=over

=item system LIST
X<system> X<shell>

=item system PROGRAM LIST

Does exactly the same thing as C<exec LIST>, except that a fork is
done first, and the parent process waits for the child process to
complete.  Note that argument processing varies depending on the
number of arguments.  If there is more than one argument in LIST,
or if LIST is an array with more than one value, starts the program
given by the first element of the list with arguments given by the
rest of the list.  If there is only one scalar argument, the argument
is checked for shell metacharacters, and if there are any, the
entire argument is passed to the system's command shell for parsing
(this is C</bin/sh -c> on Unix platforms, but varies on other
platforms).  If there are no shell metacharacters in the argument,
it is split into words and passed directly to C<execvp>, which is
more efficient.

Beginning with v5.6.0, Perl will attempt to flush all files opened for
output before any operation that may do a fork, but this may not be
supported on some platforms (see L<perlport>).  To be safe, you may need
to set C<$|> ($AUTOFLUSH in English) or call the C<autoflush()> method
of C<IO::Handle> on any open handles.

The return value is the exit status of the program as returned by the
C<wait> call.  To get the actual exit value, shift right by eight (see
below). See also L</exec>.  This is I<not> what you want to use to capture
the output from a command, for that you should use merely backticks or
C<qx//>, as described in L<perlop/"`STRING`">.  Return value of -1
indicates a failure to start the program or an error of the wait(2) system
call (inspect $! for the reason).

Like C<exec>, C<system> allows you to lie to a program about its name if
you use the C<system PROGRAM LIST> syntax.  Again, see L</exec>.

Since C<SIGINT> and C<SIGQUIT> are ignored during the execution of
C<system>, if you expect your program to terminate on receipt of these
signals you will need to arrange to do so yourself based on the return
value.

    @args = ("command", "arg1", "arg2");
    system(@args) == 0
	 or die "system @args failed: $?"

You can check all the failure possibilities by inspecting
C<$?> like this:

    if ($? == -1) {
	print "failed to execute: $!\n";
    }
    elsif ($? & 127) {
	printf "child died with signal %d, %s coredump\n",
	    ($? & 127),  ($? & 128) ? 'with' : 'without';
    }
    else {
	printf "child exited with value %d\n", $? >> 8;
    }

Alternatively you might inspect the value of C<${^CHILD_ERROR_NATIVE}>
with the W*() calls of the POSIX extension.

When the arguments get executed via the system shell, results
and return codes will be subject to its quirks and capabilities.
See L<perlop/"`STRING`"> and L</exec> for details.

=back