getpagesize(2) — Linux manual page


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

NAME         top

       getpagesize - get memory page size

SYNOPSIS         top

       #include <unistd.h>

       int getpagesize(void);

   Feature Test Macro Requirements for glibc (see

           Since glibc 2.20:
               _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
           Glibc 2.12 to 2.19:
               _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
           Before glibc 2.12:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION         top

       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         top

       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         top

       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
       glibc 2.0 fails because its getpagesize() returns a statically
       derived value, and does not use a system call.  Things are OK in
       glibc 2.1.

SEE ALSO         top

       mmap(2), sysconf(3)

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

Linux                          2021-03-22                 GETPAGESIZE(2)

Pages that refer to this page: fincore(1)strace(1)mmap2(2)mmap(2)mremap(2)remap_file_pages(2)syscalls(2)numa(3)posix_memalign(3)