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 2.19:
_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
The function getpagesize() returns the number of bytes in a memory
page, where "page" is a fixed-length block, the unit for memory alloca-
tion 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 ma-
chine model, in order to have a single binary distribution per archi-
tecture. 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 de-
rived 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 5.07 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
https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 GETPAGESIZE(2)