A signal is a type of message sent from the system to inform a command or script that an event has occurred somewhere. The events are usually to do with memory error, access problems or some user trying to stop your process. The signals are actually numbers. Below is a table listing the most used signals and their meaning.
|Signal no.||Signal name||Meaning|
|1||SIGHUP||Hangup or parent process killed|
|2||SIGINT||Interrupt from keyboard, usually <CTRL-C>|
|3||SIGQUIT||Quit from the keyboard|
|11||SIGSEGV||Segmentation (memory) violation|
|15||SIGTERM||Software termination (default kill)|
There is a signal 0, which we have already met when we created a .logout file earlier in the book. This signal is the ‘exit from shell’ signal. ...