PollEvents

There is data to read.

Writing is now possible, though a write larger that the available space in a socket or pipe will still block (unless O_NONBLOCK is set).

There is some exceptional condition on the file descriptor. Possibilities include:

* There is out-of-band data on a TCP socket (see tcp(7)). * A pseudoterminal master in packet mode has seen a state change on the slave (see ioctl_tty(2)). * A cgroup.events file has been modified (see cgroups(7)).

Error condition (only returned in revents; ignored in events). * This bit is also set for a file descriptor referring to the * write end of a pipe when the read end has been closed.

Invalid request: fd not open (only returned in revents; ignored in events).

Equivalent to POLLIN.

Priority band data can be read (generally unused on Linux).

Equivalent to POLLOUT.

Priority data may be written.

Hang up (only returned in revents; ignored in events). Note that when reading from a channel such as a pipe or a stream socket, this event merely indicates that the peer closed its end of the channel. Subsequent reads from the channel will return 0 (end of file) only after all outstanding data in the channel has been consumed.