CPL-on-Macintosh howto

Apple macOS or OS X is a proprietary unix operating system, derived from the old BSD unix, and has all the requirements for CPL tools and programs to run natively on it. However the classical unix programming tools are not part of the base system, but they are offered by Apple as a separate Xcode development environment. In addition CPL needs the gcc compiler, and although Xcode includes a C compiler named gcc, this is an Apple-modified version (also known as clang) and lacks some necessary gcc extensions. Unmodified gcc can be installed through a third-party package manager such as Homebrew. Hence come the following

Step by step instructions to use CPL on Apple macOS

1 - Open a terminal:
Click the terminal icon in your Dock, or if you do not yet have such an icon enter terminal in the search box and click terminal.app.
2 - Install Command Line Tools:

In a terminal execute the following click-to-copy line:

xcode-select --install

A dialog box will pop up asking if you want to install the Command Line Developer Tools. Accept. If the box does not appear, you probably have them already. Alternately you can install the full Xcode development environment from the App Store, but only do so if you want this much larger package for its own purposes.

3 - Install the Homebrew package manager.
Execute the following click-to-copy line, which was copied from the brew.sh website:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
4 - Bring brew up to date (the one just installed sometimes is not):
brew update; brew upgrade
5 - Install the original gcc (the one provided by Apple is an alias for their own clang):
brew install gcc
6 - Download and unpack the CPL archive, with the CC environment variable pointing at the brew-installed C compiler (currently named gcc-13, but do keep an eye for changes):
curl -fsS -o /tmp/unpack-cpl.sh https://CPLcode.net/version-archive/unpack-cpl.sh && env CC=gcc-13 sh /tmp/unpack-cpl.sh
7 - To activate CPL graphics, install package gnuplot. You can do it via Homebrew:
brew install gnuplot

or alternately find contributed macOS binaries on gnuplot's own website.

You are all set! Please notice that you may have to repeat steps 2 and 4 after a macOS system update. Also notice that running a macOS-compiled CPL executable on bare macOS does not need any of the above procedure (except for installing gnuplot if graphics are wanted). You only need to install gcc and the CPL tools when you want to edit, compile or interpret a CPL program, not to just run it.