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

[James G. <Jam...@Cl...>]

1st. You should only define your defaults in the declaration of the
function, and not redefine them in the definition of the function.
 
The reason you are not getting an error the first time you access invalid is
because when it is created the state bits are set to 'good'. After you have
tried to write out the state is not 'bad'. If you were to test and return if
the stream isn't open (is_open() returns true if the file pointer is not a
null pointer).
 
Possibly change this:
 
 if (!output_file)
    {
     cout << "Error opening file." << endl;
     return 1; // error indication
    }

to this
 
 if (!output_file.is_open())
    {
     cout << "Error opening file." << endl;
     return 1; // error indication
    }

Regards, 

James. 

-----Original Message-----
From: Alan Thomas [mailto:ala...@3n...]
Sent: Saturday, December 30, 2000 11:19 PM
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;
}








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