Docker containers were first developed on Linux for Linux. It is thus natural that the primary command-line tool used to work with Docker, also called a shell, is a Unix shell; remember, Linux derives from Unix. Most developers use the Bash shell. On some lightweight Linux distributions, such as Alpine, Bash is not installed and consequently one has to use the simpler Bourne shell, just called sh. Whenever we are working in a Linux environment, such as inside a container or on a Linux VM, we will use either /bin/bash or /bin/sh, depending on their availability.
Although macOS X is not a Linux OS, Linux and OS X are both flavors of Unix and thus support the same types of tools. Among those tools are the shells. So, when working on a Mac, you will probably be using the Bash shell.
In this book, we expect from the readers a familiarity with the most basic scripting commands in Bash, and PowerShell if you are working on Windows. If you are an absolute beginner, then we...