EPOLL_CREATE(2) Linux Programmer's Manual EPOLL_CREATE(2)NAME
epoll_create, epoll_create1 - open an epoll file descriptor
SYNOPSIS
#include <sys/epoll.h>
int epoll_create(int size);
int epoll_create1(int flags);
DESCRIPTIONepoll_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 ignored; 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 re-use.
If flags is 0, then, other than the fact that the obsolete size argu‐
ment 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 descrip‐
tor. See the description of the O_CLOEXEC flag in open(2) for
reasons why this may be useful.
RETURN VALUE
On success, these system calls return a non-negative file descriptor.
On error, -1 is returned, and errno is set to indicate the error.
ERRORS
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
reached.
ENOMEM There was insufficient memory to create the kernel object.
CONFORMING TOepoll_create() is Linux-specific, and was introduced in kernel 2.5.44.
NOTES
Since Linux 2.6.8, the size argument is unused. (The kernel dynami‐
cally sizes the required data structures without needing this initial
hint.)
SEE ALSOclose(2), epoll_ctl(2), epoll_wait(2), epoll(7)COLOPHON
This page is part of release 3.23 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/.
Linux 2009-01-17 EPOLL_CREATE(2)
