Terminal Basics

Posted on Oct 20, 2014

In this guide, I hope to:

  • Give you insight into what the terminal is, and what it can do.
  • Explain the risks and rewards of using the terminal.
  • Encourage you to try it out with some simple tasks.

Note: “Terminal” in this guide refers to the UNIX-like terminal you’ll find in a Mac or Linux Operating System. Although some of the functionality described here can be replicated in the Windows PowerShell, it is a fundamentally different environment. I highly encourage Windows users to check out Cygwin, which is designed to give you a proper UNIX-like environment on Windows.

What is the mystical Terminal?

In short, the Terminal is a window that gives you direct access to your Operating System. Instead of using an application to pass your requests on to the OS, you can tell it what to do with simple commands.

It’s a lot like the difference between going to advising and signing up for classes online. Even though an application on your computer (your advising office) can do everything you need, why wade through all of its policies and restrictions when you can tell the system (myUCF) exactly what you want and have it done immediately?

Of course, this makes the terminal dangerous. Because you are directly telling the OS what to do, there are minimal safeguards; for example: if you delete a file, it’s gone forever. You can seriously mess up your system (trust me, I have). Don’t let that turn you away, though; if you respect the terminal, it can be a very powerful tool.

So, how does it work?

When you type into a terminal, it has a list of places to check for commands that match whatever you type (the $PATH variable, an advanced topic). For example, if you enter “whoami” in your terminal, it checks a few places for an executable file called “whoami”. When it finds /usr/bin/whoami, it runs it, and that executable prints out your username.

By default, you have over a thousand commands you can run, with functionalities ranging from copying files to creating partitions on your hard disk. Let’s take a look at some basic commands for navigating and managing your files.

When you start a new terminal session, your current location or “working directory” is your home folder, such as /home/someuser. You can run pwd to find out where you are, cd to change directories, and ls to list the files in your current location.

Basic Filesystem Navigation in TerminalBasic Filesystem Navigation in Terminal

As you can see, the commands are like small building blocks you can put together to do interesting things. Some commands have arguments associated with them: for example, cd <location> changes directory to the specified location. Commands might have flags as well: for example, ls -l gives you more information about the files in your current directory.

Example Commands with Arguments and FlagsExample Commands with Arguments and Flags

With frequent use, you will memorize most of the basic commands you need to work in the terminal. For other commands, you have Google and Manual Pages at your disposal.

If you run man pwd, you’ll see the manual page for the pwd command. At the top is a short description of what it does. Further down, you can see all of the arguments, flags, and options the command might accept. For pwd, there are only two possible flags that change the behavior depending on how your filesystem is structured. Note: Man pages are displayed in a terminal program called less. You can use the up/down arrows to scroll. To exit, press Q.

Manual Page for the pwd CommandManual Page for the pwd Command

Why should I care?

Sure, there are applications out there to do most anything you need. Many users never touch the terminal, and aren’t any worse off because of it. Here are a few reasons I use the terminal on a regular basis:

  • Some things are much easier in the terminal. Example: any repetitive action (such as renaming many files at once, or according to some rule). Note: OS X Yosemite helps out with this particular example.
  • The terminal can replace entire applications. Example: with prior setup, you can use sudo apachectl start to replace MAMP for running a web server locally on your Mac.
  • You can save money. Example: if you want to compile Sass into CSS, you could pay for CodeKit on the Mac (a fantastic investment, if you can make it), or you can install and use the sass command in terminal.

How do I get started?

If you find yourself needing to do a simple task on your computer, try it out in terminal. For example, if you need to open a PDF on your Mac, try cd-ing to the correct directory and using open <filename> instead of going through Finder. Periodically ask yourself if you can replace an application with a few terminal commands. A lot of times, the answer will be “yes.”

Here are some technical things to keep in mind:

  • Commands and filenames are case sensitive.
  • Things are different across operating systems (very different on Windows).
  • The rm command, for deleting a file, is permanent.
  • There are plenty of resources to help you out!

What’s next?

If you are interested in learning more, check out some of these advanced topics:

Edit (2021-01-24): The Windows Subsystem for Linux is now a much better resource than Cygwin mentioned above.