dyn array accounts[] = listaccounts(); //all accounts
array keys[accounts.length()];  //array for the private keys
dyn array addresses[]; //array for the addresses
//this for-loop just puts every private-key from a public-key which has at least one transaction
//into an array (key[]). this array will be later used to import the keys into the new wallet. 
for(i<accounts.length();i++) {

       if( listtransactions(accounts[i]) != empty){
       addresses[i]=getaddressesbyaccount(accounts[i]);
       key[i]=importprivkey(accounts[i]);
       
       } 

       

}

fstream f;

f.write(file, keys); //now save the private keys on a file

//this for loop will be used on the 
fstream.f;
dyn array keys[];

f.read(file, keys[]); //open the saved keys and put them into this  

for(i<keys.lenght();i++){

     importprivkey(keys[i]); //import every single key to the new wallet.dat

}