Checking the Battery’s Status via the Terminal

1. Introduction

Depending on the desktop environment of the Linux distribution we are using, we may or may not have a battery status indicator on the desktop. Sometimes, we may have to check the battery status using the command line.

In this tutorial, we’ll look at some ways to check the battery status (charging status and power percentage) using commands.

2. Using upower

upower is a command-line client for the UPower daemon, which is responsible for system-wide power management on most Linux distributions. Before we use this command to obtain the information about the battery, we need to figure out the path for the connected battery. This can be done using upower -e or upower –enumerate:

$ upower -e
/org/freedesktop/UPower/devices/line_power_AC
/org/freedesktop/UPower/devices/battery_BAT0
/org/freedesktop/UPower/devices/DisplayDevice

The second line, where the device name starts with “battery..”, is the one we are looking for. It’s usually battery_BAT0 or battery_BAT1, depending on the distribution we’re using.

Once we have this path, we can proceed to get detailed information about the battery using upower -i:

$ upower -i /org/freedesktop/UPower/devices/battery_BAT0
  native-path:          BAT0
  vendor:               LGC-LGC3.0
  model:                DELL 49VTP27
  serial:               14057
  power supply:         yes
  updated:              Monday 18 April 2022 07:45:28 AM (105 seconds ago)
  has history:          yes
  has statistics:       yes
  battery
    present:             yes
    rechargeable:        yes
    state:               charging
    warning-level:       none
    energy:              53.5464 Wh
    energy-empty:        0 Wh
    energy-full:         57.3981 Wh
    energy-full-design:  48.84 Wh
    energy-rate:         2.4531 W
    voltage:             12.564 V
    time to full:        1.6 hours
    percentage:          93%
    capacity:            100%
    technology:          lithium-ion
    icon-name:          'battery-full-charging-symbolic'
  History (rate):
    1650248128	2.453	charging

Needless to say, we can use grep or other commands to process the output into a format we need:

$ upower -i /org/freedesktop/UPower/devices/battery_BAT0 | grep percentage | grep -o "[0-9]*"
93
$ upower -i /org/freedesktop/UPower/devices/battery_BAT0 | grep state | cut -d ':' -f2 | xargs
charging

These days, most devices have only a single battery, so we can also use the upower command with the -d parameter. This essentially prints information for all the connected devices:

$ upower -d
Device: /org/freedesktop/UPower/devices/line_power_AC
  native-path:          AC
  power supply:         yes
  updated:              Thursday 21 April 2022 07:42:11 AM (658 seconds ago)
  has history:          no
  has statistics:       no
  line-power
    warning-level:       none
    online:              yes
    icon-name:          'ac-adapter-symbolic'

Device: /org/freedesktop/UPower/devices/battery_BAT0
  native-path:          BAT0
  vendor:               LGC-LGC3.0
  model:                DELL 49VTP27
  serial:               14057
  power supply:         yes
  updated:              Thursday 21 April 2022 07:52:12 AM (57 seconds ago)
  has history:          yes
  has statistics:       yes
  battery
    present:             yes
    rechargeable:        yes
    state:               charging
    warning-level:       none
    energy:              48.507 Wh
    energy-empty:        0 Wh
    energy-full:         57.3981 Wh
    energy-full-design:  48.84 Wh
    energy-rate:         7.1262 W
    voltage:             12.544 V
    time to full:        1.2 hours
    percentage:          93%
    capacity:            100%
    technology:          lithium-ion
    icon-name:          'battery-full-charging-symbolic'
  History (rate):
    1650507732	7.126	charging

....more info

This command is equivalent to running upower -e, followed by upower -i for each device, and thus saves us one step in the process.

3. Using the /sys/class/power_supply Directory

The Linux kernel exposes various information about the system and connected hardware devices in a read-only filesystem known as sysfs. We can access this file system using the /sys directory. We can find the battery device directories under the /sys/class/power_supply directory using the ls command:

$ ls /sys/class/power_supply/
AC  BAT0

BAT0 is the directory we are looking for. It’s usually BAT0 or BAT1, depending on the Linux distribution we’re using. Next, we can get various information about the battery from files inside the directory. We could start with listing files to see what files are present:

ls /sys/class/power_supply/BAT0
alarm           charge_full_design  device        power          subsystem   voltage_min_design
capacity        charge_now          hwmon2        present        technology  voltage_now
capacity_level  current_now         manufacturer  serial_number  type
charge_full     cycle_count         model_name    status         uevent

Now, we can read the contents of the corresponding files to get the required data:

$ cat /sys/class/power_supply/BAT0/capacity
100
$ cat /sys/class/power_supply/BAT0/status
Full

In the above snippet, capacity gives us the percentage of charge in the battery and status tells us whether it is charging or discharging.

4. Conclusion

In this article, we looked at two different methods to get information about battery status using the command line.

Using the upower command, we’re able to print a detailed output about the battery status using one or two commands.

The information can also be accessed using the files in the /sys/class/power_supply/BAT0/ (or BAT1) directory. The information here is very raw and discrete, without any formatting. So, we can directly use the data in bash scripts if we need to.