код символа обратно во входной поток (character code back into the input stream)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
ungetwc — push wide-character code back into the input stream
Синопсис (Synopsis)
#include <stdio.h>
#include <wchar.h>
wint_t ungetwc(wint_t wc, FILE *stream);
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
The ungetwc() function shall push the character corresponding to
the wide-character code specified by wc back onto the input
stream pointed to by stream. The pushed-back characters shall be
returned by subsequent reads on that stream in the reverse order
of their pushing. A successful intervening call (with the stream
pointed to by stream) to a file-positioning function (fseek(),
fseeko(), fsetpos(), or rewind()) or fflush() shall discard any
pushed-back characters for the stream. The external storage
corresponding to the stream is unchanged.
At least one character of push-back shall be provided. If
ungetwc() is called too many times on the same stream without an
intervening read or file-positioning operation on that stream,
the operation may fail.
If the value of wc equals that of the macro WEOF, the operation
shall fail and the input stream shall be left unchanged.
A successful call to ungetwc() shall clear the end-of-file
indicator for the stream. The value of the file-position
indicator for the stream after all pushed-back characters have
been read, or discarded by calling fseek(), fseeko(), fsetpos(),
or rewind() (but not fflush()), shall be the same as it was
before the characters were pushed back. The file-position
indicator is decremented (by one or more) by each successful call
to ungetwc(); if its value was 0 before a call, its value is
unspecified after the call.
Возвращаемое значение (Return value)
Upon successful completion, ungetwc() shall return the wide-
character code corresponding to the pushed-back character.
Otherwise, it shall return WEOF.
Ошибки (Error)
The ungetwc() function may fail if:
EILSEQ An invalid character sequence is detected, or a wide-
character code does not correspond to a valid character.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.5, Standard I/O Streams, fseek(3p), fsetpos(3p),
read(3p), rewind(3p), setbuf(3p)
The Base Definitions volume of POSIX.1‐2017, stdio.h(0p),
wchar.h(0p)
