Acting on the assumption that you want to use semaphore files to lock and unlock files with Perl:

use Fcntl 'LOCK_EX';

=head2 C<sem_lock>

Pass C<sem_lock> a file name and will will add a .sem extension, open 
+the
semaphore (creating if necessary), and get an exclusive lock on the fi
+le.  The
function returns a file handle that should be passed to sem_unlock() t
+o unlock
the file.  If the program terminates, the file will be unlocked automa
+tically.

=cut

sub sem_lock
{
    my $sem_file = shift || die "No file specified";
    $sem_file .= '.sem';
    open my $fh, ">", $sem_file or die "Cannot open semaphore $sem_fil
+e: $!";
    flock $fh, LOCK_EX          or die "Cannot get exclusive lock on $
+sem_file: $!";
    return $fh;
}

=head2 C<sem_unlock>

Pass C<sem_unlock> a file handle and it will close it.  It returns tru
+e or false
depending on success or failure.  It doesn't I<unlock> the file as thi
+s happens
automatically when a file is closed.  This function is primarily just 
+to
complement C<sem_lock>.

=cut

sub sem_unlock
{
    my $fh = shift;
    close $fh or return 0;
    return 1;
}
[download]

Basically, with a given filename, sem_lock the filename and then use the file as normal. After you are done, sem_unlock the filehandle returned by sem_lock. There are variants of this you can use (such as creating a semaphore locking object and calling an unlock method).

Cheers,
Ovid

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