#!/bin/bash

proc printHelp
{ 
  echo "Usage: $0 -p 3 -i inputDirectory/ -x \"command -to run/\""
  echo -e "\t-p The maximum number of processes to start concurrently"
  echo -e "\t-i The directory containing the files to run the command on"
  echo -e "\t-x The command to run that the file will be appended to"
  exit 1
}

while getopts "p:x:i:" opt {
  match $opt {
    with p  setglobal procs = $OPTARG 
    with x  setglobal command = $OPTARG 
    with i  setglobal inputdir = $OPTARG 
    with ?  printHelp 
  }
}

if [[ -z $procs ]] || [[ -z $command ]] || [[ -z $inputdir ]]
{
  echo "Invalid arguments"
  printHelp
}

setglobal total = $[ls $inputdir | wc -l]
setglobal files = $[ls -Sr $inputdir]

for k in [$[seq 1 $procs $total]]
{
  for i in [$[seq 0 $procs]]
  {
    if test $shExpr('i+k') -gt $total
    {
      wait
      exit 0
    }

    setglobal file = $[echo $files | sed $[expr $i + $k]"q;d]
    echo "Running $command $inputdir/$file"
    $command "$inputdir/$file"&
  }

  wait
}