JavaScript is required to for searching.
Skip Navigation Links
Exit Print View
STREAMS Programming Guide
search filter icon
search icon

Document Information


Part I Application Programming Interface

1.  Overview of STREAMS

2.  STREAMS Application-Level Components

STREAMS Interfaces

STREAMS System Calls

Action Summary

Opening a STREAMS Device File

Initializing Details

Queue Allocation

Adding and Removing Modules

Closing the Stream

Stream Construction Example

Inserting Modules

Module and Driver Control

3.  STREAMS Application-Level Mechanisms

4.  Application Access to the STREAMS Driver and Module Interfaces

5.  STREAMS Administration

6.  Pipes and Queues

Part II Kernel Interface

7.  STREAMS Framework - Kernel Level

8.  STREAMS Kernel-Level Mechanisms

9.  STREAMS Drivers

10.  STREAMS Modules

11.  Configuring STREAMS Drivers and Modules

12.  Multithreaded STREAMS

13.  STREAMS Multiplex Drivers

Part III Advanced Topics

14.  Debugging STREAMS-based Applications

Part IV Appendixes

A.  Message Types

B.  Kernel Utility Interface Summary

C.  STREAMS-Based Terminal Subsystem




STREAMS Interfaces

The stream head provides the interface between the stream and an application program. After a stream has been opened, STREAMS-related system calls enable a user process to insert and delete (push and pop) modules. That process can then communicate with and control the operation of the stream head, 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.

STREAMS System Calls

Table 2-1 offers an overview of some basic STREAMS-related system calls.

Table 2-1 Summary of Basic STREAMS-related System Calls

Opens a stream
Closes a stream
Reads data from a stream
Writes data to a stream
Controls a stream
Receives a message at the stream head
Receives a priority message at the stream head
Sends a message downstream
Sends a priority message downstream
Identifies files on which a user can send or receive messages, or on which certain events have occurred (not restricted to STREAMS, although historically it was)
Creates a bidirectional channel that provides a communication path between multiple processes

Note - Sections 1, 2, 3, 7, and 9 of the online manual pages (man pages) contain all the STREAMS information.

Action Summary

The open(2) system call recognizes a STREAMS special file and creates a stream to the specified driver. A user process can receive and send data on STREAMS files using read(2) and write(2) in the same way as with traditional character files. ioctl(2) lets users perform functions specific to a particular device. STREAMS ioctl(2) commands (see the streamio(7I) man page) support a variety of functions to access and control streams. The final close(2) on a stream dismantles it.

The poll(2) system call provides a mechanism for multiplexing input/output over a set of file descriptors that reference open files. putmsg(2) and getmsg(2) and the putpmsg(2) and getpmsg(2) send and receive STREAMS messages, and can act on STREAMS modules and drivers through a service interface.