Bash: Get Cell Signal Strength

get-cell-signal.sh

#!/bin/bash

. /usr/bin/pdivt-funcs

pipe="$(mktemp -u)"

log info "Logging cell signal level..."

log info "Creating fifo at $pipe..."
mkfifo $pipe

# Start cat /dev/ttyUSB0 in the background and send its output to fifo
log info "Listening to /dev/ttyUSB0 and redirecting to $pipe..."
cat /dev/ttyUSB0 > $pipe &
catPid=$!

trap "kill -9 $catPid >& /dev/null; rm -rf $pipe >& /dev/null;" 0

# Send the signal query command to the device
(
    sleep 1
    log info "Sending cell signal query to /dev/ttyUSB0..."
    echo 'AT+CSQ' > /dev/ttyUSB0
) &

# Read the output from the device line by line until one line contains OK
log info "Waiting for cell signal query response..."
while read line; do
    case "$line" in
    *OK*)
        break
        ;;
    "")
        ;;
    *)
        line="${line// /}"
        line=( ${line//,/ } )
        log info "Cell signal level is ${line[1]}."
        echo "${line[1]}" > /tmp/cell-signal
        log info "Cell signal level saved to /tmp/cell-signal."
        ;;
   esac
done < $pipe

exit