[SOLVED] sed / grep / awk? : append matching pattern to end of line

Issue

I have a file such as

1,ab012a800,20141205
2,ab023a801,20141205
3,ab012a802,20141205
1,ab024a803,20141205
1,ab012a804,20141205

I want to extract the 'ab012a' part and append that to the end of the line.

1,ab012a800,20141205,ab012a
2,ab023a801,20141205,ab023a
3,ab012a802,20141205,ab012a
1,ab024a803,20141205,ab024a
1,ab012a804,20141205,ab012a

I can extract with grep :

grep -o '^[a-z][a-z][0-9]*[a-z]' file    

and append to a line with sed :

sed "s/$/,whatever/"

or even replace the pattern with sed :

sed '/^[a-z][a-z][0-9]*[a-z]/ s/$/something/' file

but how would I append the matching pattern to the end of the line?

Many thanks

Solution

You can use:

sed -i.bak 's/\(,[a-z][a-z][0-9]*[a-z]\).*$/&\1/' file
1,ab012a800,20141205,ab012a
2,ab023a801,20141205,ab023a
3,ab012a802,20141205,ab012a
1,ab024a803,20141205,ab024a
1,ab012a804,20141205,ab012a

& is special symbol in replacement that represents full matched string by regex used and \1 represents the matched group #1.

Answered By - anubhava