Conventions Used in This Book

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 ]

Indicates optional keywords and arguments.

{ choice-1 | choice-2 }

Signifies either choice-1 or choice-2.


This icon signifies a tip, suggestion, or general note.


This icon indicates a warning or caution.