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-.\" Hey Emacs! This file is -*- nroff -*- source.
-.\"
-.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
-.\"
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\"
-.\" Modified by Michael Haardt <michael@moria.de>
-.\" Modified by Thomas Koenig <ig25@rz.uni-karlsruhe.de>
-.\" Modified 1993-07-23 by Rik Faith <faith@cs.unc.edu>
-.\" Modified 1993-07-25 by Rik Faith <faith@cs.unc.edu>
-.\" Modified 1995-11-01 by Michael Haardt
-.\" <michael@cantor.informatik.rwth-aachen.de>
-.\" Modified 1996-04-14 by Andries Brouwer <aeb@cwi.nl>
-.\" [added some polishing contributed by Mike Battersby <mib@deakin.edu.au>]
-.\" Modified 1996-07-21 by Andries Brouwer <aeb@cwi.nl>
-.\" Modified 1997-01-17 by Andries Brouwer <aeb@cwi.nl>
-.\" Modified 2001-12-18 by Andries Brouwer <aeb@cwi.nl>
-.\" Modified 2002-07-24 by Michael Kerrisk <mtk-manpages@gmx.net>
-.\" Added note on historical rules enforced when an unprivileged process
-.\" sends a signal.
-.\" Modified 2004-06-16 by Michael Kerrisk <mtk-manpages@gmx.net>
-.\" Added note on CAP_KILL
-.\" Modified 2004-06-24 by aeb
-.\" Modified, 2004-11-30, after idea from emmanuel.colbus@ensimag.imag.fr
-.\"
-.TH KILL 2 2004-06-24 "Linux 2.6.7" "Linux Programmer's Manual"
-.SH NAME
-kill \- send signal to a process
-.SH SYNOPSIS
-.nf
-.B #include <sys/types.h>
-.br
-.B #include <signal.h>
-.sp
-.BI "int kill(pid_t " pid ", int " sig );
-.fi
-.SH DESCRIPTION
-The
-.B kill
-system call
-can be used to send any signal to any process group or process.
-.PP
-If \fIpid\fP is positive, then signal \fIsig\fP is sent to \fIpid\fP.
-.PP
-If \fIpid\fP equals 0, then \fIsig\fP is sent to every process in the
-process group of the current process.
-.PP
-If \fIpid\fP equals \-1, then \fIsig\fP is sent to every process
-for which the calling process has permission to send signals,
-except for process 1 (init), but see below.
-.PP
-If \fIpid\fP is less than \-1, then \fIsig\fP is sent to every process
-in the process group \fI\-pid\fP.
-.PP
-If \fIsig\fP is 0, then no signal is sent, but error checking is still
-performed.
-
-For a process to have permission to send a signal
-it must either be privileged (under Linux: have the
-.B CAP_KILL
-capability), or the real or effective
-user ID of the sending process must equal the real or
-saved set-user-ID of the target process.
-In the case of SIGCONT it suffices when the sending and receiving
-processes belong to the same session.
-.SH "RETURN VALUE"
-On success (at least one signal was sent), zero is returned.
-On error, \-1 is returned, and
-.I errno
-is set appropriately.
-.SH ERRORS
-.TP
-.B EINVAL
-An invalid signal was specified.
-.TP
-.B EPERM
-The process does not have permission to send the signal
-to any of the target processes.
-.TP
-.B ESRCH
-The pid or process group does not exist.
-Note that an existing process might be a zombie,
-a process which already committed termination, but
-has not yet been \fBwait()\fPed for.
-.SH NOTES
-The only signals that can be sent task number one, the
-.I init
-process, are those for which
-.I init
-has explicitly installed signal handlers.
-This is done to assure the
-system is not brought down accidentally.
-.LP
-POSIX 1003.1-2001 requires that \fIkill(\-1,sig)\fP send \fIsig\fP
-to all processes that the current process may send signals to,
-except possibly for some implementation-defined system processes.
-Linux allows a process to signal itself, but on Linux the call
-\fIkill(-\1,sig)\fP does not signal the current process.
-.LP
-POSIX 1003.1-2003 requires that if a process sends a signal to itself,
-and that process does not have the signal blocked, and no other thread
-has it unblocked or is waiting for it in \fIsigwait()\fP, at least one
-unblocked signal must be delivered to the sending thread before the
-call of \fIkill()\fP returns.
-.SH "LINUX HISTORY"
-Across different kernel versions, Linux has enforced different rules
-for the permissions required for an unprivileged process
-to send a signal to another process.
-.\" In the 0.* kernels things chopped and changed quite
-.\" a bit - MTK, 24 Jul 02
-In kernels 1.0 to 1.2.2, a signal could be sent if the
-effective user ID of the sender matched that of the receiver,
-or the real user ID of the sender matched that of the receiver.
-From kernel 1.2.3 until 1.3.77, a signal could be sent if the
-effective user ID of the sender matched either the real or effective
-user ID of the receiver.
-The current rules, which conform to POSIX 1003.1-2001, were adopted
-in kernel 1.3.78.
-.SH "CONFORMING TO"
-SVr4, SVID, POSIX.1, X/OPEN, BSD 4.3, POSIX 1003.1-2001
-.SH "SEE ALSO"
-.BR _exit (2),
-.BR killpg (2),
-.BR signal (2),
-.BR sigqueue (2),
-.BR tkill (2),
-.BR exit (3),
-.BR capabilities (7),
-.BR signal (7)
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