matterhorn: Terminal client for the Mattermost chat system

[ bsd3, chat, program ] [ Propose Tags ]

This is a terminal client for the Mattermost chat system. Please see the README for a list of features and information on getting started.

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Versions [faq] 30802.1.0, 31000.0.0, 40000.0.0, 40000.0.1, 40000.0.2, 40000.1.0, 40400.0.0, 40600.0.0, 40600.1.0, 40700.0.0, 40800.0.0, 40800.0.2, 40900.0.0, 40900.0.1, 40901.0.0, 50200.0.0, 50200.1.0, 50200.1.1, 50200.2.0, 50200.3.0, 50200.3.1, 50200.4.0, 50200.5.0, 50200.6.0, 50200.7.0, 50200.8.0
Change log
Dependencies aeson (>= && <1.5), aspell-pipe (==0.3.*), async (==2.2.*), base (>=4.8 && <5), base-compat (>=0.9 && <0.11), brick (==0.46.*), brick-skylighting (>=0.2 && <0.4), bytestring (==0.10.*), cheapskate (==0.1.*), config-ini (>= && <0.3), connection (==0.2.*), containers (>=0.5.7 && <0.7), data-clist (>=0.1.2 && <0.2), directory (==1.3.*), filepath (==1.4.*), gitrev (==1.3.*), hashable (==1.2.*), Hclip (==3.0.*), mattermost-api (==50200.1.2), microlens-platform (==0.3.*), mtl (==2.2.*), process (>=1.4 && <1.7), random (==1.1.*), semigroups (==0.18.*), skylighting-core (==0.7.*), stm (>=2.4 && <2.6), stm-delay (==0.1.*), strict (==0.3.*), temporary (>=1.2 && <1.4), text (==1.2.*), text-zipper (==0.10.*), time (>=1.6 && <1.9), timezone-olson (>=0.1.7 && <0.2), timezone-series (>= && <0.2), transformers (>=0.4 && <0.6), unix (>= && <, unordered-containers (==0.2.*), utf8-string (==1.0.*), uuid (==1.3.*), vector (<0.13), vty (>=5.23.1 && <5.26), word-wrap (>=0.4.0 && <0.5), xdg-basedir (==0.2.*) [details]
License BSD-3-Clause
Copyright ©2016-2019 AUTHORS.txt
Category Chat
Source repo head: git clone
Uploaded by JonathanDaugherty at Fri Mar 15 22:45:13 UTC 2019
Distributions NixOS:50200.7.0
Executables matterhorn
Downloads 9298 total (1359 in the last 30 days)
Rating (no votes yet) [estimated by Bayesian average]
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Status Hackage Matrix CI
Docs not available [build log]
Last success reported on 2019-03-16 [all 3 reports]


Maintainer's Corner

For package maintainers and hackage trustees

Readme for matterhorn-50200.2.0

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Matterhorn is a terminal client for the Mattermost chat system.

New Release Notifications

Get notified about new Matterhorn releases by following our Twitter account!

Chat With the Developers

The Matterhorn developers hang out on the official Mattermost pre-release server. Stop by to get support and say hello!

Quick Start

We provide pre-built binary releases for some platforms. Please see the release list to download a binary release for your platform that matches your server version:

To run Matterhorn, unpack the binary release archive and run the matterhorn binary within. Help is available via the --help or -h flag.

$ matterhorn --help
$ matterhorn

When you run Matterhorn you'll be prompted for your server information and credentials. At present matterhorn supports only username/password authentication.

Note: Version ABBCC.X.Y matches Mattermost server version A.BB.CC. For example, if your Mattermost server version is 3.6.0 then you would download matterhorn version 30600.2.4. See Our Versioning Scheme for details.


For configuration options you have two choices:

  • Interactive configuration entered on each program run
  • Configuration via stored settings in a config file

The first option is useful when trying out the program because you can get up and running without worrying about making a configuration. Once you're ready to make your settings persistent, they can be added to a configuration file. An example configuration file can be found at sample-config.ini. Any settings omitted from the configuration will be obtained interactively at startup.

When looking for configuration files, matterhorn will prefer config.ini in the current working directory, but will look in the typical XDG configuration directories (you'll probably want to use $HOME/.config/matterhorn/config.ini) and as a last resort look for a globally-accessible /etc/matterhorn/config.ini.

Using the Client

The user interface has three main areas:

  • Left: list of channels you're in, and list of users in your team and their statuses (+ means online, - means away, × means Do Not Disturb, and an absent sigil means offline)
  • Right: messages in the current channel
  • Bottom: editing area for writing, editing, and replying to messages

You can use built-in keybindings or /cmd-style commands to operate the client. Keybinding information may be obtained in a number of ways:

  • The /help command within Matterhorn.

  • The F1 key within Matterhorn.

  • Running matterhorn with the -k argument for text keybindings

  • Running matterhorn with the -K argument for Markdown keybindings

    Note: The latter two commands do not start the client but simply print to stdout and exit. The bindings shown include any user overrides from the config files; use the -i flag to skip loading the local config files and see the Matterhorn default keybindings.

Keybindings may include modifiers such as Control (indicated with a C- prefix) or Meta (indicated with a M- prefix). If your keyboard has an Alt key, that will work as Meta. If it does not, you may be able to configure your terminal to provide Meta via other means (e.g. iTerm2 on OS X can be configured to make the left Option key work as Meta). Keybindings can be customized in the configuration file; see /help keybindings for details.

To join a channel, use the /join command to choose from a list of available channels. To create a channel, use /create-channel. To leave a channel, use /leave-channel.

To create a private group chat amongst yourself and other users, use the /group-msg command, e.g., /group-msg user1 user2.

To see the members in the current channel, use the /members command.

To send a message, type it into the editor and press Enter to send. To send a multi-line message, toggle multi-line mode with the default binding M-e. Markdown syntax is accepted.

To edit your current message in an external editor ($EDITOR), use the default binding of M-k.

To preview the message you're about to send while you compose it (e.g. to check on how your Markdown syntax will be rendered), toggle preview mode with the default binding M-p.

To change channels, use /focus or one of the default bindings C-n (next channel), C-p (previous channel), C-g (fast channel switch).

To directly message another user, use /focus or C-g.

C-g channel switching mode does a substring match of the input text on the channel and usernames; metacharacters ^ and $ at the beginning or end of input, respectively, anchor the match in case of multiple matches. The cursor in this mode is usable with C-n and C-p.

To switch to the channel you were in prior to the current channel, use the default binding M-s (swap). The most recent channel is marked in the channel list with a "<" indicator.

To switch to the next channel with unread messages, use the default binding M-a.

To quickly show a list of URLs mentioned in the current channel and then open one in your local browser, use the default binding of C-o and configure the urlOpenCommand configuration setting.

To edit, delete, flag, or reply to a message, select a message with the default binding of C-s. Use the default binding of C-c to cancel these operations.

Messages that have been flagged can be viewed with either the /flags command or M-8. This view allows you to select and unflag particular messages, as well.

To enable spell-checking in the message editor, install Aspell and set enableAspell to True in your configuration. To override Aspell's choice of master dictionary, set the aspellDictionary option to the name of the dictionary you'd like to use.

To attach a file to the post being edited, use the default binding of C-x. The window that appears will let you browse the filesystem to find a file to attach. In this window, o opens the selected file with your URL open command to let you preview your choice, Enter enters the selected directory or selects the current file for attachment, and arrow keys change selection. Once you've attached a file, you'll see the text (1 attachment) above your message editor. You can attach additional files or remove existing attachments by pressing C-x again.


  • Channel creation, deletion, and membership management commands
  • Optimized channel-switching modes: M-a, M-s, and C-g
  • Message posting, editing, replying, and deletion
  • Markdown rendering
  • Convenient URL-opening with local browser
  • Secure password entry via external command (e.g. OSX keychain)
  • Yank verbatim content from messages into the system clipboard
  • Preview message rendering before sending
  • Optional smart quoting for efficient Markdown entry
  • Edit messages with $EDITOR
  • Rebindable keys (see /help keybindings)
  • Message editor with kill/yank buffer and readline-style keybindings
  • Tab-completion of usernames, channel names, commands, and fence code block languages
  • Support for attachment upload and download
  • Spell-checking via Aspell
  • Syntax highlighting of fenced code blocks in messages (works best in 256-color terminals)
  • Flagging and unflagging of posts, which are then viewable with M-8 or /flags
  • Support for SOCKS 4 and 5 proxies via the ALL_PROXY, HTTP_PROXY, and HTTPS_PROXY environment variables. (Plain HTTP proxies are not yet supported.)
  • Multiple color themes with color theme customization support
  • Custom notifications via notification scripts (see the activityNotifyCommand configuration setting).

Spell Checking Support

Matterhorn uses aspell to perform spell-checking of your message input. To use this feature:

  • Install aspell and ensure that your installation includes dictionaries corresponding to your LANG setting. To check this, ask aspell to check some input:
    $ echo stuff | aspell -a
    Error: No word lists can be found for the language "en".
    $ echo $LANG
    If Aspell succeeds, the output will look like this:
    @(#) International Ispell Version 3.1.20 (but really Aspell
  • Set enableAspell to True in your config.ini
  • Enter any message input in the message editor in matterhorn. After a short delay after you stop typing, misspelled words will turn red.


To build Matterhorn, you'll need an appropriate ghc/cabal installation. We currently build on GHC 8.4. We suggest you use a binary release if possible.

matterhorn is built by running the following commands:

$ git pull
$ git submodule update --init
$ ./

Our Versioning Scheme

Matterhorn version strings will be of the form ABBCC.X.Y where ABBCC corresponds to the lowest Mattermost server version expected to be supported by the release. For example, if a release supports Mattermost server version 1.2.3, the ABBCC portion of the matterhorn version will be 10203. There may be later versions of the Mattermost server that are supported (e.g. Matterhorn 50200.X.Y supports Mattermost server versions 5.2 through at least 5.8).

The X.Y portion of the version corresponds to our own version namespace for the package. If the server version changes, X.Y SHOULD be 0.0. Otherwise the first component should increment if the package undergoes major code changes or functionality changes. The second component alone should change only if the package undergoes security fixes or other bug fixes.

Our Design Philosophy

Overall, we strive to build a terminal client that provides the same basic feature set as the web client. This is reflected in the state of the client, our issue backlog, and the content of our wiki feature design discussions.

We intend to add web client features to Matterhorn to the extent that they can be added sensibly in a terminal setting. Our goal is to do so in a way that minimizes surprise to web client users migrating to Matterhorn while also providing the best terminal user experience that we can think of. That might entail adding the web client features but changing their designs to ones better suited for terminal use or it might mean omitting aspects of web client features that rely heavily on mouse- or DOM-related UI idioms. It might also entail adding web client features but deviating slightly on specific behaviors.

If you are used to a web client feature and don't see it in Matterhorn, that's probably because we just haven't gotten to it yet. We would be happy to hear from people wanting to contribute! If you can't contribute, search existing issues to see if we already have an issue for it, or create a new issue and let us know!


If you decide to contribute, that's great! Here are some guidelines you should consider to make submitting patches easier for all concerned:

  • If you want to take on big things, let's have a design/vision discussion before you start coding. Create a GitHub issue and we can use that as the place to hash things out. We'll be interested to discuss any usability / UI, performance, or compatibility issues.
  • Please make changes consistent with the conventions already used in the codebase.
  • We follow a few development practices to support our project and it helps when contributors are aware of these. Please see for more information.

Frequently Asked Questions