从原字符串的第m个开始的全部字符复制成为另一个字符串

#include<stdio.h>#include<string.h>int main (){void copystr(char *,char *,int);int m;char str1[20],str2[20];printf("input string:");gets(str1);printf("which character that begin to copy?");scanf("%d",&m);if(strlen(str1) < m){printf("input error!");}else{copystr(str1,str2,m);printf("result:%s\n",str2);}return 0;}void copystr(char *p1,char *p2,int m){int n;n = 0;while(n < m - 1){n++;p1++;}while(*p1 != '\0'){*p2 = *p1;p1++;p2++;}*p2 = '\0';}