femtocom - super simple serial port handler

femtocom.sh

#!/bin/bash
# Adapted from https://unix.stackexchange.com/a/311680/81195
# I added tput, fuser and cleanup

if [[ $# -lt 1 ]]; then
    echo "Usage:"
    echo "  femtocom <serial-port> [ <speed> [ <stty-options> ... ] ]"
    echo "  Example: $0 /dev/ttyS0 9600"
    echo "  Press Ctrl+Q to quit"
fi

cleanup() {
	set +e
	[[ -n "$bgPid" ]] && kill "$bgPid"
	stty "$original_settings"
}

set -e    # Exit when any command fails

# Save settings of current terminal to restore later
original_settings="$(stty -g)"

# Kill background process and restore terminal when this shell exits
trap cleanup EXIT

# Remove serial port from parameter list, so only stty settings remain
port="$1"; shift

# kill any other processes using the port, if any
fuser -k "$port" || true

# Set up serial port, append all remaining parameters from command line
stty -F "$port" raw -echo "$@"

# Set current terminal to pass through everything except Ctrl+Q
# * "quit undef susp undef" will disable Ctrl+\ and Ctrl+Z handling
# * "isig intr ^Q" will make Ctrl+Q send SIGINT to this script
stty raw -echo isig intr ^Q quit undef susp undef

echo "Connecting to $port. Press Ctrl+Q to exit."

# Let cat read the serial port to the screen in the background
# Capture PID of background process so it is possible to terminate it
cat "$port" & bgPid=$!

# Move cursor to the beginning
tput cr

cat >"$port"   # Redirect all keyboard input to serial port