Originální popis anglicky:
epoll_ctl - control interface for an epoll descriptor
Návod, kniha: Linux Programmer's Manual
#include <sys/epoll.h>
int epoll_ctl(int epfd
, int op
, int fd
, struct
epoll_event *event
)
Control an
epoll descriptor,
epfd, by requesting the operation
op be performed on the target file descriptor,
fd. The
event describes the object linked to the file descriptor
fd. 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
events member is a bit set composed using the following available
event types :
- EPOLLIN
- The associated file is available for read(2)
operations.
- EPOLLOUT
- The associated file is available for write(2)
operations.
- EPOLLPRI
- There is urgent data available for read(2)
operations.
- EPOLLERR
- Error condition happened on the associated file
descriptor.
- EPOLLHUP
- Hang up happened on the associated file descriptor.
- EPOLLET
- Sets the Edge Triggered behaviour for the associated file
descriptor. The default behaviour for epoll is Level Triggered. See
epoll(4) for more detailed informations about Edge and Level
Triggered event distribution architectures.
- EPOLLONESHOT
- Sets the One-Shot behaviour for the associated file
descriptor. It means that after an event is pulled out with
epoll_wait(2) the associated file descriptor is internally disabled
and no other events will be reported by the epoll interface. The
user must call epoll_ctl(2) with EPOLL_CTL_MOD to re-enable
the file descriptor with a new event mask.
The
epoll interface supports all file descriptors that support
poll(2). Valid values for the
op parameter are :
- EPOLL_CTL_ADD
- Add the target file descriptor fd to the
epoll descriptor epfd and associate the event event
with the internal file linked to fd.
- EPOLL_CTL_MOD
- Change the event event associated to the target file
descriptor fd.
- EPOLL_CTL_DEL
- Remove the target file descriptor fd from the
epoll file descriptor, epfd.
When successful,
epoll_ctl(2) returns zero. When an error occurs,
epoll_ctl(2) returns -1 and
errno is set appropriately.
- EBADF
- The epfd file descriptor is not a valid file
descriptor.
- EINVAL
- The supplied file descriptor, epfd, is not an
epoll file descriptor, or the requested operation op is not
supported by this interface.
- ENOMEM
- There was insufficient memory to handle the requested
op control operation.
- EPERM
- The target file fd is not supported by
epoll.
epoll_ctl(2) is a new API introduced in Linux kernel 2.5.44. The
interface should be finalized by Linux kernel 2.5.66.
epoll_create(2),
epoll_wait(2),
epoll(4)
