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 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.
