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/* LINUX DOCS: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-power
* (C) 2024 Tim Keller <tjk@tjkeller.xyz>
* MIT License
*/
#include <libnotify/notify.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#define PSUPATH "/sys/class/power_supply"
#define PERIOD 3 // number of seconds before each check
#define MAX_BATTERIES 8
#define MAX_PSU_NAME_LEN 8
#define MAX_MSG_LEN 32
#define MAX_PROP_PATH_LEN 64
// variables
static char batteries[MAX_BATTERIES][MAX_PSU_NAME_LEN];
static unsigned int num_batteries;
static FILE *fp;
static char prop_path[MAX_PROP_PATH_LEN];
// functions
void load_installed_batteries() {
// search through "power supplies" for "status" property (only available on batteries)
DIR *dir, *subdir;
struct dirent *entry, *subentry;
if ((dir = opendir(PSUPATH)) == NULL) {
fprintf(stderr, "failed to open power supplies filesystem: %s\n", PSUPATH);
exit(EXIT_FAILURE);
}
// power supplies TODO warn user if max batteries exceeded
num_batteries = 0;
while ((entry = readdir(dir)) != NULL) {
if (entry->d_name[0] == '.')
continue; // skip . and ..
if (strlen(entry->d_name) > MAX_PSU_NAME_LEN) {
fprintf(stderr, "the power supply's name was too long: %s\n", entry->d_name);
exit(EXIT_FAILURE);
}
// power supplies will always be a directory, no need to check beforehand :)
snprintf(prop_path, MAX_PROP_PATH_LEN, PSUPATH "/%.8s", entry->d_name); // 8 is equal to MAX_PSU_NAME_LEN, prevent compiler warning
if ((subdir = opendir(prop_path)) == NULL) {
fprintf(stderr, "failed to open power supply: %s\n", prop_path);
exit(EXIT_FAILURE);
}
// power supply properties
while ((subentry = readdir(subdir)) != NULL) {
// add to list of batteries if it has the status property
if (strcmp(subentry->d_name, "status") == 0) {
if(num_batteries >= MAX_BATTERIES) {
fprintf(stderr, "maximum number of batteries (8) exceeded\n");
exit(EXIT_FAILURE);
}
strncpy(batteries[num_batteries], entry->d_name, MAX_PSU_NAME_LEN);
num_batteries++;
break;
}
}
closedir(subdir);
}
closedir(dir);
}
void notifysend(char *title, char *content, NotifyUrgency urgency) {
NotifyNotification *notif;
notify_init("lowbat");
notif = notify_notification_new(title, content, NULL);
notify_notification_set_timeout(notif, NOTIFY_EXPIRES_NEVER);
notify_notification_set_urgency(notif, urgency);
notify_notification_show(notif, NULL);
}
void read_prop(char *psu, char *prop, char *fmt, void *out) {
/* this function is only designed to read one var at a time because all bat
* properties will only be one var */
snprintf(prop_path, MAX_PROP_PATH_LEN, PSUPATH "/%s/%s", psu, prop);
if ((fp = fopen(prop_path, "r")) != NULL) {
fscanf(fp, fmt, out);
fclose(fp);
}
else {
fprintf(stderr, "failed to read fmt '%s' from property %s\n", fmt, prop_path);
exit(EXIT_FAILURE);
}
}
int get_total_capacity() {
unsigned long int energy_full = 0, energy_now = 0, x;
int i;
if (!num_batteries)
return 0;
for (i = 0; i < num_batteries; i++) {
read_prop(batteries[i], "energy_full", "%ld", &x);
energy_full += x;
read_prop(batteries[i], "energy_now", "%ld", &x);
energy_now += x;
}
return energy_now * 100 / energy_full;
}
int is_discharging() {
char status[12]; // valid values: "Unknown", "Charging", "Discharging", "Not charging", "Full"
int i;
if (!num_batteries)
return 0;
for (i = 0; i < num_batteries; i++) {
read_prop(batteries[i], "status", "%s", &status);
if (strcmp(status, "Discharging") != 0)
return 0;
}
return 1;
}
int main() {
int discharging, capacity, old_discharging = -1, old_capacity = -1;
int warning_level = 0; // 1 if warned already, 2 if warned with critical warning
char msg[MAX_MSG_LEN];
while (1) {
load_installed_batteries();
discharging = is_discharging();
capacity = get_total_capacity();
if (discharging) {
if (capacity <= 5 && warning_level < 2) {
snprintf(msg, MAX_MSG_LEN, "%d%% remains", capacity);
notifysend("Critical Low Battery Warning", msg, NOTIFY_URGENCY_CRITICAL);
warning_level = 2;
} else if (capacity <= 20 && warning_level < 1) {
snprintf(msg, MAX_MSG_LEN, "%d%% remains", capacity);
notifysend("Low Battery Warning", msg, NOTIFY_URGENCY_NORMAL);
warning_level = 1;
}
} else {
warning_level = 0; // clear conditions
}
if (discharging != old_discharging || capacity != old_capacity) {
printf("%s%d%%\n", discharging ? "-" : "+", capacity);
fflush(stdout);
}
old_discharging = discharging;
old_capacity = capacity;
sleep(PERIOD);
}
return 0;
}
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