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FWSCANF(3P)                POSIX Programmer's Manual               FWSCANF(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

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 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 specifier wide character % (see below)  is  replaced  by
       the  sequence  "%n$",  where  n  is  a  decimal  integer  in  the range
       [1,{NL_ARGMAX}]. This feature provides for  the  definition  of  format
       wide-character strings that select arguments in an order appropriate to
       specific languages. In format  wide-character  strings  containing  the
       "%n$" form of conversion specifications, it is unspecified whether num-
       bered 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 spec-
       ifications  are used, specifying the Nth argument requires that all the
       leading arguments, from the first to the ( N-1)th, are pointers.

       The fwscanf() function in all its forms allows for detection of a  lan-
       guage-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 direc-
       tives. 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
       specification 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 failures (due to the unavail-
       ability 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  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 charac-
       ter from being read, the directive shall fail.

       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 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  specifica-
       tion  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 subsequence 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 conversion 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  exe-
       cution  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 specification is
       introduced by %,  or in the nth argument if  introduced  by  the  wide-
       character  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 con-
              version 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 dou-
              ble.

       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 applica-
              tion 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 argument. In the absence of a
              size modifier, the application shall ensure that the correspond-
              ing 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 repre-
       sentations 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  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 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 character, which shall be added automati-
       cally.

       [      Matches  a  non-empty  sequence of wide characters from a set of
              expected wide characters (the scanset). If no l (ell)  qualifier
              is  present,  wide 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 initial-
              ized 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 auto-
              matically.

       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  circum-
       flex  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-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 converted as if by repeated calls to the wcrtomb() func-
       tion, with the conversion state described by an mbstate_t  object  ini-
       tialized  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 corresponding  fwprintf()  func-
              tions. The application shall ensure that the corresponding argu-
              ment 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; other-
              wise, the behavior of the %p conversion is undefined.

       n      No input is consumed. The application shall ensure that the cor-
              responding argument is 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 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-suppressing
              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 conver-
       sion  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 specifi-
       cation (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 specifi-
       cation. 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  successful  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 matching 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(), wcr-
       tomb(), 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 original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                          FWSCANF(3P)
 

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