add a script to run demo

examples/run_demo.sh

@@ -0,0 +1,74 @@
+#!/bin/bash
+
+
+arg=$1
+gatewayd_path="./target/release/gatewayd"
+cashierd_path="./target/release/cashierd"
+darkfid_path="./target/release/darkfid"
+drk_path="./target/release/drk"
+
+echo Running demo...
+
+if [ "$arg" = "-d" ]; then
+	echo DEBUG MODE	
+	gatewayd_path="./target/debug/gatewayd"
+	cashierd_path="./target/debug/cashierd"
+	darkfid_path="./target/debug/darkfid"
+	drk_path="./target/debug/drk"
+fi
+
+echo Open new tab and run: 
+echo "	$ " $drk_path --help
+
+trap cleanup SIGINT 
+
+function cleanup()
+{
+	screen -X -S "gatewayd" quit
+	screen -X -S "cashierd" quit
+	screen -X -S "darkfid" quit
+	echo Exit demo...
+}
+
+# Start gateway daemon 
+screen -S "gatewayd" -dm "$gatewayd_path" -v 
+status=$?
+if [ $status -ne 0 ]; then
+  echo "Failed to start gateway daemon: $status"
+  exit $status
+fi
+
+# Start cashier daemon 
+screen -S "cashierd" -dm "$cashierd_path" -v
+status=$?
+if [ $status -ne 0 ]; then
+  echo "Failed to start cashier daemon: $status"
+  exit $status
+fi
+
+# Start darkfi daemon 
+screen -S "darkfid" -dm "$darkfid_path" -v
+status=$?
+if [ $status -ne 0 ]; then
+  echo "Failed to start darkfi daemon: $status"
+  exit $status
+fi
+
+# Exit with an error if it detects that either of the processes has exited.
+# Otherwise it loops forever, waking up every 60 seconds 
+while sleep 60; do
+  ps aux |grep "gatewayd" |grep -q -v grep
+  PROCESS_1_STATUS=$?
+  ps aux |grep "cashierd" |grep -q -v grep
+  PROCESS_2_STATUS=$?
+  ps aux |grep "darkfid" |grep -q -v grep
+  PROCESS_3_STATUS=$?
+
+  if [ $PROCESS_1_STATUS -ne 0 -o $PROCESS_2_STATUS -ne 0 -o $PROCESS_3_STATUS -ne 0 ]; then
+    echo "One of the processes has already exited."
+	cleanup
+    exit 1
+  fi
+done
+
+