NAME
getpagesize - get memory page size
SYNOPSIS
#include <unistd.h>
int getpagesize(void);
DESCRIPTION
The function
R 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
R _SC_PAGE_SIZE
for
R _SC_PAGESIZE ),
or
#include <unistd.h>
int sz = getpagesize();
CONFORMING TO
SVr4, 4.4BSD, SUSv2.
In SUSv2 the
R 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
R 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
R getpagesize ()
returns a statically derived value, and does not use a system call.
Things are OK in glibc 2.1.
SEE ALSO
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