This is some quick code I threw together this evening to measure battery level, remaining battery life in hh:mm, and current battery state (charging, charged, discharging). It has been tested under Ubuntu 9.04 Netbook Remix and seems fine; let me know if you try it. It uses a super-simple state machine to iterate around /proc/acpi/battery/BAT0/ looking for the info it needs.
Code:
Code:
///////////////////////////////////////////////////////////////////////
// Christopher Mitchell
// Linux Battery Level Checker
// May 13th, 2009
// http://www.cemetech.net
//
// This code isn't terribly groundbreaking, but please be respectful as
// far as reuse and modifications; credit me, or at least drop me an
// email to let me know you found my code helpful
///////////////////////////////////////////////////////////////////////
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <math.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define PATH_BATT_STATE "/proc/acpi/battery/BAT0/state"
#define PATH_BATT_INFO "/proc/acpi/battery/BAT0/info"
#define BATT_READ_BUFLEN 256
struct battstate {
short unsigned int powerstate, time_hour, time_min;
float chargelevel;
};
enum powerstates { //indicate charging or discharging
POWER_CHARGING,
POWER_CHARGED,
POWER_DISCHARGING
};
int main(int argc, char* argv[]);
struct battstate* getBattState(void);
int main(int argc, char* argv[]) {
struct battstate* thisstate;
thisstate = getBattState();
switch(thisstate->powerstate) {
case POWER_CHARGING:
printf("Battery is currently charging.\n");
break;
case POWER_CHARGED:
printf("Battery is charged.\n");
break;
case POWER_DISCHARGING:
printf("Battery is currently discharging.\n");
break;
default:
printf("!!BUG!! Unrecognized power state returned.\n");
exit(-1);
break;
}
printf("Battery charge level is %f%%.\n",thisstate->chargelevel);
if (thisstate->powerstate != POWER_CHARGED) {
printf("Remainging %d:%d\n",thisstate->time_hour,thisstate->time_min);
}
return 0;
}
struct battstate *getBattState(void) {
static struct battstate mybattstate;
int battStateHandle;
long int battRate_mA=0;
long int battMax_mAh=0;
long int battRemain_mAh=0;
char buffer[BATT_READ_BUFLEN];
char tok_unit[8];
int readoffset;
short int readstate=0,readlen=0; //0=reading,1=eol,2=eof
if (-1 == (battStateHandle = open(PATH_BATT_INFO,O_RDONLY))) {
perror("Could not open battery info for reading");
exit(-1);
}
while (readstate < 2) {
readoffset = 0;
readstate = 0;
while (!readstate) {
if (0 > (readlen = read(battStateHandle,buffer+readoffset,1))) {
perror("Failed to read battery state");
exit(-1);
}
if (!readlen) {
readstate=2;
break;
}
if ('\n' == *(buffer+readoffset)) {
readstate++;
*(buffer+readoffset+1) = '\0';
}
readoffset++;
}
if (readstate == 2) break;
if (NULL != strstr(buffer,"last full capacity")) {
if (0 >= sscanf(buffer+25,"%ld %s",&battMax_mAh,tok_unit)) {
perror("sscanf for battery capacity");
exit(-1);
}
break;
}
}
close(battStateHandle);
if (-1 == (battStateHandle = open(PATH_BATT_STATE,O_RDONLY))) {
perror("Could not open battery state for reading");
exit(-1);
}
readstate = 0;
while (readstate < 2) {
readoffset = 0;
readstate = 0;
while (!readstate) {
if (0 > (readlen = read(battStateHandle,buffer+readoffset,1))) {
perror("Failed to read battery state");
exit(-1);
}
if (0 == readlen) {
readstate=2;
break;
}
if ('\n' == *(buffer+readoffset)) {
readstate++;
*(buffer+readoffset+1) = '\0';
}
readoffset++;
}
if (readstate == 2) break;
if (NULL != strstr(buffer,"charging state")) {
if (NULL != strstr(buffer,"discharging")) mybattstate.powerstate = POWER_DISCHARGING;
else if (NULL != strstr(buffer,"charged")) mybattstate.powerstate = POWER_CHARGED;
else mybattstate.powerstate = POWER_CHARGING;
} else if (NULL != strstr(buffer,"present rate")) {
if (0 >= sscanf(buffer+25,"%ld %s",&battRate_mA,tok_unit)) {
perror("sscanf for battery rate failed");
exit(-1);
}
} else if (NULL != strstr(buffer,"remaining capacity")) {
if (0 >= sscanf(buffer+25,"%ld %s",&battRemain_mAh,tok_unit)) {
perror("sscanf for battery capacity");
exit(-1);
}
}
}
close(battStateHandle);
//printf("%ld, %ld, %ld\n",battRemain_mAh,battMax_mAh,battRate_mA);
mybattstate.chargelevel = 100.00*((float)battRemain_mAh/(float)battMax_mAh);
if (battRate_mA) {
mybattstate.time_hour = floor(battRemain_mAh/battRate_mA);
mybattstate.time_min = floor(60*(((float)battRemain_mAh/(float)battRate_mA)-mybattstate.time_hour));
}
return &mybattstate;
}
BTW, twitter fails 
I'm looking forward to exploring it more. 
