This is Data Science

Command Line Tools (CLT)

Developer Command Line Tools (CLT) are a set of software programs that can be executed by the developers directly on terminal without needing a graphical user interface (GUI). These tools enable essential developer capabilities from the terminal — including python3, git, make, and compiler toolchains.

A fresh macOS installation does not include any Developer-CLT. Apple distributes them as the xcode-select package, which can be downloaded from Apple developer page without installing the full Xcode IDE. Users who already have Xcode IDE installed, will have CLT bundled with it.

Checking Existing State

Before installing anything, let's check what is already present:

% which xcode-select
/usr/bin/xcode-select
 
% xcode-select --version
xcode-select version 2384.

This gives us the impression that xcode-select is already installed — the binary exists, but that does not mean the developer directory is active. When we try to print paths, this happens:

% xcode-select -p
xcode-select: error: unable to get active developer directory
 
% xcode-select -p 1>/dev/null;echo $?
2

A return code of 2 confirms no active developer directory is set. We can also check other tools that depend on CLT:

% which brew
brew not found
 
% which python3
/usr/bin/python3
 
% python3 --version
xcode-select: note: no developer tools were found, requesting install.

Installing CLT

Let's run the installation command:

% xcode-select --install
xcode-select: note: install requested for command line developer tools

A system dialog will appear offering to install the CLT. xcode-select installation dialogue box We need to click Install and wait — the process typically takes 5–30 minutes depending on the connection speed.

Verifying the Installation

A successful installation should return the code 0 instead of 2:

% xcode-select -p
/Library/Developer/CommandLineTools
 
% xcode-select -p 1>/dev/null;echo $?
0
 
% python3 --version
Python 3.8.2

Return code 0 confirms the developer directory is active. python3 now works from the terminal. Homebrew is still absent — we address that in the next chapter.