a brutally simple serial term

scat.sh

#!/bin/bash

# Derived from https://unix.stackexchange.com/a/311680/295309

if [[ $# -lt 1 ]]; then
    echo "Usage:"
    echo "    $0 <serial-port> [ <speed> [ <stty-options> ...] ]"
    echo "    Example: $0 /dev/ttyS0 115200"
    echo "    Use ^Q to quit"
    exit 1
fi

set -e
orig_settings=$(stty -g)
trap 'set +e; kill "$catpid"; stty "$orig_settings"' EXIT

port="$1"; shift
stty -F "$port" raw -echo "$@"
# Pass thru *everything* except Ctrl+Q (which sends SIGINT to this)
stty raw -echo isig intr ^Q quit undef susp undef
cat "$port" & catpid=$!
cat >"$port"