NAME¶

std::ungetwc - std::ungetwc

Synopsis¶

Defined in header <cwchar>
std::wint_t ungetwc( std::wint_t ch, std::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 than subsequent read operation
from stream will retrieve that wide character. The external device associated with
the stream is not modified.

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

If std::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
std::ungetwc were performed, read operations retrieve the pushed-back wide
characters in reverse order of std::ungetwc

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

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

A successful call to std::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 std::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.

See also¶

ungetc puts a character back into a file stream
(function)
fgetwc gets a wide character from a file stream
getwc (function)
C documentation for
ungetwc