When you are working in the console of an Un*x system you always have the possibility of using some kind of notification system to warn you when a task has completed. Quite typically, that would involve an email that could arrive to your box’ local inbox or, if you have a mail agent properly configure, to some other inbox in the Internet.

With the arriving of the Instant Messaging systems you could somehow move from the good old email notification to some other fancy service. That has been my prefered method for quite a while since I understand email as a “non-instant” messaging system. Basically, I do not want to get instant notifications when a mail arrives. Add to that the hassle of setting some kind of filter criteria to get the notifications only for specific mail rules and the not yet universally supported IMAP4 push method, instead of pulling for newly arrived mail …

Anyway, long story short, for some time now we are using [matrix] as our Instant Messaging service at Igalia so, why not getting notifications there when a task is completed?

Yes, you have guessed correctly, that’s possible and, actually, it’s very easy to set up, specially with the help of matrix-send.

First, you need an account that will send you the notification(s). Ideally, that would be a bot user, but it could be any account. Then, you have get an access token with such user so you can interact with the matrix server from the command line as if it would be any other ordinary matrix client. Finally, you need to create a chat room between that user and your own in order to keep the communication ongoing. All this is explained in matrix’ client-server API documentation but, to make things easier, it would go as follows:

$ curl -XPOST -d '{"user":"", "password":"", "type":"m.login.password"}' "https:///_matrix/client/r0/login"
{
    "access_token": "",
    "device_id": "",
    "home_server": "",
    "user_id": "@:"
}

This will give you the needed access-token.

Now, from your regular matrix client, invite the bot user to a conversation in a new room. Check in the configuration of the new room for its internal ID. It would be something like
!<internal-id>:<home-server>.

Then, accept such invitation from the command line:

$ curl -XPOST -d '{}' "https:///_matrix/client/r0/rooms/%21:/join?access_token="
{
    "room_id": "!:"
}

All that is left is to configure matrix-send and start using it. Mind you, I’ve done a small addition that it has not been merged yet so I would just clone from my fork.

The configuration file would look like this:

$ cat ~/.config/matrix-send/config.ini
[DEFAULT]
endpoint=https:///_matrix/
access_token=
channel_id=!:
msgtype=m.text

The interesting addition from my own is the msgtype field. By default, in matrix-send its value is m.notice which, depending on the configuration, quite typically won’t trigger a notification in your matrix client.

All that is left is to make matrix-send executable and test it:

$ chmod +x /matrix-send.py
$ /matrix-send.py "Hello World!"