# Returns the process id currently stored in the file set.  If the method
# is passed a file handle, it will return the value, leaving the file handle
# locked.  This is useful for atomic operations where the caller needs to
# write to the file after the read without allowing other dirty writes.
# 
# Please note, when passing a file handle, caller is responsible for
# closing it. Also, file handles must be passed by reference!

sub read {
	my ($self, $fh) = @_;

	sysopen($fh, $self->{path}, O_RDWR|O_CREAT)
		|| die qq/Cannot open pid file "$self->{path}": $!\n/;
	flock($fh, LOCK_EX | LOCK_NB)
        || die qq/pid "$self->{path}" already locked: $!\n/;
# WARNING: Use of uninitialized value in pattern match (m//):
	my ($pid) = <$fh> =~ /^(\d+)/;
	close $fh if @_ == 1;

	$self->debug("read(\"$self->{path}\") = " . ($pid || ""));
	return $pid;
	}