Matching an integer between the brackets

Question

I am given bunch of strings in the following format:

ASDF [         6]

ZXC[1]

OtPasd[ 4 ]

asdffa[   7]

I need to retrieve the integer betwee

Answer 1

use this regex (?m)(?!<=\[)(\[\s*)(\d+)(\s*\])(?!\]) your integer in match group