epoll_create, epoll_create1 - open an epoll file descriptor
int epoll_create(int size);
int epoll_create1(int flags);
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.
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
flags to obtain different behavior:
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 file descriptor (a
nonnegative integer). On error, -1 is returned, and
set to indicate the error.
size is not positive.
(epoll_create1()) Invalid value specified in
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.
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.
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
size must still be greater than zero, in order to
ensure backward compatibility when new epoll
applications are run on older kernels.
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