Compilare: user.cpp: In function ‘void _read()’: user.cpp:9: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void _write()’: user.cpp:14: warning: format ‘%ld’ expects type ‘long int*’, but argument 3 has type ‘long long int’ user.cpp:14: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result