source: trunk/essentials/dev-lang/perl/pod/perlfaq8.pod@ 3368

=head1 NAME

perlfaq8 - System Interaction ($Revision: 1.27 $, $Date: 2005/12/31 00:54:37 $)

=head1 DESCRIPTION

This section of the Perl FAQ covers questions involving operating
system interaction.  Topics include interprocess communication (IPC),
control over the user-interface (keyboard, screen and pointing
devices), and most anything else not related to data manipulation.

Read the FAQs and documentation specific to the port of perl to your
operating system (eg, L<perlvms>, L<perlplan9>, ...).  These should
contain more detailed information on the vagaries of your perl.

=head2 How do I find out which operating system I'm running under?

The $^O variable ($OSNAME if you use English) contains an indication of
the name of the operating system (not its release number) that your perl
binary was built for.

=head2 How come exec() doesn't return?

Because that's what it does: it replaces your currently running
program with a different one.  If you want to keep going (as is
probably the case if you're asking this question) use system()
instead.

=head2 How do I do fancy stuff with the keyboard/screen/mouse?

How you access/control keyboards, screens, and pointing devices
("mice") is system-dependent.  Try the following modules:

=over 4

=item Keyboard

        Term::Cap               Standard perl distribution
        Term::ReadKey           CPAN
        Term::ReadLine::Gnu     CPAN
        Term::ReadLine::Perl    CPAN
        Term::Screen            CPAN

=item Screen

        Term::Cap               Standard perl distribution
        Curses                  CPAN
        Term::ANSIColor         CPAN

=item Mouse

        Tk                      CPAN

=back

Some of these specific cases are shown as examples in other answers
in this section of the perlfaq.

=head2 How do I print something out in color?

In general, you don't, because you don't know whether
the recipient has a color-aware display device.  If you
know that they have an ANSI terminal that understands
color, you can use the Term::ANSIColor module from CPAN:

    use Term::ANSIColor;
    print color("red"), "Stop!\n", color("reset");
    print color("green"), "Go!\n", color("reset");

Or like this:

    use Term::ANSIColor qw(:constants);
    print RED, "Stop!\n", RESET;
    print GREEN, "Go!\n", RESET;

=head2 How do I read just one key without waiting for a return key?

Controlling input buffering is a remarkably system-dependent matter.
On many systems, you can just use the B<stty> command as shown in
L<perlfunc/getc>, but as you see, that's already getting you into
portability snags.

    open(TTY, "+</dev/tty") or die "no tty: $!";
    system "stty  cbreak </dev/tty >/dev/tty 2>&1";
    $key = getc(TTY);           # perhaps this works
    # OR ELSE
    sysread(TTY, $key, 1);      # probably this does
    system "stty -cbreak </dev/tty >/dev/tty 2>&1";

The Term::ReadKey module from CPAN offers an easy-to-use interface that
should be more efficient than shelling out to B<stty> for each key.
It even includes limited support for Windows.

    use Term::ReadKey;
    ReadMode('cbreak');
    $key = ReadKey(0);
    ReadMode('normal');