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From: peter@citylink.dinoex.sub.org (Peter Much)
Message-Id: <199512070201.DAA03870@citylink.dinoex.sub.org>
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Subject: awk (2.1-STABLE): close() misfunctional?
To: freebsd-hackers@freebsd.org
Date: Thu, 7 Dec 1995 03:01:35 +0100 (MET)
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Please check if you can reproduce the following - maybe there was
a compilation error, since i did install from the source-tree above
some older SNAP.
-------------------------------------------------------------------
Usually, if one prints onto a pipe from awk with something like

  print something | "some shellscript"

and afterwards closes the pipe with

  close ("some shellscript")

, this will make the pipe recognise an end-of-file and finish.

With FreeBSD 2.1-STABLE, the pipe will not recognize the end-of-file,
but instead will wait on "netio" (as shown with ps), and the awk will
wait forever inside the close(). But this will happen only, if there
are multiple such pipes open at the same time.

To reproduce, try the following:

awk 'BEGIN {
	cmnd1 = "cat > " NR;
	cmnd2 = "cat > " NR "a";
}
{
	print NR " " $0 | cmnd1;
	print NR " " $0 | cmnd2;
	close(cmnd1);
	cmnd1 = "cat > " NR;
	close(cmnd2);
	cmnd2 = "cat > " NR "a";
}'

It will write the first input line into filename "0" and into
filename "0a", and then it will hang.

The workaround is to close the second pipe first and the first pipe
second. This is not necessary on other OS' that use Gnu-awk. (But not
to get a wrong imperssion: 2.1-STABLE is more stable than these.)

Peter

-- 
  Write to:  Peter Much * Koelnische Str. 22 * D-34117 Kassel * +49-561-774961
            peter@citylink.dinoex.sub.org  *  much@hrz.uni-kassel.de