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UNGETWC(3P) POSIX Programmer's Manual UNGETWC(3P)
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.
ungetwc — push wide-character code back into the input stream
#include <stdio.h>
#include <wchar.h>
wint_t ungetwc(wint_t wc, FILE *stream);
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.1‐2008 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.
Upon successful completion, ungetwc() shall return the wide-character
code corresponding to the pushed-back character. Otherwise, it shall
return WEOF.
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.
None.
None.
None.
None.
Section 2.5, Standard I/O Streams, fseek(3p), fsetpos(3p), read(3p),
rewind(3p), setbuf(3p)
The Base Definitions volume of POSIX.1‐2008, stdio.h(0p), wchar.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 UNGETWC(3P)
Pages that refer to this page: wchar.h(0p)