getpagesize

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():
           Since glibc 2.20:
               _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
           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
       This page is part of release 5.13 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
       https://www.kernel.org/doc/man-pages/.



Linux                              2021-03-22                     GETPAGESIZE(2)