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
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.
This page is part of release 3.14 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/.
