(shell-command command)
Invokes the system shell to execute command, which must be a string. This procedure returns the exit status of the shell in the form that the C library’s system routine returns.
(system-command command arg0 arg ...)
Invokes command directly, passing arg0 as the zeroth argument and args as the additional arguments. All arguments must be strings. This procedure returns the exit status of command.
(system-command-with-environment command environment arg0 arg ...)
Same as system-command, but passes environment (which must be an a-list mapping strings to strings) as the environment.