FWPRINTF(3C)FWPRINTF(3C)NAME
fwprintf, wprintf, swprintf - print formatted wide-character output
SYNOPSIS
#include <stdio.h>
#include <wchar.h>
int fwprintf(FILE *restrict stream, const wchar_t *restrict format,
...);
int wprintf(const wchar_t *restrict format, ...);
int swprintf(wchar_t *restrict s, size_t n, const wchar_t *restrict format,
...);
DESCRIPTION
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-charac‐
ter 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 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 wide-character % (see below) is replaced by the sequence
%n$, where n is a decimal integer in the range [1, NL_ARGMAX], giving
the position of the argument in the argument list. This feature pro‐
vides for the definition of format wide-character strings that select
arguments in an order appropriate to specific languages (see the EXAM‐
PLES section).
In format wide-character strings containing the %n$ form of conversion
specifications, numbered arguments in the argument list can be refer‐
enced 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 lan‐
guage-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$, after which the following appear in
sequence:
o Zero or more flags (in any order), which modify the meaning
of the conversion specification.
o An optional minimum field width. If the converted value has
fewer wide-characters than the field width, it will be
padded with spaces by default on the left; it will be padded
on the right, if the left-adjustment flag (−), described
below, is given to the field width. The field width takes
the form of an asterisk (*), described below, or a decimal
integer.
o An optional precision that gives the minimum number of dig‐
its to appear for the d, i, o, u, x, and X conversions; the
number of digits to appear after the radix character for the
a, A, e, E, f, and F conversions; the maximum number of sig‐
nificant digits for the g and G conversions; or the maximum
number of wide-characters to be printed from a string in s
conversions. The precision takes the form of a period (.)
followed by either an asterisk (*), described below, or an
optional decimal digit string, where a null digit string is
treated as 0. If a precision appears with any other conver‐
sion wide-character, the behavior is undefined.
o An optional length modifier that specifies the size of the
argument.
o A conversion specifier wide character that indicates the
type of conversion to be applied.
A field width, or precision, or both, may be indicated by an asterisk
(*). In this case an argument of type int supplies the field width or
precision. Arguments specifying field width, or precision, or both
must appear in that order before the argument, if any, to be converted.
A negative field width is taken as a − flag followed by a positive
field width. A negative precision is taken as if the precision were
omitted. In format wide-character strings containing the %n$ form of a
conversion specification, a field width or precision may be indicated
by the sequence *m$, where m is a decimal integer in the range [1,
NL_ARGMAX] giving the position in the argument list (after the format
argument) of an integer argument containing the field width or preci‐
sion, for example:
wprintf(L"%1$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 unde‐
fined. 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 preci‐
sion (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 conver‐
sions, 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 speci‐
fied, 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 conver‐
sion 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 argu‐
ment.
h
Specifies that a following d, i, o, u, x, or X conver‐
sion specifier applies to a short or unsigned short
argument (the argument will have been promoted accord‐
ing 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 conver‐
sion specifier applies to a long or unsigned long argu‐
ment; 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 conver‐
sion specifier applies to a long long or unsigned long
long argument; or that a following n conversion speci‐
fier applies to a pointer to a long long argument.
j
Specifies that a following d, i, o, u, x, or X conver‐
sion 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 conver‐
sion 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 conver‐
sion specifier applies to a ptrdiff_t or the corre‐
sponding 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 repre‐
sented 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 for‐
mat in the style dddd. The precision specifies the minimum num‐
ber 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 pre‐
cision 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 speci‐
fication. 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 miss‐
ing, 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 con‐
version 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 con‐
verted in the style "[-]0xh.hhhhp±d", where the single hexadec‐
imal digit preceding the radix point is 0 if the value con‐
verted 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 for‐
mat according to the prevailing floating point rounding direc‐
tion 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 con‐
verted to a wide-character as if by calling the btowc(3C) func‐
tion 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) func‐
tion, with the conversion state described by an mbstate_t
object initialized to zero before the first character is con‐
verted, 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-char‐
acter. 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-charac‐
ters.
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 argu‐
ment 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. Charac‐
ters 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).
RETURN VALUES
Upon successful completion, these functions 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.
If n or more wide characters were requested to be written, swprintf()
returns a negative value.
ERRORS
For the conditions under which fwprintf() and wprintf() will fail and
may fail, refer to fputwc(3C).
In addition, all forms of fwprintf() may fail if:
EILSEQ
A wide-character code that does not correspond to a valid
character has been detected.
EINVAL
There are insufficient arguments.
In addition, wprintf() and fwprintf() may fail if:
ENOMEM
Insufficient storage space is available.
EXAMPLES
Example 1 Print Language-dependent Date and Time Format.
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
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────────────┤
│Interface Stability │ Standard │
├────────────────────┼─────────────────────────┤
│MT-Level │ MT-Safe with exceptions │
└────────────────────┴─────────────────────────┘
SEE ALSObtowc(3C), fputwc(3C), fwscanf(3C), mbrtowc(3C), setlocale(3C),
attributes(5), standards(5)NOTES
The fwprintf(), wprintf(), and swprintf() functions can be used safely
in multithreaded applications, as long as setlocale(3C) is not being
called to change the locale.
If the j length modifier is used, 32-bit applications that were com‐
piled using c89 on releases prior to Solaris 10 will experience unde‐
fined behavior.
Nov 1, 2003 FWPRINTF(3C)