var fs = require('fs');
   //Making newLink.txt file empty.
/**************************************/
fs.writeFile('your url here/newLink.txt',' ',function (err)
  {
    if (err) return console.log(err);
});
/**************************************/
//We collect the links from MainLink.txt file to compare with USEDLink.txt file fo any duplicate
var mainFile=fs.readFileSync('your url here/MainLink.txt', 'utf8',function (err)
  {
    if (err) return console.log(err);
});
mainFile=mainFile.split('\n');
mainFile =mainFile.filter(function( element ) {
   return element;
});

var usedLink=fs.readFileSync('your url here/USEDLink.txt', 'utf8',function (err)
  {
    if (err) return console.log(err);
});
usedLink=usedLink.split('\n');
usedLink=usedLink.filter(function( element ) {
   return element;
});

//We look for duplicate link
var counter=1;
var linkToDlete=3;// 0 is the first line in MainLink file

for(var i in mainFile){
for(var j in usedLink){
if(mainFile[linkToDlete].search(usedLink[j])>-1 && linkToDlete>0 ){
var deletedLink= usedLink[j];
var duplicateL=counter+1;
console.log('Position of identical link in USEDLink.txt file  is  in line number : '+/*mainFile[linkToDlete].search(usedLink[j])+*/' --> '+duplicateL)
counter++;
}
else if(mainFile[linkToDlete].search(usedLink[j])>-1 && linkToDlete===0 ){
var deletedLink= usedLink[j];
var duplicateL=counter;
console.log('Position of identical link in USEDLink.txt file  is  in line number : '+/*mainFile[linkToDlete].search(usedLink[j])+*/' --> '+duplicateL)
counter++;
}
else if(mainFile[i].search(usedLink[j])===-1){
var noDuplicateL= counter;
counter++;
}
}
break;
}
/*A duplicate link was found and deleted the rest of the links are sent to an other file*/
if(duplicateL!==undefined && delete mainFile[linkToDlete] ){
console.log('The link '+deletedLink+' is a duplicate.');
//console.log('Position of identical link in USEDLink.txt file  is  in line number : '+duplicateL);
fs.writeFile('your url here/link.txt',mainFile+'\n',function (err)
  {
    if (err) return console.log(err);
});
//console.log(mainFile)
for(var i in mainFile)/*We send the other links withouth the duplicated link to a New file*/{
fs.appendFile('your url here/newLink.txt',mainFile[i]+'\n',function (err)
  {
    if (err) return console.log(err);
});
}
}
else if(noDuplicateL!==undefined )/*No duplicate link was found*/{
console.log('The link '+mainFile[linkToDlete]+' is not a duplicate.');
}
else if(mainFile.length<1){
console.log("The MainLink.txt file is empty. ")
}
else if(usedLink.length<1){
console.log("The USEDLink.txt file is empty. ")
}