#!/usr/bin/perl

use IO::File;
use Fcntl qw(:DEFAULT :flock);

print "opening file1\n";
  my $fh1 = new IO::File("file1",O_RDONLY | O_CREAT);
print "locking file1\n";
  flock($fh1,LOCK_EX) or die "failed to lock file1";
print "opening file2\n";
  my $fh2 = new IO::File("file2",O_WRONLY | O_CREAT);
print "writing to file2\n";
  print $fh2 "file2";
  close($fh2);
print "renaming file2 over file1\n";
  rename("file2","file1") or die "failed to rename file2 over file1";
print "unlocking file1\n";
 #flock($fh1,LOCK_UN);#probably not needed as close does it
                                 #(might cause issues with buffering?)
 close($fh1);