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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,, 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 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.


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

In reply to Re^5: Quick Question - Append File at Beginning? by afoken
in thread Quick Question - Append File at Beginning? by jdlev

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