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  di-
       rectly from the function, hence does not provoke this behaviour.

       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 en-
       vironment; otherwise, only those options likely to cause  porta-
       bility problems in scripts and functions are altered.  If the -L
       switch  is  given, the options LOCAL_OPTIONS, LOCAL_PATTERNS and
       LOCAL_TRAPS will be set as well, causing the effects of the emu-
       late command and any setopt, disable -p or enable -p,  and  trap
       commands  to be local to the immediately surrounding shell func-
       tion, if any; normally these options are turned off in all  emu-
       lation  modes  except  ksh.  The -L switch is mutually exclusive
       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 be-
       fore emulate returns.  The -R switch may precede the name of the
       shell to emulate; note this has a meaning distinct from  includ-
       ing -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 em-
       ulations 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  op-
       tion  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 ex-
              ample `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.
