Compilare: user.c:4: warning: return type of ‘main’ is not ‘int’ user.c: In function ‘main’: user.c:32: warning: implicit declaration of function ‘exit’ user.c:32: warning: incompatible implicit declaration of built-in function ‘exit’ user.c:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:6: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result