swscanf(3C)
NAME
fwscanf, wscanf, swscanf, vfwscanf, vwscanf, vswscanf - con-
vert formatted wide-character input
SYNOPSIS
#include <stdio.h>
#include <wchar.h>
int fwscanf(FILE *stream, const wchar_t *format, ...);
int wscanf(const wchar_t *format, ...);
int swscanf(const wchar_t *s, const wchar_t *format, ...);
#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>
int vfwscanf(FILE *stream, const wchar_t *format, va_list
arg);
int vswcanf(const wchar_t *ws, const wchar_t *format,
va_list arg);
int vswscanf(const wchar_t *format, va_list 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(), vswcanf(), and vswcanf() 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 <stdarg.h> header (see
stdarg(3HEAD)). These functions do not invoke the va_end()
macro. Applications using these functions should call
va_end(ap) afterwards to 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$, where n is a decimal
integer in the range [1, NL_ARGMAX]. This feature provides
for the definition of format wide-character strings that
select arguments in an order appropriate to specific
languages. In format wide-character strings containing the
%n$ 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 LC_NUMERIC). 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:
o An optional assignment-suppressing character *.
o An optional non-zero decimal integer that specifies
the maximum field width.
o An optional size modifier h , l(ell), or L indicating
the size of the receiving object. The conversion
wide-characters c, s, and [ must be precede by l (ell)
if the corresponding argument is a pointer to wchar_t
rather than a pointer to a character type. The conver-
sion wide-characters d, i, and n must be preceded by h
if the corresponding argument is a pointer to short
int rather than a pointer to int, or by l (ell) if it
is a pointer to long int. Similarly, the conversion
wide-characters o, u, and x must be preceded by h if
the corresponding argument is a pointer to unsigned
short int rather than a pointer to unsigned int, or by
l (ell) if it is a pointer to unsigned long int. The
conversion wide-characters e, f, and g must be pre-
ceded by l (ell) if the corresponding argument is a
pointer to double rather than a pointer to float, or
by L if it is a pointer to long double. If an h, l
(ell), or L appears with any other conversion wide-
character, the behavior is undefined.
o A conversion wide-character that specifies 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
specification includes an n conversion 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 remains
unread. If the length of the input item is 0, the execution
of the conversion specification 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 following conversion wide-characters are valid:
d Matches an optionally signed decimal integer, whose
format is the same as expected for the subject
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.
i Matches an optionally signed integer, whose format is
the same as expected for the subject sequence of
wcstol(3C) with 0 for the base argument. In the
absence of a size modifier, the corresponding argument
must be a pointer to int.
o Matches an optionally signed octal integer, whose for-
mat 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 subject
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 subject
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.
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.
If the fwprintf() family of functions generates char-
acter string representations for infinity and NaN (a
7858 symbolic entity encoded in floating-point format)
to support the ANSI/IEEE Std 754:1985 standard, the
fwscanf() family of functions will recognize them as
input.
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 mbstate_t object initialized to zero
before the first wide-character is converted. The
corresponding argument must be a pointer to a charac-
ter 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 wchar_t large enough to accept
the sequence and the terminating null wide-character,
which will be added automatically.
[ Matches a non-empty sequence of wide-characters from a
set of expected wide-characters (the scanset). 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 mbstate_t object initialized to zero
before the first wide-character is converted. The
corresponding argument must be a pointer to a charac-
ter 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 wchar_t
large enough to accept the sequence and the terminat-
ing null wide-character, which will be added automat-
ically.
The conversion specification includes all subsequent
widw characters in the format string up to and includ-
ing 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 specifica-
tion 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 specification; otherwise the first
right square bracket is the one that ends the conver-
sion 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 charac-
ters 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 specification). 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 mbstate_t object initialized to zero
before the first wide-character is converted. The
corresponding argument must be a pointer to a charac-
ter array large enough to accept the sequence. No
null character is added.
Otherwise, the corresponding argument must be a
pointer to an array of wchar_t 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 ear-
lier during the same program execution, the pointer
that results will compare equal to that value; other-
wise 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 writ-
ten the number of wide-characters read from the input
so far by this call to the fwscanf() functions. Execu-
tion of a %n conversion specification does not incre-
ment the assignment count returned at the completion
of execution of the function.
C Same as lc.
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 E, G, and X are also valid and
behave the same as, respectively, e, 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 st_atime
field of the file associated with stream for update. The
st_atime 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
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.
ERRORS
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 character.
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.
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.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
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), wcrtomb(3C),
wcstod(3C), wcstol(3C), wcstoul(3C), attributes(5), stan-
dards(5)
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