Relationship between cpp files? How can one get and write the value of a variable from one cpp to another?

Question

linux

I am making two cpp files to build a library from them using makefile in LINUX
I need to write the values ​​of the variables discretX, discretY from function1.cpp to function2.cpp
How to do this?
function.h

struct InfaboutChanell
{ 
    int chanellcount;
    int analogChanell;
    int discretChanell;
};
void writeCfgFile (); 
void writeBinaryFile();

function1.cpp

#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include "functions.h"
using namespace std;


 struct Station station;
   void writeCfgFile(){

        ofstream file("fileConfiguration.cfg");
       //The information about count of channels
       struct InfaboutChanell infaboutChanell;
       infaboutChanell.chanellcount=14;
       const int analogX =6;
       infaboutChanell.analogChanell=analogX;
       const int discretX=8;
       infaboutChanell.discretChanell=discretX;  
       //проверка на сумму каналов
       int sum;
       sum = infaboutChanell.analogChanell+infaboutChanell.discretChanell;
       if (sum != infaboutChanell.chanellcount)
       {
           cout << "Please enter correct count of channels: " <<'\n'; 
       }
       file<<infaboutChanell.chanellcount<<","<<infaboutChanell.analogChanell<<"A"<<","<<infaboutChanell.discretChanell<<"D"<<"\n";
      
       file.close();
   
}

function2.cpp

#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include "functions.h"
using namespace std;

struct GeneralInf inf;
struct InfaboutChanell aboutchanell;


void writeBinaryFile(){
     // Create Binary file
    fstream binary_file("D:\\Struct\\Struct\\ComtradeFormat\\fileConfiguration.dat",ios::out|ios::binary|ios::app);
    if(!binary_file)
    {
        cout << "Cannot open file.\n";
        return 1;
    }

    int i=0;
    int n=0;
    int timestamp =0;

    for (i=0; i<=generalinformation.ensamp; i++){
        n = i+1;
        binary_file.write((char *) &n, sizeof n);
        timestamp = i*1000;
        binary_file.write((char *) &timestamp, sizeof timestamp);  

        // Value of analog channels
       short analogValue<b>  [analogX]</b>;
        for(int i=0; i<analogX; i++)
         
            analogValue[i] = rand() % 20000 - 10000;
        binary_file.write((char *) &analogValue, sizeof analogValue);

         unsigned __int16 m_bytesCount = 0;
         m_bytesCount = discretX / 16;
         if (discretX % 16){
             m_bytesCount++;
         }

        int ChValue<b> [discretX]</b> = {1, 1, 1, 0, 0, 0, 0, 0};
   
        for(int i = 0; i < discretX; ++i)
        {
            if(ChValue[i] == 1)
                m_bytesCount |= 1 << i;
        }

        binary_file.write((char *) &m_bytesCount, sizeof m_bytesCount);
    }

    binary_file.close();

Answer 1

Create global variables in the function.h file and use them to exchange data in *.cpp files.
(so-so advice)

Answer 2

Return values ​​from one function and pass them to another as parameters.
You can return 2 values ​​in a struct or with reference input parameters. Example.

void writeCfgFile(int & directX, int & analogX){
       analogX =6;
       discretX=8;
}
void writeBinaryFile(int directX, int analogX) {
}
main() {
int analog, direct;
writeCfgFile(direct, analog);
writeBinaryFile(direct, analog);
}

When you need to return many values, they are combined into a structure and filled in the structure in the same way.
Global variables are, of course, simple and work, but this is not the right approach.

Answer 3

In one module a global variable, and extern in another.

Answer 4

Well, you can transfer a pointer to an object, but this is possible if you need to transfer and change it everywhere. And so set get properties to describe.