Creating Bash Scripts

Let’s start with the ability to create scripts. With scripts, you can run sequences of commands. They prevent you from repeating yourself and allow you to store long and tedious to type commands for later usage.

A command-line script starts with the shebang --- a sequence of the two characters #!. After these two characters, you can name any interpreter and a bunch of arguments, like this:

#!interpreter [optional arguments]

A shell script is usually based on the most popular shell called Bash, so this would simply become:

#!/bin/bash

Sometimes you’ll see this instead:

#!/usr/bin/env bash

When using /usr/bin/env, the provided command will be searched for in the current $PATH, instead of hardcoding it to the /bin/bash location. Bash will almost always be found at /bin/bash, so the first method is fine for us.

However, you may want to use this trick to create an executable Python script. Python can be installed anywhere, depending on the way it is installed. I’ve seen it in /usr/bin/, /bin, and /usr/local/bin, just to name a few. If you're running a virtual environment, it can be anywhere. So searching the $PATH is a good option, since that will find the Python version from the virtual environment.

We’ll get to creating an actual shell script in a moment. But first, we’ll take a look at variables and for-loops to juice things up a little.


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