emulate [ -lLR ] [ {zsh|sh|ksh|csh} [ flags ... ] ]
       Without any argument print current emulation mode.

       With single argument set up zsh options to emulate the specified
       shell  as  much  as possible.  csh will never be fully emulated.
       If the argument is not one of the shells listed above, zsh  will
       be used as a default; more precisely, the tests performed on the
       argument are the same as those used to determine  the  emulation
       at  startup based on the shell name, see the section COMPATIBIL-
       ITY in zsh(1) .  In addition to setting shell options, the  com-
       mand  also restores the pristine state of pattern enables, as if
       all patterns had been enabled using enable -p.

       If the emulate command occurs inside a function  that  has  been
       marked  for  execution tracing with functions -t then the xtrace
       option will be turned on regardless of emulation mode  or  other
       options.   Note that code executed inside the function by the .,
       source, or  eval  commands  is  not  considered  to  be  running
       directly  from  the function, hence does not provoke this behav-
       iour.

       If the -R switch is given, all settable  options  are  reset  to
       their  default  value  corresponding  to the specified emulation
       mode, except for  certain  options  describing  the  interactive
       environment;  otherwise,  only  those  options  likely  to cause
       portability problems in scripts and functions are  altered.   If
       the  -L  switch  is given, the options LOCAL_OPTIONS, LOCAL_PAT-
       TERNS and LOCAL_TRAPS will be set as well, causing  the  effects
       of  the emulate command and any setopt, disable -p or enable -p,
       and trap commands to be local  to  the  immediately  surrounding
       shell function, if any; normally these options are turned off in
       all emulation modes except ksh. The -L switch is mutually exclu-
       sive with the use of -c in flags.

       If  there  is  a single argument and the -l switch is given, the
       options that would be set or unset (the  latter  indicated  with
       the  prefix  `no') are listed.  -l can be combined with -L or -R
       and the list will be modified in the appropriate way.  Note  the
       list  does not depend on the current setting of options, i.e. it
       includes all options that may  in  principle  change,  not  just
       those that would actually change.

       The  flags  may be any of the invocation-time flags described in
       the section INVOCATION in zsh(1), except that `-o EMACS' and `-o
       VI'  may not be used.  Flags such as `+r'/`+o RESTRICTED' may be
       prohibited in some circumstances.

       If -c arg appears in flags, arg is evaluated while the requested
       emulation  is temporarily in effect.  In this case the emulation
       mode and all options  are  restored  to  their  previous  values
       before  emulate  returns.  The -R switch may precede the name of
       the shell to emulate; note this  has  a  meaning  distinct  from
       including -R in flags.

       Use  of -c enables `sticky' emulation mode for functions defined
       within the evaluated expression:  the emulation mode is  associ-
       ated  thereafter with the function so that whenever the function
       is executed the emulation (respecting the -R switch, if present)
       and  all  options  are set (and pattern disables cleared) before
       entry to the function, and the state is restored after exit.  If
       the  function  is called when the sticky emulation is already in
       effect, either within an `emulate shell -c' expression or within
       another  function with the same sticky emulation, entry and exit
       from the function do not cause options to be altered (except due
       to  standard processing such as the LOCAL_OPTIONS option).  This
       also applies to functions marked for autoload within the  sticky
       emulation; the appropriate set of options will be applied at the
       point the function is loaded as well as when it is run.

       For example:

              emulate sh -c 'fni() { setopt cshnullglob; }
              fno() { fni; }'
              fno

       The two functions fni and fno are defined with sticky sh  emula-
       tion.   fno  is  then  executed, causing options associated with
       emulations to be set to their values in sh.  fno then calls fni;
       because  fni  is  also marked for sticky sh emulation, no option
       changes take place on entry to  or  exit  from  it.   Hence  the
       option  cshnullglob,  turned off by sh emulation, will be turned
       on within fni and remain on return to fno.  On  exit  from  fno,
       the emulation mode and all options will be restored to the state
       they were in before entry to the temporary emulation.

       The documentation above is typically sufficient for the intended
       purpose  of  executing code designed for other shells in a suit-
       able environment.  More detailed rules follow.
       1.     The sticky emulation  environment  provided  by  `emulate
              shell  -c'  is  identical  to that provided by entry to a
              function marked for sticky emulation as a consequence  of
              being  defined  in such an environment.  Hence, for exam-
              ple, the sticky emulation is  inherited  by  subfunctions
              defined within functions with sticky emulation.
       2.     No change of options takes place on entry to or exit from
              functions that are not marked for sticky emulation, other
              than  those that would normally take place, even if those
              functions are called within sticky emulation.
       3.     No special handling is provided for functions marked  for
              autoload nor for functions present in wordcode created by
              the zcompile command.
       4.     The presence or absence of the -R switch to emulate  cor-
              responds  to  different  sticky  emulation  modes, so for
              example `emulate sh -c', `emulate -R sh -c' and  `emulate
              csh -c' are treated as three distinct sticky emulations.
       5.     Difference  in  shell options supplied in addition to the
              basic emulation also mean the sticky emulations are  dif-
              ferent,  so for example `emulate zsh -c' and `emulate zsh
              -o cbases -c' are treated as distinct sticky emulations.
