====== tmux Battery Meter ======

I spend most of my time working from a terminal within a tmux session. When on my laptop it's nice to have instant visual access to my battery charge and if I'm on AC or not. 

I wrote a little program that provides the battery's percent charge and shows a + if on AC and a - if running off the battery.

Amazingly enough, this is called tmux_bat_meter.


===== Building =====

This thing is pretty damn simple. To build it:

<code>
  gcc tmux_bat_meter.c -o tmux_bat_meter
</code>

===== Using =====

To use this in tmux, plunk the compiled binary in your path add this to your tmux.conf:

<code>
  set -g status-right '#(tmux_bat_meter) #[fg=blue]%H:%M#[default]'
</code>

This puts tmux_bat_meter in the right hand part of the status bar. See below for a screenshot.

===== Screenshot =====

{{:tmux_bat_meter.png?direct&600|}}

===== Source =====

<file c tmux_bat_meter.c>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define AC_PATH		"/sys/class/power_supply/AC/online"
#define BAT_FULL	"/sys/class/power_supply/BAT0/energy_full"
#define BAT_NOW		"/sys/class/power_supply/BAT0/energy_now"
#define BAT_FULL2	"/sys/class/power_supply/BAT0/charge_full"
#define BAT_NOW2		"/sys/class/power_supply/BAT0/charge_now"

int main(void)
{
	unsigned int ac;
	float bat_full, bat_now;
	
	FILE *fp;
	
	/* are we on AC? */
	fp = fopen(AC_PATH, "r");
	fscanf(fp, "%d", &ac);
	fclose(fp);

	/* get current charge and max charge */
	if ( (! (fp = fopen( BAT_FULL, "r"))) &&
		(! (fp = fopen(BAT_FULL2, "r"))) )
	{
		fprintf(stderr, "Could not open BAT_FULL/2\n");
		return(1);
	}

	fscanf(fp, "%f", &bat_full);
	fclose(fp);
	
	if ( (! (fp = fopen( BAT_NOW, "r"))) &&
		(! (fp = fopen(BAT_NOW2, "r"))) )
	{
		fprintf(stderr, "Could not open BAT_NOW/2\n");
		return(2);
	}
	
	fscanf(fp, "%f", &bat_now);
	fclose(fp);

	printf("%c%2.0f%%", ac ? '+' : '-', (bat_now * 100) / bat_full);

	return(0);
}
</file>