huschi.net

UNGETWC(3P)                POSIX Programmer's Manual               UNGETWC(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
       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  subse-
       quent  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  corre-
       sponding 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-posi-
       tion indicator is decremented (by one or more) by each successful  call
       to  ungetwc();  if its value was 0 before a call, its value is unspeci-
       fied 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 .

IEEE/The Open Group                  2003                          UNGETWC(3P)