Checks to see if a message is marked.
The I_ATMARK operation shows the user if the current message on the stream-head read queue is marked by a downstream module. The arg parameter determines how the checking is done when there are multiple marked messages on the stream-head read queue. The possible values for the arg parameter are:
| ANYMARK | Read to determine if the message is marked by a downstream module. |
| LASTMARK | Read to determine if the message is the last one marked on the queue by a downstream module. |
The I_ATMARK operation returns a value of 1 if the mark condition is satisfied. Otherwise, it returns a value of 0.
If unsuccessful, the errno global variable is set to the following value:
| EINVAL | The value of the arg parameter could not be used. |
This operation is part of STREAMS Kernel Extensions.
The streamio operations.
Understanding STREAMS Messages in AIX Version 4.3 Communications Programming Concepts.