prefix.cpp: In function 'int main()': prefix.cpp:22: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result prefix.cpp:25: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result prefix.cpp:26: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result prefix.cpp:28: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result prefix.cpp:33: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result