Break three directories in three different ways

Answer

mkdir alpha beta gamma chmod 600 alpha chmod 500 beta chmod 300 gamma ls -ld alpha beta gamma

The listing reads `drw-------`, `dr-x------` and `d-wx------`. Each is missing exactly one of the three bits, which is what makes the next three commands fail differently.

Sarwar & Koretsky 3e §5.4.3, §5.5.3