Runs a bash function on all child directories in parallel

run-func-on-dirs-in-parallel.sh

#!/usr/bin/env bash

set -euo pipefail

do_something() {
  dir=$1

  echo "doing something with $dir"
  sleep 1
}

main() {
  root_dir="$(cd "$(dirname "$0")" && pwd)"
  directories_in_parallel="8"

  find "${root_dir}" -type d -depth 1 -print0 | \
    xargs -0 -P${directories_in_parallel} -I {} bash -c "$(declare -f do_something) ; do_something {}"
}

main "$@"