swscanf
, fwscanf
, wscanf
—scan and format wide character input#include <stdio.h> int wscanf(const wchar_t *format, ...); int fwscanf(FILE *fd, const wchar_t *format, ...); int swscanf(const wchar_t *str, const wchar_t *format, ...); int _wscanf_r(struct _reent *ptr, const wchar_t *format, ...); int _fwscanf_r(struct _reent *ptr, FILE *fd, const wchar_t *format, ...); int _swscanf_r(struct _reent *ptr, const wchar_t *str, const wchar_t *format, ...);
Description
wscanf
scans a series of input fields from standard input,
one wide character at a time. Each field is interpreted according to
a format specifier passed to wscanf
in the format string at
*
format. wscanf
stores the interpreted input from
each field at the address passed to it as the corresponding argument
following format. You must supply the same number of
format specifiers and address arguments as there are input fields.
There must be sufficient address arguments for the given format specifiers; if not the results are unpredictable and likely disasterous. Excess address arguments are merely ignored.
wscanf
often produces unexpected results if the input diverges from
an expected pattern. Since the combination of gets
or fgets
followed by swscanf
is safe and easy, that is the preferred way
to be certain that a program is synchronized with input at the end
of a line.
fwscanf
and swscanf
are identical to wscanf
, other than the
source of input: fwscanf
reads from a file, and swscanf
from a string.
The routines _wscanf_r
, _fwscanf_r
, and _swscanf_r
are reentrant
versions of wscanf
, fwscanf
, and swscanf
that take an additional
first argument pointing to a reentrancy structure.
The string at *
format is a wide character sequence composed
of zero or more directives. Directives are composed of
one or more whitespace characters, non-whitespace characters,
and format specifications.
Whitespace characters are blank ( ), tab (\t
), or
newline (\n
).
When wscanf
encounters a whitespace character in the format string
it will read (but not store) all consecutive whitespace characters
up to the next non-whitespace character in the input.
Non-whitespace characters are all other ASCII characters except the
percent sign (%
). When wscanf
encounters a non-whitespace
character in the format string it will read, but not store
a matching non-whitespace character.
Format specifications tell wscanf
to read and convert characters
from the input field into specific types of values, and store then
in the locations specified by the address arguments.
Trailing whitespace is left unread unless explicitly matched in the format string.
The format specifiers must begin with a percent sign (%
)
and have the following form:
%[*][width][size]type
Each format specification begins with the percent character (%
).
The other fields are:
*
wscanf
reads all the characters in the field, and then
proceeds with the next field and its format specification.
If a whitespace or a non-convertable wide character occurs
before width character are read, the characters up
to that character are read, converted, and stored.
Then wscanf
proceeds to the next format specification.
size
h
, j
, l
, L
, t
, and z
are optional size
characters which override the default way that wscanf
interprets the data type of the corresponding argument.
Modifier Type(s) hh d, i, o, u, x, n convert input to char, store in char object h d, i, o, u, x, n convert input to short, store in short object h e, f, c, s, p no effect j d, i, o, u, x, n convert input to intmax_t, store in intmax_t object j all others no effect l d, i, o, u, x, n convert input to long, store in long object l e, f, g convert input to double store in a double object l c, s, [ the input is stored in a wchar_t object l p no effect ll d, i, o, u, x, n convert to long long, store in long long L d, i, o, u, x, n convert to long long, store in long long L e, f, g, E, G convert to long double, store in long double L all others no effect t d, i, o, u, x, n convert input to ptrdiff_t, store in ptrdiff_t object t all others no effect z d, i, o, u, x, n convert input to size_t, store in size_t object z all others no effect
wscanf
performs. Here is a table of the conversion
characters:
%
%
) is stored.
c
(char *arg)
.
Otherwise, if an l
specifier is present, the corresponding
arg is a (wchar_t *arg)
.
s
(char arg[])
.
If an l
specifier is present, the corresponding arg is a (wchar_t *arg)
.
[
pattern]
(char *arg)
.
If an l
specifier is present, the corresponding arg is
a (wchar_t *arg)
.
d
(int *arg)
.
o
(int *arg)
.
u
(unsigned int *arg)
.
x,X
(int *arg)
.
e, f, g
(float *arg)
.
E, F, G
(double *arg)
.
i
(int *arg)
.
n
(int *arg)
.
p
%p
exactly the same as %U
. Corresponding
arg: (void **arg)
.
A pattern of characters surrounded by square brackets can be used
instead of the s
type character. pattern is a set of
characters which define a search set of possible characters making up
the wscanf
input field. If the first character in the brackets is a
caret (^
), the search set is inverted to include all ASCII characters
except those between the brackets. There is no range facility as is
defined in the corresponding non-wide character scanf functions.
Ranges are not part of the POSIX standard.
Here are some pattern examples:
%[abcd]
a
, b
, c
, and d
.
%[^abcd]
a
, b
, c
, or d
.
%[A-DW-Z]
A
, -
, D
, W
, Z
.
Floating point numbers (for field types e
, f
, g
, E
,
F
, G
) must correspond to the following general form:
[+/-] ddddd[.]ddd [E|e[+|-]ddd]
where objects inclosed in square brackets are optional, and ddd
represents decimal, octal, or hexadecimal digits.
Returns
wscanf
returns the number of input fields successfully
scanned, converted and stored; the return value does
not include scanned fields which were not stored.
If wscanf
attempts to read at end-of-file, the return
value is EOF
.
If no fields were stored, the return value is 0
.
wscanf
might stop scanning a particular field before
reaching the normal field end character, or may
terminate entirely.
wscanf
stops scanning and storing the current field
and moves to the next input field (if any)
in any of the following situations:
*
) appears
after the %
in the format specification; the current
input field is scanned but not stored.
Z
is read when the format is decimal).
When wscanf
stops scanning the current input field for one of
these reasons, the next character is considered unread and
used as the first character of the following input field, or the
first character in a subsequent read operation on the input.
wscanf
will terminate under the following circumstances:
WEOF
.
When the format string contains a wide character sequence that is
not part of a format specification, the same wide character
sequence must appear in the input; wscanf
will
scan but not store the matched characters. If a
conflict occurs, the first conflicting wide character remains in the
input as if it had never been read.
Portability
wscanf
is C99, POSIX-1.2008.
Supporting OS subroutines required: close
, fstat
, isatty
,
lseek
, read
, sbrk
, write
.