There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "Let's try to copy the /tmp/ directory into our home directory."

A block of code is set as follows:

#!/bin/bash

echo "Hello World!"

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

reader@ubuntu:~/scripts/chapter_10$ grep 'use' grep-file.txt 
We can use this regular file for testing grep.
but in the USA they use color (and realize)!

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

reader@ubuntu:~/scripts/chapter_10$ grep 'e.e' character-class.txt 
eee
e2e
e e

Bold: Indicates a new term, an important word, or words that you see on screen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Click the Install button and watch the installation."