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ungetwc

From cppreference.com
< c‎ | io
 
 
File input/output
Types and objects
        
Functions
File access
Unformatted input/output
(C95)(C95)
(C95)
(C95)(C95)
(C95)
(C95)
(C95)
ungetwc
(C95)

Formatted input
 
Defined in header <wchar.h>
wint_t ungetwc( wint_t ch, FILE *stream );
(since C95)

If ch does not equal WEOF, pushes the wide character ch into the input buffer associated with the stream stream in such a manner that subsequent read operation from stream will retrieve that wide character. The external device associated with the stream is not modified.

Stream repositioning operations fseek , fsetpos , and rewind discard the effects of ungetwc.

If ungetwc is called more than once without an intervening read or repositioning, it may fail (in other words, a pushback buffer of size 1 is guaranteed, but any larger buffer is implementation-defined). If multiple successful ungetwc were performed, read operations retrieve the pushed-back wide characters in reverse order of ungetwc

If ch equals WEOF, the operation fails and the stream is not affected.

A successful call to ungetwc clears the end of file status flag feof .

A successful call to ungetwc on a stream (whether text or binary) modifies the stream position indicator in unspecified manner but guarantees that after all pushed-back wide characters are retrieved with a read operation, the stream position indicator is equal to its value before ungetwc.

[edit] Parameters

ch - wide character to be put back
stream - file stream to put the wide character back to

[edit] Return value

On success ch is returned.

On failure WEOF is returned and the given stream remains unchanged.

[edit] References

  • C11 standard (ISO/IEC 9899:2011):
  • 7.29.3.10 The ungetwc function (p: 425-426)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.24.3.10 The ungetwc function (p: 370-371)

[edit] See also

puts a character back into a file stream
(function) [edit]
gets a wide character from a file stream
(function) [edit]
C++ documentation for ungetwc
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