ungetwc

wint_t ungetwc( wint_t ch, FILE *stream );

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

Return value

On success ch is returned.

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

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)

See also