regex for appending text using sed

Question

I have text that looks like this

HELLO WORLD (some_text, some_other_text)

I want to append a number say 16 at the end to the above text like this

HELLO WORLD (some_text, some_other_text) 16

I know this regex ^HELLO WORLD \(([a-z],[a-z]) matches it . I am not sure how to store the regex matched in a variable and then append 16 to it.

Answer 1

The & character holds everything in the pattern space:

sed 's/^HELLO WORLD ([a-z_]*, [a-z_]*)/& 16/' file

Take a look at Using & as the matched string

And Using \1 to keep part of the pattern