Compilare: user.cpp: In function ‘void extract_header(FILE*, FILE*)’: user.cpp:84:24: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(c,1025,f); ^ user.cpp: In function ‘void extract_columns(FILE*, FILE*)’: user.cpp:116:24: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(c,1025,f); ^