cfgetispeed - Linux


cfgetispeed is a versatile command that extracts the input baud rate (speed) from a specified serial port. It is commonly used for configuring serial port connections and monitoring communication parameters.


cfgetispeed <serial_port>


  • serial_port: The path to the serial port device, e.g., /dev/ttyS0 or /dev/ttyUSB0.


  • –help (-h): Displays a brief help message and usage information.
  • –version (-V): Shows the command’s version information.


Simple Usage

Get the input baud rate of the /dev/ttyS0 serial port:

cfgetispeed /dev/ttyS0

Complex Usage

Use a variable to store the baud rate and print it:

BAUD_RATE=$(cfgetispeed /dev/ttyS0)
echo "Baud rate: $BAUD_RATE"

Common Issues

  • No output: Check if the serial port path is correct and if the port is open.
  • Non-baud rate output: Ensure the port is configured in a raw mode or in a mode that supports baud rate.


Combine cfgetispeed with other commands for advanced tasks:

  • Setting baud rate: Set the output baud rate using cfgetospeed:
stty -F /dev/ttyS0 $(cfgetispeed /dev/ttyS0)

Related Commands

  • stty: Configure serial port settings
  • minicom: Serial port communication tool
  • screen: Terminal multiplexer for serial ports