[Feature Request] Redirect node process stdout to a log file

[dcyoung]

Currently the modifications to the /etc/rc.local file launch the node webapp on start, like so:

su pi -c 'node /home/pi/code/scanse/sweep-3d-scanner/app.js < /dev/null &'

This leaves the stdout printing to the terminal. When using a monitor+keyboard on the pi, the stdout is visible and can clutter and obfuscate the login credentials.

We should direct the output of the process into a text/log file instead. This way the output isn't visible when using a monitor + keyboard, and the file can be viewed/shared by users. This would also help in debugging, where we could ask users to provide the log file.

[dcyoung]

Release v0.2.2 modified etc/rc.local to direct both stdout and stderr to a log file (/home/pi/scanner_output.log). This helps with debugging and also clears up the console during boot when using a monitor + keyboard. Unfortunately the log file is overwritten on boot. So it must be viewed before turning off the pi. This is not ideal, but the stdout of the node webserver would start to build large files if the log file was set to append rather than reset.

I considered directing stdout and stderr to different files, where stdout is overwritten but stderr is appended. This would keep the verbose stdout from generating huge log files, but consulting just the stderr would lose a lot of the context for the preceding actions/conditions that led to the error.

It might be ideal to generate a more verbose log file that is overwritten only when it exceeds some threshold size. This way users could still shutdown the pi and retrieve the log file later. Not sure what the best strategy is for doing this... I'm sure its been documented for the pi many times over.

Additionally we may want to add an option to download the log file from the GUI, and perhaps delete/reset the log file from the GUI as well.

Leaving open for now.