printf--动态指定输出格式长度

char a1[] = {'A', 'B', 'C'};
char a2[] = "world";

printf("[%.*s][%.*s]\n", 2, a1, 10, a2);
printf("[%.*s][%.*s]\n", sizeof(a1), a1, sizeof(a2), a2);
printf("[%-*d]\n", 4, 'A'); //产生"65 "
printf("[%-*s]\n", 4, "A"); //产生"A  "
printf("[%#0*X]\n", 8, 128); //产生"0X000080"，"#"产生0X
printf("[%*.*f]\n", 10, 2, 3.1415926); //产生" 3.14"