sendmail, 4th Edition

The Order of mc Lines

As you have seen, some mc lines must precede others. This is necessary partly because m4(1) is a one-pass program, and partly because the order of items in the final sendmail.cf file is also critical. The recommended order is:

VERSIONID( )           ← see §17.2.3.1 on page 593
OSTYPE( )              ← see §17.2.2.1 on page 590
DOMAIN( )             ← see §17.2.2.3 on page 591
option definitions    ← see §24.4 on page 953
FEATURE( )            ← see §17.8 on page 611
macro definitions    ← see §21.7 on page 796
MAILER( )              ← see §17.2.2.2 on page 590
ruleset definitions   ← see §19.1.7 on page 688

If in doubt about where some particular item should go, look in the many example files in cf/cf. Some of them (especially the file knecht.mc) will also give you good ideas about how you can improve your own mc file.

VERSIONID m4 macro

The VERSIONID m4 macro is used to insert an identifier into each mc and m4 file that becomes a part of your final .cf file. Each file that is supplied with sendmail already has such an identifier. You should include a similar identifier in each of your mc files:

VERSIONID(`$Id$')

Here, the VERSIONID m4 macro is used to insert an RCS-style revision number. The $Id$ becomes an actual version number when the file is checked in with ci(1). Arbitrary text can appear between the single quotes. You can use RCS, SCCS, or any other kind of revision identification system. The text cannot contain a newline because the text appears in the .cf file as a comment:

#####  $Id$ #####

Use of VERSIONID and revision control ...