ACE_CString str("Hello, world!"); ACE_CString sub_str = str.substr(7, 5);
ACE_CString str("I love C++ programming"); ACE_CString sub_str = str.substr(2, 7);In this example, the original string "I love C++ programming" is assigned to the variable `str`. Then, a substring starting at index 2 (which corresponds to the letter "l") and 7 characters long is assigned to the variable `sub_str`. Therefore, `sub_str` contains the string "love C++". In conclusion, ACE_CString substr is a function from the ACE library that is used to extract substrings from an ACE_CString object.