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FWPRINTF(3P)		   POSIX Programmer's Manual		  FWPRINTF(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       fwprintf, swprintf, wprintf — print formatted wide-character output

SYNOPSIS
       #include <stdio.h>
       #include <wchar.h>

       int fwprintf(FILE *restrict stream, const wchar_t *restrict format, ...);
       int swprintf(wchar_t *restrict ws, size_t n,
	   const wchar_t *restrict format, ...);
       int wprintf(const wchar_t *restrict format, ...);

DESCRIPTION
       The functionality described on this reference page is aligned with  the
       ISO C  standard.	 Any  conflict between the requirements described here
       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
       defers to the ISO C standard.

       The  fwprintf() function shall place output on the named output stream.
       The wprintf() function shall place output on the standard output stream
       stdout.	 The  swprintf()  function  shall place output followed by the
       null wide character in consecutive wide characters starting at *ws;  no
       more  than  n wide characters shall be written, including a terminating
       null wide character, which is always added (unless n is zero).

       Each of these functions shall convert, format, and print its  arguments
       under  control  of the format wide-character string. The format is com‐
       posed of zero or more directives: ordinary wide-characters,  which  are
       simply copied to the output stream, and conversion specifications, each
       of which results in the fetching of zero or more arguments. The results
       are  undefined  if there are insufficient arguments for the format.  If
       the format is exhausted while arguments remain,	the  excess  arguments
       are evaluated but are otherwise ignored.

       Conversions  can be applied to the nth argument after the format in the
       argument list, rather than to the next unused argument. In  this	 case,
       the  conversion	specifier  wide character % (see below) is replaced by
       the sequence  "%n$",  where  n  is  a  decimal  integer	in  the	 range
       [1,{NL_ARGMAX}],	 giving	 the  position of the argument in the argument
       list. This feature provides for the definition of format wide-character
       strings	that select arguments in an order appropriate to specific lan‐
       guages (see the EXAMPLES section).

       The format can contain either numbered  argument	 specifications	 (that
       is,  "%n$" and "*m$"), or unnumbered argument conversion specifications
       (that is, % and *), but not both. The only exception to this is that %%
       can  be	mixed  with the "%n$" form. The results of mixing numbered and
       unnumbered argument specifications in a	format	wide-character	string
       are undefined. When numbered argument specifications are used, specify‐
       ing the Nth argument requires that all the leading arguments, from  the
       first  to  the  (N−1)th,	 are  specified	 in  the format wide-character
       string.

       In format wide-character strings containing the "%n$" form  of  conver‐
       sion specification, numbered arguments in the argument list can be ref‐
       erenced	from  the  format  wide-character  string  as  many  times  as
       required.

       In  format  wide-character  strings containing the % form of conversion
       specification, each argument in the argument list shall be used exactly
       once.

       All  forms  of  the  fwprintf()	function  allow for the insertion of a
       locale-dependent radix character in the	output	string,	 output	 as  a
       wide-character  value.  The  radix  character is defined in the current
       locale (category LC_NUMERIC).  In the POSIX  locale,  or	 in  a	locale
       where  the  radix  character  is not defined, the radix character shall
       default to a <period> ('.').

       Each conversion specification is introduced by the '%'  wide  character
       or  by  the  wide-character  sequence  "%n$", after which the following
       appear in sequence:

	*  Zero or more flags (in any order), which modify the meaning of  the
	   conversion specification.

	*  An  optional minimum field width.  If the converted value has fewer
	   wide characters than the field  width,  it  shall  be  padded  with
	   <space>  characters	by  default on the left; it shall be padded on
	   the right, if the left-adjustment flag ('−'), described  below,  is
	   given  to  the  field  width.  The field width takes the form of an
	   <asterisk> ('*'), described below, or a decimal integer.

	*  An optional precision that gives the minimum number	of  digits  to
	   appear for the d, i, o, u, x, and X conversion specifiers; the num‐
	   ber of digits to appear after the radix character for the a, A,  e,
	   E,  f,  and F conversion specifiers; the maximum number of signifi‐
	   cant digits for the g and G conversion specifiers; or  the  maximum
	   number of wide characters to be printed from a string in the s con‐
	   version specifiers. The precision takes  the	 form  of  a  <period>
	   ('.')   followed either by an <asterisk> ('*'), described below, or
	   an optional decimal digit string, where  a  null  digit  string  is
	   treated as 0. If a precision appears with any other conversion wide
	   character, the behavior is undefined.

	*  An optional length modifier that specifies the size	of  the	 argu‐
	   ment.

	*  A  conversion  specifier  wide character that indicates the type of
	   conversion to be applied.

       A field width, or precision, or both, may be indicated by an <asterisk>
       ('*').	In  this case an argument of type int supplies the field width
       or precision. Applications shall ensure that arguments specifying field
       width,  or precision, or both appear in that order before the argument,
       if any, to be converted. A negative field width is taken as a '−'  flag
       followed by a positive field width. A negative precision is taken as if
       the precision were omitted.  In format wide-character strings  contain‐
       ing the "%n$" form of a conversion specification, a field width or pre‐
       cision may be indicated by the sequence "*m$", where  m	is  a  decimal
       integer	in  the range [1,{NL_ARGMAX}] giving the position in the argu‐
       ment list (after the format argument) of an integer argument containing
       the field width or precision, for example:

	   wprintf(L"%1$d:%2$.*3$d:%4$.*3$d\n", hour, min, precision, sec);

       The flag wide characters and their meanings are:

       '       (The  <apostrophe>.)   The  integer  portion of the result of a
	       decimal conversion (%i, %d, %u, %f, %F, %g,  or	%G)  shall  be
	       formatted  with	thousands' grouping wide characters. For other
	       conversions, the behavior is undefined.	The  numeric  grouping
	       wide character is used.

       −       The result of the conversion shall be left-justified within the
	       field.  The conversion shall be right-justified if this flag is
	       not specified.

       +       The  result  of	a  signed conversion shall always begin with a
	       sign ('+' or '−').  The conversion shall begin with a sign only
	       when  a	negative value is converted if this flag is not speci‐
	       fied.

       <space> If the first wide character of a signed	conversion  is	not  a
	       sign,  or if a signed conversion results in no wide characters,
	       a <space> shall be prefixed to the result. This means  that  if
	       the  <space>  and '+' flags both appear, the <space> flag shall
	       be ignored.

       #       Specifies that the value is to be converted to  an  alternative
	       form.   For o conversion, it increases the precision (if neces‐
	       sary) to force the first digit of the result to be 0. For x  or
	       X  conversion  specifiers,  a non-zero result shall have 0x (or
	       0X) prefixed to it. For a, A, e, E, f, F, g, and	 G  conversion
	       specifiers,  the result shall always contain a radix character,
	       even if no digits follow it. Without this flag, a radix charac‐
	       ter  appears in the result of these conversions only if a digit
	       follows it. For g and G conversion specifiers,  trailing	 zeros
	       shall  not be removed from the result as they normally are. For
	       other conversion specifiers, the behavior is undefined.

       0       For d, i, o, u, x, X, a, A, e, E, f, F,	g,  and	 G  conversion
	       specifiers,  leading zeros (following any indication of sign or
	       base) are used to pad to the field width rather than performing
	       space  padding,	except	when converting an infinity or NaN. If
	       the '0' and '−' flags  both  appear,  the  '0'  flag  shall  be
	       ignored.	 For  d, i, o, u, x, and X conversion specifiers, if a
	       precision is specified, the '0' flag shall be ignored.  If  the
	       '0' and <apostrophe> flags both appear, the grouping wide char‐
	       acters are inserted before zero padding. For other conversions,
	       the behavior is undefined.

       The length modifiers and their meanings are:

       hh      Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier applies to a signed char or unsigned char	argument  (the
	       argument	 will have been promoted according to the integer pro‐
	       motions, but its value shall be converted  to  signed  char  or
	       unsigned	 char  before printing); or that a following n conver‐
	       sion specifier applies to a pointer to a signed char argument.

       h       Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier  applies to a short or unsigned short argument (the argu‐
	       ment will have been promoted according to  the  integer	promo‐
	       tions,  but  its	 value shall be converted to short or unsigned
	       short before printing); or that a following n conversion speci‐
	       fier applies to a pointer to a short argument.

       l (ell) Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier applies to a long or unsigned long argument; that a  fol‐
	       lowing  n  conversion  specifier applies to a pointer to a long
	       argument; that a following c conversion specifier applies to  a
	       wint_t  argument;  that	a  following  s	 conversion  specifier
	       applies to a pointer to a wchar_t argument; or has no effect on
	       a following a, A, e, E, f, F, g, or G conversion specifier.

       ll (ell-ell)
	       Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier applies to a long long or unsigned long long argument; or
	       that a following n conversion specifier applies to a pointer to
	       a long long argument.

       j       Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier  applies  to an intmax_t or uintmax_t argument; or that a
	       following n conversion specifier applies to  a  pointer	to  an
	       intmax_t argument.

       z       Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier applies to a size_t or the corresponding  signed  integer
	       type  argument;	or  that  a  following	n conversion specifier
	       applies to a pointer to a signed integer type corresponding  to
	       a size_t argument.

       t       Specifies that a following d, i, o, u, x, or X conversion spec‐
	       ifier applies to a ptrdiff_t or the corresponding unsigned type
	       argument; or that a following n conversion specifier applies to
	       a pointer to a ptrdiff_t argument.

       L       Specifies that a following a, A, e, E, f, F, g, or G conversion
	       specifier applies to a long double argument.

       If  a  length modifier appears with any conversion specifier other than
       as specified above, the behavior is undefined.

       The conversion specifiers and their meanings are:

       d, i    The int argument shall be converted to a signed decimal in  the
	       style  "[−]dddd". The precision specifies the minimum number of
	       digits to appear; if the value being converted  can  be	repre‐
	       sented  in  fewer  digits,  it  shall  be expanded with leading
	       zeros. The default precision shall be 1. The result of convert‐
	       ing  zero  with	an explicit precision of zero shall be no wide
	       characters.

       o       The unsigned argument shall be converted to unsigned octal for‐
	       mat  in	the style "dddd".  The precision specifies the minimum
	       number of digits to appear; if the value being converted can be
	       represented  in fewer digits, it shall be expanded with leading
	       zeros. The default precision shall be 1. The result of convert‐
	       ing  zero  with	an explicit precision of zero shall be no wide
	       characters.

       u       The unsigned argument shall be converted	 to  unsigned  decimal
	       format  in the style "dddd".  The precision specifies the mini‐
	       mum number of digits to appear; if the  value  being  converted
	       can  be	represented in fewer digits, it shall be expanded with
	       leading zeros. The default precision shall be 1. The result  of
	       converting  zero with an explicit precision of zero shall be no
	       wide characters.

       x       The unsigned argument shall be converted to unsigned  hexadeci‐
	       mal  format in the style "dddd"; the letters "abcdef" are used.
	       The precision specifies the minimum number of digits to appear;
	       if  the	value being converted can be represented in fewer dig‐
	       its, it shall be expanded with leading zeros. The default  pre‐
	       cision  shall  be  1.  The  result  of  converting zero with an
	       explicit precision of zero shall be no wide characters.

       X       Equivalent to the x conversion specifier, except	 that  letters
	       "ABCDEF" are used instead of "abcdef".

       f, F    The  double  argument shall be converted to decimal notation in
	       the style "[−]ddd.ddd", where the number of  digits  after  the
	       radix  character shall be equal to the precision specification.
	       If the precision is missing, it shall be taken  as  6;  if  the
	       precision  is  explicitly  zero	and no '#' flag is present, no
	       radix character shall appear. If a radix character appears,  at
	       least  one  digit  shall	 appear	 before it. The value shall be
	       rounded in an implementation-defined manner to the  appropriate
	       number of digits.

	       A  double  argument representing an infinity shall be converted
	       in one of the styles "[−]inf" or "[−]infinity"; which style  is
	       implementation-defined.	A  double  argument representing a NaN
	       shall be converted in one of the styles "[−]nan" or  "[−]nan(n-
	       char-sequence)";	 which	style,	and the meaning of any n-char-
	       sequence, is implementation-defined. The F conversion specifier
	       produces	 "INF", "INFINITY", or "NAN" instead of "inf", "infin‐
	       ity", or "nan", respectively.

       e, E    The  double  argument  shall  be	  converted   in   the	 style
	       "[−]d.ddde±dd", where there shall be one digit before the radix
	       character (which is non-zero if the argument is	non-zero)  and
	       the  number of digits after it shall be equal to the precision;
	       if the precision is missing, it shall be taken  as  6;  if  the
	       precision  is zero and no '#' flag is present, no radix charac‐
	       ter shall appear. The value shall be rounded in an  implementa‐
	       tion-defined  manner to the appropriate number of digits. The E
	       conversion wide character  shall	 produce  a  number  with  'E'
	       instead	of  'e'	 introducing  the exponent. The exponent shall
	       always contain at least two digits. If the value is  zero,  the
	       exponent shall be zero.

	       A double argument representing an infinity or NaN shall be con‐
	       verted in the style of an f or F conversion specifier.

       g, G    The double argument representing a floating-point number	 shall
	       be converted in the style f or e (or in the style F or E in the
	       case of a G conversion specifier), depending on the value  con‐
	       verted  and  the	 precision.  Let P equal the precision if non-
	       zero, 6 if the precision is omitted, or 1 if the	 precision  is
	       zero. Then, if a conversion with style E would have an exponent
	       of X:

	       --  If P>X≥−4, the conversion shall be with style f (or F)  and
		   precision P−(X+1).

	       --  Otherwise,  the conversion shall be with style e (or E) and
		   precision P−1.

	       Finally, unless the '#' flag is used, any trailing zeros	 shall
	       be  removed  from  the fractional portion of the result and the
	       decimal-point character shall be removed if there is  no	 frac‐
	       tional portion remaining.

	       A double argument representing an infinity or NaN shall be con‐
	       verted in the style of an f or F conversion specifier.

       a, A    A double argument representing a floating-point number shall be
	       converted  in  the style "[−]0xh.hhhhp±d", where there shall be
	       one hexadecimal digit (which is non-zero if the argument	 is  a
	       normalized  floating-point number and is otherwise unspecified)
	       before the decimal-point wide character and the number of hexa‐
	       decimal digits after it shall be equal to the precision; if the
	       precision is missing and FLT_RADIX is a power of	 2,  then  the
	       precision  shall	 be  sufficient for an exact representation of
	       the value; if the precision is missing and FLT_RADIX is	not  a
	       power  of  2, then the precision shall be sufficient to distin‐
	       guish values of type double, except that trailing zeros may  be
	       omitted; if the precision is zero and the '#' flag is not spec‐
	       ified, no decimal-point wide character shall appear.  The  let‐
	       ters  "abcdef"  are  used  for  a  conversion  and  the letters
	       "ABCDEF" for A conversion. The A conversion specifier  produces
	       a number with 'X' and 'P' instead of 'x' and 'p'.  The exponent
	       shall always contain at least one digit, and only as many  more
	       digits  as necessary to represent the decimal exponent of 2. If
	       the value is zero, the exponent shall be zero.

	       A double argument representing an infinity or NaN shall be con‐
	       verted in the style of an f or F conversion specifier.

       c       If  no  l (ell) qualifier is present, the int argument shall be
	       converted to a wide character as	 if  by	 calling  the  btowc()
	       function	 and  the  resulting  wide character shall be written.
	       Otherwise, the wint_t argument shall be converted  to  wchar_t,
	       and written.

       s       If  no  l  (ell)	 qualifier  is	present, the application shall
	       ensure that the argument is a pointer to a character array con‐
	       taining	a  character  sequence	beginning in the initial shift
	       state. Characters from the array shall be converted  as	if  by
	       repeated	 calls	to the mbrtowc() function, with the conversion
	       state described by an  mbstate_t	 object	 initialized  to  zero
	       before the first character is converted, and written up to (but
	       not including) the terminating null  wide  character.   If  the
	       precision  is specified, no more than that many wide characters
	       shall be written. If the precision  is  not  specified,	or  is
	       greater	than  the  size	 of  the  array, the application shall
	       ensure that the array contains a null wide character.

	       If an l (ell)  qualifier	 is  present,  the  application	 shall
	       ensure  that  the  argument  is	a  pointer to an array of type
	       wchar_t.	 Wide characters from the array shall be written up to
	       (but  not  including)  a terminating null wide character. If no
	       precision is specified, or is greater  than  the	 size  of  the
	       array,  the  application shall ensure that the array contains a
	       null wide character. If a precision is specified, no more  than
	       that many wide characters shall be written.

       p       The  application shall ensure that the argument is a pointer to
	       void.  The value	 of  the  pointer  shall  be  converted	 to  a
	       sequence	 of  printable	wide  characters in an implementation-
	       defined manner.

       n       The application shall ensure that the argument is a pointer  to
	       an  integer into which is written the number of wide characters
	       written to the output so	 far  by  this	call  to  one  of  the
	       fwprintf()  functions.  No argument shall be converted, but one
	       shall be consumed.  If the  conversion  specification  includes
	       any flags, a field width, or a precision, the behavior is unde‐
	       fined.

       C       Equivalent to lc.

       S       Equivalent to ls.

       %       Output a '%' wide character; no argument	 shall	be  converted.
	       The entire conversion specification shall be %%.

       If  a  conversion  specification does not match one of the above forms,
       the behavior is undefined.

       In no case does a nonexistent or small field width cause truncation  of
       a  field;  if the result of a conversion is wider than the field width,
       the field shall be expanded to contain the conversion result.   Charac‐
       ters  generated	by  fwprintf()	and  wprintf()	shall be printed as if
       fputwc() had been called.

       For a and A conversions, if FLT_RADIX is not  a	power  of  2  and  the
       result  is not exactly representable in the given precision, the result
       should be one of the two adjacent numbers in hexadecimal floating style
       with  the  given	 precision,  with the extra stipulation that the error
       should have a correct sign for the current rounding direction.

       For e, E, f, F, g, and G conversion specifiers, if the number  of  sig‐
       nificant	 decimal digits is at most DECIMAL_DIG, then the result should
       be correctly rounded. If the number of significant  decimal  digits  is
       more  than  DECIMAL_DIG	but  the source value is exactly representable
       with DECIMAL_DIG digits, then the result should be an exact representa‐
       tion  with  trailing  zeros.  Otherwise, the source value is bounded by
       two adjacent decimal strings L < U, both having DECIMAL_DIG significant
       digits; the value of the resultant decimal string D should satisfy L <=
       D <= U, with the extra stipulation that the error should have a correct
       sign for the current rounding direction.

       The  last  data	modification and last file status change timestamps of
       the file shall be marked for update between the call  to	 a  successful
       execution of fwprintf() or wprintf() and the next successful completion
       of a call to fflush() or fclose() on the same  stream,  or  a  call  to
       exit() or abort().

RETURN VALUE
       Upon  successful completion, these functions shall return the number of
       wide characters transmitted, excluding the terminating null wide	 char‐
       acter in the case of swprintf(), or a negative value if an output error
       was encountered, and set errno to indicate the error.

       If n or more wide characters were requested to be  written,  swprintf()
       shall return a negative value, and set errno to indicate the error.

ERRORS
       For  the	 conditions  under which fwprintf() and wprintf() fail and may
       fail, refer to fputwc().

       In addition, all forms of fwprintf() shall fail if:

       EILSEQ A wide-character code that does not correspond to a valid	 char‐
	      acter has been detected.

       In addition, all forms of fwprintf() may fail if:

       EINVAL There are insufficient arguments.

       In addition, fwprintf() and wprintf() may fail if:

       ENOMEM Insufficient storage space is available.

       The swprintf() shall fail if:

       EOVERFLOW
	      The  value of n is greater than {INT_MAX} or the number of bytes
	      needed to hold the output	 excluding  the	 terminating  null  is
	      greater than {INT_MAX}.

       The following sections are informative.

EXAMPLES
       To  print  the language-independent date and time format, the following
       statement could be used:

	   wprintf(format, weekday, month, day, hour, min);

       For American usage, format could be a  pointer  to  the	wide-character
       string:

	   L"%s, %s %d, %d:%.2d\n"

       producing the message:

	   Sunday, July 3, 10:02

       whereas for German usage, format could be a pointer to the wide-charac‐
       ter string:

	   L"%1$s, %3$d. %2$s, %4$d:%5$.2d\n"

       producing the message:

	   Sonntag, 3. Juli, 10:02

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.5, Standard I/O Streams, btowc(), fputwc(),  fwscanf(),  mbr‐
       towc(), setlocale()

       The  Base  Definitions  volume  of  POSIX.1‐2008,  Chapter  7,  Locale,
       <stdio.h>, <wchar.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
       cal and Electronics Engineers,  Inc  and	 The  Open  Group.   (This  is
       POSIX.1-2008  with  the	2013  Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained	online
       at http://www.unix.org/online.html .

       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker‐
       nel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2013			  FWPRINTF(3P)
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