12.4. Differentiating Operating Systems and OS Versions

Some code 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

A complete list of __FreeBSD_version values is available in 章 16, __FreeBSD_version Values.

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