Kill signals

SIGNALS

      The  signals  listed  below  may  be available for use with kill.  When
      known constant, numbers and default behavior are shown.

      Name     Num   Action    Description
      ()                                                                          ()

      0          0   n/a       exit code indicates if a signal may be sent
      ALRM      14   exit
      HUP        1   exit
      INT        2   exit
      KILL       9   exit      this signal may not be blocked
      PIPE      13   exit
      POLL           exit
      PROF           exit
      TERM      15   exit
      USR1           exit
      USR2           exit
      VTALRM         exit
      STKFLT         exit      may not be implemented
      PWR            ignore    may exit on some systems
      WINCH          ignore
      CHLD           ignore
      URG            ignore
      TSTP           stop      may interact with the shell
      TTIN           stop      may interact with the shell
      TTOU           stop      may interact with the shell
      STOP           stop      this signal may not be blocked
      CONT           restart   continue if stopped, otherwise ignore
      ABRT       6   core
      FPE        8   core
      ILL        4   core
      QUIT       3   core
      SEGV      11   core
      TRAP       5   core
      SYS            core      may not be implemented
      EMT            core      may not be implemented
      BUS            core      core dump may fail

      XCPU           core      core dump may fail
      XFSZ           core      core dump may fail

Mostly used in real life are 15 (default), 1 (allowing cleanup) and 9 (as last resort). But read here why you should avoid 9 if possible: Useless use of kill -9. Its better to try in this order and only use the next if the previous failed: 15 (TERM) -> 2 (INT) -> 1 (HUP) -> 9 (KILL).

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