Write a script named ifthen that prompts the user with >> and reads a string of text from the user. If the user enters a nonnull string, the script displays You entered: followed by the string; otherwise it displays Where is your input?. Use an if...then...else control structure to implement the two-way branch in the script. Use a test to determine if the user enters a null string. What do you have to do to avoid getting an error message when you prompt with >>?