mpd_trigger

What Is This?

I'd like to let a notification pop up whenever MPD is playing or paused. However, disappointing enough, I failed to find any existing programs/scripts to achieve this little but convenient functionality. Although there is mpd-hiss, it has quite a number of dependencies and is written in Python with several separated files. I think such a simply little desire should not be as complicated as this. Even though I love programming in Python, that project may still need to polished to be flexible and easy to deploy (but it is a good project nevertheless). Being different from it, this project tends to be lightweight and simple but as extensible as it can, but in the end, should be simple. After all, a simple task deserves a simple solution. Now the code is written in C in a single file and highly portable. It uses "patterns" to generate a command once MPD state is being changed and pipes it into a pre-selected shell. During the execution, it consumes few resources and imposes little overhead.

How to Use?

First, compile it by invoking make. The only executable file is mpd_trigger. You could run ./mpd_trigger -h to read the help information. A typical example is as follow (executed in bash):

./mpd_trigger 192.168.248.130 -p 6600 -e "echo 'Hey, {title} is {state}!'"

Then play a song. Besides diagnostic outputs, you should find the output of executing that echo command.

You may have noticed something like {title} which is actually a pattern representing the title of the song is to be filed in that place. mpd_trigger currently supports two kinds of patterns:

• Information patterns: {title}, {artist}, {album}, {track}, {state}, {elapsed_time}, total_time, {elapsed_pct}

• Conditional pattern: {str_to_check?stringa:stringb} which checks whether str_to_check is an empty string, if it is stringa is chosen, otherwise stringb, note that the surrounding braces are removed.

For Mac OS X users, after installing a tool called terminal-notifier, try the following command:

./mpd_trigger -e 'terminal-notifier -title "{title}: {state} ({elapsed_pct}%)" -subtitle "{artist}" -message "{album} @ {track?{track}:unknown track}" -sender com.apple.iTunes'

If you have no idea about how to run this program as a user daemon, try to copy the accompanied file com.ted.mpd_trigger.plist (you should modify the path to the correct location of the compiled mpd_trigger binary and may adjust parameters) to path_to_your_home/Library/LaunchAgents and then execute the following commands:

cd path_to_your_home/Library/LaunchAgents
launchctl load com.ted.mpd_trigger.plist

Finally, it is worth mentioning that patterns can be nested, for example a part of the pattern in last example {track?{track}:unkown track} makes use of such technique. Have fun! :)

Dependencies

• The canonical mpd library: libmpdclient (on which famous mpd clients such as mpc and ncmpcppp also depend)

• Some basic POSIX syscalls (ubiquitous on current unix-like systems)

• For Mac OS X users, they may want to install terminal-notifier if they'd like to, but this is not mandatory since the triggered command is up to you.

• Nothing else.