linux 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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpagesize():
	   Since glibc 2.12:
	       _BSD_SOURCE ||
		   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
	   Before glibc 2.12:
	       _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

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(2) uses, is found using

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

       (most systems allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE), or

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

CONFORMING TO
       SVr4, 4.4BSD, SUSv2.  In SUSv2 the getpagesize() call is labeled LEGACY, and in POSIX.1-2001 it has been dropped; HP-UX does not have  this
       call.  Portable applications should employ sysconf(_SC_PAGESIZE) instead of 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,
       whose value depends on the architecture and machine model.  Generally, one uses binaries that are dependent on the architecture but not	on
       the  machine  model,  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 depen-
       dency  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)

COLOPHON
       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2010-09-20							    GETPAGESIZE(2)