getpagesize — get memory page size
#include <unistd.h>
int
getpagesize( |
void) ; |
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();
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.
Whether getpagesize
() is
present as a Linux system call depends on the architecture.
If it is, it returns the kernel symbol PAGE_SIZE, which is
architecture and machine model dependent. Generally, one uses
binaries that are architecture but not machine model
dependent, 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.
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