.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "KILL" P 2003 POSIX
.\" kill 
.SH NAME
kill \- terminate or signal processes
.SH SYNOPSIS
.LP
\fBkill -s\fP \fIsignal_name pid\fP \fB...
.br
.sp
kill -l\fP \fB[\fP\fIexit_status\fP\fB]\fP\fB
.br
.sp
\fP
.LP
\fBkill\fP \fB[\fP\fB-\fP\fIsignal_name\fP\fB]\fP \fIpid\fP \fB...
.br
.sp
kill\fP \fB[\fP\fB-\fP\fIsignal_number\fP\fB]\fP \fIpid\fP \fB...
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIkill\fP utility shall send a signal to the process or processes
specified by each \fIpid\fP operand.
.LP
For each \fIpid\fP operand, the \fIkill\fP utility shall perform actions
equivalent to the \fIkill\fP() function defined in the System Interfaces
volume of IEEE\ Std\ 1003.1-2001
called with the following arguments:
.IP " *" 3
The value of the \fIpid\fP operand shall be used as the \fIpid\fP
argument.
.LP
.IP " *" 3
The \fIsig\fP argument is the value specified by the \fB-s\fP option,
\fB-\fP \fIsignal_number\fP option, or the \fB-\fP
\fIsignal_name\fP option, or by SIGTERM, if none of these options
is specified.
.LP
.SH OPTIONS
.LP
The \fIkill\fP utility shall conform to the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines,
\ except that
in the last two SYNOPSIS forms, the \fB-\fP \fIsignal_number\fP and
\fB-\fP \fIsignal_name\fP options are usually more than a
single character. 
.LP
The following options shall be supported:
.TP 7
\fB-l\fP
(The letter ell.) Write all values of \fIsignal_name\fP supported
by the implementation, if no operand is given. If an
\fIexit_status\fP operand is given and it is a value of the \fB'?'\fP
shell special parameter (see \fISpecial Parameters\fP and \fIwait\fP()
) corresponding to a process
that was terminated by a signal, the \fIsignal_name\fP corresponding
to the signal that terminated the process shall be written.
If an \fIexit_status\fP operand is given and it is the unsigned decimal
integer value of a signal number, the \fIsignal_name\fP
(the symbolic constant name without the \fBSIG\fP prefix defined in
the Base Definitions volume of IEEE\ Std\ 1003.1-2001)
corresponding to that signal shall be written. Otherwise, the results
are unspecified.
.TP 7
\fB-s\ \fP \fIsignal_name\fP
.sp
Specify the signal to send, using one of the symbolic names defined
in the \fI<signal.h>\fP header. Values of \fIsignal_name\fP shall
be recognized in a
case-independent fashion, without the \fBSIG\fP prefix. In addition,
the symbolic name 0 shall be recognized, representing the
signal value zero. The corresponding signal shall be sent instead
of SIGTERM.
.TP 7
\fB-\fP\fIsignal_name\fP
.sp
Equivalent to \fB-s\fP \fIsignal_name\fP. 
.TP 7
\fB-\fP\fIsignal_number\fP
.sp
Specify a non-negative decimal integer, \fIsignal_number\fP, representing
the signal to be used instead of SIGTERM, as the
\fIsig\fP argument in the effective call to \fIkill\fP(). The correspondence
between integer
values and the \fIsig\fP value used is shown in the following table.
.LP
The effects of specifying any \fIsignal_number\fP other than those
listed in the table are undefined. 
.sp
.sp
.TS C
center; l l.
\fIsignal_number\fP	\fB\fIsig\fP Value\fP
0	0
1	SIGHUP
2	SIGINT
3	SIGQUIT
6	SIGABRT
9	SIGKILL
14	SIGALRM
15	SIGTERM
.TE
.LP
If the first argument is a negative integer, it shall be interpreted
as a \fB-\fP \fIsignal_number\fP option, not as a
negative \fIpid\fP operand specifying a process group. 
.SH OPERANDS
.LP
The following operands shall be supported:
.TP 7
\fIpid\fP
One of the following: 
.RS
.IP " 1." 4
A decimal integer specifying a process or process group to be signaled.
The process or processes selected by positive, negative,
and zero values of the \fIpid\fP operand shall be as described for
the \fIkill\fP()
function. If process number 0 is specified, all processes in the current
process group shall be signaled. For the effects of
negative \fIpid\fP numbers, see the \fIkill\fP() function defined
in the System Interfaces
volume of IEEE\ Std\ 1003.1-2001. If the first \fIpid\fP operand is
negative, it should be preceded by \fB"--"\fP to
keep it from being interpreted as an option.
.LP
.IP " 2." 4
A job control job ID (see the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
Section 3.203, Job Control Job ID) that identifies a background process
group to be
signaled. The job control job ID notation is applicable only for invocations
of \fIkill\fP in the current shell execution
environment; see \fIShell Execution Environment\fP .
.LP
.RE
.TP 7
\fIexit_status\fP
A decimal integer specifying a signal number or the exit status of
a process terminated by a signal.
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fIkill\fP:
.TP 7
\fILANG\fP
Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
for
the precedence of internationalization variables used to determine
the values of locale categories.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
When the \fB-l\fP option is not specified, the standard output shall
not be used.
.LP
When the \fB-l\fP option is specified, the symbolic name of each signal
shall be written in the following format:
.sp
.RS
.nf

\fB"%s%c", <\fP\fIsignal_name\fP\fB>, <\fP\fIseparator\fP\fB>
\fP
.fi
.RE
.LP
where the <\fIsignal_name\fP> is in uppercase, without the \fBSIG\fP
prefix, and the <\fIseparator\fP> shall be
either a <newline> or a <space>. For the last signal written, <\fIseparator\fP>
shall be a <newline>.
.LP
When both the \fB-l\fP option and \fIexit_status\fP operand are specified,
the symbolic name of the corresponding signal shall
be written in the following format:
.sp
.RS
.nf

\fB"%s\\n", <\fP\fIsignal_name\fP\fB>
\fP
.fi
.RE
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
At least one matching process was found for each \fIpid\fP operand,
and the specified signal was successfully processed for at
least one matching process.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
Process numbers can be found by using \fIps\fP.
.LP
The job control job ID notation is not required to work as expected
when \fIkill\fP is operating in its own utility execution
environment. In either of the following examples:
.sp
.RS
.nf

\fBnohup kill %1 &
system("kill %1");
\fP
.fi
.RE
.LP
the \fIkill\fP operates in a different environment and does not share
the shell's understanding of job numbers.
.SH EXAMPLES
.LP
Any of the commands:
.sp
.RS
.nf

\fBkill -9 100 -165
kill -s kill 100 -165
kill -s KILL 100 -165
\fP
.fi
.RE
.LP
sends the SIGKILL signal to the process whose process ID is 100 and
to all processes whose process group ID is 165, assuming the
sending process has permission to send that signal to the specified
processes, and that they exist.
.LP
The System Interfaces volume of IEEE\ Std\ 1003.1-2001 and this volume
of IEEE\ Std\ 1003.1-2001 do not require
specific signal numbers for any \fIsignal_names\fP. Even the \fB-\fP
\fIsignal_number\fP option provides symbolic (although
numeric) names for signals. If a process is terminated by a signal,
its exit status indicates the signal that killed it, but the
exact values are not specified. The \fIkill\fP \fB-l\fP option, however,
can be used to map decimal signal numbers and exit
status values into the name of a signal. The following example reports
the status of a terminated job:
.sp
.RS
.nf

\fBjob
stat=$?
if [ $stat -eq 0 ]
then
    echo job completed successfully.
elif [ $stat -gt 128 ]
then
    echo job terminated by signal SIG$(kill -l $stat).
else
    echo job terminated with error code $stat.
fi
\fP
.fi
.RE
.LP
To send the default signal to a process group (say 123), an application
should use a command similar to one of the
following:
.sp
.RS
.nf

\fBkill -TERM -123
kill -- -123
\fP
.fi
.RE
.SH RATIONALE
.LP
The \fB-l\fP option originated from the C shell, and is also implemented
in the KornShell. The C shell output can consist of
multiple output lines because the signal names do not always fit on
a single line on some terminal screens. The KornShell output
also included the implementation-defined signal numbers and was considered
by the standard developers to be too difficult for
scripts to parse conveniently. The specified output format is intended
not only to accommodate the historical C shell output, but
also to permit an entirely vertical or entirely horizontal listing
on systems for which this is appropriate.
.LP
An early proposal invented the name SIGNULL as a \fIsignal_name\fP
for signal 0 (used by the System Interfaces volume of
IEEE\ Std\ 1003.1-2001 to test for the existence of a process without
sending it a signal). Since the \fIsignal_name\fP 0
can be used in this case unambiguously, SIGNULL has been removed.
.LP
An early proposal also required symbolic \fIsignal_name\fPs to be
recognized with or without the \fBSIG\fP prefix. Historical
versions of \fIkill\fP have not written the \fBSIG\fP prefix for the
\fB-l\fP option and have not recognized the \fBSIG\fP
prefix on \fIsignal_name\fPs. Since neither applications portability
nor ease-of-use would be improved by requiring this
extension, it is no longer required.
.LP
To avoid an ambiguity of an initial negative number argument specifying
either a signal number or a process group,
IEEE\ Std\ 1003.1-2001 mandates that it is always considered the former
by implementations that support the XSI option. It
also requires that conforming applications always use the \fB"--"\fP
options terminator argument when specifying a process
group, unless an option is also specified.
.LP
The \fB-s\fP option was added in response to international interest
in providing some form of \fIkill\fP that meets the
Utility Syntax Guidelines.
.LP
The job control job ID notation is not required to work as expected
when \fIkill\fP is operating in its own utility execution
environment. In either of the following examples:
.sp
.RS
.nf

\fBnohup kill %1 &
system("kill %1");
\fP
.fi
.RE
.LP
the \fIkill\fP operates in a different environment and does not understand
how the shell has managed its job numbers.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIShell Command Language\fP , \fIps\fP , \fIwait\fP() , the System
Interfaces volume of IEEE\ Std\ 1003.1-2001, \fIkill\fP(), the Base
Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<signal.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .