.. _flycheck-installation:

==============
 Installation
==============

This document gives you detailed instructions and information about installing
Flycheck.

Prerequisites
=============

Flycheck needs GNU Emacs |min-emacs| and works best on Unix-like systems like
Linux or macOS.  It does not support older releases of GNU Emacs or other
flavours of Emacs (e.g. XEmacs, Aquamacs, etc.).

.. _flycheck-windows-support:

Windows support
---------------

**Flycheck does not explicitly support Windows**, but tries to maintain Windows
compatibility and should generally work fine on Windows, too.  However, we can
neither answer questions about Windows nor fix bugs that only occur on Windows
without the help of active Windows users.  Please watch out for `known Windows
issues`_.

.. _known Windows issues: https://github.com/flycheck/flycheck/labels/arch%3A%20windows%20only

Syntax checking tools
---------------------

Flycheck does not check buffers itself but relies on *external* programs to
check buffers.  These programs must be installed separately.  Please take a look
at the :ref:`list of supported languages <flycheck-languages>` to find out what
tools are required for a particular language.

Many of these programs are available in the package repositories of Linux
distributions or in Homebrew_ for macOS.  Others can be installed with standard
package managers such as Rubygems, NPM, Cabal, etc.

.. important::

   For a GUI Emacs on MacOS we recommend to install and configure
   exec-path-from-shell_ to make Emacs use the proper ``$PATH`` and avoid a
   :ref:`common setup issue on MacOS <flycheck-macos-exec-path-from-shell>`.

.. _Homebrew: https://brew.sh
.. _exec-path-from-shell: https://github.com/purcell/exec-path-from-shell

.. _flycheck-package-installation:

Package installation
====================

We recommend to install Flycheck with Emacs' built-in package manager.  Flycheck
is available in the popular `MELPA`_ archive which serves up to date snapshots
of Flycheck's development state.  We recommend to read through the
:doc:`changelog </changes>` before every upgrade to check for any breaking
changes that might affect you.

.. note::

   The sibling repository `MELPA Stable`_ provides packages for Flycheck
   releases.  If you prefer to follow the most recent changes use MELPA instead,
   but be aware that, while we try to be careful about the stability of the
   development snapshots, we may make breaking changes anytime without prior
   announcement.

Unfortunately the MELPA repositories are not available in Emacs by default.  You
must explicitly add them to `package-archives` with the following code in your
:term:`init file`:

.. code-block:: elisp

   (require 'package)

   (add-to-list 'package-archives
                '("MELPA Stable" . "https://stable.melpa.org/packages/") t)
   (package-initialize)

This adds MELPA Stable; for MELPA replace ``https://stable.melpa.org`` with
``https://melpa.org`` and change the name accordingly.  If you do not know where
your init file is inspect the value of `user-init-file` with :kbd:`C-h v
user-init-file`.

Once the repository is set up you can install Flycheck from Emacs' package menu
at :kbd:`M-x list-packages`, or directly with :kbd:`M-x package-install RET
flycheck`.

use-package
-----------

You may want to take a look at `use-package`_ which provides simple syntax to
declare and configure packages in your init file.  Specifically it allows to
automatically install missing packages from package archive when Emacs starts.

Add the following form to your init file to setup Flycheck with `use-package`_:

.. code-block:: elisp

   (use-package flycheck
     :ensure t
     :init (global-flycheck-mode))

Then press :kbd:`C-M-x` with point somewhere in this form to install and enable
Flycheck for the current Emacs session.

.. _flycheck-distribution-packages:

Distribution packages
---------------------

Alternatively some distributions provide binary packages of Flycheck.  We
officially support the following distributions:

* Debian 9 and newer: ``apt-get install elpa-flycheck flycheck-doc`` (the latter
  for our manual).  The `Debian Emacs addon team`_ provides these packages.

.. _Debian Emacs addon team: https://pkg-emacsen.alioth.debian.org/

.. _flycheck-legacy-installation-methods:

Legacy installation methods
===========================

Some users prefer to install Flycheck with legacy methods such as el-get, Git
submodules, etc that were common before Emacs included a package manager.  There
are also many 3rd party packages provided by various package managers.  We do
neither support nor endorse any of these:

.. warning::

   If you install Flycheck in any way other than :ref:`our official packages
   <flycheck-package-installation>` you do so **at your own risk**.

Please beware of breakage, and understand that while we do not actively work
against alternative installation methods we will not make compromises to support
alternative installation methods.  We will close issues reported for alternative
installation if we fail to reproduce them with a proper installation of
Flycheck.

.. _MELPA: https://melpa.org
.. _MELPA Stable: https://stable.melpa.org
.. _Getting Started: https://melpa.org/#/getting-started
.. _use-package: https://github.com/jwiegley/use-package