This manual is written using Texinfo, the GNU documentation formatting language. The same set of Texinfo source files is used to produce both the printed and online versions of the documentation. Because of this, the typographical conventions may be slightly different than in other books you may have read.
Examples you would type at the command line are preceded by the common shell primary prompt, ‘$’. The command itself is printed in this font, and the output it produces ‘in this font’, for example:
$ mailfromd --version mailfromd (mailfromd 9.0)
In the text, the command names are printed like this,
command line options are displayed in this font. Some
notions are emphasized like this, and if a point needs to be made
strongly, it is done this way. The first occurrence of
a new term is usually its definition and appears in the same
font as the previous occurrence of “definition” in this sentence.
File names are indicated like this: /path/to/ourfile.
The variable names are represented like this, keywords and
fragments of program text are written in this font.