How to solve C++ runtime error: 'file read/write error'?

How to solve C runtime error: 'file read/write error'?

During the C programming process, we often encounter file read and write errors. One of the most common errors is 'file read/write error'. This kind of error usually leads to the interruption of program operation and brings some trouble to developers. This article will explain the causes of this error and provide some solutions.

First, we need to understand the cause of 'file read/write error'. This error usually occurs when a problem occurs while trying to read or write a file. Possible reasons include the file not existing, the file being occupied by other programs, insufficient permissions, etc. Next, let's look at how to solve these problems.

1. Check if the file exists: You should check if the file exists before trying to read or write to it. You can use the file system-related functions to determine whether the file exists, for example, use the is_open() function of the std::ifstream class to determine whether the file is successfully opened. If the file does not exist, you can take some steps, such as creating a new file.

#include <iostream>
#include <fstream>

int main() {
    std::ifstream file("example.txt");
    if (!file.is_open()) {
        std::cout << "File does not exist." << std::endl;
        // 创建新文件
        std::ofstream newFile("example.txt");
    }
    // 文件存在，继续读取或写入操作
    return 0;
}

2. Check whether the file is occupied by other programs: Sometimes the file is being used by other programs, resulting in the inability to read or write. In this case, we can try waiting for some time and try reading or writing the file again. You can use the std::this_thread::sleep_for() function to try again after a period of time.

#include <iostream>
#include <fstream>
#include <chrono>
#include <thread>

int main() {
    std::ofstream file("example.txt");
    if (!file.is_open()) {
        std::cout << "Failed to open file." << std::endl;
        return -1;
    }
    // 尝试写入文件，如果失败则等待1秒后再次尝试
    bool success = false;
    while (!success) {
        try {
            file << "Hello, world!" << std::endl;
            success = true;
        } catch (std::ofstream::failure e) {
            std::cout << "Unable to write to file." << std::endl;
            std::this_thread::sleep_for(std::chrono::seconds(1));
        }
    }
    // 写入成功后关闭文件
    file.close();

    return 0;
}

3. Check file permissions: Another possible cause is insufficient file permissions, preventing the file from being read or written. In this case, we need to check the permissions of the file and change the permissions of the file accordingly. You can use file system related functions, such as chmod() to modify file permissions.

#include <iostream>
#include <fstream>
#include <sys/stat.h>

int main() {
    std::ofstream file("example.txt");
    if (!file.is_open()) {
        std::cout << "Failed to open file." << std::endl;
        return -1;
    }
    // 尝试写入文件，如果失败则更改文件权限
    bool success = false;
    while (!success) {
        try {
            file << "Hello, world!" << std::endl;
            success = true;
        } catch (std::ofstream::failure e) {
            std::cout << "Unable to write to file." << std::endl;
            // 更改文件权限
            chmod("example.txt", S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH);
        }
    }
    // 写入成功后关闭文件
    file.close();

    return 0;
}

Summary: In C programming, 'file read/write error' is a common but solvable problem. We can solve this error by checking whether the file exists, whether the file is occupied by other programs, and file permissions. If it cannot be solved, you can try other file system-related operations, such as moving files, deleting files, etc. Hopefully the solutions provided in this article will help you handle 'file read/write error' errors better.

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