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FWSCANF(P)			    POSIX Programmer's Manual			       FWSCANF(P)

NAME
       fwscanf, swscanf, wscanf - convert formatted wide-character input

SYNOPSIS
       #include <stdio.h>
       #include <wchar.h>

       int fwscanf(FILE *restrict stream, const wchar_t *restrict format, ... );
       int swscanf(const wchar_t *restrict ws,
	      const wchar_t *restrict format, ... );
       int wscanf(const wchar_t *restrict format, ... );

DESCRIPTION
       The  fwscanf()  function  shall	read  from the named input stream.  The wscanf() function
       shall read from the standard input stream stdin. The swscanf() function	shall  read  from
       the wide-character string ws. Each function reads wide characters, interprets them accord-
       ing 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 indi-
       cating 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 specifier wide char-
       acter % (see below) is replaced by the sequence "%n$" , where n is a  decimal  integer  in
       the range [1,{NL_ARGMAX}]. This feature provides for the definition of format wide-charac-
       ter strings that select arguments in an order appropriate to specific languages. In format
       wide-character  strings	containing  the  "%n$"	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. When numbered
       argument specifications are used, specifying the Nth argument requires that all the  lead-
       ing arguments, from the first to the ( N-1)th, are pointers.

       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 shall  default  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>s,
       <tab>s, <newline>s, <vertical-tab>s, or <form-feed>s); an ordinary wide character (neither
       '%' nor a white-space character); or a conversion specification.  Each conversion specifi-
       cation  is  introduced by a '%'	  or the sequence "%n$"  after which the following appear
       in sequence:

	* An optional assignment-suppressing character '*' .

	* An optional non-zero decimal integer that specifies the maximum field width.

	* An optional length modifier that specifies the size of the receiving object.

	* A conversion specifier wide character that specifies	the  type  of  conversion  to  be
	  applied. The valid conversion specifiers are described below.

       The fwscanf() functions shall execute each directive of the format in turn. If a directive
       fails, as detailed below, the function shall return. Failures are described as input fail-
       ures (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 shall be 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 shall fail,
       and the differing and subsequent wide characters remain unread. Similarly, if end-of-file,
       an encoding error, or a read error prevents a wide character from being read,  the  direc-
       tive shall fail.

       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  exe-
       cuted in the following steps.

       Input  white-space  wide characters (as specified by iswspace() ) shall be skipped, unless
       the conversion specification includes a [ , c , or n conversion specifier.

       An item shall be read from the input, unless the conversion specification  includes  an	n
       conversion  specifier  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 subse-
       quence  of  a  matching	sequence.  The first wide character, if any, after the input item
       shall remain unread.  If the length of the input item is zero, the execution of	the  con-
       version	specification  shall  fail;  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 specifier, the input item (or, in the case of a %n
       conversion specification, the count of input wide characters) shall be 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 shall fail; this  condition  is	a
       matching failure. Unless assignment suppression was indicated by a '*' , the result of the
       conversion shall be 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 speci-
       fication is introduced by % ,	or in the nth argument if introduced by the  wide-charac-
       ter 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 specifier wide characters are valid:

       d      Matches an optionally signed decimal integer, whose format is the same as  expected
	      for  the	subject  sequence of wcstol() with the value 10 for the base argument. In
	      the absence of a size modifier, the application shall ensure that the corresponding
	      argument is a pointer to int.

       i      Matches  an optionally signed integer, whose format is the same as expected for the
	      subject sequence of wcstol() with 0 for the base argument. In the absence of a size
	      modifier, the application shall ensure that the corresponding argument is a pointer
	      to int.

       o      Matches an optionally signed octal integer, whose format is the  same  as  expected
	      for  the	subject  sequence of wcstoul() with the value 8 for the base argument. In
	      the absence of a size modifier, the application shall ensure that the corresponding
	      argument is a pointer to unsigned.

       u      Matches  an optionally signed decimal integer, whose format is the same as expected
	      for the subject sequence of wcstoul() with the value 10 for the base  argument.  In
	      the absence of a size modifier, the application shall ensure that the corresponding
	      argument is a pointer to unsigned.

       x      Matches an optionally signed hexadecimal integer,  whose	format	is  the  same  as
	      expected for the subject sequence of wcstoul() with the value 16 for the base argu-
	      ment. In the absence of a size modifier, the application shall ensure that the cor-
	      responding argument is a pointer to unsigned.

       a, e, f, g

	      Matches  an  optionally signed floating-point number, infinity, or NaN whose format
	      is the same as expected for the subject sequence of wcstod(). In the absence  of	a
	      size  modifier,  the  application shall ensure that the corresponding argument is a
	      pointer to float.

       If the fwprintf() family of  functions  generates  character  string  representations  for
       infinity  and  NaN  (a  symbolic  entity  encoded  in  floating-point  format)  to support
       IEEE Std 754-1985, the fwscanf() family of functions shall recognize them as input.

       s      Matches a sequence of non white-space wide characters. If no l (ell)  qualifier  is
	      present, characters from the input field shall be 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 appli-
	      cation shall ensure that the corresponding argument is a	pointer  to  a	character
	      array large enough to accept the sequence and the terminating null character, which
	      shall be added automatically.

       Otherwise, the application shall ensure that the corresponding argument is a pointer to an
       array of wchar_t large enough to accept the sequence and the terminating null wide charac-
       ter, which shall be added automatically.

       [      Matches a non-empty sequence of wide characters from a set of expected wide charac-
	      ters  (the  scanset).  If no l (ell) qualifier is present, wide characters from the
	      input field shall be 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 application  shall  ensure  that
	      the corresponding argument is a pointer to a character array large enough to accept
	      the sequence and the terminating null character, which  shall  be  added	automati-
	      cally.

       If  an  l  (ell) qualifier is present, the application shall ensure that the corresponding
       argument is a pointer to an array of wchar_t large enough to accept the sequence  and  the
       terminating null wide character, which shall 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) 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 match-
       ing 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-defined.

       c      Matches  a sequence of wide characters of exactly the number specified by the field
	      width (1 if no field width is present in the conversion specification).

       If no l (ell) length modifier is present, characters from the input field  shall  be  con-
       verted  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  shall  be a pointer to the initial element of a
       character array large enough to accept the sequence.  No null character is added.

       If an l (ell) length modifier is present, the corresponding argument shall be a pointer to
       the  initial  element  of an array of wchar_t large enough to accept the sequence. No null
       wide character is added.

       Otherwise, the application shall ensure that the corresponding argument is a pointer to an
       array of wchar_t large enough to accept the sequence. No null wide character is added.

       p      Matches  an implementation-defined set of sequences, which shall be the same as the
	      set of sequences that is produced by the %p conversion specification of the  corre-
	      sponding	fwprintf() functions. The application shall ensure that the corresponding
	      argument is a pointer to a pointer to void. The interpretation of the input item is
	      implementation-defined.  If  the input item is a value converted earlier during the
	      same program execution, the pointer that results shall compare equal to that value;
	      otherwise, the behavior of the %p conversion is undefined.

       n      No  input is consumed. The application shall ensure that the corresponding argument
	      is a pointer to the integer into which is to be written the number of wide  charac-
	      ters  read from the input so far by this call to the fwscanf() functions. Execution
	      of a %n conversion specification shall not increment the assignment count  returned
	      at the completion of execution of the function. No argument shall be converted, but
	      one shall be consumed.  If the conversion specification includes an assignment-sup-
	      pressing wide character or a field width, the behavior is undefined.

       C      Equivalent to lc .

       S      Equivalent to ls .

       %      Matches  a  single '%' wide character; no conversion or assignment shall occur. The
	      complete conversion specification shall be %% .

       If a conversion specification is invalid, the behavior is undefined.

       The conversion specifiers A , E , F , G , and X are also valid and shall be equivalent to,
       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 shall terminate 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) shall be  terminated
       with an input failure.

       Reaching  the  end  of the string in swscanf() shall be equivalent to encountering end-of-
       file for fwscanf().

       If conversion terminates on a conflicting input, the offending input shall be left  unread
       in  the	input. Any trailing white space (including <newline>) shall be 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 shall be marked for update by  the  first  suc-
       cessful	execution  of  fgetc(),  fgetwc(),  fgets(),  fgetws(), fread(), getc(), getwc(),
       getchar(), getwchar(), gets(), fscanf(), or fwscanf() using stream that returns	data  not
       supplied by a prior call to ungetc().

RETURN VALUE
       Upon  successful  completion,  these  functions	shall  return  the number of successfully
       matched and assigned input items; this number can be zero in the event of an early  match-
       ing  failure. If the input ends before the first matching failure or conversion, EOF shall
       be returned. If a read error occurs, the error indicator for the stream is set, EOF  shall
       be returned,    and errno shall be set to indicate the error.

ERRORS
       For  the  conditions under which the fwscanf() functions shall fail and may fail, refer to
       fgetwc() .

       In addition, fwscanf() may fail if:

       EILSEQ Input byte sequence does not form a valid character.

       EINVAL There are insufficient arguments.

       The following sections are informative.

EXAMPLES
       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

       assigns to n the value 3, to i the value 25, to x the value 5.432, and name  contains  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

       assigns	56  to	i, 789.0 to x, skips 0123, and places the string "56\0" in name. The next
       call to getchar() shall return the character 'a' .

APPLICATION USAGE
       In format strings containing the '%' form of conversion specifications, each  argument  in
       the argument list is used exactly once.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       getwc()	,  fwprintf()  ,  setlocale() , wcstod() , wcstol() , wcstoul() , wcrtomb() , the
       Base  Definitions  volume  of  IEEE Std 1003.1-2001,  Chapter  7,  Locale,   <langinfo.h>,
       <stdio.h>, <wchar.h>

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				       FWSCANF(P)
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