How to insert content at a specified location in a file using C++?

In C++, use the ofstream class to insert content at a specified location in the file: open the file and locate the insertion point. Insert content using the

How to use C++ to insert content at a specified location in a file?

In C++, you can use the ofstream class to insert content at a specified location in a file. Here are the steps on how to do it:

Preparation

First, you need to open the file using the ofstream object:

ofstream file("file_name.txt");

Position the insertion point

Next, you need to locate the place where you want to insert content. This can be achieved in the following ways:

// 定位到文件的偏移量为 offset 的位置
file.seekp(offset, ios::beg);

Insert content

After positioning the insertion point, you can use the << operator to insert content:

file << "要插入的内容";

Practical Case

Suppose there is a file named data.txt, the content is:

这是一行内容。

You want to insert "new content" into the second line of the file After that, you can do the following:

#include <iostream>
#include <fstream>

using namespace std;

int main() {
  // 打开文件
  ofstream file("data.txt");

  // 定位到第二行之后
  file.seekp(15, ios::beg); // 15 是第二行开头之前的字节数

  // 插入内容
  file << "新内容" << endl;

  return 0;
}

After saving and running this program, the contents of data.txt will become:

这是一行内容。
新内容

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