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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);

DESCRIPTION
       epoll_create()  creates  an  epoll  "instance", requesting the kernel to allocate an event backing store dimen-
       sioned for size descriptors.  The size is not the maximum size of the backing store but just a hint to the ker-
       nel 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 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.

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 TO
       epoll_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 dynamically sizes  the  required  data  structures
       without needing this initial hint.)

SEE ALSO
       close(2), epoll_ctl(2), epoll_wait(2), epoll(7)

COLOPHON
       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2009-01-17                   EPOLL_CREATE(2)