C++: String Functions without <cstring>

Question

I started learning strings and string functions (from a book) , I learned functions like strcpy and strcat and strncat..etc

So I started to practice using them in simple programs to get a sense of what they do.

Then I was surprised later that in the book it tells me that i have to use #include <cstring> in order to use all these string functions.

I have tried using string functions more than once without including <cstring> so why?

The only header file i included was <iostream> and yet i was able to use string functions.

Please someone explain to me why the string functions worked without <cstring> and do I need to include it to use string functions, and if no what are the uses of <cstring>;

Answer 1

First of all, you absolutely need to consider switching to std::string. Manual memory allocation, while being an interesting and sometimes challenging task, should not be a part of your everyday job.

Having said that, probably the <cstring> was #included by some other header you are using in your project. However it's better not to depend on the other headers including <cstring> (no one guarantees that they will do always and for every compiler), and include it where appropriate.

Answer 2

You don't need to include <cstring> because it is included by iostream.

However note that the function you are talking about (strcpy, strcat, strncat) are C function taking char * and have their C++ equivalents working with the more convenient std::string.

strcpy: std::string::operator=

std::string str2;
std::string str1 = str2; // copy str2 in str1

strcat: std::string::operator+=

str1 += str2; // concat str2 to str1

strncat:

str1 += str2.substr(0,n); // concat the first n characters of str2 to str1