¹ As the Software Carpentry Unix Shell lesson describes: ‘The most popular Unix shell is Bash, the Bourne Again SHell (so-called because it’s derived from a shell written by Stephen Bourne). Bash is the default shell on most modern implementations of Unix and in most packages that provide Unix-like tools for Windows’ (Devenyi, Koch, & Srinath, 2016). Popular examples of ‘modern implementations of Unix’ are Mac OS X and Linux operating systems such as Ubuntu.