kill - send signal to a process
int kill(pid_t pid, int sig)
Kill sends the signal sig to a process, specified by the process number
pid. Sig may be one of the signals specified in sigaction(2), or it may
be 0, in which case error checking is performed but no signal is actually
sent. This can be used to check the validity of pid.
The sending and receiving processes must have the same effective user ID,
otherwise this call is restricted to the super-user.
If the process number is 0, the signal is sent to all processes in the
sender's process group.
If the process number is -1 and the user is the super-user, the signal is
broadcast universally except to init and the process sending the signal.
If the process number is -1 and the user is not the super-user, the
signal is broadcast universally to all processes with the same uid as the
user except the process sending the signal. No error is returned if any
process could be signaled.
If the process number is negative but not -1, the signal is sent to all
processes whose process group ID is equal to the absolute value of the
Processes may send signals to themselves.
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
Kill will fail and no signal will be sent if any of the following occur:
[EINVAL] Sig is not a valid signal number.
[ESRCH] No process can be found corresponding to that specified by
[ESRCH] The process id was given as 0 but the sending process does
not have a process group.
[EPERM] The sending process is not the super-user and its
effective user id does not match the effective user-id of
the receiving process. When signaling a process group,
this error was returned if any members of the group could
not be signaled.
getpid(2), getpgrp(2), sigaction(2), raise(3).