char *strcpy(char *dest, const char *src);

#include <string.h>
main(){
 char a[30] = "string(1)";
 char b[] = "string(2)";
 printf("before strcpy() :%s\n", a);
 printf("after strcpy() :%s\n", strcpy(a, b));
}

before strcpy() :string(1)
after strcpy() :string(2)

 char * strncpy(char *dest, const char *src, size_t n);

#include<stdio.h>
#include<string.h>
int main(void){
 char dest1[20];
 char src1[] = "abc";
 int n1 = 3;
 char dest2[20]="********************";
 char src2[] = "abcxyz";
 int n2 = strlen(src2)+1;
 char dest3[100] = "http://see.xidian.edu.cn/cpp/shell/";
 char src3[6] = "abcxyz"; // 没有'\0'
 int n3 = 20;
 char dest4[100] = "http://see.xidian.edu.cn/cpp/u/yuanma/";
 char src4[] = "abc\0defghigk";
 int n4 = strlen(src3);
 strncpy(dest1, src1, n1); // n1小于strlen(str1)+1，不会追加'\0'
 strncpy(dest2, src2, n2); // n2等于strlen(str2)+1，恰好可以把src2末尾的'\0'拷贝到dest2
 strncpy(dest3, src3, n3); // n3大于strlen(str3)+1，循环拷贝str3
 strncpy(dest4, src4, n4); // src4中间出现'\0'
 printf("dest1=%s\n", dest1);
 printf("dest2=%s, dest2[15]=%c\n", dest2, dest2[10]);
 printf("dest3=%s\n", dest3);
 printf("dest4=%s, dest4[6]=%d, dest4[20]=%d, dest4[90]=%d\n", dest4, dest4[6], dest4[20], dest4[90]);
 return 0;
}