1 .\" Copyright (C) 2003 Davide Libenzi
2 .\" and Copyright 2008, 2009, 2012 Michael Kerrisk <tk.manpages@gmail.com>
3 .\" Davide Libenzi <davidel@xmailserver.org>
5 .\" %%%LICENSE_START(GPLv2+_SW_3_PARA)
6 .\" This program is free software; you can redistribute it and/or modify
7 .\" it under the terms of the GNU General Public License as published by
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9 .\" (at your option) any later version.
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14 .\" GNU General Public License for more details.
16 .\" You should have received a copy of the GNU General Public
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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 2021-03-22 "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.
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.
59 is 0, then, other than the fact that the obsolete
65 The following value can be included in
67 to obtain different behavior:
72 flag on the new file descriptor.
73 See the description of the
77 for reasons why this may be useful.
81 return a file descriptor (a nonnegative integer).
82 On error, \-1 is returned, and
84 is set to indicate the error.
92 .RB ( epoll_create1 ())
93 Invalid value specified in
97 The per-user limit on the number of epoll instances imposed by
98 .I /proc/sys/fs/epoll/max_user_instances
105 The per-process limit on the number of open file descriptors has been reached.
108 The system-wide limit on the total number of open files has been reached.
111 There was insufficient memory to create the kernel object.
114 was added to the kernel in version 2.6.
115 Library support is provided in glibc starting with version 2.3.2.
117 .\" To be precise: kernel 2.5.44.
118 .\" The interface should be finalized by Linux kernel 2.5.66.
120 was added to the kernel in version 2.6.27.
121 Library support is provided in glibc starting with version 2.9.
132 argument informed the kernel of the number of file descriptors
133 that the caller expected to add to the
136 The kernel used this information as a hint for the amount of
137 space to initially allocate in internal data structures describing events.
138 (If necessary, the kernel would allocate more space
139 if the caller's usage exceeded the hint given in
142 this hint is no longer required
143 (the kernel dynamically sizes the required data structures
144 without needing the hint), but
146 must still be greater than zero,
147 in order to ensure backward compatibility when new
149 applications are run on older kernels.