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

PROLOG         top

       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         top

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

SYNOPSIS         top

       #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         top

       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 composed 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 languages (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, specifying 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
       conversion specification, numbered arguments in the argument list can
       be referenced 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
           number of digits to appear after the radix character for the a,
           A, e, E, f, and F conversion specifiers; the maximum number of
           significant digits for the g and G conversion specifiers; or the
           maximum number of wide characters to be printed from a string in
           the s 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 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 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
       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
               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 o conversion, it increases the precision (if
               necessary) 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 character 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 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 d, i, o, u, x, or X conversion
               specifier applies to a signed char or unsigned char argument
               (the argument will have been promoted according to the
               integer promotions, but its value shall be converted to
               signed char or unsigned char before printing); or that a
               following n conversion specifier applies to a pointer to a
               signed char argument.

       h       Specifies that a following d, i, o, u, x, or X conversion
               specifier applies to a short or unsigned short argument (the
               argument will have been promoted according to the integer
               promotions, but its value shall be converted to short or
               unsigned short before printing); or that a following n
               conversion specifier applies to a pointer to a short
               argument.

       l (ell) Specifies that a following d, i, o, u, x, or X conversion
               specifier applies to a long or unsigned long argument; that a
               following 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
               specifier 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
               specifier 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
               specifier 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
               specifier 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 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 unsigned argument shall be converted to unsigned octal
               format 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 converting 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
               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 unsigned argument shall be converted to unsigned
               hexadecimal 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 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 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", "infinity", 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 character shall appear. The value shall be rounded in
               an implementation-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
               converted 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 converted 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 fractional portion remaining.

               A double argument representing an infinity or NaN shall be
               converted 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.hhhhd", 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 double,
               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 "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
               converted 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
               containing 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 undefined.

       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.
       Characters 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
       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 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         top

       Upon successful completion, these functions shall return the number
       of wide characters transmitted, excluding the terminating null wide
       character 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         top

       For the conditions under which fwprintf() and wprintf() fail and may
       fail, refer to fputwc(3p).

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

       EILSEQ A wide-character code that does not correspond to a valid
              character 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         top

       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-
       character string:

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

       producing the message:

           Sonntag, 3. Juli, 10:02

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Section 2.5, Standard I/O Streams, btowc(3p), fputwc(3p),
       fwscanf(3p), mbrtowc(3p), setlocale(3p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 7, Locale,
       stdio.h(0p), wchar.h(0p)

COPYRIGHT         top

       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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                        FWPRINTF(3P)

Pages that refer to this page: wchar.h(0p)fwscanf(3p)swprintf(3p)vfwprintf(3p)wprintf(3p)