Shells make large-scale IT possible. They’re a necessary component to modern computing. But it might not have turned out that way without a lot of hard work from a developer at the Free Software Foundation named Brian Fox. Now, the Bash shell is shipped with almost every computer in the world.

In the ‘70s, Bell Labs wanted to automate sequences of repetitive, complex commands. Chet Ramey describes how Bell developed several shells—but there could be only one officially supported shell for UNIX. Enter the Bourne shell. Though it was the best of that crop, the Bourne shell had its limits. And it was only available with a limited UNIX license. Brian J. Fox recounts his time at the Free Software Foundation where he needed to create a free—as in speech—version of the Bourne shell. It had to be compatible without using any elements of the original source code. That Bourne-Again Shell, aka Bash, is possibly the most widely used software in the planet. And Taz Brown describes how it’s one of the most important tools a developer can learn to use.