将文本和行添加到文件的开头（C ++）

问题描述

我想要在文件开头添加行。

I'd like to be able to add lines to the beginning of a file.

我写的程序会从用户那里获取信息，然后准备写入文件。那个文件将是一个已经生成的diff，添加到开头的是描述符和标签，使它与Debian的DEP3 Patch标签系统兼容。

This program I am writing will take information from a user, and prep it to write to a file. That file, then, will be a diff that was already generated, and what is being added to the beginning is descriptors and tags that make it compatible with Debian's DEP3 Patch tagging system.

这需要跨平台，所以它需要在GNU C + +（Linux）和Microsoft C + +（和任何Mac自带）

This needs to be cross-platform, so it needs to work in GNU C++ (Linux) and Microsoft C++ (and whatever Mac comes with)

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推荐答案

请参阅答案：

通过使用作为输入文件和输出文件。之后，您可以使用和替换旧文件：

You can achieve such by using std::ifstream for the input file and std::ofstream for the output file. Afterwards you can use std::remove and std::rename to replace your old file:

#include <iostream>
#include <fstream>
#include <string>
#include <cstdio>

int main(){
    std::ofstream outputFile("outputFileName");
    std::ifstream inputFile("inputFileName");
    std::string tempString;

    outputFile << "Write your lines...\n";
    outputFile << "just as you would do to std::cout ...\n";

    outputFile << inputFile.rdbuf();

    inputFile.close();
    outputFile.close();

    std::remove("inputFileName");
    std::rename("outputFileName","inputFileName");

    return 0;
}

另一种不使用 code>或 rename 使用 std :: stringstream ：

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

int main(){
    const std::string fileName = "outputFileName";
    std::fstream processedFile(fileName.c_str());
    std::stringstream fileData;

    fileData << "First line\n";
    fileData << "second line\n";

    fileData << processedFile.rdbuf();
    processedFile.close();

    processedFile.open(fileName.c_str(), std::fstream::out | std::fstream::trunc);
    processedFile << fileData.rdbuf();

    return 0;
}

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