extract line if value in first column matches and value in second column not matches in another file in bash

Question

I have 2 different files that look like this

 61435320        rs10000085
 12984967        rs10000091
 32039123        rs10000150

and this:

 61435320        rs12958
 12984967        rs10000091
 32039123        rs37892

I would like to extract only those rows which match the first field but do NOT match the second field.

So, my desired output would look like (I only want the first field):

61435320
32039123

I've tried this answer on Ask Ubuntu but, unfortunately, it is not working for me (I guess it is not exactly what I'm looking for).

Answer 1

Suppose your files are called a and b, you can do it like this:

join a b | awk '{if ($2!=$3){print $1}}'

If your files are not sorted properly, join may have issues. You can sort them like this:

join <(sort a) <(sort b) | awk '{if ($2!=$3){print $1}}'

Answer 2

Only with awk :

awk -v'f=file2' '{if((getline b<f)>0)$0=$0 b}$1==$3 && $2 != $4{print $1}' file1