NAME

       ungetwc - push wide-character code back into the input stream

SYNOPSIS

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

       wint_t ungetwc(wint_t wc, FILE *stream);

DESCRIPTION

       The  ungetwc()  function shall push the character corresponding to the wide-character code
       specified by wc back  onto  the  input  stream  pointed  to  by  stream.  The  pushed-back
       characters  shall  be  returned by subsequent reads on that stream in the reverse order of
       their pushing. A successful intervening call (with the stream pointed to by stream)  to  a
       file-positioning  function  (  fseek(),  fsetpos(),  or rewind()) discards any pushed-back
       characters for the stream. The external storage corresponding to the stream is unchanged.

       At least one character of push-back shall be provided. If ungetwc()  is  called  too  many
       times on the same stream without an intervening read or file-positioning operation on that
       stream, the operation may fail.

       If the value of wc equals that of the macro WEOF, the operation shall fail and  the  input
       stream shall be left unchanged.

       A  successful  call to ungetwc() shall clear the end-of-file indicator for the stream. The
       value of the file-position indicator for  the  stream  after  reading  or  discarding  all
       pushed-back characters shall be the same as it was before the characters were pushed back.
       The file-position indicator is decremented (by one or more) by  each  successful  call  to
       ungetwc(); if its value was 0 before a call, its value is unspecified after the call.

RETURN VALUE

       Upon  successful  completion, ungetwc() shall return the wide-character code corresponding
       to the pushed-back character.  Otherwise, it shall return WEOF.

ERRORS

       The ungetwc() function may fail if:

       EILSEQ An invalid character sequence is  detected,  or  a  wide-character  code  does  not
              correspond to a valid character.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       fseek()  ,  fsetpos()  ,  read()  ,  rewind()  , setbuf() , the Base Definitions volume of
       IEEE Std 1003.1-2001, <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 .