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Best way to control multiple threads writing & reading from the same file (Perl)

Posted on 2010-11-27
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Last Modified: 2012-05-10
Expertos,

What's the best way to control multiple threads writing & reading from the same file in Perl?

I'm working with the threads::simple module.

Thanks!

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Question by:php-newbie
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Justin Mathews earned 2000 total points
ID: 34230935
You can use flock() to lock a file handle in exclusive or shared mode. So each thread can call flock() to acquire an exclusive lock before writing to the file and immediately release the lock so that other threads also can obtain a lock and write to the file. Here is the sample from the documentation (http://perldoc.perl.org/functions/flock.html):



use Fcntl ':flock'; # import LOCK_* constants

sub lock {
    flock(MBOX,LOCK_EX);
    # and, in case someone appended
    # while we were waiting...
    seek(MBOX, 0, 2);
}

sub unlock {
    flock(MBOX,LOCK_UN);
}

open(MBOX, ">>/usr/spool/mail/$ENV{'USER'}")
        or die "Can't open mailbox: $!";

lock();
print MBOX $msg,"\n\n";
unlock();

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