strncpy()函数类似于strcpy()函数，不同之处在于它只从源字符串复制指定数量的字符到目标字符串。
char *strncpy(char *str1, const char *str2, size_t n)str1 - 目标字符串。复制源字符串str2的前n个字符到其中的字符串。
str2 - 源字符串
`n - 需要复制的源字符串的字符数。
在将源字符串的n个字符复制到其中之后，它返回指向目标字符串的指针。
#include <stdio.h>
#include <string.h>
int main () {
char str1[20];
char str2[25];
/* The first argument in the function is destination string.
* In this case we are doing full copy using the strcpy() function.
* Here string str2 is destination string in which we are copying the
* specified string
*/
strcpy(str2, "welcome to beginnersbook.com");
/* In this case we are doing a limited copy using the strncpy()
* function. We are copying only the 7 characters of string str2 to str1
*/
strncpy(str1, str2, 7);
printf("String str1: %s\n", str1);
printf("String str2: %s\n", str2);
return 0;
}输出：
String str1: welcome
String str2: welcome to beginnersbook.com