These functions can be used for data structure access the mtab file:
FILE * setmntent(const char *file, const char *mode)
int endmntent (FILE *stream)
struct mntent * getmntent (FILE *stream)
struct mntent * getmntent_r (FILE *stream, struct mentent *result, char *buffer, int bufsize)
int addmntent (FILE *stream, const struct mntent *mnt)
char * hasmntopt (const struct mntent *mnt, const char *opt)
For more details about these functions refer the man page.