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():
           Since glibc 2.19:
               _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
           From glibc 2.12 to 2.19:
               _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
           Before glibc 2.12:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION

       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

       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

       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 glibc 2.0 fails because  its  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

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