Name
epoll_ctl — control interface for an epoll
descriptor
Synopsis
#include <sys/epoll.h>
int
epoll_ctl( |
int |
epfd, |
| |
int |
op, |
| |
int |
fd, |
| |
struct epoll_event
* |
event); |
DESCRIPTION
Control an epoll
descriptor, epfd, by
requesting that the operation op be performed on the target
file descriptor, fd.
The event describes
the object linked to the file descriptor fd. The struct epoll_event is defined as
:
| typedef |
union epoll_data { |
| |
void |
* |
ptr; |
|
| |
int |
|
fd; |
|
| |
__uint32_t |
|
u32; |
|
| |
__uint64_t |
|
u64; |
|
| } epoll_data_t; |
|
| struct |
epoll_event { |
| |
__uint32_t |
|
events; |
/* Epoll events */ |
| |
epoll_data_t |
|
data; |
/* User data variable */ |
| }; |
The events
member is a bit set composed using the following available
event types :
EPOLLIN-
The associated file is available for read(2)
operations.
EPOLLOUT-
The associated file is available for write(2)
operations.
EPOLLRDHUP (since kernel
2.6.17)-
Stream socket peer closed connection, or shut down
writing half of connection. (This flag is especially
useful for writing simple code to detect peer shutdown
when using Edge Triggered monitoring.)
EPOLLPRI-
There is urgent data available for read(2)
operations.
EPOLLERR-
Error condition happened on the associated file
descriptor. epoll_wait(2) will
always wait for this event; it is not necessary to set
it in events.
EPOLLHUP-
Hang up happened on the associated file descriptor.
epoll_wait(2) will
always wait for this event; it is not necessary to set
it in events.
EPOLLET-
Sets the Edge Triggered behaviour for the associated
file descriptor. The default behaviour for epoll is Level
Triggered. See epoll(7) for more
detailed information about Edge and Level Triggered
event distribution architectures.
EPOLLONESHOT (since kernel
2.6.2)-
Sets the one-shot behaviour for the associated file
descriptor. This means that after an event is pulled
out with epoll_wait(2) the
associated file descriptor is internally disabled and
no other events will be reported by the epoll interface. The
user must call epoll_ctl(2) with
EPOLL_CTL_MOD to
re-enable the file descriptor with a new event
mask.
The epoll
interface supports all file descriptors that support poll(2). Valid values for
the op parameter are
:
EPOLL_CTL_ADD-
Add the target file descriptor fd to the epoll descriptor
epfd and
associate the event event with the
internal file linked to fd.
EPOLL_CTL_MOD-
Change the event event associated with
the target file descriptor fd.
EPOLL_CTL_DEL-
Remove the target file descriptor fd from the
epoll
file descriptor, epfd. The event is ignored and
can be NULL (but see BUGS below).
RETURN VALUE
When successful, epoll_ctl(2) returns zero.
When an error occurs, epoll_ctl(2) returns
−1 and errno is set
appropriately.
ERRORS
- EBADF
-
epfd or
fd is not a
valid file descriptor.
- EEXIST
-
op was
EPOLL_CTL_ADD, and the supplied file descriptor
fd is already
in epfd.
- EINVAL
-
epfd is not
an epoll file
descriptor, or fd is the same as
epfd, or the
requested operation op is not supported by
this interface.
- ENOENT
-
op was
EPOLL_CTL_MOD or EPOLL_CTL_DEL, and fd is not in epfd.
- ENOMEM
-
There was insufficient memory to handle the
requested op
control operation.
- EPERM
-
The target file fd does not support
epoll.
CONFORMING TO
epoll_ctl(2) is Linux
specific, and was introduced in kernel 2.5.44.
BUGS
In kernel versions before 2.6.9, the EPOLL_CTL_DEL operation required a non-NULL
pointer in event,
even though this argument is ignored. Since kernel 2.6.9,
event can be
specified as NULL when using EPOLL_CTL_DEL.
SEE ALSO
epoll_create(2), epoll_wait(2), poll(2), epoll(7)
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 <davidel@xmailserver.org>
|
