What is use of c_str function In c++

Question

I have just started reading C++ and found c++ having rich functions for string manipulation which C does not have. I am reading these function and came across c_str() and from what I understand is c_str convert a string which may be null terminated or may not be to a null terminated string .Is it true?

Can anyone suggest me some example so that i can understand the use of c_str function??

Answer 1

c_str returns a const char* that points to a null-terminated string (i.e. a C-style string). It is useful when you want to pass the "contents"¹ of an std::string to a function that expects to work with a C-style string.

For example, consider this code:

std::string string("Hello world!"); std::size_t pos1 = string.find_first_of('w');  std::size_t pos2 = static_cast<std::size_t>(std::strchr(string.c_str(), 'w') - string.c_str());  if (pos1 == pos2) {     std::printf("Both ways give the same result.\n"); } 

See it in action.

Notes:

¹ This is not entirely true because an std::string (unlike a C string) can contain the \0 character. If it does, the code that receives the return value of c_str() will be fooled into thinking that the string is shorter than it really is, since it will interpret \0 as the end of the string.