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Linux 2.6 - man page for getpagesize (linux section 2)

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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 memory page, where "page" is a
       fixed-length block, the unit for memory allocation and file mapping performed by mmap(2).

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.

NOTES
       Portable applications should employ sysconf(_SC_PAGESIZE) instead of getpagesize():

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

       (Most systems allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE.)

       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  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)

COLOPHON
       This  page  is  part of release 3.55 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					    2010-11-16				   GETPAGESIZE(2)
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