On this page, we'll cover an overview of the CLI. To be completely transparent, most data science tutorials will not start you here. They'll want to jump straight to something like installing Python. So why am I choosing to begin here? Well, it's a bit ironic because you almost assuredly have to interact with the CLI to install Python! When I see many beginner Python courses out there, they make the unfortunate assumption that beginners are already familiar with the CLI and basic CLI commands. I personally found it very frustrating and discouraging as a total beginner.
If you're a complete beginner, you are in the right place! We'll put you on a path to success by keeping things in very simple, non-techie speak. Plus, we'll include lots of pretty pictures! 😁 Again, just be aware that I'm not perfect at keeping this guide updated, so if you do get lost, lean on your AI friends like ChatGPT, Claude, or Perplexity!
The command line interface, or CLI, is the one of the primary ways in which a software developer interacts with a computer. Most programs you are familiar with run as Graphical User Interfaces, or GUIs. (Pronounced "gooey".) As great as GUIs are, they are very subjective from program to program. For example, can you remember how to access the settings for Facebook or Twitter on your phone? Chances are they're in different places! The CLI keeps things a lot more basic, which is helpful for developers as allows for complex functionality to be run in a more simplified, text-based interface.
Mac and Windows each have their own respective CLIs, and for data science work, we're going to focus more on the Mac flavor of this. It's actually not Mac but Linux as the macOS is built on top of Linux. We could spend all day talking about Linux, but simply but Linux is an open source operating system that many engineers like to use because it's reliable, highly configurable, and of course, free.
(Note: We're getting a little bit ahead of ourselves here, because we're going to need to do the installation of the CLI stuff before we can necessarily start playing around with these commands! The problem is that the installation guide can be a bit lengthy that I didn't want this section to bet buried.)
Linux comes with a lot of common commands that are used on a regular basis. Udacity has an excellent free course that teaches these commands well, and I would highly advise you check that out. Here is a link to that course: Udacity - Linux Command Line Basics.
As a quick reference, here are some of the commands I use on a regular basis:
- cd: Standing for "change directory", this command helps you to traverse your computer's directory (or folder) system.
- pwd: Standing for "print working directory", this command will tell you which directory your CLI currently is in.
- ls: This command displays all files and subdirectories listed in the current directory you are working in.
- mkdir: Standing for "make directory", this command will create a new directory under the directory you are currently in.
- touch: Similar to the
mkdircommand,touchwill create a new file under the directory you are working in. - rm: Standing for "remove", this command will remove a file. Be careful when using this command!!
- cp and mv: Standing for "copy" and "move", these commands work similarly to move files or directories around. As the names imply, one is simply moving files from one place to another, whereas the the
cpcommand performs a copy without moving the original file. - cat: This command displays the contents of a file.
As noted before, the Mac CLI already uses Linux commands, so you can actually begin immediately using the default Terminal application that comes bundled with every Mac. Technically, Terminal is ready to go right out of the box. You're welcome to begin using Terminal immediately. But... most developers don't like using Terminal immediately like that. Instead, many developers (including myself) prefer to use a different CLI program called iTerm2. If you're okay with just using Terminal, that is totally fine, but if you'd like to learn more about iTerm2, see further on ahead. (Note: I actually advise pure beginners to stick just within the baseline Terminal application.)
When opening Terminal or iTerm2, you may be prompted to install the XCode developer tools in order to get things working. The XCode developer tools are a suite of software tools that Apple doesn't preinstall on a Mac but supplies for free if you choose to do development on your computer
If the prompt doesn't show up for you, you'll instead want to type in the following command and then press the return key:
xcode-select --install
What this is doing is downloading some core things that your Mac needs to run code. This will also conveniently install Git, which we'll cover in another section.
While there is nothing wrong with using the default Terminal application, I personally prefer to use iTerm2. If you would like to install iTerm2, navigate to this website and follow the download instructions: Link to iTerm2 website.
There is more customizability we can do to iTerm2, but for now we're going to keep things basic. I might come back and update this Markdown at a later time with those customizability features!
By default, Apple implements a version of the CLI called Z shell, or zsh for short. When you open Terminal / iTerm2, it first runs a series of commands to basically set ourselves up for success as we continue along. Within the .zshrc file, we can do things like:
- Create custom aliases that serve as shorthand to do whatever we want
- Set various environment variables
- Enable a custom look and feel
Around that last point, let's set up a custom look and feel program known as Oh My Zsh.
Oh My Zsh is a popular means to make iTerm2 have a bit of extra pizazz and functionality. In order to install Oh My Zsh, simply run the following command:
sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"
After we run this, you should notice some instant changes to the user interface. Remember the .zshrc? It should now be updated with a ton of configuration about Oh My Zsh. Here is what it looks like for me:
# If you come from bash you might have to change your $PATH.
# export PATH=$HOME/bin:/usr/local/bin:$PATH
# Path to your oh-my-zsh installation.
export ZSH="$HOME/.oh-my-zsh"
# Set name of the theme to load --- if set to "random", it will
# load a random theme each time oh-my-zsh is loaded, in which case,
# to know which specific one was loaded, run: echo $RANDOM_THEME
# See https://github.com/ohmyzsh/ohmyzsh/wiki/Themes
ZSH_THEME="robbyrussell"
# Set list of themes to pick from when loading at random
# Setting this variable when ZSH_THEME=random will cause zsh to load
# a theme from this variable instead of looking in $ZSH/themes/
# If set to an empty array, this variable will have no effect.
# ZSH_THEME_RANDOM_CANDIDATES=( "robbyrussell" "agnoster" )
# Uncomment the following line to use case-sensitive completion.
# CASE_SENSITIVE="true"pytp
# Uncomment the following line to use hyphen-insensitive completion.
# Case-sensitive completion must be off. _ and - will be interchangeable.
# HYPHEN_INSENSITIVE="true"
# Uncomment one of the following lines to change the auto-update behavior
# zstyle ':omz:update' mode disabled # disable automatic updates
# zstyle ':omz:update' mode auto # update automatically without asking
# zstyle ':omz:update' mode reminder # just remind me to update when it's time
# Uncomment the following line to change how often to auto-update (in days).
# zstyle ':omz:update' frequency 13
# Uncomment the following line if pasting URLs and other text is messed up.
# DISABLE_MAGIC_FUNCTIONS="true"
# Uncomment the following line to disable colors in ls.
# DISABLE_LS_COLORS="true"
# Uncomment the following line to disable auto-setting terminal title.
# DISABLE_AUTO_TITLE="true"
# Uncomment the following line to enable command auto-correction.
# ENABLE_CORRECTION="true"
# Uncomment the following line to display red dots whilst waiting for completion.
# You can also set it to another string to have that shown instead of the default red dots.
# e.g. COMPLETION_WAITING_DOTS="%F{yellow}waiting...%f"
# Caution: this setting can cause issues with multiline prompts in zsh < 5.7.1 (see #5765)
# COMPLETION_WAITING_DOTS="true"
# Uncomment the following line if you want to disable marking untracked files
# under VCS as dirty. This makes repository status check for large repositories
# much, much faster.
# DISABLE_UNTRACKED_FILES_DIRTY="true"
# Uncomment the following line if you want to change the command execution time
# stamp shown in the history command output.
# You can set one of the optional three formats:
# "mm/dd/yyyy"|"dd.mm.yyyy"|"yyyy-mm-dd"
# or set a custom format using the strftime function format specifications,
# see 'man strftime' for details.
# HIST_STAMPS="mm/dd/yyyy"
# Would you like to use another custom folder than $ZSH/custom?
# ZSH_CUSTOM=/path/to/new-custom-folder
# Which plugins would you like to load?
# Standard plugins can be found in $ZSH/plugins/
# Custom plugins may be added to $ZSH_CUSTOM/plugins/
# Example format: plugins=(rails git textmate ruby lighthouse)
# Add wisely, as too many plugins slow down shell startup.
plugins=(git)
source $ZSH/oh-my-zsh.sh
# User configuration
# export MANPATH="/usr/local/man:$MANPATH"
# You may need to manually set your language environment
# export LANG=en_US.UTF-8
# Preferred editor for local and remote sessions
# if [[ -n $SSH_CONNECTION ]]; then
# export EDITOR='vim'
# else
# export EDITOR='mvim'
# fi
# Compilation flags
# export ARCHFLAGS="-arch x86_64"
# Set personal aliases, overriding those provided by oh-my-zsh libs,
# plugins, and themes. Aliases can be placed here, though oh-my-zsh
# users are encouraged to define aliases within the ZSH_CUSTOM folder.
# For a full list of active aliases, run `alias`.
#
# Example aliases
# alias zshconfig="mate ~/.zshrc"
# alias ohmyzsh="mate ~/.oh-my-zsh"
Notice that a lot of this begins with a hash (#) sign. In the coding world, the # often indicates the start of a human comment, but the code is not actually functional. Developers often "comment out" code when they don't want a piece of code to run but don't want to delete it just in case. You'll notice that in this sample that Oh My Zsh creates, much of this is commented out. If you want to simplify this down, you can do what I did and include only the following bits of information:
export ZSH="$HOME/.oh-my-zsh"
ZSH_THEME="steeef"
plugins=(git)
source $ZSH/oh-my-zsh.sh
Much simpler! One thing to note: you'll notice my ZSH_THEME is set to "steeef". This is just a personal preference. If you want to see a full list of all the themes you can select from, check out this website.
While macOS is built on top of Linux and therefore uses Linux commands right out of the box, this is not the case with Windows. By default, Windows instead makes use of its own CLI called the Command Prompt. Because the Command Prompt uses radically different commands from standard Linux commands, we will NOT be making use of the Command Prompt at all.
In an effort to remedy this, Microsoft has started bundling a program called Windows Terminal (with another program called PowerShell as a profile) with newer versions of Windows. Windows Terminal and PowerShell have been designed to emulate those same Linux commands we see across macOS and other Linux machines. If these are not already installed on your computer, you can install these directly from the Microsoft Store. Here are the appropriate links for those:
To actually make use of Windows Terminal with the PowerShell profile, open Windows Terminal and navigate to the settings. (The screenshot below illustrates where this is, if you can't find it!) Under the "Default profile" dropdown menu, select "PowerShell" (NOT to be confused with Windows PowerShell, which is something different). Then click the "Save" button the bottom right hand corner of the UI.
Technically, this is all you need to do to get Windows Terminal working, but there are some cool things we can do with Windows Terminal / PowerShell that aren't available right out of the box. If you'd like to enable these advanced features, check out the next subsection!
While the Windows Terminal certainly works just fine as we installed it above, most developers (including myself) appreciate extra levels of customization that help navigating the CLI a lot easier. When we're done with this customization, this is what your Windows Terminal might look like:
To enable this, we will be using something called Oh My Posh, "Posh" being short for PowerShell. In the Mac world, there is a very popular CLI customization tool called Oh My Zsh, so Oh My Posh is basically Window's version of that. To get this working, we'll need to follow the following high level steps:
- Installing the Meslo Font
- Creating the PowerShell Profile
- Installing Oh My Posh
- Setting the Oh My Posh theme
- Adding an alias for quick navigation
Let's cover each of these steps more in depth below.
Because Oh My Posh uses special characters not found in the default fonts that come pre-bundled with Windows. The creators of Oh My Posh recommend using this font called Meslo. To download Meslo, simply click this link: Download Meslo here. This will download a ZIP file with a bunch of variants of Meslo font. Technically, we only need one of these variants: Meslo LGM NF. To install, double-click on this variant, which will open a window that looks like this:
Notice in the top left of this window, there is an "Install" button. Click that, and your font will be installed! (Note: You're welcome to install as many variants of this Menlo font as you'd like, but be aware, there's 96 of them, so you'd have to do this 96 times.)
To update the default font of Windows Terminal, navigate to the "Settings" again. This time, click on "Open JSON File" as indicated in the screenshot below.
What this will do is open up the default Windows Notepad to edit some basic settings in text form with this organization style called JSON. Don't worry if you don't know what JSON is, the only thing you'll need to do is scroll down to a section called "profiles", and under the "defaults" section, you will need to add the information found in the screenshot below. Please note that syntax and spacing is important here!!
Save this (hotkey: CTRL+S) and exit Notepad. When you close out of Windows Terminal and re-open it, your default font will now be Menlo!
The first thing we will need to do is to create a PowerShell profile. The PowerShell profile is basically a little script that runs when a new window is opened with PowerShell running. In other words, when we open up Windows Terminal (with the default PowerShell running, as we setup in the previous section), the PowerShell profile will do all the stuff to make Windows Terminal look all nice and pretty!
First off, let's do a quick check to see if you have a profile already created. In order to do that, run the following command:
Test-Path -Path $PROFILE
If this comes back as "False," this means a PowerShell profile does not exist for you yet, which is expected if this is your first time setting up your Windows machine! In order to create your PowerShell profile, run the following command:
New-Item -ItemType File -Path $PROFILE -Force
On executing this command, you should see something like the screenshot below.
That's it for creating the PowerShell profile! Let's move on to populating with what we need for Oh My Posh.
In order to install Oh My Posh directly from your Windows Terminal, all you have to do is run the following command:
winget install JanDeDobbeleer.OhMyPosh
What this did was install the executable file in order to actually get Oh My Posh working as well as download a bunch of different themes to select from. And that's pretty much it for this step! In the next step, you'll see how we can actually set the theme to "prettify" our Windows Terminal!
Okay, as I mentioned in the last step, Oh My Posh downloaded a bunch of themes we can select from. If you'd like to preview all the themes, check out the official Oh My Posh website at this link.
Once you find one you like, we then need to edit our PowerShell profile to set the theme appropriately. Now, if you're curious where Oh My Posh downloaded all the themes, you can find them in this filepath (note that your username will be specific to you):
C:\Users\<YOUR_USERNAME>\AppData\Local\Programs\oh-my-posh\themes
I personally like the simple Amro theme the best, so that's what I'm going to select. In order to edit your PowerShell profile to add your theme, you will need to run this command:
notepad $PROFILE
This will open up Notepad on your computer, and all you need to do is to paste in your selected theme here. Here's what I pasted in mine (again keeping in mind that your username will be different):
oh-my-posh --init --shell pwsh --config C:\Users\david\AppData\Local\Programs\oh-my-posh\themes\amro.omp.json | Invoke-Expression
Just to ensure you're on the right track, here's a screenshot of what this should look like for you.
Once you've added your theme to your PowerShell profile in Notepad here, be sure to save and then close out. Now when you restart your Windows Terminal, you should have your prettified Oh My Posh theme working! Now, if you want, you can be done here, but I would encourage you to check out the last step anyway...
As you'll discover when learning the Linux commands, navigating around your files is easy but can be a little bit cumbersome. For example, it would be annoying to constantly have to type the cd command to navigate to where my Git repositories reside.
Fortunately, PowerShell supports a concept called aliasing. What this basically means is that you can define your own special command that serves as a shortcut proxy in place of doing something like all those cd commands.
So in this specific example, I like to keep my Git repositories at the following path:
C:\Users\david\Documents\Repositories
Instead of typing the Linux cd command over and over to navigate to that, I can instead create an alias for that. Creating an alias is fortunately very simple. Just like we added our theme to our PowerShell profile from the previous step, we can also add an alias as the following:
function repos { set-location "C:\Users\david\Documents\Repositories" }
Here's what that looks like as a screenshot:
Save and close out of Notepad here to apply the changes. Now when I open a new Windows Terminal and type the word repos, it will automatically jump to that directory with my Git repositories!