=head1 NAME

prunehistory - Remove tokens from Usenet history file

=head1 SYNOPSIS

B<prunehistory> [B<-p>] [B<-f> I<filename>]

=head1 DESCRIPTION

B<prunehistory> modifies a history(5)-format text file to "remove"
a set of tokens from it.  The tokens are removed by overwriting
them with spaces, so that the size and position of any following entries
does not change.  This has an effect similar to expiring the article, in
that it is still mentioned in the history database but cannot be retrieved.

This program only works with the C<hisv6> history storage method.

B<prunehistory> reads the standard input.  The input is taken as a set of
lines.  Blank lines and lines starting with a number sign (C<#>) are ignored.
All other lines should consist of a message-ID followed by zero or more other
fields (which are ignored).  The message-ID is used as the I<dbz> key to get
an offset into the text file.  Since B<innd> only appends to the text file,
B<prunehistory> does not need to have any interaction with it.

=head1 OPTIONS

=over 4

=item B<-p>

B<prunehistory> will normally complain about lines that do not follow
the correct format.  If the B<-p> flag is used, then the program will
silently print any invalid lines on its standard output.  (Blank lines
and comment lines are also passed through.)

=item B<-f> I<filename>

The default name of the F<history> file is I<pathhistory>/F<history>; to
specify a different name, use the B<-f> flag.

=back

=head1 HISTORY

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

=head1 SEE ALSO

history(5), innd(8), libinn_dbz(3).

=cut
