Synopsis:
   set shell [<program>]

Description:
   When the EXEC command is used, the program named in this variable is
   spawned to execute the desired command.  This is generally a command
   shell of some sort, though it doesn't necessarily have to be one.

   If the shell requires special command-line switches, they may be given
   in the SHELL_FLAGS variable.

See Also:
   exec(5); set(4) shell_flags