Name
getpagesize — get memory page size
Synopsis
#include <unistd.h>
int getpagesize( |
void); |
![[Note]](../stylesheet/note.png) |
Note | ||
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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.
COLOPHON
This page is part of release 3.24 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/.
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Copyright (C) 2001 Andries Brouwer <aebcwi.nl> Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. |