.bash_profile

PS1="\w \$(~/bin/battery.sh) "

README

Colors:
White = fully charged
Green = 60% charged or better
Yellow = 40% charged or better
Red = less than 40% charged

Symbol:
$ = connected to power
! = not connected

battery.sh

#!/usr/bin/env python
# coding=UTF-8

import math, subprocess

p = subprocess.Popen(["ioreg", "-rc", "AppleSmartBattery"], stdout=subprocess.PIPE)
output = p.communicate()[0]

o_max = [l for l in output.splitlines() if 'MaxCapacity' in l][0]
o_cur = [l for l in output.splitlines() if 'CurrentCapacity' in l][0]
o_crg = [l for l in output.splitlines() if 'ExternalConnected' in l][0]
o_ful = [l for l in output.splitlines() if 'FullyCharged' in l][0]

b_max = float(o_max.rpartition('=')[-1].strip())
b_cur = float(o_cur.rpartition('=')[-1].strip())
b_crg = o_crg.rpartition('=')[-1].strip()
b_ful = o_ful.rpartition('=')[-1].strip()

charge = b_cur / b_max

# Output

import sys

color_green = ''
color_yellow = ''
color_red = ''
color_reset = ''
color_out = (
    "" if b_ful == "Yes"
    else color_green if charge > 0.6
    else color_yellow if charge > 0.4
    else color_red
)

out = color_out

if b_crg == "Yes":
    out += '$'
else:
    out += '!'

out += color_reset

sys.stdout.write(out)