EPOLL_WAIT - phpMan

EPOLL_WAIT(2)              Linux Programmer’s Manual             EPOLL_WAIT(2)



NAME
       epoll_wait - wait for an I/O event on an epoll file descriptor

SYNOPSIS
       #include <sys/epoll.h>

       int epoll_wait(int epfd, struct epoll_event * events, int maxevents, int timeout)

DESCRIPTION
       Wait  for  events  on  the epoll file descriptor epfd for a maximum time of timeout
       milliseconds. The memory area pointed to by events will  contain  the  events  that
       will  be  available for the caller.  Up to maxevents are returned by epoll_wait(2).
       The maxevents parameter must be greater than zero. Specifying a timeout of -1 makes
       epoll_wait(2)  wait  indefinitely,  while  specifying a timeout equal to zero makes
       epoll_wait(2) to return immediately even if no events are available (  return  code
       equal to zero ).  The struct epoll_event is defined as :


            typedef union epoll_data {
                 void *ptr;
                 int fd;
                 __uint32_t u32;
                 __uint64_t u64;
            } epoll_data_t;

            struct epoll_event {
                 __uint32_t events;  /* Epoll events */
                 epoll_data_t data;  /* User data variable */
            };


       The  data of each returned structure will contain the same data the user set with a
       epoll_ctl(2) (EPOLL_CTL_ADD,EPOLL_CTL_MOD) while the events member will contain the
       returned event bit field.

RETURN VALUE
       When successful, epoll_wait(2) returns the number of file descriptors ready for the
       requested I/O, or zero if no file descriptor  became  ready  during  the  requested
       timeout  milliseconds.  When an error occurs, epoll_wait(2) returns -1 and errno is
       set appropriately.

ERRORS
       EBADF  epfd is not a valid file descriptor.

       EINVAL The supplied file descriptor, epfd, is not an epoll file descriptor, or  the
              maxevents parameter is less than or equal to zero.

       EFAULT The  memory  area  pointed to by events is not accessible with write permis-
              sions.

CONFORMING TO
       epoll_wait(2) is a new API introduced in Linux kernel 2.5.44.  The interface should
       be finalized by Linux kernel 2.5.66.

SEE ALSO
       epoll_ctl(2), epoll_create(2), epoll(4)




Linux                           23 October 2002                  EPOLL_WAIT(2)

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