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       epoll_create, epoll_create1 - open an epoll file descriptor


       #include <sys/epoll.h>

       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
       for reuse.

       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.

       EMFILE The per-process limit on the number of open file descriptors has
              been reached.

       ENFILE The system-wide 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)


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