epoll_create, epoll_create1 - open an epoll file descriptor
int epoll_create(int size);
int epoll_create1(int flags);
epoll_create() creates an epoll(7) instance. Since Linux 2.6.8, the
size 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 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
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
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.
ENFILE The system limit on the total number of open files has been
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
close(2), epoll_ctl(2), epoll_wait(2), epoll(7)
This page is part of release 3.65 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.