getpagesize(2) - phpMan

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 applica-
       tions should employ sysconf(_SC_PAGESIZE) instead of this call.

NOTES
       Whether  getpagesize()  is  present as a Linux system call depends on the architec-
       ture.  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
       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 information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



Linux                             2007-07-26                    GETPAGESIZE(2)

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