Conventions Used in This Book
The following conventions are used in this
Used for Unix file, directory, command, user, and group names. It is
also used for URLs and to emphasize new terms and concepts when they
- Constant Width
Used for code examples, system output, and passwords.
- Constant Width Italic
Used in examples for variable input or output (e.g., a filename).
Constant Width Bold
Used in examples for user input.
Used in examples to show input typed by the user that is not echoed
by the computer. This is mainly used for passwords and passphrases
that are typed.
- call( )
indicate a system call, in contrast to a command. In the original
edition of the book, we referred to commands in the form
command(1) and to calls in the form
call(2) or call(3), in
which the number indicates the section of the Unix
programmer's manual in which the command or call is
described. Because different vendors now have diverged in their
documentation section numbering, we try to avoid this convention in
this edition of the book. (Consult your own documentation index for
the right section.) The call( ) convention is
helpful in differentiating, for example, between the
crypt command and the crypt(
) library function.
Unix C shell prompt.
T he Unix Bourne shell or Korn
The Unix superuser prompt (Korn,
Bourne, or C shell). We usually use this symbol for examples that
should be executed by root.
Normally, we will use the Bourne or Korn shell in our examples unless
we are showing something that is unique to the C shell.
- [ ]
Surrounds optional values in a
description of program syntax. (The brackets themselves should never
Ctrl-X or ^X indicate the use of control
characters. They mean "Hold down the Control key
while typing the character
All command examples are followed by Return unless otherwise
This icon designates a note, which is an important aside to the
This icon designates a warning relating to the nearby text.