0.2.3. Conventions
In syntax descriptions and examples, what you would actually type is
shown in the Courier font, as are all command names.
Variables (which you would not
type literally, but would replace with an actual value when you typed
the command) are shown in Courier Italic. Brackets indicate that a
variable is optional. For example, in the syntax line:
vi [filename]
filename would be replaced by an actual filename.
The brackets indicate that the vi command can be
invoked without specifying a filename at all. The brackets themselves
are not typed.
Certain examples show the effect of commands typed at the UNIX shell
prompt. In such examples, what you actually type is shown in
Courier Bold to distinguish it from
the system response. For example:
$ ls
ch01.sgm ch02.sgm ch03.sgm ch04.sgm
In examples, italic indicates a comment which
is not to be typed. Otherwise,
italic emphasizes special terms and
indicate the names of files.