12.4. Differentiating Operating Systems and OS Versions

You may come across code that needs modifications or conditional compilation based upon what version of FreeBSD Unix it is running under. The preferred way to tell FreeBSD versions apart are the __FreeBSD_version and __FreeBSD__ macros defined in sys/param.h. If this file is not included add the code,

#include <sys/param.h>

to the proper place in the .c file.

__FreeBSD__ is defined in all versions of FreeBSD as their major version number. For example, in FreeBSD 9.x, __FreeBSD__ is defined to be 9.

#if __FreeBSD__ >= 9
#  if __FreeBSD_version >= 901000
	 /* 9.1+ release specific code here */
#  endif
#endif

All FreeBSD documents are available for download at http://ftp.FreeBSD.org/pub/FreeBSD/doc/

Questions that are not answered by the documentation may be sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.