Gammu modem changes /dev/ttyUSBx name

[deajan]

Hello,

Not an issue actually, but merely a post with a script to detect whenever a USB modem changes it's name (when disconnected / reconnected while it's old port is being read).

The following script updates the modem device path in /etc/gammu-smsdrc whenever needed.
You can configure it as cron task every 15 minutes or so

#!/usr/bin/env bash

log_file="/var/log/modem_update.log"
gammu_config_file="/etc/gammu-smsdrc"
modem=""
# Optional command when modem port change detected
optional_cmd="systemctl restart gammu-smsd"

function log {
    line="${1}"

    echo "${line}" >> "${log_file}"
    echo "${line}"
}

for tty in $(ls /dev/ttyUSB*); do
    log "Checking $tty"
    picocom -qrX -b 9600 $tty
    sleep 1
    result=$(echo "AT&F" | picocom -qrix 1000 $tty)
    if [ "${result}" = "AT&F" ]; then
        log "Found AT compatible modem at $tty"
        modem="${tty}"
    else
        log "No AT compatible modem at $tty"
    fi
done

curr_gammu_modem=$(cat "${gammu_config_file}" | grep "device = " | awk -F'=' '{gsub(/ /,""); print $2}')
if [ "${modem}" != "" ]; then
    if [ "${modem}" != "${curr_gammu_modem}" ]; then
        log "Updating modem from ${curr_gammu_modem} to ${modem}"
        sed -i "s%${curr_gammu_modem}%${modem}%" "${gammu_config_file}"
        if [ "${optional_cmd}" != "" ]; then
            log "Running ${optional_cmd}"
            ${optional_cmd} >> "${log_file}"
            if [ $? -ne 0 ]; then
                log "Could not restart service, exitcode: $?"
            fi
        fi
    fi
fi

Hope this helps someone ;)