getpagesize - get memory page size
#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
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).
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
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.
mmap(2),
sysconf(3)