Why is wtmp so big?

[Aryeh M. Weiss]

In article <413 at tabbs.UUCP> aris at tabbs.UUCP (Aris Stathakis) writes:
> ...
>
>Is there perhaps any program out there ther truncates the /etc/wtmp
>file to the 100 most recent entries?  
>
>Since it is a binary file, this is no trivial task.
               ^^^^^^
>
>Thanks in advance.
>
>Aris
>
>-- 
>Aris Stathakis | Bang: ..!uunet!ddsw1!olsa99!tabbs!aris or aris at tabbs.UUCP
>         - Gimme a beer and money sandwich....  Hold the bread -
>                                                  - Waldo (D.R.) Dobbs

Since it IS a binary file, it IS a trivial task -- all records in the
file are the same size.  I don't know the record size off hand, but you could
use something like "dd":

if file is big then
	dd if=/etc/wtmp of=/tmp/wtmp bs=<record-size> \
	    skip=<(file-size/record-size) - 100> count=100
	mv /tmp/wtmp /etc/wtmp
endif

Of course you need to know the record-size and file-size but these can be 
figured out by suitable means.

-- 
eliot%lees-rif at eddie.mit.edu (Eliot H. Frank)