C++ 使用 ofstream 附加到文件
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/26084885/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
appending to a file with ofstream
提问by Wojtek
I have a problem with appending a text to a file. I open an ofstreamin append mode, still instead of three lines it contains only the last:
我在将文本附加到文件时遇到问题。我ofstream在追加模式中打开一个，它仍然只包含最后一行而不是三行：
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
ofstream file("sample.txt");
file << "Hello, world!" << endl;
file.close();
file.open("sample.txt", ios_base::ate);
file << "Again hello, world!" << endl;
file.close();
file.open("sample.txt", ios_base::ate);
file << "And once again - hello, world!" << endl;
file.close();
string str;
ifstream ifile("sample.txt");
while (getline(ifile, str))
cout << str;
}
// output: And once again - hello, world!
So what's the correct ofstreamconstructor for appending to a file?
那么ofstream附加到文件的正确构造函数是什么？
回答by dynamic
I use a very handy function (similar to PHP file_put_contents)
我使用了一个非常方便的函数（类似于 PHP file_put_contents）
// Usage example: filePutContents("./yourfile.txt", "content", true);
void filePutContents(const std::string& name, const std::string& content, bool append = false) {
std::ofstream outfile;
if (append)
outfile.open(name, std::ios_base::app);
else
outfile.open(name);
outfile << content;
}
When you need to append something just do:
当您需要附加某些内容时，请执行以下操作：
filePutContents("./yourfile.txt","content",true);
Using this function you don't need to take care of opening/closing. Altho it should not be used in big loops
使用此功能您无需关心打开/关闭。尽管它不应该在大循环中使用
回答by macfij
Use ios_base::appinstead of ios_base::ateas ios_base::openmodefor ofstream's constructor.
使用ios_base::app代替ios_base::ateas ios_base::openmodeforofstream的构造函数。
