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



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

NNAAMMEE
       fwprintf, swprintf, wprintf -- print formatted wide-character output

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

       int fwprintf(FILE *restrict _s_t_r_e_a_m, const wchar_t *restrict _f_o_r_m_a_t, ...);
       int swprintf(wchar_t *restrict _w_s, size_t _n,
           const wchar_t *restrict _f_o_r_m_a_t, ...);
       int wprintf(const wchar_t *restrict _f_o_r_m_a_t, ...);

DDEESSCCRRIIPPTTIIOONN
       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.1-2017
       defers to the ISO C standard.

       The _f_w_p_r_i_n_t_f() function shall place output on the named output _s_t_r_e_a_m.
       The _w_p_r_i_n_t_f() function shall place output on the standard output stream
       _s_t_d_o_u_t.  The _s_w_p_r_i_n_t_f() function shall place output followed by the
       null wide character in consecutive wide characters starting at *_w_s; 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 _f_o_r_m_a_t wide-character string. The _f_o_r_m_a_t is
       composed of zero or more directives: _o_r_d_i_n_a_r_y _w_i_d_e_-_c_h_a_r_a_c_t_e_r_s, which
       are simply copied to the output stream, and _c_o_n_v_e_r_s_i_o_n _s_p_e_c_i_f_i_c_a_t_i_o_n_s,
       each of which results in the fetching of zero or more arguments. The
       results are undefined if there are insufficient arguments for the
       _f_o_r_m_a_t.  If the _f_o_r_m_a_t is exhausted while arguments remain, the excess
       arguments are evaluated but are otherwise ignored.

       Conversions can be applied to the _nth argument after the _f_o_r_m_a_t 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 ""%%nn$$"", 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 _f_o_r_m_a_t wide-character
       strings that select arguments in an order appropriate to specific
       languages (see the EXAMPLES section).

       The _f_o_r_m_a_t 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 _f_o_r_m_a_t wide-character string
       are undefined. When numbered argument specifications are used,
       specifying the _Nth argument requires that all the leading arguments,
       from the first to the (_N-1)th, are specified in the _f_o_r_m_a_t wide-
       character string.

       In _f_o_r_m_a_t wide-character strings containing the "%_n$" form of
       conversion specification, numbered arguments in the argument list can
       be referenced from the _f_o_r_m_a_t wide-character string as many times as
       required.

       In _f_o_r_m_a_t wide-character strings containing the %% form of conversion
       specification, each argument in the argument list shall be used exactly
       once. It is unspecified whether an encoding error occurs if the format
       string contains wwcchhaarr__tt values that do not correspond to members of the
       character set of the current locale and the specified semantics do not
       require that value to be processed by _w_c_r_t_o_m_b().

       All forms of the _f_w_p_r_i_n_t_f() 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 _L_C___N_U_M_E_R_I_C).  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 _f_l_a_g_s (in any order), which modify the meaning of the
           conversion specification.

        *  An optional minimum _f_i_e_l_d _w_i_d_t_h.  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 _p_r_e_c_i_s_i_o_n that gives the minimum number of digits to
           appear for the dd, ii, oo, uu, xx, and XX conversion specifiers; the
           number of digits to appear after the radix character for the aa, AA,
           ee, EE, ff, and FF conversion specifiers; the maximum number of
           significant digits for the gg and GG conversion specifiers; or the
           maximum number of wide characters to be printed from a string in
           the ss conversion 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
           argument.

        *  A _c_o_n_v_e_r_s_i_o_n _s_p_e_c_i_f_i_e_r 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 iinntt 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 _f_o_r_m_a_t wide-character strings
       containing the "%_n$" form of a conversion specification, a field width
       or precision may be indicated by the sequence "*_m$", where _m is a
       decimal integer in the range [1,{NL_ARGMAX}] giving the position in the
       argument list (after the _f_o_r_m_a_t 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 (%%ii, %%dd, %%uu, %%ff, %%FF, %%gg, or %%GG) 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
               specified.

       <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 oo conversion, it shall increase the precision, if
               and only if necessary, to force the first digit of the result
               to be zero (if the value and precision are both 0, a single 0
               is printed). For xx or XX conversion specifiers, a non-zero
               result shall have 0x (or 0X) prefixed to it. For aa, AA, ee, EE, ff,
               FF, gg, and GG conversion specifiers, the result shall always
               contain a radix character, even if no digits follow it. Without
               this flag, a radix character appears in the result of these
               conversions only if a digit follows it. For gg and GG conversion
               specifiers, trailing zeros shall _n_o_t be removed from the result
               as they normally are. For other conversion specifiers, the
               behavior is undefined.

       0       For dd, ii, oo, uu, xx, XX, aa, AA, ee, EE, ff, FF, gg, and GG 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 ''00'' and ''--'' flags both appear, the ''00'' flag shall be
               ignored. For dd, ii, oo, uu, xx, and XX conversion specifiers, if a
               precision is specified, the ''00'' flag shall be ignored.  If the
               ''00'' and <apostrophe> flags both appear, the grouping wide
               characters are inserted before zero padding. For other
               conversions, the behavior is undefined.

       The length modifiers and their meanings are:

       hh      Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to a ssiiggnneedd cchhaarr or uunnssiiggnneedd cchhaarr argument
               (the argument will have been promoted according to the integer
               promotions, but its value shall be converted to ssiiggnneedd cchhaarr or
               uunnssiiggnneedd cchhaarr before printing); or that a following nn
               conversion specifier applies to a pointer to a ssiiggnneedd cchhaarr
               argument.

       h       Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to a sshhoorrtt or uunnssiiggnneedd sshhoorrtt argument (the
               argument will have been promoted according to the integer
               promotions, but its value shall be converted to sshhoorrtt or
               uunnssiiggnneedd sshhoorrtt before printing); or that a following nn
               conversion specifier applies to a pointer to a sshhoorrtt argument.

       l (ell) Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to a lloonngg or uunnssiiggnneedd lloonngg argument; that a
               following nn conversion specifier applies to a pointer to a lloonngg
               argument; that a following cc conversion specifier applies to a
               wwiinntt__tt argument; that a following ss conversion specifier
               applies to a pointer to a wwcchhaarr__tt argument; or has no effect on
               a following aa, AA, ee, EE, ff, FF, gg, or GG conversion specifier.

       ll (ell-ell)
               Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to a lloonngg lloonngg or uunnssiiggnneedd lloonngg lloonngg
               argument; or that a following nn conversion specifier applies to
               a pointer to a lloonngg lloonngg argument.

       j       Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to an iinnttmmaaxx__tt or uuiinnttmmaaxx__tt argument; or that
               a following nn conversion specifier applies to a pointer to an
               iinnttmmaaxx__tt argument.

       z       Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to a ssiizzee__tt or the corresponding signed
               integer type argument; or that a following nn conversion
               specifier applies to a pointer to a signed integer type
               corresponding to a ssiizzee__tt argument.

       t       Specifies that a following dd, ii, oo, uu, xx, or XX conversion
               specifier applies to a ppttrrddiiffff__tt or the corresponding uunnssiiggnneedd
               type argument; or that a following nn conversion specifier
               applies to a pointer to a ppttrrddiiffff__tt argument.

       L       Specifies that a following aa, AA, ee, EE, ff, FF, gg, or GG conversion
               specifier applies to a lloonngg ddoouubbllee 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 iinntt argument shall be converted to a signed decimal in the
               style "[-]_d_d_d_d_". 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
               converting zero with an explicit precision of zero shall be no
               wide characters.

       o       The uunnssiiggnneedd argument shall be converted to unsigned octal
               format in the style ""dddddddd"".  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 converting zero with an explicit precision of
               zero shall be no wide characters.

       u       The uunnssiiggnneedd argument shall be converted to unsigned decimal
               format in the style ""dddddddd"".  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 converting zero with an explicit precision of
               zero shall be no wide characters.

       x       The uunnssiiggnneedd argument shall be converted to unsigned
               hexadecimal format in the style ""dddddddd""; the letters ""aabbccddeeff""
               are used. 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 converting zero
               with an explicit precision of zero shall be no wide characters.

       X       Equivalent to the xx conversion specifier, except that letters
               ""AABBCCDDEEFF"" are used instead of ""aabbccddeeff"".

       f, F    The ddoouubbllee argument shall be converted to decimal notation in
               the style "[-]_d_d_d_._d_d_d_", 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 ddoouubbllee argument representing an infinity shall be converted
               in one of the styles ""[[--]]iinnff"" or ""[[--]]iinnffiinniittyy""; which style is
               implementation-defined. A ddoouubbllee argument representing a NaN
               shall be converted in one of the styles ""[[--]]nnaann"" or "[-]nan(_n_-
               _c_h_a_r_-_s_e_q_u_e_n_c_e)"; which style, and the meaning of any _n_-_c_h_a_r_-
               _s_e_q_u_e_n_c_e, is implementation-defined. The FF conversion specifier
               produces ""IINNFF"", ""IINNFFIINNIITTYY"", or ""NNAANN"" instead of ""iinnff"",
               ""iinnffiinniittyy"", or ""nnaann"", respectively.

       e, E    The ddoouubbllee argument shall be converted in the style
               "[-]_d_._d_d_de+-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
               character shall appear. The value shall be rounded in an
               implementation-defined manner to the appropriate number of
               digits. The EE conversion wide character shall produce a number
               with ''EE'' instead of ''ee'' introducing the exponent. The exponent
               shall always contain at least two digits. If the value is zero,
               the exponent shall be zero.

               A ddoouubbllee argument representing an infinity or NaN shall be
               converted in the style of an ff or FF conversion specifier.

       g, G    The ddoouubbllee argument representing a floating-point number shall
               be converted in the style ff or ee (or in the style FF or EE in the
               case of a GG conversion specifier), depending on the value
               converted and the precision.  Let PP 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 EE would have an exponent
               of _X:

               --  If PP>_X>=-4, the conversion shall be with style ff (or FF) and
                   precision PP-(_X+1).

               --  Otherwise, the conversion shall be with style ee (or EE) and
                   precision PP-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
               fractional portion remaining.

               A ddoouubbllee argument representing an infinity or NaN shall be
               converted in the style of an ff or FF conversion specifier.

       a, A    A ddoouubbllee argument representing a floating-point number shall be
               converted in the style "[-]0x_h._h_h_h_hp+-_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
               hexadecimal 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
               distinguish values of type ddoouubbllee, except that trailing zeros
               may be omitted; if the precision is zero and the ''##'' flag is
               not specified, no decimal-point wide character shall appear.
               The letters ""aabbccddeeff"" are used for aa conversion and the letters
               ""AABBCCDDEEFF"" for AA conversion. The AA conversion specifier produces
               a number with ''XX'' and ''PP'' instead of ''xx'' and ''pp''.  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 ddoouubbllee argument representing an infinity or NaN shall be
               converted in the style of an ff or FF conversion specifier.

       c       If no ll (ell) qualifier is present, the iinntt argument shall be
               converted to a wide character as if by calling the _b_t_o_w_c()
               function and the resulting wide character shall be written.
               Otherwise, the wwiinntt__tt argument shall be converted to wwcchhaarr__tt,
               and written.

       s       If no ll (ell) qualifier is present, the application shall
               ensure that the argument is a pointer to a character array
               containing a character sequence beginning in the initial shift
               state. Characters from the array shall be converted as if by
               repeated calls to the _m_b_r_t_o_w_c() function, with the conversion
               state described by an mmbbssttaattee__tt 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 ll (ell) qualifier is present, the application shall
               ensure that the argument is a pointer to an array of type
               wwcchhaarr__tt.  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
               vvooiidd.  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
               _f_w_p_r_i_n_t_f() 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
               undefined.

       C       Equivalent to llcc.

       S       Equivalent to llss.

       %       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.
       Characters generated by _f_w_p_r_i_n_t_f() and _w_p_r_i_n_t_f() shall be printed as if
       _f_p_u_t_w_c() had been called.

       For aa and AA 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 ee, EE, ff, FF, gg, and GG conversion specifiers, if the number of
       significant 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 representation 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 _f_w_p_r_i_n_t_f() or _w_p_r_i_n_t_f() and the next successful completion
       of a call to _f_f_l_u_s_h() or _f_c_l_o_s_e() on the same stream, or a call to
       _e_x_i_t() or _a_b_o_r_t().

RREETTUURRNN VVAALLUUEE
       Upon successful completion, these functions shall return the number of
       wide characters transmitted, excluding the terminating null wide
       character in the case of _s_w_p_r_i_n_t_f(), or a negative value if an output
       error was encountered, and set _e_r_r_n_o to indicate the error.

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

EERRRROORRSS
       For the conditions under which _f_w_p_r_i_n_t_f() and _w_p_r_i_n_t_f() fail and may
       fail, refer to _f_p_u_t_w_c().

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

       EEIILLSSEEQQ A wide-character code that does not correspond to a valid
              character has been detected.

       In addition, _f_w_p_r_i_n_t_f() and _w_p_r_i_n_t_f() may fail if:

       EENNOOMMEEMM Insufficient storage space is available.

       The _s_w_p_r_i_n_t_f() shall fail if:

       EEOOVVEERRFFLLOOWW
              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}.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       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, _f_o_r_m_a_t 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, _f_o_r_m_a_t could be a pointer to the wide-
       character string:


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

       producing the message:


           Sonntag, 3. Juli, 10:02

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       If an implementation detects that there are insufficient arguments for
       the format, it is recommended that the function should fail and report
       an [[EEIINNVVAALL]] error.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _S_e_c_t_i_o_n _2_._5, _S_t_a_n_d_a_r_d _I_/_O _S_t_r_e_a_m_s, _b_t_o_w_c(), _f_p_u_t_w_c(), _f_w_s_c_a_n_f(),
       _m_b_r_t_o_w_c(), _s_e_t_l_o_c_a_l_e()

       The Base Definitions volume of POSIX.1-2017, _C_h_a_p_t_e_r _7, _L_o_c_a_l_e,
       <<iinnttttyyppeess..hh>>, <<ssttddiioo..hh>>, <<wwcchhaarr..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                          FWPRINTF(3)
