ghcup-hs/docs/guide.md

User Guide

ghcup --help is your friend.

Basic usage

For the simple interactive TUI (not available on windows), run:

ghcup tui

For the full functionality via cli:

# 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

Tags and shortcuts

GHCup has a number of tags and version shortcuts, that can be used as arguments to install/set etc. All of the following are valid arguments to ghcup install ghc:

• latest, recommended
• base-4.15.1.0
• 9.0.2, 9.0, 9

If the argument is omitted, the default is recommended.

Configuration

A configuration file can be put in ~/.ghcup/config.yaml. The default config file explaining all possible configurations can be found in this repo: config.yaml.

Partial configuration is fine. Command line options always override the config file settings.

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 scripts/shell-completions directory of this repository.

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).

Caching

GHCup has a few caching mechanisms to avoid redownloads. All cached files end up in ~/.ghcup/cache by default.

Downloads cache

Downloaded tarballs (such as GHC, cabal, etc.) are not cached by default unless you pass ghcup --cache or set caching in your config via ghcup config set cache true.

Metadata cache

The metadata files (also see github.com/haskell/ghcup-metadata) have a 5 minutes cache per default depending on the last access time of the file. That means if you run ghcup list 10 times in a row, only the first time will trigger a download attempt.

Clearing the cache

If you experience problems, consider clearing the cache via ghcup gc --cache.

Compiling GHC from source

Compiling from source is supported for both source tarballs and arbitrary git refs. See ghcup compile ghc --help for a list of all available options.

If you need to overwrite the existing build.mk, check the default files in data/build_mk, copy them somewhere, adjust them and pass --config path/to/build.mk to ghcup compile ghc. Common build.mk options are explained here.

Make sure your system meets all the prerequisites.

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.

XDG support

To enable XDG style directories, set the environment variable GHCUP_USE_XDG_DIRS to anything.

Then you can control the locations via XDG environment variables as such:

• XDG_DATA_HOME: GHCs will be unpacked in ghcup/ghc subdir (default: ~/.local/share)
• XDG_CACHE_HOME: logs and download files will be stored in ghcup subdir (default: ~/.cache)
• XDG_BIN_HOME: binaries end up here (default: ~/.local/bin)
• XDG_CONFIG_HOME: the config file is stored in ghcup subdir as config.yaml (default: ~/.config)

Note that ghcup makes some assumptions about structure of files in XDG_BIN_HOME. So if you have other tools installing e.g. stack/cabal/ghc into it, this will likely clash. In that case consider disabling XDG support.

Env variables

This is the complete list of env variables that change GHCup behavior:

• GHCUP_USE_XDG_DIRS: see XDG support above
• TMPDIR: where ghcup does the work (unpacking, building, ...)
• GHCUP_INSTALL_BASE_PREFIX: the base of ghcup (default: $HOME)
• GHCUP_CURL_OPTS: additional options that can be passed to curl
• GHCUP_WGET_OPTS: additional options that can be passed to wget
• GHCUP_GPG_OPTS: additional options that can be passed to gpg
• GHCUP_SKIP_UPDATE_CHECK: Skip the (possibly annoying) update check when you run a command
• CC/LD etc.: full environment is passed to the build system when compiling GHC via GHCup

Installing custom bindists

There are a couple of good use cases to install custom bindists:

1. manually built bindists (e.g. with patches)
   • example: ghcup install ghc -u 'file:///home/mearwald/tmp/ghc-eff-patches/ghc-8.10.2-x86_64-deb10-linux.tar.xz' 8.10.2-eff
2. GHC head CI bindists
   • example: ghcup install ghc -u 'https://gitlab.haskell.org/api/v4/projects/1/jobs/artifacts/master/raw/ghc-x86_64-fedora27-linux.tar.xz?job=validate-x86_64-linux-fedora27' head
3. DWARF bindists
   • example: ghcup install ghc -u 'https://downloads.haskell.org/~ghc/8.10.2/ghc-8.10.2-x86_64-deb10-linux-dwarf.tar.xz' 8.10.2-dwarf

Since the version parser is pretty lax, 8.10.2-eff and head are both valid versions and produce the binaries ghc-8.10.2-eff and ghc-head respectively. GHCup always needs to know which version the bindist corresponds to (this is not automatically detected).

Mirrors

GHCup allows to use custom mirrors/download-info hosted by yourself or 3rd parties.

To use a mirror, set the following option in ~/.ghcup/config.yaml:

url-source:
  # Accepts file/http/https scheme
  OwnSource: "https://some-url/ghcup-0.0.6.yaml"

See config.yaml for more options.

Alternatively you can do it via a cli switch:

ghcup --url-source=https://some-url/ghcup-0.0.6.yaml list

Known mirrors

1. https://mirror.sjtu.edu.cn/docs/ghcup

Isolated installs

Ghcup also enables you to install a tool (GHC, Cabal, HLS, Stack) at an isolated location of your choosing. These installs, as the name suggests, are separate from your main installs and DO NOT conflict with them.

• No symlinks are made to these isolated installed tools, you'd have to manually point to them wherever you intend to use them.

• These installs, can also NOT be deleted from ghcup, you'd have to go and manually delete these.

You need to use the --isolate or -i flag followed by the directory path.

Examples:

1. install an isolated GHC version at location /home/user/isolated_dir/ghc/

   • ghcup install ghc 8.10.5 --isolate /home/user/isolated_dir/ghc

2. isolated install Cabal at a location you desire

   • ghcup install cabal --isolate /home/username/my_isolated_dir/

3. do an isolated install with a custom bindist

   • ghcup install ghc --isolate /home/username/my_isolated_dir/ -u 'https://gitlab.haskell.org/api/v4/projects/1/jobs/artifacts/master/raw/ghc-x86_64-fedora27-linux.tar.xz?job=validate-x86_64-linux-fedora27' head

4. isolated install HLS

   • ghcup install hls --isolate /home/username/dir/hls/

5. you can even compile ghc to an isolated location.

   • ghcup compile ghc -j 4 -v 9.0.1 -b 8.10.5 -i /home/username/my/dir/ghc

Continuous integration

On windows, ghcup can be installed automatically on a CI runner non-interactively like so:

Set-ExecutionPolicy Bypass -Scope Process -Force;[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072;Invoke-Command -ScriptBlock ([ScriptBlock]::Create((Invoke-WebRequest https://www.haskell.org/ghcup/sh/bootstrap-haskell.ps1 -UseBasicParsing))) -ArgumentList $false,$true,$true,$false,$false,$false,$false,"C:\"

On linux/darwin/freebsd, run the following on your runner:

curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_MINIMAL=1 sh

This will just install ghcup and on windows additionally msys2.

For the full list of env variables and parameters to tweak the script behavior, see:

• bootstrap-haskell for linux/darwin/freebsd
• bootstrap-haskell.ps1 for windows

github workflows

On github workflows you can use https://github.com/haskell/actions/. GHCup itself is also pre-installed on all platforms, but may use non-standard install locations.

GPG verification

GHCup supports verifying the GPG signature of the metadata file. The metadata file then contains SHA256 hashes of all downloads, so this is cryptographically secure.

First, obtain the gpg key:

gpg --batch --keyserver keys.openpgp.org --recv-keys 7784930957807690A66EBDBE3786C5262ECB4A3F

Then verify the gpg key in one of these ways:

1. find out where I live and visit me to do offline key signing
2. figure out my mobile phone number and call me to verify the fingerprint
3. more boring: contact me on Libera IRC (maerwald) and verify the fingerprint

Once you've verified the key, you have to figure out if you trust me.

If you trust me, then you can configure gpg in ~/.ghcup/config.yaml:

gpg-setting: GPGLax # GPGStrict | GPGLax | GPGNone

In GPGStrict mode, ghcup will fail if verification fails. In GPGLax mode it will just print a warning. You can also pass the mode via ghcup --gpg <strict|lax|none>.

Tips and tricks

with_ghc wrapper (e.g. for HLS)

Due to some HLS bugs it's necessary that the ghc in PATH is the one defined in cabal.project. With some simple shell functions, we can start our editor with the appropriate path prepended.

For bash, in e.g. ~/.bashrc define:

with_ghc() {
  local np=$(ghcup --offline whereis -d ghc $1 || { ghcup --cache install ghc $1 && ghcup whereis -d ghc $1 ;})
  if [ -e "${np}" ] ; then
    shift
    PATH="$np:$PATH" "$@"
  else
    >&2 echo "Cannot find or install GHC version $1"
    return 1
  fi
}

For fish shell, in e.g. ~/.config/fish/config.fish define:

function with_ghc
  set --local np (ghcup --offline whereis -d ghc $argv[1] ; or begin ghcup --cache install ghc $argv[1] ; and ghcup whereis -d ghc $argv[1] ; end)
  if test -e "$np"
    PATH="$np:$PATH" $argv[2..-1]
  else
    echo "Cannot find or install GHC version $argv[1]" 1>&2
    return 1
  end
end

Then start a new shell and issue:

# replace 'code' with your editor
with_ghc 8.10.5 code path/to/haskell/source

Cabal and HLS will now see 8.10.5 as the primary GHC, without the need to run ghcup set all the time when switching between projects.