#!/local/bin/perl
#

use Getopt::Long;
GetOptions(qw(read write debug file:s));

die "No file specified" if (!$opt_file);

print "file: $opt_file\n";

open(BLAH, ">$opt_file");
if ($opt_read) {
    $rc = read_lock('BLAH');
} elsif ($opt_write) {
    $rc = write_lock('BLAH');
} else {
    die "No lock method defined.";
}

print "Return lock - $rc\n" if ($opt_debug);

chop($junk=<STDIN>);

$rc = clr_lock('BLAH');
print "Return clr - $rc\n" if ($opt_debug);
close(BLAH);

#
# File locking defines
sub LOCK_SH { 1; }
sub LOCK_EX { 2; }
sub LOCK_NB { 4; }
sub LOCK_UN { 8; }

#
# Shared lock on a file - flock() should be okay everywhere (see perlfunc)
sub read_lock {
    my($fh)=shift;
    print "SH_LOCKing $fh\n" if ($opt_debug);
    return flock($fh, LOCK_SH());
}

sub write_lock {
    my($fh)=shift;
    print "EX_LOCKing $fh\n" if ($opt_debug);
    return flock($fh, LOCK_EX());
}

sub clr_lock {
    my($fh)=shift;
    print "UN_LOCKing $fh\n" if ($opt_debug);
    return flock($fh, LOCK_UN());
}