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A bitwise combination representing an I/O condition to watch for on an event source. 
 
The flags correspond to those used by the poll()system call on UNIX (seeman 2 poll). To test for individual flags, do something like this: Bitwise operators:IOCondition operator|(IOCondition, IOCondition)
 IOCondition operator&(IOCondition, IOCondition)
 IOCondition operator^(IOCondition, IOCondition)
 IOCondition operator~(IOCondition)
 IOCondition& operator|=(IOCondition&, IOCondition)
 IOCondition& operator&=(IOCondition&, IOCondition)
 IOCondition& operator^=(IOCondition&, IOCondition)
 Enumerator: 
| IO_IN | There is data to read. |  | IO_OUT | Data can be written (without blocking). |  | IO_PRI | There is urgent data to read. |  | IO_ERR | Error condition. |  | IO_HUP | Hung up (the connection has been broken, usually for pipes and sockets). |  | IO_NVAL | Invalid request. The file descriptor is not open. | 
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