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Name

kill - terminate a process

Synopsis

kill [-signal|-s signal|-p] [-q value] [-a] [--] pid|name...
kill -l [number] | -L

Description

The command kill sends the specified signal to the specified processes or process groups. If no signal is specified, the TERM signal is sent. This TERM signal will kill processes that do not catch it; for other processes it may be necessary to use the KILL signal (number 9), since this signal cannot be caught.

Most modern shells have a builtin kill function, with a usage rather similar to that of the command described here. The --all, --pid, and --queue options, and the possibility to specify processes by command name, are local extensions.

If signal is 0, then no actual signal is sent, but error checking is still performed.

Arguments

The list of processes to be signaled can be a mixture of names and pids.
pid
Each pid can be one of four things:
n
where n is larger than 0. The process with pid n is signaled.
  • All processes in the current process group are signaled.
    • -1
    All processes with a pid larger than 1 are signaled.
    -n
    where n is larger than 1. All processes in process group n are signaled. When an argument of the form ’-n’ is given, and it is meant to denote a process group, either a signal must be specified first, or the argument must be preceded by a ’--’ option, otherwise it will be taken as the signal to send.
    name
    All processes invoked using this name will be signaled.

    Options

    -s, --signal signal
    The signal to send. It may be given as a name or a number.
    -l, --list [number]
    Print a list of signal names, or convert the given signal number to a name. The signals can be found in /usr/:include/:linux/:signal.h
    -L, --table
    Similar to -l, but it will print signal names and their corresponding numbers.
    -a, --all
    Do not restrict the commandname-to-pid conversion to processes with the same uid as the present process.
    -p, --pid
    Only print the process id (pid) of the named processes, do not send any signals.
    The --pid option is automatically enabled when the kill command
    is invoked with the name of pid. This functionality is deprecated, and will be removed in March 2016.
    -q, --queue value
    Use sigqueue(2) rather than kill(2) . The value argument is an integer that is sent along with the signal. If the receiving process has installed a handler for this signal using the SA_SIGINFO flag to sigaction(2) , then it can obtain this data via the si_sigval field of the siginfo_t structure.

    Notes

    It is not possible to send a signal to an explicitly selected thread in a multithreaded process using the kill(2) syscall. If kill(2) is used to send a signal to a thread group, then the kernel selects an arbitrary member of the thread group that has not blocked the signal. For more details see clone(2) , the CLONE_THREAD description.

    The command kill(1) as well as syscall kill(2) accept a TID (thread ID, see gettid(2) ) as an argument. In this case the kill behavior is not changed and the signal is also delivered to the thread group rather than to the specified thread.

    Return Codes

    kill has the following return codes:
    1. success
    2. failure
    3. partial success (when more than one process specified)

    See Also

    bash(1) , tcsh(1) , kill(2) , sigvec(2) , signal(7)

    Authors

    Salvatore Valente
    Karel Zak

    The original version was taken from BSD 4.4.

    Availability

    The kill command is part of the util-linux package and is available from Linux Kernel Archive

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