Convert std::string to const char* in C++

This post will discuss how to convert a std::string to const char* in C++. The returned pointer should point to a char array containing the same sequence of characters as present in the string object and an additional null terminator (‘\0’ character) at the end.

1. Using `string::c_str` function

We can easily get a const char* from the std::string in constant time with the help of the string::c_str function. The returned pointer is backed by the internal array used by the string object, and if the string object is modified, the returned pointer will also be invalidated.

#include <iostream>

#include <string>

int main()

{

std::string str = "std::string to const char*";

const char *c = str.c_str();

std::cout << c;

return 0;

}

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Output:

std::string to const char*

2. Using `string::data` function

We can also call the string::data function on a std::string object to get const char*. This function works exactly like the string::c_str.

#include <iostream>

#include <string>

int main()

{

std::string str = "std::string to const char*";

char const *c = str.data();

std::cout << c;

return 0;

}

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Output:

std::string to const char*

3. Using contiguous storage of C++11

We know that C++11 guarantees std::string‘s memory allocation to be contiguous. So, we can get a pointer to the underlying char[] array behind std::string by invoking &str[0] or &*str.begin(). This approach will not work with C++98/03 standard.

#include <iostream>

#include <string>

int main()

{

std::string str = "std::string to const char*";

const char* c = &str[0];

std::cout << c;

return 0;

}

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Output:

std::string to const char*

That’s all about converting std::string to const char in C++.

Convert std::string to const char* in C++

1. Using string::c_str function

2. Using string::data function

3. Using contiguous storage of C++11

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1. Using `string::c_str` function

2. Using `string::data` function