Shell Scripting: Expert Recipes for Linux, Bash, and More

Chapter 20

Processes

Controlling processes is one of the key tasks of the operating system’s kernel. The kernel also provides a signal-sending facility which enables one process to send a message to another. These can be handled by the trap facility of the receiving shell. Other methods are also available: for example, the mere existence of a file may be used to change a script’s behavior. This recipe uses both of these methods. This recipe also makes use of the pgrep and kill commands to find running processes as well as sending signals to them.