Kill processes matching a pattern.

    .. code-block:: bash

        salt '*' ps.pkill pattern [user=username] [signal=signal_number] \\
                [full=(true|false)]

    pattern
        Pattern to search for in the process list.

    user
        Limit matches to the given username. Default: All users.

    signal
        Signal to send to the process(es). See manpage entry for kill
        for possible values. Default: 15 (SIGTERM).

    full
        A boolean value indicating whether only the name of the command or
        the full command line should be matched against the pattern.

    **Examples:**

    Send SIGHUP to all httpd processes on all 'www' minions:

    .. code-block:: bash

        salt 'www.*' ps.pkill httpd signal=1

    Send SIGKILL to all bash processes owned by user 'tom':

    .. code-block:: bash

        salt '*' ps.pkill bash signal=9 user=tom

def pkill(pattern, user=None, signal=15, full=False):
    '''
    Kill processes matching a pattern.

    .. code-block:: bash

        salt '*' ps.pkill pattern [user=username] [signal=signal_number] \\
                [full=(true|false)]

    pattern
        Pattern to search for in the process list.

    user
        Limit matches to the given username. Default: All users.

    signal
        Signal to send to the process(es). See manpage entry for kill
        for possible values. Default: 15 (SIGTERM).

    full
        A boolean value indicating whether only the name of the command or
        the full command line should be matched against the pattern.

    **Examples:**

    Send SIGHUP to all httpd processes on all 'www' minions:

    .. code-block:: bash

        salt 'www.*' ps.pkill httpd signal=1

    Send SIGKILL to all bash processes owned by user 'tom':

    .. code-block:: bash

        salt '*' ps.pkill bash signal=9 user=tom
    '''

    killed = []
    for proc in psutil.process_iter():
        name_match = pattern in ' '.join(_get_proc_cmdline(proc)) if full \
            else pattern in _get_proc_name(proc)
        user_match = True if user is None else user == _get_proc_username(proc)
        if name_match and user_match:
            try:
                proc.send_signal(signal)
                killed.append(_get_proc_pid(proc))
            except psutil.NoSuchProcess:
                pass
    if not killed:
        return None
    else:
        return {'killed': killed}