File and device input/output

STREAMS mechanism

This section shows how to construct, use, and dismantle a Stream using STREAMS-related systems calls. General and STREAMS-specific system calls provide the user level facilities required to implement application programs. This system call interface is upwardly compatible with the traditional character I/O facilities. The open system call recognizes a STREAMS file and creates a Stream to the specified driver. A user process can receive and send data on STREAMS files using read and write in the same way as with traditional character files. The ioctl system call enables users to perform functions specific to a particular device. STREAMS ioctl commands (see streamio(7)) support a variety of functions for accessing and controlling Streams. The last close in a Stream dismantles a Stream.

In addition to the traditional ioctl commands and system calls, there are other system calls used by STREAMS. The poll system call enables a user to poll multiple Streams for various events. The putmsg and getmsg system calls enable users to send and receive STREAMS messages, and are suitable for interacting with STREAMS modules and drivers through a service interface.

STREAMS provides kernel facilities and utilities to support development of modules and drivers. The Stream head handles most system calls so that the related processing does not have to be incorporated in a module or driver.

Next topic: STREAMS system calls
Previous topic: Module reusability

© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 27 April 2004