• 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 applications should employ sysconf(_SC_PAGESIZE) instead of this call.
• NOTES
  
  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 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 3.19 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

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