This book uses the following typographical conventions:
Italic
Indicates the names of files, databases, directories, hostnames, domain names, usernames, email addresses, sendmail feature names, Unix utilities, programs, and it is used to emphasize new terms when they are first introduced.
Constant width
Indicates configuration files, commands and variables, m4 macros and built-in commands, and Unix command-line options. It is used to show the contents of files and the output from commands. Keywords are also in constant width.
Constant width bold
Used in examples to show commands or text that you would type.
Constant width italic
Used in examples and text to show variables for which a context-specific substitution should be made. (The variable filename, for example, would be replaced by some actual filename.)
