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).  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.  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.
       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.
