export doesn't work in a background process

Question

pipe.sh

 export START=100
 . ./other.sh &
 wait

other.sh

sleep 5
export END=200

Answer 1

A child process cannot change parents environment, you need to declare the variable from the parent somehow. For example using a file:

pipe.sh:

export START=100
. ./other.sh > tmp &
wait
source tmp
rm tmp 
echo $END

other.sh:

sleep 5
echo "export END=200"

Also see this answer.