1GETPAGESIZE(2)             Linux Programmer's Manual            GETPAGESIZE(2)
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NAME

6       getpagesize - get memory page size
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SYNOPSIS

9       #include <unistd.h>
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11       int getpagesize(void);
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13   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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15       getpagesize():
16           Since glibc 2.19:
17               _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
18           From glibc 2.12 to 2.19:
19               _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
20           Before glibc 2.12:
21               _BSD_SOURCE || _XOPEN_SOURCE >= 500
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DESCRIPTION

24       The  function  getpagesize()  returns  the  number of bytes in a memory
25       page, where "page" is a fixed-length block, the unit for memory alloca‐
26       tion and file mapping performed by mmap(2).
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CONFORMING TO

29       SVr4,  4.4BSD,  SUSv2.   In  SUSv2  the  getpagesize()  call is labeled
30       LEGACY, and in POSIX.1-2001 it has been dropped; HP-UX  does  not  have
31       this call.
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NOTES

34       Portable  applications  should  employ sysconf(_SC_PAGESIZE) instead of
35       getpagesize():
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37           #include <unistd.h>
38           long sz = sysconf(_SC_PAGESIZE);
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40       (Most systems allow the synonym _SC_PAGE_SIZE for _SC_PAGESIZE.)
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42       Whether getpagesize() is present as a Linux system call depends on  the
43       architecture.   If it is, it returns the kernel symbol PAGE_SIZE, whose
44       value depends on the architecture and machine  model.   Generally,  one
45       uses  binaries  that  are  dependent on the architecture but not on the
46       machine model, in order to have a single binary distribution per archi‐
47       tecture.   This  means that a user program should not find PAGE_SIZE at
48       compile time from a header file, but use  an  actual  system  call,  at
49       least for those architectures (like sun4) where this dependency exists.
50       Here glibc 2.0 fails because its  getpagesize()  returns  a  statically
51       derived  value, and does not use a system call.  Things are OK in glibc
52       2.1.
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SEE ALSO

55       mmap(2), sysconf(3)
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COLOPHON

58       This page is part of release 4.15 of the Linux  man-pages  project.   A
59       description  of  the project, information about reporting bugs, and the
60       latest    version    of    this    page,    can     be     found     at
61       https://www.kernel.org/doc/man-pages/.
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65Linux                             2017-09-15                    GETPAGESIZE(2)