GETPAGESIZESection: Linux Programmer's Manual (2)
Index Return to Main Contents
NAMEgetpagesize - get memory page size
DESCRIPTIONThe 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();
CONFORMING TOSVr4, 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.
NOTESWhether 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.
SEE ALSOmmap(2), sysconf(3)