Getting problem while executing strlen() in C++

[saiavinashiitr]

when i am executing cout<<strlen("a vinash"); in the main function, i am getting output as 7....but whereas if i execute as following

#include <iostream>
#include <cstring>
using namespace std;
int main()
{
string a = "avinash";
cout<<strlen(a) ;
}

Now, i am getting an error that cannot covert std::string ot const chat* for argument 1 to size_t strlen(const char*)

but if do using string length, i am getting the perfect answer

#include <iostream>
#include <string>
#include <cstring>
using namespace std;
int main()
{
string a = "avinash";
cout<<a.length( );
}

Now i am getting the correct output as 7

can u please tell me why i am unable to get the same output using cout<<strlen(a) ;

[weaknessforcats]

You cannot use strlen on a C++ string object. strlen assumes a null-terminated char array. A sring object my not have that structure.

You are supposed to use the size() method of string.

You can, however, tell the string object to produce a C-style null terminated string by using the c_str() method:

 cout<<strlen(a.c_str());