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

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

#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

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

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