Warning: to download this program, you'll want to save the Source listing, and edit out the HTML. This is due to an incompatibility between HTML and Perl. I've made a note of where this is important. There is no HTML code inside the --- cut here --- marks.

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#!/usr/bin/perl

# Simple Battery Monitor by Ian Johnston
#-----------------------------------------
# this program was designed and coded in about an hour, as a way to have
# a reasonable display of current battery status.  it's not very slick
# or even a great program, but it works, and it's very simple.  it is
# designed solely with Linux in mind, and your kernel must have the APM
# patches installed for it to work.  if your computer doesn't have an APM
# BIOS, this program won't help you at all.
#
# the display shows three pieces of information: whether the battery is
# charging or not, whether the AC line is connected, and the approximate
# charge in the battery.  as of this writing, the screen looked like
# this:
#
#	 ----------------------
#	 |Battery Status  * AC|
#	 |###########---------|
#	 |0        5        10|
#	 ----------------------
#
# the information displayed is: * = charging (becomes a '-' when the
# battery isn't charging), AC = power line connected (once again, 
# becomes '--' when disconnected).  the power bar should be fairly
# obvious, but it indicates percentage of battery charge, in 5% chunks.
#
# there are some variables below which are designed to be modified to 
# suit individual tastes.  at the moment, they are refresh delay and
# bar-character.  refresh delay is the number of seconds between when
# the program updates the information.  i have this sent to 10 at the
# moment, since that seems like a reasonable amount of time, given the
# circumstances.  the bar-character variable is just in case you don't
# like the "#" character, and want to use, say "*" instead.  it's a 
# matter of taste.
#
# i run this program as a window, using the following command:
# 
# rxvt -geometry 20x3+582+0 -T battery -n battery -e /home/reaper/bin/battery &
#
# obviously, you should replace the executable path (after the -e) with
# the path to wherever you stick the program.  the geometry should be 
# customized to suit your particular needs as well.  (20x3 is the right
# size for the window, though.)
#
# this is hardly the prettiest possible implementation, but it is a quick,
# simple hack, and it works for my needs.
#
# this software is copyright (c) 1996 Ian Johnston.  it is freely
# distributable in any form, and may be modified without any prior
# permission.  if you include a substantial portion of this code in a
# program you write, please mention my name as a contributing author.
# i leave it up to you to determine what substantial means.  this program
# is not warranted in any way to perform any particular function, and 
# suitability to a given task is neither expressed nor implied.  use
# at your own risk.
#
# please mail me with any bugs or comments: reaper@muppetlabs.com or
# reaper@gahd.mallard.rain.com
#
# i don't plan on maintaining this software in any way, but if i make
# changes for the better, i'll post them to my web site:
# http://www.muppetlabs.com/~reaper/
# like i said above, i will be glad to fix bugs if you find them.

#-------------------------------------------------------------------
# user-definable variables:

$refresh_delay = 10; # number of seconds between refreshes - I use 10
$bar_character = "#"; # the character which makes up the power bar

#-------------------------------------------------------------------

$| = 1;
$CLS = "\014";

if (-x "/usr/bin/tput") {             # SysV-like systems.
        $CLS = `/usr/bin/tput clear`;
} elsif (-x "/usr/ucb/clear") {       # Deathstarish-challenged boxen.
	$CLS = `/usr/ucb/clear`;
}


while (1)
{
	open (APM, "/proc/apm");
	@apm = ; # this line doesn't work with HTML
			# it should read: @apm = <APM>;
			# View Source to make sure you get the
			# correct line.
	close APM;
	
	$ac = (split(' ', $apm[3]))[1]; # on or off
	$status = (split(' ', $apm[4]))[2]; # 'charging' or 'charged'
	$power = (split(' ', $apm[5]))[2]; # a percentage
	$power =~ s/(\d+)%/$1/;

	if ($status =~ 'charging') {$charging = '*';} else {$charging = "-";}
	if ($ac =~ 'on') {$line_power = 'AC';} else {$line_power = '--';}
	$bar_mult = int($power / 5);

	$charge = "";

	for ($x=0; $x<$bar_mult; $x++)
	{
		$charge .= $bar_character;
	}
	for ($x=0; $x<(20-$bar_mult); $x++)
	{
		$charge .= "-";
	}

	print $CLS;
	print "Battery Status  $charging $line_power\n";
	print "$charge\n";
	print "0        5        10";
	
	sleep $refresh_delay;
}
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