How to Use the Command 'ghcup' (with Examples)

GHCup is a powerful tool for managing the Haskell programming toolchain on different operating systems. Through GHCup, users can easily install, manage, and update GHC versions, cabal-install, and more. This utility simplifies the process of setting up and maintaining a Haskell development environment, ensuring developers have the right tools and versions to match their project requirements.

Use case 1: Start the Interactive TUI

Code:

ghcup tui

Motivation:

Starting the Text User Interface (TUI) is an excellent choice for users who prefer navigating through options in an interactive, text-based visual interface rather than using command-line arguments. The TUI provides a user-friendly way to manage installations and updates without needing to recall specific commands.

Explanation:

The command ghcup tui does not involve additional arguments. It launches the interactive interface provided by GHCup, allowing users to browse, select, and execute various actions related to their Haskell toolchain.

Example Output:

Running this command will open a TUI that might display a list of available actions, such as managing GHC versions, installing cabal-install, and checking current toolchain status.

Use case 2: List Available GHC/Cabal Versions

Code:

ghcup list

Motivation:

The ability to list available GHC and Cabal versions is crucial for developers when they need to decide on a specific version to install or switch to. This ensures compatibility with particular libraries or projects which may depend on a specific tool version.

Explanation:

The ghcup list command queries the GHCup repository for all available versions of both GHC and Cabal. It provides a comprehensive view of all the tools that a developer can install or update to, directly from their terminal window.

Example Output:

Running this command will typically return a list of versions, each tagged with availability status, like:

GHC:
 * 9.0.1
   8.10.4
   8.8.4

cabal-install:
 * 3.4.0.0
   3.2.0.0

Use case 3: Install the Recommended GHC Version

Code:

ghcup install ghc

Motivation:

Installing the recommended version of the Glasgow Haskell Compiler (GHC) is a wise choice for users who want to ensure they have a stable and well-supported version for general Haskell development. This is particularly useful for beginners who may not know which version to choose.

Explanation:

The command ghcup install ghc installs the version of GHC that is recommended by the GHCup toolchain for most users. This is curated to represent a balance of stability, compatibility, and new features.

Example Output:

This command usually results in a message confirming the installation of GHC, such as:

[ Info ] Unpacking GHC...
[ Info ] GHCup installed GHC 9.0.1

Use case 4: Install a Specific GHC Version

Code:

ghcup install ghc version

Motivation:

Sometimes projects require a specific version of GHC to ensure consistency in development, testing, and deployment. Developers can use this command to install the exact version they require, as opposed to using the latest or recommended version.

Explanation:

In the command ghcup install ghc version, version should be replaced with the desired version number, such as 8.8.4. This instructs GHCup to download and install that particular version for use on the system.

Example Output:

A typical response might look like this after a successful installation:

[ Info ] Installing version 8.8.4
[ Info ] GHCup installed GHC 8.8.4

Use case 5: Set the Currently “Active” GHC Version

Code:

ghcup set ghc version

Motivation:

Switching between different versions of GHC is crucial in environments where multiple projects are maintained, each potentially requiring different compiler features. This command enables developers to easily change the active version of GHC on their system without uninstalling or reinstalling.

Explanation:

Here, ghcup set ghc version takes version as an argument specifying which installed GHC version should be made active. This updates the system path settings so that the specified version is used by default.

Example Output:

Upon execution, the user is informed of the change:

[ Info ] Set GHC 8.8.4 as the active version

Use case 6: Install Cabal-Install

Code:

ghcup install cabal

Motivation:

Cabal is a system for building and packaging Haskell libraries and programs. Installing it via GHCup simplifies the process for developers who need a reliable building tool for their Haskell projects.

Explanation:

ghcup install cabal directs GHCup to install the latest version of Cabal available from its repository, facilitating dependency management and build processes for Haskell projects.

Example Output:

The command results in a confirmation message:

[ Info ] Cabal-Install version 3.4.0.0 installed successfully

Use case 7: Update GHCup Itself

Code:

ghcup upgrade

Motivation:

GHCup is continually improved, with new features, enhancements, and bug fixes. Regularly updating the tool ensures that users have access to the latest optimizations and functionality, which could streamline their development process.

Explanation:

ghcup upgrade fetches the latest version of the GHCup software and installs it, ensuring the user benefits from the latest updates and security fixes.

Example Output:

The process is typically quick, with output similar to:

[ Info ] Upgrading GHCup from version 0.1.0 to 0.1.1
[ Info ] Upgrade complete

Conclusion:

GHCup provides an essential utility for Haskell developers, offering a streamlined interface for managing the entire Haskell toolchain. Through these examples, it is clear how GHCup can enhance productivity and maintain a clean setup by giving the user easy control over installations, versions, and updates.