用C/C ++编写日志文件 [英] Writing a Log file in c/c++

问题描述

我想用c ++编写一个日志文件. 我正在处理某些事物，因此我需要维护我正在处理的事物的属性的日志，以便可以恢复到此日志文件以查看特别令我感兴趣的事物的属性. 有人可以帮助我实现这一目标吗?

I want to write a log file in c++. I am processing certain things and thus i need to maintain a log of the properties of the things that i process so that i could revert back to this log file to see the properties of anything that interests me in particular.. Could someone help me in achieving this?

推荐答案

(以我的经验)标准的日志记录方法是使用stdout或stderr流.在C ++中，要使用这些功能，您需要包含iostream，并按以下方式使用:

The standard method of logging (in my experience) is to use either the stdout or stderr streams. In C++ to use these you would need to include iostream, and use as below:

#include <iostream>

int main(int argc, char* argv[])
{
  using std::cout;
  using std::cerr;
  using std::endl;

  cout << "Output message" << endl;
  cerr << "Error message" << endl;
}

但是，这只能实现到通常在终端上输出的那些输出.如果要使用这些标准流方法(可读性很强)来输出到文件，则必须以某种方式重定向输出.一种方法是使用cstdio提供的freopen函数.这样做是打开一个文件，然后将给定的流移动到该文件.有关文档，请参见此处.一个例子是:

This, however, only achieves printing to those outputs, which usually end up at a terminal. If you want to use these standard stream methods (which are quite readable) to output to a file, then you have to redirect your output somehow. One way of doing this is by using the freopen function, provided by cstdio. What this does is open a file, and moves a given stream to that file. See here for documentation. An example would be:

#include <iostream>
#include <cstdio>

int main(int argc, char* argv[])
{
  using namespace std;
  freopen( "output.txt", "w", stdout );
  freopen( "error.txt", "w", stderr );

  cout << "Output message" << endl;
  cerr << "Error message" << endl;
}

(为简洁起见，我已更改为using namespace std;.)

(I've changed to using namespace std; there just for conciseness.)

您要将标准输出流stdout(由cout使用)移动到output.txt(在写模式下)，并且您将stderr(由cerr使用)在写入模式下也可以访问error.txt.

You're moving the standard output stream stdout (which is used by cout) to output.txt (in write mode), and you're moving stderr (which is used by cerr) to error.txt also in write mode.

希望这能解决问题.

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