AWK: Access captured group from line pattern

With gawk, you can use the match function to capture parenthesized groups.

gawk 'match($0, pattern, ary) {print ary[1]}' 

example:

echo "abcdef" | gawk 'match($0, /b(.*)e/, a) {print a[1]}' 

outputs cd.

Note the specific use of gawk which implements the feature in question.

For a portable alternative you can achieve similar results with match() and substr.

example:

echo "abcdef" | awk 'match($0, /b[^e]*/) {print substr($0, RSTART+1, RLENGTH-1)}'

outputs cd.

That was a stroll down memory lane...

I replaced awk by perl a long time ago.

Apparently the AWK regular expression engine does not capture its groups.

you might consider using something like :

perl -n -e'/test(\d+)/ && print $1'

the -n flag causes perl to loop over every line like awk does.