misc-utils/kill.1

   1 .\" Copyright 1994 Salvatore Valente (svalente@mit.edu)
   2 .\" Copyright 1992 Rickard E. Faith (faith@cs.unc.edu)
   3 .\" May be distributed under the GNU General Public License
   4 .TH KILL 1 "November 2019" "util-linux" "User Commands"
   5 .SH NAME
   6 kill \- terminate a process
   7 .SH SYNOPSIS
   8 .B kill
   9 .RB [ \- \fIsignal\fR| \-s
  10 .IR signal | \fB\-p\fP ]
  11 .RB [ \-q
  12 .IR value ]
  13 .RB [ \-a ]
  14 \fR[\fB\-\-timeout \fImilliseconds signal\fR]
  15 .RB [ \-\- ]
  16 .IR pid | name ...
  17 .br
  18 .B kill \-l
  19 .RI [ number ]
  20 .RB "| " \-L
  21 .SH DESCRIPTION
  22 The command
  23 .B kill
  24 sends the specified \fIsignal\fR to the specified processes or process groups.
  25 .PP
  26 If no signal is specified, the TERM signal is sent.
  27 The default action for this signal is to terminate the process.
  28 This signal should be used in preference to the
  29 KILL signal (number 9), since a process may install a handler for the
  30 TERM signal in order to perform clean-up steps before terminating in
  31 an orderly fashion.
  32 If a process does not terminate after a TERM signal has been sent,
  33 then the KILL signal may be used; be aware that the latter signal
  34 cannot be caught, and so does not give the target process the opportunity
  35 to perform any clean-up before terminating.
  36 .PP
  37 Most modern shells have a builtin
  38 .B kill
  39 command, with a usage rather similar to
  40 that of the command described here.  The
  41 .BR \-\-all ,
  42 .BR \-\-pid ", and"
  43 .B \-\-queue
  44 options, and the possibility to specify processes by command name, are local extensions.
  45 .PP
  46 If \fIsignal\fR is 0, then no actual signal is sent, but error checking is still performed.
  47
  48 .SH ARGUMENTS
  49 The list of processes to be signaled can be a mixture of names and PIDs.
  50 .TP
  51 .I pid
  52 Each
  53 .I pid
  54 can be expressed in one of the following ways:
  55 .RS
  56 .TP
  57 .I n
  58 where
  59 .I n
  60 is larger than 0.  The process with PID
  61 .I n
  62 is signaled.
  63 .TP
  64 .B 0
  65 All processes in the current process group are signaled.
  66 .TP
  67 .B \-1
  68 All processes with a PID larger than 1 are signaled.
  69 .TP
  70 .BI \- n
  71 where
  72 .I n
  73 is larger than 1.  All processes in process group
  74 .I n
  75 are signaled.  When an argument of the form '\-n' is given, and it is meant to
  76 denote a process group, either a signal must be specified first, or the
  77 argument must be preceded by a '\-\-' option, otherwise it will be taken as the
  78 signal to send.
  79 .RE
  80 .TP
  81 .I name
  82 All processes invoked using this \fIname\fR will be signaled.
  83
  84 .SH OPTIONS
  85 .TP
  86 \fB\-s\fR, \fB\-\-signal\fR \fIsignal\fR
  87 The signal to send.  It may be given as a name or a number.
  88 .TP
  89 \fB\-l\fR, \fB\-\-list\fR [\fInumber\fR]
  90 Print a list of signal names, or convert the given signal number to a name.
  91 The signals can be found in
  92 .IR /usr/\:include/\:linux/\:signal.h .
  93 .TP
  94 \fB\-L\fR, \fB\-\-table\fR
  95 Similar to \fB\-l\fR, but it will print signal names and their corresponding
  96 numbers.
  97 .TP
  98 \fB\-a\fR, \fB\-\-all\fR
  99 Do not restrict the command-name-to-PID conversion to processes with the same
 100 UID as the present process.
 101 .TP
 102 \fB\-p\fR, \fB\-\-pid\fR
 103 Only print the process ID (PID) of the named processes, do not send any
 104 signals.
 105 .TP
 106 \fB\-\-verbose\fR
 107 Print PID(s) that will be signaled with
 108 .B kill
 109 along with the signal.
 110 .TP
 111 \fB\-q\fR, \fB\-\-queue\fR \fIvalue\fR
 112 Send the signal using
 113 .BR sigqueue (3)
 114 rather than
 115 .BR kill (2).
 116 The
 117 .I value
 118 argument is an integer that is sent along with the signal.  If the
 119 receiving process has installed a handler for this signal using the
 120 .B SA_SIGINFO
 121 flag to
 122 .BR sigaction (2),
 123 then it can obtain this data via the
 124 .I si_sigval
 125 field of the
 126 .I siginfo_t
 127 structure.
 128 .TP
 129 \fB\-\-timeout\fR \fImilliseconds signal\fR
 130 Send a signal defined the usual way to a process.
 131 .B \-\-timeout
 132 will make
 133 .B kill
 134 to wait for a period defined in
 135 .I milliseconds
 136 before sending follow-up
 137 .I signal
 138 to process.
 139 This feature is implemented by PID file-descriptor and guarantees that
 140 follow-up signals are sent to the same process or not sent if the process no
 141 more exist.  Note that the operating system may re-use PIDs and implement the
 142 same feature in a shell by kill and sleep commands sequence may introduce a
 143 race.  This option can be specified more than once than signals are sent
 144 sequentially in defined timeouts.  The
 145 .B \-\-timeout
 146 option can be combined with
 147 .B \-\-queue
 148 option.
 149 .IP
 150 Example.  Send signals QUIT, TERM and KILL in sequence and wait for 1000
 151 milliseconds between the signals
 152 .br
 153 kill \-\-verbose \-\-timeout 1000 TERM \-\-timeout 1000 KILL \-\-signal QUIT 12345
 154 .SH EXIT STATUS
 155 .B kill
 156 has the following exit status values:
 157 .PP
 158 .RS
 159 .PD 0
 160 .TP
 161 .B 0
 162 success
 163 .TP
 164 .B 1
 165 failure
 166 .TP
 167 .B 64
 168 partial success (when more than one process specified)
 169 .PD
 170 .RE
 171 .SH NOTES
 172 Although it is possible to specify the TID (thread ID, see
 173 .BR gettid (2))
 174 of one of the threads in a multithreaded process as the argument of
 175 .BR kill ,
 176 the signal is nevertheless directed to the process
 177 (i.e., the entire thread group).
 178 In other words, it is not possible to send a signal to an
 179 explicitly selected thread in a multithreaded process.
 180 The signal will be delivered to an arbitrarily selected thread
 181 in the target process that is not blocking the signal.
 182 For more details, see
 183 .BR signal (7)
 184 and the description of
 185 .B CLONE_THREAD
 186 in
 187 .BR clone (2).
 188 .P
 189 Various shells provide a builtin
 190 .B kill
 191 command that is
 192 preferred in relation to the
 193 .BR kill (1)
 194 executable described by this manual.
 195 The easiest way to ensure one is executing the command described in this page
 196 is to use the full path when calling the command, for example:
 197 .B "/bin/kill \-\-version"
 198 .SH AUTHORS
 199 .MT svalente@mit.edu
 200 Salvatore Valente
 201 .ME
 202 .br
 203 .MT kzak@redhat.com
 204 Karel Zak
 205 .ME
 206 .br
 207 .PP
 208 The original version was taken from BSD 4.4.
 209
 210 .SH SEE ALSO
 211 .BR bash (1),
 212 .BR tcsh (1),
 213 .BR sigaction (2),
 214 .BR kill (2),
 215 .BR sigqueue (3),
 216 .BR signal (7)
 217
 218 .SH AVAILABILITY
 219 The kill command is part of the util-linux package and is available from
 220 .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 221 Linux Kernel Archive
 222 .UE .