in reply to Order of flock and open

I'm surprised no one has pointed you to sysopen(), rather than the simpler open() function.

From the perlopentut tutorial:

To get an exclusive lock, typically used for writing, you have to be careful. We sysopen the file so it can be locked before it gets emptied. You can get a nonblocking version using LOCK_EX | LOCK_NB. 
    use 5.004; # make sure you have at least this level perl
    use Fcntl qw(:DEFAULT :flock);
    sysopen(FH, "filename", O_WRONLY | O_CREAT)
        or die "can't open filename: $!";
    flock(FH, LOCK_EX)
        or die "can't lock filename: $!";
    truncate(FH, 0)
        or die "can't truncate filename: $!";
    # now write to FH

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[Jon]

Replies are listed 'Best First'.
Re: Re: Order of flock and open
by mdog (Pilgrim) on May 01, 2003 at 20:33 UTC
    Personally, I like LockFile::Simple.

    Works great for me... 
    use LockFile::Simple qw(lock trylock unlock);

$lockmgr = LockFile::Simple->make(-format => '%f.lck',
    -max => 20, -delay => 1, -stale => 1);
    
# first program to get the lock the file gets the chance to run it    
+       
if($lockmgr->trylock("$eventsLogFile")){

    my @bytes= split(//, $serial_data); 
    $lockmgr->unlock("$eventsLogFile");
}

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[d/l]

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