Read console output in C++ and convert file pointer FILE* to istream

solved problem:

• 1. After executing the bash command of the system, get its output (similar to python's subprocess module)
• 2. Convert the output from FILE* to std::istream, which is convenient for processing in the way of C++

Get the output of the bash command: http://www.cnblogs.com/caosiyang/archive/2012/06/25/2560976.html

Convert the file pointer FILE* to istream: https://stackoverflow.com/questions/2746168/ how-to-construct-ac-fstream-from-a-posix-file-descriptor

This article adopts the scheme given by Mark in the above question (it seems that the scheme is also used in the boost library), that is, redefines a buffer class, see the following The fdinbuf class in the link and how it is used in fdistream: http://www.josuttis.com/cppcode/fdstream.html


Sample code (see attachment for complete program):

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <stdio.h>
#include <string>
#include <memory>
#include "fdstream.hpp"

//using namespace std;
using std::string;

std::shared_ptr<boost::fdistream> eg_read_from_bash_output(const char *cmd) {
	::FILE *fp = ::popen(cmd, "r");
	if (!fp) {
		throw string("count not open PIPE");
	}
	//boost::fdistream fs(fileno(fp)); //Note that because the parent class istream does not have operator =, the changed class cannot be used as the return value.
	//To use fs as the return value, use std::shared_ptr to encapsulate: http://en.cppreference.com/w/cpp/memory/shared_ptr/shared_ptr
	std::shared_ptr<boost::fdistream> pfi(new boost::fdistream(fileno(fp)));
	return pfi;
}

int main(){
 	auto pfi = eg_read_from_bash_output("cat hello.txt");
	boost::fdistream& fs = *pfi; 	

 	string line;
	while (std::getline(fs, line)) {
		std::cout << line << std::endl;
	}
	
}