#!/usr/bin/perl -w

# Prints the PID of a process that is holding a lock on the file
# $ARGV[0].  Surely there's a better way to get locker info?
# Something like /proc/timer_list is for sleeps/timeouts?

use Fcntl;

$lock_format = "s2l5"; # For the Linux 64-bit interface

sysopen(FD, $ARGV[0], O_RDONLY) or die "open $!";
$fs = pack($lock_format, F_RDLCK, 0, 0, 0, 1, 1, 0);
fcntl(FD, F_GETLK, $fs) or die "fcntl $!";
print((unpack $lock_format, $fs)[6] . "\n");