UNIX case study - 7

We do often try to do something with a text file that is similar to SQL concept of "inner join" and "left outer join"
It is really easy ...

shell> cat file1
111
222
333
444
shell> cat file2
222
444
666
888
shell> cat file1 file2 | sort | uniq -d
222
444
shell> cat file1 file2 file2 | sort | uniq -u
111
333

More explanation can be found here...
http://tinyurl.com/7wkbaw