Cabal-Install

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The cabal-install package provides the cabal command-line tool which simplifies the process of managing Haskell software by automating the fetching, configuration, compilation and installation of Haskell libraries and programs. Those packages must be prepared using Cabal and should be present at Hackage.

As of 2020-03-15 this page is out of date. Cabal-install 3.0 switched to the v2-* class of commands, while this guide still refers to the v1-ones. See https://cabal.readthedocs.io/en/latest/nix-local-build-overview.html for more info.

Usage

Installing a package

Once you have the tool installed, installing other packages is easy. The first thing to do is to give the command:

 cabal update

This will download the most recent list of packages; this must be done from time to time, to get the latest version of each package, when installing.

It is advisable to use a sandbox, to prevent version incompatibility with earlier installed packages. To initiate a sandbox, give command:

 cabal sandbox init

To install Cabal packages from Hackage use:

 cabal install foo

Other common variations:

 cabal install                             Package in the current directory
 cabal install foo                         Package from the Hackage server
 cabal install foo-1.0                     Specific version of a package
 cabal install 'foo < 2'                   Constrained package version
 cabal install foo bar baz                 Several packages at once
 cabal install foo --dry-run               Show what would be installed
 cabal install foo --constraint=bar==1.0   Use version 1.0 of package bar

One thing to be especially aware of, is that the packages are installed locally by default, whereas the commands

 runhaskell Setup configure
 runhaskell Setup build
 runhaskell Setup install

install globally by default. If you install a package globally, the local packages are ignored. The default for cabal-install can be modified by editing the configuration file.

Help about cabal-install can be obtained by giving commands like:

 cabal --help
 cabal install --help

Commands

Usage:

  cabal COMMAND [FLAGS]

or:

  cabal [GLOBAL FLAGS]

Global flags:

-h --help                         Show this help text
-V --version                      Print version information
   --numeric-version              Print just the version number
   --config-file=FILE             Set an alternate location for the config
                                  file
   --sandbox-config-file=FILE     Set an alternate location for the sandbox
                                  config file (default:
                                  './cabal.sandbox.config')
   --default-user-config=FILE     Set a location for a cabal.config file for
                                  projects without their own cabal.config
                                  freeze file.
   --require-sandbox              Enable requiring the presence of a sandbox
                                  for sandbox-aware commands
   --no-require-sandbox           Disable requiring the presence of a sandbox
                                  for sandbox-aware commands
   --ignore-sandbox               Ignore any existing sandbox
   --ignore-expiry                Ignore expiry dates on signed metadata (use
                                  only in exceptional circumstances)
   --http-transport=HttpTransport Set a transport for http(s) requests.
                                  Accepts 'curl', 'wget', 'powershell', and
                                  'plain-http'. (default: 'curl')
   --enable-nix                   Enable Nix integration: run commands through
                                  nix-shell if a 'shell.nix' file exists
   --disable-nix                  Disable Nix integration: run commands
                                  through nix-shell if a 'shell.nix' file
                                  exists

Commands:

 [global]
  update           Updates list of known packages.
  install          Install packages.

  help             Help about commands.
  info             Display detailed information about a particular package.
  list             List packages matching a search string.
  fetch            Downloads packages for later installation.
  user-config      Display and update the user's global cabal configuration.

 [package]
  get              Download/Extract a package's source code (repository).
  init             Create a new .cabal package file (interactively).

  configure        Prepare to build the package.
  build            Compile all/specific components.
  clean            Clean up after a build.

  run              Builds and runs an executable.
  repl             Open an interpreter session for the given component.
  test             Run all/specific tests in the test suite.
  bench            Run all/specific benchmarks.

  check            Check the package for common mistakes.
  sdist            Generate a source distribution file (.tar.gz).
  upload           Uploads source packages or documentation to Hackage.
  report           Upload build reports to a remote server.

  freeze           Freeze dependencies.
  gen-bounds       Generate dependency bounds.
  outdated         Check for outdated dependencies
  doctest          Run doctest tests.
  haddock          Generate Haddock HTML documentation.
  hscolour         Generate HsColour colourised code, in HTML format.
  copy             Copy the files of all/specific components to install locations.
  register         Register this package with the compiler.
  reconfigure      Reconfigure the package if necessary.

 [sandbox]
  sandbox          Create/modify/delete a sandbox.
  exec             Give a command access to the sandbox package repository.
  repl             Open interpreter with access to sandbox packages.

 [new-style projects (beta)]
  new-build        Compile targets within the project.
  new-configure    Add extra project configuration
  new-repl         Open an interactive session for the given component.
  new-run          Run an executable.
  new-test         Run test-suites
  new-bench        Run benchmarks
  new-freeze       Freeze dependencies.
  new-haddock      Build Haddock documentation

 [other]
  new-update       Updates list of known packages.
  new-install      Install packages.
  new-exec         Give a command access to the store.

For more information about a command use:

 cabal COMMAND --help

To install Cabal packages from Hackage, use:

 cabal install foo [--dry-run]

If --dry-run is specified, the packages are not installed, but a list of packages to install is given.

Occasionally you need to update the list of available packages:

 cabal update

The cabal-install configuration file

You can edit the cabal configuration file to set defaults, for *nix based systems this is:

 ~/.cabal/config

The config file on a Windows system is

 %appdata%\cabal\config

Things to put in the config file

To turn on --global by default:

 user-install: False

The root-cmd configuration parameter can be used to automatically run cabal-install with root privileges on *nix based systems, when needed:

 root-cmd: sudo

Installation

If you have the Haskell Platform installed, you already have cabal-install; no further action is needed.

Windows

Get a pre-built cabal.exe from:

 http://www.haskell.org/cabal/download.html

You must put the cabal.exe in a directory that is on your %PATH%, for example C:\Program Files\Haskell\bin.

Unix

Download the latest cabal-install tarball from:

 http://www.haskell.org/cabal/download.html

It includes a shell script bootstrap.sh that you can run to download and install the other dependencies.

Note this assumes you have the zlib C library and its header files installed. Those header files are usually in a native system package like zlib-devel (On debian-based systems it is zlib1g-dev). You should also have the Haskell packages parsec and network installed. If you installed GHC via your native system package manager then you may also need to use it to install these two packages. (On debian-based systems they are called libghc6-parsec-dev and libghc6-network-dev.)

 tar -zxf cabal-install-0.14.0.tar.gz 
 cd cabal-install-0.14.0
 ./bootstrap.sh

If this completes successfully you will have the cabal binary in ~/.cabal/bin. You should either add this directory to your $PATH or copy the cabal program to some location that is on your $PATH, eg ~/bin.

to get the current list of package from Hackage you should now run:

 cabal update

By default the cabal tool will install programs in ~/.cabal/bin. If you decided not to put this directory on your $PATH then you can get cabal to symlink binaries into another directory, eg ~/bin. To use this feature edit ~/.cabal/config and see the symlink-bindir field. Note that the ~/.cabal/config file is not created until you run a cabal command for the first time, eg cabal update.

Error reporting

Errors in cabal-install can be reported at the GitHub Cabal issues page

FAQ

I just installed packages, but now the packages are not found

This happens when you install a package globally, and the previous packages were installed locally. Note that cabal-install install locally by default and the "runhaskell Setup" commands install globally by default.

How can I uninstall packages?

There is no "cabal uninstall" command. You can only unregister packages with ghc-pkg:

 ghc-pkg unregister

See also

• The Cabal page on GitHub.
• An Introduction to Cabal sandboxes
• The Cabal of Cabal, the undocumented or obscure artifices and intrigues of Cabal.
• Storage and Identification of Cabalized Packages
• Hack-Nix alternative based on the Nix package manager.
• Capri a wrapper over cabal-install and ghc-pkg to operate in project-private mode; similar to Hack-Nix but does not involve any extra software..