FWPRINTF(3C) Standard C Library Functions 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-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).
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-
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(7) for descriptions of the following attributes:
+--------------------+-------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------------+
|Interface Stability | Standard |
+--------------------+-------------------------+
|MT-Level | MT-Safe with exceptions |
+--------------------+-------------------------+
SEE ALSO
btowc(3C),
fputwc(3C),
fwscanf(3C),
mbrtowc(3C),
setlocale(3C),
attributes(7),
standards(7)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
compiled using
c89 on releases prior to Solaris 10 will experience
undefined behavior.
February 17, 2023 FWPRINTF(3C)
