dev-cpp-users

[Dev-C++] first time error return on checking file stream validity

[Alan T. <ala...@3n...>]

The code below gives some interesting results.  First return from the
function start_HTML_file is 0 (no error), while the second time it =
returns 1
(could not open file).  What does this mean?
                                                        Thanks, Alan

#include <iostream.h>
#include <stdlib.h>
#include <fstream.h>
#include <string.h>

// define HTML author
const char *Author =3D "Alan Thomas";

//
// function prototype
//
int start_HTML_file (ofstream&output_file, char *keywords =3D NULL,
    char *title =3D NULL);


int main()
{
 ofstream invalid; // used to test for error opening file

  // Test invalid file checking
 cout << "Error return was " << start_HTML_file (invalid, NULL,
                "This is the title") << endl;
 cout << "Error return was " << start_HTML_file (invalid, NULL,
                "This is the title") << endl;

 system("PAUSE");

 return 0;
}

int start_HTML_file (ofstream&output_file, char *keywords =3D NULL, char
*title =3D NULL)
{
 if (!output_file)
    {
     cout << "Error opening file." << endl;
     return 1; // error indication
    }
 // Write header information
 output_file << "<!doctype html public \"-//w3c//dtd html 4.0
transitional//en\">";
 output_file << endl;
 output_file << "<html>" << endl;
 output_file << "<head>" << endl;
 output_file << "<meta http-equiv=3D\"Content-Type\" =
content-\"text/html;
charset=3Diso-8859-1\"";
 output_file << endl;
 output_file << "<meta name=3D\"Author\" content=3D\"" << Author << =
"\">" <<
endl;
 if (keywords !=3D NULL)
    {
     output_file << "<meta name=3D\"KeyWords\" content=3D\"";
     output_file << keywords << ">\"" << endl;
    }
 // Write out title
 if (title !=3D NULL)
    {
     output_file << "<title>";
     output_file << title;
     output_file << "</title>" << endl;
    }
 // End header
 output_file << "</head>" << endl;

 return 0;
}

RE: [Dev-C++] first time error return on checking file stream validity

[Ioannis V. <no...@ya...>]

I have the impression you do not create or open any file, e.g. std::ofstream
invalid("test.txt");

I do not know much about C++ file operations yet but i think this is the
problem.


Ioannis
  -----Original Message-----
  From: dev...@li...
[mailto:dev...@li...]On Behalf Of Alan Thomas
  Sent: Sunday, December 31, 2000 1:19 AM
  To: dev...@li...
  Subject: [Dev-C++] first time error return on checking file stream
validity


  The code below gives some interesting results.  First return from the
  function start_HTML_file is 0 (no error), while the second time it returns
1
  (could not open file).  What does this mean?
                                                          Thanks, Alan

  #include <iostream.h>
  #include <stdlib.h>
  #include <fstream.h>
  #include <string.h>

  // define HTML author
  const char *Author = "Alan Thomas";

  //
  // function prototype
  //
  int start_HTML_file (ofstream&output_file, char *keywords = NULL,
      char *title = NULL);


  int main()
  {
   ofstream invalid; // used to test for error opening file

    // Test invalid file checking
   cout << "Error return was " << start_HTML_file (invalid, NULL,
                  "This is the title") << endl;
   cout << "Error return was " << start_HTML_file (invalid, NULL,
                  "This is the title") << endl;

   system("PAUSE");

   return 0;
  }

  int start_HTML_file (ofstream&output_file, char *keywords = NULL, char
  *title = NULL)
  {
   if (!output_file)
      {
       cout << "Error opening file." << endl;
       return 1; // error indication
      }
   // Write header information
   output_file << "<!doctype html public \"-//w3c//dtd html 4.0
  transitional//en\">";
   output_file << endl;
   output_file << "<html>" << endl;
   output_file << "<head>" << endl;
   output_file << "<meta http-equiv=\"Content-Type\" content-\"text/html;
  charset=iso-8859-1\"";
   output_file << endl;
   output_file << "<meta name=\"Author\" content=\"" << Author << "\">" <<
  endl;
   if (keywords != NULL)
      {
       output_file << "<meta name=\"KeyWords\" content=\"";
       output_file << keywords << ">\"" << endl;
      }
   // Write out title
   if (title != NULL)
      {
       output_file << "<title>";
       output_file << title;
       output_file << "</title>" << endl;
      }
   // End header
   output_file << "</head>" << endl;

   return 0;
  }