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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
EPOLL_CREATE(2) Linux Programmer's Manual EPOLL_CREATE(2)
epoll_create, epoll_create1 - open an epoll file descriptor
#include <sys/epoll.h>
int epoll_create(int size);
int epoll_create1(int flags);
epoll_create() creates a new epoll(7) instance. Since Linux 2.6.8,
the size argument is ignored, but must be greater than zero; see
NOTES below.
epoll_create() returns a file descriptor referring to the new epoll
instance. This file descriptor is used for all the subsequent calls
to the epoll interface. 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.
epoll_create1()
If flags is 0, then, other than the fact that the obsolete size
argument is dropped, epoll_create1() is the same as epoll_create().
The following value can be included in flags to obtain different
behavior:
EPOLL_CLOEXEC
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.
EINVAL size is not positive.
EINVAL (epoll_create1()) Invalid value specified in flags.
EMFILE The per-user limit on the number of epoll instances imposed by
/proc/sys/fs/epoll/max_user_instances was encountered. See
epoll(7) for further details.
EMFILE The per-process limit on the number of open file descriptors
has been reached.
ENFILE The system-wide limit on the total number of open files has
been reached.
ENOMEM 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.
epoll_create() is Linux-specific.
In the initial epoll_create() implementation, the size argument
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 epoll applications are run on
older kernels.
close(2), epoll_ctl(2), epoll_wait(2), epoll(7)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2015-12-28 EPOLL_CREATE(2)
Pages that refer to this page: epoll_ctl(2), epoll_wait(2), syscalls(2), proc(5), epoll(7)