c - 是否可以仅打印出 C 字符串的特定部分，而不制作单独的子字符串？

Question

假设我有以下内容:

char* string = "Hello, how are you?";

是否可以只打印出这个字符串的最后 5 个字节？仅前 5 个字节怎么样？ printf 是否有一些允许这样做的变体？

Answer 1

Is it possible to print out only the last 5 bytes of this string?

是的，只需传递一个指向倒数第五个字符的指针。您可以通过 string + strlen(string) - 5 来确定。

What about the first 5 bytes only?

使用精度说明符:%.5s

#include <stdio.h>
#include <string.h>
char* string = "Hello, how are you?";

int main() {
  /* print  at most the first five characters (safe to use on short strings) */
  printf("(%.5s)\n", string);

  /* print last five characters (dangerous on short strings) */
  printf("(%s)\n", string + strlen(string) - 5);

  int n = 3;
  /* print at most first three characters (safe) */
  printf("(%.*s)\n", n, string);

  /* print last three characters (dangerous on short strings) */
  printf("(%s)\n", string + strlen(string) - n);
  return 0;
}