[man] kill

kill

#include <signal.h>

The kill() system call can be used to send any signal to any process group or process.

int kill(pid_t pid, int sig);

PARAMETERS

-pid

• pid > 0
  : signal sig is sent to the process with the ID specified by pid.
• pid == 0
  : sig is sent to every process in the process group of the calling process.
• pid == -1
  : sig is sent to every process for which the calling process has permission to send signals, except for process 1 (init).
• pid < -1
  : sig is sent to every process in the process group whose ID is -pid.

-sig

• sig == 0
  : no signal is sent, but existence and permission checks are still performed.
  ⏩ this can be used to check for the existence of a process ID or process group ID that the caller is permitted to signal.

RETURN VALUE
: On success (at least one signal was sent), 0 is returned.
On error, -1 is returned, and errno is set to indicate the error.

📖 kill