The following typographic conventions are used in this book:
is 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 is also used to emphasize new terms and concepts when they are introduced.
Constant
Width
is 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
is used in examples
to show commands or some other text that is to be typed
literally by the user. For example, the phrase
cat/etc/sendmail.pid
means the user should type
"cat/etc/sendmail.pid" exactly as it appears in the text or example.
Constant
Italic
is 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.
In the output error:
num
, for example, num
will be a variable value
printed by a program (usually sendmail).
indicates a user shell.
indicates a root shell.