Script Development

You can run MPlayer in a script with only a single line, but a scheduling solution will require a bit more. Listing 6 is an example of a streaming script that will play a specific stream, as well as calculate the time it should be stopped. The last line of this script updates the timer.txt file with the date and time that the stream should be stopped.

The solution has several moving parts (see Tables 1 and 2), but it is essentially held together by a few Cron entries.

The taskrunner script must be run by the pi user every minute; thus, the web page is not very responsive when selecting a new stream. Considering the nature of the streaming solution, however, this frequency is acceptable.

The goquiet script should also run every minute. This script will compare the time from the timer.txt file against the system time. When this time is surpassed, it will stop any processes that are streaming or playing MP3 files.

Just like the playing.html page, the timer.txt and queue.txt files and the logs directory must be writable for world (i.e., chmod 777).

The final crontab entry is for the root user. The command looks for a trigger to shutdown the computer. The command uses the find utility to search for the trigger and, upon finding it, removes the file and executes the shutdown:

find /tmp -name shutdown.now \( -exec /bin/rm {} \; -exec /sbin/shutdown \; \)

This is not the most secure solution for a production machine, but it should be OK for a tiny home streaming device.

To test and support a headless solution, I needed to know when processes were running during development. There may be an easier method for seeing what processes are running, but, not knowing it, I came up with a creative solution.

The playing shell script queries the running tasks I am interested in and then dynamically generates the HTML to display those processes to the user using the browser.

Note: It is important that you create a file called playing.html in the HTML input directory with permissions that will allow it to be overwritten; all other files can, and probably should, remain read only.

You can find the full source code on the Linux Magazine FTP site [7].