Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Is used for filenames, directory names , and URLs. It is also used for emphasis and for the first use of a technical term .

Constant width

Is used for examples and to show the contents of files and the output of commands.

Constant width italic

Is used for replaceable elements in examples.

  Constant width bold  

Indicates code in an example that we want you to pay special attention to.

UPPERCASE

In syntax descriptions, usually indicates keywords.

lowercase

In syntax descriptions, usually indicates user -defined items, such as variables .

[ ]

In syntax descriptions, square brackets enclose optional items.

{ }

In syntax descriptions, curly brackets enclose a set of items from which you must choose only one.

In syntax descriptions, a vertical bar separates the items enclosed in curly or square brackets, as in {ON OFF YES NO TRUE FALSE}.

...

In code listings, ellipses indicate missing output that is not critical to understanding the example and that has been removed in the interest of not taking up inordinate amounts of space in the book.

Indicates a tip, suggestion, or general note.

Indicates a warning or caution.

Sample output in code listings has been adapted to fit the size of the book. Strings that contain a lot of spaces have been shortened , and numeric values that extend over two decimal places have been either rounded or truncated. These changes create more readable output and maximize the amount of information we can pack into a sample listing.