Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The cat command is commonly used to output the contents of text files, and /proc/asound is a directory."

A block of code is set as follows:

#!/bin/bash 
sudo echo 17 > /sys/class/gpio/export 
sudo echo in > /sys/class/gpio/gpio17/direction 
 
# loop forever 
while true 
do 
  # read the beam state 
  BEAM=$(sudo cat /sys/class/gpio/gpio17/value)

Any command-line input or output is written as follows:

pi@raspberrypi ~ $ cat /proc/asound/cards

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Just right-click on the image file and select Send to, then click on Compressed (zipped) folder."