Using awk, how to get desired output from multiple file sources

Question

I have two files:

file1:

A,D
B,E
C,F

file2:

G,H,I
J,K,L

Using awk, I want to print:

A,D
B,E,I
C,F,L

How can I use awk to achieve this?

What is the relation between the 2 files? Is it a one one one comparison?
@Guru, I do not understand what you're asking. File2 looks exactly like the above.
@nowy1 : How will the output be if the file1 has 5 lines in it?
It's unclear from your sample how the files should be merged in the general case.
@Stephane Chazelas, See my edit. I changed the question and its description. You should now be clear.

glenn jackman · Accepted Answer · 2012-12-21 12:35:46Z

up vote 5 down vote accepted

I'll assume that extra field from the n lines of file2 should be appended to the last n lines of file1:

awk -F, -v OFS=, 'FNR==NR {a[FNR]=$3; next} {print $0, a[FNR]}' <(tac file2) <(tac file1) | tac

paste -d, <(tac file1) <(cut -d, -f3- <(tac file2)) | tac

These solution add a trailing comma to the first line. You can remove it by piping the above through sed 's/,$//'

edited Dec 21 '12 at 12:35

answered Dec 21 '12 at 12:30

glenn jackman
5,275514

	See my edit. The files have a different number of lines (file1 -> 3 lines; file2 -> 2 lines). – nowy1 Dec 21 '12 at 12:36
	This is a good solution. Thank you. – nowy1 Dec 21 '12 at 12:41

1 Answer