Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!rutgers!mcdchg!ddsw1!dattier
From: dattier@ddsw1.MCS.COM (David W. Tamkin)
Newsgroups: comp.editors
Subject: sed output
Summary: two output files without truncation?
Message-ID: <1991Feb20.234921.5738@ddsw1.MCS.COM>
Date: 20 Feb 91 23:49:21 GMT
Organization: Contributor Account at ddsw1, Wheeling, Illinois
Lines: 23

Hmmm...this is knotty to explain...  I'm running sed in a for loop (in sh)
on several input files.  Let's call them A, B, C, D, and E.  The sed script
should send output to three places.  If I made a separate output file for
each one, I'd finish with fifteen output files: Ax, Ay, Az, Bx, etc., through
Ez.  What I really want are a single x file, y file, and z file.

When a sed script begins, sed scans for w operators and creates all target
files needed.  If files by those names already exist, tough; the old contents
are clobbered.  So if I use "w x" and "w y" in the script and redirect sed's
stdout >>z, only z will have the proper contents; x and y will have only the
extractions from input file E.

I can use "w $i.x" and "w $i.y" (with proper quoting for the loop variable to
be expanded) and then cat [A-E].x > x and cat [A-E].y > y afterward, but I'd
rather lengthen the sed script than add the extra forks.  Yes, I'm sure it
can all be done in awk or perl, but I don't know them, don't do this stuff
for a living, and certainly don't have the means or time or talent to learn
awk or perl.

Can sed be prevented from clobbering a file named in a w command?

David Tamkin  Box 7002  Des Plaines IL  60018-7002  708 518 6769  312 693 0591
MCI Mail: 426-1818  GEnie: D.W.TAMKIN  CIS: 73720,1570   dattier@ddsw1.mcs.com