Correctly test sensor path for Linux 3.13

Previously the fopen write mode caused the call to spuriously report
newer sensors.  Now we check the newer sensors path.  Also plug file
descriptor leak and more carefully check return values.

Author: gaul

README.md

@@ -62,6 +62,7 @@ This section reports those models where mbpfan was tested successfully. It does
 - MacBook Pro 6,2 15"  (Intel i7 - Linux 3.5.0)
 - MacBook Pro 6,2 15"  (Intel i7 - Linux 3.2.0)
 - MacBook Pro 2,2 15"  (Intel Core 2 Duo - Linux 3.4.4)
+- MacBook Air 6,1 13"  (Intel i7 - Linux 3.13)
 - MacBook Air 5,2 13"  (Intel i5 - Linux 3.16)
 - MacBook Air 1,1 13"  (Intel Core Duo - Linux 4.4, Linux 4.8)
 - MacBook Air 7,2 13"  (Intel Core Duo - Linux 4.10)

src/mbpfan.c

@@ -87,43 +87,25 @@ static char *smprintf(const char *fmt, ...)
 
 bool is_legacy_sensors_path()
 {
-    struct utsname kernel;
-    uname(&kernel);
+    const char *path_begin = "/sys/devices/platform/coretemp.0/hwmon/hwmon";
+    int counter;
 
-    char *str_kernel_version;
-    str_kernel_version = strtok(kernel.release, ".");
+    for (counter = 0; counter < 10; counter++) {
+        char hwmon_path[strlen(path_begin)+2];
+        sprintf(hwmon_path, "%s%d", path_begin, counter);
 
-    if (atoi(str_kernel_version) < 3){
-        syslog(LOG_INFO, "mbpfan detected a pre-3.x.x linux kernel. Detected version: %s. Exiting.\n", kernel.release);
-        printf("mbpfan detected a pre-3.x.x linux kernel. Detected version: %s. Exiting.\n", kernel.release);
-        exit(EXIT_FAILURE);
-    }
-
-    
-    // thanks http://stackoverflow.com/questions/18192998/plain-c-opening-a-directory-with-fopen
-    fopen("/sys/devices/platform/coretemp.0/hwmon", "wb");
+        FILE *file = fopen(hwmon_path, "rb");
+        int isdir = file == NULL && errno == EISDIR;
+        if (file != NULL) {
+            fclose(file);
+        }
 
-    if (errno == EISDIR) {
-        return 0;
-    } else {
-        return 1;
+        if (isdir) {
+            return 0;
+        }
     }
 
-    // 
-    // str_kernel_version = strtok(NULL, ".");
-    // int kernel_version = atoi(str_kernel_version);
-
-    // if(verbose) {
-    //     printf("Detected kernel version: %s\n", kernel.release);
-    //     printf("Detected kernel minor revision: %s\n", str_kernel_version);
-
-    //     if(daemonize) {
-    //         syslog(LOG_INFO, "Kernel version: %s", kernel.release);
-    //         syslog(LOG_INFO, "Detected kernel minor revision: %s", str_kernel_version);
-    //     }
-    // }
-
-    // return (atoi(kernel.release) == 3 && kernel_version < 15);
+    return 1;
 }
 
 
@@ -167,9 +149,13 @@ t_sensors *retrieve_sensors()
             sprintf(hwmon_path, "%s%d", path_begin, counter);
 
             // thanks http://stackoverflow.com/questions/18192998/plain-c-opening-a-directory-with-fopen
-            fopen(hwmon_path, "wb");
+            FILE *file = fopen(hwmon_path, "rb");
+            int isdir = file == NULL && errno == EISDIR;
+            if (file != NULL) {
+                fclose(file);
+            }
 
-            if (errno == EISDIR) {
+            if (isdir) {
 
                 path_begin = smprintf("%s/temp", hwmon_path);