uptime: Use clock_gettime instead of reading from /dev/uptime

apps/src/uptime.c

@@ -1,27 +1,10 @@
 #include <stdio.h>
-#include <stdlib.h>
+#include <time.h>
 
 int main()
 {
-    FILE* fp = fopen("/dev/uptime", "r");
-    if (!fp)
-    {
-        perror("fopen");
-        return 1;
-    }
+    struct timespec tp;
+    clock_gettime(CLOCK_MONOTONIC, &tp); // On Luna, CLOCK_MONOTONIC starts at boot.
 
-    char buf[BUFSIZ];
-    fgets(buf, sizeof(buf), fp);
-
-    if (ferror(fp))
-    {
-        perror("fgets");
-        return 1;
-    }
-
-    long ms_uptime = atol(buf);
-
-    printf("up for %ld seconds\n", ms_uptime / 1000);
-
-    fclose(fp);
+    printf("up for %ld seconds\n", tp.tv_sec);
 }