EPOLL_CREATE(2)           (2020-04-11)            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 a new 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 descrip-
          tors referring to an epoll instance have been closed, the
          kernel destroys the instance and releases the associated
          resources for reuse.

        epoll_create1()
          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 file descriptor (a
          nonnegative integer).  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.

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     EPOLL_CREATE(2)           (2020-04-11)            EPOLL_CREATE(2)

          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 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
          In the initial epoll_create() implementation, the size argu-
          ment 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 need-
          ing the hint), but size must still be greater than zero, in
          order to ensure backward compatibility when new epoll appli-
          cations are run on older kernels.

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

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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