Show the current capacity of all managed batteries in Linux

battery.sh

#!/usr/bin/env bash
# Show the current capacity of all managed batteries
# script by github.com/hhromic

POWER_SUPPLY_DIR=/sys/class/power_supply
mapfile -t CAPACITIES < <(compgen -G "$POWER_SUPPLY_DIR"/'*'/capacity)

for capacity in "${CAPACITIES[@]}"; do
  battery="${capacity%/*}"
  battery="${battery##*/}"
  printf "%s=%s"$'\n' "$battery" "$(cat "$capacity")"
done