JSBSim.cpp

Go to the documentation of this file.

/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 Module:       JSBSim.cpp
 Author:       Jon S. Berndt
 Date started: 08/17/99
 Purpose:      Standalone version of JSBSim.
 Called by:    The USER.
 
 ------------- Copyright (C) 1999  Jon S. Berndt (jon@jsbsim.org) -------------
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU Lesser General Public License as published by the Free Software
 Foundation; either version 2 of the License, or (at your option) any later
 version.
 
 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
 details.
 
 You should have received a copy of the GNU Lesser General Public License along with
 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 Place - Suite 330, Boston, MA  02111-1307, USA.
 
 Further information about the GNU Lesser General Public License can also be found on
 the world wide web at http://www.gnu.org.
 
FUNCTIONAL DESCRIPTION
--------------------------------------------------------------------------------
 
This class implements the JSBSim standalone application. It is set up for compilation
under gnu C++, MSVC++, or other compiler.
 
HISTORY
--------------------------------------------------------------------------------
08/17/99   JSB   Created
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
#include "initialization/FGTrim.h"
#include "FGFDMExec.h"
#include "input_output/FGXMLFileRead.h"
 
#if !defined(__GNUC__) && !defined(sgi) && !defined(_MSC_VER)
#  include <time>
#else
#  include <time.h>
#endif
 
#if defined(_MSC_VER)
#  include <float.h>
#elif defined(__GNUC__) && !defined(sgi)
#  include <fenv.h>
#endif
 
#if defined(__BORLANDC__) || defined(_MSC_VER) || defined(__MINGW32__)
#  define WIN32_LEAN_AND_MEAN
#  include <windows.h>
#  include <mmsystem.h>
#  include <regstr.h>
#  include <sys/types.h>
#  include <sys/timeb.h>
#else
#  include <sys/time.h>
#endif
 
#include <iostream>
#include <cstdlib>
 
using namespace std;
using JSBSim::FGXMLFileRead;
using JSBSim::Element;
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GLOBAL DATA
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
SGPath RootDir;
SGPath ScriptName;
string AircraftName;
SGPath ResetName;
vector <string> LogOutputName;
vector <SGPath> LogDirectiveName;
vector <string> CommandLineProperties;
vector <double> CommandLinePropertyValues;
JSBSim::FGFDMExec* FDMExec;
JSBSim::FGTrim* trimmer;
 
bool realtime;
bool play_nice;
bool suspend;
bool catalog;
bool nohighlight;
 
double end_time = 1e99;
double simulation_rate = 1./120.;
bool override_sim_rate = false;
double sleep_period=0.01;
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FORWARD DECLARATIONS
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
bool options(int, char**);
int real_main(int argc, char* argv[]);
void PrintHelp(void);
 
#if defined(__BORLANDC__) || defined(_MSC_VER) || defined(__MINGW32__)
  double getcurrentseconds(void)
  {
    struct timeb tm_ptr;
    ftime(&tm_ptr);
    return tm_ptr.time + tm_ptr.millitm*0.001;
  }
#else
  double getcurrentseconds(void)
  {
    struct timeval tval;
    struct timezone tz;
 
    gettimeofday(&tval, &tz);
    return (tval.tv_sec + tval.tv_usec*1e-6);
  }
#endif
 
#if defined(__BORLANDC__) || defined(_MSC_VER) || defined(__MINGW32__)
  void sim_nsleep(long nanosec)
  {
    Sleep((DWORD)(nanosec*1e-6)); // convert nanoseconds (passed in) to milliseconds for Win32.
  }
#else
  void sim_nsleep(long nanosec)
  {
    struct timespec ts, ts1;
 
    ts.tv_sec = 0;
    ts.tv_nsec = nanosec;
    nanosleep(&ts, &ts1);
  }
#endif

class XMLFile : public FGXMLFileRead {
public:
  bool IsScriptFile(const SGPath& filename) {
    bool result=false;
    Element *document = LoadXMLDocument(filename, false);
    if (document && document->GetName() == "runscript") result = true;
    ResetParser();
    return result;
  }
  bool IsLogDirectiveFile(const SGPath& filename) {
    bool result=false;
    Element *document = LoadXMLDocument(filename, false);
    if (document && document->GetName() == "output") result = true;
    ResetParser();
    return result;
  }
  bool IsAircraftFile(const SGPath& filename) {
    bool result=false;
    Element* document = LoadXMLDocument(filename, false);
    if (document && document->GetName() == "fdm_config") result = true;
    ResetParser();
    return result;
  }
  bool IsInitFile(const SGPath& filename) {
    bool result=false;
    Element *document = LoadXMLDocument(filename, false);
    if (document && document->GetName() == "initialize") result = true;
    ResetParser();
    return result;
  }
};
 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS DOCUMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/

 
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
int main(int argc, char* argv[])
{
#if defined(_MSC_VER)
  _clearfp();
  _controlfp(_controlfp(0, 0) & ~(_EM_INVALID | _EM_ZERODIVIDE | _EM_OVERFLOW),
           _MCW_EM);
#elif defined(__GNUC__) && !defined(sgi) && !defined(__APPLE__)
  feenableexcept(FE_DIVBYZERO | FE_INVALID);
#endif
 
  try {
    real_main(argc, argv);
  } catch (string& msg) {
    std::cerr << "FATAL ERROR: JSBSim terminated with an exception."
              << std::endl << "The message was: " << msg << std::endl;
    return 1;
  } catch (...) {
    std::cerr << "FATAL ERROR: JSBSim terminated with an unknown exception."
              << std::endl;
    return 1;
  }
  return 0;
}
 
int real_main(int argc, char* argv[])
{
  // *** INITIALIZATIONS *** //
 
  ScriptName = "";
  AircraftName = "";
  ResetName = "";
  LogOutputName.clear();
  LogDirectiveName.clear();
  bool result = false, success;
  bool was_paused = false;
  
  double frame_duration;
 
  double new_five_second_value = 0.0;
  double actual_elapsed_time = 0;
  double initial_seconds = 0;
  double current_seconds = 0.0;
  double paused_seconds = 0.0;
  double sim_lag_time = 0;
  double cycle_duration = 0.0;
  double override_sim_rate_value = 0.0;
  long sleep_nseconds = 0;
 
  realtime = false;
  play_nice = false;
  suspend = false;
  catalog = false;
  nohighlight = false;
 
  // *** PARSE OPTIONS PASSED INTO THIS SPECIFIC APPLICATION: JSBSim *** //
  success = options(argc, argv);
  if (!success) {
    PrintHelp();
    exit(-1);
  }
 
  // *** SET UP JSBSIM *** //
  FDMExec = new JSBSim::FGFDMExec();
  FDMExec->SetRootDir(RootDir);
  FDMExec->SetAircraftPath(SGPath("aircraft"));
  FDMExec->SetEnginePath(SGPath("engine"));
  FDMExec->SetSystemsPath(SGPath("systems"));
  FDMExec->GetPropertyManager()->Tie("simulation/frame_start_time", &actual_elapsed_time);
  FDMExec->GetPropertyManager()->Tie("simulation/cycle_duration", &cycle_duration);
 
  if (nohighlight) FDMExec->disableHighLighting();
 
  if (simulation_rate < 1.0 )
    FDMExec->Setdt(simulation_rate);
  else
    FDMExec->Setdt(1.0/simulation_rate);
 
  if (override_sim_rate) override_sim_rate_value = FDMExec->GetDeltaT();
 
  // SET PROPERTY VALUES THAT ARE GIVEN ON THE COMMAND LINE and which are for the simulation only.
 
  for (unsigned int i=0; i<CommandLineProperties.size(); i++) {
 
    if (CommandLineProperties[i].find("simulation") != std::string::npos) {
      if (FDMExec->GetPropertyManager()->GetNode(CommandLineProperties[i])) {
        FDMExec->SetPropertyValue(CommandLineProperties[i], CommandLinePropertyValues[i]);
      }
    }
  }
 
  // *** OPTION A: LOAD A SCRIPT, WHICH LOADS EVERYTHING ELSE *** //
  if (!ScriptName.isNull()) {
 
    result = FDMExec->LoadScript(ScriptName, override_sim_rate_value, ResetName);
 
    if (!result) {
      cerr << "Script file " << ScriptName << " was not successfully loaded" << endl;
      delete FDMExec;
      exit(-1);
    }
 
  // *** OPTION B: LOAD AN AIRCRAFT AND A SET OF INITIAL CONDITIONS *** //
  } else if (!AircraftName.empty() || !ResetName.isNull()) {
 
    if (catalog) FDMExec->SetDebugLevel(0);
 
    if ( ! FDMExec->LoadModel(SGPath("aircraft"),
                              SGPath("engine"),
                              SGPath("systems"),
                              AircraftName)) {
      cerr << "  JSBSim could not be started" << endl << endl;
      delete FDMExec;
      exit(-1);
    }
 
    if (catalog) {
      FDMExec->PrintPropertyCatalog();
      delete FDMExec;
      return 0;
    }
 
    JSBSim::FGInitialCondition *IC = FDMExec->GetIC();
    if ( ! IC->Load(ResetName)) {
      delete FDMExec;
      cerr << "Initialization unsuccessful" << endl;
      exit(-1);
    }
 
  } else {
    cout << "  No Aircraft, Script, or Reset information given" << endl << endl;
    delete FDMExec;
    exit(-1);
  }
 
  // Load output directives file[s], if given
  for (unsigned int i=0; i<LogDirectiveName.size(); i++) {
    if (!LogDirectiveName[i].isNull()) {
      if (!FDMExec->SetOutputDirectives(LogDirectiveName[i])) {
        cout << "Output directives not properly set in file " << LogDirectiveName[i] << endl;
        delete FDMExec;
        exit(-1);
      }
    }
  }
 
  // OVERRIDE OUTPUT FILE NAME. THIS IS USEFUL FOR CASES WHERE MULTIPLE
  // RUNS ARE BEING MADE (SUCH AS IN A MONTE CARLO STUDY) AND THE OUTPUT FILE
  // NAME MUST BE SET EACH TIME TO AVOID THE PREVIOUS RUN DATA FROM BEING OVER-
  // WRITTEN.
  for (unsigned int i=0; i<LogOutputName.size(); i++) {
    string old_filename = FDMExec->GetOutputFileName(i);
    if (!FDMExec->SetOutputFileName(i, LogOutputName[i])) {
      cout << "Output filename could not be set" << endl;
    } else {
      cout << "Output filename change from " << old_filename << " from aircraft"
              " configuration file to " << LogOutputName[i] << " specified on"
              " command line" << endl;
    }
  }
 
  // SET PROPERTY VALUES THAT ARE GIVEN ON THE COMMAND LINE
 
  for (unsigned int i=0; i<CommandLineProperties.size(); i++) {
 
    if (!FDMExec->GetPropertyManager()->GetNode(CommandLineProperties[i])) {
      cerr << endl << "  No property by the name " << CommandLineProperties[i] << endl;
      delete FDMExec;
      exit(-1);
    } else {
      FDMExec->SetPropertyValue(CommandLineProperties[i], CommandLinePropertyValues[i]);
    }
  }
 
  FDMExec->RunIC();
 
  // PRINT SIMULATION CONFIGURATION
  FDMExec->PrintSimulationConfiguration();
 
  // Dump the simulation state (position, orientation, etc.)
  FDMExec->GetPropagate()->DumpState();
  
  // Perform trim if requested via the initialization file
  JSBSim::TrimMode icTrimRequested = (JSBSim::TrimMode)FDMExec->GetIC()->TrimRequested();
  if (icTrimRequested != JSBSim::TrimMode::tNone) {
    trimmer = new JSBSim::FGTrim( FDMExec, icTrimRequested );
    try {
      trimmer->DoTrim();
 
      if (FDMExec->GetDebugLevel() > 0)
        trimmer->Report();
 
      delete trimmer;
    } catch (string& msg) {
      cerr << endl << msg << endl << endl;
      exit(1);
    }
  }
  
  cout << endl << JSBSim::FGFDMExec::fggreen << JSBSim::FGFDMExec::highint
       << "---- JSBSim Execution beginning ... --------------------------------------------"
       << JSBSim::FGFDMExec::reset << endl << endl;
 
  result = FDMExec->Run();  // MAKE AN INITIAL RUN
 
  if (suspend) FDMExec->Hold();
 
  // Print actual time at start
  char s[100];
  time_t tod;
  time(&tod);
  strftime(s, 99, "%A %B %d %Y %X", localtime(&tod));
  cout << "Start: " << s << " (HH:MM:SS)" << endl;
 
  frame_duration = FDMExec->GetDeltaT();
  if (realtime) sleep_nseconds = (long)(frame_duration*1e9);
  else          sleep_nseconds = (sleep_period )*1e9;           // 0.01 seconds
 
  tzset(); 
  current_seconds = initial_seconds = getcurrentseconds();
 
  // *** CYCLIC EXECUTION LOOP, AND MESSAGE READING *** //
  while (result && FDMExec->GetSimTime() <= end_time) {
 
    FDMExec->ProcessMessage(); // Process messages, if any.
    
    // Check if increment then hold is on and take appropriate actions if it is
    // Iterate is not supported in realtime - only in batch and playnice modes
    FDMExec->CheckIncrementalHold();
    
    // if running realtime, throttle the execution, else just run flat-out fast
    // unless "playing nice", in which case sleep for a while (0.01 seconds) each frame.
    // If suspended, then don't increment cumulative realtime "stopwatch".
 
    if ( ! FDMExec->Holding()) {
      if ( ! realtime ) {         // ------------ RUNNING IN BATCH MODE
 
        result = FDMExec->Run();
 
        if (play_nice) sim_nsleep(sleep_nseconds);
 
      } else {                    // ------------ RUNNING IN REALTIME MODE
 
        // "was_paused" will be true if entering this "run" loop from a paused state.
        if (was_paused) {
          initial_seconds += paused_seconds;
          was_paused = false;
        }
        current_seconds = getcurrentseconds();                      // Seconds since 1 Jan 1970
        actual_elapsed_time = current_seconds - initial_seconds;    // Real world elapsed seconds since start
        sim_lag_time = actual_elapsed_time - FDMExec->GetSimTime(); // How far behind sim-time is from actual
                                                                    // elapsed time.
        for (int i=0; i<(int)(sim_lag_time/frame_duration); i++) {  // catch up sim time to actual elapsed time.
          result = FDMExec->Run();
          cycle_duration = getcurrentseconds() - current_seconds;   // Calculate cycle duration
          current_seconds = getcurrentseconds();                    // Get new current_seconds
          if (FDMExec->Holding()) break;
        }
 
        if (play_nice) sim_nsleep(sleep_nseconds);
 
        if (FDMExec->GetSimTime() >= new_five_second_value) { // Print out elapsed time every five seconds.
          cout << "Simulation elapsed time: " << FDMExec->GetSimTime() << endl;
          new_five_second_value += 5.0;
        }
      }
    } else { // Suspended
      was_paused = true;
      paused_seconds = getcurrentseconds() - current_seconds;
      sim_nsleep(sleep_nseconds);
      result = FDMExec->Run();
    }
 
  }
 
  // PRINT ENDING CLOCK TIME
  time(&tod);
  strftime(s, 99, "%A %B %d %Y %X", localtime(&tod));
  cout << "End: " << s << " (HH:MM:SS)" << endl;
 
  // CLEAN UP
  delete FDMExec;
 
  return 0;
}
 
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
#define gripe cerr << "Option '" << keyword     \
    << "' requires a value, as in '"    \
    << keyword << "=something'" << endl << endl;/**/
 
bool options(int count, char **arg)
{
  int i;
  bool result = true;
 
  if (count == 1) {
    PrintHelp();
    exit(0);
  }
 
  cout.setf(ios_base::fixed);
 
  for (i=1; i<count; i++) {
    string argument = string(arg[i]);
    string keyword(argument);
    string value("");
    string::size_type n=argument.find("=");
 
    if (n != string::npos && n > 0) {
      keyword = argument.substr(0, n);
      value = argument.substr(n+1);
    }
 
    if (keyword == "--help") {
      PrintHelp();
      exit(0);
    } else if (keyword == "--version") {
      cout << endl << "  JSBSim Version: " << FDMExec->GetVersion() << endl << endl;
      exit (0);
    } else if (keyword == "--realtime") {
      realtime = true;
    } else if (keyword == "--nice") {
      play_nice = true;
      if (n != string::npos) {
        try {
          sleep_period = atof( value.c_str() );
        } catch (...) {
          cerr << endl << "  Invalid sleep period given!" << endl << endl;
          result = false;
        }
      } else {
        sleep_period = 0.01;
      }
    } else if (keyword == "--suspend") {
      suspend = true;
    } else if (keyword == "--nohighlight") {
        nohighlight = true;
    } else if (keyword == "--outputlogfile") {
      if (n != string::npos) {
        LogOutputName.push_back(value);
      }
    } else if (keyword == "--logdirectivefile") {
      if (n != string::npos) {
        LogDirectiveName.push_back(SGPath::fromLocal8Bit(value.c_str()));
      } else {
        gripe;
        exit(1);
      }
    } else if (keyword == "--root") {
      if (n != string::npos) {
        RootDir = SGPath::fromLocal8Bit(value.c_str());
      } else {
        gripe;
        exit(1);
      }
    } else if (keyword == "--aircraft") {
      if (n != string::npos) {
        AircraftName = value;
      } else {
        gripe;
        exit(1);
      }
    } else if (keyword == "--script") {
      if (n != string::npos) {
        ScriptName = SGPath::fromLocal8Bit(value.c_str());
      } else {
        gripe;
        exit(1);
      }
    } else if (keyword == "--initfile") {
      if (n != string::npos) {
        ResetName = SGPath::fromLocal8Bit(value.c_str());
      } else {
        gripe;
        exit(1);
      }
 
    } else if (keyword == "--property") {
      if (n != string::npos) {
         string propName = value.substr(0,value.find("="));
         string propValueString = value.substr(value.find("=")+1);
         double propValue = atof(propValueString.c_str());
         CommandLineProperties.push_back(propName);
         CommandLinePropertyValues.push_back(propValue);
      } else {
        gripe;
        exit(1);
      }
 
    } else if (keyword.substr(0,5) == "--end") {
      if (n != string::npos) {
        try {
        end_time = atof( value.c_str() );
        } catch (...) {
          cerr << endl << "  Invalid end time given!" << endl << endl;
          result = false;
        }
      } else {
        gripe;
        exit(1);
      }
 
    } else if (keyword == "--simulation-rate") {
      if (n != string::npos) {
        try {
          simulation_rate = atof( value.c_str() );
          override_sim_rate = true;
        } catch (...) {
          cerr << endl << "  Invalid simulation rate given!" << endl << endl;
          result = false;
        }
      } else {
        gripe;
        exit(1);
      }
 
    } else if (keyword == "--catalog") {
        catalog = true;
        if (value.size() > 0) AircraftName=value;
    } else if (keyword.substr(0,2) != "--" && value.empty() ) {
      // See what kind of files we are specifying on the command line
 
      XMLFile xmlFile;
      SGPath path = SGPath::fromLocal8Bit(keyword.c_str());
      
      if (xmlFile.IsScriptFile(path)) ScriptName = path;
      else if (xmlFile.IsLogDirectiveFile(path))  LogDirectiveName.push_back(path);
      else if (xmlFile.IsAircraftFile(SGPath("aircraft")/keyword/keyword)) AircraftName = keyword;
      else if (xmlFile.IsInitFile(path)) ResetName = path;
      else if (xmlFile.IsInitFile(SGPath("aircraft")/AircraftName/keyword)) ResetName = SGPath("aircraft")/AircraftName/keyword;
      else {
        cerr << "The argument \"" << keyword << "\" cannot be interpreted as a file name or option." << endl;
        exit(1);
      }
 
    }
    else //Unknown keyword so print the help file, the bad keyword and abort
    {
          PrintHelp();
          cerr << "The argument \"" << keyword << "\" cannot be interpreted as a file name or option." << endl;
          exit(1);
    }
 
  }
 
  // Post-processing for script options. check for incompatible options.
 
  if (catalog && !ScriptName.isNull()) {
    cerr << "Cannot specify catalog with script option" << endl << endl;
    result = false;
  }
  if (!AircraftName.empty() && ResetName.isNull() && !catalog) {
    cerr << "You must specify an initialization file with the aircraft name." << endl << endl;
    result = false;
  }
  if (!ScriptName.isNull() && !AircraftName.empty()) {
    cerr << "You cannot specify an aircraft file with a script." << endl;
    result = false;
  }
 
  return result;
 
}
 
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
void PrintHelp(void)
{
  cout << endl << "  JSBSim version " << FDMExec->GetVersion() << endl << endl;
  cout << "  Usage: jsbsim [script file name] [output file names] <options>" << endl << endl;
  cout << "  options:" << endl;
    cout << "    --help  returns this message" << endl;
    cout << "    --version  returns the version number" << endl;
    cout << "    --outputlogfile=<filename>  sets (overrides) the name of a data output file" << endl;
    cout << "    --logdirectivefile=<filename>  specifies the name of a data logging directives file" << endl;
    cout << "                                   (can appear multiple times)" << endl;
    cout << "    --root=<path>  specifies the JSBSim root directory (where aircraft/, engine/, etc. reside)" << endl;
    cout << "    --aircraft=<filename>  specifies the name of the aircraft to be modeled" << endl;
    cout << "    --script=<filename>  specifies a script to run" << endl;
    cout << "    --realtime  specifies to run in actual real world time" << endl;
    cout << "    --nice  specifies to run at lower CPU usage" << endl;
    cout << "    --nohighlight  specifies that console output should be pure text only (no color)" << endl;
    cout << "    --suspend  specifies to suspend the simulation after initialization" << endl;
    cout << "    --initfile=<filename>  specifies an initilization file" << endl;
    cout << "    --catalog specifies that all properties for this aircraft model should be printed" << endl;
    cout << "              (catalog=aircraftname is an optional format)" << endl;
    cout << "    --property=<name=value> e.g. --property=simulation/integrator/rate/rotational=1" << endl;
    cout << "    --simulation-rate=<rate (double)> specifies the sim dT time or frequency" << endl;
    cout << "                      If rate specified is less than 1, it is interpreted as" << endl;
    cout << "                      a time step size, otherwise it is assumed to be a rate in Hertz." << endl;
    cout << "    --end=<time (double)> specifies the sim end time" << endl << endl;
 
    cout << "  NOTE: There can be no spaces around the = sign when" << endl;
    cout << "        an option is followed by a filename" << endl << endl;
}