initial commit

sb-cpu.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <unistd.h>
+
+typedef struct {
+  long long idle;
+  long long total;
+} cpu_stats_t;
+
+static int read_cpu_stats(cpu_stats_t *stats) {
+  FILE *fp = fopen("/proc/stat", "r");
+  if (!fp)
+    return 1;
+
+  long long user, nice, system, idle, iowait, irq, softirq;
+  int ret = fscanf(fp, "cpu %lld %lld %lld %lld %lld %lld %lld", &user, &nice,
+                   &system, &idle, &iowait, &irq, &softirq);
+  fclose(fp);
+
+  if (ret != 7)
+    return 1;
+
+  stats->idle = idle + iowait;
+  stats->total = user + nice + system + idle + iowait + irq + softirq;
+  return 0;
+}
+
+static double calculate_usage(cpu_stats_t *prev, cpu_stats_t *curr) {
+  long long diff_total = curr->total - prev->total;
+  long long diff_idle = curr->idle - prev->idle;
+
+  if (diff_total == 0)
+    return 0.0;
+  return 100.0 * (diff_total - diff_idle) / diff_total;
+}
+
+int main() {
+  cpu_stats_t prev, curr;
+
+  if (read_cpu_stats(&prev) < 0) {
+    fprintf(stderr, "Error reading CPU stats\n");
+    return 1;
+  }
+
+  sleep(1);
+
+  if (read_cpu_stats(&curr) < 0) {
+    fprintf(stderr, "Error reading CPU stats\n");
+    return 1;
+  }
+
+  printf("CPU: %.0f%%\n", calculate_usage(&prev, &curr));
+  return 0;
+}