SWSCANF(3) NEWLIB SWSCANF(3)NAME
4.63 `swscanf', `fwscanf', `wscanf'--scan and format wide character
input
SYNOPSIS
#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 disaster‐
ous. 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 reen‐
trant versions of `wscanf', `fwscanf', and `swscanf' that take an addi‐
tional 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 white‐
space characters, non-whitespace characters, and format specifications.
Whitespace characters are blank (` '), tab (`'), or newline (`0).
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 charac‐
ter 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: `*'
an optional marker; if present, it suppresses interpretation and
assignment of this input field.
`WIDTH'
an optional maximum field width: a decimal integer, which controls
the maximum number of characters that will be read before
converting the current input field. If the input field has fewer
than WIDTH characters, `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
`TYPE'
A character to specify what kind of conversion `wscanf' performs.
Here is a table of the conversion characters:
`%'
No conversion is done; the percent character (`%') is stored.
`c'
Scans one wide character. Corresponding ARG: `(char *arg)'.
Otherwise, if an `l' specifier is present, the corresponding
ARG is a `(wchar_t *arg)'.
`s'
Reads a character string into the array supplied.
Corresponding ARG: `(char arg[])'. If an `l' specifier is
present, the corresponding ARG is a `(wchar_t *arg)'.
`[PATTERN]'
Reads a non-empty character string into memory starting at
ARG. This area must be large enough to accept the sequence
and a terminating null character which will be added
automatically. (PATTERN is discussed in the paragraph
following this table). Corresponding ARG: `(char *arg)'. If
an `l' specifier is present, the corresponding ARG is a
`(wchar_t *arg)'.
`d'
Reads a decimal integer into the corresponding ARG: `(int
*arg)'.
`o'
Reads an octal integer into the corresponding ARG: `(int
*arg)'.
`u'
Reads an unsigned decimal integer into the corresponding ARG:
`(unsigned int *arg)'.
`x,X'
Read a hexadecimal integer into the corresponding ARG: `(int
*arg)'.
`e, f, g'
Read a floating-point number into the corresponding ARG:
`(float *arg)'.
`E, F, G'
Read a floating-point number into the corresponding ARG:
`(double *arg)'.
`i'
Reads a decimal, octal or hexadecimal integer into the
corresponding ARG: `(int *arg)'.
`n'
Stores the number of characters read in the corresponding
ARG: `(int *arg)'.
`p'
Stores a scanned pointer. ANSI C leaves the details to each
implementation; this implementation treats `%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]'
matches wide character strings containing only `a', `b', `c',
and `d'.
`%[^abcd]'
matches wide character strings containing any characters
except `a', `b', `c', or `d'.
`%[A-DW-Z]'
Note: No wide character ranges, so this expression matches
wide character strings containing `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, con‐
verted 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:
* The assignment suppressing character (`*') appears after the `%'
in the format specification; the current input field is scanned
but not stored.
* WIDTH characters have been read (WIDTH is a width specification, a
positive decimal integer).
* The next wide character read cannot be converted under the the
current format (for example, if a `Z' is read when the format is
decimal).
* The next wide character in the input field does not appear in the
search set (or does appear in the inverted search set).
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:
* The next wide character in the input field conflicts with a
corresponding non-whitespace character in the format string.
* The next wide character in the input field is `WEOF'.
* The format string has been exhausted.
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'.
SEE ALSOswscanf is part of the library. The full documentation for is main‐
tained as a Texinfo manual. If info and are properly installed at your
site, the command
info
will give you access to the complete manual.
NEWLIB April 2010 SWSCANF(3)
