UNIX for Beginners Questions & Answers

Thanks @bakunin for the detailed explanation regarding join. I also realized that my original question wasn't clear and I didn't really need to compare the files or capture the data in an array. I was able to do a simple "join" after sorting. As I was in a hurry I ended up posting a query that was poorly worded. Anyway just for clarification here is my first file (sorted by the first field):

Code:

ant	Insecta	
cat	mammal
Elephant	mammal	
lizard	reptile

Here is my second file sorted by the first field:

Code:

ant	termite
ant	army_ant
human	man
human	woman

I can join this by the (default) first field as follows:

Code:

join first.txt second.txt


Code:

ant Insecta termite
ant Insecta army_ant

Clearly in my original post, I also erred in my expectation for the “third file” where I erroneously included human man mammal. This was first pointed out by @vgersh99. Thanks!

If you don't want to sort your input files (as required by join), please show us what you tried with awk (so we can see how close you were able to get to your goal). Maybe we can help you fix your awk code to get the output you want.

Don, @vgersh99 gave me a hint in a PM and using that I think, I have got the output I desired using the following awk code:

awk 'FNR==NR{f1[$1]=$2;next} $1 in f1 {print $0,f1[$1]}' first.txt second.txt

Code:

ant	termite Insecta
ant	army_ant Insecta