[SOLVED] awk remove duplicates based on two columns and custom duplication rule

Issue

I want to process a CSV input file like the following :

a;b
b;c
b;a
c;d
x;y
d;c

and remove both duplicate lines defined by the rule : a;b and b;a are considered duplicate and therefore should be removed, the same rule applies to c;d and d;c they shoud be removed.

I tried to process file twice and use the condition NR==FNR to figure which pass it is (first or second) but i can't figure out how to implement the test on the duplication rule i defined above.

please help me

Solution

$ awk -F';' '{ks[$0]; a[$2 FS $1]++} END{for(k in ks) if(!a[k]) print k}' file

x;y
b;c

Answered By - karakfa