GETPAGESIZE
Section: Linux Programmer's Manual (2)
Updated: 2017-09-15
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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 allocation 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 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
mmap(2),
sysconf(3)
COLOPHON
This page is part of release 4.13 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
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
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