Controlling the Raspberry Pi's GPIO pins is surprisingly simple using the GPIO command-line interface.

First, install the GPIO command-line tools by running this:

git clone git://git.drogon.net/wiringPi
cd wiringPi/
./build

Verify that the gpio command-line tool has been installed by running this:

gpio -v

Let's say we have an LED connected to pin 4 (to be more specific, the positive end is connected to pin 4 and the negative end is connected to one end of a resistor, whose other end is connected to the ground pin).

This circuit is similar to the pin-low Write mode we discussed earlier.

You can test this circuit through the following steps:

1. Set the pin 4 to output mode:

gpio mode 4 output

2. Set the pin to high:

gpio write 4 1

You should now see the LED glowing.

3. Set the pin to low:

gpio write 4 0

The LED should...