KILL(2) System Calls KILL(2)

NAME

kill - send a signal to a process or a group of processes

SYNOPSIS

#include <sys/types.h>
#include <signal.h>

int kill(pid_t pid, int sig);

DESCRIPTION

The kill() function sends a signal to a process or a group of processes.
The process or group of processes to which the signal is to be sent is
specified by pid. The signal that is to be sent is specified by sig and
is either one from the list given in signal (see signal.h(3HEAD)), or 0.
If sig is 0 (the null signal), error checking is performed but no signal
is actually sent. This can be used to check the validity of pid.


The real or effective user ID of the sending process must match the real
or saved (from one of functions in the exec(2) family) user ID of the
receiving process, unless the privilege {PRIV_PROC_OWNER} is asserted in
the effective set of the sending process (see Intro(2)), or sig is
SIGCONT and the sending process has the same session ID as the receiving
process. A process needs the basic privilege {PRIV_PROC_SESSION} to send
signals to a process with a different session ID. See privileges(7).


If pid is greater than 0, sig will be sent to the process whose process
ID is equal to pid.


If pid is negative but not (pid_t)-1, sig will be sent to all processes
whose process group ID is equal to the absolute value of pid and for
which the process has permission to send a signal.


If pid is 0, sig will be sent to all processes excluding special
processes (see Intro(2)) whose process group ID is equal to the process
group ID of the sender.


If pid is (pid_t)-1 and the {PRIV_PROC_OWNER} privilege is not asserted
in the effective set of the sending process, sig will be sent to all
processes excluding special processes whose real user ID is equal to the
effective user ID of the sender.


If pid is (pid_t)-1 and the {PRIV_PROC_OWNER} privilege is asserted in
the effective set of the sending process, sig will be sent to all
processes excluding special processes.

RETURN VALUES

Upon successful completion, 0 is returned. Otherwise, -1 is returned, no
signal is sent, and errno is set to indicate the error.

ERRORS

The kill() function will fail if:

EINVAL
The sig argument is not a valid signal number.


EPERM
The sig argument is SIGKILL and the pid argument is (pid_t)-1
(that is, the calling process does not have permission to send
the signal to any of the processes specified by pid).

The effective user of the calling process does not match the
real or saved user and the calling process does not have the
{PRIV_PROC_OWNER} privilege asserted in the effective set, and
the calling process either is not sending SIGCONT to a process
that shares the same session ID or does not have the
{PRIV_PROC_SESSION} privilege asserted and is trying to send a
signal to a process with a different session ID.


ESRCH
No process or process group can be found corresponding to that
specified by pid.

USAGE

The sigsend(2) function provides a more versatile way to send signals to
processes.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Standard |
+--------------------+-------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+-------------------+

SEE ALSO

kill(1), Intro(2), exec(2), getpid(2), getsid(2), setpgrp(2),
sigaction(2), sigsend(2), signal(3C), signal.h(3HEAD), attributes(7),
privileges(7), standards(7)

March 22, 2004 KILL(2)