Rewrite reading core mhz files

src/cpu.cpp

@@ -223,12 +223,16 @@ bool CPUStats::UpdateCPUData()
 
 bool CPUStats::UpdateCoreMhz() {
     m_coreMhz.clear();
+    FILE *fp;
+    char str[10];
     for (size_t i = 0; i < m_cpuData.size(); i++)
     {
-        std::string val;
-        std::ifstream file("/sys/devices/system/cpu/cpu" + std::to_string(i) + "/cpufreq/scaling_cur_freq");
-        std::getline(file, val);
-        m_cpuData[i].mhz = std::stoi(val) / 1000;
+        std::string path = "/sys/devices/system/cpu/cpu" + std::to_string(i) + "/cpufreq/scaling_cur_freq";
+        if (fp = fopen(path.c_str(), "r")){
+            fscanf(fp, "%s", str);
+            m_cpuData[i].mhz = atoi(str) / 1000;
+            fclose(fp);
+        }
     }
     
     m_cpuDataTotal.cpu_mhz = 0;