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Date: Tue, 26 Sep 2006 12:48:24 +0100
From: "Richard Quadling" <rquadling AT googlemail DOT com>
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To: cygwin AT cygwin DOT com
Subject: Re: grep weirdness - matching space character
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On 26/09/06, Dave Korn <dave DOT korn AT artimi DOT com> wrote:
> On 26 September 2006 11:17, The Blog User wrote:
>
> > I am really struggling to understand what I am doing wrong here.
> >
> > I have a log file with a line that looks like this:
> >
> > ++ 04:51:32 All 94 items succeeded
> >
> > The binary data for that line is this:
> >
> > 2B 2B 20 30 34 3A 35 31 3A 33 32 20 41 6C 6C 20 39 34 20 69 74 65 6D 73 20
> > 73 75 63 63 65 65 64 65 64 0A
> >
> > using grep and tail (versions below) I am failing to match that line
> >
> > $ tail -1 /path/to/file/the.log | grep -a "All \d*.items succeeded"
>
>   There's no such thing as \d.
>
> > however if I insert 3 (why three?) dots (or a .*) between 'All' and '\d' I
> > get a match, what is happening ?
>
>   The dots are eating the '94' as well as the space.
>
> > This seems wrong to me, since - from my knowledge of regex's - that is
> > saying there must be three characters between the 'All' and the first
> > digit, yet I can see there is only a single space character.
>
>   Escaping a d just matches a literal 'd'.  So the expression '\d*' matches
> zero or more of the letter d.  If you use the three dots to eat the two digits
> as well as the space, the optional any-number-of-d's is matched by the zero
> d's following, and then the trailing 'items succeeded' matches.
>
>   Whereas with only the one dot, the dot matches the space, then there's
> zero-optional-'d's, then the '9' fails to match against '.items succeeded'.

$ cat c:\log.log
++ 04:51:32 All 90 items succeeded
++ 04:51:32 All 91 items succeeded
++ 04:51:32 All 92 items succeeded
++ 04:51:32 All 93 items succeeded
++ 04:51:32 All 94 items succeeded

$ tail -1 c:\log.log
++ 04:51:32 All 94 items succeeded

$ tail -1 c:\log.log | grep -a "All [0-9]* items succeeded"
++ 04:51:32 All 94 items succeeded


Is that what you wanted?

-- 
-----
Richard Quadling
Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&amp;r=213474731
"Standing on the shoulders of some very clever giants!"

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