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From: rupley@arizona.edu (John Rupley)
Newsgroups: comp.unix.questions
Subject: Re: sed script to combine blank lines?
Summary: use sed not awk
Keywords: sed
Message-ID: <7372@megaron.arizona.edu>
Date: 14 Oct 88 00:30:01 GMT
References: <192@vlsi.ll.mit.edu> <136@nascom.UUCP>
Distribution: comp
Organization: U of Arizona CS Dept, Tucson
Lines: 27

In article <136@nascom.UUCP>, rar@nascom.UUCP (Alan Ramacher) writes:
> In article <192@vlsi.ll.mit.edu>, young@vlsi.ll.mit.edu (George Young) writes:
> > Is there a 'sed' wizard out there?  I often want to take a big ascii file
> > (like a .c file after cc -E) and collapse each group of 'blank' lines
> > into exactly one blank line.  'Blank' here is any combination of blanks,
> > tabs and maybe ^L's.
> 
> sed is not powerful enuf for the job, but a simple awk script will
> work. 

The following simple sed script should work (after replacing <sp> etc
by the corresponding ascii characters) -- and I suspect it is shorter and
will run faster than an equivalent awk script.

sed   "/^[<sp><tab><lf>]*$/{
	N
	/\n.*[^<sp><tab><lf>]/{
	b
	}
	D
	}" filename


John Rupley
    internet: rupley@megaron.arizona.edu
    uucp: ..{cmcl2 | hao!ncar!noao}!arizona!rupley
    Dept. Biochemistry, Univ. Arizona, Tucson  AZ  85721