getting a substring from a regular expression

Question

Here is the line of text:

SRC='999'

where 999 can be any three digits.

I need a grep command that will return me the 999. How do I do this?

Answer 1

Here is how to do it using sed

grep SRC=\'.*\' | sed 's/SRC=.\(.*\)./\1/'

Answer 2

You can use the -o option on grep to return only the part of the string that matches the regex:

echo "SRC='999'" | grep -o -E '[0-9]{3}'