How to find common rows in multiple files using awk

Question

I have tab delimited text files in which common rows between them are to be found based on columns 1 and 2 as key columns. Sample files:

file1.txt 

aba 0 0 
aba         


        

Answer 1

Can't you simply use uniq to search for repeated lines in you files?

Something like:

cat file1.txt file2.txt file3.txt | uniq -d

For your complete scenario, you could use uniq -c to get the number of repetition for each line, and filter this with grep.