writting a binary in c++ - c++

Question

So i have this program that supposedly reads any file (e.g images, txt) and get its data and creates a new file with that same data. The problem is that i want the data in an array and not in a vector and when i copy that same data to char array, whenever i try to write those bits into a file it doesnt write the file properly.
So the question is how can i get the data from std::ifstream input( "hello.txt", std::ios::binary ); and save it an char array[] so that i can write that data into a new file?
Program:
#include <stdlib.h>
#include <string.h>
#include <fstream>
#include <iterator>
#include <vector>
#include <iostream>
#include <algorithm>
int main()
{
FILE *newfile;
std::ifstream input( "hello.txt", std::ios::binary );
std::vector<unsigned char> buffer(std::istreambuf_iterator<char>(input), {});
char arr[buffer.size()];
std::copy(buffer.begin(), buffer.end(), arr);
int sdfd;
sdfd = open("newhello.txt",O_WRONLY | O_CREAT);
write(sdfd,arr,strlen(arr)*sizeof(char));
close(sdfd);
return(0);
}

Answer 1

Try this:
(It basically uses a char*, but it's an array here. You probably can't have an array in the stack in this case)
#include <iostream>
#include <fstream>
int main() {
std::ifstream input("hello.txt", std::ios::binary);
char* buffer;
size_t len; // if u don't want to delete the buffer
if (input) {
input.seekg(0, input.end);
len = input.tellg();
input.seekg(0, input.beg);
buffer = new char[len];
input.read(buffer, len);
input.close();
std::ofstream fileOut("newhello.txt");
fileOut.write(buffer, len);
fileOut.close();
// delete[] buffer; u may delete the buffer or keep it for further use anywhere else
}
}
This should probably solve your problem, remember to always have the length (len here) of the buffer if you don't want to delete it.
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