Problem
A telephone directory, teledir.txt, maintains records in the form name: number where number is of the form nnn-nnn-nnnn. Devise a shell script that accepts one or two arguments that could be:
(i) the name or number. If it exists in the directory, then the line should be displayed.
(ii) both. The entry is displayed if it exists and is added if it doesn't exist in the file. Note that the number will always be entered as a 10-digit string, so you'll have to use the script developed in Exercise 18 to perform both conversion and validation.
Exercise 18
Display the processes in the system every 30 seconds five times using a
(i) while loop,
(ii) for loop. What is the unusual feature of the for loop that you used?