'\" te
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.TH KILL 2 "Mar 22, 2004"
.SH NAME
kill \- send a signal to a process or a group of processes
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <signal.h>

\fBint\fR \fBkill\fR(\fBpid_t\fR \fIpid\fR, \fBint\fR \fIsig\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBkill()\fR 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 \fIpid\fR. The signal that is to be sent is specified by \fIsig\fR
and is either one from the list given in \fBsignal\fR (see
\fBsignal.h\fR(3HEAD)), or 0. If \fIsig\fR is 0 (the null signal), error
checking is performed but no signal is actually sent. This can be used to check
the validity of \fIpid\fR.
.sp
.LP
The real or effective user ID of the sending process must match the real or
saved (from one of functions in the \fBexec\fR(2) family) user ID of the
receiving process, unless the privilege {\fBPRIV_PROC_OWNER\fR} is asserted in
the effective set of the sending process (see \fBIntro\fR(2)), or \fIsig\fR is
\fBSIGCONT\fR and the sending process has the same session \fBID\fR as the
receiving process. A process needs the basic privilege
{\fBPRIV_PROC_SESSION\fR} to send signals to a process with a different session
ID. See \fBprivileges\fR(5).
.sp
.LP
If \fIpid\fR is greater than 0, \fIsig\fR will be sent to the process whose
process ID is equal to  \fIpid\fR.
.sp
.LP
If \fIpid\fR is negative but not \fB(pid_t)\(mi1\fR, \fIsig\fR will be sent to
all processes whose process group ID is equal to the absolute value of
\fIpid\fR and for which the process has permission to send a signal.
.sp
.LP
If \fIpid\fR is 0, \fIsig\fR will be sent to all processes excluding special
processes (see \fBIntro\fR(2)) whose process group ID is equal to the process
group ID of the sender.
.sp
.LP
If \fIpid\fR is \fB(pid_t)\(mi1\fR and the {\fBPRIV_PROC_OWNER\fR} privilege is
not asserted in the effective set of the sending process, \fIsig\fR will be
sent to all processes excluding special processes whose real user ID is equal
to the effective user \fBID\fR of the sender.
.sp
.LP
If \fIpid\fR is \fB(pid_t)\(mi1\fR and the {\fBPRIV_PROC_OWNER\fR} privilege is
asserted in the effective set of the sending process, \fIsig\fR will be sent to
all processes excluding special processes.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, 0 is returned. Otherwise, \(mi1 is returned, no
signal is sent, and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBkill()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIsig\fR argument is not a valid signal number.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The \fIsig\fR argument is \fBSIGKILL\fR and the \fIpid\fR argument is
\fB(pid_t)-1\fR (that is, the calling process does not have permission to send
the signal to any of the processes specified by \fIpid\fR).
.sp
The effective user of the calling process does not match the real or saved user
and the calling process does not have the {\fBPRIV_PROC_OWNER\fR} privilege
asserted in the effective set, and the calling process either is not sending
\fBSIGCONT\fR to a process that shares the same session \fBID\fR or does not
have the {\fBPRIV_PROC_SESSION\fR} privilege asserted and is trying to send a
signal to a process with a different session ID.
.RE

.sp
.ne 2
.na
\fB\fBESRCH\fR\fR
.ad
.RS 10n
No process or process group can be found corresponding to that specified by
\fIpid\fR.
.RE

.SH USAGE
.sp
.LP
The \fBsigsend\fR(2) function provides a more versatile way to send signals to
processes.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	Async-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBkill\fR(1), \fBIntro\fR(2), \fBexec\fR(2), \fBgetpid\fR(2), \fBgetsid\fR(2),
\fBsetpgrp\fR(2), \fBsigaction\fR(2), \fBsigsend\fR(2), \fBsignal\fR(3C),
\fBsignal.h\fR(3HEAD), \fBattributes\fR(5), \fBprivileges\fR(5),
\fBstandards\fR(5)