Simple serial console logger with timestamps to use with screen

logger.py

#!/usr/bin/env python3
import sys
import argparse
import datetime
import serial


## Initiate logging like: screen -d -m -S foobar ./logger.py -b 115200 -p foobar /dev/ttyACM1
## Check command line options with ./logger.py -h
## Written with help from OpenAI Codex (GPT-5.6 Sol Medium)

def main():
    # Parse command line arguments
    parser = argparse.ArgumentParser(
        description="Serial Logger with Timestamps"
    )
    parser.add_argument(
        "port",
        nargs="?",
        default="/dev/ttyUSB0",
        help="Serial port device (e.g. /dev/serial0, /dev/ttyUSB0, /dev/ttyACM0). Default: /dev/ttyUSB0"
    )
    parser.add_argument(
        "-b", "--baud",
        type=int,
        default=115200,
        help="Baud rate (default: 115200)"
    )
    parser.add_argument(
        "-p", "--prefix",
        default="logger",
        help="Log filename prefix (default: logger)"
    )
    args = parser.parse_args()

    # Generate filename with starting timestamp
    start_time_str = datetime.datetime.now().strftime("%Y%m%d_%H%M%S")
    log_filename = f"{args.prefix}-{start_time_str}.log"

    print(f"[*] Opening serial port: {args.port} at {args.baud} baud")
    print(f"[*] Logging output to: {log_filename}")
    print("[*] Press Ctrl+C to stop logging.\n" + "-" * 50)

    try:
        # Open serial port
        ser = serial.Serial(args.port, args.baud, timeout=1)

        # Open log file in append mode with explicit line flushing
        with open(log_filename, "a", encoding="utf-8", errors="replace") as log_file:
            while True:
                # Read line from serial buffer
                raw_line = ser.readline()

                if raw_line:
                    # Decode byte stream to string
                    decoded_line = raw_line.decode"utf-8", errors="replace").rstrip("\r\n")

                    if decoded_line:
                        # Timestamp each line
                        now_str = datetime.datetime.now().strftime("[%Y-%m-%d %H:%M:%S]")
                        formatted_line = f"{now_str} {decoded_line}\n"

                        # Print to screen
                        sys.stdout.write(formatted_line)
                        sys.stdout.flush()

                        # Save to log file
                        log_file.write(formatted_line)
                        log_file.flush()

    except serial.SerialException as e:
        print(f"\n[!] Serial Error: {e}")
        sys.exit(1)
    except KeyboardInterrupt:
        print("\n[*] Logging stopped by user.")
        sys.exit(0)


if __name__ == "__main__":
    main()