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man:epoll_create1

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 a new epoll(7) instance.  Since Linux 2.6.8, the
     size argument is ignored, but must be  greater  than  zero;  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.
 epoll_create1()
     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 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.
     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   argument
     informed  the  kernel of the number of file descriptors that the caller
     expected to add to the epoll instance.  The kernel used  this  informa-
     tion  as a hint for the amount of space to initially allocate in inter-
     nal 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  dynami-
     cally sizes the required data structures without needing the hint), but
     size must still be greater than zero, in order to ensure backward  com-
     patibility when new epoll applications are run on older kernels.

SEE ALSO

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

COLOPHON

     This  page  is  part of release 4.16 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/.

Linux 2017-09-15 EPOLL_CREATE(2)

/data/webs/external/dokuwiki/data/pages/man/epoll_create1.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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