wprintf(3C)
NAME
fwprintf, wprintf, swprintf - print formatted wide-character
output
SYNOPSIS
#include <stdio.h>
#include <wchar.h>
int fwprintf(FILE *stream, const wchar_t *format, ...);
int wprintf(const wchar_t *format, <...);
int swprintf(wchar_t *s, size_t n, const wchar_t *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-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 for-
mat. 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 argu-
ment 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 inser-
tion of a language-dependent radix character in the output
string, output as a wide-character value. The radix charac-
ter 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 conver-
sions; the number of digits to appear after the radix
character for the e, E, and f conversions; the maximum
number of significant digits for the g and G conver-
sions; 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 l (ell) specifying that a following c
conversion wide-character applies to a wint_t argu-
ment; an optional l specifying that a following s
conversion wide-character applies to a wchar_t argu-
ment; an optional h specifying that a following d, i,
o, u, x, and X conversion wide-character applies to a
type short int or type unsigned short int argument
(the argument will have been promoted according to the
integral promotions, and its value will be converted
to type short int or unsigned short int before print-
ing); an optional h specifying that a following n
conversion wide-character applies to a pointer to a
type short int argument; an optional l (ell) specify-
ing that a following d, i, o, u, x, and X conversion
wide-character applies to a type long int or unsigned
long int argument; an optional l (ell) specifying that
a following n conversion wide-character applies to a
pointer to a type long int argument; or an optional L
specifying that a following e, E, f, g, or G conver-
sion wide-character applies to a type long double
argument. If an h, l, or L appears with any other
conversion wide-character, the behavior is undefined.
o A conversion 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 preci-
sion were omitted. In format wide-character strings contain-
ing 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 specifica-
tions (that is, %n$ and *m$), or unnumbered argument specif-
ications (that is, % and *), but normally not both. The only
exception to this is that %% can be mixed with the %n$ 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 conver-
sion (%i, %d, %u, %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
e, E, 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 fol-
lows 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, e, E, 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 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 con-
verted 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 preci-
sion of 0 is no wide-characters.
o The unsigned int argument is converted to unsigned
octal format in the style dddd. The precision speci-
fies 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 speci-
fies 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 con-
verted 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 preci-
sion 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 The double argument is converted to decimal notation
in the style [-]ddd.ddd, where the number of digits
after the radix character is equal to the precision
specification. If the precision is missing, it is
taken as 6; if the precision is explicitly 0 and no #
flag is present, no radix character appears. If a
radix character appears, at least one digit appears
before it. The value is rounded to the appropriate
number of digits.
The fwprintf() family of functions may make available
wide-character string representations for infinity and
NaN.
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 value is
rounded to the appropriate number of digits. 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.
The fwprintf() family of functions may make available
wide-character string representations for infinity and
NaN.
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.
The fwprintf() family of functions may make available
wide-character string representations for infinity and
NaN.
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 charac-
ter 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 ini-
tialized to zero before the first character is con-
verted, and written up to (but not including) the ter-
minating 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 char-
acters 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).
RETURN VALUES
Upon successful completion, these functions return the
number of wide-characters transmitted excluding the ter-
minating null wide-character in the case of swprintf() or a
negative value if an output error was encountered.
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-character 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 attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe with exceptions |
|_____________________________|_____________________________|
SEE ALSO
btowc(3C), fputwc(3C), fwscanf(3C), mbrtowc(3C),
setlocale(3C), attributes(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.
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