ungetwc - push back a wide character onto a FILE stream

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ ungetwc()                                                                   │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       The ungetwc() function is the wide-character equivalent of the ungetc(3) function.  It pushes back a wide
       character onto stream and returns it.

       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.

       POSIX.1-2001, C99.

       Standard C library (libc, -lc)

       ungetwc - push back a wide character onto a FILE stream

       The behavior of ungetwc() depends on the LC_CTYPE category of the current locale.

       The ungetwc() function returns wc when successful, or WEOF upon failure.

fgetwc(3)

Linux man-pages 6.9.1                              2024-05-02                                         ungetwc(3)

       C11, POSIX.1-2008.

#include<wchar.h>wint_tungetwc(wint_twc,FILE*stream);