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  #1  
Old 22-May-2006, 11:32
jdbrine jdbrine is offline
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File Output - Using Variable for FileName

Hi,

Can someone give me an idea how I would go about using a variable in my program to determine what a name of a file should be when output is written?

My code is below:

CPP / C++ / C Code:
	ofstream output;
	
	#define FILE_OUT "Env.txt"

	output.open(FILE_OUT, ios::out);

	output<<env.sender.FName<<" "<<env.sender.LName<<endl;
	output<<env.sender.Street<<endl;
	output<<env.sender.City<<", "<<env.sender.State<<" "<<env.sender.Zip<<endl<<endl<<endl;
	output<<'\t'<<'\t'<<'\t'<<'\t'<<env.receiver.FName<<" "<<env.receiver.LName<<endl;
	output<<'\t'<<'\t'<<'\t'<<'\t'<<env.receiver.Street<<endl;
	output<<'\t'<<'\t'<<'\t'<<'\t'<<env.receiver.City<<", "<<env.receiver.State<<" "<<env.receiver.Zip<<endl;

	output.close();

I am unsure how to change the format in my #define statement to accept a variable name instead of hardcoding the name.

Any suggestions are appreciated. Thanks!
  #2  
Old 22-May-2006, 13:28
davis
 
Posts: n/a

Re: File Output - Using Variable for FileName

Quote:
Originally Posted by jdbrine
I am unsure how to change the format in my #define statement to accept a variable name instead of hardcoding the name.

There is no way to convert a macro argument into a character constant.

Just use a program variable.

CPP / C++ / C Code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
    cout << "Enter a filename: ";
    std::string strFilename;
    cin >> strFilename;
    fstream outfile( strFilename.c_str(), ios_base::out );
    if( outfile.is_open() )
    {
        cout << "Successfully created file: " << strFilename << endl;
        outfile.close();
    }
    else
    {
        cout << "Creating file named: " << strFilename << " failed!" << endl;
    }
    return 0;
}

Output:
Code:
Enter a filename: bogus
Successfully created file: bogus

...and please consider using more whitespace in your code!


:davis:
  #3  
Old 22-May-2006, 14:17
jdbrine jdbrine is offline
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Re: File Output - Using Variable for FileName

So, if I wanted to make the filename be an element of my structure, I would do something like:

CPP / C++ / C Code:
void WriteEnvelope(Envelope env)
{

	ofstream output;
	
	//#define FILE_OUT "Env.txt"

	std::string strFilename;
	
	strFilename=env.receiver.LName;

	
	fstream outfile( strFilename.c_str(), ios_base::out );
	
	//output.open(FILE_OUT, ios::out);

	output<<env.sender.FName<<" "<<env.sender.LName<<endl;

	output<<env.sender.Street<<endl;

	output<<env.sender.City<<", "<<env.sender.State<<" "<<env.sender.Zip<<endl<<endl<<endl;

	output<<'\t'<<'\t'<<'\t'<<'\t'<<env.receiver.FName<<" "<<env.receiver.LName<<endl;

	output<<'\t'<<'\t'<<'\t'<<'\t'<<env.receiver.Street<<endl;

	output<<'\t'<<'\t'<<'\t'<<'\t'<<env.receiver.City<<", "<<env.receiver.State<<" "<<env.receiver.Zip<<endl;

	output.close();


}

It created the file, but didn't dump any of the data.
  #4  
Old 22-May-2006, 14:40
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WaltP WaltP is offline
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Re: File Output - Using Variable for FileName

Wrong whitespace. He meant horizontal (between operators and such), not vertical:
CPP / C++ / C Code:
output<<env.sender.City<<", "<<env.sender.State<<" "<<env.sender.Zip<<endl<<endl<<endl;
to
CPP / C++ / C Code:
output << env.sender.City << ", " << env.sender.State << " " 
       << env.sender.Zip << endl << endl << endl;
shortening lines also so they aren't over 80-100 characters per line.

Whatyouhaveisakintothistext.Veryhardtoread.
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  #5  
Old 22-May-2006, 14:56
jdbrine jdbrine is offline
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Re: File Output - Using Variable for FileName

Okay thanks. So, if I wanted to make the filename be an element of my structure, I would do something like:


CPP / C++ / C Code:
void WriteEnvelope(Envelope env)
{

	ofstream output;
	
	//#define FILE_OUT "Env.txt"

	std::string strFilename;
	
	strFilename=env.receiver.LName;

	
	fstream outfile( strFilename.c_str(), ios_base::out );
	
	//output.open(FILE_OUT, ios::out);

	output<<  env.sender.FName  <<  " " <<  env.sender.LName <<  ndl;
	output <<  env.sender.Street  <<  endl;
	output <<  env.sender.City << ", " <<  env.sender.State  <<  " "
                       <<  env.sender.Zip  << endl  <<  endl  <<  endl;
	output <<  '\t' << '\t' << '\t' << '\t' <<  env.receiver.FName  << " "
                       <<  env.receiver.LName  <<  endl;
	output <<  '\t' << '\t' << '\t' << '\t' <<  env.receiver.Street << endl;
	output <<  '\t' << '\t' << '\t' << '\t' <<  env.receiver.City  << ", "
                      <<  env.receiver.State  << " "<<  env.receiver.Zip<<endl;

	output.close();


}

It created the file, but didn't dump any of the data.
  #6  
Old 22-May-2006, 15:05
jdbrine jdbrine is offline
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Re: File Output - Using Variable for FileName

Thanks, I figured out my problem. I appreciate your help!
  #7  
Old 22-May-2006, 15:19
jdbrine jdbrine is offline
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Re: File Output - Using Variable for FileName

If I wanted to append a filetype, .txt, would I be able to using this same example?

CPP / C++ / C Code:
void WriteEnvelope(Envelope env)
{

	ofstream output;
	
	//#define FILE_OUT "Env.txt"

	std::string strFilename;
	
	strFilename=env.receiver.LName;

	
	output.open( strFilename.c_str(), ios_base::out );
	
	//output.open(FILE_OUT, ios::out);

	output << env.sender.FName << " " << env.sender.LName << endl;
	output << env.sender.Street << endl;
	output << env.sender.City << ", " <<env.sender.State << " " 
		   <<env.sender.Zip << endl << endl << endl;
	output << '\t' << '\t' << '\t' << '\t' << env.receiver.FName << " "
		   <<env.receiver.LName << endl;
	output << '\t' << '\t' << '\t' << '\t' << env.receiver.Street << endl;
	output << '\t' << '\t' << '\t' << '\t' << env.receiver.City << ", "
		   << env.receiver.State << " " <<env.receiver.Zip << endl;

	output.close();


}
  #8  
Old 22-May-2006, 15:32
davis
 
Posts: n/a

Re: File Output - Using Variable for FileName

Quote:
Originally Posted by jdbrine
If I wanted to append a filetype, .txt, would I be able to using this same example?

The user can just enter filename.txt or you can simply append a desired file extension to the string.

CPP / C++ / C Code:
std::string strFilename;
strFilename += ".txt";
strFilename=env.receiver.LName;


:davis:
 
 
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