commandliners

You know kill utility sends a signal to the processes specified by their pid. If you want to know all the signals implemented by your Operating System and supported by any process, type:

$ kill -l
 1) SIGHUP       2) SIGINT       3) SIGQUIT      4) SIGILL
 5) SIGTRAP      6) SIGABRT      7) SIGEMT       8) SIGFPE
 9) SIGKILL     10) SIGBUS      11) SIGSEGV     12) SIGSYS
13) SIGPIPE     14) SIGALRM     15) SIGTERM     16) SIGURG
17) SIGSTOP     18) SIGTSTP     19) SIGCONT     20) SIGCHLD
21) SIGTTIN     22) SIGTTOU     23) SIGIO       24) SIGXCPU
25) SIGXFSZ     26) SIGVTALRM   27) SIGPROF     28) SIGWINCH
29) SIGINFO     30) SIGUSR1     31) SIGUSR2

I ran it on a Mac OS X and it shows all the above values. Some of the most used ones are:

  1       HUP (hang up)
  2       INT (interrupt)
  3       QUIT (quit)
  6       ABRT (abort)
  9       KILL (non-catchable, non-ignorable kill)
  14      ALRM (alarm clock)
  15      TERM (software termination signal)

Remember that only the super-user can send signals to other users’ processes.