key1
key3
key4
key6
...

##</code><code>##

key2
key3
key4
key5
...

##</code><code>##

cmpcol -i file1 file2

##</code><code>##

cmpcol -u file1 file2

##</code><code>##

cmpcol -x1 file1 file2  # what's uniq to file1
cmpcol -x2 file1 file2  # what's uniq to file2
cmpcol -x  file1 file2  # all uniq items, tagged by source -- i.e.:
key1 <1
key2 <2
key5 <2
key6 <1