A while ago I wrote about how I solved the Google Treasure Hunt Puzzle #4 about prime numbers. I took an unusual approach and solved this problem entirely from the Unix shell. The solution involved finding the intersection between a bunch of files containing numbers. This lead me to an idea to write a post about how to do various set operations from the shell by using common utilities such as sort
![Set Operations in the Unix Shell](https://cdn-ak-scissors.b.st-hatena.com/image/square/deedb67dac356f5b6b3e505320e371d9688b51b1/height=288;version=1;width=512/https%3A%2F%2Fcatonmat.net%2Fimages%2Fcatonmat-preview-image.png)