Function kill 

#[unsafe(no_mangle)]
pub extern "C" fn kill(pid: pid_t, sig: c_int) -> c_int

See https://pubs.opengroup.org/onlinepubs/9799919799/functions/kill.html.

Sends a signal to a process or a group of processes specified by pid.

Upon success, returns 0. Upon failure, returns -1 and sets errno to indicate the error. No signal is sent if failed.