Curly braces in regular expressions, sed

[Johnny Rosenberg]

2015-01-06 21:25 GMT+01:00 Nathan Dorfman <na at rtfm.net>:

> On Tue, Jan 6, 2015 at 2:49 PM, Johnny Rosenberg <gurus.knugum at gmail.com>
> wrote:
> > So I use the following command:
> > sed -r 's/.*([0-9]{1,2}:[0-9]{2},[0-9]{2}).*/\1/' x
> > [...]
> > Why is one digit missing in the third line?
>
> Simple: because the '*' operator that comes right before it is
> "greedy," meaning it will match as much as possible, including the
> first digit if it exists.
>

I actually thought of that greedyness, but I reversed my thought: Since
it's greedy it should match ”10” rather than ”0” since matching ”10” is
greedier than matching ”0”… I never thought of the ”.*” part of the pattern…

But yes, I see it now, thanks!


>
> If you include the first | character in your pattern, it should work
> for the example you posted. Like this: sed -r
> 's/.*\|([0-9]{1,2}:[0-9]{2},[0-9]{2}).*/\1/' x
>
>
Yes, that works. I was actually going to try the following, but for some
reason I didn't, I think I forgot about it…:
sed -r 's/[^0-9]*([0-9]{1,2}:[0-9]{2},[0-9]{2}).*/\1/' x

That is, look for anything that is NOT a number followed by that number
pattern. I tried that now and it works too.


Thanks!


Kind regards

Johnny Rosenberg
ジョニー・ローゼンバーグ




> -nd.
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