Get signal quality from GPRS modem

A quite sophisticated bash script for getting signal quality (AT+CSQ) from GPRS modem:



#!/bin/bash


function get_response
{
        local ECHO
        # cat will read the response, then die on timeout
        cat <&5 >$TMP &
        echo "$1" >&5
        # wait for cat to die
        wait $!


        exec 6<$TMP
        read ECHO <&6
        if [ "$ECHO" != "$1" ]
        then
                exec 6<&-
                return 1
        fi


        read ECHO <&6
        read RESPONSE <&6
        exec 6<&-
        return 0
}


TMP="/tmp/response"


# Clear out old response
: > $TMP


# Set modem with timeout of 5/10 a second
stty -F /dev/ttyACM0 -echo igncr -icanon onlcr ixon min 0 time 5


# Open modem on FD 5
exec 5<>/dev/ttyACM0


get_response "AT" || echo "Bad response"
RESPONSE=`cat $TMP`
echo "Response was ${RESPONSE}"


echo


get_response "AT+CSQ" || echo "Bad response"
RESPONSE=`cat $TMP`
echo "Response was ${RESPONSE}"


exec 5<&-