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flock on postfix /var/spool/mail/user

by abachus (Monk)
on Jun 01, 2006 at 12:46 UTC ( #553037=perlquestion: print w/replies, xml ) Need Help??

abachus has asked for the wisdom of the Perl Monks concerning the following question:

A very good day to you, you and you.

I would like to periodically read and empty users email spools in /var/spool/mail.

Postfix is the one doing the writing, as could be expected.

My thoughts are though, what happens if my shiney script truncates(and writes) to the spool at the same instance postfix wants to write new mail to that file.

Will the world end as we know it ? I just don't know, and i'm worried.

Therefore, my guess is to implement some sort of flock, hmmm, but which type exactly ? What kind of lock does postfix use (if any) ?

I'll bet there is a splendid module availible on cpan that i don't yet know of, i'm hopeful.


Isaac Close

Original question restored above for context by tye

Thanks guys, it seems to be the case that this is indeed a postfix thang. Now reading some postfix docs. on this topic.

Isaac Close
be good, if you can't be good be brilliant.

Replies are listed 'Best First'.
Re: flock on postfix /var/spool/mail/user
by gellyfish (Monsignor) on Jun 01, 2006 at 12:54 UTC

    This is more a question for a postfix forum but as I understand it postfix does use either flock or fcntl on most systems so it should be safe for you to use flock to get an exclusive lock on the file before processing it, however you may want to confirm that with the postfix documentation before relying on it.


Re: flock on postfix /var/spool/mail/user
by ruzam (Curate) on Jun 01, 2006 at 15:16 UTC
    Postfix will respect standard flock. It can also be configured to use '.lock' files if your spools live on NFS shares, (or flock just isn't working for you).
Re: flock on postfix /var/spool/mail/user
by ambrus (Abbot) on Jun 01, 2006 at 13:39 UTC

    I belive unix mail files use some other locking scheme than flock or fcntl, it's something with a separate lockfile, but I'm not sure how it works.

    Procmail has a utility called lockfile whose manpage might tell you something about this.

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