inotify battery script

specific.c

#include <stdio.h>
#include <limits.h>
#include <string.h>
#include <fnmatch.h>
#include <sys/inotify.h>

#define BUF_LEN (10 * (sizeof(struct inotify_event) + NAME_MAX + 1))
#define FILE_COUNT 3

void battery_status(char *files[FILE_COUNT]) {
    int i = 0, temp_i;
    double temp_f, capacity;
    FILE *fp;

    capacity = 0.0;

    for (i=0; i < FILE_COUNT; i++) {
        fp = fopen(files[i], "r");

        if (fp != NULL) {
            if (!fnmatch("*BAT*", files[i], FNM_NOESCAPE)) {
                fscanf(fp, "%lf", &temp_f);
                capacity += temp_f;
            } else {
                fscanf(fp, "%d", &temp_i);
            }
        }

        fclose(fp);
    }

    capacity /= 2.0;

    if (temp_i) {
        printf("%.1lf%%+\n", capacity);
    } else {
        printf("%.1lf%%-\n", capacity);
    }
    fflush(stdout);
}

int main() {
    char *read_files[FILE_COUNT] = {
        "/sys/class/power_supply/AC/online",
        "/sys/class/power_supply/BAT0/capacity",
        "/sys/class/power_supply/BAT1/capacity"
    };

    char *watch_files[FILE_COUNT] = {
        "/sys/class/power_supply/AC/uevent",
        "/sys/class/power_supply/BAT0/uevent",
        "/sys/class/power_supply/BAT1/uevent"
    };


    int fd, wd, i;
    char buf[BUF_LEN] __attribute__ ((aligned(8)));
    ssize_t num_read = 1;

    fd = inotify_init();
    if (fd == -1) {
        perror("inotify_init");
    }

    for (i=0; i < FILE_COUNT; i++) {
        wd = inotify_add_watch(fd, watch_files[i], IN_ACCESS);
    }
    if (wd == -1) {
        perror("inotify_add_watch");
    }

    battery_status(read_files);

    while (num_read > 0) {
        num_read = read(fd, buf, BUF_LEN);

        if (num_read == 0 || num_read == -1) {
            perror("read() from inotify fd returned 0");
            break;
        } else {
            battery_status(read_files);
        }
    }

    return 0;
}