grep - regex - brackets and parenthesis in character-class

Question

I would like to match these characters: [ ] ( ) in a character class in a regex, how can I do that?

echo 'some text (some text in parenthesis) [some other in brackets]' | grep '[[]()]'

This one doesn't match any character.

Answer 1

You can use it like this:

echo 'some text (some text in paranthesis) [some other in brackets]' | grep -o '[][()]'

(
)
[
]

You don't need to escape ( and ) inside a character class. Moreover if you place ] and [ right after opening [ then you don't need to escape them either.