sendmail, 4th Edition

The _CF_DIR_ m4 Macro

It can be advantageous to maintain all the files that make up your local m4 configuration separately from the sendmail distribution. This prevents new releases of sendmail from clobbering your source files. It also allows you to maintain configuration information more conveniently (perhaps under rcs(1) control) and to use programs such as make(1) to simplify configuration and installation.

Most modern versions of m4 allow you to define m4 macros on the command line, and one such m4 macro is recognized internally by the m4 technique:

_CF_DIR_

This command-line m4 macro tells m4 where the m4/cf.m4 file described earlier is located. It needs to have its value set to be the cf directory under the sendmail source distribution, and it needs to end in a slash character. For example, GNU m4 version 1.2 allows this:

% setenv CFDIR /usr/local/src/mail/sendmail/cf/
% /usr/local/gnu/bin/m4 -D_CF_DIR_=${CFDIR} ${CFDIR}m4/cf.m4 localsun.mc \
    > sendmail.cf

Notice that we store the value for _CF_DIR_ in an environment variable. Note that GNU m4 can figure out the _CF_DIR_ path itself from the path of the cf.m4 file. We include _CF_DIR_ here merely as an example. If your version of m4 lacks this ability, you should consider upgrading.

With the _CF_DIR_ m4 macro, we can further simplify configuration and installation by using make(1). To illustrate, consider the following few lines from a Makefile on a SunOS system:

M4=/usr/local/gnu/bin/m4 CFDIR=/usr/local/src/mail/sendmail/cf/ localsun: ...