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       getpagesize - get memory page size


       #include <unistd.h>

       int getpagesize(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpagesize(): _BSD_SOURCE || _XOPEN_SOURCE >= 500


       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();


       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.


       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.


       mmap(2), sysconf(3)


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