Date: Fri, 20 Nov 1998 10:09:25 +0000 From: Mark Ovens <marko@uk.radan.com> To: Mikhail Teterin <mi@video-collage.com> Cc: questions@FreeBSD.ORG Subject: Re: re_format Message-ID: <36553FD5.29931290@uk.radan.com> References: <199811200112.UAA17886@xxx.video-collage.com>
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Mikhail Teterin wrote:
>
> Hello!
>
> According to the re_format's manpage, the following
>
> echo aXbXccc | sed 's/X.*/X/2'
>
> must result in aXbX -- the second occurence of X.* to be replaced
> by X itself.
>
> Yet, it results in aXbXccc -- no changes. To the best of my
> understanding of re_format, ``X.*'' is a perfectly valid regular
> expression, matching anything that starts with ``X''...
>
r.e.'s using wildcards return the _longest_ unambiguous match, which
in this case is ``XbXccc''. I think that since the (first) match
reaches the end of the string that further matches are not searched
for, therefore the sed substitution fails.
FWIW echo aXbXccc | sed 's/X.*/X/2' gives the same result on SunOS
4.1.3
grep does the same thing. If it found _both_ matches it would return
the line twice.
gppsun4:/users2/radan{4}% cat > scrap
aXbXccc
gppsun4:/users2/radan{5}% grep 'X.*' scrap
aXbXccc
gppsun4:/users2/radan{6}%
> Thanks for any hints.
>
> -mi
>
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--
Trust the computer industry to shorten Year 2000 to Y2K. It
was this thinking that caused the problem in the first place.
Mark Ovens, CNC Applications Engineer, Radan Computational Ltd.
Bath, Avon, England. Sheet Metal CAD/CAM Solutions
mailto:marko@uk.radan.com http://www.radan.com
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