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getpagesize - get memory page size
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() uses, is found using
long sz = sysconf(_SC_PAGESIZE);
(where some systems also allow the synonym _SC_PAGE_SIZE for
int sz = getpagesize();
This call first appeared in 4.2BSD.
SVr4, 4.4BSD, SUSv2. In SUSv2 the getpagesize() call is labeled
"legacy", and in POSIX 1003.1-2001 it has been dropped. HPUX does not
have 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