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From: ted@ecr2.UUCP (Ted Richards)
Newsgroups: net.unix
Subject: Re: AWK question
Message-ID: <140@ecr2.UUCP>
Date: Thu, 8-Aug-85 12:15:43 EDT
Article-I.D.: ecr2.140
Posted: Thu Aug  8 12:15:43 1985
Date-Received: Sat, 10-Aug-85 01:19:53 EDT
References: <436@brl-tgr.ARPA>
Organization: Emerald City Research Inc., Toronto
Lines: 10

The problem with the statement

	awk '$5 >= $dt' ...

is that the "$dt" is inside single quotes and gets passed literally to awk.
What you want is for the shell to expand the "$dt" (but not the "$5"!).
Try something like:

	echo '$5 >=' $dt >/tmp/whatever
	awk -f /tmp/whatever ...