emulate [ -LR ] [ {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) .

       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   and
       LOCAL TRAPS will be set as well, causing the effects of the emu-
       late command and any setopt 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 exclusive with the use of -c in flags.

       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  before  entry  to the function, and
       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).

       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.  fni then calls fno;
       because fno 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.
