/// read from the process' output stream
/// data is stored in the given buffer, at most max_len bytes
/// read from the process' output stream
/// data is stored in the given buffer, at most max_len bytes
/// close program's output stream
void CloseOut();
/// read from the process' error stream
/// data is stored in the given buffer, at most max_len bytes
/// close program's output stream
void CloseOut();
/// read from the process' error stream
/// data is stored in the given buffer, at most max_len bytes