LAB 17: LOOPS

Write a program called mchecker to check for new mail and write a message to the screen if new mail has arrived.
The program will get the size of the mail spool file for the user. (The spool files are found in /usr/mail/$LOGNAME on AT&T systems and /usr/spool/mail/$USER on UCB systems. Use the find command if you cannot locate the file.) The script will execute in a continuous loop, once every 30 seconds. Each time the loop executes, it will compare the size of the mail spool file with its size from the previous loop. If the new size is greater than the old size, a message will be printed on your screen, saying Username, You have new mail.
The size of a file can be found by looking at the output from ls –l, wc –c, or from the find command.
Write a program called dusage that will mail a list of users, one at a time, a listing of the number of blocks they are currently using. The list of users will be in a file called potential_hogs. One of the users listed in the potential_hogs file will be admin.
1. Use file testing to check that potential_hogs file exists and is readable.
2. A loop will be used to iterate through the list of users. Only those users who are using over 500 blocks will be sent mail. The user admin will be skipped over (i.e., he or she does not get a mail message). The mail message will be stored in a here document in your dusage script.
3. Keep a list of the names of each person who received mail. Do this by creating a log file. After everyone on the list has been sent mail, print the number of people who received mail and a list of their names.