batcolor.c

//purpleposeidon@gmail.com
//Mar 15 2011

//Checks the battery level every so often, and writes a color code escape sequence to ~/.battery_color
//compile this program, have it run at startup:
//  crontab -e
//    @reboot              /home/USER/bin/batcolor
//Or something
//Change PS1 to cat ~/.battery_color in .bashrc
//Here's mine:
//  PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u$(cat ~/.battery_color)@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\n\$ '

//TODO: It'd be nice to have it only update when charge_now is changed
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/stat.h>
#include <errno.h>
#include <wordexp.h>


const int sleep_time = 45; /* how often to check, in seconds */
const char out_file[] = "~/.battery_color"; /* color escape code written here */
const char cn_file[] = "/sys/class/power_supply/BAT0/charge_now";
const char cf_file[] = "/sys/class/power_supply/BAT0/charge_full";



const char color_not_running[] = "\033[0m\033[33m"; /* brown */
const char color_battery_gone[] = "\033[30m\033[1m"; /* dark gray */
const char *colors[] = {
  "\033[0m\033[31m", /* red */
  "\033[31m\033[1m",  /* orange */
  "\033[33m\033[1m", /* yellow */
  "\033[0m\033[32m", /* green */
  "\033[32m\033[1m", /* bright green */
};
const int col_count = 5;


int colorize(const char *s) {
  /* Write string to file */
  FILE *out;
  wordexp_t p;
  if (wordexp(out_file, &p, WRDE_SHOWERR)) {
    return -1;
  }
  out = fopen(p.we_wordv[0], "w");
  fputs(s, out);
  fclose(out);
  wordfree(&p);
  return 0;
}

void not_running() {
  colorize(color_not_running);
}

void battery_gone() {
  colorize(color_battery_gone);
}

int update_color() {
  /* Get charge, pick appropriate color */
  int charge_now, charge_full, charge_index;
  float perc;
  FILE *fd;
  fd = fopen(cf_file, "r");
  if (!fd) return -1; /* battery probably removed */
  fscanf(fd, "%i", &charge_full);
  fclose(fd);

  fd = fopen(cn_file, "r");
  if (!fd) return -1;
  fscanf(fd, "%i", &charge_now);
  fclose(fd);

  perc = ((float)charge_now)/charge_full;
  charge_index = perc*(col_count+1);
  if (colorize(colors[charge_index])) {
    exit(EXIT_FAILURE);
  }
 return 0;
}

void handle_sig(int signum) {
  /* call atexits */
  exit(EXIT_SUCCESS);
}

int main() {
  /* Have the color set appropriately when program gets killed */
  atexit(not_running);
  signal(SIGINT, handle_sig);
  signal(SIGHUP, handle_sig);

  /* Check that there is a battery file */
  struct stat result;
  errno = 0;
  if (stat(cn_file, &result) || errno) {
    perror("Unable to access battery information");
    return EXIT_FAILURE;
  }

  /* Wait quietly in the darkness */
  for (;;) {
    if (update_color()) {
      battery_gone();
    }
    sleep(sleep_time);
  }
  return 0;
}