fwscanf(3C)fwscanf(3C)NAMEfwscanf(), wscanf(), swscanf() - convert formatted wide-character
input
SYNOPSISDESCRIPTION
The function reads from the named input stream.
The function reads from the standard input stream The reads from the
wide-character string s.
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
where n is a decimal integer in the range 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 form of conversion specifications, it is unspec‐
ified 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 but the two forms cannot normally be mixed within a single for‐
mat wide-character string. The only exception to this is that or can
be mixed with the form.
The function in all its forms allows for detection of a language-depen‐
dent radix character in the input string, encoded as a wide-character
value. The radix character is defined in the program's locale (cate‐
gory 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 direc‐
tives. 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 specification is introduced by a or the sequence after
which the following appear in sequence:
· An optional assignment-suppressing character
· An optional non-zero decimal integer that specifies the maxi‐
mum field width.
· An optional size modifier or indicating the size of the
receiving object.
The conversion wide-characters and must be precede by (ell)
if the corresponding argument is a pointer to rather than a
pointer to a character type.
The conversion wide-characters and must be preceded by if the
corresponding argument is a pointer to short int rather than
a pointer to int, or by if it is a pointer to signed char, or
by if it is a pointer to intmax_t, or by (ell) if it is a
pointer to long int, or by (ell-ell) if it is a pointer to
long long, or by if it is a pointer to ptrdiff_t, or by if it
is a pointer to ssize_t.
Similarly, the conversion wide-characters and must be pre‐
ceded by if the corresponding argument is a pointer to
unsigned short int rather than a pointer to unsigned int, or
by if it is a pointer to unsigned char, or by if it is a
pointer to uintmax_t, or by (ell) if it is a pointer to
unsigned long int, or by (ell-ell) if it is a pointer to
unsigned long long, or by if it is a pointer to unsigned
ptrdiff_t, or by if it is a pointer to size_t.
The conversion wide-characters and must be preceded by (ell)
if the corresponding argument is a pointer to double rather
than a pointer to float, or by if it is a pointer to long
double. If an or appears with any other conversion wide-
character, the behavior is undefined.
· For Itanium(R)-based systems if the optional decimal floating
point feature is installed and enabled, the following
optional character specifications are allowed:
An optional specifying that a following or conversion speci‐
fier applies to an argument with type pointer to
An optional specifying that a following or conversion speci‐
fier applies to an argument with type pointer to
An optional specifying that a following or conversion speci‐
fier applies to an argument with type pointer to
The behavior of the or conversion specifiers for decimal
floating point numbers is the same as for double except hexa‐
decimal floating-point input is not accepted.
· A conversion wide-character that specifies the type of con‐
version to be applied. The valid conversion wide-characters
are described below.
The 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 exe‐
cuted 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 match‐
ing input sequences, as described below for each conversion wide-char‐
acter. A conversion specification is executed in the following steps:
Input white-space wide-characters (as specified by are skipped, unless
the conversion specification includes a or n conversion character.
An item is read from the input, unless the conversion specification
includes an 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 conver‐
sion 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 specifica‐
tion 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 con‐
version specification is introduced by or in the nth argument if intro‐
duced by the wide-character sequence If this object does not have an
appropriate type, or if the result of the conversion cannot be repre‐
sented in the space provided, the behavior is undefined.
The following conversion wide-characters are valid:
Matches an optionally signed decimal integer, whose format is
the same
as expected for the subject sequence of with the value
10 for the base argument. In the absence of a size
modifier, the corresponding argument must be a pointer
to int.
Matches an optionally signed integer, whose format is the same
as expected for
the subject sequence of with 0 for the base argument.
In the absence of a size modifier, the corresponding
argument must be a pointer to int.
Matches an optionally signed octal integer, whose format is the
same as
expected for the subject sequence of with the value 8
for the base argument. In the absence of a size modi‐
fier, the corresponding argument must be a pointer to
unsigned int.
Matches an optionally signed decimal integer, whose format is
the same as expected for the subject sequence of 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.
Matches an optionally signed hexadecimal integer, whose format
is
the same as expected for the subject sequence of 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.
Matches an optionally signed floating-point number,
whose format is the same as expected for the subject
sequence of In the absence of a size modifier, the
corresponding argument must be a pointer to float.
If the family of functions generates character 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 family of
functions will recognize them as input.
Matches a sequence of non white-space wide-characters.
If no (ell) qualifier is present, characters from the
input field are converted as if by repeated calls to
the function, with the conversion state described by
an 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 charac‐
ter, which will be added automatically.
Otherwise, the corresponding argument must be a pointer to an array of
large enough to accept the sequence and the terminating null wide-char‐
acter, which will be added automatically.
Matches a non-empty sequence of wide-characters from
a set of expected wide-characters (the scanset). If
no (ell) qualifier is present, wide-characters from
the input field are converted as if by repeated calls
to the function, with the conversion state described
by an object initialized to zero before the first
wide-character is converted. The corresponding argu‐
ment 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 (ell) qualifier is present, the corresponding argument must be a
pointer to an array of large enough to accept the sequence and the ter‐
minating null wide-character, which will be added automatically.
The conversion specification includes all subsequent wide characters in
the format string up to and including the matching right square bracket
( The wide-characters between the square brackets (the scanlist) com‐
prise 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 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, the behavior
is implementation-dependent.
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 (ell) qualifier is
present, wide-characters from the input field are con‐
verted as if by repeated calls to the function, with
the conversion state described by an object initial‐
ized to zero before the first wide-character is con‐
verted. 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 large enough to accept the sequence. No null wide-
character is added.
Matches an implementation-dependent set of sequences, which must
be
the same as the set of sequences that is produced by
the conversion of the corresponding 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 conversion is undefined.
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 functions. Execution of a conversion
specification does not increment the assignment count
returned at the completion of execution of the func‐
tion.
Same as
S Same as
Matches a single
no conversion or assignment occurs. The complete con‐
version specification must be
If a conversion specification is invalid, the behavior is undefined.
The conversion characters and are also valid and behave the same as,
respectively, and
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 have been read (other than leading
white-space, where permitted), execution of the current conversion
specification terminates with an input failure. Otherwise, unless exe‐
cution 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 is equivalent to encountering end-of-
file for
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 suc‐
cess of literal matches and suppressed assignments is only directly
determinable via the conversion specification.
The and functions may mark the field of the file associated with stream
for update. The field will be marked for update by the first success‐
ful execution of or using stream that returns data not supplied by a
prior call to
APPLICATION USAGE
After or is applied to a stream, the stream becomes wide-oriented (see
orientation(5)).
In format strings containing the form of conversion specifications,
each argument in the argument list is used exactly once.
The prototypes of these functions are available to applications if they
are:
a. conformant.
b. Compiled with macro with a value >=500.
c. Compiled with macro with a value >= 200112.
RETURN VALUE
Upon successful completion, these functions return the number of suc‐
cessfully 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, is returned. If a read error occurs
the error indicator for the stream is set, is returned, and is set to
indicate the error.
ERRORS
For the conditions under which the functions will fail and may fail,
refer to In addition, may fail if:
Input byte sequence does not form a valid character.
There are insufficient arguments.
Insufficient storage space is available.
In addition, may fail if:
The stream pointed to by
stream is byte-oriented.
In addition, may fail if:
is byte-oriented.
EXAMPLES
The call:
with the input line:
will assign to n the value 3, to i the value 25, x the value 5.432, and
name will contain the string
The call:
with input:
will assign 56 to i, 789.0 to x, skip 0123, and place the string 56 in
name. The next call to will return the character
AUTHOR
were developed by HP and Mitsubishi Electric Corporation.
SEE ALSOfwprintf(3C), getwc(3C), setlocale(3C), wcstod(3C), wcstol(3C), wcr‐
tomb(3C), wcstoul(3C), langinfo(5), orientation(5), thread_safety(5),
glossary(9).
fwscanf(3C)
