Bash: "Execute for all subdirectories", execute commands in all subdirectorys, cache output and print sequentially with locking

forallsubdirs.sh

# Add this to your .bashrc and source it (source ~/.bashrc)
# Example: forallsubdirs basedir commands
#   - forallsubdirs . "ls | wc -l; git status"
#   - forallsubdirs . "git fetch --all; git merge --ff-only"
# Note:
#   - To include hidden directories (starting with a "."), set the dotglob option in Bash: shopt -s dotglob
#   - Silencing job control (see comments) is only partially possible, in certain cases job control output will still be printed (see https://stackoverflow.com/a/38278291/202504).
forallsubdirs() {
  if [ -d "$1" ]; then
    dir="$1"
    shift
    # create a tmp file and immediately delete it, but keep a handle
    lockfile=$(mktemp /tmp/bashrc-execfsd-flock.XXXXXX); exec 3>"$lockfile"; rm "$lockfile"
    for i in "${dir%/}"/*; do
      if [[ -d "$i" && ! -L "$i" ]]; then # directories, exclude symlinks.
        echo "$i"
        # note: do not add further brackets, this only works for max 1 subshell. flock() to force sequential output.
        {(res=$(exec 2>&1; echo "$i:"; cd $i; eval "$@"); flock 3; printf "\n%s\n" "$res") & } #2>/dev/null #uncomment to silence job control
      fi
    done
    wait #2>/dev/null #uncomment to silence job control
    echo "Done."
  else
    echo "not a directory: $1"
    return 1
  fi
}