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)