Question

I have this datafile

[abc]
def
ghi
[jkl]
[mno]

From this file; i can run grep and easily get all lines that have “[” in them. How can I get the contents of text inside “[]”.

For example:

abc
jkl
mno

Thanks

Answer 1

sed -n 's/\[\(.*\)\]/\1/p' file

Explanation: -n suppresses the printing of each line to STDOUT, but the /p at the end of the regex re-enables this behavior causing all matching lines to be printed. The regex itself matches everything between brackets and replaces the entire line with it.