Checks if a message of a particular band is on the stream-head read queue.
The I_CKBAND operation checks to see if a message of a given priority band exists on the stream-head read queue. The arg parameter is an integer containing the value of the priority band being searched for.
The I_CKBAND operation returns a value of 1 if a message of the given band exists. Otherwise, it returns a value of -1.
If unsuccessful, the errno global variable is set to the following value:
| EINVAL | The value in the arg parameter is not valid. |
This operation is part of STREAMS Kernel Extensions.
The streamio operations.
Understanding STREAMS Messages in AIX Version 4.3 Communications Programming Concepts.