FWPRINTF(3P) POSIX Programmer's Manual FWPRINTF(3P)
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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 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$" form of conver-
sion specification, numbered arguments in the argument list can be ref-
erenced from the format wide-character string as many times as
required.
In format wide-character strings containing the % form of conversion
specification, each argument in the argument list shall be used exactly
once.
All forms of the fwprintf() function allow for the insertion of a
locale-dependent radix character in the output string, output as a
wide-character value. The radix character is defined in the program's
locale (category LC_NUMERIC ). In the POSIX locale, or in a locale
where the radix character is not defined, the radix character shall
default to a period ( '.' ).
Each conversion specification is introduced by the '%' wide character
or by the wide-character sequence "%n$", 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 spaces
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 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 ( '.' ) fol-
lowed 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 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 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 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 speci-
fiers, 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 fol-
lows 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; no space padding is
performed. If the '0' and '-' flags both appear, the '0' flag
shall be ignored. For d, i, o, u, x, and X conversion speci-
fiers, if a precision is specified, the '0' flag shall be
ignored. If the '0' and '" flags both appear, the grouping wide
characters are inserted before zero padding. For other conver-
sions, the behavior is undefined.
The length modifiers and their meanings are:
hh Specifies that a following d, i, o, u, x, or X conversion speci-
fier applies to a signed char or unsigned char argument (the
argument will have been promoted according to the integer promo-
tions, 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 speci-
fier 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 speci-
fier applies to a long or unsigned long argument; that a follow-
ing n conversion specifier applies to a pointer to a long argu-
ment; 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 fol-
lowing 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 speci-
fier 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 speci-
fier applies to an intmax_t or uintmax_t argument; or that a
following n conversion specifier applies to a pointer to an int-
max_t argument.
z Specifies that a following d, i, o, u, x, or X conversion speci-
fier 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 speci-
fier 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 converting 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 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.
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 pre-
cision 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 pre-
cision 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 pre-
cision 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 con-
version wide character shall produce a number with 'E' instead
of 'e' introducing the exponent. The exponent shall always con-
tain 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 shall be converted in the style f or e (or
in the style F or E in the case of a G conversion specifier),
with the precision specifying the number of significant digits.
If an explicit precision is zero, it shall be taken as 1. The
style used depends on the value converted; style e (or E ) shall
be used only if the exponent resulting from such a conversion is
less than -4 or greater than or equal to the precision. Trailing
zeros shall be removed from the fractional portion of the
result; a radix character shall appear only if it is followed by
a digit.
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.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 distinguish val-
ues 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 conver-
sion. 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() func-
tion and the resulting wide character shall be written. Other-
wise, 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. Char-
acters 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 speci-
fied, 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 con-
tains 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 con-
tains 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 man-
ner.
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. 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 st_ctime and st_mtime fields 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() may fail if:
EILSEQ A wide-character code that does not correspond to a valid char-
acter has been detected.
EINVAL There are insufficient arguments.
In addition, wprintf() and fwprintf() may fail if:
ENOMEM Insufficient storage space is available.
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
btowc(), fputwc(), fwscanf(), mbrtowc(), setlocale(), the Base Defini-
tions volume of IEEE Std 1003.1-2001, Chapter 7, Locale, <stdio.h>,
<wchar.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 FWPRINTF(3P)
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