battery_log/sources/main/battery.c

#include <stdio.h>
#include <errno.h>
#include <unistd.h>

#define CHARGE_NOW_PATH "/sys/class/power_supply/BAT0/charge_now"
#define CHARGE_FULL_PATH "/sys/class/power_supply/BAT0/charge_full"
#define VERSION "v0.0"
#define TITLE "Battery Percentage, by Catluck Kettlemerry"
#define PROGNAME "battery_percentage"
#define USAGE0 "Usage: "
#define USAGE1 "[option]"
#define OPTIONS0 "Options:"
#define OPTIONS1 "\t-v run verbosely"
#define OPTIONS2 "\t-h show help and exit"
#define OPTIONS3 "\t-t provide terse output"

int run_verbose = 0;
int run_terse = 0;

void print_help(void){
	printf("%s %s\n", TITLE, VERSION);
	printf("%s %s %s\n", USAGE0, PROGNAME, USAGE1);
	printf("%s\n%s\n%s\n%s\n", OPTIONS0, OPTIONS1, OPTIONS2, OPTIONS3);
}

int main(int argc, char *const argv[]){

	int opt;
	while((opt = getopt(argc, argv, "vht")) != -1) {
		switch(opt){
		case 'v':
			run_verbose = 1;
			break;
		case 'h':
			print_help();
			return 0;
		case 't':
			run_terse = 1;
			break;
		default:
			printf("Literally how could you pass an unspecified argument to this program");
		}
	}

	FILE * fd_now = fopen(CHARGE_NOW_PATH, "r");
	FILE * fd_full = fopen(CHARGE_FULL_PATH, "r");

	int c_now;
	int c_full;

	int vals_read = fscanf(fd_now, "%d", &c_now);
	if(vals_read != 1){
		if(errno != 0){
			perror("Error reading full battery charge: ");
		} else if(vals_read == EOF){
			printf("End-of-file reached while reading current battery charge(?)");
		} else {
			printf("Invalid number of arguments (%d) returned while reading full battery charge", vals_read);
		}
		return 1;
	}
	vals_read = fscanf(fd_full, "%d", &c_full);
	if(vals_read != 1){
		if(errno != 0){
			perror("Error reading full battery charge: ");
		} else if(vals_read == EOF){
			printf("End-of-file reached while reading full battery charge(?)");
		} else {
			printf("Invalid number of arguments (%d) returned while reading full battery charge", vals_read);
		}
		return 1;
	}

	if(run_verbose){
		printf("Current charge: %d\n microampere-hours", c_now);
		printf("Full charge: %d\n microampere-hours", c_full);
	}

	if(!run_terse) {
		printf("Battery percentage: ");
	}
	float frac = ((float)c_now) / ((float)c_full);
	int pct = (int)(frac * 100);
	printf("%d\n", pct);
	return 0;
}