=head1 NAME

history - Record of current and recently expired Usenet articles

=head1 DESCRIPTION

The file I<pathdb>/history keeps a record of all articles currently
stored in the news system, as well as those that have been received but
since expired.  In a typical production environment, this file will be
many megabytes.

The file consists of text lines.  Each line corresponds to one article.
The file is normally kept sorted in the order in which articles are
received, although this is not a requirement.  B<innd> appends a new
line each time it files an article, and B<expire> builds a new version
of the file by removing old articles and purging old entries.

Each line consists of two or three fields separated by a tab, shown
below as C< \t >:

    [hash] \t date
    [hash] \t date \t @token@

The I<hash> field is the ASCII representation of the hash of the
Message-ID.  This is directly used for the key of the I<dbz>.

The I<date> field consists of three sub-fields separated by a tilde.
All sub-fields are the text representation of the number of seconds
since the epoch, that is to say a I<time_t> like in C<gettimeofday(2)>.
The first sub-field is the article's arrival date.  If copies of the
article are still present, then the second sub-field is either the value
of the article's Expires header field, or a hyphen if no expiration
date was specified.  If an article has been expired, then the second
sub-field will be a hyphen.  The third sub-field is the value of the
article's Date header field, recording when the article was posted.

The I<token> field is a token of the article.  This field is empty if
the article has been expired.

For example, an article whose Message-ID was
<7q2saq$sal$1@isrv4.pa.vix.com>, posted on 26 Aug 1999 08:02:34 GMT
and received at 26 Aug 1999 08:06:54 GMT, could have a history line
(broken into three lines for display) like the following:

    [E6184A5BC2898A35A3140B149DE91D5C] \t
        935678987~-~935678821 \t
        @030154574F00000000000007CE3B000004BA@

In addition to the text file, there is a I<dbz> database associated
with the file that uses the Message-ID field as a key to determine the
offset in the text file where the associated line begins.  For historical
reasons, the key includes the trailing C<\0> byte (which is not stored
in the text file).

=head1 HISTORY

Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  Rewritten
into POD by Julien Elie.

=head1 SEE ALSO

expire(8), inn.conf(5), innd(8), libinn_dbz(3), makehistory(8).

=cut
