The kill utility sends a signal to the process or processes specified by each pid operand.
For each pid operand, the kill utility will perform actions equivalent to the kill(2) function called with the following arguments:
The value of the pid operand will be used as the pid argument.
The sig argument is the value specified by the -s option, the -signal_name option, or the -signal_number option, or, if none of these options is specified, by
The signaled process must belong to the current user unless the user is the super-user.
See NOTES for descriptions of the shell built-in versions of kill.
The following options are supported:
(The letter ell.) Writes 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 and wait corresponding to a process that was terminated by a signal, the signal_name corresponding to the signal that terminated the process will be written. If an exit_status operand is given and it is the unsigned decimal integer value of a signal number, the signal_name corresponding to that signal will be written. Otherwise, the results are unspecified.
Specifies the signal to send, using one of the symbolic names defined in the <signal.h> description. Values of signal_name will be recognized in a case-independent fashion, without the SIG prefix. In addition, the symbolic name 0 will be recognized, representing the signal value zero. The corresponding
signal will be sent instead of
Equivalent to -s signal_name.
Specifies 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(2).
The following operands are supported:
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 will be as described for the kill function. If process number 0 is specified, all processes in the process group are signaled. 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 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.
Note: The job control job ID type of pid is available only on systems supporting the job control option.
A decimal integer specifying a signal number or the exit status of a process terminated by a signal.
Process numbers can be found by using ps(1).
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:
example% nohup kill %1 & example% system( "kill %1");
kill operates in a different environment and will not share the shell's understanding of job numbers.
When the -l option is not specified, the standard output will not be used.
When the -l option is specified, the symbolic name of each signal will be written in the following format:
"%s%c", <signal_name>, <separator>
where the <signal_name> is in upper-case, without the SIG prefix, and the <separator> will be either a newline character or a space character. For the last signal written, <separator> will be a newline character.
When both the -l option and exit_status operand are specified, the symbolic name of the corresponding signal will be written in the following format:
Any of the commands:
example% kill -9 100 -165 example% kill -s kill 100 -165 example% kill -s KILL 100 -165
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.
To avoid an ambiguity of an initial negative number argument specifying either a signal number or a process group, the former will always be the case. Therefore, to send the default signal to a process group (for example, 123), an application should use a command similar to one of the following:
example% kill -TERM -123 example% kill -- -123
See environ(5) for descriptions of the following environment variables that affect the execution of kill: LC_CTYPE, LC_MESSAGES, and NLSPATH.
The following exit values are returned:
At least one matching process was found for each pid operand, and the specified signal was successfully processed for at least one matching process.
An error occurred.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
The Bourne shell, sh, has a built-in version of kill to provide the functionality of the kill command for processes identified with a jobid. The sh syntax is:
kill [ -sig ] [ pid ] [ %job ]... kill -l
The C-shell, csh, also has a built-in kill command, whose syntax is:
kill [-sig][pid][%job]... kill -l
The csh kill built-in sends the
TERM (terminate) signal, by default, or the signal specified, to the specified process ID, the job indicated, or the current job. Signals are either given by number or by name. There is no default. Typing kill does not send a signal to the current job. If the signal being sent
TERM (terminate) or
HUP (hangup), then the job or process is sent a
CONT (continue) signal as well.
Lists the signal names that can be sent.
The syntax of the ksh kill is:
kill [-sig][pid][%job]... kill -l
The ksh kill sends either the
TERM (terminate) signal or the specified signal to the specified jobs or processes. Signals are either given by number or by names (as given in signal(3HEAD) stripped of the SIG prefix). If the signal being sent is
TERM (terminate) or
HUP (hangup), then the job or process will be sent a
CONT (continue) signal if it is stopped. The argument job can be the process id of a process that is not a member of one of the active jobs. In the second form, kill -l, the signal numbers and names are listed.