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



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

NAME
       kill - terminate or signal processes

SYNOPSIS
       kill -s signal_name pid ...

       kill -l [exit_status]



       kill [-signal_name] pid ...

       kill [-signal_number] pid ...


DESCRIPTION
       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 IEEE Std 1003.1-2001 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
       The  kill  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 - 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
              Special  Parameters  and  wait()  ) corresponding to a process that was terminated by a signal, the sig-
              nal_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
              IEEE Std 1003.1-2001) corresponding to that signal shall be written. Otherwise, the results are unspeci-
              fied.

       -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 table.

       The effects of specifying any signal_number other than those listed in the table are undefined.



                                                  signal_number   sig Value
                                                  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 neg-
       ative pid operand specifying a process group.

OPERANDS
       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 IEEE Std 1003.1-2001. If the first pid operand is negative, it should  be  pre-
                  ceded by "--" to keep it from being interpreted as an option.


               2. 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 kill in the current shell execution environment; see
                  Shell Execution Environment .


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


STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       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 IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the prece-
              dence 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 exam-
              ple, 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  writ-
              ten to standard error.

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


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       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 <new-
       line> 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
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       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
       Default.

       The following sections are informative.

APPLICATION USAGE
       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
       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 IEEE Std 1003.1-2001 and this volume of IEEE Std 1003.1-2001 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 sig-
       nal  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
       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  IEEE Std 1003.1-2001  to  test  for the existence of a process without sending it a signal). Since the sig-
       nal_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. Histori-
       cal  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, 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 "--" 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
       None.

SEE ALSO
       Shell Command Language, ps, wait(), the System Interfaces volume of IEEE Std 1003.1-2001, kill(), the Base Def-
       initions volume of IEEE Std 1003.1-2001, <signal.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  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 .



IEEE/The Open Group                  2003                             KILL(1P)