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 2.19:
               _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
       This page is part of release 5.03 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                             2017-09-15                    GETPAGESIZE(2)