166 lines
5.7 KiB
Markdown
166 lines
5.7 KiB
Markdown
`ghcup` makes it easy to install specific versions of `ghc` on GNU/Linux as well as macOS (aka Darwin), and can also bootstrap a fresh Haskell developer environment from scratch.
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It follows the unix UNIX philosophy of [do one thing and do it well](https://en.wikipedia.org/wiki/Unix_philosophy#Do_One_Thing_and_Do_It_Well).
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Similar in scope to [rustup](https://github.com/rust-lang-nursery/rustup.rs), [pyenv](https://github.com/pyenv/pyenv) and [jenv](http://www.jenv.be).
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*Ubuntu users may prefer [hvr's ppa](https://launchpad.net/~hvr/+archive/ubuntu/ghc).*
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*This project was started when [CM](https://github.com/capital-match) was switching from stack to [cabal nix-style builds](https://www.haskell.org/cabal/users-guide/nix-local-build-overview.html).*
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## Table of Contents
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* [Installation](#installation)
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* [Usage](#usage)
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* [Design goals](#design-goals)
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* [How](#how)
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* [Known users](#known-users)
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* [Known problems](#known-problems)
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* [FAQ](#faq)
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## Installation
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Choose one of the following installation methods.
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### Simple bootstrap of ghcup, GHC and cabal-install
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```sh
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# complete bootstrap
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curl https://gitlab.haskell.org/haskell/ghcup/raw/master/bootstrap-haskell -sSf | sh
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# prepare your environment
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. "$HOME/.ghcup/env"
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echo '. $HOME/.ghcup/env' >> "$HOME/.bashrc" # or similar
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# now create a project, such as:
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mkdir myproject && cd myproject
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cabal init -n --is-executable
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cabal v2-run
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```
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### Manual install
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Just place the `ghcup` shell script into your `PATH` anywhere.
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E.g.:
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```sh
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( mkdir -p ~/.ghcup/bin && curl https://gitlab.haskell.org/haskell/ghcup/raw/master/ghcup > ~/.ghcup/bin/ghcup && chmod +x ~/.ghcup/bin/ghcup) && echo "Success"
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```
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Then adjust your `PATH` in `~/.bashrc` (or similar, depending on your shell) like so, for example:
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```sh
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export PATH="$HOME/.cabal/bin:$HOME/.ghcup/bin:$PATH"
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```
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Security aware users may want to use the files from the [release page](https://gitlab.haskell.org/haskell/ghcup/tags/)
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and verify the gpg signatures.
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## Usage
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See `ghcup --help`.
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Common use cases are:
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```sh
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# install the last known "best" GHC version
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ghcup install
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# install a specific GHC version
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ghcup install 8.2.2
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# set the currently "active" GHC version
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ghcup set 8.4.4
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# install cabal-install
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ghcup install-cabal
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# update cabal-install
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cabal new-install cabal-install
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```
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Generally this is meant to be used with [`cabal-install`](https://hackage.haskell.org/package/cabal-install), which
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handles your haskell packages and can demand that [a specific version](https://cabal.readthedocs.io/en/latest/nix-local-build.html#cfg-flag---with-compiler) of `ghc` is available, which `ghcup` can do.
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## Design goals
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1. simplicity
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2. non-interactive
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3. portable
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4. do one thing and do it well (UNIX philosophy)
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### Non-goals
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1. invoking `sudo`, `apt-get` or *any* package manager
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2. handling system packages
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3. handling cabal projects
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4. being a stack alternative
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## How
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Installs a specified GHC version into `~/.ghcup/ghc/<ver>`, and places `ghc-<ver>` symlinks in `~/.ghcup/bin/`.
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Optionally, an unversioned `ghc` link can point to a default version of your choice.
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This uses precompiled GHC binaries that have been compiled on fedora/debian by [upstream GHC](https://www.haskell.org/ghc/download_ghc_8_6_1.html#binaries).
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Alternatively, you can also tell it to compile from source (note that this might fail due to missing requirements).
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In addition this script can also install `cabal-install`.
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## Known users
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* [vabal](https://github.com/Franciman/vabal)
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## Known problems
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### Limited distributions supported
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Currently only GNU/Linux distributions compatible with the [upstream GHC](https://www.haskell.org/ghc/download_ghc_8_6_1.html#binaries) binaries are supported.
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### Precompiled binaries
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Since this uses precompiled binaries you may run into
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several problems.
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#### Missing libtinfo (ncurses)
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You may run into problems with *ncurses* and **missing libtinfo**, in case
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your distribution doesn't use the legacy way of building
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ncurses and has no compatibility symlinks in place.
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Ask your distributor on how to solve this or
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try to compile from source via `ghcup compile <version>`.
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#### Libnuma required
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This was a [bug](https://ghc.haskell.org/trac/ghc/ticket/15688) in the build system of some GHC versions that lead to
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unconditionally enabled libnuma support. To mitigate this you might have to install the libnuma
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package of your distribution. See [here](https://gitlab.haskell.org/haskell/ghcup/issues/58) for a discussion.
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### Compilation
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Although this script can compile GHC for you, it's just a very thin
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wrapper around the build system. It makes no effort in trying
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to figure out whether you have the correct toolchain and
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the correct dependencies. Refer to [the official docs](https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Linux)
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on how to prepare your environment for building GHC.
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## FAQ
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1. Why reimplement stack?
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ghcup is not a reimplementation of stack. The only common part is automatic installation of GHC, but even that differs in scope and design.
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2. Why not contribute to stack and create a library for the common part?
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While this might be an interesting idea, ghcup is about simplicity.
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3. Why write a >1000k LOC bash script?
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ghcup is POSIX sh.
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4. Why write a >1000k LOC POSIX sh script?
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Mainly because the implementation is fairly straight-forward and the script is highly portable. No need to bootstrap anything or set up yet another CI to build ghcup binaries for all possible arches and distros just to perform a very simple task: identify distro and platform and download a GHC bindist.
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5. Why not support windows?
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Portability between linux and windows is difficult. However ghcup doesn't have to be only POSIX based, so a separate windows-specific PowerShell script might be the way to go. Contributions are welcome.
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