1 EPOLL_CTL(2) Linux Programmer's Manual EPOLL_CTL(2) 2 3 4 5 NAME 6 epoll_ctl - control interface for an epoll descriptor 7 8 SYNOPSIS 9 #include <sys/epoll.h> 10 11 int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event) 12 13 DESCRIPTION 14 Control an epoll descriptor, epfd, by requesting the operation op be 15 performed on the target file descriptor, fd. The event describes the 16 object linked to the file descriptor fd. The struct epoll_event is 17 defined as : 18 19 20 typedef union epoll_data { 21 void *ptr; 22 int fd; 23 __uint32_t u32; 24 __uint64_t u64; 25 } epoll_data_t; 26 27 struct epoll_event { 28 __uint32_t events; /* Epoll events */ 29 epoll_data_t data; /* User data variable */ 30 }; 31 32 33 The events member is a bit set composed using the following available 34 event types : 35 36 EPOLLIN 37 The associated file is available for read(2) operations. 38 39 EPOLLOUT 40 The associated file is available for write(2) operations. 41 42 EPOLLPRI 43 There is urgent data available for read(2) operations. 44 45 EPOLLERR 46 Error condition happened on the associated file descriptor. 47 48 EPOLLHUP 49 Hang up happened on the associated file descriptor. 50 51 EPOLLET 52 Sets the Edge Triggered behaviour for the associated file 53 descriptor. The default behaviour for epoll is Level Triggered. 54 See epoll(4) for more detailed informations about Edge and Level 55 Triggered event distribution architectures. 56 57 EPOLLONESHOT 58 Sets the One-Shot behaviour for the associated file descriptor. 59 It means that after an event is pulled out with epoll_wait(2) 60 the associated file descriptor is internally disabled and no 61 other events will be reported by the epoll interface. The user 62 must call epoll_ctl(2) with EPOLL_CTL_MOD to re-enable the file 63 descriptor with a new event mask. 64 65 66 The epoll interface supports all file descriptors that support poll(2). 67 Valid values for the op parameter are : 68 69 EPOLL_CTL_ADD 70 Add the target file descriptor fd to the epoll descriptor epfd 71 and associate the event event with the internal file linked to 72 fd. 73 74 EPOLL_CTL_MOD 75 Change the event event associated to the target file descriptor 76 fd. 77 78 EPOLL_CTL_DEL 79 Remove the target file descriptor fd from the epoll file 80 descriptor, epfd. 81 82 RETURN VALUE 83 When successful, epoll_ctl(2) returns zero. When an error occurs, 84 epoll_ctl(2) returns -1 and errno is set appropriately. 85 86 ERRORS 87 EBADF The epfd file descriptor is not a valid file descriptor. 88 89 EPERM The target file fd is not supported by epoll. 90 91 EINVAL The supplied file descriptor, epfd, is not an epoll file 92 descriptor, or the requested operation op is not supported by 93 this interface. 94 95 ENOMEM There was insufficient memory to handle the requested op control 96 operation. 97 98 CONFORMING TO 99 epoll_ctl(2) is a new API introduced in Linux kernel 2.5.44. The 100 interface should be finalized by Linux kernel 2.5.66. 101 102 SEE ALSO 103 epoll(4) epoll_create(2) epoll_wait(2) 104 105 106 107 108 Linux 23 October 2002 EPOLL_CTL(2) 109
