1 .\" Copyright (C) 2003 Davide Libenzi
2 .\" Davide Libenzi <davidel@xmailserver.org>
4 .\" %%%LICENSE_START(GPLv2+_SW_3_PARA)
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
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8 .\" (at your option) any later version.
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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
16 .\" License along with this manual; if not, see
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20 .TH EPOLL_CTL 2 2012-04-15 "Linux" "Linux Programmer's Manual"
22 epoll_ctl \- control interface for an epoll descriptor
24 .B #include <sys/epoll.h>
26 .BI "int epoll_ctl(int " epfd ", int " op ", int " fd \
27 ", struct epoll_event *" event );
29 This system call performs control operations on the
32 referred to by the file descriptor
34 It requests that the operation
36 be performed for the target file descriptor,
44 Register the target file descriptor
48 instance referred to by the file descriptor
50 and associate the event
52 with the internal file linked to
58 associated with the target file descriptor
62 Remove (deregister) the target file descriptor
66 instance referred to by
70 is ignored and can be NULL (but see BUGS below).
74 argument describes the object linked to the file descriptor
82 typedef union epoll_data {
90 uint32_t events; /* Epoll events */
91 epoll_data_t data; /* User data variable */
98 member is a bit set composed using the following available event
102 The associated file is available for
107 The associated file is available for
111 .BR EPOLLRDHUP " (since Linux 2.6.17)"
112 Stream socket peer closed connection,
113 or shut down writing half of connection.
114 (This flag is especially useful for writing simple code to detect
115 peer shutdown when using Edge Triggered monitoring.)
118 There is urgent data available for
123 Error condition happened on the associated file descriptor.
125 will always wait for this event; it is not necessary to set it in
129 Hang up happened on the associated file descriptor.
131 will always wait for this event; it is not necessary to set it in
135 Sets the Edge Triggered behavior for the associated file descriptor.
136 The default behavior for
141 for more detailed information about Edge and Level Triggered event
142 distribution architectures.
144 .BR EPOLLONESHOT " (since Linux 2.6.2)"
145 Sets the one-shot behavior for the associated file descriptor.
146 This means that after an event is pulled out with
148 the associated file descriptor is internally disabled and no other events
149 will be reported by the
156 to rearm the file descriptor with a new event mask.
161 When an error occurs,
165 is set appropriately.
172 is not a valid file descriptor.
178 and the supplied file descriptor
180 is already registered with this epoll instance.
191 or the requested operation
193 is not supported by this interface.
203 is not registered with this epoll instance.
206 There was insufficient memory to handle the requested
212 .I /proc/sys/fs/epoll/max_user_watches
213 was encountered while trying to register
214 .RB ( EPOLL_CTL_ADD )
215 a new file descriptor on an epoll instance.
227 was added to the kernel in version 2.6.
228 .\" To be precise: kernel 2.5.44.
229 .\" The interface should be finalized by Linux kernel 2.5.66.
233 Library support is provided in glibc starting with version 2.3.2.
237 interface supports all file descriptors that support
240 In kernel versions before 2.6.9, the
242 operation required a non-null pointer in
244 even though this argument is ignored.
247 can be specified as NULL
250 Applications that need to be portable to kernels before 2.6.9
251 should specify a non-null pointer in
254 .BR epoll_create (2),
259 This page is part of release 3.67 of the Linux
262 A description of the project,
263 information about reporting bugs,
264 and the latest version of this page,
266 \%http://www.kernel.org/doc/man\-pages/.