Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!convex!usenet
From: tchrist@convex.COM (Tom Christiansen)
Newsgroups: comp.lang.misc
Subject: Re: awk
Message-ID: <1991Apr10.181844.2649@convex.com>
Date: 10 Apr 91 18:18:44 GMT
References: <1182@junkyard.UUCP>
Sender: usenet@convex.com (news access account)
Reply-To: tchrist@convex.COM (Tom Christiansen)
Organization: CONVEX Software Development, Richardson, TX
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Nntp-Posting-Host: pixel.convex.com

From the keyboard of hal@junkyard.UUCP (Hal Moroff):
:
:	I'm trying to use awk to read an ascii file, and translate only
:certain fields.  I have my own special filter that will be used for the
:translation.

This is the old double-headed popen() problem.  Your best
bet is to write it all to a temp file, then read from the
file when done.  This is the best way to avoid deadlock.  

You could theoretically use some forks, dups, and execs
do get this all right, but unless you are sure of the 
behavior of the inferior, you can't guarantee that you'll
be free of deadlock.   Of course, awk won't let you do these
things, nor could you flush the pipe if you wanted to.  
You might look at question 20 of the Frequently Asked
Questions list in comp.lang.perl -- perl code is included
there for doing this, and the algorithm is easily translatable
into C.  But awk users are at a dead-end.

--tom