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Path: utzoo!linus!philabs!cmcl2!seismo!ut-sally!utastro!gary
From: gary@utastro.UUCP (Gary Hansen)
Newsgroups: net.sources
Subject: 7 chr self duplicator
Message-ID: <502@utastro.UUCP>
Date: Fri, 7-Sep-84 14:28:26 EDT
Article-I.D.: utastro.502
Posted: Fri Sep  7 14:28:26 1984
Date-Received: Sun, 16-Sep-84 08:18:17 EDT
Distribution: net
Organization: UTexas Astronomy Dept., Austin, Texas
Lines: 6

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Try this shortest yet self duplicator:
cat $0
It works with both sh and csh and is only 7 characters in length.