Program cannot find an input file if the output file is saved outside of the program's directory


I have a code that takes an input file, does calculations to it and outputs it into an output file. There are 2 input files, one is asked to be provided by the user, the other one is in the ImpFiles folder in the program directory. When i run the code and save the output file in the same forder then it works fine, but when i try to save it on the desktop for example, it gives me my built in error. Heres my code:

void PropertyEstimatesElasticDlg::OnBnClickedOk()
      CString inputFileFourier;
      CString temp;
      CString inputFileMaterial;
      CString outputCalculatedFile;
      GetDlgItemText(IDC_INPUT_FOURIER_ELASTIC, inputFileFourier);
       GetDlgItemText(IDC_INPUT_MATERIAL_ELASTIC, inputFileMaterial);
      GetDlgItemText(IDC_PROPERTY_OUTPUT_ELASTIC, outputCalculatedFile);

      char buffer[256];
      //Open the file where the Fourier coefficients representing the microstrucutre are
      double F[4];
      F[0]=1; //F000 is always egual to 1
      ifstream Fcoefficient (inputFileFourier);
      if (! Fcoefficient.is_open()){
            MessageBox("Error opening file.", "Fourier coefficient file.", MB_OK | MB_ICONEXCLAMATION);
      double coef[24];
      double consC[3], consS[3];
      ifstream elastic (inputFileMaterial);
      while ( elastic.eof() ){

      ifstream coeff ("ImpFiles/coefficients_elastic.txt");
      if ( ! coeff.is_open())
            MessageBox("Error opening file.", "coefficients_elastic file", MB_OK | MB_ICONEXCLAMATION);
      while ( coeff.eof() ){
      for (int i=0; i<24;i++) coeff>>coef[i];

      ofstream outputfile (outputCalculatedFile);
      if (outputfile.is_open()){
//do calculation
            MessageBox("Could not open the output file.", "Error openning file", MB_OK | MB_ICONEXCLAMATION);



The error that I'm getting is the coefficients_elastic.txt could not be opened

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Mad_AngelAuthor Commented:
Maybe instead of doing this: ifstream coeff ("ImpFiles/coefficients_elastic.txt"); there's a way to make it read from ifstream coeff ("%program dir%/ImpFiles/coefficients_elastic.txt");  ?

Jaime OlivaresSoftware ArchitectCommented:
>    ifstream coeff ("ImpFiles/coefficients_elastic.txt");
You must use fully qualified path names. Something like:


To achieve this, first save application folder name in a variable, and add before your filename. To obtain exe's folder use WINAPI's GetModuleFileName()
>>You must use fully qualified path names

That's not true. Relative paths will work also.

Where exactly does the program reside and where exactly is the input file stored. BTW, what about using

bool GetInputFileName      (      string& strName) {

      BYTE                  Filter      [ 100] = "Text (*.txt)\0*.txt\0\0";    
      char                  acBuf      [ MAX_PATH];
      OPENFILENAME      ofName;

      ZeroMemory      (      &ofName,      sizeof( OPENFILENAME));
      ZeroMemory      (      acBuf,      MAX_PATH);
      ofName.hwndOwner            =      NULL;
      ofName.lStructSize      =      sizeof( OPENFILENAME);
      ofName.lpstrFile        =      acBuf;
      ofName.nMaxFile         =      MAX_PATH;
      ofName.lpstrInitialDir  =      NULL;
      ofName.lpstrDefExt      =      "txt";
      ofName.lpstrFilter      =      ( char *) Filter;
      ofName.nFilterIndex            =      1;
      ofName.lpstrTitle            =      "Choose InputFile";

      if      ( !GetOpenFileName ( &ofName))
            return ( false);

      strName = acBuf

      return ( true);


     string strName;
     ifstream Fcoefficient (strName.c_str());
     if (! Fcoefficient.is_open()){
         MessageBox("Error opening file.", "Fourier coefficient file.", MB_OK | MB_ICONEXCLAMATION);
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Jaime OlivaresSoftware ArchitectCommented:
Try to run you program from explorer and from inside your compiler IDE, your "current directory" won't be the same. So, if you have an "aplication directory" at the same root as your .exe file, I recommend you again to use GetModuleFileName to avoid any confussion when trying to access that folder.
That allows you to change to any user directory without lossing the "path" to your own directory.
Mad_AngelAuthor Commented:
I can't get the GetModuleFileName() to work, i tried using CString but it doesnt allow me, can you post an example please?

PS jkr, I don't want the user to provide me with coefficients_elastic.txt, i want the program to know that it's in the folder ImpFiles which is inside of the program directory.

>>i want the program to know that it's in the folder ImpFiles which is inside of the program directory.

Are you executing the application from VisualStudio? If so, try

ifstream coeff ("../ImpFiles/coefficients_elastic.txt");

since jaime_olivares is right about the IDE issue.
Jaime OlivaresSoftware ArchitectCommented:
Here is (tested):

      CString appDir;
      ::GetModuleFileName(NULL, appDir.GetBuffer(MAX_PATH), MAX_PATH);
      appDir = appDir.Left(appDir.ReverseFind('\\')+1);

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Jaime OlivaresSoftware ArchitectCommented:
You can use so:

ifstream coeff (appDir+"ImpFiles/coefficients_elastic.txt");
Mad_AngelAuthor Commented:
I'm executing the program from both VisualStudio and the built file.

With ifstream coeff ("../ImpFiles/coefficients_elastic.txt"); it doesn't find the file even when i save the outpul file in the program directory where it was run from.

your paths are


Mad_AngelAuthor Commented:
I got it, jaime-olivares' tested code worked for me.

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