From cppreference.com
< c‎ | io
Defined in header <wchar.h>
wint_t ungetwc( wint_t ch, FILE *stream );

Puts the wide character ch back to the given file stream. Only one wide character pushback is guaranteed.

[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] See also

puts a character back into a file stream
gets a wide character from a file stream
C++ documentation for ungetwc