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To update data in a file, you can use the ofstream class along with the ios::app flag similar to appending. However, instead of appending, you can modify specific lines or sections within the file.

Here's an example code that demonstrates how to update data in a file using ofstream:

1#include <iostream>
2#include <fstream>
3
4int main() {
5  std::ofstream file("example.txt", std::ios::app);
6
7  if (file.is_open()) {
8    file << "This is an updated line";
9    file.close();
10    std::cout << "Data updated in file." << std::endl;
11  } else {
12    std::cout << "Unable to open file" << std::endl;
13  }
14
15  return 0;
16}