[Python-Dev] cpython (2.7): #9559: Append data to single-file mailbox files if messages are only added

[Petri Lehtinen]

R. David Murray wrote:
> It is true, however, that Petri found that mutt (I think?) does some extra
> gymnastics to provide recovery where the write fails part way through,
> and it would be worth adding that as an enhanced bugfix if someone
> has the motivation (basically, make a copy of the unmodified mailbox
> and mv it back into place if the write fails).

This is not what mutt does. It just writes the modified part of the
mailbox to a temporary file, and then copies the data from the
temporary file to the mailbox file. If this last step fails, the
temporary file is left behind for recovery.

Copying the whole mailbox before making modifications might be clever,
though. It's just quite a lot of writing, especially for big
mailboxes. OTOH, the whole file is rewritten by the current code, too.