'\" et

.TH FWPRINTF "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

fwprintf,

swprintf,

wprintf

\(em print formatted wide-character output

.SH SYNOPSIS

.LP

.nf

#include <stdio.h>

#include <wchar.h>

.P

int fwprintf(FILE *restrict \fIstream\fP, const wchar_t *restrict \fIformat\fP, ...);

int swprintf(wchar_t *restrict \fIws\fP, size_t \fIn\fP,

    const wchar_t *restrict \fIformat\fP, ...);

int wprintf(const wchar_t *restrict \fIformat\fP, ...);

.fi

.SH DESCRIPTION

The functionality described on this reference page is aligned with the

ISO\ C standard. Any conflict between the requirements described here and the

ISO\ C standard is unintentional. This volume of POSIX.1\(hy2008 defers to the ISO\ C standard.

.P

The

\fIfwprintf\fR()

function shall place output on the named output

.IR stream .

The

\fIwprintf\fR()

function shall place output on the standard output stream

.IR stdout .

The

\fIswprintf\fR()

function shall place output followed by the null wide character in

consecutive wide characters starting at *\fIws\fP; no more than

.IR n

wide characters shall be written, including a terminating null wide

character, which is always added (unless

.IR n

is zero).

.P

Each of these functions shall convert, format, and print its arguments

under control of the

.IR format

wide-character string. The

.IR format

is composed of zero or more directives:

.IR "ordinary wide-characters" ,

which are simply copied to the output stream, and

.IR "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

.IR format .

If the

.IR format

is exhausted while arguments remain, the excess arguments are evaluated

but are otherwise ignored.

.P

Conversions can be applied to the

.IR n th

argument after the

.IR format

in the argument list, rather than to the next unused argument. In this

case, the conversion specifier wide character

.BR %

(see below) is replaced by the

sequence

.BR \(dq%n$\(dq ,

where

.IR 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

.IR format

wide-character strings that select arguments in an order appropriate to

specific languages (see the EXAMPLES section).

.P

The

.IR format

can contain either numbered argument specifications (that is,

\fR"%\fIn\fR$"\fR and \fR"*\fIm\fR$"\fR), or unnumbered argument

conversion specifications (that is,

.BR %

and

.BR * ),

but not both. The only exception to this is that

.BR %%

can be mixed with the \fR"%\fIn\fR$"\fR form. The results of mixing

numbered and unnumbered argument specifications in a

.IR format

wide-character string are undefined. When numbered argument

specifications are used, specifying the

.IR N th

argument requires that all the leading arguments, from the first to the

(\fIN\fP\(mi1)th, are specified in the

.IR format

wide-character string.

.P

In

.IR format

wide-character strings containing the \fR"%\fIn\fR$"\fR form of

conversion specification, numbered arguments in the argument list can

be referenced from the

.IR format

wide-character string as many times as required.

.P

In

.IR format

wide-character strings containing the

.BR %

form of conversion specification, each argument in the argument list

shall be used exactly once.

.P

All forms of the

\fIfwprintf\fR()

function allow for the insertion of a locale-dependent radix

character in the output string, output as a wide-character value. The

radix character is defined in the current locale (category

.IR LC_NUMERIC ).

In the POSIX locale, or in a locale where the radix character is not

defined, the radix character shall default to a

<period>

(\c

.BR '.' ).

.br

.P

Each conversion specification is introduced by the

.BR '%' 

wide character

or by the wide-character sequence \fR"%\fIn\fR$"\fR,

after which the following appear in sequence:

.IP " *" 4

Zero or more

.IR flags

(in any order), which modify the meaning of the conversion

specification.

.IP " *" 4

An optional minimum

.IR "field width" .

If the converted value has fewer wide characters than the field width,

it shall be padded with

<space>

characters by default on the left; it shall be padded on the right,

if the left-adjustment flag (\c

.BR '\(mi' ),

described below, is given to the field width. The field width takes the

form of an

<asterisk>

(\c

.BR '*' ),

described below, or a decimal integer.

.IP " *" 4

An optional

.IR precision

that gives the minimum number of digits to appear for the

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

and

.BR X

conversion specifiers; the number of digits to appear after the radix

character for the

.BR a ,

.BR A ,

.BR e ,

.BR E ,

.BR f ,

and

.BR F

conversion specifiers; the maximum number of significant digits for the

.BR g

and

.BR G

conversion specifiers; or the maximum number of wide characters to be

printed from a string in the

.BR s

conversion specifiers. The precision takes the form of a

<period>

(\c

.BR '.' )

followed either by an

<asterisk>

(\c

.BR '*' ),

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.

.IP " *" 4

An optional length modifier that specifies the size of the argument.

.IP " *" 4

A

.IR "conversion specifier"

wide character that indicates the type of conversion to be applied.

.P

A field width, or precision, or both, may be indicated by an

<asterisk>

(\c

.BR '*' ).

In this case an argument of type

.BR int

supplies the field width or precision. Applications shall ensure that

arguments specifying field width, or precision, or both appear in that

order before the argument, if any, to be converted. A negative field

width is taken as a

.BR '\(mi' 

flag followed by a positive field width. A negative precision is taken

as if the precision were omitted.

In

.IR format

wide-character strings containing the \fR"%\fIn\fR$"\fR form

of a conversion specification, a field width or precision may be

indicated by the sequence \fR"*\fIm\fR$"\fR, where

.IR m

is a decimal integer in the range [1,{NL_ARGMAX}] giving the position

in the argument list (after the

.IR format

argument) of an integer argument containing the field width or

precision, for example:

.sp

.RS 4

.nf

\fB

wprintf(L"%1$d:%2$.*3$d:%4$.*3$d\en", hour, min, precision, sec); \*?

.fi \fR

.P

.RE

.P

The flag wide characters and their meanings are:

.IP "\fR'\fR" 8

(The

<apostrophe>.)

The integer portion of the result of a decimal conversion (\c

.BR %i ,

.BR %d ,

.BR %u ,

.BR %f ,

.BR %F ,

.BR %g ,

or

.BR %G )

shall be formatted with thousands' grouping wide characters. For other

conversions, the behavior is undefined. The numeric grouping wide

character is used.

.IP "\fR\(mi\fR" 8

The result of the conversion shall be left-justified within the field.

The conversion shall be right-justified if this flag is not specified.

.IP "\fR+\fR" 8

The result of a signed conversion shall always begin with a sign (\c

.BR '+' 

or

.BR '\(mi' ).

The conversion shall begin with a sign only when a negative value is

converted if this flag is not specified.

.IP <space> 8

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>

shall be prefixed to the result. This means that if the

<space>

and

.BR '+' 

flags both appear, the

<space>

flag shall be ignored.

.IP "\fR#\fR" 8

Specifies that the value is to be converted to an alternative form.

For

.BR o

conversion, it increases the precision (if necessary) to force the

first digit of the result to be 0. For

.BR x

or

.BR X

conversion specifiers, a non-zero result shall have 0x (or 0X) prefixed

to it. For

.BR a ,

.BR A ,

.BR e ,

.BR E ,

.BR f ,

.BR F ,

.BR g ,

and

.BR G

conversion specifiers, the result shall 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

.BR g

and

.BR G

conversion specifiers, trailing zeros shall

.IR not

be removed from the result as they normally are. For other conversion

specifiers, the behavior is undefined.

.IP "\fR0\fR" 8

For

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

.BR X ,

.BR a ,

.BR A ,

.BR e ,

.BR E ,

.BR f ,

.BR F ,

.BR g ,

and

.BR G

conversion specifiers, leading zeros (following any indication of sign

or base) are used to pad to the field width rather than performing

space padding, except when converting an infinity or NaN. If the

.BR '0' 

and

.BR '\(mi' 

flags both appear, the

.BR '0' 

flag shall be ignored. For

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

and

.BR X

conversion specifiers, if a precision is specified, the

.BR '0' 

flag shall be ignored.

If the

.BR '0' 

and

<apostrophe>

flags both appear, the grouping wide characters are inserted before

zero padding. For other conversions, the behavior is undefined.

.P

The length modifiers and their meanings are:

.IP "\fRhh\fR" 8

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to a

.BR "signed char"

or

.BR "unsigned char"

argument (the argument will have been promoted according to the integer

promotions, but its value shall be converted to

.BR "signed char"

or

.BR "unsigned char"

before printing); or that a following

.BR n

conversion specifier applies to a pointer to a

.BR "signed char"

argument.

.IP "\fRh\fR" 8

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to a

.BR "short"

or

.BR "unsigned short"

argument (the argument will have been promoted according to the integer

promotions, but its value shall be converted to

.BR "short"

or

.BR "unsigned short"

before printing); or that a following

.BR n

conversion specifier applies to a pointer to a

.BR "short"

argument.

.IP "\fRl\fR\ (ell)" 8

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to a

.BR "long"

or

.BR "unsigned long"

argument; that a following

.BR n

conversion specifier applies to a pointer to a

.BR "long"

argument; that a following

.BR c

conversion specifier applies to a

.BR wint_t

argument; that a following

.BR s

conversion specifier applies to a pointer to a

.BR wchar_t

argument; or has no effect on a following

.BR a ,

.BR A ,

.BR e ,

.BR E ,

.BR f ,

.BR F ,

.BR g ,

or

.BR G

conversion specifier.

.IP "\fRll\fR\ (ell-ell)" 8

.br

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to a

.BR "long long"

or

.BR "unsigned long long"

argument; or that a following

.BR n

conversion specifier applies to a pointer to a

.BR "long long"

argument.

.IP "\fRj\fR" 8

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to an

.BR intmax_t

or

.BR uintmax_t

argument; or that a following

.BR n

conversion specifier applies to a pointer to an

.BR intmax_t

argument.

.IP "\fRz\fR" 8

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to a

.BR size_t

or the corresponding signed integer type argument; or that a following

.BR n

conversion specifier applies to a pointer to a signed integer type

corresponding to a

.BR size_t

argument.

.IP "\fRt\fR" 8

Specifies that a following

.BR d ,

.BR i ,

.BR o ,

.BR u ,

.BR x ,

or

.BR X

conversion specifier applies to a

.BR ptrdiff_t

or the corresponding

.BR unsigned

type argument; or that a following

.BR n

conversion specifier applies to a pointer to a

.BR ptrdiff_t

argument.

.IP "\fRL\fR" 8

Specifies that a following

.BR a ,

.BR A ,

.BR e ,

.BR E ,

.BR f ,

.BR F ,

.BR g ,

or

.BR G

conversion specifier applies to a

.BR "long double"

argument.

.br

.P

If a length modifier appears with any conversion specifier other than

as specified above, the behavior is undefined.

.P

The conversion specifiers and their meanings are:

.IP "\fRd\fR,\ \fRi\fR" 8

The

.BR int

argument shall be converted to a signed decimal in the style

\fR"[\(mi]\fIdddd"\fR. The precision specifies the minimum number of

digits to appear; if the value being converted can be represented in

fewer digits, it shall be expanded with leading zeros. The default

precision shall be 1. The result of converting zero with an explicit

precision of zero shall be no wide characters.

.IP "\fRo\fP" 8

The

.BR unsigned

argument shall be converted to unsigned octal format in the style

.BR \(dqdddd\(dq .

The precision specifies the minimum number of digits to appear; if the

value being converted can be represented in fewer digits, it shall be

expanded with leading zeros. The default precision shall be 1. The

result of converting zero with an explicit precision of zero shall be

no wide characters.

.IP "\fRu\fP" 8

The

.BR unsigned

argument shall be converted to unsigned decimal format in the style

.BR \(dqdddd\(dq .

The precision specifies the minimum number of digits to appear; if the

value being converted can be represented in fewer digits, it shall be

expanded with leading zeros. The default precision shall be 1. The

result of converting zero with an explicit precision of zero shall be

no wide characters.

.IP "\fRx\fP" 8

The

.BR unsigned

argument shall be converted to unsigned hexadecimal format in the style

.BR \(dqdddd\(dq ;

the letters

.BR \(dqabcdef\(dq 

are used. The precision specifies the minimum number of digits to

appear; if the value being converted can be represented in fewer

digits, it shall be expanded with leading zeros. The default precision

shall be 1. The result of converting zero with an explicit precision of

zero shall be no wide characters.

.IP "\fRX\fP" 8

Equivalent to the

.BR x

conversion specifier, except that letters

.BR \(dqABCDEF\(dq 

are used instead of

.BR \(dqabcdef\(dq .

.IP "\fRf\fR,\ \fRF\fR" 8

The

.BR double

argument shall be converted to decimal notation in the style

\fR"[\(mi]\fIddd.ddd"\fR, where the number of digits after the radix

character shall be equal to the precision specification. If the

precision is missing, it shall be taken as 6; if the precision is

explicitly zero and no

.BR '#' 

flag is present, no radix character shall appear. If a radix character

appears, at least one digit shall appear before it. The value shall be

rounded in an implementation-defined manner to the appropriate number

of digits.

.RS 8 

.P

A

.BR double

argument representing an infinity shall be converted in one of the

styles

.BR \(dq[\(mi]inf\(dq 

or

.BR \(dq[\(mi]infinity\(dq ;

which style is implementation-defined. A

.BR double

argument representing a NaN shall be converted in one of the styles

.BR \(dq[\(mi]nan\(dq 

or \fR"[\(mi]nan(\fIn-char-sequence\fR)"\fR; which style, and the

meaning of any \fIn-char-sequence\fR, is implementation-defined. The

.BR F

conversion specifier produces

.BR \(dqINF\(dq ,

.BR \(dqINFINITY\(dq ,

or

.BR \(dqNAN\(dq 

instead of

.BR \(dqinf\(dq ,

.BR \(dqinfinity\(dq ,

or

.BR \(dqnan\(dq ,

respectively.

.RE

.IP "\fRe\fR,\ \fRE\fR" 8

The

.BR double

argument shall be converted in the style

\fR"[\(mi]\fId.ddd\fRe\fR\(+-dd"\fR, where there shall be one digit

before the radix character (which is non-zero if the argument is

non-zero) and the number of digits after it shall be equal to the

precision; if the precision is missing, it shall be taken as 6; if the

precision is zero and no

.BR '#' 

flag is present, no radix character shall appear. The value shall be

rounded in an implementation-defined manner to the appropriate number

of digits. The

.BR E

conversion wide character shall produce a number with

.BR 'E' 

instead of

.BR 'e' 

introducing the exponent. The exponent shall always contain at least

two digits. If the value is zero, the exponent shall be zero.

.RS 8 

.P

A

.BR double

argument representing an infinity or NaN shall be converted in the

style of an

.BR f

or

.BR F

conversion specifier.

.RE

.IP "\fRg\fR,\ \fRG\fR" 8

The

.BR double

argument representing a floating-point number shall be converted in the

style

.BR f

or

.BR e

(or in the style

.BR F

or

.BR E

in the case of a

.BR G

conversion specifier), depending on the value converted and the precision.

Let

.BR P

equal the precision if non-zero, 6 if the precision is omitted, or 1 if the

precision is zero. Then, if a conversion with style

.BR E

would have an exponent of

.IR X :

.RS 8 

.IP -- 4

If

.BR P >\c

.IR X \(>=\(mi4,

the conversion shall be with style

.BR f

(or

.BR F )

and precision

.BR P \(mi(\c

.IR X +1).

.IP -- 4

Otherwise, the conversion shall be with style

.BR e

(or

.BR E )

and precision

.BR P \(mi1.

.P

Finally, unless the

.BR '#' 

flag is used, any trailing zeros shall be removed from the fractional

portion of the result and the decimal-point character shall be removed

if there is no fractional portion remaining.

.P

A

.BR double

argument representing an infinity or NaN shall be converted in the

style of an

.BR f

or

.BR F

conversion specifier.

.RE

.IP "\fRa\fR,\ \fRA\fR" 8

A

.BR double

argument representing a floating-point number shall be converted in

the style \fR"[\(mi]0x\fIh\fR.\fIhhhh\fRp\(+-\fId\fR"\fR, where there

shall be one hexadecimal digit (which is non-zero if the argument is a

normalized floating-point number and is otherwise unspecified) before

the decimal-point wide character and the number of hexadecimal digits

after it shall be equal to the precision; if the precision is missing

and FLT_RADIX is a power of 2, then the precision shall be sufficient

for an exact representation of the value; if the precision is missing

and FLT_RADIX is not a power of 2, then the precision shall be sufficient

to distinguish values of type

.BR double ,

except that trailing zeros may be omitted; if the precision is zero and

the

.BR '#' 

flag is not specified, no decimal-point wide character shall appear.

The letters

.BR \(dqabcdef\(dq 

are used for

.BR a

conversion and the letters

.BR \(dqABCDEF\(dq 

for

.BR A

conversion. The

.BR A

conversion specifier produces a number with

.BR 'X' 

and

.BR 'P' 

instead of

.BR 'x' 

and

.BR 'p' .

The exponent shall always contain 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 shall be zero.

.RS 8 

.P

A

.BR double

argument representing an infinity or NaN shall be converted in the

style of an

.BR f

or

.BR F

conversion specifier.

.RE

.IP "\fRc\fP" 8

If no

.BR l

(ell) qualifier is present, the

.BR int

argument shall be converted to a wide character as if by calling the

\fIbtowc\fR()

function and the resulting wide character shall be written. Otherwise,

the

.BR wint_t

argument shall be converted to

.BR wchar_t ,

and written.

.IP "\fRs\fP" 8

If no

.BR l

(ell) qualifier is present, the application shall ensure that the

argument is a pointer to a character array containing a character

sequence beginning in the initial shift state. Characters from the

array shall be converted as if by repeated calls to the

\fImbrtowc\fR()

function, with the conversion state described by an

.BR 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

shall be written. If the precision is not specified, or is greater than

the size of the array, the application shall ensure that the array

contains a null wide character.

.RS 8 

.P

If an

.BR l

(ell) qualifier is present, the application shall ensure that the

argument is a pointer to an array of type

.BR wchar_t .

Wide characters from the array shall be 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 application

shall ensure that the array contains a null wide character. If a

precision is specified, no more than that many wide characters shall be

written.

.RE

.IP "\fRp\fP" 8

The application shall ensure that the argument is a pointer to

.BR void .

The value of the pointer shall be converted to a sequence of printable

wide characters in an implementation-defined manner.

.IP "\fRn\fP" 8

The application shall ensure that the argument is 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

\fIfwprintf\fR()

functions. No argument shall be converted, but one shall be consumed.

If the conversion specification includes any flags, a field width, or a

precision, the behavior is undefined.

.IP "\fRC\fP" 8

Equivalent to

.BR lc .

.IP "\fRS\fP" 8

Equivalent to

.BR ls .

.IP "\fR%\fR" 8

Output a

.BR '%' 

wide character; no argument shall be converted. The entire conversion

specification shall be

.BR %% .

.P

If a conversion specification does not match one of the above forms,

the behavior is undefined.

.P

In no case does a nonexistent or small field width cause truncation of

a field; if the result of a conversion is wider than the field width,

the field shall be expanded to contain the conversion result.

Characters generated by

\fIfwprintf\fR()

and

\fIwprintf\fR()

shall be printed as if

\fIfputwc\fR()

had been called.

.P

For

.BR a

and

.BR A

conversions, if FLT_RADIX is not a power of 2 and the result is not

exactly representable in the given precision, the result should be one

of the two adjacent numbers in hexadecimal floating style with the

given precision, with the extra stipulation that the error should have

a correct sign for the current rounding direction.

.P

For

.BR e ,

.BR E ,

.BR f ,

.BR F ,

.BR g ,

and

.BR G

conversion specifiers, if the number of significant decimal digits is

at most DECIMAL_DIG, then the result should be correctly rounded. If

the number of significant decimal digits is more than DECIMAL_DIG but

the source value is exactly representable with DECIMAL_DIG digits, then

the result should be an exact representation with trailing zeros.

Otherwise, the source value is bounded by two adjacent decimal strings

.IR L

<

.IR U ,

both having DECIMAL_DIG significant digits; the value of the resultant

decimal string

.IR D

should satisfy

.IR L

<=

.IR D

<=

.IR U ,

with the extra stipulation that the error should have a correct sign

for the current rounding direction.

.P

The last data modification and last file status change timestamps

of the file shall be marked for update between the call to a

successful execution of

\fIfwprintf\fR()

or

\fIwprintf\fR()

and the next successful completion of a call to

\fIfflush\fR()

or

\fIfclose\fR()