kill(P)                                                 kill(P)





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 - sig-
              nal_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() ) correspond-
              ing 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  num-
              ber,  the signal_name (the symbolic constant name
              without the SIG prefix defined in the Base  Defi-
              nitions  volume  of  IEEE Std 1003.1-2001) corre-
              sponding to that signal shall be written.  Other-
              wise, the results are unspecified.

       -s  signal_name

              Specify the signal to send, using one of the sym-
              bolic 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,  sig-
              nal_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 nega-
       tive pid operand specifying a process group.

OPERANDS
       The following operands shall be supported:

       pid    One of the following:

       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 cur-
       rent 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 preceded
       by  "--" to keep it from being interpreted as an option.

       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  sig-
       naled.  The  job  control  job ID notation is applicable
       only for invocations of kill in the current shell execu-
       tion environment; see Shell Execution Environment .

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


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 internationaliza-
              tion  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 cate-
              gories.)

       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 mes-
              sages written 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 <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
       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 suc-
              cessfully 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 exam-
       ples:


              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  spe-
       cific  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  termi-
       nal  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 for-
       mat 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  sig-
       nal_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
       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 sig-
       nal_names.  Since  neither  applications portability nor
       ease-of-use would be improved by requiring  this  exten-
       sion, 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 appli-
       cations 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  exam-
       ples:


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

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

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell Command Language , ps , wait() , the System Inter-
       faces volume of IEEE Std 1003.1-2001, kill(),  the  Base
       Definitions 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,
       Standard  for Information Technology -- Portable Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute 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.open-
       group.org/unix/online.html .



POSIX                         2003                      kill(P)
