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perlinput

Perl do input one char from stdin

How can Perl do input from stdin, one char like

readline -N1

does?

Solution

  • You can do that with the base perl distribution, no need to install extra packages:

    use strict;
sub IO::Handle::icanon {
        my ($fh, $on) = @_;
        use POSIX;
        my $ts = new POSIX::Termios;
        $ts->getattr(fileno $fh) or die "tcgetattr: $!";
        my $f = $ts->getlflag;
        $ts->setlflag($on ? $f | ICANON : $f & ~ICANON);
        $ts->setattr(fileno $fh) or die "tcsetattr: $!";
}

# usage example
# a key like `Left` or `á` may generate multiple bytes
STDIN->icanon(0);
sysread STDIN, my $c, 256;
STDIN->icanon(1);
# the read key is in $c

    Reading just one byte may not be a good idea because it will just leave garbage to be read later when pressing a key like Left or F1. But you can replace the 256 with 1 if you want just that, no matter what.