FAQ 8.5 How do I read just one key without waiting for a return key?

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8.5: 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 stty command as shown in "getc" in
    perlfunc, but as you see, that's already getting you into portability

        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 stty for each key. It even
    includes limited support for Windows.

        use Term::ReadKey;
        $key = ReadKey(0);

    However, using the code requires that you have a working C compiler and
    can use it to build and install a CPAN module. Here's a solution using
    the standard POSIX module, which is already on your systems (assuming
    your system supports POSIX).

        use HotKey;
        $key = readkey();

    And here's the HotKey module, which hides the somewhat mystifying calls
    to manipulate the POSIX termios structures.

        # HotKey.pm
        package HotKey;

        @ISA = qw(Exporter);
        @EXPORT = qw(cbreak cooked readkey);

        use strict;
        use POSIX qw(:termios_h);
        my ($term, $oterm, $echo, $noecho, $fd_stdin);

        $fd_stdin = fileno(STDIN);
        $term     = POSIX::Termios->new();
        $oterm     = $term->getlflag();

        $echo     = ECHO | ECHOK | ICANON;
        $noecho   = $oterm & ~$echo;

        sub cbreak {
            $term->setlflag($noecho);  # ok, so i don't want echo either
            $term->setcc(VTIME, 1);
            $term->setattr($fd_stdin, TCSANOW);

        sub cooked {
            $term->setcc(VTIME, 0);
            $term->setattr($fd_stdin, TCSANOW);

        sub readkey {
            my $key = '';
            sysread(STDIN, $key, 1);
            return $key;

        END { cooked() }



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