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RedHat 9 (Linux i386) - man page for zshmisc (redhat section 1)

ZSHMISC(1)			     General Commands Manual			       ZSHMISC(1)

       zshmisc - everything and then some

       A  simple  command is a sequence of optional parameter assignments followed by blank-sepa-
       rated words, with optional redirections interspersed.  The first word is the command to be
       executed,  and  the  remaining  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 pipeline 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 ordinary back-
       ground 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 command 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	sublist  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 whatsoever, including
       the complex commands below; this is implied wherever the  word  `list'  appears	in  later
       descriptions.  For example, the commands in a shell function form a special sort of list.

       A  simple  command may be preceded by a precommand modifier, which will alter how the com-
       mand 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.

	      Spelling	correction  is not done on any of the words.  This must appear before any
	      other precommand modifier, as it is interpreted 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.

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

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

       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, executing list each time.  If the  in  word
	      is omitted, use the positional parameters instead of the words.

       for (( [expr1] ; [expr2] ; [expr3] )) do list done
	      The  arithmetic  expression  expr1  is evaluated first (see the section `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 selection 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 parameter.  If pipeline is omitted, print sta-
	      tistics 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.

       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.  For the if, while and until commands, in both these cases the
       test part of the loop must also be suitably delimited, such as by `[[ ... ]]' or  `((  ...
       ))',  else  the	end  of  the  test will not be recognized.  For the for, repeat, case and
       select commands no such special form for the arguments is necessary, but the other  condi-
       tion (the special form of sublist or use of the SHORT_LOOPS option) still applies.

       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'.  The same limitations on the form of list apply
	      as for the previous form.

       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.  Note the limitations on the form of  list	mentioned

       until list { list }
	      An  alternative  form of until.  Note the limitations on the form of list mentioned

       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.

       The following words are recognized as reserved words when used as the first word of a com-
       mand 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.

       In noninteractive shells, or in interactive shells with	the  INTERACTIVE_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.

       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 command), 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.

       A character may be quoted (that is, made to stand for itself) by preceding 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 considered 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 exam-

	      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 `$'.

       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 produces 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 CLOBBER 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 substitution 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 inter-
	      pretation  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 section below).

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

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

       >>&| word
       >>&! word
       &>>| word
       &>>! word
	      Redirects both standard output and standard error (file descriptor 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  redi-
       rections  were reversed, file descriptor 2 would be associated with the terminal (assuming
       file descriptor 1 had been) and then file descriptor  1	would  be  associated  with  file

       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 out-
       puts, 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 re-
       direction; 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.

       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 command 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.

       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 `Func-
       tions'.	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  exe-
       cutable	file by that name.  If the search is unsuccessful, the shell prints an error mes-
       sage 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 inter-
       preter  for  the  program.   The shell will execute the specified interpreter on operating
       systems that do not handle this executable format in the kernel.

       Shell functions are defined with the function reserved word or the special  syntax  `func-
       name  ()'.   Shell  functions are read in and stored internally.  Alias names are resolved
       when the function is read.  Functions are executed like commands with the arguments passed
       as positional parameters.  (See the section `Command Execution'.)

       Functions  execute in the same process as the caller and share all files and present work-
       ing directory with the caller.  A trap on EXIT set inside a function is executed after the
       function completes in the environment of the caller.

       The return builtin is used to return from function calls.

       Function identifiers can be listed with the functions builtin.  Functions can be undefined
       with the unfunction builtin.

       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 recommended 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  corresponding
       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:

	      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.

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

	      A file of zsh command text, taken to be the definition for function.

       In  summary,  the order of searching is, first, in the parents of directories in fpath for
       the newer of either a compiled directory or a directory in fpath; second, if more than one
       of  these contains a definition 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 execution, 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  exe-
       cutable 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 initialization  and
       then call the function defined, the file should contain initialization 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, includ-
       ing 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 initialization 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 following are equivalent:

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


	      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 executing myfunc, use:

	      autoload +X myfunc

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

       chpwd  Executed whenever the current working directory is changed.

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

       precmd Executed before each prompt.

	      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  buf-
	      fer),  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.

	      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.

	      Executed after each command.

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

	      Executed	whenever  a command has a non-zero exit status.  However, 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

	      TRAPNAL() {
	       # code


	      trap '
	       # code

       are equivalent.

       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 `suspended', 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 immediately 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 suspended.  This (intentionally) does not  apply
       if the command is continued 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:

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

       The shell learns immediately whenever a process changes state.  It  normally  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 triggers any trap set  for

       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 immediately try to exit again, the shell will not warn you a sec-
       ond 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.

       The INT and QUIT signals for an invoked command are ignored if the command is followed  by
       `&' and the MONITOR option is not active.  Otherwise, signals have the values inherited by
       the shell from its parent (but see the TRAPNAL special functions  in  the  section  `Func-

       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 sepa-
       rately.	 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  matching  `))'  are treated as a quoted expression and arithmetic expansion per-
       formed 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 val 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 arithmetical substitutions or when  assign-
       ing  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  arithmetic
       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
       encountered 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 output 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	appropriate  base  prefix
       will be output if necessary, so that the value output 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 supported (listed in decreasing order of

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

       The operators `&&', `||', `&&=', and `||=' are short-circuiting, and only one of the  lat-
       ter  two  expressions in a ternary operator is evaluated.  Note the precedence of the bit-
       wise 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 expres-
       sions. The shell currently defines no mathematical functions by default,  but  the  module
       zsh/mathfunc  may  be  loaded with the zmodload builtin to provide standard floating 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  different  from  the expression `$#foo', a standard parameter substitution which
       gives the length of the parameter foo.  `#\' is accepted instead of `##', but its  use  is

       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 specified 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  inte-
       ger 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 necessary.  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

       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 initial-
       ization	into  `f = 0.0'.  It is therefore best to declare numeric variables with explicit

       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 fol-
       lowing unary or binary expressions:

       -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 character, 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 single word, similar to the effect of dou-
       ble 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  inte-
       ger,  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

       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 represented 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  recog-

       %%     A `%'.

       %)     A `)'.

       %/     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  nega-
	      tive 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 `~'.

       %!     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.

       %@     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 exe-
	      cuting, whichever was started most recently.  If there is none, this is  equivalent
	      to the parameter $0.  An integer may follow the `%' to specify a number of trailing
	      path components 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.

	      string is formatted using the strftime function.	See strftime(3) for more details.
	      Three  additional codes are available:  %f prints the day of the month, like %e but
	      without any preceding 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 without /dev/ prefix.  If name starts with
	      /dev/tty this is stripped.

       %y     The line (tty) the user is logged in on without /dev/ prefix.  It  does  not  treat
	      /dev/tty* specially.

       %?     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

       %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.

	      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 following:

	      ~      True if the current path, with prefix replacement, has at least n elements.
	      C      True if the current absolute path has at least n elements.
	      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.

	      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 displayed 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 `>' trun-
	      cate  at	the  right  of	the  string.   For  example,  if the current directory is
	      `/home/pike', the prompt `%8<..<%/' will expand to `..e/pike'.  In this string, the
	      terminating character (`<', `>' or `]'), or in fact any character, may be quoted by
	      a preceding `\'; note when using print -P, however, that this must  be  doubled  as
	      the  string  is also subject to standard print processing, in addition to any back-
	      slashes 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 trunca-
	      tion encountered at the same grouping level (i.e. truncations  inside  a	`%('  are
	      separate),  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 `#', fol-
	      lowed by a space.  Without the `%<<', those two characters would be included in the
	      string to be truncated.

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

zsh 4.0.6				 August 14, 2002			       ZSHMISC(1)

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