C语言字符串截取

#include <stdio.h>
#include <string.h>
int main ()
{
   char str[] = "http://www.runoob.com";
   char ch = '.';
   char *ret = NULL;
   ret = strchr(str, 'r');
   if ( ret == NULL )
   {
        printf("aaaa/n");
   }
   else
   {
        if ( strlen(ret+1) == 0 )
        {
                printf("ccc/n");
        }
        printf("[%s]/n",ret+1);
   }
   printf("%d/n",strlen("${agent_id}:"));
   return(0);
}

strstr strchr