c字符串替換strstr strncpy

#include <stdio.h> 
#include <string.h>

int main () 
{ 
char str[] ="This is a simple string"; 
char * pch; 
pch = strstr (str,"simple"); 
puts(pch); 
strncpy (pch,"sample",6); 
puts(pch); 
puts (str); 
return 0; 
}

結果:This is a sample string