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Technical Reference: Base Operating System and Extensions, Volume 1

cfgetospeed, cfsetospeed, cfgetispeed, or cfsetispeed Subroutine

Purpose

Gets and sets input and output baud rates.

Library

Standard C Library (libc.a)

Syntax

#include <termios.h>


speed_t cfgetospeed ( TermiosPointer)
const struct termios *TermiosPointer;


int cfsetospeed (TermiosPointer, Speed)
struct termios *TermiosPointer;
speed_t Speed;

speed_t cfgetispeed (TermiosPointer)
const struct termios *TermiosPointer;

int cfsetispeed (TermiosPointer, Speed)
struct termios *TermiosPointer;
speed_t Speed;

Description

The baud rate subroutines are provided for getting and setting the values of the input and output baud rates in the termios structure. The effects on the terminal device described below do not become effective and not all errors are detected until the tcsetattr function is successfully called.

The input and output baud rates are stored in the termios structure. The supported values for the baud rates are shown in the table that follows this discussion.

The termios.h file defines the type speed_t as an unsigned integral type.

The cfgetospeed subroutine returns the output baud rate stored in the termios structure pointed to by the TermiosPointer parameter.

The cfsetospeed subroutine sets the output baud rate stored in the termios structure pointed to by the TermiosPointer parameter to the value specified by the Speed parameter.

The cfgetispeed subroutine returns the input baud rate stored in the termios structure pointed to by the TermiosPointer parameter.

The cfsetispeed subroutine sets the input baud rate stored in the termios structure pointed to by the TermiosPointer parameter to the value specified by the Speed parameter.

Certain values for speeds have special meanings when set in the termios structure and passed to the tcsetattr function. These values are discussed in the tcsetattr subroutine.

The following table lists possible baud rates:

Baud Rate Values
Name Description Name Description
B0 Hang up B600 600 baud
B5 50 baud B1200 1200 baud
B75 75 baud B1800 1800 baud
B110 110 baud B2400 2400 baud
B134 134 baud B4800 4800 baud
B150 150 baud B9600 9600 baud
B200 200 baud B19200 19200 baud
B300 300 baud B38400 38400 baud

The termios.h file defines the name symbols of the table.

Parameters

TermiosPointer Points to a termios structure.
Speed Specifies the baud rate.

Return Values

The cfgetospeed and cfgetispeed subroutines return exactly the value found in the termios data structure, without interpretation.

Both the cfsetospeed and cfsetispeed subroutines return a value of 0 if successful and -1 if unsuccessful.

Examples

To set the output baud rate to 0 (which forces modem control lines to stop being asserted), enter:

cfsetospeed (&my_termios, B0);
tcsetattr (stdout, TCSADRAIN, &my_termios);

Related Information

The tcsetattr subroutine.

The termios.h file.

Input and Output Handling Programmer's Overview in AIX 5L Version 5.2 General Programming Concepts: Writing and Debugging Programs.

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