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File manipulation

pmah (6)
Hello, I am a newbie in c++. I have done file copy program which copies two file and makes new file to write. But this has limitations, it doesn't consider whitespace while writing. I want to modify it so that input is read as vector, and it is written as vector for output as well. Here is my program. 

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int main()
{
	ifstream ifile1, ifile2;
	ofstream ofile;
	char ch;
	string fname1, fname2, fname3;

	cout<<"\n\n Merge two files and write it in a new file :\n";
	cout<<"-------------------------------------------------\n";

	cout<<" Input the 1st file name : ";
	
	cin>>fname1;
	cout<<" Input the 2nd file name : ";
	
	cin>>fname2;
	cout<<" Input the new file name where to merge the above two files : ";
	cin>> fname3;
	ifile1.open(fname1);
	ifile2.open(fname2);
	if (!ifile1  || !ifile2 )
	{
		perror("fopen()");
		cout<<" File does not exist or error in opening...!!\n";
		exit(EXIT_FAILURE);
	}
	ofile.open(fname3);
	if (!ofile)
	{
		cout<<" File does not exist or error in opening...!!\n";
		exit(EXIT_FAILURE);
	}
	while (ifile1.eof()==0)
	{
		ifile1>>ch;
		ofile << ch;
	}
	while (ifile2.eof()==0)
	{
		ifile2 >> ch;
		ofile << ch;
	}
	cout<<" The two files merged into %s file successfully..!!\n\n"<<fname3;
	ifile1.close();
	ifile2.close();
	ofile.close();

	return 0;
}


Second thing, I want to do it with a function (function for reading, and function for writing)
Last edited on
againtry (2313)
Modify your 2 while loops as follows:
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while (ifile1 >> std::noskipws >> ch)
    {
        ofile << ch;
    }
    
    while (ifile2 >> std::noskipws >> ch)
    {
        ofile << ch;
    }
Duthomhas (13206)
Is your desire to use std::vector some sort of requirement?
pmah (6)
The function opens file, reads as vector, saves into buffer. Now another function reads it and saves into a file.
seeplus (6591)
To read a file into a vector and then display:

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#include <iostream>
#include <fstream>
#include <vector>

int main() {
	std::ifstream ifs("input.txt");

	if (!ifs)
		return (std::cout << "Cannot open file\n"), 1;

	const std::vector<char> fdata((std::istream_iterator<char>(ifs >> std::noskipws)), std::istream_iterator<char>());

	for (const auto& f : fdata)
		std::cout << f;
}


PS To write the vector to a file:

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std::ofstream ofs("output.txt");

ofs.write(fdata.data(), fdata.size());


PPS. It's sometimes more convenient to read the file into a std::string rather than a std::vector - depending upon what, if any, manipulation of the container is required.

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

int main() {
	std::ifstream ifs("input.txt");

	if (!ifs)
		return (std::cout << "Cannot open file\n"), 1;

	const std::string fdata((std::istream_iterator<char>(ifs >> std::noskipws)), std::istream_iterator<char>());

	for (const auto& f : fdata)
		std::cout << f;

	std::ofstream ofs("output.txt");

	ofs.write(fdata.data(), fdata.size());
}

Last edited on
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