sendmail, 4th Edition

Macros in Rules

Each noncomment part of a rule is expanded as the configuration file is read.^[246] Thus, any references to defined macros are replaced with the value that the macro has at that point in the configuration file. To illustrate, consider the following mini configuration file (which we will call test.cf):

V10
Stest
DAvalue1
R $A    $A.new
DAvalue2
R $A    $A.new

First, note that as of V8.10 sendmail, rules (the R lines) cannot exist outside of rule sets (the S line). If you omit a rule set declaration, the following error will be printed and logged:

configfile: line number: missing valid ruleset for "bad rule here"

Second, note that beginning with V8.9, sendmail will complain if the configuration file lacks a correct version number (the V line). Had we omitted that line, sendmail would have printed and logged the following warning:

Warning: .cf file is out of date: sendmail 8.12.6 supports version 10, .cf file is
version 0

The first D line assigns the value value1 to the $A sendmail macro. The second D line replaces the value assigned to $A in the first line with the new value value2. Thus, $A will have the value value1 when the first R line is expanded and value2 when the second is expanded. Prove this to yourself by running sendmail in -bt rule-testing mode to test that file:

% echo =Stest | /usr/sbin/sendmail -bt -Ctest.cf
> =S0
R value1                 value1 . new
R value2                 value2 . new

Here, we use the =S command (Show Rules in a Rule Set with =S on page 306) to show each rule after it has been ...