help plz! find email in an .txt

[lostinthesauce]

hey everyone i am new to programming and have been working on this code for about two days with no solution. the code is supposed to find a email address withing a text file starting from the @ symbol back then to the end and find if it has a dot. as the code stands now all it dose is output blank lines. Any help will be appreciated thank you =)

// Libraries
#include <fstream> 
#include <iostream> 
#include <string> 
#include <iomanip>
using namespace std;

// Compiler specific definitions
// None

// Programmer defined functions
struct userFile 
{ 
  string userInput;
  string userOutput;   
}; 

char line(string  line)                        
{
  char userSelection = ' ';
  int i = 0;
  //if sting isent empty
  if ( line.length() != 0){            
	  //loops every char looking for blanks
    while (i <  line.length()) 
	{
		//locates the postion
      userSelection=  line[i]; 
	  // if char isent blank
      if (userSelection != ' ') break; 
	  //goes to next char
      i ++;                             
    }
  }
  return userSelection;
}
//funtion to find input
userFile userInput(userFile& info)           
{
  string lines;                        
  //prompt the user
  cout << "Enter input file name [default: " << info.userInput << "]: ";       
  getline(cin, lines);   
  char userSelection = line(lines);    
  if (userSelection!= ' ')
  {                   
    info.userInput = lines; 
    info.userOutput = lines;     
  }  
  return info;   
}
//function find output file
userFile userOutput(userFile& info)            
{
  string lines;                          
   //prompt user
  cout << "Enter output file name [default: " << info.userOutput<< "]: ";       
  getline(cin, lines);                      
  char userSelection = line(lines);    
  if (userSelection != ' ')                  
    info.userOutput = lines;              
  return info;   
}

bool isValidEmailCharacter(char c)

{

bool result = false;

if (c >='A' && c <= 'Z' || c >= 'a' && c <= 'z'|| c >= '0' && c <='9' ||c =='.'||c =='-' || c =='+') result = true;

return result;

}
//prints out user userinput
void print(userFile& info)           
{
  cout << "Input file : "<< info.userInput << endl;
  cout << "Output file: "<< info.userOutput<< endl;
}

//Main program  
int main() 
{ 


  userFile info;
  //default for input
  info.userInput   = "fileContainingEmails.txt";   
  //default for output
  info.userOutput  = "copyPasteMyEmails.txt";      
 
  //gets input file from user
 userInput (info);  
  //gets outputfile from user
  userOutput(info);
  //opens selected files
  string line;
  ifstream fin;
 
  string lineFromFile;
  fin.open (info.userInput.c_str());
  if (!fin.good()) throw "File input error";
 


  const int MAX_EMAILS = 1000;
  int nEmails = 0;
  string email[MAX_EMAILS];

  while(true)
  {
    if (!fin.good()) break;
    char s;
   char e;
    string lineFromFile;
    getline(fin, lineFromFile);

  for (int i = 0; i < lineFromFile.length(); i++) // for each character in the string
  {
    
    if(lineFromFile[i] == '@')
      
    {

      for (s = i; s >= 0; s--)
      {
        if (!isValidEmailCharacter(lineFromFile[s]));

      for (e = i; e < lineFromFile.length(); e++)
      {
        if (!isValidEmailCharacter(lineFromFile[e]))
	
		{    
            if (nEmails > MAX_EMAILS)
			{
				email[nEmails++] == lineFromFile.substr(s, e-s);
		
			}
		     break;
	  }
        
  
      }
    }
  }
}
    for (int z=0;z<=nEmails;z++)
  {
  cout <<email[z] << endl;
  }
}

  print(info);   
cin.get();
  return 0; 
}