merge-fifo

#!/usr/bin/perl

use Getopt::Long;
use IO::Select;
use IO::File;

die "usage: $0 FIFO-LIST

This allows you to merge multiple fifo outputs without causing a read 
block on one to prevent reading from the other (deadlock!)

Reads from ANY of the fifos in the list that are 
available.   If one blocks in the middle of a line, for 
example, this program will not block.
" unless @ARGV;

my $i = 0;
my @findex;
my @fbuf;
my $sel= IO::Select->new();
for my $file (@ARGV) {
    open($fin[$i],$file) || die "$file: $!\n";;
    $fin[$i]->blocking(0);
    $findex[fileno($fin[$i])]=$i;
    $sel->add($fin[$i]);
    ++$i;
}

my $closed = 0;
while ( @ready = $sel->can_read() ) {
    for my $h (@ready) {
        my $ret=sysread($h, $char, 1);

        if ($ret) {
            my $fn;
            $fbuf[$fn=fileno($h)] .= $char;
            if ($char eq "\n") {
                print $fbuf[$fn];
                $fbuf[$fn]="";
            }
        } else {
            $sel->remove($h);
            if (!$h->close()) {
                die "ERROR during close: $!\n";
            } else {
                ++$closed;
            }
        }
    }
}

if ($closed != @ARGV) {
        die "ERROR during merge\n";
}