The goal was to read from a mailbox /var/spool/mail/foobar and write the content to someplace else, then truncate it. Logically, I need prevent the MTA from writing; sendmail uses no extraordinary locking according to the Flying Dog book.

Following is a modification of the code from perlopentut which I assumed to be safe. A coworker informed me we got data corruption, at "someplace else" a partial mail was written. The logfiles reveal nothing unusual.

use Fcntl qw(:DEFAULT :flock);
use IO::File;

# [...]

my $mbox = new IO::File $cMailBoxFile, O_RDWR or logthis("could not op
+en <$cMailBoxFile> for read/write: $!";
flock $mbox, LOCK_EX;
logthis("opened and locked <$cMailBoxFile>");

[download]
Does this create a race condition or do I have to look somewhere else for a possible explanation? Does IO::File, when used in this manner, use sysopen internally or not?

In reply to 5.8, locking with IO::File and Fcntl by Anonymous Monk

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