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



NAME
       getpagesize - get memory page size

SYNOPSIS
       #include <unistd.h>

       int getpagesize(void);

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

       getpagesize(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       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

           #include <unistd.h>
           int sz = getpagesize();

CONFORMING TO
       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 bina-
       ries that are dependent on the architecture but not on the machine model, in order to have a single binary dis-
       tribution  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
       mmap(2), sysconf(3)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2007-07-26                    GETPAGESIZE(2)