问题描述

我正在编写一个 C++ 应用程序，我需要读取系统命令的结果.

I am writing a C++ application and I need to read the result of a system command.

我或多或少地使用 popen() 如下所示:

I am using popen() more or less as shown here:

    const int MAX_BUFFER = 2048;
    string cmd="ls -l";
    char buffer[MAX_BUFFER];
    FILE *stream = popen(cmd.c_str(), "r");
    if (stream){
       while (!feof(stream))
       {
            if (fgets(buffer, MAX_BUFFER, stream) != NULL)
            {
               //here is all my code
            }
       }
       pclose(stream);
    }

我一直在尝试以不同的方式重新编写它.我看到了一些非标准的解决方案，例如:

I've been trying to re-write this in a different way. I saw some non-standard solutions like:

FILE *myfile;
std::fstream fileStream(myfile);
std::string mystring;
while(std::getline(myfile,mystring))
{
    // .... Here I do what I need
}

我的编译器不接受这个.

My compiler does not accept this though.

如何从 C++ 中的 popen 读取数据?

How can I read from popen in C++?

推荐答案

你的例子:

FILE *myfile;
std::fstream fileStream(myfile);
std::string mystring;
while(std::getline(myfile,mystring))

不起作用，因为尽管您非常接近，但标准库不提供可以从 FILE* 构造的 fstream.Boost iostreams 确实提供了一个iostream 可以从文件描述符构造，您可以通过调用 fileno 从 FILE* 获取一个.

Does't work because although you're very close the standard library doesn't provide an fstream that can be constructed from a FILE*. Boost iostreams does however provide an iostream that can be constructed from a file descriptor and you can get one from a FILE* by calling fileno.

例如:

typedef boost::iostreams::stream<boost::iostreams::file_descriptor_sink>
        boost_stream; 

FILE *myfile; 
// make sure to popen and it succeeds
boost_stream stream(fileno(myfile));
stream.set_auto_close(false); // https://svn.boost.org/trac/boost/ticket/3517
std::string mystring;
while(std::getline(stream,mystring))

不要忘记稍后pclose.

注意:较新版本的 boost 已经弃用了只需要一个 fd 的构造函数.相反，您需要将 boost::iostreams::never_close_handle 或 boost::iostreams::close_handle 之一作为强制第二个参数传递给构造函数.

Note: Newer versions of boost have deprecated the constructor which takes just a fd. Instead you need to pass one of boost::iostreams::never_close_handle or boost::iostreams::close_handle as a mandatory second argument to the constructor.

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