From e7e4ade4ca53bd806dd539c297bc82ec0d24a10a Mon Sep 17 00:00:00 2001
From: Florian Kromer <thinwybk@mailbox.org>
Date: Sun, 6 Aug 2017 13:35:48 +0200
Subject: [PATCH] add D script to control a led

easiest is to install the compiler (here: gdc) on the target which runs Ubuntu with `sudo apt-get install gdc`

use `./build` to build the executable script

invoke the script with:

- `./led --command=on`
- `./led --command=flash`
- `./led --command=off`
---
 chp05/dLED/build  |  3 +++
 chp05/dLED/dLED.d | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100755 chp05/dLED/build
 create mode 100644 chp05/dLED/dLED.d

diff --git a/chp05/dLED/build b/chp05/dLED/build
new file mode 100755
index 0000000..cdea085
--- /dev/null
+++ b/chp05/dLED/build
@@ -0,0 +1,3 @@
+#!/bin/bash
+echo "Building the D led example script led"
+gdc dLED.d -o led
diff --git a/chp05/dLED/dLED.d b/chp05/dLED/dLED.d
new file mode 100644
index 0000000..71989f1
--- /dev/null
+++ b/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;
+}