std::println(3)

NAME
std::println - std::println

Synopsis
   Defined in header <print>
   template< class... Args > (1) (since C++23)
   void println( std::format_string<Args...> fmt, Args&&... args );
   template< class... Args >
   void println( std::FILE* stream, (2) (since C++23)
                 std::format_string<Args...> fmt, Args&&... args );
   void println(); (3) (since C++26)
   void println( std::FILE* stream ); (4) (since C++26)
   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 std::print(stream, std::runtime_format(std::string(fmt.get()) +
   '\n'),
              std::forward<Args>(args)...).
   3) Equivalent to std::println(stdout).
   4) Equivalent to std::print(stream, "\n").
   The behavior is undefined if std::formatter<Ti, char> does not meet the
   BasicFormatter requirements for any Ti in Args (as required by
   std::make_format_args).

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 used in order.
             arg-id -
                        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 (since C++23)
                 thread id format specification and stacktrace entry
                 format specification.
               * For std::basic_stacktrace, no format specifier is
                 allowed.
               * For std::filesystem::path, see path format (since C++26)
                 specification.
               * 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
   Although overloads (3,4) are added in C++26, all known implementations make them
   available in C++23 mode.
   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
// Run this code
 #include <print>
 int main()
 {
     // Each call to std::println ends with new-line
     std::println("Please"); // overload (1)
     std::println("enter"); // (1)
     std::print("pass");
     std::print("word");
     std::println(); // (3); valid since C++26; same effect as std::print("\n");
 }

Output:
 Please
 enter
 password

See also
   print prints to stdout or a file stream using formatted
   (C++23) representation of the arguments
                        (function template)
   println(std::ostream) outputs formatted representation of the arguments with
   (C++23) appended '\n'
                        (function template)
   format stores formatted representation of the arguments in a new
   (C++20) string
                        (function template)
   printf
   fprintf prints formatted output to stdout, a file stream or a buffer
   sprintf (function)
   snprintf
   (C++11)