IPC and counters

[Paul Makepeace]

On Thu, Oct 16, 2008 at 7:36 AM, Philip Newton <philip.newton at gmail.com> wrote:
> On Wed, Oct 15, 2008 at 02:01, Simon Wistow <simon at thegestalt.org> wrote:
>>     Child:
>>
>>     my ($msg, $sem_id)  = get_message();
>>     my $sem = IPC::Semaphore->new($sem_id);
>>     if (0 == $sem->op(0, -1, IPC_NOWAIT)) {
>>         do_something($message);
>>     }
>>
>>     # If we're the last then clean up
>>     if (EAGAIN == $sem->op(1,-1, IPC_NOWAIT)) {
>>         $sem->remove;
>>     }
>
> Does the module really export no constants for this "0, 1, -1" stuff?

The first arg is the semaphore number, the second is what to do with
it: acquire (-1)/release (+1) the semaphore or wait for it to be full
(0).

http://www.linuxhq.com/guides/LPG/node52.html

> It all seems rather error-prone to me.
>
> Cheers,
> --
> Philip Newton <philip.newton at gmail.com>
>