在 C++ 中读取 popen 结果
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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