1 EPOLL_WAIT(2) Linux Programmer's Manual EPOLL_WAIT(2) 2 3 4 5 NAME 6 epoll_wait - wait for an I/O event on an epoll file descriptor 7 8 SYNOPSIS 9 #include <sys/epoll.h> 10 11 int epoll_wait(int epfd, struct epoll_event * events, int maxevents, 12 int timeout) 13 14 DESCRIPTION 15 Wait for events on the epoll file descriptor epfd for a maximum time of 16 timeout milliseconds. The memory area pointed to by events will contain 17 the events that will be available for the caller. Up to maxevents are 18 returned by epoll_wait(2). The maxevents parameter must be greater 19 than zero. Specifying a timeout of -1 makes epoll_wait(2) wait indefi- 20 nitely, while specifying a timeout equal to zero makes epoll_wait(2) to 21 return immediately even if no events are available ( return code equal 22 to zero ). The struct epoll_event is defined as : 23 24 25 typedef union epoll_data { 26 void *ptr; 27 int fd; 28 __uint32_t u32; 29 __uint64_t u64; 30 } epoll_data_t; 31 32 struct epoll_event { 33 __uint32_t events; /* Epoll events */ 34 epoll_data_t data; /* User data variable */ 35 }; 36 37 38 The data of each returned structure will contain the same data the user 39 set with a epoll_ctl(2) (EPOLL_CTL_ADD,EPOLL_CTL_MOD) while the events 40 member will contain the returned event bit field. 41 42 RETURN VALUE 43 When successful, epoll_wait(2) returns the number of file descriptors 44 ready for the requested I/O, or zero if no file descriptor became ready 45 during the requested timeout milliseconds. When an error occurs, 46 epoll_wait(2) returns -1 and errno is set appropriately. 47 48 ERRORS 49 EBADF epfd is not a valid file descriptor. 50 51 EINVAL The supplied file descriptor, epfd, is not an epoll file 52 descriptor, or the maxevents parameter is less than or equal to 53 zero. 54 55 EFAULT The memory area pointed to by events is not accessible with 56 write permissions. 57 58 CONFORMING TO 59 epoll_wait(2) is a new API introduced in Linux kernel 2.5.44. The 60 interface should be finalized by Linux kernel 2.5.66. 61 62 SEE ALSO 63 epoll(4) epoll_create(2) epoll_ctl(2) 64 65 66 67 68 Linux 23 October 2002 EPOLL_WAIT(2) 69
