.* too greedy in sed

Question

I want to extract a version number from some strings in bash without using too much additional packages. So far I tried sed.

Here is the API :

3.81-8.1ubuntu1.1    should give :  3.81
2.68-1ubuntu2        should give :  2.68
1:1.11.3-1ubuntu2    should give :  1.11.3

And here is my sed command so far:

echo ... | sed -r 's/.*([0-9\.]+).*/\1/'

However, the opening .* is too greedy, especially with the last case. I've tried some .*? and .\{-} without any success.

I can do it in two passes, but I would rather learn how to do it in one.

Possible duplicate of http://stackoverflow.com/questions/1103149/non-greedy-regex-matching-in-sed — , Jan 22 '13 at 17:21
@Tinctorius I'd rather not use perl, as stated in my question. But if there is no better way... — Offirmo, Jan 22 '13 at 17:23

score 8 · Accepted Answer · answered Jan 22 '13 at 17:25

8

is this ok for you?

 grep -Po "[\d\.]*(?=-)" file

example:

kent$  cat tt
3.81-8.1ubuntu1.1
2.68-1ubuntu2
1:1.11.3-1ubuntu2

kent$  grep -Po "[\d\.]*(?=-)" tt
3.81
2.68
1.11.3

answered Jan 22 '13 at 17:25

Kent

1

Waow. Didn't know that grep could be used that way. I'm a little afraid of "This is highly experimental and grep -P may warn of unimplemented features." (cf. man grep) but this is a very strong answer ! – Offirmo Jan 22 '13 at 17:28
1

Exactly what I just about to post +1 You don't need to escape the period inside a character class however. – Chris Seymour Jan 22 '13 at 17:28
@sudo_O thx.. I always put a back-slash...seems to be unnecessary . – Kent Jan 22 '13 at 17:35
I'm using this technique again. What is the last part `(?=-)` ? – Offirmo Feb 22 '13 at 23:35
1

@Offirmo means "followed by `-`" – Kent Feb 22 '13 at 23:42

Chris Seymour · Answer 2 · 2013-01-22T17:56:06.043

1

To overcome the greediness you need to be more strict with the regexp:

$ sed -r 's/.*([0-9]+\.[0-9]+\.?[0-9]+)-.*/\1/' file
3.81
2.68
1.11.3

This will match version numbers with major, minor and build (optionally) marks, always followed by a hyphen.

edited Jan 22 '13 at 17:56

answered Jan 22 '13 at 17:50

Chris Seymour

2 Answers2