pollution: FILE
typedef struct __FILE FILE; 

pollution: fgetgrent
struct group* fgetgrent(FILE*); 

pollution: fgetgrent_r
int fgetgrent_r(FILE* restrict, struct group* restrict, char* restrict, size_t, struct group** restrict); 

pollution: getgrent_r
int getgrent_r(struct group* restrict, char* restrict, size_t, struct group** restrict); 

pollution: opengr
FILE* opengr(void);