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 feature_test_macros(7)):

           Since glibc 2.19:
               _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
           From 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

           #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.  Gener‐
       ally, one uses binaries that are dependent on the architecture but
       not on the machine model, in order to have a single binary distribu‐
       tion 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 5.08 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                            2017-09-15                   GETPAGESIZE(2)

Pages that refer to this page: fincore(1)strace(1)mmap2(2)mmap(2)mremap(2)munmap(2)remap_file_pages(2)syscalls(2)aligned_alloc(3)memalign(3)mmap64(3)numa(3)posix_memalign(3)pvalloc(3)valloc(3)