The attached script requires "make menuconfig" to have
Power management and ACPI options --->
[*] ACPI (Advanced Configuration and Power Interface) Support --->
<*> Battery
or CONFIG_ACPI_BATTERY enabled if you do .config manually.
The script reads /sys/class/power_supply/BAT1/uevent on a laptop and
calculates the percentage of battery charge. Because it only reads from
/sys, and does not write, it can be run by a regular user. The script
is primitive, and has to be stopped with {CTRL}{C}.
The script runs in text mode, and can run in xterm or even a pure text
console. I've removed the #!/bin/bash at the top of the attached file
and chmod'ed it non-executable. The mailing list software seems to
reject any such attachments. You can source the file as is, or chmod it
executable, and insert #!/bin/bash at the top. Note that there is an
ANSI escape sequence in the script, to keep the output in one location.
Regular cut-and-paste can fail if you try to copy from the screen.
--
Walter Dnes <[email protected]>
I don't run "desktop environments"; I run useful applications
#
# If no battery found, bail out
if [ ! -d /sys/class/power_supply/BAT1 ]; then
echo "***ERROR***; Battery not detected"
exit
fi
#
# Get line containing full design charge value
full=`grep POWER_SUPPLY_CHARGE_FULL_DESIGN /sys/class/power_supply/BAT1/uevent`
#
# Strip out everything except the actual number itself
full1="${full#POWER*=}"
#
# Get half of the full value, for use in emulating "round offs" in integer
# arithmetic.
half=$(( ${full} / 2 ))
while true
do
#
# Get line containing current charge value and strip out everything
# except the actual number itself
now=`grep POWER_SUPPLY_CHARGE_NOW /sys/class/power_supply/BAT1/uevent`
now1="${now#POWER*=}"
#
# Multiply by 1000, so that the following division is actually 10 times
# the percentage.
now2=$(( ${now1} * 1000 ))
percent=$(( ${now2} / ${full1} ))
#
# Get the remainder of the division. If it's greater than or equal to
# half the divisor (as determined above) add 1 to the percent x 10 value.
remainder=$(( ${now2} % ${full1} ))
if [ ${remainder} -ge ${half} ]; then
percent=$(( ${percent} + 1 ))
fi
#
# Treating ${percent} as a string, figure out where to place a decimal
# point to fake 10ths of a percent.
pointer=$(( ${#percent} - 1 ))
percent1="${percent:0:${pointer}}.${percent:${pointer}}"
#
# Backtrack the cursor up to 7 columns, and display the new value
echo -n "[7D${percent1} %"
#
# Wait 5 seconds and update again. This is an infinite loop.
sleep 5
done
