Why is iostream::eof inside a loop condition considered wrong?

The iostream::eof in a loop is considered as wrong because we haven’t reached the EOF. So it does not mean that the next read will succeed.

When we want to read a file using file streams in C++. And when we use a loop to write in a file, if we check the end of file using stream.eof(), we are actually checking whether the file has reached end or not.

Example Code

#include<iostream> #include<fstream> using namespace std; int main() { ifstream myFile("myfile.txt"); string x; while(!myFile.eof()) { myFile >> x; // Need to check again if x is valid or eof if(x) { // Do something with x } } }

When we are using the stream directly in a loop, We will not check the condition again.

Example Code

#include<iostream> #include<fstream> using namespace std; int main() { ifstream myFile("myfile.txt"); string x; while(myFile >> x) { // Do something with x // No checks needed! } }