I_ATMARK streamio Operation

Purpose

Checks to see if a message is marked.

Description

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:

Value Description
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.

This operation is part of STREAMS Kernel Extensions.

Error Codes

If unsuccessful, the errno global variable is set to the following value:

Value Description
EINVAL The value of the arg parameter could not be used.