illumos: manual page: swscanf.3c

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
arguments, 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$,
where n is a decimal integer in the range [1, NL_ARGMAX]. This feature
provides for the definition of format wide-character strings that select
arguments in an order appropriate to specific languages. In format wide-
character strings containing the %n$ 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 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-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 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 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 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 hexadecimal floating point values only
in C99/SUSv3 (see standards(7)) 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 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 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
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-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
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 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 converted 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
conversion 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 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 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\0 in
name. The next call to getchar(3C) will return the character a.

ATTRIBUTES

NOTES

The behavior of the conversion specifier "%%" has changed for all of the
functions described on this manual page. Previously 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 the old
behavior is desired, the conversion specification "%*[%]" can be used.

July 10, 2008 FWSCANF(3C)