Learn Bash Commands

Overview

The command line lets you communicate with your computer without using your mouse. It’s a text-based interface where you communicate using text alone. The commands differ between Unix-based systems (e.g., Mac / Linux) and Windows computers. On Apple and Windows computers the command line tool is called the Terminal and Command Prompt, respectively.

With this building block, we will help you navigate the command line (Terminal and Command Prompt) and describe the various commands that are used to do so.

But before we start, it is important to be familiar with two important terms: Directories and file paths.

Directories

In programming, all folders are called directories and a directory within another directory is called a subdirectory. A working directory is the directory in which the user is working currently. The default working directory when the user logs in is known as the home directory. So when you open up a new Terminal window, you are automatically situated in your home directory.

File Paths

Your computer understands two kinds of paths, absolute and relative ones. An absolute path starts from the root (or home directory). A relative path, on the other hand, starts from the current directory (for instance, your desktop).

		
absolute_path = "/Users/Pieter/Desktop/images/photo1.jpg"

relative_path = "images/photo1.jpg"  # provided that your working directory is "Desktop"

How to open the Command Line?

Mac
Open the Terminal by going into your Applications folder, and then into your Utilities folder, and then double-clicking on the Terminal icon. Alternatively, you can use Spotlight to search for the program (e.g. Cmd + Space).

Windows
Type cmd into the search bar and hit enter, it should launch the Windows Command Prompt.

Commands

Print Working Directory

Mac
To see the full path for your working directory, you can use the pwd command, which stands for print working directory.

terminal_pwd

Windows
If you type pwd in the Windows Command prompt, it doesn’t recognize the command. Instead, type cd (or chdir) to view the current working directory.

List Files

Mac
Unlike the graphical user interface, you cannot see what other directories or files are present just by being in a particular directory. You have to explicitly tell your computer to list them for you using the ls command.

terminal_ls

If you’d like to explore another directory, you need to use ls with a path. For example, ls ~/Documents will show you what’s inside Documents.

Windows
The dir command lists all files and folders in the current directory. In addition, it returns the file size, file type, and the date and time the file was last updated.

Tip

Press the up and down arrows on your keyboard to cycle through previously used commands in the terminal. Also, you can press TAB for auto-complete suggestions.

Change Directories

Mac & Windows
The command cd allows you to change directories; it’s the equivalent of double-clicking on a folder. For example, if you want to move from the samspade directory into its subdirectory Documents, you would write cd Documents. To move back up to your home directory, you can use the cd .. command.

Note that the path in front of $ indicates your working directory. This helps you keep track of where you’re at.

terminal_cd

Tip

A handy shortcut to start in a specific directory immediately is to look up the folder in Finder, right-click on it, and choose “New Terminal at Folder”.

Create Folder

Mac & Windows
To make a new directory, you can use the mkdir command which takes the name of the new directory and the destination path of the directory. So, the command mkdir to-do-lists Documents would create a new to-do lists directory inside the documents folder.

Tip

Generally speaking, it’s better to avoid special characters in directory names, you can use quotes to create a folder name that includes spaces (e.g., mkdir "to do lists" Documents).

Remove Files & Directories

Mac
You can delete a directory along with any files or subdirectories by running the rm -r command. For example, rm -r to-do-lists removes the to-do lists folder and its contents. Note that you can list multiple files and directories after rm -r to remove them all.

Windows
Separate files can be removed with the del command (e.g., del to-do-list.txt). To remove a directory, use the command rmdir.

Warning

You can’t undo the rm and del commands, so be careful when you delete files. Removing files in command line is not the same as moving a file to the trash - it’s permanent!

Move & Rename Files

Mac
The mv command has two applications: moving and renaming files. It uses the following syntax:

		
# move directories or files to a new location
mv [FILE_NAME] [LOCATION]

# rename files
mv [FILE_NAME] [NEW_FILE_NAME]

Examples:

mv monday_tasks.txt To_Do_Lists moves the text file from its current directory to the ‘to-do list’ folder.
mv 'Monday Tasks.txt' monday_tasks.txt renames the file by stripping the spaces.

Windows
The syntax to move and rename files is exactly the same as on Mac, but instead of mv you need to use the commands move and rename respectively. Note that you cannot use move to rename files on Windows!