Problem
1. Look up the man page for any shell and understand the significance of the -c option. Next, write a program that prompts for a command, which is executed with exec and sh -c. Try using the program with both external and internal (shell) commands. Does this program behave properly, even when using wild cards and pipes?
2. In what ways can a process behave when it receives a signal? What is special about the SIGSTOP and SIGKILL signals?
3. Invoke the command vi foo &, and explain why you can't input text to the editor.