Sunday, August 18, 2013

Conditional Statement in Bash on OS X

I had a bit of trouble getting a conditional statement to evaluate on my bash script in OS X.
I was trying to perform an action if I was online or not.

A good way to test if you are online - ping google of course!

For testing purposes I just got the computer to use text to speech to let me know the result.
Here is my working example, spaces are important!



ping -q -c 1 && FLAG=1
if [ $FLAG = "1" ] ; then
say $FLAG
say $FLAG


If you can ping google,the computer will speak "one"

If you you want to test, change to something you cant resolve such as and run it again.

You shouldn't be able to ping so the computer will speak "zero"

Of course this is a simple example and you need to tailor to your situation, just because you can't ping google doesn't mean you are not online. For example pings could be blocked on your network, however this suits my situation.


Thursday, August 1, 2013

Raspberry Pi Temperature Sensing.

Thanks to Adafruits Raspberry Pi tutorials on temperature sensing,
and this blog on Raspberry Pi temperature sensing to

I decided to do my own.
I also wanted to store the results locally, so I also saved it to a file.

I used a DS18B20 1-wire temperature sensor
Adafruit T-Cobbler
Breadboard and wires.

I wired it up just like they did in their diagrams.

Add one wire support.
In /boot/config.txt add
I subscribed to and in your profile you can find your API key.

After checking out their tutorials I then wrote a bash script to grab the the temperature, then use curl and JSON to upload it.

Here is the script replace SERIALNUMBERHERE with the serial number of your sensor.
API KEY HERE with your API key, and SENSEFEEDID with your feed id.


sudo modprobe w1-gpio

sudo modprobe w1-therm

cd /sys/bus/w1/devices/SERIALNUMBERHERE/



NOW=$(date +"%d_%m_%Y")

DATA=$(cat w1_slave)





echo $OUTPUT >> /root/output_$NOW.csv

curl -H "Content-Type: application/json" -H "Accept: application/json" -X POST -d '{"feed_id": SENSEFEEDID,"value": '$DATA3'}' $URL

I then use Cron to schedule a reading every few minutes.

Then back in you can graph it or manipulate it like you want.