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(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

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 architec-
       ture.  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 3.25 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                                                      2007-07-26                                             GETPAGESIZE(2)