< cpp‎ | io‎ | basic 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.


[edit] 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 }.

(since C++23)
(since C++26)
  • For other formattable types, the format specification is determined by user-defined formatter specializations.
args - arguments to be formatted

[edit] Return value


[edit] Exceptions

[edit] 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

[edit] Example

[edit] See also

outputs character data using type-erased argument representation
(function) [edit]
outputs formatted representation of the arguments
(function template) [edit]
inserts character data or insert into rvalue stream
(function template) [edit]
prints to Unicode capable stdout or a file stream using type-erased argument representation
(function) [edit]
stores formatted representation of the arguments in a new string
(function template) [edit]

[edit] External links

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