strstr() (search for a substring) function.

char * strstr(const char *s, const char *t)
{
   int i, j, k;
   for (i = 0; s[i] != '\0'; i++) 
   {
       for (j=i, k=0; t[k]!='\0' && s[j]==t[k]; j++, k++);
         if (k > 0 && t[k] == '\0')
            return (&s[i]);
   }
return NULL;
}