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man: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 alloca-
     tion 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 archi-
     tecture.   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 4.16 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)

/data/webs/external/dokuwiki/data/pages/man/getpagesize.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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