Making a Script Behave Like a Daemon

In this chapter, we will introduce the following topics:

• Running a program continuously (forever) using looping constructs or recursion
• Keeping programs/scripts running after logoff
• Invoking commands when they require permissions
• Sanitizing user input and for repeatable results
• Making a simple multi-level user menu using select
• Generating and trapping signals for cleanup
• Using temporary files and lock files in your program
• Leveraging timeout when waiting for command completion
• Creating a file-in-file-out program and running processes in parallel
• Executing your script on startup