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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 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
       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
       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  nonnegative  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.

VERSIONS

       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.

CONFORMING TO

       epoll_create() is Linux-specific.

NOTES

       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.)

SEE ALSO

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

COLOPHON

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