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'\" t
.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" References consulted:
.\" GNU glibc-2 source code and manual
.\" Dinkumware C library reference http://www.dinkumware.com/
.\" OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
.\" ISO/IEC 9899:1999
.\"
.TH ungetwc 3 2024-05-02 "Linux man-pages (unreleased)"
.SH NAME
ungetwc \- push back a wide character onto a FILE stream
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <wchar.h>
.P
.BI "wint_t ungetwc(wint_t " wc ", FILE *" stream );
.fi
.SH DESCRIPTION
The
.BR ungetwc ()
function is the wide-character equivalent of the
.BR ungetc (3)
function.
It pushes back a wide character onto
.I stream
and returns it.
.P
If
.I wc
is
.BR WEOF ,
it returns
.BR WEOF .
If
.I wc
is an invalid wide character,
it sets
.I errno
to
.B EILSEQ
and returns
.BR WEOF .
.P
If
.I 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.
.P
Note:
.I wc
need not be the last wide-character read from the stream;
it can be any other valid wide character.
.P
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.
.SH RETURN VALUE
The
.BR ungetwc ()
function returns
.I wc
when successful, or
.B WEOF
upon
failure.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR ungetwc ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, C99.
.SH NOTES
The behavior of
.BR ungetwc ()
depends on the
.B LC_CTYPE
category of the
current locale.
.SH SEE ALSO
.BR fgetwc (3)
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