# std::basic_string<CharT,Traits,Allocator>::starts_with

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< cpp‎ | string‎ | basic string

constexpr bool starts_with( std::basic_string_view<CharT,Traits> sv ) const noexcept; | (1) | (since C++20)
constexpr bool starts_with( CharT ch ) const noexcept; | (2) | (since C++20)
constexpr bool starts_with( const CharT* s ) const; | (3) | (since C++20)

Checks if the string begins with the given prefix. The prefix may be one of the following:

1) A string view `sv` (which may be a result of implicit conversion from another `std::basic_string`).
2) A single character ch.
3) A null-terminated character string s.

All three overloads effectively return std::basic_string_view<CharT, Traits>(data(), size()).starts_with(x), where `x` is the parameter.

### Parameters

sv | - | a string view which may be a result of implicit conversion from another `std::basic_string`
ch | - | a single character
s | - | a null-terminated character string

### Return value

true if the string begins with the provided prefix, false otherwise.

### Notes

Feature-test macro | Value | Std | Comment
--- | --- | --- | ---
`__cpp_lib_starts_ends_with` | 201711L | (C++20) | String prefix and suffix checking: starts_with() and ends_with()

### Example

Run this code

    #include <iostream>
    #include <string>
    #include <string_view>

    template<typename PrefixType>
    void test_prefix_print(const std::string& str, PrefixType prefix)
    {
        std::cout << '\'' << str << "' starts with '" << prefix << "': "
                  << str.starts_with(prefix) << '\n';
    }

    int main()
    {
        std::boolalpha(std::cout);
        auto helloWorld = std::string("hello world");

        test_prefix_print(helloWorld, std::string_view("hello"));

        test_prefix_print(helloWorld, std::string_view("goodbye"));

        test_prefix_print(helloWorld, 'h');

        test_prefix_print(helloWorld, 'x');
    }

Output:

    'hello world' starts with 'hello': true
    'hello world' starts with 'goodbye': false
    'hello world' starts with 'h': true
    'hello world' starts with 'x': false

### See also

ends_with (C++20) | checks if the string ends with the given suffix (public member function)
starts_with (C++20) | checks if the string view starts with the given prefix (public member function of `std::basic_string_view<CharT,Traits>`)
ends_with (C++20) | checks if the string view ends with the given suffix (public member function of `std::basic_string_view<CharT,Traits>`)
contains (C++23) | checks if the string contains the given substring or character (public member function)
contains (C++23) | checks if the string view contains the given substring or character (public member function of `std::basic_string_view<CharT,Traits>`)
compare | compares two strings (public member function)
substr | returns a substring (public member function)

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