Effective Computation in Physics

Chapter 1. Introduction to the Command Line

The command line, or shell, provides a powerful, transparent interface between the user and the internals of a computer. At least on a Linux or Unix computer, the command line provides total access to the files and processes defining the state of the computer—including the files and processes of the operating system.

Also, many numerical tools for physics can only be installed and run through this interface. So, while this transparent interface could inspire the curiosity of a physicist all on its own, it is much more likely that you picked up this book because there is something you need to accomplish that only the command line will be capable of. While the command line may conjure images of The Matrix, do not let it intimidate you. Let’s take the red pill.

Navigating the Shell

You can access the shell by opening a terminal emulator (“terminal” for short) on a Linux or Unix computer. On a Windows computer, the Git Bash program is equivalent. Launching the terminal opens an interactive shell program, which is where you will run your executable programs. The shell provides an interface, called the command-line interface, that can be used to run commands and navigate through the filesystem(s) to which your computer is connected. This command line is also sometimes called the prompt, and in this book it will be denoted with a dollar sign ($) that points to where your cursor is ready to enter input. It should look something like Figure 1-1 ...