The fwprintf() function places output on the named output
stream. The wprintf() function places output on the standard
output stream stdout. The swprintf() function places output
followed by the null wide-character in consecutive wide-characters starting
at *s; no more than n wide-characters are written, including a
terminating null wide-character, which is always added (unless n is
zero).
Each of these functions converts, formats and prints 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 wide-character % (see below) is replaced
by the sequence %n$, where n is a decimal
integer in the range [1, NL_ARGMAX], giving the position of the
argument in the argument list. This feature provides for the definition of
format wide-character strings that select arguments in an order appropriate
to specific languages (see the EXAMPLES section).
In format wide-character strings containing the
%n$ form of conversion specifications, 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 specifications, each argument in the argument list is used
exactly once.
All forms of the fwprintf() functions allow for the
insertion of a language-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
defaults to a period (.).
Each conversion specification is introduced by the %
wide-character or by the wide-character sequence %n$,
after which the following appear in sequence:
- o
- Zero or more flags (in any order), which modify the meaning of the
conversion specification.
- o
- An optional minimum field width. If the converted value has fewer
wide-characters than the field width, it will be padded with spaces by
default on the left; it will be padded on the right, if the
left-adjustment flag (−), described below, is given to the
field width. The field width takes the form of an asterisk (*), described
below, or a decimal integer.
- o
- An optional precision that gives the minimum number of digits to
appear for the d, i, o, u, x, and
X conversions; the number of digits to appear after the radix
character for the a, A, e, E, f, and
F conversions; the maximum number of significant digits for the
g and G conversions; or the maximum number of
wide-characters to be printed from a string in s conversions. The
precision takes the form of a period (.) followed by either an asterisk
(*), described below, or an optional decimal digit string, where a null
digit string is treated as 0. If a precision appears with any other
conversion wide-character, the behavior is undefined.
- o
- An optional length modifier that specifies the size of the argument.
- o
- A conversion specifier wide character that indicates the type of
conversion to be applied.
A field width, or precision, or both, may be indicated by an
asterisk (*). In this case an argument of type int supplies the field
width or precision. Arguments specifying field width, or precision, or both
must appear in that order before the argument, if any, to be converted. A
negative field width is taken as a − flag followed by a
positive field width. A negative precision is taken as if the precision were
omitted. In format wide-character strings containing the
%n$ 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 format can contain either numbered argument
specifications (that is, %n$ and
*m$), or unnumbered argument specifications (that is,
% and *), but normally not both. The only exception to this is
that %% can be mixed with the %n$ 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.
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) will be formatted with thousands' grouping wide-characters. For
other conversions the behavior is undefined. The non-monetary grouping
wide-character is used.
−
The result of the conversion will be left-justified
within the field. The conversion will be right-justified if this flag is not
specified.
+
The result of a signed conversion will always begin with
a sign (+ or −). The conversion will 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 will
be prefixed to the result. This means that if the space and + flags
both appear, the space flag will be ignored.
#
This flag 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 conversions, a non-zero result will have 0x (or 0X) prefixed to it.
For a, A, e, E, f, F, g, or
G conversions, the result will 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 conversions, trailing zeros will not be removed from the
result as they normally are. For other conversions, the behavior is
undefined.
0
For d, i, o, u, x,
X, a, A, e, E, f, F,
g, and G conversions, 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 will be ignored. For d, i, o, u, x,
and X conversions, if a precision is specified, the 0 flag will
be ignored. If the 0 and ' 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:
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 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 wide-characters and their meanings are:
d, i
The int argument is 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 will be expanded with leading zeros. The
default precision is 1. The result of converting 0 with an explicit precision
of 0 is no wide-characters.
o
The unsigned int argument is 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 will be expanded with leading zeros. The default precision is
1. The result of converting 0 with an explicit precision of 0 is no
wide-characters.
u
The unsigned int argument is 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 will be expanded with leading zeros. The default precision is
1. The result of converting 0 with an explicit precision of 0 is no
wide-characters.
x
The unsigned int argument is 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 will be expanded with leading
zeros. The default precision is 1. The result of converting 0 with an explicit
precision of 0 is no wide-characters.
X
Behaves the same as the x conversion
wide-character except that letters "ABCDEF" are used instead
of "abcdef".
f, F
The
double argument is converted to decimal
notation in the style [
−]
ddd.ddd, where the
number of digits after the radix character (see
setlocale(3C)) is equal
to the precision specification. If the precision is missing it is taken as 6;
if the precision is explicitly 0 and the
# flag is not specified, no
radix character appears. If a radix character appears, at least 1 digit
appears before it. The converted value is rounded to fit the specified output
format according to the prevailing floating point rounding direction mode. If
the conversion is not exact, an inexact exception is raised.
For the f specifier, a double argument representing an
infinity or NaN is converted in the style of the e conversion
specifier, except that for an infinite argument, "infinity" or
"Infinity" is printed when the precision is at least 8 and
"inf" or "Inf" is printed otherwise.
For the F specifier, a double argument representing an infinity or
NaN is converted in the SUSv3 style of the E conversion specifier, except
that for an infinite argument, "INFINITY" is printed when the
precision is at least 8 and or "INF" is printed otherwise.
e, E
The
double argument is converted in the style
[−
]d.ddde±dd, where there is one digit
before the radix character (which is non-zero if the argument is non-zero) and
the number of digits after it is equal to the precision; if the precision is
missing, it is taken as 6; if the precision is 0 and no
# flag is
present, no radix character appears. The converted value is rounded to fit the
specified output format according to the prevailing floating point rounding
direction mode. If the conversion is not exact, an inexact exception is
raised. The
E conversion wide-character will produce a number with
E instead of
e introducing the exponent. The exponent always
contains at least two digits. If the value is 0, the exponent is 0.
Infinity and NaN values are handled in one of the following
ways:
SUSv3
For the e specifier, a double argument
representing an infinity is printed as "[−]infinity",
when the precision for the conversion is at least 7 and as
"[−]inf" otherwise. A double argument
representing a NaN is printed as "[−]nan". For the
E specifier, "INF", "INFINITY", and
"NAN" are printed instead of "inf",
"infinity", and "nan", respectively.
Printing of the sign follows the rules described above.
Default
A double argument representing an infinity is
printed as "[−]Infinity", when the precision for the
conversion is at least 7 and as "[−]Inf" otherwise. A
double argument representing a NaN is printed as
"[−]NaN". Printing of the sign follows the rules
described above.
g, G
The
double argument is converted in the style
f or
e (or in the style
E in the case of a
G
conversion wide-character), with the precision specifying the number of
significant digits. If an explicit precision is 0, it is taken as 1. The style
used depends on the value converted; style
e (or
E) will 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 are removed from the
fractional portion of the result; a radix character appears only if it is
followed by a digit.
A double argument representing an infinity or NaN is
converted in the style of the e or E conversion specifier,
except that for an infinite argument, "infinity",
"INFINITY", or "Infinity" is printed when the precision
is at least 8 and "inf", "INF", or "Inf" is
printed otherwise.
a, A
A double argument representing a floating-point number is
converted in the style "[-]
0xh.hhhhp±d", where the
single hexadecimal digit preceding the radix point is 0 if the value converted
is zero and 1 otherwise and the number of hexadecimal digits after it are
equal to the precision; if the precision is missing, the number of digits
printed after the radix point is 13 for the conversion of a double value, 16
for the conversion of a long double value on x86, and 28 for the conversion of
a long double value on SPARC; if the precision is zero and the '#' flag is not
specified, no decimal-point wide character appears. 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 always
contains 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 is
zero.
The converted valueis rounded to fit the specified output format
according to the prevailing floating point rounding direction mode. If the
conversion is not exact, an inexact exception is raised.
A double argument representing an infinity or NaN is
converted in the SUSv3 style of an e or E conversion
specifier.
c
If no
l (ell) qualifier is present, the
int
argument is converted to a wide-character as if by calling the
btowc(3C) function and the resulting wide-character is written.
Otherwise the
wint_t argument is converted to
wchar_t, and
written.
s
If no
l (ell) qualifier is present, the argument
must be a pointer to a character array containing a character sequence
beginning in the initial shift state. Characters from the array are converted
as if by repeated calls to the
mbrtowc(3C) 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 are written. If the precision is not specified
or is greater than the size of the array, the array must contain a null
wide-character.
If an l (ell) qualifier is present, the argument must be a
pointer to an array of type wchar_t. Wide characters from the array
are 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
array must contain a null wide-character. If a precision is specified, no
more than that many wide-characters are written.
p
The argument must be a pointer to void. The value
of the pointer is converted to a sequence of printable wide-characters.
n
The argument must be 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 is
converted.
C
Same as lc.
S
Same as ls.
%
Output a % wide-character; no argument is converted. The
entire conversion specification must be %%.
If a conversion specification does not match one of the above
forms, the behavior is undefined.
In no case does a non-existent or small field width cause
truncation of a field; if the result of a conversion is wider than the field
width, the field is simply expanded to contain the conversion result.
Characters generated by fwprintf() and wprintf() are printed
as if fputwc(3C) had been called.
The st_ctime and st_mtime fields of the file will 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(3C) or fclose(3C) on the same stream or a
call to exit(3C) or abort(3C).