Loading an external function to a shell script

A problem that will often pop up when you need to create more complex shell scripts is going to be how to include other code into your script. Once you start scripting, you will often create a couple of common functions that you always use—things such as opening connections to servers, getting some operations done, and other things like that.

Sometimes, your scripts will have to use a lot of preset variables that are defined by the user before they even run the script in order to avoid having to type them in each time a script is called.

Of course, the solution to both of these problems can be to simply copy and paste the relevant code into your script and to make the user edit the script before running it. The reason we should never do this is that each time we copy and paste something, we are creating a new version of our code. If we notice an error in the code, we need to fix it in all the scripts that reuse it. Luckily...