NAME
wprintf,
fwprintf,
swprintf,
vwprintf,
vfwprintf,
vswprintf —
formatted wide character output conversion
LIBRARY
Standard C Library (libc, -lc)
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,
...);
#include <stdarg.h>
int
vfwprintf(
FILE *
restrict stream,
const
wchar_t * restrict,
va_list
ap);
int
vswprintf(
wchar_t
* restrict ws,
size_t
n,
const wchar_t *restrict
format,
va_list ap);
int
vwprintf(
const
wchar_t * restrict format,
va_list ap);
DESCRIPTION
The
wprintf() family of functions produces output according to
a
format as described below. The
wprintf() and
vwprintf() functions write
output to
stdout
, the standard output stream;
fwprintf() and
vfwprintf() write output to
the given output
stream;
swprintf()
and
vswprintf() write to the wide-character string
ws.
These functions write the output under the control of a
format string that specifies how subsequent arguments
(or arguments accessed via the variable-length argument facilities of
stdarg(3)) are converted for
output.
The
swprintf() and
vswprintf() functions
will fail if
n or more wide characters were requested to
be written,
The format string is composed of zero or more directives: ordinary characters
(not
%), which are copied unchanged to the output stream;
and conversion specifications, each of which results in fetching zero or more
subsequent arguments. Each conversion specification is introduced by the
% character. The arguments must correspond properly (after
type promotion) with the conversion specifier. After the
%,
the following appear in sequence:
- An optional field, consisting of a decimal digit string
followed by a $, specifying the next argument to access.
If this field is not provided, the argument following the last argument
accessed will be used. Arguments are numbered starting at
1. If unaccessed arguments in the format string are
interspersed with ones that are accessed the results will be
indeterminate.
- Zero or more of the following flags:
-
-
- ‘#’
- The value should be converted to an “alternate
form”. For c, d,
i, n, p,
s, and u conversions, this option
has no effect. For o conversions, the precision of
the number is increased to force the first character of the output
string to a zero (except if a zero value is printed with an explicit
precision of zero). For x and X
conversions, a non-zero result has the string
‘
0x
’ (or
‘0X
’ for X
conversions) prepended to it. For a,
A, e, E,
f, F, g, and
G conversions, the result will always contain a
decimal point, even if no digits follow it (normally, a decimal point
appears in the results of those conversions only if a digit follows).
For g and G conversions, trailing
zeros are not removed from the result as they would otherwise be.
-
-
- ‘0’
(zero)
- Zero padding. For all conversions except
n, the converted value is padded on the left with
zeros rather than blanks. If a precision is given with a numeric
conversion (d, i,
o, u, i,
x, and X), the 0
flag is ignored.
-
-
- ‘-’
- A negative field width flag; the converted value is to
be left adjusted on the field boundary. Except for n
conversions, the converted value is padded on the right with blanks,
rather than on the left with blanks or zeros. A -
overrides a 0 if both are given.
-
-
- ‘ ’
(space)
- A blank should be left before a positive number
produced by a signed conversion (a,
A, d, e,
E, f, F,
g, G, or
i).
-
-
- ‘+’
- A sign must always be placed before a number produced
by a signed conversion. A + overrides a space if
both are used.
-
-
- ‘'’
- Decimal conversions (d,
u, or i) or the integral portion
of a floating point conversion (f or
F) should be grouped and separated by thousands
using the non-monetary separator returned by
localeconv(3).
- An optional decimal digit string specifying a minimum
field width. If the converted value has fewer characters than the field
width, it will be padded with spaces on the left (or right, if the
left-adjustment flag has been given) to fill out the field width.
- An optional precision, in the form of a period
. followed by an optional digit string. If the digit
string is omitted, the precision is taken as zero. This gives the minimum
number of digits to appear for d, i,
o, u, x, and
X conversions, the number of digits to appear after the
decimal-point for a, A,
e, E, f, and
F conversions, the maximum number of significant digits
for g and G conversions, or the
maximum number of characters to be printed from a string for
s conversions.
- An optional length modifier, that specifies the size of
the argument. The following length modifiers are valid for the
d, i, n,
o, u, x, or
X conversion:
Modifier |
d, i |
o, u,
x, X |
n |
hh |
signed char |
unsigned char |
signed char * |
h |
short |
unsigned short |
short * |
l
(ell) |
long |
unsigned long |
long * |
ll (ell
ell) |
long long |
unsigned long long |
long long * |
j |
intmax_t |
uintmax_t |
intmax_t * |
t |
ptrdiff_t |
(see note) |
ptrdiff_t * |
z |
(see note) |
size_t |
(see note) |
q
(deprecated) |
quad_t |
u_quad_t |
quad_t * |
Note: the t modifier, when applied to a
o, u, x, or
X conversion, indicates that the argument is of an
unsigned type equivalent in size to a ptrdiff_t. The
z modifier, when applied to a d or
i conversion, indicates that the argument is of a signed
type equivalent in size to a size_t. Similarly, when
applied to an n conversion, it indicates that the
argument is a pointer to a signed type equivalent in size to a
size_t.
The following length modifier is valid for the a,
A, e, E,
f, F, g, or
G conversion:
Modifier |
a, A,
e, E, f,
F, g, G |
L |
long double |
The following length modifier is valid for the c or
s conversion:
Modifier |
c |
s |
l
(ell) |
wint_t |
wchar_t * |
- A character that specifies the type of conversion to be
applied.
A field width or precision, or both, may be indicated by an asterisk
‘
*
’ or an asterisk followed by one or more
decimal digits and a ‘
$
’ instead of a
digit string. In this case, an
int argument supplies the
field width or precision. A negative field width is treated as a left
adjustment flag followed by a positive field width; a negative precision is
treated as though it were missing. If a single format directive mixes
positional (
nn$
) and non-positional arguments, the
results are undefined.
The conversion specifiers and their meanings are:
-
-
- diouxX
- The int (or appropriate variant)
argument is converted to signed decimal (d and
i), unsigned octal (o), unsigned
decimal (u), or unsigned hexadecimal
(x and X) notation. The letters
“
abcdef
” are used for
x conversions; the letters
“ABCDEF
” are used for
X conversions. The precision, if any, gives the minimum
number of digits that must appear; if the converted value requires fewer
digits, it is padded on the left with zeros.
-
-
- DOU
- The long int argument is converted to
signed decimal, unsigned octal, or unsigned decimal, as if the format had
been ld, lo, or lu
respectively. These conversion characters are deprecated, and will
eventually disappear.
-
-
- eE
- The double argument is rounded and
converted in the style
[-]d
.
ddde±
dd
where there is one digit before the decimal-point character 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 zero, no decimal-point character
appears. An E conversion uses the letter
‘E
’ (rather than
‘e
’) to introduce the exponent. The
exponent always contains at least two digits; if the value is zero, the
exponent is 00.
For a, A, e,
E, f, F,
g, and G conversions, positive and
negative infinity are represented as inf
and
-inf
respectively when using the lowercase
conversion character, and INF
and
-INF
respectively when using the uppercase
conversion character. Similarly, NaN is represented as
nan
when using the lowercase conversion, and
NAN
when using the uppercase conversion.
-
-
- fF
- The double argument is rounded and
converted to decimal notation in the style
[-]ddd
.
ddd,
where the number of digits after the decimal-point character is equal to
the precision specification. If the precision is missing, it is taken as
6; if the precision is explicitly zero, no decimal-point character
appears. If a decimal point appears, at least one digit appears before
it.
-
-
- gG
- The double argument is converted in
style f or e (or F
or E for G conversions). The precision
specifies the number of significant digits. If the precision is missing, 6
digits are given; if the precision is zero, it is treated as 1. Style
e is used if the exponent from its conversion is less
than -4 or greater than or equal to the precision. Trailing zeros are
removed from the fractional part of the result; a decimal point appears
only if it is followed by at least one digit.
-
-
- aA
- The double argument is converted to
hexadecimal notation in the style
[-]
0x
h.
hhhp[±]d,
where the number of digits after the hexadecimal-point character is equal
to the precision specification. If the precision is missing, it is taken
as enough to exactly represent the floating-point number; if the precision
is explicitly zero, no hexadecimal-point character appears. This is an
exact conversion of the mantissa+exponent internal floating point
representation; the
[-]0x
h.
hhh
portion represents exactly the mantissa; only denormalized mantissas have
a zero value to the left of the hexadecimal point. The p
is a literal character ‘p
’; the
exponent is preceded by a positive or negative sign and is represented in
decimal, using only enough characters to represent the exponent. The
A conversion uses the prefix
“0X
” (rather than
“0x
”), the letters
“ABCDEF
” (rather than
“abcdef
”) to represent the hex digits,
and the letter ‘P
’ (rather than
‘p
’) to separate the mantissa and
exponent.
-
-
- C
- Treated as c with the l
(ell) modifier.
-
-
- c
- The int argument is converted to an
unsigned char, then to a
wchar_t as if by
btowc(3), and the resulting
character is written.
If the l (ell) modifier is used, the
wint_t argument is converted to a
wchar_t and written.
-
-
- S
- Treated as s with the l
(ell) modifier.
-
-
- s
- The char * argument is expected to be
a pointer to an array of character type (pointer to a string) containing a
multibyte sequence. Characters from the array are converted to wide
characters and written up to (but not including) a terminating
NUL
character; if a precision is specified, no
more than the number specified are written. If a precision is given, no
null character need be present; if the precision is not specified, or is
greater than the size of the array, the array must contain a terminating
NUL
character.
If the l (ell) modifier is used, the
wchar_t * argument is expected to be a pointer to an
array of wide characters (pointer to a wide string). Each wide character
in the string is written. Wide characters from the array are written up to
(but not including) a terminating wide NUL
character; if a precision is specified, no more than the number specified
are written (including shift sequences). If a precision is given, no null
character need be present; if the precision is not specified, or is
greater than the number of characters in the string, the array must
contain a terminating wide NUL
character.
-
-
- p
- The void * pointer argument is
printed in hexadecimal (as if by ‘
%#x
’
or ‘%#lx
’).
-
-
- n
- The number of characters written so far is stored into the
integer indicated by the int * (or variant) pointer
argument. No argument is converted.
-
-
- %
- A ‘
%
’ is written. No
argument is converted. The complete conversion specification is
‘%%
’.
The decimal point character is defined in the program's locale (category
LC_NUMERIC
).
In no case does a non-existent or small field width cause truncation of a
numeric field; if the result of a conversion is wider than the field width,
the field is expanded to contain the conversion result.
RETURN VALUES
These functions return the number of characters printed (not including the
trailing ‘
\0
’ used to end output to
strings).
SEE ALSO
btowc(3),
fputws(3),
printf(3),
putwc(3),
setlocale(3),
wcsrtombs(3),
wscanf(3)
STANDARDS
The
wprintf(),
fwprintf(),
swprintf(),
vwprintf(),
vfwprintf() and
vswprintf() functions
conform to
ISO/IEC 9899:1999
(“ISO C99”).
SECURITY CONSIDERATIONS
Subject to the caveats noted in the
printf(3).