Regular Expressions Cookbook

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, program elements such as variable or function names, values returned as the result of a regular expression replacement, and subject or input text that is applied to a regular expression. This could be the contents of a text box in an application, a file on disk, or the contents of a string variable.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

‹Regular●expression›

Represents a regular expression, standing alone or as you would type it into the search box of an application. Spaces in regular expressions are indicated with gray circles, except when spaces are used in free-spacing mode.

«Replacement●text»

Represents the text that regular expression matches will be replaced with in a search-and-replace operation. Spaces in replacement text are indicated with gray circles.

Matched text

Represents the part of the subject text that matches a regular expression.

⋯

A gray ellipsis in a regular expression indicates that you have to “fill in the blank” before you can use the regular expression. The accompanying text explains what you can fill in.

CR, LF, and CRLF

CR, LF, and CRLF in boxes represent actual line break characters in strings, rather than character escapes such as \r, \n, and \r\n. Such strings can be created by pressing Enter in a multiline edit control in an application, or by using multiline string constants in source code such as verbatim strings in C# or triple-quoted strings in Python.

↵

The return arrow, as you may see on the Return or Enter key on your keyboard, indicates that we had to break up a line to make it fit the width of the printed page. When typing the text into your source code, you should not press Enter, but instead type everything on a single line.

Tip

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

Caution

This icon indicates a warning or caution.