epoll_create, epoll_create1 — open an epoll file descriptor
epoll_create() creates an
epoll(7) instance. Since
Linux 2.6.8, the
argument is ignored, but must be greater than zero; see NOTES
epoll_create() returns a
file descriptor referring to the new epoll instance. This
file descriptor is used for all the subsequent calls to the
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.
flags is 0,
then, other than the fact that the obsolete
size argument is dropped,
epoll_create1() is the same
following value can be included in
flags to obtain different
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.
On success, these system calls return a nonnegative file
descriptor. On error, −1 is returned, and
errno is set to indicate the error.
size is not
Invalid value specified in
The per-user limit on the number of epoll instances
was encountered. See epoll(7) for further
The per-process limit on the number of open file descriptors has been reached.
The system-wide limit on the total number of open files has been reached.
There was insufficient memory to create the kernel object.
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.
In the initial
epoll_create() implementation, the
informed the kernel of the number of file descriptors that
the caller expected to add to the
epoll instance. The kernel
used this information as a hint for the amount of space to
initially allocate in internal data structures describing
events. (If necessary, the kernel would allocate more space
if the caller's usage exceeded the hint given in
size.) Nowadays, this hint is
no longer required (the kernel dynamically sizes the required
data structures without needing the hint), but
size must still be greater than
zero, in order to ensure backward compatibility when new
are run on older kernels.
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Copyright (C) 2003 Davide Libenzi
Davide Libenzi <davidelxmailserver.org>
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 manual; if not, see
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()