public member function

std::string::front

      char& front();const char& front() const;

Access first character

Returns a reference to the first character of the string.

Unlike member string::begin, which returns an iterator to this same character, this function returns a direct reference.

This function shall not be called on empty strings.

Parameters

none

Return value

A reference to the first character in the string.

If the string object is const-qualified, the function returns a

const char&. Otherwise, it returns a char&.

Example

// string::front
#include <iostream>
#include <string>

int main ()
{
  std::string str ("test string");
  str.front() = 'T';
  std::cout << str << '\n';
  return 0;
}

Output:

Complexity

Constant.

Iterator validity

No changes.

Data races

The container is accessed (neither the const nor the non-const versions modify the container).
The reference returned can be used to access or modify characters. Concurrently accessing or modifying different characters is safe.

Exception safety

If the string is not empty, the function never throws exceptions (no-throw guarantee).
Otherwise, it causes undefined behavior.