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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 

.TH "FWSCANF" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"

.\" fwscanf 

.SH NAME

fwscanf, swscanf, wscanf \- convert formatted wide-character input

.SH SYNOPSIS

.LP

\fB#include <stdio.h>

.br

#include <wchar.h>

.br

.sp

int fwscanf(FILE *restrict\fP \fIstream\fP\fB, const wchar_t *restrict\fP

\fIformat\fP\fB, ... );

.br

int swscanf(const wchar_t *restrict\fP \fIws\fP\fB,

.br

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

.br

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

.br

\fP

.SH DESCRIPTION

.LP

The \fIfwscanf\fP() function shall read from the named input \fIstream\fP.

The \fIwscanf\fP() function shall read from the

standard input stream \fIstdin\fP. The \fIswscanf\fP() function shall

read from the wide-character string \fIws\fP. Each

function reads wide characters, interprets them according to a format,

and stores the results in its arguments. Each expects, as

arguments, a control wide-character string \fIformat\fP described

below, and a set of \fIpointer\fP arguments indicating where

the converted input should be stored. The result is undefined if there

are insufficient arguments for the format. If the

\fIformat\fP is exhausted while arguments remain, the excess arguments

are evaluated but are otherwise ignored.

.LP

Conversions can be applied to the \fIn\fPth argument after the \fIformat\fP

in the argument list, rather than to the next unused

argument. In this case, the conversion specifier wide character \fB%\fP

(see below) is replaced by the sequence \fB"%n$"\fP ,

where \fIn\fP is a decimal integer in the range [1,{NL_ARGMAX}]. This

feature provides for the definition of \fIformat\fP

wide-character strings that select arguments in an order appropriate

to specific languages. In \fIformat\fP wide-character strings

containing the \fB"%\fP\fIn\fP\fB$"\fP form of conversion specifications,

it is unspecified whether numbered arguments in

the argument list can be referenced from the \fIformat\fP wide-character

string more than once.

.LP

The \fIformat\fP can contain either form of a conversion specification-that

is, \fB%\fP or \fB"%\fP\fIn\fP\fB$"\fP-

but the two forms cannot normally be mixed within a single \fIformat\fP

wide-character string. The only exception to this is that

\fB%%\fP or \fB%*\fP can be mixed with the \fB"%\fP\fIn\fP\fB$"\fP

form. When numbered argument specifications are

used, specifying the \fIN\fPth argument requires that all the leading

arguments, from the first to the ( \fIN\fP-1)th, are

pointers. 

.LP

The

\fIfwscanf\fP() function in all its forms allows for detection of

a language-dependent radix character in the input string,

encoded as a wide-character value. The radix character is defined

in the program's locale (category \fILC_NUMERIC ).\fP In the

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

the radix character shall default to a period ( \fB'.'\fP

). 

.LP

The \fIformat\fP is a wide-character string composed of zero or more

directives. Each directive is composed of one of the

following: one or more white-space wide characters ( <space>s, <tab>s,

<newline>s, <vertical-tab>s, or

<form-feed>s); an ordinary wide character (neither \fB'%'\fP nor a

white-space character); or a conversion specification.

Each conversion specification is introduced by a \fB'%'\fP   \ or

the sequence \fB"%\fP\fIn\fP\fB$"\fP  after which the following appear

in sequence:

.IP " *" 3

An optional assignment-suppressing character \fB'*'\fP .

.LP

.IP " *" 3

An optional non-zero decimal integer that specifies the maximum field

width.

.LP

.IP " *" 3

An optional length modifier that specifies the size of the receiving

object.

.LP

.IP " *" 3

A conversion specifier wide character that specifies the type of conversion

to be applied. The valid conversion specifiers are

described below.

.LP

.LP

The \fIfwscanf\fP() functions shall execute each directive of the

format in turn. If a directive fails, as detailed below, the

function shall return. Failures are described as input failures (due

to the unavailability of input bytes) or matching failures

(due to inappropriate input).

.LP

A directive composed of one or more white-space wide characters is

executed by reading input until no more valid input can be

read, or up to the first wide character which is not a white-space

wide character, which remains unread.

.LP

A directive that is an ordinary wide character shall be executed as

follows. The next wide character is read from the input and

compared with the wide character that comprises the directive; if

the comparison shows that they are not equivalent, the directive

shall fail, and the differing and subsequent wide characters remain

unread. Similarly, if end-of-file, an encoding error, or a read

error prevents a wide character from being read, the directive shall

fail.

.LP

A directive that is a conversion specification defines a set of matching

input sequences, as described below for each conversion

wide character. A conversion specification is executed in the following

steps.

.LP

Input white-space wide characters (as specified by \fIiswspace\fP()

) shall be skipped, unless the

conversion specification includes a \fB[\fP , \fBc\fP , or \fBn\fP

conversion specifier.

.LP

An item shall be read from the input, unless the conversion specification

includes an \fBn\fP conversion specifier wide

character. An input item is defined as the longest sequence of input

wide characters, not exceeding any specified field width,

which is an initial subsequence of a matching sequence. The first

wide character, if any, after the input item shall remain unread.

If the length of the input item is zero, the execution of the conversion

specification shall fail; this condition is a matching

failure, unless end-of-file, an encoding error, or a read error prevented

input from the stream, in which case it is an input

failure.

.LP

Except in the case of a \fB%\fP conversion specifier, the input item

(or, in the case of a \fB%n\fP conversion

specification, the count of input wide characters) shall be converted

to a type appropriate to the conversion wide character. If

the input item is not a matching sequence, the execution of the conversion

specification shall fail; this condition is a matching

failure. Unless assignment suppression was indicated by a \fB'*'\fP

, the result of the conversion shall be placed in the object

pointed to by the first argument following the \fIformat\fP argument

that has not already received a conversion result if the

conversion specification is introduced by \fB%\fP ,   \ or in the

\fIn\fPth argument if introduced by the wide-character

sequence \fB"%\fP\fIn\fP\fB$"\fP.  If this object does not

have an appropriate type, or if the result of the conversion cannot

be represented in the space provided, the behavior is

undefined.

.LP

The length modifiers and their meanings are:

.TP 7

\fBhh\fP

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP

conversion specifier applies to an argument with type pointer to \fBsigned

char\fP or \fBunsigned char\fP.

.TP 7

\fBh\fP

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP

conversion specifier applies to an argument with type pointer to \fBshort\fP

or \fBunsigned short\fP.

.TP 7

\fBl\fP\ (ell)

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP

conversion specifier applies to an argument with type pointer to \fBlong\fP

or \fBunsigned long\fP; that a following \fBa\fP ,

\fBA\fP , \fBe\fP , \fBE\fP , \fBf\fP , \fBF\fP , \fBg\fP , or \fBG\fP

conversion specifier applies to an

argument with type pointer to \fBdouble\fP; or that a following \fBc\fP

, \fBs\fP , or \fB[\fP conversion specifier

applies to an argument with type pointer to \fBwchar_t\fP.

.TP 7

\fBll\fP\ (ell-ell)

.sp

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP conversion

specifier applies to an argument with type pointer to \fBlong long\fP

or \fBunsigned long long\fP.

.TP 7

\fBj\fP

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP

conversion specifier applies to an argument with type pointer to \fBintmax_t\fP

or \fBuintmax_t\fP.

.TP 7

\fBz\fP

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP

conversion specifier applies to an argument with type pointer to \fBsize_t\fP

or the corresponding signed integer type.

.TP 7

\fBt\fP

Specifies that a following \fBd\fP , \fBi\fP , \fBo\fP , \fBu\fP ,

\fBx\fP , \fBX\fP , or \fBn\fP

conversion specifier applies to an argument with type pointer to \fBptrdiff_t\fP

or the corresponding \fBunsigned\fP type.

.TP 7

\fBL\fP

Specifies that a following \fBa\fP , \fBA\fP , \fBe\fP , \fBE\fP ,

\fBf\fP , \fBF\fP , \fBg\fP , or

\fBG\fP conversion specifier applies to an argument with type pointer

to \fBlong double\fP.

.sp

.LP

If a length modifier appears with any conversion specifier other than

as specified above, the behavior is undefined.

.LP

The following conversion specifier wide characters are valid:

.TP 7

\fBd\fP

Matches an optionally signed decimal integer, whose format is the

same as expected for the subject sequence of \fIwcstol\fP() with the

value 10 for the \fIbase\fP argument. In the absence of a size modifier,

the application shall ensure that the corresponding argument is a

pointer to \fBint\fP.

.TP 7

\fBi\fP

Matches an optionally signed integer, whose format is the same as

expected for the subject sequence of \fIwcstol\fP() with 0 for the

\fIbase\fP argument. In the absence of a size modifier, the

application shall ensure that the corresponding argument is a pointer

to \fBint\fP.

.TP 7

\fBo\fP

Matches an optionally signed octal integer, whose format is the same

as expected for the subject sequence of \fIwcstoul\fP() with the value

8 for the \fIbase\fP argument. In the absence of a size modifier,

the application shall ensure that the corresponding argument is a

pointer to \fBunsigned\fP.

.TP 7

\fBu\fP

Matches an optionally signed decimal integer, whose format is the

same as expected for the subject sequence of \fIwcstoul\fP() with

the value 10 for the \fIbase\fP argument. In the absence of a size

modifier,

the application shall ensure that the corresponding argument is a

pointer to \fBunsigned\fP.

.TP 7

\fBx\fP

Matches an optionally signed hexadecimal integer, whose format is

the same as expected for the subject sequence of \fIwcstoul\fP() with

the value 16 for the \fIbase\fP argument. In the absence of a size

modifier,

the application shall ensure that the corresponding argument is a

pointer to \fBunsigned\fP.

.TP 7

\fBa\fP,\ \fBe\fP,\ \fBf\fP,\ \fBg\fP

.sp

Matches an optionally signed floating-point number, infinity, or NaN

whose format is the same as expected for the subject sequence

of \fIwcstod\fP(). In the absence of a size modifier, the application

shall ensure that the

corresponding argument is a pointer to \fBfloat\fP. 

.LP

If the \fIfwprintf\fP() family of functions generates character string

representations

for infinity and NaN (a symbolic entity encoded in floating-point

format) to support IEEE\ Std\ 754-1985, the

\fIfwscanf\fP() family of functions shall recognize them as input.

.TP 7

\fBs\fP

Matches a sequence of non white-space wide characters. If no \fBl\fP

(ell) qualifier is present, characters from the input

field shall be converted as if by repeated calls to the \fIwcrtomb\fP()

function, with the

conversion state described by an \fBmbstate_t\fP object initialized

to zero before the first wide character is converted. The

application shall ensure that the corresponding argument is a pointer

to a character array large enough to accept the sequence and

the terminating null character, which shall be added automatically.

.LP

Otherwise, the application shall ensure that the corresponding argument

is a pointer to an array of \fBwchar_t\fP large enough

to accept the sequence and the terminating null wide character, which

shall be added automatically.

.TP 7

\fB[\fP

Matches a non-empty sequence of wide characters from a set of expected

wide characters (the \fIscanset\fP). If no \fBl\fP

(ell) qualifier is present, wide characters from the input field shall

be converted as if by repeated calls to the \fIwcrtomb\fP() function,

with the conversion state described by an \fBmbstate_t\fP object

initialized to zero before the first wide character is converted.

The application shall ensure that the corresponding argument is a

pointer to a character array large enough to accept the sequence and

the terminating null character, which shall be added

automatically. 

.LP

If an \fBl\fP (ell) qualifier is present, the application shall ensure

that the corresponding argument is a pointer to an

array of \fBwchar_t\fP large enough to accept the sequence and the

terminating null wide character, which shall be added

automatically.

.LP

The conversion specification includes all subsequent wide characters

in the \fIformat\fP string up to and including the

matching right square bracket ( \fB']'\fP ). The wide characters between

the square brackets (the \fIscanlist\fP) comprise the

scanset, unless the wide character after the left square bracket is

a circumflex ( \fB'^'\fP ), in which case the scanset

contains all wide characters that do not appear in the scanlist between

the circumflex and the right square bracket. If the

conversion specification begins with \fB"[]"\fP or \fB"[^]"\fP , the

right square bracket is included in the scanlist and the

next right square bracket is the matching right square bracket that

ends the conversion specification; otherwise, the first right

square bracket is the one that ends the conversion specification.

If a \fB'-'\fP is in the scanlist and is not the first wide

character, nor the second where the first wide character is a \fB'^'\fP

, nor the last wide character, the behavior is

implementation-defined.

.TP 7

\fBc\fP

Matches a sequence of wide characters of exactly the number specified

by the field width (1 if no field width is present in the

conversion specification). 

.LP

If no \fBl\fP (ell) length modifier is present, characters from the

input field shall be converted as if by repeated calls to

the \fIwcrtomb\fP() function, with the conversion state described

by an \fBmbstate_t\fP

object initialized to zero before the first wide character is converted.

The corresponding argument shall be a pointer to the

initial element of a character array large enough to accept the sequence.

No null character is added.

.LP

If an \fBl\fP (ell) length modifier is present, the corresponding

argument shall be a pointer to the initial element of an

array of \fBwchar_t\fP large enough to accept the sequence. No null

wide character is added.

.LP

Otherwise, the application shall ensure that the corresponding argument

is a pointer to an array of \fBwchar_t\fP large enough

to accept the sequence. No null wide character is added.

.TP 7

\fBp\fP

Matches an implementation-defined set of sequences, which shall be

the same as the set of sequences that is produced by the

\fB%p\fP conversion specification of the corresponding \fIfwprintf\fP()

functions. The

application shall ensure that the corresponding argument is a pointer

to a pointer to \fBvoid\fP. The interpretation of the input

item is implementation-defined. If the input item is a value converted

earlier during the same program execution, the pointer that

results shall compare equal to that value; otherwise, the behavior

of the \fB%p\fP conversion is undefined.

.TP 7

\fBn\fP

No input is consumed. The application shall ensure that the corresponding

argument is a pointer to the integer into which is to

be written the number of wide characters read from the input so far

by this call to the \fIfwscanf\fP() functions. Execution of a

\fB%n\fP conversion specification shall not increment the assignment

count returned at the completion of execution of the

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

If the conversion specification includes an

assignment-suppressing wide character or a field width, the behavior

is undefined.

.TP 7

\fBC\fP

Equivalent to \fBlc\fP . 

.TP 7

\fBS\fP

Equivalent to \fBls\fP . 

.TP 7

\fB%\fP

Matches a single \fB'%'\fP wide character; no conversion or assignment

shall occur. The complete conversion specification

shall be \fB%%\fP .

.sp

.LP

If a conversion specification is invalid, the behavior is undefined.

.LP

The conversion specifiers \fBA\fP , \fBE\fP , \fBF\fP , \fBG\fP ,

and \fBX\fP are also valid and shall be

equivalent to, respectively, \fBa\fP , \fBe\fP , \fBf\fP , \fBg\fP

, and \fBx\fP .

.LP

If end-of-file is encountered during input, conversion is terminated.

If end-of-file occurs before any wide characters matching

the current conversion specification (except for \fB%n\fP ) have been

read (other than leading white-space, where permitted),

execution of the current conversion specification shall terminate

with an input failure. Otherwise, unless execution of the current

conversion specification is terminated with a matching failure, execution

of the following conversion specification (if any) shall

be terminated with an input failure.

.LP

Reaching the end of the string in \fIswscanf\fP() shall be equivalent

to encountering end-of-file for \fIfwscanf\fP().

.LP

If conversion terminates on a conflicting input, the offending input

shall be left unread in the input. Any trailing white space

(including <newline>) shall be left unread unless matched by a conversion

specification. The success of literal matches and

suppressed assignments is only directly determinable via the \fB%n\fP

conversion specification.

.LP

The

\fIfwscanf\fP() and \fIwscanf\fP() functions may mark the \fIst_atime\fP

field of the file associated with \fIstream\fP for

update. The \fIst_atime\fP field shall be marked for update by the

first successful execution of \fIfgetc\fP(), \fIfgetwc\fP(), \fIfgets\fP(),

\fIfgetws\fP(), \fIfread\fP(), \fIgetc\fP(), \fIgetwc\fP(), \fIgetchar\fP(),

\fIgetwchar\fP(), \fIgets\fP(), \fIfscanf\fP(), or \fIfwscanf\fP()

using \fIstream\fP that returns data not supplied by a prior

call to \fIungetc\fP(). 

.SH RETURN VALUE

.LP

Upon successful completion, these functions shall return the number

of successfully matched and assigned input items; this

number can be zero in the event of an early matching failure. If the

input ends before the first matching failure or conversion,

EOF shall be returned. If a read error occurs, the error indicator

for the stream is set, EOF shall be returned,   \ and

\fIerrno\fP shall be set to indicate the error. 

.SH ERRORS

.LP

For the conditions under which the \fIfwscanf\fP() functions shall

fail and may fail, refer to \fIfgetwc\fP() .

.LP

In addition, \fIfwscanf\fP() may fail if:

.TP 7

.B EILSEQ

Input byte sequence does not form a valid character. 

.TP 7

.B EINVAL

There are insufficient arguments. 

.sp

.LP

\fIThe following sections are informative.\fP

.SH EXAMPLES

.LP

The call:

.sp

.RS

.nf

\fBint i, n; float x; char name[50];

n = wscanf(L"%d%f%s", &i, &x, name);

\fP

.fi

.RE

.LP

with the input line:

.sp

.RS

.nf

\fB25 54.32E-1 Hamster

\fP

.fi

.RE

.LP

assigns to \fIn\fP the value 3, to \fIi\fP the value 25, to \fIx\fP

the value 5.432, and \fIname\fP contains the string

\fB"Hamster"\fP .

.LP

The call:

.sp

.RS

.nf

\fBint i; float x; char name[50];

(void) wscanf(L"%2d%f%*d %[0123456789]", &i, &x, name);

\fP

.fi

.RE

.LP

with input:

.sp

.RS

.nf

\fB56789 0123 56a72

\fP

.fi

.RE

.LP

assigns 56 to \fIi\fP, 789.0 to \fIx\fP, skips 0123, and places the

string \fB"56\\0"\fP in \fIname\fP. The next call to \fIgetchar\fP()

shall return the character \fB'a'\fP .

.SH APPLICATION USAGE

.LP

In format strings containing the \fB'%'\fP form of conversion specifications,

each argument in the argument list is used

exactly once.

.SH RATIONALE

.LP

None.

.SH FUTURE DIRECTIONS

.LP

None.

.SH SEE ALSO

.LP

\fIgetwc\fP() , \fIfwprintf\fP() , \fIsetlocale\fP() , \fIwcstod\fP()

, \fIwcstol\fP() ,

\fIwcstoul\fP() , \fIwcrtomb\fP() , the Base Definitions volume of

IEEE\ Std\ 1003.1-2001, Chapter 7, Locale, \fI<langinfo.h>\fP, \fI<stdio.h>\fP,

\fI<wchar.h>\fP

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group. In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.opengroup.org/unix/online.html .