1UNGETWC(3P)                POSIX Programmer's Manual               UNGETWC(3P)
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PROLOG

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

13       ungetwc — push wide-character code back into the input stream
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SYNOPSIS

16       #include <stdio.h>
17       #include <wchar.h>
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19       wint_t ungetwc(wint_t wc, FILE *stream);
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DESCRIPTION

22       The functionality described on this reference page is aligned with  the
23       ISO C  standard.  Any  conflict between the requirements described here
24       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
25       defers to the ISO C standard.
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27       The  ungetwc()  function  shall push the character corresponding to the
28       wide-character code specified by wc back onto the input stream  pointed
29       to  by  stream.  The pushed-back characters shall be returned by subse‐
30       quent reads on that stream in the reverse order  of  their  pushing.  A
31       successful intervening call (with the stream pointed to by stream) to a
32       file-positioning function (fseek(), fseeko(), fsetpos(),  or  rewind())
33       or  fflush()  shall  discard any pushed-back characters for the stream.
34       The external storage corresponding to the stream is unchanged.
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36       At least one character of push-back shall be provided. If ungetwc()  is
37       called too many times on the same stream without an intervening read or
38       file-positioning operation on that stream, the operation may fail.
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40       If the value of wc equals that of the macro WEOF, the  operation  shall
41       fail and the input stream shall be left unchanged.
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43       A  successful  call  to ungetwc() shall clear the end-of-file indicator
44       for the stream. The value of the file-position indicator for the stream
45       after  all pushed-back characters have been read, or discarded by call‐
46       ing fseek(), fseeko(), fsetpos(), or rewind() (but not fflush()), shall
47       be the same as it was before the characters were pushed back. The file-
48       position indicator is decremented (by one or more) by  each  successful
49       call  to  ungetwc();  if  its  value  was 0 before a call, its value is
50       unspecified after the call.
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RETURN VALUE

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

58       The ungetwc() function may fail if:
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60       EILSEQ An invalid character sequence is detected, or  a  wide-character
61              code does not correspond to a valid character.
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63       The following sections are informative.
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EXAMPLES

66       None.
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APPLICATION USAGE

69       None.
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RATIONALE

72       None.
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FUTURE DIRECTIONS

75       None.
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SEE ALSO

78       Section   2.5,   Standard  I/O  Streams,  fseek(),  fsetpos(),  read(),
79       rewind(), setbuf()
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81       The Base Definitions volume of POSIX.1‐2008, <stdio.h>, <wchar.h>
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84       Portions of this text are reprinted and reproduced in  electronic  form
85       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
86       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
87       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
88       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
89       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
90       event of any discrepancy between this version and the original IEEE and
91       The  Open Group Standard, the original IEEE and The Open Group Standard
92       is the referee document. The original Standard can be  obtained  online
93       at http://www.unix.org/online.html .
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95       Any  typographical  or  formatting  errors that appear in this page are
96       most likely to have been introduced during the conversion of the source
97       files  to  man page format. To report such errors, see https://www.ker
98       nel.org/doc/man-pages/reporting_bugs.html .
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102IEEE/The Open Group                  2013                          UNGETWC(3P)
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