bash while loop threading

Question

i have a while loop reading lines from a $hosts

while read line
do
    ip=$line
    check
done < $hosts

my question is can I us

Answer 1

You can start multiple processes, each calling the function check and wait for them to finish.

while read line 
do 
  ip=$line
  check &
done < $hosts
wait # wait for all child processes to finish

Whether this increases the speed depends on available processors and the function check's implementation. You have to ensure there's no data dependency in check between iterations.