169 lines
3.6 KiB
HTML
169 lines
3.6 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of GETPAGESIZE</TITLE>
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</HEAD><BODY>
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<H1>GETPAGESIZE</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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getpagesize - get memory page size
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>></B>
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<P>
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<B>int getpagesize(void);</B>
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>getpagesize</B>():
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<DL COMPACT><DT id="1"><DD>
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<DL COMPACT>
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<DT id="2">Since glibc 2.19:<DD>
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<PRE>
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_DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
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<DT id="3"></PRE>
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<DD>
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From glibc 2.12 to 2.19:
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<PRE>
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_BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
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<DT id="4"></PRE>
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<DD>
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Before glibc 2.12:
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_BSD_SOURCE || _XOPEN_SOURCE >= 500
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</DL>
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The function
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<B>getpagesize</B>()
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returns the number of bytes in a memory page,
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where "page" is a fixed-length block,
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the unit for memory allocation and file mapping performed by
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<B><A HREF="/cgi-bin/man/man2html?2+mmap">mmap</A></B>(2).
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<A NAME="lbAE"> </A>
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<H2>CONFORMING TO</H2>
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SVr4, 4.4BSD, SUSv2.
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In SUSv2 the
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<B>getpagesize</B>()
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call is labeled LEGACY, and in POSIX.1-2001
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it has been dropped;
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HP-UX does not have this call.
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<A NAME="lbAF"> </A>
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<H2>NOTES</H2>
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Portable applications should employ
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<I>sysconf(_SC_PAGESIZE)</I>
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instead of
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<B>getpagesize</B>():
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<P>
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#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>>
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long sz = sysconf(_SC_PAGESIZE);
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<P>
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(Most systems allow the synonym
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<B>_SC_PAGE_SIZE</B>
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for
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<B>_SC_PAGESIZE</B>.)
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<P>
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Whether
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<B>getpagesize</B>()
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is present as a Linux system call depends on the architecture.
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If it is, it returns the kernel symbol
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<B>PAGE_SIZE</B>,
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whose value depends on the architecture and machine model.
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Generally, one uses binaries that are dependent on the architecture but not
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on the machine model, in order to have a single binary
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distribution per architecture.
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This means that a user program
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should not find
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<B>PAGE_SIZE</B>
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at compile time from a header file,
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but use an actual system call, at least for those architectures
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(like sun4) where this dependency exists.
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Here glibc 2.0 fails because its
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<B>getpagesize</B>()
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returns a statically derived value, and does not use a system call.
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Things are OK in glibc 2.1.
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<A NAME="lbAG"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+mmap">mmap</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+sysconf">sysconf</A></B>(3)
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<A NAME="lbAH"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">CONFORMING TO</A><DD>
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<DT id="9"><A HREF="#lbAF">NOTES</A><DD>
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<DT id="10"><A HREF="#lbAG">SEE ALSO</A><DD>
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<DT id="11"><A HREF="#lbAH">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:32 GMT, March 31, 2021
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</HTML>
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