std::vprint_unicode,std::vprint_unicode_locking(3)

NAME
std::vprint_unicode,std::vprint_unicode_locking - std::vprint_unicode,std::vprint_unicode_locking

Synopsis
   Defined in header <print>
   void vprint_unicode( std::string_view fmt, std::format_args args (1) (since C++23)
   );
   void vprint_unicode( std::FILE* stream,
                        std::string_view fmt, std::format_args args (2) (since C++23)
   );
   void vprint_unicode_locking( std::FILE* stream,
                        std::string_view fmt, (3) (since C++23)
   std::format_args args );
   Format args according to the format string fmt, and writes the result to the output
   stream.
   1) Equivalent to std::vprint_unicode(stdout, fmt, args).
   2) Equivalent to std::string out = std::vformat(fmt, args);
   std::vprint_unicode_locking(stream, "{}", std::make_format_args(out));.
   3) Performs the following operations in order:
    1. Locks stream.
    2. Let out denote the character representation of formatting arguments provided by
       args formatted according to specifications given in fmt.
    3. Writes out to stream:
     * If stream refers to a terminal capable of displaying Unicode, flushes stream and
       writes out to the terminal using the native Unicode API.
     * Otherwise, writes unmodified out to the stream.
   Unconditionally unlocks stream on function exit.
   If any of the following condition is satisfied, the behavior is undefined:
     * stream is not a valid pointer to an output C stream.
     * out contains invalid Unicode code units if the native Unicode API is used.

Parameters
   stream - output file stream to write to
            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
                        specifies the index of the argument in args whose value is to
                        be used for formatting; if it is omitted, the arguments are
            arg-id - 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.
   fmt - the format specification defined by the std::formatter
            format-spec - 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 (since C++23)
                id format specification and stacktrace entry format
                specification.
              * For std::basic_stacktrace, no format specifier is
                allowed.
              * 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

Exceptions
     * std::bad_alloc on allocation failure.
     * std::system_error, if writing to the stream fails.
     * Propagates any exception thrown by used formatters, e.g. std::format_error.

Notes
   The C++ standard encourages the implementers to produce a diagnostic message if out
   contains invalid Unicode code units.
   On POSIX, the stream refers to a terminal if the expression isatty(fileno(stream))
   != 0 holds true (see POSIX documentation for isatty, and fileno).
   On Windows, the stream refers to a terminal if the expression
   GetConsoleMode(_get_osfhandle(_fileno(stream))) returns nonzero (see Windows
   documentation for GetConsoleMode, _get_osfhandle, and _fileno). The native Unicode
   API on Windows is WriteConsoleW.
   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
                      202207L (C++23) Formatted output
   __cpp_lib_print 202403L (C++26) Formatted output with stream locking
                        (DR23)
   __cpp_lib_format 202207L (C++23) Exposing std::basic_format_string

Example
    This section is incomplete
    Reason: no example

See also
   vprint_nonunicode prints to stdout or a file stream using type-erased
   vprint_nonunicode_locking argument representation
   (C++23) (function)
   (C++23)
   vprint_unicode(std::ostream) performs Unicode aware output using type-erased
   (C++23) argument representation
                        (function)
   print prints to stdout or a file stream using formatted
   (C++23) representation of the arguments
                        (function template)
   format stores formatted representation of the arguments in a
   (C++20) new string
                        (function template)

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

Category:
     * Todo no example