Running parallel batch tasks in bash

parallel no semaphore.sh

#!/bin/bash

task() {
  sleep 1; echo "$1 - $(date)";
}

N=2

for item in {1..6}; do
  ((i=i%N)); ((i++==0)) && wait
  task "$item" &
done

wait

parallel semaphore.sh

#!/bin/bash

task() {
  sleep 1; echo "$1 - $(date)";
}

export -f task # so sem has access

N=2 # the size of each batch

for item in {1..6}; do
  sem -j $N task "$item"
done

sem --wait