Signals

Signals are used for communication between processes. If you start a new process, how can you communicate with it through your shell or any other program or process while it is running? Also, how does the parent process know when the child process is finishing? For example, how does your Bash know when the ls -al command is terminating? In Linux, this kind of notification and interprocess communication is done using signals. In Linux, if a process starts another process, the parent process is put to sleep until the child process command has finished, which will trigger a special signal and this will wake up the parent process. The parent process is put to sleep so that no active CPU time is needed for waiting. A popular signal is the seek or interrupt signal, which will be sent to the running process each time we press Ctrl + C in an active program. This will interrupt...