epoll_data(3type)

epoll event

distropkg manpages-dev@6.9.1-1dataset 2026-04-01T06:19:02Z+debian+ec4110e+mandoc:1.14.6-4

Synopsis

#include <sys/epoll.h>
struct epoll_event {
    uint32_t      events;
  /* Epoll events */
    epoll_data_t  data;
    /* User data variable */
};
union epoll_data {
    void     *ptr;
    int       fd;
    uint32_t  u32;
    uint64_t  u64;
};
typedef union epoll_data  epoll_data_t;

—

NAME

epoll_event, epoll_data, epoll_data_t - epoll event

LIBRARY

Standard C library (libc)

SYNOPSIS

bash

#include <sys/epoll.h>

bash

struct epoll_event {\n
\n    uint32_t      events;\n  /* Epoll events */
\n    epoll_data_t  data;\n    /* User data variable */
\n};

bash

union epoll_data {\n
\n    void     *ptr;\n
\n    int       fd;\n
\n    uint32_t  u32;\n
\n    uint64_t  u64;\n
\n};

bash

typedef union epoll_data  epoll_data_t;\n

DESCRIPTION

The epoll_event structure specifies data that the kernel should save and return when the corresponding file descriptor becomes ready.

VERSIONS

C library/kernel differences

The Linux kernel headers also provide this type, with a slightly different definition:

bash

#include <linux/eventpoll.h>
struct epoll_event {
\n
    __poll_t  events;
\n
    __u64     data;
};

STANDARDS

Linux.