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Conventions Used in This Book

The following typographic conventions appear in this book:


is used for file and command names. It is also used to highlight comments in command examples, and to define terms the first time they appear.

Constant Width

is used in examples and in regular text to show operators, variables, and the output from commands or programs.

Constant Bold

is used in examples to show the user's actual input at the terminal.

Constant Italic

is used in examples to show variables for which a context-specific substitution should be made. The variable filename , for example, would be replaced by some actual filename.


are used to attach parenthetical notes which you should not read on your first reading of this book. Sometimes, lies are spoken to simplify the discussion, and the footnotes restore the lie to truth. Often, the material in the footnote will be advanced information that may not even be discussed anywhere else in the book.