Compilare: user.c: In function ‘main’: user.c:15:11: warning: unused variable ‘i’ [-Wunused-variable] int n,i; ^ user.c:15:9: warning: unused variable ‘n’ [-Wunused-variable] int n,i; ^ user.c:9:11: warning: unused variable ‘f’ [-Wunused-variable] FILE *f = fopen(File_in,"r"); ^