NAME
kill - send signal to a process

SYNOPSIS
kill(pid, sig)
int pid, sig;

DESCRIPTION
Kill sends the signal sig to a process, specified by the process
number pid. Sig may be one of the signals specified in sigvec(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. A
single exception is the signal SIGCONT, which may always be sent to
any descendant of the current process.

If the process number is 0, the signal is sent to all processes in
the sender’s process group; this is a variant of killpg(2).

If the process number is -1 and the user is the super-user, the
signal is broadcast universally except to system processes 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.

For compatibility with System V, 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 process number. This is a
variant of killpg(2).

Processes may send signals to themselves.

RETURN VALUE
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and errno is set to indicate the error.

ERRORS
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 pid.

[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.

SEE ALSO
getpid(2), getpgrp(2), killpg(2), sigvec(2)