GETPAGESIZE
Section: Linux Programmer's Manual (2)
Updated: 2010-09-20
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 2.12:
-
_BSD_SOURCE ||
!(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
-
-
Before glibc 2.12:
_BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
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 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 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 3.27 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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Time: 07:34:55 GMT, March 26, 2013