字符串连接[不用库函数]

#include "stdio.h"
#include "string.h"
char *str(char d[],char s[])
{
    char *p=d;;
    while(*p!='\0')p++;
    do
    {
        *p++=*s++;
    }while(*s!='\0');    
    *p=0;
    return d;
}
int main()
{
char d[20],s[20];
strcpy(d,"string ");
strcpy(s,"cat");
printf("%s\n",str(d,s));
}