Relative and Absolute Paths A relative path is a path that is relative to your cwd. An absolute path is a path that points to an absolute location in the file system.

The Environment Variable $PATH and friends $PATH tells the system where to look when you enter a command.

Comments in BASH A one-line comment is a space then a pound sign(#). Do not forget the space or you will get an ugly surprise. That means: deliberately make that mistake and see what happens.

Aliases

Writing a Shell Script A shell script is just a bunch of UNIX commands in a file. BASH is a turing-complete programming language. Using a .sh extension gives you proper syntax coloring.

The first line should be the shebang line which looks like this.

#!/bin/bash