Re: regular expression behaviour.

[Matthew Woehlke]

cristi wrote:
> By executing the following statement at the command prompt (linux os)
>
> $ echo "         01" | grep '^ *...$'
>
> the string  "         01" (excluding the double quotes)  is printed to
> the standard output.  Can somebody  explain the behaviour? Of  course,
> theoretically the regular expression matches the string, but according
> to the documentation  it shouldn't. The documentation says  that the *
> operator  is greedy  so the  regular expression  should match  all the
> space at the beginnign of the  string and then (because of the 3 dots)
> it should try to match 3 more characters.

I might be wrong, but I think "greedy" means that, for example, "a*b" 
will match all of "aaaaaaaaaaaaaaaaaaaab" rather than just the last two 
characters (e.g. if using --color), not that it will consume all 
possible characters in such a way to prevent a match when only consuming 
some would result in a match. IOW, it's greed that isn't especially 
relevant to grep where what matters is mainly matched vs. didn't match, 
but moreso to things where it matters what part of the string matched 
(e.g. sed, syntax highlighters, etc).

--
Matthew
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