Writing to a single file from two files.

Jake hollcroft (14)
I created a simple program that writes some text to two different text files. Could someone show me how to create a program that would retrieve the information from those two files, and put them in a single file, first the content of input1 and then the content of input2. I am really needing help learning how to do this.
Here is the program that I created that creates the two files.

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#include <iostream>
#include <fstream>
#include <string>

int main()
{
	using namespace std;
	string input1;
	
	ofstream fout("input1.txt");
	fout<<"This is the first line in input1.txt.\n";
	cout<<"The first line was added to input1"<<endl;
	fout<<"This is the second line in input1.txt.\n";
	cout<<"The second line was added to input1"<<endl;
	fout<<"This is the third line in input1.txt.\n";
	cout<<"The third line was added to input1"<<endl;
	fout<<"This is the fourth line in input1.txt.\n";
	cout<<"The fourth line was added to input1"<<endl;
fout.close();

fout.open("input2.txt");
fout<<"This is the first line in input2.txt.\n";
cout<<"The first line was added to input2"<<endl;
fout<<"This is the second line in input2.txt."<<endl;
cout<<"The second line was added to input2"<<endl;
fout<<"This is the third line in input2.txt."<<endl;
cout<<"The third line was added to input2"<<endl;
fout.close();	

cin.get();
cin.get();
	return 0;
}
snowright (48)
Could you consider reading http://www.cplusplus.com/doc/tutorial/files/ ?
Last edited on
Jake hollcroft (14)
I read it, but I don't understand it. I am needing a program that can open or read the content of input1 and create a single file, and then to do the same with input2, but have them both going to the same single file, instead of two different files.
snowright (48)
If you did not understand a lot from the tutorial I am not quite sure you are going to understand this when I write it either. Let us try it for now though. I wrote a more general case, this will make you able to read contents of N files and add them to a single file in order. Suppose you have some preliminaries:
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static const int FILES = 3;

static const char * fileName[ FILES ] = 
{
	"file1",
	"file2",
	"file3"
};

static const char * fileNameOut = "file4";


Reading the files could be something similar to following.
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ifstream is[ FILES ];
int length[ FILES ];
for( int f = 0; f < FILES; f++ )
{
	is[ f ].open( fileName[ f ], ios::binary );
	if( is[ f ].is_open( ) )
	{
		is[ f ].seekg( 0, ios::end );
		length[ f ] = is[ f ].tellg( );
		is[ f ].seekg( 0, ios::beg );
	}
	else
	{
		cout << "Unable to open file " << fileName[ f ] << ".\n";
		//Handle error
	}
}

int addedLength[ FILES ];
addedLength[ 0 ] = 0;
for( int f = 1; f < FILES; f++ )
	addedLength[ f ] = addedLength[ f - 1 ] + length[ f - 1 ];

char * b = new char[ addedLength[ FILES - 1 ] + length[ FILES - 1 ] ];

for( int f = 0; f < FILES; f++ )
{
	is[ f ].read( ( b + addedLength[ f ] ), length[ f ] );
	is[ f ].close( );
}


Continuing with same writing could be done as follows.
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ofstream os( fileNameOut, ios::binary );
if( os.is_open( ) )
{
	os.write( b, addedLength[ FILES - 1 ] + length[ FILES - 1 ] );
	os.close( );
}
else
	cout << "Unable to open file " << fileNameOut << ".\n";


Notice I am using the std namespace.
Had you any questions, needed explanation or assist in understanding the code, feel free to ask.
Last edited on
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