NAME
wscanf,
fwscanf,
swscanf,
vwscanf,
vswscanf,
vfwscanf —
wide character input
format conversion
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdio.h>
#include <wchar.h>
int
wscanf(
const
wchar_t * restrict format,
...);
int
fwscanf(
FILE *
restrict stream,
const
wchar_t * restrict format,
...);
int
swscanf(
const
wchar_t * restrict str,
const wchar_t * restrict
format,
...);
#include <stdarg.h>
int
vwscanf(
const
wchar_t * restrict format,
va_list ap);
int
vswscanf(
const
wchar_t * restrict str,
const wchar_t * restrict
format,
va_list ap);
int
vfwscanf(
FILE *
restrict stream,
const
wchar_t * restrict format,
va_list ap);
DESCRIPTION
The
wscanf() family of functions scans input according to a
format as described below. This format may contain
conversion specifiers; the results from such conversions, if
any, are stored through the
pointer arguments. The
wscanf() function reads input from the standard input stream
stdin
,
fwscanf() reads input from
the stream pointer
stream, and
swscanf() reads its input from the wide-character string
pointed to by
str. The
vfwscanf()
function is analogous to
vfwprintf(3) and reads input
from the stream pointer
stream using a variable argument
list of pointers (see
stdarg(3)). The
vwscanf() function scans a variable argument list from the
standard input and the
vswscanf() function scans it from a
wide-character string; these are analogous to the
vwprintf()
and
vswprintf() functions respectively. Each successive
pointer argument must correspond properly with each
successive conversion specifier (but see the
* conversion
below). All conversions are introduced by the
% (percent
sign) character. The
format string may also contain
other characters. White space (such as blanks, tabs, or newlines) in the
format string match any amount of white space, including
none, in the input. Everything else matches only itself. Scanning stops when
an input character does not match such a format character. Scanning also stops
when an input conversion cannot be made (see below).
CONVERSIONS
Following the
% character introducing a conversion there may
be a number of
flag characters, as follows:
-
-
- *
- Suppresses assignment. The conversion that follows occurs
as usual, but no pointer is used; the result of the conversion is simply
discarded.
-
-
- hh
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a char (rather than
int).
-
-
- h
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a short int (rather than
int).
-
-
- l
(ell)
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a long int (rather than
int), that the conversion will be one of
a, e, f, or
g and the next pointer is a pointer to
double (rather than float), or
that the conversion will be one of c or
s and the next pointer is a pointer to an array of
wchar_t (rather than
char).
-
-
- ll
(ell ell)
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a long long int (rather than
int).
-
-
- L
- Indicates that the conversion will be one of
a, e, f, or
g and the next pointer is a pointer to
long double.
-
-
- j
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a intmax_t (rather than
int).
-
-
- t
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a ptrdiff_t (rather than
int).
-
-
- z
- Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a size_t (rather than
int).
-
-
- q
- (deprecated.) Indicates that the conversion will be one of
dioux or n and the next pointer is a
pointer to a long long int (rather than
int).
In addition to these flags, there may be an optional maximum field width,
expressed as a decimal integer, between the
% and the
conversion. If no width is given, a default of “infinity” is used
(with one exception, below); otherwise at most this many characters are
scanned in processing the conversion. Before conversion begins, most
conversions skip white space; this white space is not counted against the
field width.
The following conversions are available:
-
-
- %
- Matches a literal ‘
%
’.
That is, “%%
” in the format string
matches a single input ‘%
’ character.
No conversion is done, and assignment does not occur.
-
-
- d
- Matches an optionally signed decimal integer; the next
pointer must be a pointer to int.
-
-
- i
- Matches an optionally signed integer; the next pointer must
be a pointer to int. The integer is read in base 16
if it begins with ‘
0x
’ or
‘0X
’, in base 8 if it begins with
‘0
’, and in base 10 otherwise. Only
characters that correspond to the base are used.
-
-
- o
- Matches an octal integer; the next pointer must be a
pointer to unsigned int.
-
-
- u
- Matches an optionally signed decimal integer; the next
pointer must be a pointer to unsigned int.
-
-
- x,
X
- Matches an optionally signed hexadecimal integer; the next
pointer must be a pointer to unsigned int.
-
-
- a,
A, e, E,
f, F, g,
G
- Matches a floating-point number in the style of
wcstod(3). The next pointer
must be a pointer to float (unless
l or L is specified.)
-
-
- s
- Matches a sequence of non-white-space wide characters; the
next pointer must be a pointer to char, and the
array must be large enough to accept the multibyte representation of all
the sequence and the terminating
NUL
character.
The input string stops at white space or at the maximum field width,
whichever occurs first.
If an l qualifier is present, the next pointer must be a
pointer to wchar_t, into which the input will be
placed.
-
-
- S
- The same as ls.
-
-
- c
- Matches a sequence of width count wide
characters (default 1); the next pointer must be a pointer to
char, and there must be enough room for the
multibyte representation of all the characters (no terminating
NUL
is added). The usual skip of leading white
space is suppressed. To skip white space first, use an explicit space in
the format.
If an l qualifier is present, the next pointer must be a
pointer to wchar_t, into which the input will be
placed.
-
-
- C
- The same as lc.
-
-
- [
- Matches a nonempty sequence of characters from the
specified set of accepted characters; the next pointer must be a pointer
to char, and there must be enough room for the
multibyte representation of all the characters in the string, plus a
terminating
NUL
character. The usual skip of
leading white space is suppressed. The string is to be made up of
characters in (or not in) a particular set; the set is defined by the
characters between the open bracket [ character and a
close bracket ] character. The set
excludes those characters if the first character after
the open bracket is a circumflex ^. To include a close
bracket in the set, make it the first character after the open bracket or
the circumflex; any other position will end the set. To include a hyphen
in the set, make it the last character before the final close bracket;
some implementations of wscanf() use
“A-Z
” to represent the range of
characters between ‘A
’ and
‘Z
’. The string ends with the
appearance of a character not in the (or, with a circumflex, in) set or
when the field width runs out.
If an l qualifier is present, the next pointer must be a
pointer to wchar_t, into which the input will be
placed.
-
-
- p
- Matches a pointer value (as printed by
‘
%p
’ in
wprintf(3)); the next
pointer must be a pointer to void.
-
-
- n
- Nothing is expected; instead, the number of characters
consumed thus far from the input is stored through the next pointer, which
must be a pointer to int. This is
not a conversion, although it can be suppressed with the
* flag.
The decimal point character is defined in the program's locale (category
LC_NUMERIC
).
For backwards compatibility, a “conversion” of
‘
%\0
’ causes an immediate return of
EOF
.
RETURN VALUES
These functions return the number of input items assigned, which can be fewer
than provided for, or even zero, in the event of a matching failure. Zero
indicates that, while there was input available, no conversions were assigned;
typically this is due to an invalid input character, such as an alphabetic
character for a ‘
%d
’ conversion. The value
EOF
is returned if an input failure occurs before any
conversion such as an end-of-file occurs. If an error or end-of-file occurs
after conversion has begun, the number of conversions which were successfully
completed is returned.
SEE ALSO
fgetwc(3),
scanf(3),
wcrtomb(3),
wcstod(3),
wcstol(3),
wcstoul(3),
wprintf(3)
STANDARDS
The
fwscanf(),
wscanf(),
swscanf(),
vfwscanf(),
vwscanf() and
vswscanf() functions conform
to
ISO/IEC 9899:1999 (“ISO C99”).
BUGS
In addition to the bugs documented in
scanf(3),
wscanf() does not support the
“
A-Z
” notation for specifying character
ranges with the character class conversion
(‘
%[’).