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epoll_create, epoll_create1 - open an epoll file descriptor
int epoll_create(int size);
int epoll_create1(int flags);
epoll_create() creates an epoll "instance", requesting the kernel to
allocate an event backing store dimensioned for size descriptors. The
size is not the maximum size of the backing store but just a hint to
the kernel about how to dimension internal structures. (Nowadays, size
is unused; 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
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.
Since Linux 2.6.8, the size argument is unused, but must be greater
than zero. (The kernel dynamically sizes the required data structures
without needing this initial hint.)
close(2), epoll_ctl(2), epoll_wait(2), epoll(7)
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