如何使用 C++ 在另一个程序中读取源代码的输出

Question

I think this is really hard to explain what I want. But, let me try. (I am trying to build a program for scoring student's programming homework)

There are a lot of simple source codes in C++. (Please think there are more than 100 code files )

// C:\homework1\studentA.cpp
int main()
{
    cout << "The answer is 456" << endl;
}

And This is question. As you can see, there are tons of code files and I cannot compile it and check it whether right or wrong one by one. So, I need to make scoring program for convenience.

How can I read the standard output (The answer is 456) in another program ? Is there any function for 'compiling source code' and 'save standard output' ?

Answer 1

I would use a bash script for this instead of C++. Something along the lines of:

g++ $filename
./a.out > student_answer.txt
diff -q student_answer.txt expected_answer.txt

Then, $? would tell you whether the answer was correct.

Answer 2

How can I read the standard output (The answer is 456) in another program?

You cannot do that without help from your operating system . Because you don't have (in general, according to the C++17 standard ) some "other program" running (read about processes ). When you have one, please thank your OS. Read some textbook about operating systems .

However, on Linux, you could just use popen(3) (or fork(2) , execve(2) , pipe(7) so pipe(2) , dup2(2) , waitpid(2) ) and on operating systems for which Qt has been ported (that includes Windows, but read about the WinAPI ), you could use QProcess .

If you are paranoid, consider using setuid and/or chroot techniques (perhaps with LXC ) on Linux to increase the security of your tool.

Look also inside the POCO framework library.