UNGETWC(3) Linux Programmer's Manual UNGETWC(3)
ungetwc - push back a wide character onto a FILE stream
wint_t ungetwc(wint_t wc, FILE *stream);
The ungetwc() function is the wide-character equivalent of the
ungetc(3) function. It pushes back a wide character onto stream and
If wc is WEOF, it returns WEOF. If wc is an invalid wide character, it
sets errno to EILSEQ and returns WEOF.
If 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.
Note: 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 fail-
Multithreading (see pthreads(7))
The ungetwc() function is thread-safe.
The behavior of ungetwc() depends on the LC_CTYPE category of the cur-
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GNU 2013-12-09 UNGETWC(3)