NAME

getpagesize - get memory page size

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

#include <unistd.h>

int getpagesize(void);

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

getpagesize():

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

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).

VERSIONS

A user program should not hard-code a page size, neither as a literal nor using the PAGE_SIZE macro, because some architectures support multiple page sizes.

This manual page is in section 2 because Alpha, SPARC, and SPARC64 all have a Linux system call getpagesize() though other architectures do not, and use the ELF auxiliary vector instead.

STANDARDS

None.

HISTORY

This call first appeared in 4.2BSD. SVr4, 4.4BSD, SUSv2. In SUSv2 the getpagesize() call was labeled LEGACY, and it was removed in POSIX.1-2001.

glibc 2.0 returned a constant even on architectures with multiple page sizes.