The
kill()
system call sends the signal given by
sig
to
pid,
a
process or a group of processes.
The
sig
argument
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.
For a process to have permission to send a signal to a process designated
by
pid,
the user must be the super-user, or
the real or saved user ID of the receiving process must match
the real or effective user ID of the sending process.
A single exception is the signal SIGCONT, which may always be sent
to any process with the same session ID as the sender.
In addition, if the
security.bsd.conservative_signals
sysctl(9)
is set to 1, the user is not a super-user, and
the receiver is set-uid, then
only job control and terminal control signals may
be sent (in particular, only SIGKILL, SIGINT, SIGTERM, SIGALRM,
SIGSTOP, SIGTTIN, SIGTTOU, SIGTSTP, SIGHUP, SIGUSR1, SIGUSR2).
|
| amp;Ifpid, No, amp;is, greater, than, zero:
|
| |
The
sig
signal
is sent to the process whose ID is equal to
pid.
|
| amp;Ifpid, No, amp;is, zero:
|
| |
The
sig
signal
is sent to all processes whose group ID is equal
to the process group ID of the sender, and for which the
process has permission;
this is a variant of
killpg(2).
|
| amp;Ifpid, No, amp;is, -1:
|
| |
If the user has super-user privileges,
the signal is sent to all processes excluding
system processes
(with
P_SYSTEM
flag set),
process with ID 1
(usually
init(8)),
and the process sending the signal.
If the user is not the super user, the signal is sent to all processes
which the caller has permissions to, excluding 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 process number.
This is a variant of
killpg(2).
