Name

epoll_create, epoll_create1 — open an epoll file descriptor

Synopsis

#include <sys/epoll.h>
int epoll_create( int size);
 
int epoll_create1( int flags);
 

DESCRIPTION

epoll_create() creates an epoll "instance", requesting the kernel to allocate an event backing store dimensioned for size descriptors. The size is not the maximum size of the backing store but just a hint to the kernel about how to dimension internal structures. (Nowadays, size is unused; see NOTES below.)

epoll_create() returns a file descriptor referring to the new epoll instance. This file descriptor is used for all the subsequent calls to the epoll interface. When no longer required, the file descriptor returned by epoll_create() should be closed by using close(2). When all file descriptors referring to an epoll instance have been closed, the kernel destroys the instance and releases the associated resources for reuse.

If flags is 0, then, other than the fact that the obsolete size argument is dropped, epoll_create1() is the same as epoll_create(). The following value can be included in flags to obtain different behavior:

EPOLL_CLOEXEC

Set the close-on-exec (FD_CLOEXEC) flag on the new file descriptor. See the description of the O_CLOEXEC flag in open(2) for reasons why this may be useful.

RETURN VALUE

On success, these system calls return a nonnegative file descriptor. On error, −1 is returned, and errno is set to indicate the error.

ERRORS

EINVAL

size is not positive.

EINVAL

(epoll_create1()) Invalid value specified in flags.

EMFILE

The per-user limit on the number of epoll instances imposed by /proc/sys/fs/epoll/max_user_instances was encountered. See epoll(7) for further details.

ENFILE

The system limit on the total number of open files has been reached.

ENOMEM

There was insufficient memory to create the kernel object.

VERSIONS

epoll_create() was added to the kernel in version 2.6. Library support is provided in glibc starting with version 2.3.2.

epoll_create1() was added to the kernel in version 2.6.27. Library support is provided in glibc starting with version 2.9.

CONFORMING TO

epoll_create() is Linux-specific.

NOTES

Since Linux 2.6.8, the size argument is unused, but must be greater than zero. (The kernel dynamically sizes the required data structures without needing this initial hint.)

SEE ALSO

close(2), epoll_ctl(2), epoll_wait(2), epoll(7)

COLOPHON

This page is part of release 3.33 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man-pages/.


 epoll by Davide Libenzi ( efficient event notification retrieval )
 Copyright (C) 2003  Davide Libenzi

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 Davide Libenzi <davidelxmailserver.org>

Modified 2004-06-17 by Michael Kerrisk <mtk.manpagesgmail.com>
Modified 2005-04-04 by Marko Kohtala <marko.kohtalagmail.com>
2008-10-10, mtk: add description of epoll_create1()