字符串函数 bcmp bcopy bzero memccpy memchr memcmp memcpy memicmp memmove memset movmem setmem stpcpy strcat strchr strcmp strcmpi strcpy strcspn strdup stricmp strlen strlwr strncat strncmp strncmpi strncpy strnicmp strpbrk strrev strset strstr strtok strupr 数学函数 ab