Linux Signals

In Linux, processes can send signals that are used to interrupt, announce asynchronous events to a process.

Common signals include:

• SIGINT is a signal generated when a user presses Control-C. This will terminate the program from the terminal.
• SIGALRM is generated when the timer set by the alarm function goes off.
• SIGABRT is generated when a process executes the abort function.
• SIGSTOP tells LINUX to pause a process to be resumed later.
• SIGCONT tells LINUX to resume the processed paused earlier.
• SIGSEGV is sent to a process when it has a segmentation fault.
• SIGKILL is sent to a process to cause it to terminate at once.

What happens when a signal occurs?

A process may choose to do one of three things…

• Ignore it: many can be ignored but Hardware signals like “divide by zero cannot be ignored successfully and some signals such as SIGKILL cannot be ignored at all.
• Catch and handle the exception: The process has some function to execute, but now it may terminate the program and handle the exception OR handle without terminating.
• Default Action: Every signal has some default action associated with it. These include:
  • ignore- terminate
  • terminate and dump core
  • stop or pause the program
  • resume a program paused earlier