fwscanf(3C) Standard C Library Functions fwscanf(3C)
NAME
fwscanf, wscanf, swscanf, vfwscanf, vwscanf, vswscanf - convert formatted wide-character input
SYNOPSIS
#include <stdio.h>
#include <wchar.h>
int fwscanf(FILE *restrict stream, const wchar_t *restrict format, ...);
int wscanf(const wchar_t *restrict format, ...);
int swscanf(const wchar_t *restrict s, const wchar_t *restrict format,
...);
#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>
int vfwscanf(FILE *restrict stream, const wchar_t *restrict format,
va_list arg);
int vswcanf(const wchar_t *restrict ws, const wchar_t *restrict format,
va_list arg);
int vwscanf(const wchar_t *restrict 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(), vswscanf(), and vwscanf() functions are equivalent to the fwscanf(), swscanf(), and wscanf() functions, 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 . 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 according to a format, and stores the results in its arguments. Each expects, as argu-
ments, a control wide-character string format described below, and a set of pointer arguments indicating 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$, where n is a decimal integer in the range [1,
NL_ARGMAX]. This feature provides for the definition of format wide-character strings that select arguments in an order appropriate to spe-
cific languages. In format wide-character strings containing the %n$ 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 specification, 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 character); or a conversion specification. Each conversion specification 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 option length modifier that specifies the size of the receiving object.
o A conversion specifier 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 function 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 subsequent 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 specification includes a [, c, or n
conversion character.
An item is read from the input unless the conversion specification 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 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-char-
acters 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 func-
tions 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 specification, 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 conversion specification is introduced by %, or in the nth argument 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 pro-
vided, 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
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 wchar_t.
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 intmax_t
or uintmax_t.
z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies to an argument with type pointer to size_t
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
ptrdiff_t 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 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 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 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.
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 hexa-
decimal 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.
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 ini-
tialized 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 wchar_t large enough to accept the sequence and the ter-
minating 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 conver-
sion 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 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 wchar_t large enough to accept
the sequence and the terminating null wide-character, which will be added automatically.
The conversion specification includes all subsequent 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-charac-
ter 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 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 conver-
sion 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 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 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 con-
verted earlier during the same program 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.
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 conver-
sion specification terminates 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) 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 offending input is left unread in the input. Any trailing white space (including new-
line) 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 successful 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 in name. The next call to getchar(3C) will return the character a.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE 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), attributes(5), standards(5)
NOTES
The behavior of the conversion specifier "%%" has changed for all of the functions described on this manual page. Previously the "%%" spec-
ifier 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 the old behavior is desired, the conversion specification "%*[%]" can be used.
SunOS 5.11 10 Jul 2008 fwscanf(3C)