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From: dattier@ddsw1.MCS.COM (David W. Tamkin)
Newsgroups: comp.editors
Subject: Re: ex search & substitution question
Message-ID: <1990Aug08.200822.13213@ddsw1.MCS.COM>
Date: 8 Aug 90 20:08:22 GMT
References: <3440001@hprnd.HP.COM> <26814@nigel.ee.udel.edu> <1990Aug07.174235.28911@hoss.unl.edu>
Reply-To: dattier@ddsw1.MCS.COM (David W. Tamkin)
Organization: Contributor Account at ddsw1, Wheeling, Illinois
Lines: 39

Sanjiv K. Bhatia wrote in <1990Aug07.174235.28911@hoss.unl.edu>, answering
Darren New's response to Brent McInnis:

DN> Try 
DN> :10,20g/^#[iut]55/s/55/71/

DN> I think you can give a range to the g command to have it operate on the 
DN> lines within the range that also match the pattern.       -- Darren

Yes, you can give a firstline,lastline range and then a g or v within it, but
you cannot nest a g or a v within a[nother] g or v.

SKB> Here is my $0.02 worth.  I prefer to use the substitute command 's'.
SKB> :10,20s/^#[iut]55/77/

Not quite, Sanjiv.  That will lose the # and the letter, replacing all four
characters with just "77".

Darren's suggestion of :10,20 g/^#[iut]55/s/55/71/ will work *for this
situation*.  It says to look for #[iut]55 at the beginning of any of those
eleven lines in the numeric range and change the leftmost 55 to 71 in every
line containing that pattern.  It depends, however, on the expression's being
anchored to the left end of the line, or there would be a risk of changing the
wrong 55 to 71 if 55 occurs again farther leftward in the line.  It also
depends on the first part of the search expression's not containing the last
part: if Brent had wanted to change /^5555/ to 5571, he'd get 7155!

:10,20 s/^\(#[itu]\)55/\171/ gets around that problem; it says to look for
the four-character pattern and change the 55 in its last two characters to
71, leaving the first two characters unaltered, regardless of what they were.
Its reasoning can be applied to search patterns that are not left-edge
anchored.  I like the logic behind this method better, but in this particular
case the risks in Darren's advice are not present, and I find his way less
subject than my own to the particular typing errors I'm prone to make.
(Neither method requires a space after the 20; it's just another personal
preference of mine, as was alphabetizing [itu].)

David Tamkin  Box 7002  Des Plaines IL  60018-7002  708 518 6769  312 693 0591
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