mirror of https://github.com/mkerrisk/man-pages
135 lines
3.2 KiB
Groff
135 lines
3.2 KiB
Groff
.\"
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.\" epoll by Davide Libenzi ( efficient event notification retrieval )
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.\" Copyright (C) 2003 Davide Libenzi
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.\"
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.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License as published by
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.\" the Free Software Foundation; either version 2 of the License, or
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.\" (at your option) any later version.
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.\"
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.\" This program is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program; if not, write to the Free Software
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.\" Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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.\"
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.\" Davide Libenzi <davidel@xmailserver.org>
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.\"
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.\"
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.\" FIXME 2.6.19-rc5 has epoll_pwait(); this should be documented
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.\" on this page.
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.\"
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.TH EPOLL_WAIT 2 "23 October 2002" Linux "Linux Programmer's Manual"
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.SH NAME
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epoll_wait \- wait for an I/O event on an epoll file descriptor
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.SH SYNOPSIS
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.nf
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.B #include <sys/epoll.h>
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.sp
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.BI "int epoll_wait(int " epfd ", struct epoll_event *" events ,
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.BI " int " maxevents ", int " timeout);
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.fi
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.SH DESCRIPTION
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Wait for events on the
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.B epoll
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file descriptor
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.I epfd
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for a maximum time of
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.I timeout
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milliseconds.
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The memory area pointed to by
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.I events
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will contain the events that will be available for the caller.
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Up to
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.I maxevents
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are returned by
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.BR epoll_wait (2).
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The
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.I maxevents
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parameter must be greater than zero.
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Specifying a
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.I timeout
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of \-1 makes
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.BR epoll_wait (2)
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wait indefinitely, while specifying a
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.I timeout
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equal to zero makes
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.BR epoll_wait (2)
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to return immediately even if no events are available
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(return code equal to zero).
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The
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.I struct epoll_event
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is defined as :
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.sp
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.in +0.5i
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.nf
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typedef union epoll_data {
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void *ptr;
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int fd;
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__uint32_t u32;
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__uint64_t u64;
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} epoll_data_t;
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struct epoll_event {
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__uint32_t events; /* Epoll events */
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epoll_data_t data; /* User data variable */
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};
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.fi
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.in -0.5i
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The
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.I data
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of each returned structure will contain the same data the user set with a
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.BR epoll_ctl (2)
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.IR ( EPOLL_CTL_ADD , EPOLL_CTL_MOD )
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while the
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.I events
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member will contain the returned event bit field.
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.SH "RETURN VALUE"
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When successful,
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.BR epoll_wait (2)
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returns the number of file descriptors ready for the requested I/O, or zero
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if no file descriptor became ready during the requested
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.I timeout
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milliseconds.
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When an error occurs,
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.BR epoll_wait (2)
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returns \-1 and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.B EBADF
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.I epfd
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is not a valid file descriptor.
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.TP
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.B EFAULT
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The memory area pointed to by
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.I events
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is not accessible with write permissions.
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.TP
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.B EINTR
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The call was interrupted by a signal handler before any of the
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requested events occurred or the
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.I timeout
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expired.
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.TP
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.B EINVAL
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.IR epfd
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is not an
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.B epoll
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file descriptor, or
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.I maxevents
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is less than or equal to zero.
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.SH CONFORMING TO
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.BR epoll_wait (2)
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is Linux specific, and was introduced in kernel 2.5.44.
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.\" The interface should be finalized by Linux kernel 2.5.66.
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.SH "SEE ALSO"
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.BR epoll_create (2),
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.BR epoll_ctl (2),
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.BR epoll (7)
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