[Chapter 32] 32.3 Class with m4
Author: Bryan Costales & Eric Allman
Date: 1999-01-06T20:20:37Z

#

| Chapter 32 Class Macros |

## 32.3 Class with m4

In configuring with the m4 technique, many classes are defined for your convenience. You need to be aware of these not only to take advantage of them, but also to avoid reusing their single-character names by mistake. Table 32.1 lists all the macros that the m4 technique uses as of version 8.8.4. Most are described in other sections, but a few are described here. See Section 19.6.30, LOCAL-CONFIG for the general method used for adding members and new class names using the m4 technique.

Table 32.1: Class Macros Used with the m4 Technique
Class |  | Description
--- | --- | ---
$=B | Section 19.6.8, FEATURE(bestmx-is-local) | Domains to lookup in `bestmx` in place of `$=w`
$=E | Section 19.6.4, EXPOSED-USER | List of EXPOSED USERS users
$=F |  | U.C. Berkeley example .mc files
$=G | Section 19.6.11, FEATURE(genericstable) | List of other sites to look up in genericstable
$=L | Section 19.6.38, LOCAL-USER | List of LOCAL USER users
$=M | Section 19.6.12, FEATURE(limited-masquerade) | List of hosts to masquerade
$=O | here | List nonusername characters
$=P | here | List of pseudo domains
$=U | Section 19.4.6, "UUCP" | Locally connected UUCP hosts
$=V | Section 19.4.6 | Hosts connected to UUCP relay $V
$=W | Section 19.4.6 | Hosts connected to UUCP relay $W
$=X | Section 19.4.6 | Hosts connected to UUCP relay $X
$=Y | Section 19.4.6 | Locally connected smart UUCP hosts
$=Z | Section 19.4.6 | Locally connected domainized UUCP hosts

The class `O` is used by the m4 technique to hold a list of characters that cannot be used in local usernames. This list is used to detect certain kinds of routing addresses that might otherwise be difficult to detect. This list initially contains

>     @ %

but may also contain a `!` if UUCP support is included.

The class `P` holds a list of pseudo domains that will not be looked up using DNS. Unless you use a FEATURE, this class will only contain a dot. Various FEATUREs will add appropriate pseudo domains to it, such as .UUCP and .REDIRECT.

32.2 Access Class in Rules |  | 32.4 Pitfalls