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 control structure (sobell, page 424) to implement the two-way branch in the script. use the test (sobell, pages 420 and 978) builtin 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 > > ? (there are several ways to construct the test statement.)