PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

KILL(1P)                  POSIX Programmer's Manual                 KILL(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       kill — terminate or signal processes

SYNOPSIS         top

       kill −s signal_name pid...

       kill −l [exit_status]

       kill [signal_name] pid...

       kill [signal_number] pid...

DESCRIPTION         top

       The kill utility shall send a signal to the process or processes
       specified by each pid operand.

       For each pid operand, the kill utility shall perform actions
       equivalent to the kill() function defined in the System Interfaces
       volume of POSIX.1‐2008 called with the following arguments:

        *  The value of the pid operand shall be used as the pid argument.

        *  The sig argument is the value specified by the −s option,
           signal_number option, or the signal_name option, or by SIGTERM,
           if none of these options is specified.

OPTIONS         top

       The kill utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that in
       the last two SYNOPSIS forms, the signal_number and signal_name
       options are usually more than a single character.

       The following options shall be supported:

       −l        (The letter ell.) Write all values of signal_name supported
                 by the implementation, if no operand is given. If an
                 exit_status operand is given and it is a value of the '?'
                 shell special parameter (see Section 2.5.2, Special
                 Parameters and wait) corresponding to a process that was
                 terminated by a signal, the signal_name corresponding to
                 the signal that terminated the process shall be written. If
                 an exit_status operand is given and it is the unsigned
                 decimal integer value of a signal number, the signal_name
                 (the symbolic constant name without the SIG prefix defined
                 in the Base Definitions volume of POSIX.1‐2008)
                 corresponding to that signal shall be written. Otherwise,
                 the results are unspecified.

       −s signal_name
                 Specify the signal to send, using one of the symbolic names
                 defined in the <signal.h> header. Values of signal_name
                 shall be recognized in a case-independent fashion, without
                 the SIG prefix. In addition, the symbolic name 0 shall be
                 recognized, representing the signal value zero. The
                 corresponding signal shall be sent instead of SIGTERM.

       signal_name
                 Equivalent to −s signal_name.

       signal_number
                 Specify a non-negative decimal integer, signal_number,
                 representing the signal to be used instead of SIGTERM, as
                 the sig argument in the effective call to kill().  The
                 correspondence between integer values and the sig value
                 used is shown in the following list.

                 The effects of specifying any signal_number other than
                 those listed below are undefined.

                 0     0

                 1     SIGHUP

                 2     SIGINT

                 3     SIGQUIT

                 6     SIGABRT

                 9     SIGKILL

                 14    SIGALRM

                 15    SIGTERM

                 If the first argument is a negative integer, it shall be
                 interpreted as a signal_number option, not as a negative
                 pid operand specifying a process group.

OPERANDS         top

       The following operands shall be supported:

       pid       One of the following:

                  1. 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 pid operand
                     shall be as described for the kill() function. If
                     process number 0 is specified, all processes in the
                     current process group shall be signaled. For the
                     effects of negative pid numbers, see the kill()
                     function defined in the System Interfaces volume of
                     POSIX.1‐2008. If the first pid operand is negative, it
                     should be preceded by "−−" to keep it from being
                     interpreted as an option.

                  2. A job control job ID (see the Base Definitions volume
                     of POSIX.1‐2008, Section 3.204, 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 kill in the current shell
                     execution environment; see Section 2.12, Shell
                     Execution Environment.

       exit_status
                 A decimal integer specifying a signal number or the exit
                 status of a process terminated by a signal.

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       The following environment variables shall affect the execution of
       kill:

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1‐2008, Section 8.2, Internationalization
                 Variables for the precedence of internationalization
                 variables used to determine the values of locale
                 categories.)

       LC_ALL    If set to a non-empty string value, override the values of
                 all the other internationalization variables.

       LC_CTYPE  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).

       LC_MESSAGES
                 Determine the locale that should be used to affect the
                 format and contents of diagnostic messages written to
                 standard error.

       NLSPATH   Determine the location of message catalogs for the
                 processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       When the −l option is not specified, the standard output shall not be
       used.

       When the −l option is specified, the symbolic name of each signal
       shall be written in the following format:

           "%s%c", <signal_name>, <separator>

       where the <signal_name> is in uppercase, without the SIG prefix, and
       the <separator> shall be either a <newline> or a <space>.  For the
       last signal written, <separator> shall be a <newline>.

       When both the −l option and exit_status operand are specified, the
       symbolic name of the corresponding signal shall be written in the
       following format:

           "%s\n", <signal_name>

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    At least one matching process was found for each pid operand,
             and the specified signal was successfully processed for at
             least one matching process.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       Process numbers can be found by using ps.

       The job control job ID notation is not required to work as expected
       when kill is operating in its own utility execution environment. In
       either of the following examples:

           nohup kill %1 &
           system("kill %1");

       the kill operates in a different environment and does not share the
       shell's understanding of job numbers.

EXAMPLES         top

       Any of the commands:

           kill −9 100 −165
           kill −s kill 100 −165
           kill −s KILL 100 −165

       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.

       The System Interfaces volume of POSIX.1‐2008 and this volume of
       POSIX.1‐2008 do not require specific signal numbers for any
       signal_names.  Even the signal_number 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 kill −l 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:

           job
           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

       To send the default signal to a process group (say 123), an
       application should use a command similar to one of the following:

           kill −TERM −123
           kill −− −123

RATIONALE         top

       The −l 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.

       An early proposal invented the name SIGNULL as a signal_name for
       signal 0 (used by the System Interfaces volume of POSIX.1‐2008 to
       test for the existence of a process without sending it a signal).
       Since the signal_name 0 can be used in this case unambiguously,
       SIGNULL has been removed.

       An early proposal also required symbolic signal_names to be
       recognized with or without the SIG prefix. Historical versions of
       kill have not written the SIG prefix for the −l option and have not
       recognized the SIG prefix on signal_names.  Since neither
       applications portability nor ease-of-use would be improved by
       requiring this extension, it is no longer required.

       To avoid an ambiguity of an initial negative number argument
       specifying either a signal number or a process group, POSIX.1‐2008
       mandates that it is always considered the former by implementations
       that support the XSI option. It also requires that conforming
       applications always use the "−−" options terminator argument when
       specifying a process group, unless an option is also specified.

       The −s option was added in response to international interest in
       providing some form of kill that meets the Utility Syntax Guidelines.

       The job control job ID notation is not required to work as expected
       when kill is operating in its own utility execution environment. In
       either of the following examples:

           nohup kill %1 &
           system("kill %1");

       the kill operates in a different environment and does not understand
       how the shell has managed its job numbers.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Chapter 2, Shell Command Language, ps(1p), wait(1p)

       The Base Definitions volume of POSIX.1‐2008, Section 3.204, Job
       Control Job ID, Chapter 8, Environment Variables, Section 12.2,
       Utility Syntax Guidelines, signal.h(0p)

       The System Interfaces volume of POSIX.1‐2008, kill(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                            KILL(1P)