242 lines
5.4 KiB
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242 lines
5.4 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 EPOLL_CREATE</TITLE>
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</HEAD><BODY>
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<H1>EPOLL_CREATE</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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epoll_create, epoll_create1 - open an epoll file descriptor
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/sys/epoll.h">sys/epoll.h</A>></B>
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<B>int epoll_create(int </B><I>size</I><B>);</B>
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<B>int epoll_create1(int </B><I>flags</I><B>);</B>
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>epoll_create</B>()
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creates a new
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<B><A HREF="/cgi-bin/man/man2html?7+epoll">epoll</A></B>(7)
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instance.
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Since Linux 2.6.8, the
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<I>size</I>
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argument is ignored, but must be greater than zero; see NOTES below.
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<P>
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<B>epoll_create</B>()
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returns a file descriptor referring to the new epoll instance.
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This file descriptor is used for all the subsequent calls to the
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<B>epoll</B>
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interface.
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When no longer required, the file descriptor returned by
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<B>epoll_create</B>()
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should be closed by using
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<B><A HREF="/cgi-bin/man/man2html?2+close">close</A></B>(2).
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When all file descriptors referring to an epoll instance have been closed,
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the kernel destroys the instance
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and releases the associated resources for reuse.
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<A NAME="lbAE"> </A>
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<H3>epoll_create1()</H3>
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If
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<I>flags</I>
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is 0, then, other than the fact that the obsolete
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<I>size</I>
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argument is dropped,
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<B>epoll_create1</B>()
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is the same as
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<B>epoll_create</B>().
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The following value can be included in
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<I>flags</I>
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to obtain different behavior:
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<DL COMPACT>
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<DT id="1"><B>EPOLL_CLOEXEC</B>
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<DD>
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Set the close-on-exec
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(<B>FD_CLOEXEC</B>)
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flag on the new file descriptor.
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See the description of the
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<B>O_CLOEXEC</B>
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flag in
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2)
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for reasons why this may be useful.
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</DL>
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<A NAME="lbAF"> </A>
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<H2>RETURN VALUE</H2>
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On success,
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these system calls
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return a nonnegative file descriptor.
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On error, -1 is returned, and
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<I>errno</I>
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is set to indicate the error.
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<A NAME="lbAG"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="2"><B>EINVAL</B>
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<DD>
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<I>size</I>
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is not positive.
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<DT id="3"><B>EINVAL</B>
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<DD>
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(<B>epoll_create1</B>())
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Invalid value specified in
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<I>flags</I>.
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<DT id="4"><B>EMFILE</B>
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<DD>
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The per-user limit on the number of epoll instances imposed by
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<I>/proc/sys/fs/epoll/max_user_instances</I>
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was encountered.
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See
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<B><A HREF="/cgi-bin/man/man2html?7+epoll">epoll</A></B>(7)
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for further details.
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<DT id="5"><B>EMFILE</B>
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<DD>
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The per-process limit on the number of open file descriptors has been reached.
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<DT id="6"><B>ENFILE</B>
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<DD>
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The system-wide limit on the total number of open files has been reached.
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<DT id="7"><B>ENOMEM</B>
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<DD>
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There was insufficient memory to create the kernel object.
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</DL>
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<A NAME="lbAH"> </A>
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<H2>VERSIONS</H2>
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<B>epoll_create</B>()
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was added to the kernel in version 2.6.
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Library support is provided in glibc starting with version 2.3.2.
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<P>
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<B>epoll_create1</B>()
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was added to the kernel in version 2.6.27.
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Library support is provided in glibc starting with version 2.9.
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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<B>epoll_create</B>()
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is Linux-specific.
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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In the initial
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<B>epoll_create</B>()
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implementation, the
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<I>size</I>
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argument informed the kernel of the number of file descriptors
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that the caller expected to add to the
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<B>epoll</B>
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instance.
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The kernel used this information as a hint for the amount of
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space to initially allocate in internal data structures describing events.
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(If necessary, the kernel would allocate more space
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if the caller's usage exceeded the hint given in
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<I>size</I>.)
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Nowadays,
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this hint is no longer required
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(the kernel dynamically sizes the required data structures
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without needing the hint), but
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<I>size</I>
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must still be greater than zero,
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in order to ensure backward compatibility when new
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<B>epoll</B>
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applications are run on older kernels.
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<A NAME="lbAK"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+close">close</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+epoll_ctl">epoll_ctl</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+epoll_wait">epoll_wait</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+epoll">epoll</A></B>(7)
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<A NAME="lbAL"> </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="8"><A HREF="#lbAB">NAME</A><DD>
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<DT id="9"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="10"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="11"><A HREF="#lbAE">epoll_create1()</A><DD>
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</DL>
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<DT id="12"><A HREF="#lbAF">RETURN VALUE</A><DD>
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<DT id="13"><A HREF="#lbAG">ERRORS</A><DD>
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<DT id="14"><A HREF="#lbAH">VERSIONS</A><DD>
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<DT id="15"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="16"><A HREF="#lbAJ">NOTES</A><DD>
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<DT id="17"><A HREF="#lbAK">SEE ALSO</A><DD>
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<DT id="18"><A HREF="#lbAL">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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</BODY>
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</HTML>
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