Context of the matching regular expression

Question

I'm using egrep with the -o option in order to just get the matching part of the line, e.g.

cat /usr/share/dict/words | egrep -o '(aa|ii)'

Now I'd like to see some context of the match, i.e. a few characters on the left and on the right. One way to achieve this is by

cat /usr/share/dict/words | egrep -o '.{3}(aa|ii).{2}'

Is there a better (more efficient and elegant) way? (I've gone through the egrep commandline options but didn't find one for this purpose.)

@StéphaneChazelas Thanks, it's the same question, but I'm looking for a better answer. ;) — Kaarel
– Kaarel, Commented Jul 3, 2014 at 19:47
If it is the same question, this kind of clarification might be better if asked in-comments on the original. — HalosGhost
– HalosGhost, Commented Jul 3, 2014 at 19:54
If the Q is a duplicate (it is), the other answers aren't good enough, and you can't find a way to make this a new question, the answer to "Is there a better way?" is No. @HalosGhost Adding a comment to an existing question looking for another answer is unlikely to solicit any response from anyone at all. — goldilocks
– goldilocks, Commented Jul 3, 2014 at 21:37
I'd say they're closely related but not duplicates (I answered both). The other one was looking at limiting the (multi-line) context offered by grep -A/B/C and was asking for color, file names and line numbers. This one is simpler as it only asks for context around a (or several) match within a line. — Stéphane Chazelas
– Stéphane Chazelas, Commented Jul 3, 2014 at 22:17

Stéphane Chazelas · Accepted Answer · 2014-07-03 19:58:14Z

3

You could do something like:

$ echo 'aabiicaa' | perl -lne '
   while (/aa|ii/g) {print substr($`,-3)."[$&]".substr($'\'',0,2)}'
[aa]bi
aab[ii]ca
iic[aa]

answered Jul 3, 2014 at 19:58

584k96 gold badges1.1k silver badges1.7k bronze badges

1 Answer 1