DragonFly On-Line Manual Pages
WPRINTF(3) DragonFly Library Functions Manual WPRINTF(3)
wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted
wide character output conversion
Standard C Library (libc, -lc)
fwprintf(FILE * restrict stream, const wchar_t * restrict format, ...);
swprintf(wchar_t * restrict ws, size_t n,
const wchar_t * restrict format, ...);
wprintf(const wchar_t * restrict format, ...);
vfwprintf(FILE * restrict stream, const wchar_t * restrict format,
vswprintf(wchar_t * restrict ws, size_t n,
const wchar_t *restrict format, va_list ap);
vwprintf(const wchar_t * restrict format, va_list ap);
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
These functions return the number of characters printed (not including
the trailing `\0' used to end output to strings).
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
`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
` ' (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
* 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
* 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
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 *
L (non-standard) 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
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
ll (non-standard) 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
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
aA The double argument is converted to hexadecimal notation in
the style [-]0xh.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
[-]0xh.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
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
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.
btowc(3), fputws(3), printf(3), putwc(3), setlocale(3), wcsrtombs(3),
Subject to the caveats noted in the BUGS section of printf(3), the
wprintf(), fwprintf(), swprintf(), vwprintf(), vfwprintf() and
vswprintf() functions conform to ISO/IEC 9899:1999 ("ISO C99").
As an extension, DragonFly treats the length modifiers ll and L as
synonyms, so that the non-standard %Ld is equivalent to %ld and the non-
standard %llg is equivalent to %Lg.
Refer to printf(3).
DragonFly 6.3-DEVELOPMENT March 21, 2022 DragonFly 6.3-DEVELOPMENT