redhat man page for getpagesize

GETPAGESIZE(2)						     Linux Programmer's Manual						    GETPAGESIZE(2)

NAME
       getpagesize - get memory page size

SYNOPSIS
       #include <unistd.h>

       int getpagesize(void);

DESCRIPTION
       The  function  getpagesize()  returns  the  number of bytes in a page, where a "page" is the thing used where it says in the description of
       mmap(2) that files are mapped in page-sized units.

       The size of the kind of pages that mmap uses, is found using

	      #include <unistd.h>
	      long sz = sysconf(_SC_PAGESIZE);

       (where some systems also allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE), or

	      #include <unistd.h>
	      int sz = getpagesize();

HISTORY
       This call first appeared in 4.2BSD.

CONFORMING TO
       SVr4, 4.4BSD, SUSv2.  In SUSv2 the getpagesize() call is labeled "legacy", and in POSIX 1003.1-2001 it has been	dropped.   HPUX  does  not
       have this call.

NOTES
       Whether	getpagesize()  is  present  as a Linux system call depends on the architecture.  If it is, it returns the kernel symbol PAGE_SIZE,
       which is architecture and machine model dependent.  Generally, one uses binaries that are architecture but not machine model dependent,	in
       order  to have a single binary distribution per architecture. This means that a user program should not find PAGE_SIZE at compile time from
       a header file, but use an actual system call, at least for those architectures (like sun4)  where  this	dependency  exists.   Here  libc4,
       libc5,  glibc  2.0  fail  because their getpagesize() returns a statically derived value, and does not use a system call.  Things are OK in
       glibc 2.1.

SEE ALSO
       mmap(2), sysconf(3)

Linux 2.5.0							    2001-12-21							    GETPAGESIZE(2)