[ILUG] Re: sed problem

[Dave Neary]

Hi all,

I was reading the Sed question to the list in the archives (sorry, still 
not re-subscribed :) and Padraig's answer, which is no good...

John A. Kinsella wrote:
 > I'd like to do a simple conversion
 > s/Maple 8/Maple 9/g
 > in a bunch of Maple *.mws files using sed.
 >
 > Is there a way to tell sed to do the substitution while preserving the
 > line breaks (which Maple seems to need).

There is, but it's a mess. The problem is that sed's buffer only stores 
lines, usually. You need to use G and H to add the current line to the 
stored pattern buffer, and retrieve it. It's all a big mess...

But here goes a try...

sed -e '
N
s/Maple\([\n ]\{1,\}\)8/Maple\19/g
P
D' testfile

The D is the trick - since there'll be stuff left in the pattern buffer 
every time until the last, it restarts without automatically dumpling 
the pattern buffer, and without reading a new line. We dump and read 
explicitly with P and N respectively. Then when N fails, sed does what 
it always does, prints the pattern space (the last line) and quits.

I thought \19 might cause a problem, but apparrently sed does the right 
thing.

Cheers,
Dave.

-- 
David Neary
Phenix Engineering
110 ave Jean Jaures, 69007 Lyon