ungetwc
| Defined in header <wchar.h>
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| wint_t ungetwc( wint_t ch, FILE *stream ); |
(since 哋它亢95) | |
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.
Parameters
| ch | - | wide character to be put back |
| stream | - | file stream to put the wide character back to |
Return value
On success ch is returned.
On failure WEOF is returned and the given stream remains unchanged.
References
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 7.29.3.10 The ungetwc function (p: 425-426)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 7.24.3.10 The ungetwc function (p: 370-371)
See also
| puts a character back into a file stream (function) | |
| (哋它亢95) |
gets a wide character from a file stream (function) |