Conventions (TCP/IP Network Administration, 3rd Edition)

0.4. Conventions

This book uses the following typographical conventions:

Italic: is used for the names of files, directories, hostnames, domain names, and to emphasize new terms when they are introduced.
Constant width: is used to show the contents of files or the output from commands. It is also used to represent commands, options, and keywords in text.
Constant width bold: is used in examples to show commands typed on the command line.
Constant width italic: is 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.)
%, #: Commands that you would give interactively are shown using the default C shell prompt (%). If the command must be executed as root, it is shown using the default superuser prompt (#). Because the examples may include multiple systems on a network, the prompt may be preceded by the name of the system on which the command was given.
[ option ]: When showing command syntax, optional parts of the command are placed within brackets. For example, ls [ -l ] means that the -l option is not required.