Comparing strings behaves different on mingw and on ubuntu gcc

I am trying to compare two strings. Here is the code that I have.

string line;
getline(cin, line);
if(line.compare("% Input alphabet")==0)
dosomething;

The problem is the following code works correctly when using mingw on a windows machine but when I run the same code on my ubuntu vm it does not execute dosomething method. I compiled my program and ran the following commands

On windows

a.exe < input.txt

On Ubuntu

./a.out < input.txt