How can I use a look after to match either a single or a double quote?

Question

I have a series of strings I want to extract:

hello.this_is(\"bla bla bla\")
some random text
hello.this_is(\'hello hello\')
other stuff

What I

Answer 1

Use a capturing group and look for its content like the following:

grep -Po 'hello\.this_is\(([\047"])((?!\1).|\\.)*\1\)' file

This cares about escaped characters too e.g. hello.this_is("bla b\"la bla")

See live demo here

If the output should be what comes between parentheses then utilize both \K and a positive lookahead:

grep -Po 'hello\.this_is\(([\047"])\K((?!\1).|\\.)*(?=\1\))' file

Outputs:

bla bla bla
hello hello