I/O: Improve messaging when user doesn't have permissions to write to LEDs

gohai · gohai · commit a0d5cd715861 · 2015-10-12T00:06:39.000+02:00
This is e.g. the case with the newly released Raspbian 2015-09-24.
diff --git a/java/libraries/io/src/processing/io/LED.java b/java/libraries/io/src/processing/io/LED.java
@@ -87,7 +87,10 @@ public LED(String dev) {
     String fn = "/sys/class/leds/" + dev + "/trigger";
     int ret = NativeInterface.writeFile(fn, "none");
     if (ret < 0) {
-      throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));
+      if (ret == -13) {     // EACCES
+        System.err.println("You might need to install a custom udev rule to allow regular users to modify /sys/class/leds/*.");
+      }
+      throw new RuntimeException(NativeInterface.getError(ret));
     }
   }
 

Original file line number	Diff line number	Diff line change
`@@ -87,7 +87,10 @@ public LED(String dev) {`
`87`	`87`	`String fn = "/sys/class/leds/" + dev + "/trigger";`
`88`	`88`	`int ret = NativeInterface.writeFile(fn, "none");`
`89`	`89`	`if (ret < 0) {`
`90`		`- throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));`
	`90`	`+ if (ret == -13) { // EACCES`
	`91`	`+ System.err.println("You might need to install a custom udev rule to allow regular users to modify /sys/class/leds/*.");`
	`92`	`+ }`
	`93`	`+ throw new RuntimeException(NativeInterface.getError(ret));`
`91`	`94`	`}`
`92`	`95`	`}`
`93`	`96`