sendmail, 4th Edition

Rule Operator Reference

In this section, we describe each rule operator. Note that we exclude operators that are not germane to rules (such as $?, Macro Conditionals: $?, $|, and $. on page 794) and list only those that can be used in rules. Because all rule operators are symbolic, we cannot list them in alphabetical order, so instead we list them in the alphabetical order of pronunciation. That is, for example, $@ (pronounced dollar-at) comes before $: (pronounced dollar-colon).

To avoid confusion based on different ways of pronouncing symbols, we list all the operators in Table 18-4 so that you can easily find them.

Table 18-4. Operators in rules

Operator	§	RHS or LHS	Description or use
$&	$& on page 673	LHS and RHS	Delay macro expansion until runtime.
$@	$@ on page 673	LHS	Match exactly zero tokens (V8 only).
$@	$@ on page 674	RHS	Rewrite once and return.
$@	$@ on page 674	RHS	Specify host in delivery agent “triple”.
$@	$@ on page 674	RHS	Specify DSN status in error agent “triple”.
$@	$@ on page 675	RHS	Specify a database-map argument.
$:	$: on page 675	RHS	Rewrite once and continue.
$:	$: on page 676	RHS	Specify address in delivery agent “triple”.
$:	$: on page 676	RHS	Specify message in error or discard agent “triple”.
$:	$: on page 676	RHS	Specify a default database-map value.
$digit	$digit on page 677	RHS	Copy by position.
$=	$= on page 677	LHS	Match any token in a class.
$>	$> on page 677	RHS	Rewrite through another rule ...