getopt 함수의 정의를 찾고있는데요
#if (defined __STDC__ && __STDC__) || defined __cplusplus
# ifdef __GNU_LIBRARY__
/* Many other libraries have conflicting prototypes for getopt, with
differences in the consts, in stdlib.h. To avoid compilation
errors, only prototype getopt for the GNU C library. */
extern int getopt (int ___argc, char *const *___argv, const char *__shortopts);
# else /* not __GNU_LIBRARY__ */
extern int getopt ();
# endif /* __GNU_LIBRARY__ */
# ifndef __need_getopt
extern int getopt_long (int ___argc, char *const *___argv,
const char *__shortopts,