Add an option for only starting a single sensor

fetcher.use

@@ -16,3 +16,6 @@ OPTIONS:
     -p           If this flag is passed, fetcher will print its sensor data to
                  stdout. Enabling this flag will take messages off the output
                  message queue.
+
+    -s           If this flag is passed, fetcher will only open and read 
+                 sensor data from the sensor whose name follows.

src/main.c

@@ -34,9 +34,14 @@
 /** The maximum number of sensors that fetcher can support. */
 #define MAX_SENSORS 8
 
+#define SYSCLOCK_NAME "sysclock"
+
 /** Whether or not to print data to stdout. */
 bool print_output = false;
 
+/** The name of a single sensor to enable, or null if no sensor was selected */
+char *select_sensor = NULL;
+
 /** Stores the thread IDs of all the collector threads. */
 static pthread_t collector_threads[MAX_SENSORS];
 
@@ -112,11 +117,14 @@ int main(int argc, char **argv) {
     opterr = 0;
 
     /* Get command line options. */
-    while ((c = getopt(argc, argv, ":p")) != -1) {
+    while ((c = getopt(argc, argv, ":ps:")) != -1) {
         switch (c) {
         case 'p':
             print_output = true;
             break;
+        case 's':
+            select_sensor = optarg;
+            break;
         case ':':
             fprintf(stderr, "Option -%c requires an argument.\n", optopt);
             exit(EXIT_FAILURE);
@@ -194,8 +202,17 @@ int main(int argc, char **argv) {
         uint8_t naddrs = MAX_ADDR_PER_SENSOR;
         cur = read_sensor_addresses(cur, addresses, &naddrs);
 
+        // Check if the sensor that was requested is this sensor (if none match, will do nothing)
+        if (select_sensor != NULL) {
+            if (strncasecmp(select_sensor, sensor_name, MAX_SENSOR_NAME) != 0) {
+                // Skip this sensor, not the right one
+                fprintf(stderr, "Skipping sensor %s\n", sensor_name);
+                continue;
+            } else {
+                fprintf(stderr, "Found sensor %s, starting\n", select_sensor);
+            }
+        }
         for (uint8_t i = 0; i < naddrs; i++) {
-
             /* Create sensor data collection threads. */
             collector_t collector = collector_search(sensor_name);
             if (collector == NULL) {
@@ -211,10 +228,13 @@ int main(int argc, char **argv) {
             num_sensors++; // Record that a new sensor was created
         }
     }
-
-    /* Add sysclock sensor because it won't be specified in board ID. */
-    collector_t sysclock = collector_search("sysclock");
-    err = pthread_create(&collector_threads[num_sensors], NULL, sysclock, NULL);
+    // Only start the sysclock if we're not debugging a single sensor or if this is the sensor that was selected
+    if (select_sensor == NULL || !strncasecmp(select_sensor, SYSCLOCK_NAME, sizeof(SYSCLOCK_NAME))) {
+        /* Add sysclock sensor because it won't be specified in board ID. */
+        collector_t sysclock = collector_search(SYSCLOCK_NAME);
+        err = pthread_create(&collector_threads[num_sensors], NULL, sysclock, NULL);
+        num_sensors++;
+    }
 
     /* Constantly receive from sensors on message queue and print data. */
     while (print_output) {