ds18b20

Small program that locates all DS18B20 probes in the system
and opens a logfile for each probe and writes the temperature
from each probe to it's logfile.
Also capable of running as a nagios check.

To build it, just run make in the directory containing the files.

Arguments:
* -v = Verbose. Print additional info on what the program is doing.
* -i = Interval. The interval the probes are checked in seconds.
* -l = Log to text files.
* -r = Maintain RRD files.
* -o = Run once. Print temperatures to screen and exit.
* -f = Foreground. Do not daemonize and run in the foreground.
* -p = Probename. Only report for the named probe or alias. Implies -o and -f
* -m = Minimum temperature for nagios checking (only used with -p)
* -M = Maximum temperature for nagios checking (only used with -p)

Additionally these arguments can also be set in a config file (/etc/ds18b20.cfg).
See example ds18b20.cfg file to see how it's configured.

RRD support is still pending.

The OS on the Raspberry needs to be properly configured. In many cases the
following is needed in /boot/config.txt:

dtoverlay=w1-gpio

Also, the drivers/modules "w1-gpio" and "w1-therm" need to be loaded before the
program is run in order for the probes to show up.

It is not recommended to keep the log files for the probes on the SD disk in the PI.
This is because there are values written to these files every INTERVAL (default 5)
minutes. Such frequent writes will kill your SD card in a short time.
Personally I use the RAM disk for the logs:

ra@raspberrypi ~ $ ls -l /var/probes
lrwxrwxrwx 1 root root 11 Nov 17 04:06 /var/probes -> /run/probes

Then I have a cron job that transfers the logs from the RAM disk to a safe
place every night as the RAM disk is volatile and all data there will be
lost on reboot or powerfailure.

The program can also work as a Nagios check using the -p and -m and/or -M
switches. If the probe named with -p is either below -m or above -M
then the program will exit with a critical message for Nagios.
The program also prints out performance data for Nagios to graph.

Written by Richard Allen and released under the GPLv2 license.

TODO:
* Finish RRD support.
* Consider mysql/mariadb support.