Standard C Library Functions fwscanf(3C)
NAME
fwscanf, wscanf, swscanf, vfwscanf, vwscanf, vswscanf - con-
vert formatted wide-character input
SYNOPSIS
#include
#include
int fwscanf(FILE *restrict stream, const wchart *restrict format, ...);
int wscanf(const wchart *restrict format, ...);
int swscanf(const wchart *restrict s, const wchart *restrict format,
...);
#include
#include
#include
int vfwscanf(FILE *restrict stream, const wchart *restrict format,
valist arg);
int vswcanf(const wchart *restrict ws, const wchart *restrict format,
valist arg);
int vwscanf(const wchart *restrict format, valist arg);
DESCRIPTION
The fwscanf() function reads from the named input stream.
The wscanf() function reads from the standard input stream
stdin.
The swscanf() function reads from the wide-character string
s.
The vfwscanf(), vswscanf(), and vwscanf() functions are
equivalent to the fwscanf(), swscanf(), and wscanf() func-
tions, respectively, except that instead of being called
with a variable number of arguments, they are called with an
argument list as defined by the header . These
functions do not invoke the vaend() macro. Applications
using these functions should call vaend(ap) afterwards to
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Standard C Library Functions fwscanf(3C)
clean up.
Each function reads wide-characters, interprets them accord-
ing to a format, and stores the results in its arguments.
Each expects, as arguments, a control wide-character string
format described below, and a set of pointer arguments indi-
cating where the converted input should be stored. The
result is 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$, where n is a decimal
integer in the range [1, NLARGMAX]. This feature provides
for the definition of format wide-character strings that
select arguments in an order appropriate to specific
languages. In format wide-character strings containing the
%n$ form of conversion specifications, it is unspecified
whether numbered arguments in the argument list can be
referenced from the format wide-character string more than
once.
The format can contain either form of a conversion specifi-
cation, that is, % or %n$, but the two forms cannot normally
be mixed within a single format wide-character string. The
only exception to this is that %% or %* can be mixed with
the %n$ form.
The fwscanf() 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 LCNUMERIC). In
the POSIX locale, or in a locale where the radix character
is not defined, the radix character defaults to a period
(.).
The format 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,
tab, newline, vertical-tab or form-feed characters); an
ordinary wide-character (neither % nor a white-space charac-
ter); or a conversion specification. Each conversion specif-
ication is introduced by a % or the sequence %n$ after which
the following appear in sequence:
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Standard C Library Functions fwscanf(3C)
o An optional assignment-suppressing character *.
o An optional non-zero decimal integer that specifies
the maximum field width.
o An option length modifier that specifies the size
of the receiving object.
o A conversion specifier wide-character that speci-
fies the type of conversion to be applied. The
valid conversion wide-characters are described
below.
The fwscanf() functions execute each directive of the format
in turn. If a directive fails, as detailed below, the func-
tion returns. Failures are described as input failures (due
to the unavailability of input bytes) or matching failures
(due to inappropriate input).
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.
A directive that is an ordinary wide-character is 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 fails, and the differing and sub-
sequent wide-characters remain unread.
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:
Input white-space wide-characters (as specified by
iswspace(3C)) are skipped, unless the conversion specifica-
tion includes a [, c, or n conversion character.
An item is read from the input unless the conversion specif-
ication includes an n conversion wide-character. The length
of the item read is limited to any specified maximum field
width. In Solaris default mode, the input item is defined as
the longest sequence of input wide-characters that forms a
matching sequence. In some cases, fwscanf() might need to
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Standard C Library Functions fwscanf(3C)
read several extra wide-characters beyond the end of the
input item to find the end of a matching sequence. In
C99/SUSv3 mode, the input item is defined as the longest
sequence of input wide-characters that is, or is a prefix
of, a matching sequence. With this definition, fwscanf()
need only read at most one wide-character beyond the end of
the input item. Therefore, in C99/SUSv3 mode, some sequences
that are acceptable to wcstod(3C), wcstol(3C), and similar
functions are unacceptable to fwscanf(). In either mode,
fwscanf() attempts to push back any excess bytes read using
ungetc(3C). Assuming all such attempts succeed, the first
wide-character, if any, after the input item remains unread.
If the length of the input item is 0, the conversion fails.
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.
Except in the case of a % conversion wide-character, the
input item (or, in the case of a %n conversion specifica-
tion, the count of input wide-characters) is 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 fails; this condition is a matching
failure. Unless assignment suppression was indicated by a *,
the result of the conversion is placed in the object pointed
to by the first argument following the format argument that
has not already received a conversion result if the conver-
sion specification is introduced by %, or in the nth argu-
ment if introduced by the wide-character sequence %n$. 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.
The length modifiers and their meanings are:
hh Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to signed char or
unsigned char.
h Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to short or
unsigned short.
l (ell) Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to long or
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Standard C Library Functions fwscanf(3C)
unsigned long; that a following a, A, e, E,
f, F, g, or G conversion specifier applies
to an argument with type pointer to double;
or that a following c, s, or [ conversion
specifier applies to an argument with type
pointer to wchart.
ll (ell-ell) Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to long long or
unsigned long long.
j Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to intmaxt or
uintmaxt.
z Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to sizet or the
corresponding signed integer type.
t Specifies that a following d, i, o, u, x, X,
or n conversion specifier applies to an
argument with type pointer to ptrdifft or
the corresponding unsigned type.
L Specifies that a following a, A, e, E, f, F,
g, or G conversion specifier applies to an
argument with type pointer to long double.
If a length modifier appears with any conversion specifier
other than as specified above, the behavior is undefined.
The following conversion wide-characters are valid:
d Matches an optionally signed decimal integer,
whose format is the same as expected for the sub-
ject sequence of wcstol(3C) with the value 10 for
the base argument. In the absence of a size
modifier, the corresponding argument must be a
pointer to int.
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Standard C Library Functions fwscanf(3C)
i Matches an optionally signed integer, whose for-
mat is the same as expected for the subject
sequence of wcstol(3C) with 0 for the base argu-
ment. In the absence of a size modifier, the
corresponding argument must be a pointer to int.
o Matches an optionally signed octal integer, whose
format is the same as expected for the subject
sequence of wcstoul(3C) with the value 8 for the
base argument. In the absence of a size modifier,
the corresponding argument must be a pointer to
unsigned int.
u Matches an optionally signed decimal integer,
whose format is the same as expected for the sub-
ject sequence of wcstoul(3C) with the value 10
for the base argument. In the absence of a size
modifier, the corresponding argument must be a
pointer to unsigned int.
x Matches an optionally signed hexadecimal integer,
whose format is the same as expected for the sub-
ject sequence of wcstoul(3C) with the value 16
for the base argument. In the absence of a size
modifier, the corresponding argument must be a
pointer to unsigned int.
a,e,f,g Matches an optionally signed floating-point
number, whose format is the same as expected for
the subject sequence of wcstod(3C). In the
absence of a size modifier, the corresponding
argument must be a pointer to float. The e, f,
and g specifiers match hexadecimal floating point
values only in C99/SUSv3 (see standards(5)) mode,
but the a specifier always matches hexadecimal
floating point values.
These conversion specifiers match any subject
sequence accepted by strtod(3C), including the
INF, INFINITY, NAN, and NAN(n-char-sequence)
forms. The result of the conversion is the same
as that of calling strtod() (or strtof() or
strtold()) with the matching sequence, including
the raising of floating point exceptions and the
setting of errno to ERANGE, if applicable.
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Standard C Library Functions fwscanf(3C)
s Matches a sequence of non white-space wide-
characters. If no l (ell) qualifier is present,
characters from the input field are converted as
if by repeated calls to the wcrtomb(3C) function,
with the conversion state described by an
mbstatet object initialized to zero before the
first wide-character is converted. The
corresponding argument must be a pointer to a
character array large enough to accept the
sequence and the terminating null character,
which will be added automatically.
Otherwise, the corresponding argument must be a
pointer to an array of wchart large enough to
accept the sequence and the terminating null
wide-character, which will be added automati-
cally.
[ Matches a non-empty sequence of wide-characters
from a set of expected wide-characters (the scan-
set). If no l (ell) qualifier is present, wide-
characters from the input field are converted as
if by repeated calls to the wcrtomb() function,
with the conversion state described by an
mbstatet object initialized to zero before the
first wide-character is converted. The
corresponding argument must be a pointer to a
character array large enough to accept the
sequence and the terminating null character,
which will be added automatically.
If an l (ell) qualifier is present, the
corresponding argument must be a pointer to an
array of wchart large enough to accept the
sequence and the terminating null wide-
character, which will be added automatically.
The conversion specification includes all subse-
quent widw characters in the format string up to
and including the matching right square bracket
(]). The wide-characters between the square
brackets (the scanlist) comprise the scanset,
unless the wide-character after the left square
bracket is a circumflex (^), 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 [] or [^], 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
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Standard C Library Functions fwscanf(3C)
specification; otherwise the first right square
bracket is the one that ends the conversion
specification. If a minus-sign (-) is in the
scanlist and is not the first wide-character, nor
the second where the first wide-character is a ^,
nor the last wide-character, it indicates a range
of characters to be matched.
c Matches a sequence of wide-characters of the
number specified by the field width (1 if no
field width is present in the conversion specifi-
cation). If no l (ell) qualifier is present,
wide-characters from the input field are con-
verted as if by repeated calls to the wcrtomb()
function, with the conversion state described by
an mbstatet object initialized to zero before
the first wide-character is converted. The
corresponding argument must be a pointer to a
character array large enough to accept the
sequence. No null character is added.
Otherwise, the corresponding argument must be a
pointer to an array of wchart large enough to
accept the sequence. No null wide-character is
added.
p Matches the set of sequences that is the same as
the set of sequences that is produced by the %p
conversion of the corresponding fwprintf(3C)
functions. The corresponding argument must be a
pointer to a pointer to void. If the input item
is a value converted earlier during the same pro-
gram execution, the pointer that results will
compare equal to that value; otherwise the
behavior of the %p conversion is undefined.
n No input is consumed. The corresponding argument
must be 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
fwscanf() functions. Execution of a %n conversion
specification does not increment the assignment
count returned at the completion of execution of
the function.
C Same as lc.
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Standard C Library Functions fwscanf(3C)
S Same as ls.
% Matches a single %; no conversion or assignment
occurs. The complete conversion specification
must be %%.
If a conversion specification is invalid, the behavior is
undefined.
The conversion characters A, E, F, G, and X are also valid
and behave the same as, respectively, a, e, f, g, and x.
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
%n) have been read (other than leading white-space, where
permitted), execution of the current conversion specifica-
tion terminates with an input failure. Otherwise, unless
execution of the current conversion specification is ter-
minated with a matching failure, execution of the following
conversion specification (if any) is terminated with an
input failure.
Reaching the end of the string in swscanf() is equivalent to
encountering end-of-file for fwscanf().
If conversion terminates on a conflicting input, the offend-
ing input is left unread in the input. Any trailing white
space (including newline) is left unread unless matched by a
conversion specification. The success of literal matches and
suppressed assignments is only directly determinable via the
%n conversion specification.
The fwscanf() and wscanf() functions may mark the statime
field of the file associated with stream for update. The
statime field will be marked for update by the first suc-
cessful execution of fgetc(3C), fgetwc(3C), fgets(3C),
fgetws(3C), fread(3C), getc(3C), getwc(3C), getchar(3C),
getwchar(3C), gets(3C), fscanf(3C) or fwscanf() using stream
that returns data not supplied by a prior call to
ungetc(3C).
RETURN VALUES
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Standard C Library Functions fwscanf(3C)
Upon successful completion, these functions return the
number of successfully matched and assigned input items;
this number can be 0 in the event of an early matching
failure. If the input ends before the first matching
failure or conversion, EOF is returned. If a read error
occurs the error indicator for the stream is set, EOF is
returned, and errno is set to indicate the error.
ERORS
For the conditions under which the fwscanf() functions will
fail and may fail, refer to fgetwc(3C).
In addition, fwscanf() may fail if:
EILSEQ Input byte sequence does not form a valid charac-
ter.
EINVAL There are insufficient arguments.
USAGE
In format strings containing the % form of conversion
specifications, each argument in the argument list is used
exactly once.
EXAMPLES
Example 1 wscanf() example
The call:
int i, n; float x; char name[50];
n = wscanf(L"%d%f%s", &i, &x, name);
with the input line:
25 54.32E-1 Hamster
will assign to n the value 3, to i the value 25, to x the
value 5.432, and name will contain the string Hamster.
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Standard C Library Functions fwscanf(3C)
The call:
int i; float x; char name[50];
(void) wscanf(L"%2d%f%*d %[0123456789], &i, &x, name);
with input:
56789 0123 56a72
will assign 56 to i, 789.0 to x, skip 0123, and place the
string 56\0 in name. The next call to getchar(3C) will
return the character a.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability Committed
MT-Level MT-Safe
Standard See standards(5).
SEE ALSO
fgetc(3C), fgets(3C), fgetwc(3C), fgetws(3C), fread(3C),
fscanf(3C), fwprintf(3C), getc(3C), getchar(3C), gets(3C),
getwc(3C), getwchar(3C), setlocale(3C), strtod(3C),
wcrtomb(3C), wcstod(3C), wcstol(3C), wcstoul(3C), attri-
butes(5), standards(5)
NOTES
The behavior of the conversion specifier "%%" has changed
for all of the functions described on this manual page. Pre-
viously the "%%" specifier accepted a "%" character from
input only if there were no preceding whitespace characters.
The new behavior accepts "%" even if there are preceding
whitespace characters. This new behavior now aligns with the
description on this manual page and in various standards. If
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Standard C Library Functions fwscanf(3C)
the old behavior is desired, the conversion specification
"%*[%]" can be used.
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