Signals and the KILL command

COMMAND: KILL

The kill command sends a signal to specified processes or process groups causing them to act according to the signal.

Kill -<value or signal> <pid>

Most common:
Kill -9 <pid>
equal to
Kill -SIGKILL <pid>

CAN I TERMINATE THREADS INSTEAD OF PROCESSES?

NO.

Threads are an integral part of the process and cannot be killed outside it. There is the pthread_kill function but it only applies in the context of the thread itself. Indeed, pthread_kill only causes the signal to be handled in the context of the given thread; the signal actions "termination" or "stopping" affect the process as a whole.

LIST OF SIGNALS

Signal          Value    Action   Comment  ──────────────────────────────────────────────────────────

   SIGHUP        1       Term    Hangup detected on controlling terminal or death of controlling process

   SIGINT        2       Term    Interrupt from keyboard

   SIGQUIT       3       Core    Quit from keyboard

   SIGILL        4       Core    Illegal Instruction

   SIGABRT       6       Core    Abort signal from abort(3)

   SIGFPE        8       Core    Floating point exception

   SIGKILL       9       Term    Kill signal

   SIGSEGV      11       Core    Invalid memory reference

   SIGPIPE      13       Term    Broken pipe: write to pipe with no readers

   SIGALRM      14       Term    Timer signal from alarm(2)

   SIGTERM      15       Term    Termination signal

   SIGUSR1   30,10,16    Term    User-defined signal 1

   SIGUSR2   31,12,17    Term    User-defined signal 2

   SIGCHLD   20,17,18    Ign     Child stopped or terminated

   SIGCONT   19,18,25    Cont    Continue if stopped

   SIGSTOP   17,19,23    Stop    Stop process

   SIGTSTP   18,20,24    Stop    Stop typed at terminal

   SIGTTIN   21,21,26    Stop    Terminal input for background process

   SIGTTOU   22,22,27    Stop    Terminal output for background process