2 .\" epoll by Davide Libenzi ( efficient event notification retrieval )
3 .\" Copyright (C) 2003 Davide Libenzi
5 .\" This program is free software; you can redistribute it and/or modify
6 .\" it under the terms of the GNU General Public License as published by
7 .\" the Free Software Foundation; either version 2 of the License, or
8 .\" (at your option) any later version.
10 .\" This program is distributed in the hope that it will be useful,
11 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
12 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 .\" GNU General Public License for more details.
15 .\" You should have received a copy of the GNU General Public License
16 .\" along with this program; if not, write to the Free Software
17 .\" Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 .\" Davide Libenzi <davidel@xmailserver.org>
21 .\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com>
22 .\" Modified 2005-04-04 by Marko Kohtala <marko.kohtala@gmail.com>
23 .\" 2008-10-10, mtk: add description of epoll_create1()
25 .TH EPOLL_CREATE 2 2012-04-15 "Linux" "Linux Programmer's Manual"
27 epoll_create, epoll_create1 \- open an epoll file descriptor
30 .B #include <sys/epoll.h>
32 .BI "int epoll_create(int " size );
33 .BI "int epoll_create1(int " flags );
40 Since Linux 2.6.8, the
42 argument is ignored, but must be greater than zero; see NOTES below.
45 returns a file descriptor referring to the new epoll instance.
46 This file descriptor is used for all the subsequent calls to the
49 When no longer required, the file descriptor returned by
51 should be closed by using
53 When all file descriptors referring to an epoll instance have been closed,
54 the kernel destroys the instance
55 and releases the associated resources for reuse.
60 is 0, then, other than the fact that the obsolete
66 The following value can be included in
68 to obtain different behavior:
73 flag on the new file descriptor.
74 See the description of the
78 for reasons why this may be useful.
82 return a nonnegative file descriptor.
83 On error, \-1 is returned, and
85 is set to indicate the error.
93 .RB ( epoll_create1 ())
94 Invalid value specified in
98 The per-user limit on the number of epoll instances imposed by
99 .I /proc/sys/fs/epoll/max_user_instances
106 The system limit on the total number of open files has been reached.
109 There was insufficient memory to create the kernel object.
112 was added to the kernel in version 2.6.
113 Library support is provided in glibc starting with version 2.3.2.
115 .\" To be precise: kernel 2.5.44.
116 .\" The interface should be finalized by Linux kernel 2.5.66.
118 was added to the kernel in version 2.6.27.
119 Library support is provided in glibc starting with version 2.9.
128 argument informed the kernel of the number of file descriptors
129 that the caller expected to add to the
132 The kernel used this information as a hint for the amount of
133 space to initially allocate in internal data structures describing events.
134 (If necessary, the kernel would allocate more space
135 if the caller's usage exceeded the hint given in
138 this hint is no longer required
139 (the kernel dynamically sizes the required data structures
140 without needing the hint), but
142 must still be greater than zero,
143 in order to ensure backward compatibility when new
145 applications are run on older kernels.