read wlan signal with command line tool iwconfig

src/wlanSignal.cpp

@@ -1,12 +1,41 @@
 #include "ros/ros.h"
 #include "wlan_pioneer/WlanSignalMsg.h"
-#include <sstream>
+#include <iostream>
+#include <stdio.h>
+#include <stdlib.h>
 
+using namespace std;
 using namespace ros;
 using namespace wlan_pioneer;
 
+string GetStdoutFromCommand(const string &cmd)
+{
+  string data;
+  FILE *stream;
+  const int max_buffer = 256;
+  char buffer[max_buffer];
+  //cmd.append(" 2>&1");
+
+  stream = popen(cmd.c_str(), "r");
+  if (stream)
+  {
+    while (!feof(stream))
+    {
+      if (fgets(buffer, max_buffer, stream) != NULL)
+      {
+        data.append(buffer);
+      }
+    }
+    pclose(stream);
+  }
+  return data;
+}
+
 int main(int argc, char **argv)
 {
+  // TODO: make interface configurable
+  string singalLevelCmd("iwconfig wlp3s0 | grep Signal | cut -d \"=\" -f3 | cut -d \" \" -f1");
+
   init(argc, argv, "wlanSignal");
   NodeHandle node;
 
@@ -19,7 +48,7 @@ int main(int argc, char **argv)
   {
     WlanSignalMsg msg;
     msg.timestamp = ros::Time::now();
-    msg.level_24G = 0; // TODO: read real WLAN signal strength
+    msg.level_24G = stol(GetStdoutFromCommand(singalLevelCmd));
     msg.level_5G = 0;
 
     ROS_INFO("Signal strength 2.4G: %li      Signal strength 5G: %li", msg.level_24G, msg.level_5G);