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