std:: vprint_unicode (std::ostream)

Defined in header <ostream>
void vprint_unicode ( std:: ostream & os, std:: string_view fmt, std:: format_args args ) ;		(since C++23)

Behaves as FormattedOutputFunction (except that some details of error reporting differ ):

• First, the function constructs and checks the sentry object.
• Then, initializes an automatic variable as if by std:: string out = std:: vformat ( os. getloc ( ) , fmt, args ) ; .
• Finally, inserts the character sequence [out.begin(), out.end()) into os , that is, if os refers to a terminal capable of displaying Unicode, writes out to this terminal using the native Unicode API. Otherwise, writes unmodified out to the os .

Parameters

os	-	output stream to insert data into
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. The arg-id s in a format string must all be present or all be omitted. Mixing manual and automatic indexing is an error. format-spec - the format specification defined by the std::formatter specialization for the corresponding argument. Cannot start with } . For basic types and standard string types, the format specification is interpreted as standard format specification . For chrono types, the format specification is interpreted as chrono format specification . For range types, the format specification is interpreted as range format specification . For std::pair and std::tuple , the format specification is interpreted as tuple format specification . For std::thread::id and std::stacktrace_entry , see thread id format specification and stacktrace entry format specification . For std::basic_stacktrace , no format specifier is allowed. (since C++23) For std::filesystem::path , see path format specification . (since C++26) For other formattable types, the format specification is determined by user-defined formatter specializations.
args	-	arguments to be formatted

Return value

(none)

Exceptions

• std::bad_alloc on allocation failure.
• Propagate any exception thrown by any formatter , e.g. std::format_error , without regard to the value of os. exceptions ( ) and without turning on ios_base::badbit in the error state of os .
• May throw ios_base::failure caused by os. setstate ( ios_base :: badbit ) which is called if an insertion into os fails.

Notes

If invoking the native Unicode API requires transcoding, the invalid code units are substituted with U+FFFD REPLACEMENT CHARACTER (see "The Unicode Standard Version 14.0 - Core Specification", Chapter 3.9 ).

Feature-test macro	Value	Std	Feature
__cpp_lib_print	202207L	(C++23)	Formatted output
__cpp_lib_format	202207L	(C++23)	Exposing std::basic_format_string

Example

This section is incomplete Reason: no example

See also

vprint_nonunicode (std::ostream) (C++23)	outputs character data using type-erased argument representation (function)
print (std::ostream) (C++23)	outputs formatted representation of the arguments (function template)
operator<< (std::basic_ostream)	inserts character data or insert into rvalue stream (function template)
vprint_unicode vprint_unicode_buffered (C++23)	prints to Unicode capable stdout or a file stream using type-erased argument representation (function)
format (C++20)	stores formatted representation of the arguments in a new string (function template)

External links

1.	Unicode
2.	The Unicode Standard Version 14.0 - Core Specification