用C ++解析文件

Question

I have created code that will execute a file and then will execute code and store that code into a .csv filer shown below

#include <string>
#include <iostream>
#include <sstream>
#include <stdlib.h>
#include <fstream>
using namespace.std;

int main(){
    int foo = 10;
    for(int i =1; x<=8 x++){

      std::stringstream ss;
      ss << "echo " << foo << " | ./triad >> scaling.csv"<<'\n';
      std::cout << ss.str().c_str() <<std::endl;
      system(ss.str().c_str());

      foo=foo*10
    }
return 0;
}

The triad program is one that I am given and cannot change. I run basically 10 iterations on it and print the output of that to a scaling.csv, to give me the following output

Length:        10    MFLOP/s:    2541.29
Length:       100    MFLOP/s:    2515.85
Length:      1000    MFLOP/s:    3616.75

and so on...

does anyone know how to parse that file so instead my scaling.csv will look something like this

Key,Value
10,2541.29
100,2515.85
1000,3616.75

Again what gets printed out by triad I cannot change.

Answer 1

Simple:

int main()
{
     string s;
     int key; float val;
     ifstream out("out.txt");
     ofstream in("in.txt);

    in >> s;
    in >> key; // key == 10
    in >> s;
    in >> val; // val == 2541.29
}

Put this into a function and you have:

void extract(std::istream& in, int& key, float& val)
{
    // same as above
}

int main()
{
    int key; float val;
    while (in)
    {
        extract(in, key, val);
        out << key << ", " << val << std::endl;
    }
}

But we're performing the input after we check the stream. This can cause problems. Let's have the extract function return a reference to the stream:

std::ios& extract(std::istream& in, int& key, float& val)
{
    // same as above
}

int main()
{
    int key; float val;
    while (extract(in, key, val))
//         ^^^^^^^^^^^^^^^^^^^^^
    {
        out << key << ", " << val << std::endl;
    }
}