How can I test STDIN without blocking in Perl?

Question

I\'m writing my first Perl app -- an AOL Instant Messenger bot that talks to an Arduino microcontroller, which in turn controls a servo that will push the power button on our sy

Answer 1

I found that IO::Select works fine as long as STDOUT gets closed, such as when the upstream process in the pipeline exits, or input is from a file. However, if output is ongoing (such as from "tail -f") then any partial data buffered by will not be displayed. Instead, use the unbuffered sysread:

#!/usr/bin/perl
use IO::Select;
$s = IO::Select->new(\*STDIN);

while (++$i) {
        if ($s->can_read(2)) {
                last unless defined($foo=get_unbuf_line());
                print "Got '$foo'\n";
        }
}

sub get_unbuf_line {
        my $line="";
        while (sysread(STDIN, my $nextbyte, 1)) {
                return $line if $nextbyte eq "\n";
                $line .= $nextbyte;
        }
        return(undef);
}