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#
# Copyright (c) 2018 Red Hat, Inc.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.
#
"""
Command -- a command which is implemented as an ioctl
$Id: //eng/vdo-releases/magnesium/src/python/vdo/statistics/Command.py#1 $
"""
import fcntl
class Command(object):
"""
Command represents a command which may be sent to a VDO via an ioctl.
Commands have no return data. For ioctls which fetch statistics, use
StatStruct.
"""
def __init__(self, ioctl):
"""
:param ioctl: The numeric value of the ioctl for this command.
"""
self.ioctl = ioctl
def act(self, device):
"""
Send the command to a device.
:param device: The name of the device on which to act.
"""
with open(device, 'r') as fd:
result = fcntl.ioctl(fd, self.ioctl)
if result:
raise Exception("ioctl failed with result {0}".format(result))
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