.TH history "5" "28-Feb-1994" "Version 4.50" "Reference"
.SH NAME
history - remember which articles arrived
.SH DESCRIPTION
.PP
.The
.B HISTORY
mechanism can be used to detect the arrival of articles that have
been received before.  This can happen if a system has more than
one news feeding host, with all these hosts sending articles.
Whenever the system receives an article, it adds a record about the
arrival to the
.B /usr/lib/news/history
file. This file contains lines of ASCII text, with the following
field definitions:
.sp 1
.ti +0.5i
.B "msgid<TAB>date<SPACE>time<TAB>newsgroup/artseqno"
.sp 1
So, the first field uniquely identifies a message.  The second field
forms the date and time at which the article arrived.  Finally, the
third (and last) field tells us where the article was stored.  Note,
that the name of the news group is written in NEWS style, not as a
UNIX path name.  Also note, that if an article was cross-posted to
more than one news group, there will be just as many entries of the
article in the history file.
.sp 1
A sample history file might look like this:
.sp 1
.nf
 <9091@star.cs.vu.nl>    02/28/91 19:15  comp.os.minix/731
 <6854@munnari.oz.au>    02/28/91 19:15  comp.os.minix/735
 <8492@plains.NoDak.edu> 02/28/91 19:16  comp.os.minix/750
.fi
.sp 1
The history file is also updated by the
.B cancel
control message.  The program that executes this message simply
reads through the history file, and removes all occurrences of
a certain article on the disks.  It also removes their entries
in the history file.
.sp 1
Note, that this feature is relatively expensive in terms of both
disk space usage and CPU cycle demand.  Use it only when you
really think you need it.  Usually, the news host takes care of
cancelling articles!
.PP
As of
.B WNEWS
version 4.4.3, it is possible that your system also uses a \fIdbm\fP
type database for the history file. This speeds up posting articles
with \fIinews\fP(8) a lot!
.SH FILES
.nf
/usr/lib/news/history \fBor\fP /var/adm/news/history
.fi
.SH AUTHOR
.nf
Fred N. van Kempen, waltje@Infomagic.COM
.fi
.SH "SEE ALSO"
.nf
mkhist(8)
.fi
