cfgetispeed() — Determine the input baud rate

Standards

Standards / Extensions	C or C++	Dependencies
POSIX.1 XPG4 XPG4.2 Single UNIX Specification, Version 3	both

Format

#define _POSIX_SOURCE
#include <termios.h>

speed_t cfgetispeed(const struct termios *termptr);

General description

Extracts the input baud rate from the termios structure indicated by *termptr. The termios structure contains information about a terminal. A program should first use tcgetattr() to get the termios structure, and then use cfgetispeed() to extract the speed from the structure. The program can then use cfgetispeed() to set a new baud rate in the structure and tcsetattr() to pass the changed value to the system.

Although in a z/OS® UNIX application valid speeds can be set with cfsetispeed() and passed to the system with tcsetattr(), the speed has no effect on the operation of a pseudoterminal. However, the operation will have an effect if issued for an OCS remote terminal.

Returned value

cfgetispeed() returns a code indicating the baud rate; see Table 1. These codes are defined in the termios.h header file and have an unsigned integer type.

There are no documented errno values.

Table 1. Baud Rate Codes
B0	Hang up
B50	50 baud
B75	75 baud
B110	110 baud
B134	134.5 baud
B150	150 baud
B200	200 baud
B300	300 baud
B600	600 baud
B1200	1200 baud
B1800	1800 baud
B2400	2400 baud
B4800	4800 baud
B9600	9600 baud
B19200	19,200 baud
B38400	38,400 baud

Example

CELEBC05

⁄* CELEBC05

   This example determines the speed of stdin.

 *⁄
#define _POSIX_SOURCE
#include <termios.h>
#include <stdio.h>

char *see_speed(speed_t speed) {
  static char   SPEED[20];
  switch (speed) {
    case B0:       strcpy(SPEED, "B0");
                   break;
    case B50:      strcpy(SPEED, "B50");
                   break;
    case B75:      strcpy(SPEED, "B75");
                   break;
    case B110:     strcpy(SPEED, "B110");
                   break;
    case B134:     strcpy(SPEED, "B134");
                   break;
    case B150:     strcpy(SPEED, "B150");
                   break;
    case B200:     strcpy(SPEED, "B200");
                   break;
    case B300:     strcpy(SPEED, "B300");
                   break;
    case B600:     strcpy(SPEED, "B600");
                   break;
    case B1200:    strcpy(SPEED, "B1200");
                   break;
    case B1800:    strcpy(SPEED, "B1800");
                   break;
    case B2400:    strcpy(SPEED, "B2400");
                   break;
    case B4800:    strcpy(SPEED, "B4800");
                   break;
    case B9600:    strcpy(SPEED, "B9600");
                   break;
    case B19200:   strcpy(SPEED, "B19200");
                   break;
    case B38400:   strcpy(SPEED, "B38400");
                   break;
    default:       sprintf(SPEED, "unknown (%d)", (int) speed);
  }
  return SPEED;
}

main() {
  struct termios term;
  speed_t speed;

  if (tcgetattr(0, &term) != 0)
    perror("tcgetattr() error");
  else {
    speed = cfgetispeed(&term);
    printf("cfgetispeed() says the speed of stdin is %s\n",
           see_speed(speed));
  }
}

Output

cfgetispeed() says the speed of stdin is B0