The shell command spawns an interactive shell. To return to gnuplot,
type logout if using VMS, exit or the END-OF-FILE character if using
Unix, endcli if using AmigaOS, or exit if using MS-DOS or OS/2.
A single shell command may be spawned by preceding it with the ! character
($ if using VMS) at the beginning of a command line. Control will return
immediately to gnuplot after this command is executed. For example, in
Unix, AmigaOS, MS-DOS or OS/2,
! dir
prints a directory listing and then returns to gnuplot.
On an Atari, the ! command first checks whether a shell is already loaded
and uses it, if available. This is practical if gnuplot is run from
gulam, for example.