The cfsetspeed function is provided for setting the baud rate values in the termios structure. The effects of the function on the terminal as described below do not become effective, nor are all errors detected, until the tcsetattr function is called. Certain values for baud rates set in the termios structure and passed to tcsetattr have special meanings.
The input and output baud rates are found in the termios structure. The unsigned integer speed_t is typdef'd in the include file <termios.h>. The value of the integer corresponds directly to the baud rate being represented, however, the following symbolic values are defined.
#define B0 0
#define B50 50
#define B75 75
#define B110 110
#define B134 134
#define B150 150
#define B200 200
#define B300 300
#define B600 600
#define B1200 1200
#define B1800 1800
#define B2400 2400
#define B4800 4800
#define B9600 9600
#define B19200 19200
#define B38400 38400
#ifndef _POSIX_SOURCE
#define EXTA 19200
#define EXTB 38400
#endif /*_POSIX_SOURCE */
The cfsetspeed function sets both the input and output baud rate in the termios structure referenced by t to speed.