在 C++ 中使用流写入文件
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writing to a file using stream in C++
提问by venkysmarty
I want to some text to output to a file. I heard that it is better to stream the data rather than creating a large string and outputing that. Presently I am creating a large string and outputing to a file. Request to provide an sample code on how to stream a data and write to a file using C++.
我想要一些文本输出到文件。我听说最好是流式传输数据，而不是创建一个大字符串并输出它。目前我正在创建一个大字符串并输出到一个文件。请求提供有关如何使用 C++ 流式传输数据和写入文件的示例代码。
Thanks!
谢谢！
回答by Armen Tsirunyan
#include <fstream>
int main()
{
std::ofstream fout("filename.txt");
fout << "Hello";
fout << 5;
fout << std::endl;
fout << "end";
}
Your file now contains this:
您的文件现在包含以下内容：
Hello5
end
See more info on std::ofstreamfor details.
有关详细信息，请参阅有关std::ofstream的更多信息。
HTH
HTH
回答by CashCow
File writing already uses buffering. If it is not efficient for you, you can actually modify the filebuf, eg increase its size or use a custom one.
文件写入已经使用缓冲。如果它对您来说效率不高，您实际上可以修改filebuf，例如增加其大小或使用自定义的。
Avoid doing unnecessary flushes of your buffer, which is done with endl. That is the most "abused" feature of file-writing.
避免对缓冲区进行不必要的刷新，这是使用 endl 完成的。这是文件写入最“滥用”的功能。
The simplest way to create a file-stream for outputting is:
创建用于输出的文件流的最简单方法是：
#include <fstream>
int main( int argc, char * argv[])
{
if( argc > 1 )
{
std::ofstream outputFile( argv[1] );
if( outputFile )
{
outputFile << 99 << '\t' << 158 << '\n'; // write some delimited numbers
std::vector< unsigned char > buf;
// write some data into buf
outputFile.write( &buf[0], buf.size() ); // write binary to the output stream
}
else
{
std::cerr << "Failure opening " << argv[1] << '\n';
return -1;
}
}
else
{
std::cerr << "Usage " << argv[0] << " <output file>\n";
return -2;
}
return 0;
}
