The following typographic conventions are used in this book:
Italic
Used for names, including pathnames, filenames, program and command names, usernames, hostnames, machine names, and mailing-list names , as well as for mail addresses. It also is used to indicate that part of a program's output is not specific. For example, " error: number or file " indicates that the error will be shown either as a number or as a filename. Italic is also used to emphasize new terms and concepts when they are introduced.
Constant Width
Used in examples to show the contents of files or the output from commands. This includes examples from the configuration file or other files such as message files, shell scripts, or C-language program source. Constant-width text is quoted only when necessary to show enclosed space; for example, the five-character " From " header.
Single characters , symbolic expressions, and command-line switches are always shown in constant-width font. For instance, the o option illustrates a single character, the rule $- illustrates a symbolic expression, and -d illustrates a command-line switch.
Constant Bold
Used in examples to show commands or some other text that is to be typed literally by the user . For example, the phrase cat /var/run/sendmail.pid means the user should type "cat /var/run/sendmail.pid" exactly as it appears in the text or example.
Constant Italic
Used in examples to show variables for which a context-specific substitution should be or will be made. In the string S num , for example, num will be a user-assigned integer.
