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Linux signals

Signals​

  • signals are used to notify processes about events in Inter Process Communication
  • signal is an asynchronous event:
    • not expected
    • expected, but the time is not know
  • signals are sent from the kernel or from a user process via system call with kill
  • user can send signal to his own processes
  • root can send signal to any process
  • signals can be handled differently by the programmer or resbond acording to the system defaults
  • two signal always use the system default: SIGKILL and SIGSTOP
  • signal has a type and the type is indicate the meaning of the signal
  • signals handle:
    • exceptions detected by the hardware
    • exceptions generated by the environment
  • when signal sent from the kernel: the meaning attached to the signal
  • The full list if signals is here
  • SIGTERM: kills the process gracefully
  • SIGKILL: kills the process immediately
  • SIGRTMIN:
    • no predefined purpose
    • can be stacked, handled in FIFO

Reference​

  • LFS201 (this is just my note from LFS201, not meant to replace the original, which is explain better the above)