ungetwc - push back a wide character onto a FILE stream
#include <wchar.h> wint_t ungetwc(wint_t wc, FILE *stream);
wc is WEOF, it returns WEOF. If
wc is an invalid wide character, it sets
errno to EILSEQ and returns WEOF.
wc is a valid wide character, it is pushed back onto the stream and thus becomes available for future wide-character read operations. The file-position indicator is decremented by one or more. The end-of-file indicator is cleared. The backing storage of the file is not affected.
wc need not be the last wide-character read from the stream; it can be any other valid wide character.
If the implementation supports multiple push-back operations in a row, the pushed-back wide characters will be read in reverse order; however, only one level of push-back is guaranteed.
The ungetwc() function returns
wc when successful, or WEOF upon failure.
POSIX.1-2001, POSIX.1-2008, C99.
The behavior of ungetwc() depends on the LC_CTYPE category of the current locale.
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