The APPENDDEF( )
m4 directive allows you to append new
information to information that was previously defined. To
illustrate, consider that the locations of your
#include files are sometimes preset in the
appropriate devtools/OS directory. For
OS/UXPDS.V10, for example, the default is:
-I/usr/include -I/usr/ucbinclude
You can use this APPENDDEF( ) directive to add another directory to
this list, without erasing what is already there:
APPENDDEF(`confINCDIRS', `-I/usr/local/include/db')
This causes the new directory to be appended to the declaration in
the previous example:
-I/usr/include -I/usr/ucbinclude -I/usr/local/include/db
Even when you are not sure if a macro has been given a value by
default, you can safely use this APPENDDEF( ) directive because no
harm is caused by appending to an empty definition. See also PREPENDDEF( ).
