We started this chapter off by creating and running our very first shell script. As is almost mandatory when learning a new software language, we printed Hello World! onto our Terminal. Continuing, we explained the shebang: the first line of a script, it is an instruction to the Linux system about the interpreter it should use when running the script. For a Bash script, the convention is to have the file name end in .sh, with a shebang of #!/bin/bash.

We explained that there are multiple ways in which we can run a script. We can start with the interpreter and pass the script name as the argument (for example: bash hello-world.sh). In this case, the shebang is not needed because we're specifying the interpreter on the command line. However, normally, we run the file by setting the executable permission and calling it directly; in this case, the shebang is used to determine which interpreter to use. Because you cannot be sure about how a user will run your script, including a shebang should be considered mandatory.

To increase the quality of our scripts, we described how to increase the readability of our shell scripts. We explained how and when to use comments in our scripts, and how we can use comments to create a script header that we can easily view by using the head command. The tail command, which is closely related to head, was briefly introduced. Besides comments, we also explained the concept of verbosity.

Verbosity can be found in multiple levels: verbosity in comments, verbosity in commands, and verbosity in command output. We argued that using long options for commands in scripts is almost always a better idea than shorthand, as it increases readability and can prevent the need for extra comments, even though we established that too many comments are almost always better than no comments.

We ended the chapter with a short description of the KISS principle, which we linked to some design principles in Python. The reader should realize that, if there is a simple solution to a problem, it will most often be the best one. If a simple solution isn't an option, a complex solution should be preferred over a complicated one.

The following commands were introduced in this chapter: head, tail, and wget.