Hello, Read line by line from data2.txt, compare with data1.txt lines, if match , remove , else append to a new file (result.txt) . mathces are exact string matches, both are text files. My code as follows. ------------------- #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ifstream ifs1("data1.txt"); ifstream ifs2("data2.txt"); ofstream ofs("result.txt"); string line1; string line2; while (!ifs2.eof()) { getline(ifs2,line2); while (!ifs1.eof()) { getline(ifs1,line1); if (line1!=line2) { ofs << line1; ofs << "\n"; } else { } } } return 0; } ------------------------- data1.txt : This is line 1 This is line 2 This is line 3 This is line 4 This is line 5 data2.txt This is line 5 This is line 1 Result.txt should be: --------------------- This is line 2 This is line 3 This is line 4 But I don't get the required results. Appreciate your assistance. thanks.

Correction : ------------ Read line by line from data2.txt, compare with data1.txt lines, if match , do nothing (NOT remove) , else append to a new file (result.txt) . Thx.