no gui linux start background process and wait for complete

[Kvach-Lukich]

How to start carla in background and make some changes in jack after carla is ready
>/var/log/carla.log
nice -10 carla -n /var/www/dddsound_com/vst/presets/tcarla.carxp &>/var/log/carla.log &
str="Carla Bridge Ready"
while true
do
sleep 1
IFS= read -r line
if grep -q "$str" <<< "$line"; then
break
fi
done < /var/log/carla.log

I'm just checking log file for "Carla Bridge Ready" string and allow bash script to continue after that
Any ideas on how to do this correctly?