3.5 Things to Try

• When your machine boots, it executes the commands in one or more Bourne shell scripts. Examine the script that runs the sendmail program in daemon mode. Write a small Bourne shell script that checks for the existence of the echo (1) program and then executes that program. Model it around the way sendmail is run.

• For each program that is mentioned in your configuration file's M lines (like /bin/mail and /bin/uux ), read the appropriate online manual page. Examine the possible command-line arguments to determine how envelope information is passed. Compare what you discover to the A= part of each corresponding M line.

• Locate all the files mentioned in O lines in your configuration file. For any that exist, what kind of file is it: data or text? If it is text, read it. What purpose do you suppose it has?