standard output.
	      If the file does not exist, and the  CLOBBER  option  is	unset,
	      this causes an error; otherwise, the file is created.

       >>| word
       >>! word
	      Same  as	>>,  except  that  the	file is created if it does not
	      exist, even if CLOBBER is unset.

       <<[-] word
	      The shell input is read up to a line that is the same  as	 word,
	      or to an end-of-file.  No parameter expansion, command substitu‐
	      tion or filename generation is performed on word.	 The resulting
	      document, called a here-document, becomes the standard input.

	      If  any character of word is quoted with single or double quotes
	      or a `\', no interpretation is placed upon the characters of the
	      document.	 Otherwise, parameter and command substitution occurs,
	      `\' followed by a newline is removed, and `\' must  be  used  to
	      quote  the  characters  `\', `$', ``' and the first character of
	      word.

	      If <<- is used, then all leading tabs are stripped from word and
	      from the document.

       <<< word
	      Perform  shell expansion on word and pass the result to standard
	      input.  This is known as a here-string.

       <& number
       >& number
	      The standard input/output is  duplicated	from  file  descriptor
	      number (see dup2(2)).

       <& -
       >& -   Close the standard input/output.

       <& p
       >& p   The  input/output from/to the coprocess is moved to the standard
	      input/output.

       >& word
       &> word
	      (Except where `>& word' matches one of the above syntaxes;  `&>'
	      can  always  be  used  to avoid this ambiguity.)	Redirects both
	      standard output and standard error (file descriptor  2)  in  the
	      manner  of  `>  word'.   Note  that  this does not have the same
	      effect as `> word 2>&1' in the presence of multios (see the sec‐
	      tion below).

       >&| word
       >&! word
       &>| word
       &>! word
	      Redirects both standard output and standard error (file descrip‐
	      tor 2) in the manner of `>| word'.

       >>& word
       &>> word
	      Redirects both standard output and standard error (file descrip‐
	      tor 2) in the manner of `>> word'.

       >>&| word
       >>&! word
       &>>| word
       &>>! word
	      Redirects both standard output and standard error (file descrip‐
	      tor 2) in the manner of `>>| word'.

       If one of the above is preceded by a digit, then	 the  file  descriptor
       referred	 to is that specified by the digit instead of the default 0 or
       1.  The order in which redirections are specified is significant.   The
       shell  evaluates	 each  redirection  in	terms of the (file descriptor,
       file) association at the time of evaluation.  For example:

	      ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (that
       is, fname).  If the order of redirections were reversed, file  descrip‐
       tor 2 would be associated with the terminal (assuming file descriptor 1
       had been) and then file descriptor 1  would  be	associated  with  file
       fname.

MULTIOS
       If the user tries to open a file descriptor for writing more than once,
       the shell opens the file descriptor as a pipe to a process that	copies
       its  input  to  all the specified outputs, similar to tee, provided the
       MULTIOS option is set, as it is by default.  Thus:

	      date >foo >bar

       writes the date to two files, named `foo' and `bar'.  Note that a  pipe
       is an implicit redirection; thus

	      date >foo | cat

       writes the date to the file `foo', and also pipes it to cat.

       If  the MULTIOS option is set, the word after a redirection operator is
       also subjected to filename generation (globbing).  Thus

	      : > *

       will truncate all files in the current directory, assuming  there's  at
       least  one.  (Without the MULTIOS option, it would create an empty file
       called `*'.)  Similarly, you can do

	      echo exit 0 >> *.sh

       If the user tries to open a file descriptor for reading more than once,
       the  shell opens the file descriptor as a pipe to a process that copies
       all the specified inputs to its output in the order specified,  similar
       to cat, provided the MULTIOS option is set.  Thus

	      sort <foo <fubar

       or even

	      sort <f{oo,ubar}

       is equivalent to `cat foo fubar | sort'.

       Note that a pipe is an implicit redirection; thus

	      cat bar | sort <foo

       is equivalent to `cat bar foo | sort' (note the order of the inputs).

       If  the MULTIOS option is unset, each redirection replaces the previous
       redirection for that file descriptor.  However, all files redirected to
       are actually opened, so

	      echo foo > bar > baz

       when MULTIOS is unset will truncate bar, and write `foo' into baz.

REDIRECTIONS WITH NO COMMAND
       When a simple command consists of one or more redirection operators and
       zero or more parameter assignments, but no command name, zsh can behave
       in several ways.

       If  the	parameter NULLCMD is not set or the option CSH_NULLCMD is set,
       an error is caused.  This is the csh behavior and CSH_NULLCMD is set by
       default when emulating csh.

       If  the option SH_NULLCMD is set, the builtin `:' is inserted as a com‐
       mand with the given redirections.  This is the default  when  emulating
       sh or ksh.

       Otherwise, if the parameter NULLCMD is set, its value will be used as a
       command with the given redirections.  If both NULLCMD  and  READNULLCMD
       are  set,  then the value of the latter will be used instead of that of
       the former when the redirection is an input.  The default  for  NULLCMD
       is `cat' and for READNULLCMD is `more'. Thus

	      < file

       shows the contents of file on standard output, with paging if that is a
       terminal.  NULLCMD and READNULLCMD may refer to shell functions.

COMMAND EXECUTION
       If a command name contains no slashes, the shell attempts to locate it.
       If  there exists a shell function by that name, the function is invoked
       as described in the section  `Functions'.   If  there  exists  a	 shell
       builtin by that name, the builtin is invoked.

       Otherwise,  the	shell  searches	 each element of $path for a directory
       containing an executable file by that name.  If the  search  is	unsuc‐
       cessful,	 the  shell prints an error message and returns a nonzero exit
       status.

       If execution fails because the file is not in  executable  format,  and
       the  file  is  not  a  directory,  it  is assumed to be a shell script.
       /bin/sh is spawned to execute it.  If the program is a  file  beginning
       with `#!', the remainder of the first line specifies an interpreter for
       the program.  The shell will execute the specified interpreter on oper‐
       ating systems that do not handle this executable format in the kernel.

FUNCTIONS
       Shell functions are defined with the function reserved word or the spe‐
       cial syntax `funcname ()'.  Shell functions  are	 read  in  and	stored
       internally.  Alias names are resolved when the function is read.	 Func‐
       tions are executed like commands with the  arguments  passed  as	 posi‐
       tional parameters.  (See the section `Command Execution'.)

       Functions execute in the same process as the caller and share all files
       and present working directory with the caller.	A  trap	 on  EXIT  set
       inside a function is executed after the function completes in the envi‐
       ronment of the caller.

       The return builtin is used to return from function calls.

       Function identifiers can be listed with the functions  builtin.	 Func‐
       tions can be undefined with the unfunction builtin.

AUTOLOADING FUNCTIONS
       A  function  can	 be marked as undefined using the autoload builtin (or
       `functions -u' or `typeset -fu').  Such a function has no  body.	  When
       the  function  is first executed, the shell searches for its definition
       using the elements of the fpath variable.  Thus to define functions for
       autoloading, a typical sequence is:

	      fpath=(~/myfuncs $fpath)
	      autoload myfunc1 myfunc2 ...

       The  usual  alias  expansion  during  reading will be suppressed if the
       autoload builtin or its equivalent is given the option -U. This is rec‐
       ommended	 for  the use of functions supplied with the zsh distribution.
       Note that for functions precompiled with the zcompile  builtin  command
       the flag -U must be provided when the .zwc file is created, as the cor‐
       responding information is compiled into the latter.

       For each element in fpath, the shell looks for  three  possible	files,
       the newest of which is used to load the definition for the function:

       element.zwc
	      A	 file  created	with  the  zcompile  builtin command, which is
	      expected to contain the definitions for  all  functions  in  the
	      directory named element.	The file is treated in the same manner
	      as a directory containing files for functions  and  is  searched
	      for  the	definition of the function.   If the definition is not
	      found, the search for a definition proceeds with the  other  two
	      possibilities described below.

	      If element already includes a .zwc extension (i.e. the extension
	      was explicitly given by the user), element is searched  for  the
	      definition  of the function without comparing its age to that of
	      other files; in fact, there does not need to  be	any  directory
	      named  element  without  the  suffix.  Thus including an element
	      such as `/usr/local/funcs.zwc' in fpath will speed up the search
	      for  functions,  with  the  disadvantage that functions included
	      must be explicitly recompiled by hand before the	shell  notices
	      any changes.

       element/function.zwc
	      A	 file  created with zcompile, which is expected to contain the
	      definition for function.	It may include other function  defini‐
	      tions as well, but those are neither loaded nor executed; a file
	      found in this way is searched only for the definition  of	 func‐
	      tion.

       element/function
	      A file of zsh command text, taken to be the definition for func‐
	      tion.

       In summary, the order of searching is, first, in the parents of	direc‐
       tories  in  fpath  for  the  newer  of either a compiled directory or a
       directory in fpath; second, if more than one of these contains a	 defi‐
       nition  for  the	 function that is sought, the leftmost in the fpath is
       chosen; and third, within a directory, the newer of either  a  compiled
       function or an ordinary function definition is used.

       If  the	KSH_AUTOLOAD option is set, or the file contains only a simple
       definition of the function, the file's contents will be executed.  This
       will  normally  define  the  function in question, but may also perform
       initialization, which is executed in the context of the function execu‐
       tion, and may therefore define local parameters.	 It is an error if the
       function is not defined by loading the file.

       Otherwise, the function body (with no surrounding  `funcname()  {...}')
       is taken to be the complete contents of the file.  This form allows the
       file to be used directly as an executable shell script.	If  processing
       of  the	file  results  in  the function being re-defined, the function
       itself is not re-executed.  To force the shell to  perform  initializa‐
       tion  and  then call the function defined, the file should contain ini‐
       tialization code (which will be executed then discarded) in addition to
       a  complete  function definition (which will be retained for subsequent
       calls to the function), and a call to the shell function, including any
       arguments, at the end.

       For example, suppose the autoload file func contains

	      func() { print This is func; }
	      print func is initialized

       then  `func;  func' with KSH_AUTOLOAD set will produce both messages on
       the first call, but only the message `This is func' on the  second  and
       subsequent  calls.   Without KSH_AUTOLOAD set, it will produce the ini‐
       tialization message on the first call, and the  other  message  on  the
       second and subsequent calls.

       It  is  also  possible  to  create  a  function	that  is not marked as
       autoloaded, but which loads its own definition by searching  fpath,  by
       using  `autoload -X' within a shell function.  For example, the follow‐
       ing are equivalent:

	      myfunc() {
		autoload -X
	      }
	      myfunc args...

       and

	      unfunction myfunc	  # if myfunc was defined
	      autoload myfunc
	      myfunc args...

       In fact, the functions command outputs `builtin	autoload  -X'  as  the
       body  of	 an  autoloaded	 function.   A true autoloaded function can be
       identified by the presence of the comment `# undefined'	in  the	 body,
       because	all  comments  are  discarded from defined functions.  This is
       done so that

	      eval "$(functions)"

       produces a reasonable result.

       To load the definition of an autoloaded function myfunc without execut‐
       ing myfunc, use:

	      autoload +X myfunc

SPECIAL FUNCTIONS
       The following functions, if defined, have special meaning to the shell:

       chpwd  Executed whenever the current working directory is changed.

       periodic
	      If  the parameter PERIOD is set, this function is executed every
	      $PERIOD seconds, just before a prompt.

       precmd Executed before each prompt.

       preexec
	      Executed just after a command has been read and is about	to  be
	      executed.	  If the history mechanism is active (and the line was
	      not discarded from the history buffer), the string that the user
	      typed  is passed as the first argument, otherwise it is an empty
	      string.  The actual command that	will  be  executed  (including
	      expanded	aliases)  is passed in two different forms: the second
	      argument is a single-line, size-limited version of  the  command
	      (with  things  like  function bodies elided); the third argument
	      contains the full text what what is being executed.

       TRAPNAL
	      If defined and non-null, this function will be executed whenever
	      the shell catches a signal SIGNAL, where NAL is a signal name as
	      specified for the kill  builtin.	 The  signal  number  will  be
	      passed as the first parameter to the function.

	      If  a  function  of this form is defined and null, the shell and
	      processes spawned by it will ignore SIGNAL.

       TRAPDEBUG
	      Executed after each command.

       TRAPEXIT
	      Executed when the shell exits,  or  when	the  current  function
	      exits if defined inside a function.

       TRAPZERR
	      Executed	whenever  a  command has a non-zero exit status.  How‐
	      ever, the function is not executed if the command occurred in  a
	      sublist  followed	 by  `&&' or `||'; only the final command in a
	      sublist of this type causes the trap to be executed.

       The functions beginning `TRAP' may alternatively be  defined  with  the
       trap  builtin:	this may be preferable for some uses, as they are then
       run in the environment of the calling process, rather than in their own
       function	 environment.	Apart from the difference in calling procedure
       and the fact that the function form appears in lists of functions,  the
       forms

	      TRAPNAL() {
	       # code
	      }

       and

	      trap '
	       # code

       are equivalent.

JOBS
       If  the	MONITOR	 option	 is set, an interactive shell associates a job
       with each pipeline.  It keeps a table of current jobs, printed  by  the
       jobs  command,  and  assigns them small integer numbers.	 When a job is
       started asynchronously with `&', the shell prints a  line  which	 looks
       like:

	      [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process ID was 1234.

       If a job is started with `&|' or `&!', then  that  job  is  immediately
       disowned.   After  startup,  it does not have a place in the job table,
       and is not subject to the job control features described here.

       If you are running a job and wish to do something else you may hit  the
       key  ^Z (control-Z) which sends a TSTP signal to the current job:  this
       key may be redefined by the susp option of the external	stty  command.
       The  shell  will	 then  normally	 indicate  that the job has been `sus‐
       pended', and print another prompt.  You can then manipulate  the	 state
       of  this	 job, putting it in the background with the bg command, or run
       some other commands and then eventually bring the  job  back  into  the
       foreground  with	 the foreground command fg.  A ^Z takes effect immedi‐
       ately and is like an interrupt in that pending output and unread	 input
       are discarded when it is typed.

       A job being run in the background will suspend if it tries to read from
       the terminal.  Background jobs are normally allowed to produce  output,
       but  this  can be disabled by giving the command `stty tostop'.	If you
       set this tty option, then background jobs will suspend when they try to
       produce output like they do when they try to read input.

       When  a	command	 is  suspended and continued later with the fg or wait
       builtins, zsh restores tty modes that were in effect when it  was  sus‐
       pended.	 This (intentionally) does not apply if the command is contin‐
       ued via `kill -CONT', nor when it is continued with bg.

       There are several ways to refer to jobs in the shell.   A  job  can  be
       referred	 to  by	 the process ID of any process of the job or by one of
       the following:

       %number
	      The job with the given number.
       %string
	      Any job whose command line begins with string.
       %?string
	      Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to `%%'.
       %-     Previous job.

       The shell learns immediately whenever a process changes state.  It nor‐
       mally  informs  you  whenever  a job becomes blocked so that no further
       progress is possible.  If the NOTIFY option is not set, it waits	 until
       just before it prints a prompt before it informs you.

       When  the  monitor mode is on, each background job that completes trig‐
       gers any trap set for CHLD.

       When you try to leave the shell while jobs are  running	or  suspended,
       you  will  be warned that `You have suspended (running) jobs'.  You may
       use the jobs command to see what they are.  If you do this  or  immedi‐
       ately try to exit again, the shell will not warn you a second time; the
       suspended jobs will be terminated, and the running jobs will be sent  a
       SIGHUP signal, if the HUP option is set.

       To  avoid  having  the shell terminate the running jobs, either use the
       nohup command (see nohup(1)) or the disown builtin.

SIGNALS
       The INT and QUIT signals for an invoked command are ignored if the com‐
       mand  is	 followed by `&' and the MONITOR option is not active.	Other‐
       wise, signals have the values inherited by the shell  from  its	parent
       (but see the TRAPNAL special functions in the section `Functions').

ARITHMETIC EVALUATION
       The  shell  can	perform	 integer and floating point arithmetic, either
       using the builtin let, or via a substitution of the form $((...)).  For
       integers,  the  shell is usually compiled to use 8-byte precision where
       this is available, otherwise precision is 4 bytes.  This can be tested,
       for example, by giving the command `print - $(( 12345678901 ))'; if the
       number appears unchanged, the precision is at least 8 bytes.   Floating
       point arithmetic is always double precision.

       The let builtin command takes arithmetic expressions as arguments; each
       is evaluated separately.	 Since many of the  arithmetic	operators,  as
       well  as	 spaces, require quoting, an alternative form is provided: for
       any command which begins with a `((', all the characters until a match‐
       ing  `))'  are  treated as a quoted expression and arithmetic expansion
       performed as for an argument of	let.   More  precisely,	 `((...))'  is
       equivalent to `let "..."'.  For example, the following statement

	      (( val = 2 + 1 ))

       is equivalent to

	      let "val = 2 + 1"

       both  assigning	the  value 3 to the shell variable foo and returning a
       zero status.

       Integers can be in bases other than 10.	A leading `0x' or `0X' denotes
       hexadecimal.   Integers may also be of the form `base#n', where base is
       a decimal number between two and thirty-six representing the arithmetic
       base  and  n  is	 a number in that base (for example, `16#ff' is 255 in
       hexadecimal).  The base# may also be omitted, in which case base 10  is
       used.  For backwards compatibility the form `[base]n' is also accepted.

       It is also possible to specify a base to be used for output in the form
       `[#base]', for example `[#16]'.	This is used  when  outputting	arith‐
       metical	substitutions  or  when assigning to scalar parameters, but an
       explicitly defined integer or floating  point  parameter	 will  not  be
       affected.   If  an  integer variable is implicitly defined by an arith‐
       metic expression, any base specified in this way will  be  set  as  the
       variable's  output  arithmetic  base  as if the option `-i base' to the
       typeset builtin had been used.  The expression has no precedence and if
       it occurs more than once in a mathematical expression, the last encoun‐
       tered is used.  For clarity it is recommended that  it  appear  at  the
       beginning of an expression.  As an example:

	      typeset -i 16 y
	      print $(( [#8] x = 32, y = 32 ))
	      print $x $y

       outputs first `8#40', the rightmost value in the given output base, and
       then `8#40 16#20', because y has been explicitly declared to have  out‐
       put base 16, while x (assuming it does not already exist) is implicitly
       typed by the arithmetic evaluation, where it acquires the  output  base
       8.

       When  an output base is specified using the `[#base]' syntax, an appro‐
       priate base prefix will be output if necessary, so that the value  out‐
       put  is	valid  syntax  for  input.   If	 the # is doubled, for example
       `[##16]', then no base prefix is output.

       Floating point constants are recognized by the presence	of  a  decimal
       point  or an exponent.  The decimal point may be the first character of
       the constant, but the exponent character e or E may not, as it will  be
       taken for a parameter name.

       An  arithmetic  expression uses nearly the same syntax, precedence, and
       associativity of expressions in C.  The following  operators  are  sup‐
       ported (listed in decreasing order of precedence):

       + - ! ~ ++ --
	      unary plus/minus, logical NOT, complement, {pre,post}{in,de}cre‐
	      ment
       << >>  bitwise shift left, right
       &      bitwise AND
       ^      bitwise XOR
       |      bitwise OR
       **     exponentiation
       * / %  multiplication, division, modulus (remainder)
       + -    addition, subtraction
       < > <= >=
	      comparison
       == !=  equality and inequality
       &&     logical AND
       || ^^  logical OR, XOR
       ? :    ternary operator
       = += -= *= /= %= &= ^= |= <<= >>= &&= ||= ^^= **=
	      assignment
       ,      comma operator

       The operators `&&', `||', `&&=', and `||='  are	short-circuiting,  and
       only  one of the latter two expressions in a ternary operator is evalu‐
       ated.  Note the precedence of the bitwise AND, OR, and XOR operators.

       Mathematical functions can be  called  with  the	 syntax	 `func(args)',
       where  the  function  decides  if  the  args  is	 used as a string or a
       comma-separated list of arithmetic  expressions.	 The  shell  currently
       defines	no mathematical functions by default, but the module zsh/math‐
       func may be loaded with the zmodload builtin to provide standard float‐
       ing point mathematical functions.

       An  expression of the form `##x' where x is any character sequence such
       as `a', `^A', or `\M-\C-x' gives the ASCII value of this character  and
       an  expression  of  the	form `#foo' gives the ASCII value of the first
       character of the value of the parameter foo.  Note that this is differ‐
       ent  from  the  expression  `$#foo',  a standard parameter substitution
       which gives the length of the parameter foo.  `#\' is accepted  instead
       of `##', but its use is deprecated.

       Named  parameters  and  subscripted  arrays  can	 be referenced by name
       within an arithmetic expression without using the  parameter  expansion
       syntax.	For example,

	      ((val2 = val1 * 2))

       assigns twice the value of $val1 to the parameter named val2.

       An  internal  integer representation of a named parameter can be speci‐
       fied with the integer builtin.  Arithmetic evaluation is	 performed  on
       the  value  of each assignment to a named parameter declared integer in
       this manner.  Assigning a floating point number to an  integer  results
       in rounding down to the next integer.

       Likewise,  floating  point  numbers  can	 be  declared  with  the float
       builtin; there are two types, differing only in their output format, as
       described  for  the typeset builtin.  The output format can be bypassed
       by using arithmetic substitution instead of the parameter substitution,
       i.e.  `${float}'	 uses  the  defined  format,  but  `$((float))' uses a
       generic floating point format.

       Promotion of integer to floating point values is performed where neces‐
       sary.   In  addition,  if  any operator which requires an integer (`~',
       `&', `|', `^', `%', `<<', `>>' and their equivalents  with  assignment)
       is given a floating point argument, it will be silently rounded down to
       the next integer.

       Scalar variables can hold integer or floating point values at different
       times; there is no memory of the numeric type in this case.

       If a variable is first assigned in a numeric context without previously
       being declared, it will be implicitly typed as  integer	or  float  and
       retain  that  type either until the type is explicitly changed or until
       the end of the scope.  This  can	 have  unforeseen  consequences.   For
       example, in the loop

	      for (( f = 0; f < 1; f += 0.1 )); do
	      # use $f
	      done

       if  f has not already been declared, the first assignment will cause it
       to be created as an integer, and consequently the operation `f +=  0.1'
       will  always cause the result to be truncated to zero, so that the loop
       will fail.  A simple fix would be to turn the initialization into `f  =
       0.0'.   It is therefore best to declare numeric variables with explicit
       types.

CONDITIONAL EXPRESSIONS
       A conditional expression is used with the [[ compound command  to  test
       attributes  of  files  and  to compare strings.	Each expression can be
       constructed from one or more of the following unary or  binary  expres‐
       sions:

       -a file
	      true if file exists.

       -b file
	      true if file exists and is a block special file.

       -c file
	      true if file exists and is a character special file.

       -d file
	      true if file exists and is a directory.

       -e file
	      true if file exists.

       -f file
	      true if file exists and is a regular file.

       -g file
	      true if file exists and has its setgid bit set.

       -h file
	      true if file exists and is a symbolic link.

       -k file
	      true if file exists and has its sticky bit set.

       -n string
	      true if length of string is non-zero.

       -o option
	      true if option named option is on.  option may be a single char‐
	      acter, in which case it is a single letter  option  name.	  (See
	      the section `Specifying Options'.)

       -p file
	      true if file exists and is a FIFO special file (named pipe).

       -r file
	      true if file exists and is readable by current process.

       -s file
	      true if file exists and has size greater than zero.

       -t fd  true  if file descriptor number fd is open and associated with a
	      terminal device.	(note: fd is not optional)

       -u file
	      true if file exists and has its setuid bit set.

       -w file
	      true if file exists and is writable by current process.

       -x file
	      true if file exists and is executable by	current	 process.   If
	      file  exists  and	 is  a directory, then the current process has
	      permission to search in the directory.

       -z string
	      true if length of string is zero.

       -L file
	      true if file exists and is a symbolic link.

       -O file
	      true if file exists and is owned by the  effective  user	ID  of
	      this process.

       -G file
	      true if file exists and its group matches the effective group ID
	      of this process.

       -S file
	      true if file exists and is a socket.

       -N file
	      true if file exists and its access time is not  newer  than  its
	      modification time.

       file1 -nt file2
	      true if file1 exists and is newer than file2.

       file1 -ot file2
	      true if file1 exists and is older than file2.

       file1 -ef file2
	      true if file1 and file2 exist and refer to the same file.

       string = pattern
       string == pattern
	      true  if string matches pattern.	The `==' form is the preferred
	      one.  The `=' form is for backward compatibility and  should  be
	      considered obsolete.

       string != pattern
	      true if string does not match pattern.

       string1 < string2
	      true  if	string1	 comes	before string2 based on ASCII value of
	      their characters.

       string1 > string2
	      true if string1 comes after string2  based  on  ASCII  value  of
	      their characters.

       exp1 -eq exp2
	      true if exp1 is numerically equal to exp2.

       exp1 -ne exp2
	      true if exp1 is numerically not equal to exp2.

       exp1 -lt exp2
	      true if exp1 is numerically less than exp2.

       exp1 -gt exp2
	      true if exp1 is numerically greater than exp2.

       exp1 -le exp2
	      true if exp1 is numerically less than or equal to exp2.

       exp1 -ge exp2
	      true if exp1 is numerically greater than or equal to exp2.

       ( exp )
	      true if exp is true.

       ! exp  true if exp is false.

       exp1 && exp2
	      true if exp1 and exp2 are both true.

       exp1 || exp2
	      true if either exp1 or exp2 is true.

       Normal  shell  expansion	 is  performed on the file, string and pattern
       arguments, but the result of each expansion is constrained to be a sin‐
       gle  word,  similar  to	the effect of double quotes.  However, pattern
       metacharacters are active for the pattern arguments; the	 patterns  are
       the  same  as  those  used for filename generation, see zshexpn(1), but
       there is no special behaviour of `/' nor	 initial  dots,	 and  no  glob
       qualifiers are allowed.

       In  each	 of the above expressions, if file is of the form `/dev/fd/n',
       where n is an integer, then the test applied to	the  open  file	 whose
       descriptor  number is n, even if the underlying system does not support
       the /dev/fd directory.

       In the forms which do numeric comparison, the expressions  exp  undergo
       arithmetic expansion as if they were enclosed in $((...)).

       For example, the following:

	      [[ ( -f foo || -f bar ) && $report = y* ]] && print File exists.

       tests if either file foo or file bar exists, and if so, if the value of
       the parameter report begins with `y';  if  the  complete	 condition  is
       true, the message `File exists.' is printed.

PROMPT EXPANSION
       Prompt  sequences  undergo  a  special form of expansion.  This type of
       expansion is also available using the -P option to the print builtin.

       If the PROMPT_SUBST option is set, the prompt string is first subjected
       to  parameter expansion, command substitution and arithmetic expansion.
       See zshexpn(1).

       Certain escape sequences may be recognised in the prompt string.

       If the PROMPT_BANG option is set, a `!' in the prompt  is  replaced  by
       the  current  history  event  number.  A literal `!' may then be repre‐
       sented as `!!'.

       If the PROMPT_PERCENT option is	set,  certain  escape  sequences  that
       start  with  `%'	 are  expanded.	 Some escapes take an optional integer
       argument, which should appear between the `%' and the next character of
       the sequence.  The following escape sequences are recognized:

       %%     A `%'.

       %)     A `)'.

       %d
       %/     Present  working	directory  ($PWD).   If an integer follows the
	      `%', it specifies a number of trailing  components  of  $PWD  to
	      show;  zero  means the whole path.  A negative integer specifies
	      leading components, i.e. %-1d specifies the first component.

       %~     As %d and %/, but if $PWD has a named directory as  its  prefix,
	      that  part  is  replaced	by  a  `~' followed by the name of the
	      directory.  If it starts with $HOME, that part is replaced by  a
	      `~'.

       %h
       %!     Current history event number.

       %L     The current value of $SHLVL.

       %M     The full machine hostname.

       %m     The hostname up to the first `.'.	 An integer may follow the `%'
	      to specify how many components  of  the  hostname	 are  desired.
	      With a negative integer, trailing components of the hostname are
	      shown.

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

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

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

       %t
       %@     Current time of day, in 12-hour, am/pm format.

       %T     Current time of day, in 24-hour format.

       %*     Current time of day in 24-hour format, with seconds.

       %n     $USERNAME.

       %N     The name of the script, sourced file, or shell function that zsh
	      is currently executing, whichever was started most recently.  If
	      there is none, this is equivalent to the parameter $0.  An inte‐
	      ger may follow the `%' to specify a number of trailing path com‐
	      ponents to show; zero means the full path.  A  negative  integer
	      specifies leading components.

       %i     The  line number currently being executed in the script, sourced
	      file, or shell function given by %N.  This is  most  useful  for
	      debugging as part of $PS4.

       %w     The date in day-dd format.

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

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

       %D{string}
	      string  is  formatted  using  the	 strftime function.  See strf‐
	      time(3) for more details.	 Three additional codes are available:
	      %f  prints the day of the month, like %e but without any preced‐
	      ing space if the day is a single digit, and %K/%L correspond  to
	      %k/%l  for  the  hour  of the day (24/12 hour clock) in the same
	      way.

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

       %?     The return code of the last command  executed  just  before  the
	      prompt.

       %_     The  status  of the parser, i.e. the shell constructs (like `if'
	      and `for') that have been started on the command line. If	 given
	      an  integer  number  that	 many strings will be printed; zero or
	      negative or no integer means print as many as there  are.	  This
	      is most useful in prompts PS2 for continuation lines and PS4 for
	      debugging with the XTRACE option; in the	latter	case  it  will
	      also work non-interactively.

       %E     Clears to end of line.

       %#     A	 `#'  if  the  shell is running with privileges, a `%' if not.
	      Equivalent to `%(!.#.%%)'.  The definition of `privileged',  for
	      these  purposes,	is  that either the effective user ID is zero,
	      or, if POSIX.1e capabilities are supported, that	at  least  one
	      capability  is  raised  in  either  the Effective or Inheritable
	      capability vectors.

       %v     The value of the first element of	 the  psvar  array  parameter.
	      Following	 the  `%'  with	 an  integer gives that element of the
	      array.  Negative integers count from the end of the array.

       %{...%}
	      Include a string as  a  literal  escape  sequence.   The	string
	      within  the braces should not change the cursor position.	 Brace
	      pairs can nest.

       %(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.	  This
	      separator	 may  not appear in the true-text, except as part of a
	      %-escape sequence.  A `)' may appear in the false-text as	 `%)'.
	      true-text	 and  false-text  may  both contain arbitrarily-nested
	      escape sequences, including further ternary expressions.

	      The left parenthesis may be preceded or followed by  a  positive
	      integer  n,  which defaults to zero.  A negative integer will be
	      multiplied by -1.	 The test character x may be any of  the  fol‐
	      lowing:

	      c
	      .
	      ~	     True if the current path, with prefix replacement, has at
		     least n elements.
	      /
	      C	     True if the current absolute path has  at	least  n  ele‐
		     ments.
	      t	     True if the time in minutes is equal to n.
	      T	     True if the time in hours is equal to n.
	      d	     True if the day of the month is equal to n.
	      D	     True if the month is equal to n (January = 0).
	      w	     True if the day of the week is equal to n (Sunday = 0).
	      ?	     True if the exit status of the last command was n.
	      #	     True if the effective uid of the current process is n.
	      g	     True if the effective gid of the current process is n.
	      l	     True  if  at least n characters have already been printed
		     on the current line.
	      L	     True if the SHLVL parameter is at least n.
	      S	     True if the SECONDS parameter is at least n.
	      v	     True if the array psvar has at least n elements.
	      _	     True if at least n shell constructs were started.
	      !	     True if the shell is running with privileges.

       %<string<
       %>string>
       %[xstring]
	      Specifies truncation behaviour for the remainder of  the	prompt
	      string.	 The   third,	deprecated,   form  is	equivalent  to
	      `%xstringx', i.e. x may be `<' or `>'.   The  numeric  argument,
	      which  in	 the  third form may appear immediately after the `[',
	      specifies the maximum permitted length of	 the  various  strings
	      that  can	 be  displayed in the prompt.  The string will be dis‐
	      played in place of the truncated portion	of  any	 string;  note
	      this does not undergo prompt expansion.

	      The  forms  with `<' truncate at the left of the string, and the
	      forms with `>' truncate at the right of the string.   For	 exam‐
	      ple,  if	the  current  directory	 is  `/home/pike',  the prompt
	      `%8<..<%/' will expand to `..e/pike'.  In this string, the  ter‐
	      minating	character (`<', `>' or `]'), or in fact any character,
	      may be quoted by a preceding `\'; note when using print -P, how‐
	      ever, that this must be doubled as the string is also subject to
	      standard	print  processing,  in	addition  to  any  backslashes
	      removed  by a double quoted string:  the worst case is therefore
	      `print -P "%<\\\\<<..."'.

	      If the string is longer than the specified truncation length, it
	      will appear in full, completely replacing the truncated string.

	      The part of the prompt string to be truncated runs to the end of
	      the string, or to the end of the next  enclosing	group  of  the
	      `%('  construct,	or  to	the next truncation encountered at the
	      same grouping level (i.e. truncations inside a  `%('  are	 sepa‐
	      rate), which ever comes first.  In particular, a truncation with
	      argument zero (e.g. `%<<') marks the end of  the	range  of  the
	      string  to  be truncated while turning off truncation from there
	      on. For example, the prompt  '%10<...<%~%<<%#  '	will  print  a
	      truncated representation of the current directory, followed by a
	      `%' or `#', followed by a space.	Without the `%<<',  those  two
	      characters would be included in the string to be truncated.

       %c
       %.
       %C     Trailing	component  of  $PWD.  An integer may follow the `%' to
	      get more than one component.  Unless `%C' is  used,  tilde  con‐
	      traction	is performed first.  These are deprecated as %c and %C
	      are equivalent to %1~ and %1/, respectively, while explicit pos‐
	      itive  integers  have  the  same	effect	as  for the latter two
	      sequences.

zsh 4.0.1			 June 1, 2001			    ZSHMISC(1)
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