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Re^5: Quick Question - Append File at Beginning?

by afoken (Parson)
on Nov 17, 2013 at 11:47 UTC ( #1062988=note: print w/ replies, xml ) Need Help??


in reply to Re^4: Quick Question - Append File at Beginning?
in thread Quick Question - Append File at Beginning?

How does *NIX MBOX deal with data? Would the way it does it, offer some interesting methods.

Are you refering to "the" mbox mail box file format? (See Wikipedia, qmail.org, Jonathan de Boyne Pollard, RFC 4155)

Well, actually, there are serveral slightly incompatible formats, and they all are essentially append-only formats. A variant is used by Netscape's Communicator and its derivates (Thunderbird, Seamonkey). It has a separate index file containing the file offsets of the e-mails in the mbox file and some other data. "Compacting" the mailbox just rewrites the entire mbox file, omitting all e-mails flagged as deleted. (See http://www.jwz.org/doc/mailsum.html.) Mail servers using the mbox format probably do something similar. I remember one old server at my university that kept a special first message in the mbox files, invisible via POP3 and IMAP. Parts of this message were constantly overwritten to keep track of changes to the mbox file. I think that some of my old linux machines behaved the same until I've switched to imapdir several years ago.

So, perhaps the only useful ideas from mbox are a second file containing a list of file offsets into the main file, and a special (fixed size) directory record at the beginning of the main file.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)


Comment on Re^5: Quick Question - Append File at Beginning?
Re^6: Quick Question - Append File at Beginning?
by taint (Chaplain) on Nov 17, 2013 at 19:33 UTC
    Right you are afoken.

    My bad. I'm afraid I had an incorrect association in my head. I had viewed a couple of mailboxes in the past, and somehow remembered that new entries were pushed to the top of the stack. I imagine my *incorrect* recollection stems from the fact, my reader sorts the order *reversed*.

    Thanks for the correction, afoken.

    Next time, I'll take the time to confirm my thoughts before posting them. :P

    --Chris

    #!/usr/bin/perl -Tw
    use Perl::Always or die;
    my $perl_version = (5.12.5);
    print $perl_version;

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