std::println

Defined in header <print>

template< class... Args >
void println( std::format_string<Args...> fmt, Args&&... args );

template< class... Args >
void println( std::format_string<Args...> fmt, Args&&... args );

since C++23

(1)

template< class... Args >
void println( std::FILE* stream,
            std::format_string<Args...> fmt, Args&&... args );

template< class... Args >
void println( std::FILE* stream,
            std::format_string<Args...> fmt, Args&&... args );

since C++23

(2)

void println();

void println();

since C++26

(3)

void println( std::FILE* stream );

void println( std::FILE* stream );

since C++26

(4)

Format args according to the format string fmt with appended \n (which means that each output ends with a new-line), and print the result to a stream.

1. Equivalent to std::println(stdout, fmt, std::forward<Args>(args)...)

2. Equivalent to performing the following operations:

   • std::print(stream, "{}\n", std::format(fmt, std::forward<Args>(args)...));

     (until C++26)
   • std::print(stream, std::runtime_format(std::string(fmt.get()) + '\n'), std::forward<Args>(args)...)

     (since C++26)

3. Equivalent to std::println(stdout).

4. Equivalent to std::print(stream, "\n").

If std::formatter<Ti, char> does not meet the BasicFormatter requirements for any Ti in Args (as required by std::make_format_args), the behavior is undefined.

Parameters

stream

output file stream to write to

fmt

• an object that represents the format string. The format string consists of
• ordinary characters (except { and }), which are copied unchanged to the output,
• escape sequences {{ and }}, which are replaced with { and } respectively in the output, and
• replacement fields.

Each replacement field has the following format:

|{ arg-id (optional) } |(1)| |{ arg-id (optional) : format-spec } |(2)|

1. replacement field without a format specification
2. replacement field with a format specification
   • arg-id - specifies the index of the argument in args whose value is to be used for formatting; if it is omitted, the arguments are used in order.