A set of bit flags used to specify conditions for which an input callback will be triggered. The three members of this enumeration correspond to the readfds, writefds, and exceptfds arguments to the select system call.
|The file descriptor has become available for reading. (Or, as is standard in Unix, a socket or pipe was closed at the other end; this is the case if a subsequent read on the file descriptor returns a count of zero.)
|The file descriptor has become available for writing.
|An exception was raised on the file descriptor.