Shell Programming and Scripting

#!/bin/sh
DIR="$1"
if [ $# -lt 1 ]
then
        echo "You haven't given any parameters, please give a directory and run the program in the following format: sh <programname.sh> <directory>"

elif [ ! -e "$DIR" ]
then
        echo "The directory you have specified does not exist."

elif [ ! -d $DIR ]
then
        echo "The parameter you have specified is not a directory, please specify a directory to run the program."
else
        du -s -m "$DIR"
fi

#! /bin/bash

if [ $# -lt 1 ]
then
    echo "No parameters. Exiting."
    exit
fi

sum=0
for i in $@
do
    if [ -d $i ]
    then
        sum=$(($sum + `du $i | awk '{print $1}'`))
    else
        continue
    fi
done

echo $sum

if [[ $# -ne 1 ]] ; then   #-ne  not equals
  echo "I need just 1 argument. No more, no less." 
  exit 1
fi