The following typographical conventions are used in this book:
Indicates new terms, URLs, email addresses, filenames, file extensions, pathnames, directories, and package names, as well as Unix utilities, commands, options, parameters, and arguments.
Constant
        width
        Used to display code samples, file contents, command-line interactions, library names, and database commands.
Constant width
        bold
        Indicates commands or other text that should be typed literally by the user. Also used for emphasis in code.
Constant width italic
        Shows text that should be replaced with user-supplied values.
[ Keywords and other stuff
        ]
        { choice-1 | choice-2
        }