File locking of mboxrd-format mbox file

[Ian Zimmerman]

On 2019-06-29 15:24, Frank Watt wrote:

> My question is: how do I know what type of file locking that has been
> in use all these years of using fetchmail?

AFAIK the default mode for fetchmail is not to touch the mailbox file
itself at all, but either deliver the message via SMTP to port 25 on
localhost, or pipe it to a MDA such as procmail.  So your question may
be a bit confused and you should have asked about _procmail_, not
fetchmail. 

I happen to know that procmail tries to lock the file in _all_ the ways
available on the system, for instance on Linux with a dotlock temporary
file, with flock, and with fcntl.  This is a bit overkill but it means
procmail is safe to use as long as the other program accessing the
mailbox uses any locking at all.

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