add getROSArg function to ros init

clients/roscpp/include/ros/init.h

@@ -195,6 +195,16 @@ ROSCPP_DECL bool isStarted();
  */
 ROSCPP_DECL CallbackQueue* getGlobalCallbackQueue();
 
+/**
+ * \brief searches the command line arguments for the given arg parameter. In case this argument is not found
+ * an empty string is returned.
+ *
+ * \param argc the number of command-line arguments
+ * \param argv the command-line arguments
+ * \param arg argument to search for
+ */
+ROSCPP_DECL std::string getROSArg(int argc, const char* const* argv, const std::string& arg);
+
 /**
  * \brief returns a vector of program arguments that do not include any ROS remapping arguments.  Useful if you need
  * to parse your arguments to determine your node name

clients/roscpp/src/libros/init.cpp

@@ -509,6 +509,20 @@ void init(const VP_string& remappings, const std::string& name, uint32_t options
   init(remappings_map, name, options);
 }
 
+std::string getROSArg(int argc, const char* const* argv, const std::string& arg)
+{
+  for (int i = 0; i < argc; ++i)
+  {
+    std::string str_arg = argv[i];
+    size_t pos = str_arg.find(":=");
+    if (str_arg.substr(0,pos) == arg)
+    {
+      return str_arg.substr(pos+2);
+    }
+  }
+  return "";
+}
+
 void removeROSArgs(int argc, const char* const* argv, V_string& args_out)
 {
   for (int i = 0; i < argc; ++i)