A script called, among other things, backfinger, planner, and
finger_logger (flogger or frogger, for short), makes your .plan into
a named pipe. Think of a named pipe as being a sort of pipe used with
plumbing that opens on the screen of the person who is fingering you
- say, Fred - so that when the .plan file (a named pipe) is accessed,
it looks for a program from which to get something to stick on Fred's
screen. The script is called when you are fingered. At that moment,
the script looks to the finger port of your UNIX machine, sees which
machine Fred is on, and logs that machine's IP number and host name.
The script then can execute a command to spit out a .plan on Fred's
screen.  You could use a program that generates random poetry, the
fortune program, or simply "cat plan_file" to make the contents of
the text file (plan_file) appear on Fred's screen.  To make Fred
think that you are really cool, the script also tells him what
machine he is fingering you from.

This script tells you only the machine that Fred is fingering you
from, not his actual user name. Although the identification protocol
(documented in RFC1413) allows exchange of the user name that
initiated the finger process over port 113, the current backfinger
program does not use it. (Anyone who has enough time to add this
feature certainly may, though!) The other way to find out Fred's name
is to use systat, which requests a list of current processes on
Fred's machine over port 11. This option rarely is available, due to
security concerns.  

Following are two caveats:

 * This program must be running at all times on your system, even
   when you are logged out. Leaving on a background process like this
   one annoys most system administrators no end, especially on
   high-load systems. Do not run the program unless you are sure that
   you are allowed to run background processes.

 * If you decide that you want to stop running this program, remove
   your .plan file as soon as you kill the process; otherwise, all
   your finger processes will hang.

Given these caveats, the script is distributed only to those who can
use it, mostly for educational reasons. The Web site is
http://pubweb.acns.nwu.edu/~jrosen/scripts/logger.src.

Note: I am not the author of this program; the version that I
distribute is virtually identical to the program distributed by Steve
Franklin. The real author is Tony Rems (rembo@unisoft.com).
Modifications and revisions were made by Geoff Loker
(geoff@mdms.moore.com), Karen Bruner (napalm@ugcs.caltech.edu),
Norman Franke (franke1@llnl.gov), and Steve Franklin
(franklin@ug.cs.dal.ca).

SEE ALSO
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Newsgroup: comp.sources.misc