c - printf中的 "%.6d"是什么意思

Question

%.6d是什么意思:

printf("%s.%.6d len:%d ", timestr, header->ts.tv_usec, header->len);

是不是打错字了？

看来 %.6d 和 %6d 是一样的。

Answer 1

%.6d

In the .precision format for integer specifiers (d, i, o, u, x, X), precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer.

%6d

The width (here 6) specifies the minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.

例子:

printf("%.6d\n%6d",1,1);

输出:

000001
     1