How to open a file using C++?

In C++, use the fstream header file and the ifstream or ofstream classes to open files. The specific steps are as follows: Open the file for reading operation: ifstream ifs("file name"); Open the file for writing operation: ofstream ofs("file name");

How Open file using C++?

Opening a file in C++ involves using the fstream header file and the ifstream or ofstream class. The following are the steps on how to open a file in C++:

Open a file for reading

ifstream ifs("input.txt");
if (ifs.is_open()) {
    // 文件已成功打开，可以读取数据
} else {
    // 文件打开失败，处理错误
}

Open a file for writing

ofstream ofs("output.txt");
if (ofs.is_open()) {
    // 文件已成功打开，可以写入数据
} else {
    // 文件打开失败，处理错误
}

Practical case: reading and writing files

#include <iostream>
#include <fstream>

using namespace std;

int main() {
    // 打开文件进行读操作
    ifstream ifs("input.txt");
    if (ifs.is_open()) {
        string line;
        while (getline(ifs, line)) {
            // 从文件中读取一行数据并处理它
            cout << line << endl;
        }
        ifs.close(); // 读取完成后关闭文件
    }

    // 打开文件进行写操作
    ofstream ofs("output.txt");
    if (ofs.is_open()) {
        ofs << "Hello, world!" << endl; // 将数据写入文件
        ofs.close(); // 写入完成后关闭文件
    }

    return 0;
}

In this example, input.txt is used to read data, while output.txt is used to write data.

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