Add command sensor

homeassistant/components/sensor/command_sensor.py

@@ -0,0 +1,124 @@
+"""
+homeassistant.components.sensor.command_sensor
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Allows to configure custom shell commands to turn a value for a sensor.
+
+Configuration:
+
+To use the command_line sensor you will need to add something like the
+following to your configuration.yaml file.
+
+sensor:
+  platform: command_sensor
+  name: "Command sensor"
+  command: sensor_command
+  unit_of_measurement: "°C"
+  correction_factor: 0.0001
+
+Variables:
+
+name
+*Optional
+Name of the command sensor.
+
+command
+*Required
+The action to take to get the value.
+
+unit_of_measurement
+*Optional
+Defines the units of measurement of the sensor, if any.
+
+correction_factor
+*Optional
+A float value to do some basic calculations.
+
+For more details about this platform, please refer to the documentation at
+https://home-assistant.io/components/sensor.command_sensor.html
+"""
+import logging
+from subprocess import check_output, CalledProcessError
+from datetime import timedelta
+
+from homeassistant.helpers.entity import Entity
+from homeassistant.util import Throttle
+
+
+_LOGGER = logging.getLogger(__name__)
+
+DEFAULT_NAME = "Command Sensor"
+
+# Return cached results if last scan was less then this time ago
+MIN_TIME_BETWEEN_UPDATES = timedelta(seconds=60)
+
+
+# pylint: disable=unused-argument
+def setup_platform(hass, config, add_devices_callback, discovery_info=None):
+    """ Add the Command Sensor. """
+
+    if config.get('command') is None:
+        _LOGGER.error('Missing required variable: "command"')
+        return False
+
+    data = CommandSensorData(config.get('command'))
+
+    add_devices_callback([CommandSensor(
+        data,
+        config.get('name', DEFAULT_NAME),
+        config.get('unit_of_measurement'),
+        config.get('correction_factor', 1.0)
+    )])
+
+
+class CommandSensor(Entity):
+    """ Represents a sensor that is returning a value of a shell commands. """
+    def __init__(self, data, name, unit_of_measurement, corr_factor):
+        self.data = data
+        self._name = name
+        self._state = False
+        self._unit_of_measurement = unit_of_measurement
+        self._corr_factor = corr_factor
+        self.update()
+
+    @property
+    def name(self):
+        """ The name of the sensor. """
+        return self._name
+
+    @property
+    def unit_of_measurement(self):
+        """ Unit the value is expressed in. """
+        return self._unit_of_measurement
+
+    @property
+    def state(self):
+        """ Returns the state of the device. """
+        return self._state
+
+    def update(self):
+        """ Gets the latest data and updates the state. """
+        self.data.update()
+        value = self.data.value
+
+        if value is not None:
+            self._state = int(round(float(value)) * self._corr_factor)
+
+
+# pylint: disable=too-few-public-methods
+class CommandSensorData(object):
+    """ Class for handling the data retrieval. """
+
+    def __init__(self, command):
+        self.command = command
+        self.value = None
+
+    @Throttle(MIN_TIME_BETWEEN_UPDATES)
+    def update(self):
+        """ Gets the latest data with a shell command. """
+        _LOGGER.info('Running command: %s', self.command)
+
+        try:
+            return_value = check_output(self.command.split())
+            self.value = return_value.strip().decode('utf-8')
+        except CalledProcessError:
+            _LOGGER.error('Command failed: %s', self.command)