8.3.6 Union, Intersection and Difference of files

Combine sort, uniq and join to perform the equivalent of set operations on files:

Command outcome
sort -u file1 file2 Union of unsorted files
uniq -d Intersection of unsorted files
uniq -u Difference of unsorted files
uniq -u Symmetric Difference of unsorted files
join -t -a1 -a2 file1 file2 Union of sorted files
join -t file1 file2 Intersection of sorted files
join -t -v2 file1 file2 Difference of sorted files
join -t -v1 -v2 file1 file2 Symmetric Difference of sorted files

All examples above operate on entire lines and not on specific fields: sort without -k and join -t both consider entire lines as the key.