Merge pull request #11 from fkromer/d-led

add D script to control a led

chp05/dLED/build

@@ -0,0 +1,3 @@
+#!/bin/bash
+echo "Building the D led example script led"
+gdc dLED.d -o led

chp05/dLED/dLED.d

@@ -0,0 +1,44 @@
+import std.file;
+import std.getopt;
+import std.stdio;
+
+int main (string[] args) {
+   int ARGUMENT_COUNT = 2;
+   string LED3_PATH = "/sys/class/leds/beaglebone:green:usr3";
+
+   enum Command : string
+   {
+      on = "on",
+      off = "off",
+      flash = "flash"
+   }
+
+   enum ReturnCode : int
+   {
+      pass = 0,
+      fail = 1
+   }
+
+   if (args.length != ARGUMENT_COUNT) {
+      writeln("too many or too little arguments");
+      return ReturnCode.fail;
+   }
+
+   string cmd = "invalid"; // no default, value force validation below to fail
+   getopt(args, "command", &cmd);
+
+   chdir(LED3_PATH);
+
+   if (cmd == Command.on) {
+      std.file.write("brightness", "1");
+   } else if (cmd == Command.off) {
+      std.file.write("brightness", "0");
+   } else if (cmd == Command.flash) {
+      std.file.write("trigger", "timer");
+   } else {
+      writeln("command not supported");
+      return ReturnCode.fail;
+   }
+
+   return ReturnCode.pass;
+}