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 (con-
       sult 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 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-position-
       ing 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 indi-
       cator  for the stream after reading or discarding all pushed-back characters shall be the same as it was before the char-
       acters 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   UNGETWC(3P)