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From: oscar@utcsrgv.UUCP (Oscar M. Nierstrasz)
Newsgroups: net.misc
Subject: self-printing programs
Message-ID: <2933@utcsrgv.UUCP>
Date: Tue, 13-Dec-83 18:34:40 EST
Article-I.D.: utcsrgv.2933
Posted: Tue Dec 13 18:34:40 1983
Date-Received: Tue, 13-Dec-83 19:29:32 EST
Organization: CSRG, University of Toronto
Lines: 29

Here's a puzzle!  (Perhaps this belongs in net.jokes ...)

What is the shortest program you can come up with whose only output is
the program itself?

Trivial solutions are not acceptable -- the null program will obviously
do the trick.  Similarly, it must not access any external text or data
files since the shell script

	cat $0

simply reads and prints itself.  Clearly all the "data" must be
contained in the program itself.  A shell script containing

	self

where "self" is a shell script that does an "echo self" is also
cheating.

So far I have a three-line shell script that seems to fit the bill.
Any takers for this mind-bender?  Please *mail* me and I'll post the
cleverest solutions after a decent wait.  (Programs are fine, but shell
scripts tend to be shorter.)

Oscar Nierstrasz
-- 

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