And here is an example of how to call an AT command and read back output in a simple bash script. We use things like this as a quick way to monitor cellular coverage.

# AT Command for monitoring network coverage
#!/bin/bash
while true; do
	date
	echo -ne "AT+QENG=\"servingcell\"\r" | busybox microcom -t 1000 /dev/ttyUSB2
        echo -e "-----------------------------------------------------------------\n"
        sleep 5
done