NAME | SYNOPSIS | DESCRIPTION | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

GETPAGESIZE(2)            Linux Programmer's Manual           GETPAGESIZE(2)

NAME         top

       getpagesize - get memory page size

SYNOPSIS         top

       #include <unistd.h>

       int getpagesize(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpagesize():
           Since glibc 2.12:
               _BSD_SOURCE ||
                   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
           Before glibc 2.12:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
               _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

DESCRIPTION         top

       The function getpagesize() returns the number of bytes in a memory
       page, where "page" is a fixed-length block, the unit for memory
       allocation and file mapping performed by mmap(2).

CONFORMING TO         top

       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.

NOTES         top

       Portable applications should employ sysconf(_SC_PAGESIZE) instead of
       getpagesize():

           #include <unistd.h>
           long sz = sysconf(_SC_PAGESIZE);

       (Most systems allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE.)

       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.

SEE ALSO         top

       mmap(2), sysconf(3)

COLOPHON         top

       This page is part of release 3.70 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       http://www.kernel.org/doc/man-pages/.

Linux                            2010-11-16                   GETPAGESIZE(2)