Sendmail, 3rd Edition

m4 Macros by Function

The m4 technique uses a huge number of macros to accomplish the complex task of creating configuration files for all possible circumstances. Many are detailed in the reference section at the end of this chapter. Many others are documented in chapters dedicated to particular subjects. Here, we summarize many of the m4 macros by classification or function. Note that a comprehensive list of all m4 macros is available in Appendix A.

Options

Options can be set, unset, and changed in your mc file with simple define statements. For example, the following line sets the location of the alias file and thus the AliasFile option:

define(`ALIAS_FILE', `nis:-N mail.aliases')

Configuring options with the m4 technique is described in Section 24.4 (with the individual m4 option names listed in Table 24-3 of that section). Options are described in general in Chapter 24. We recommend you leap ahead to that chapter, learn about options that will make your use of sendmail more valuable, then return here.

Define sendmail Macros

Defined sendmail macros can be declared in your mc file. Those that are useful are listed in Table 21-5 of Section 21.7. That section also describes the general technique of defining sendmail macros via m4. To illustrate, for example:

define(`BITNET_RELAY', `host.domain')

causes the value host.domain to be assigned to an internal sendmail macro (currently $B). Non-m4 specific defined macros can be declared with the LOCAL_CONFIG technique (Section 4.3.3.1).