A stream is an I/O pipeline through which serial data passes between the HP-UX operating system and a kernel driver associated with a raw (character-mode) device file and corresponding device such as a terminal or pty. One or more streams modules can be "plugged" or inserted into the stream to perform various functions such as data encryption or compression, character or message translation, attaching information to data packets, adding protocol data to the message, etc.).
Each module in the stream performs a specific task on or associated with the data being transmitted through the pipe, and multiple modules can be pushed onto a given stream. The configurable kernel parameters for streams are used to manage the resources allocated for or consumed by character-mode I/O streams and to help prevent inappropriate pushing or other streams behaviors.
For more information about streams and streams programming, refer to the STREAMS/UX for the HP 9000 Reference Manual.
Note that streams I/O pipes are not the same as conventional HP-UX and UNIX file-system pipelines.