ghcup-hs/README.md

ghcup makes it easy to install specific versions of ghc on GNU/Linux, macOS (aka Darwin) and FreeBSD and can also bootstrap a fresh Haskell developer environment from scratch. It follows the unix UNIX philosophy of do one thing and do it well.

Similar in scope to rustup, pyenv and jenv.

Ubuntu users may prefer hvr's ppa.

Table of Contents

• Installation
• Usage
  • Manpages
  • Shell-completion
  • Cross support
• Design goals
• How
• Known users
• Known problems
• FAQ

Installation

Simple bootstrap

Follow the instructions at https://www.haskell.org/ghcup/

Manual install

Download the binary for your platform at https://downloads.haskell.org/~ghcup/ and place it into your PATH anywhere.

Then adjust your PATH in ~/.bashrc (or similar, depending on your shell) like so:

export PATH="$HOME/.cabal/bin:$HOME/.ghcup/bin:$PATH"

Usage

See ghcup --help.

Common use cases are:

# list available ghc/cabal versions
ghcup list

# install the recommended GHC version
ghcup install ghc

# install a specific GHC version
ghcup install ghc 8.2.2

# set the currently "active" GHC version
ghcup set ghc 8.4.4

# install cabal-install
ghcup install cabal

# update ghcup itself
ghcup upgrade

Generally this is meant to be used with cabal-install, which handles your haskell packages and can demand that a specific version of ghc is available, which ghcup can do.

Manpages

For man pages to work you need man-db as your man provider, then issue man ghc. Manpages only work for the currently set ghc. MANPATH may be required to be unset.

Shell-completion

Shell completions are in shell-completions.

For bash: install shell-completions/bash as e.g. /etc/bash_completion.d/ghcup (depending on distro) and make sure your bashrc sources the startup script (/usr/share/bash-completion/bash_completion on some distros).

Cross support

ghcup can compile and install a cross GHC for any target. However, this requires that the build host has a complete cross toolchain and various libraries installed for the target platform.

Consult the GHC documentation on the prerequisites. For distributions with non-standard locations of cross toolchain and libraries, this may need some tweaking of build.mk or configure args. See ghcup compile ghc --help for further information.

Design goals

1. simplicity
2. non-interactive
3. portable (eh)
4. do one thing and do it well (UNIX philosophy)

Non-goals

1. invoking sudo, apt-get or any package manager
2. handling system packages
3. handling cabal projects
4. being a stack alternative

How

Installs a specified GHC version into ~/.ghcup/ghc/<ver>, and places ghc-<ver> symlinks in ~/.ghcup/bin/.

Optionally, an unversioned ghc link can point to a default version of your choice.

This uses precompiled GHC binaries that have been compiled on fedora/debian by upstream GHC.

Alternatively, you can also tell it to compile from source (note that this might fail due to missing requirements).

In addition this script can also install cabal-install.

Known users

• vabal

Known problems

Limited distributions supported

Currently only GNU/Linux distributions compatible with the upstream GHC binaries are supported.

Precompiled binaries

Since this uses precompiled binaries you may run into several problems.

Missing libtinfo (ncurses)

You may run into problems with ncurses and missing libtinfo, in case your distribution doesn't use the legacy way of building ncurses and has no compatibility symlinks in place.

Ask your distributor on how to solve this or try to compile from source via ghcup compile <version>.

Libnuma required

This was a bug in the build system of some GHC versions that lead to unconditionally enabled libnuma support. To mitigate this you might have to install the libnuma package of your distribution. See here for a discussion.

Compilation

Although this script can compile GHC for you, it's just a very thin wrapper around the build system. It makes no effort in trying to figure out whether you have the correct toolchain and the correct dependencies. Refer to the official docs on how to prepare your environment for building GHC.

FAQ

1. Why reimplement stack?

ghcup is not a reimplementation of stack. The only common part is automatic installation of GHC, but even that differs in scope and design.

2. Why not support windows?

Consider using Chocolatey or ghcups.

3. Why the haskell reimplementation?

Why not?