使用 strncpy 将字符串的两个部分复制到其他两个字符串

Question

I want to copy two parts of string s to two strings a and b:

#include <stdio.h>
#include <string.h>
int main()
{
   char s[] = "0123456789ABCDEF";
   char a[10];
   char b[6];
   strncpy( a, s, 10 );
   a[10] = '\0';
   printf("%s\n", a);
   strncpy( b, s+10, 6 );
   b[6] = '\0';
   printf("%s  %s\n", a, b);
   return 0;
}

Result:

0123456789
  ABCDEF

I had expected

0123456789
0123456789  ABCDEF

What has happened to a? Can anybody tell me what is wrong?

Answer 1

The arrays a and b do not contain strings. Declare them like

char a[11];
char b[7];

that is reserve one more element for the terminating zero character.

Otherwise these statements

a[10] = '\0';
b[6] = '\0';

use invalid indices.