Script to list master/slave pseudoterminal ends on Linux

pty_ends.pl

use strict;
use warnings;

print "MASTER\tSLAVES\n";
my $pid = -1;
for my $master_end (qx#lsof -F pcf /dev/ptmx#) {
    chomp $master_end;
    if ($master_end =~ /p.*/) {
        print "\n" if $pid>0;
        $pid = substr($master_end, 1);
        print "$pid,";
    } elsif ($master_end =~ /c.*/) {
        print substr($master_end, 1)."\t";
    }
    elsif ($master_end =~ /f.*/) {
        # a file descriptor for current pid
        my $fd = substr($master_end, 1);
        readfile("/proc/$pid/fdinfo/$fd") =~ /^tty-index:\s*(\d+)$/m;
        my $slave_processes = qx#ps -o "%p,%c" -t pts/$1#;
        $slave_processes =~ s/^(?:.*\n)//;
        $slave_processes =~ s/^\s*//;
        $slave_processes =~ s/\n/\t/g;
        print "$slave_processes";
    }
}
sub readfile { local $/; my $h; open $h, '<', shift and <$h> }
print "\n";