C++ (pre C++11) fstream initialized by sstream - c++

Question

I am trying to open other process stdin and write to it, using C++, no dup() and other C tricks. But unfortunately, fstream constructor taking string seems to be available only from C++11 ( source:http://www.cplusplus.com/reference/fstream/fstream/fstream/ )
#include <iostream>
#include <fstream>
#include <sstream>
//using namespace std;
int main()
{
pid_t pid = fork();
if (pid == 0)
{
// std::cout << "child:" << i << std::endl;
std::string line;
std::cin.sync();
std::cout << "child got message:" << std::endl;
while ( std::getline(std::cin, line) )
{
std::cout << line << std::endl;
}
std::cout << "child done receiving" << std::endl;
}
else{
//std::cout << "parent"<<std::endl;
std::ifstream file("stdin", std::ios::in);
if(file.is_open())
{
std::string tmp, str;
std::stringstream pidstr;
pidstr << "/proc/" << pid << "/fd/0";
while ( std::getline(file, tmp) )
str += tmp + "\n";
std::fstream other( (pidstr.str().c_str()), std::ios::out);
other << str ;
}
}
return 0;
}
I have four questions:
Is "pidstr.str().c_str()" most C++ way to do it? Looks ugly to me.
Is that proper C++ way or maybe there are better alternatives?
Since, as far as I know, getline() is blocking, can I ommit cin.sync(), expecting child to wait for input in while ?
Why do I need to press enter twice, (regardless if i have getchar in child commented out or not(!))
Thanks for understanding.
EDIT: This compiles, and produces desired output, using Code:Blocks, Linux 13.04
EDIT2: No, apparently this does NOT produce desired output. I've added some changes: parent waits for child to exit (not important here).
But also changed this (in child) :
while ( std::getline(std::cin, line) )
{
std::cout << line << std::endl;
}
std::cout << "child done" << std::endl;
to this :
std::getline(std::cin, line);
int lines; // this is single line sent as first from parent, containing int
std::istringstream toint(line);
toint >> lines;
std::cout << "how much lines should it read:" << lines << std::endl;
And it appears that child will wait for anything on stdin, then prints out that what was sent from parent. Really, sometimes I wonder how should i consider C++ as better than plain C :/