'\" et
.TH UNGETWC "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH 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.

.SH NAME
ungetwc
\(em push wide-character code back into the input stream
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>
#include <wchar.h>
.P
wint_t ungetwc(wint_t \fIwc\fP, FILE *\fIstream\fP);
.fi
.SH 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\(hy2008 defers to the ISO\ C standard.
.P
The
\fIungetwc\fR()
function shall push the character corresponding to the wide-character
code specified by
.IR wc
back onto the input stream pointed to by
.IR 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
.IR stream )
to a file-positioning function (\c
\fIfseek\fR(),
\c
\fIfseeko\fR(),
\fIfsetpos\fR(),
or
\fIrewind\fR())
or
\fIfflush\fR()
shall discard any pushed-back characters for the stream. The external
storage corresponding to the stream is unchanged.
.P
At least one character of push-back shall be provided. If
\fIungetwc\fR()
is called too many times on the same stream without an intervening read
or file-positioning operation on that stream, the operation may fail.
.P
If the value of
.IR wc
equals that of the macro WEOF, the operation shall fail and the input
stream shall be left unchanged.
.P
A successful call to
\fIungetwc\fR()
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
\fIfseek\fR(),
\c
\fIfseeko\fR(),
\fIfsetpos\fR(),
or
\fIrewind\fR()
(but not
\fIfflush\fR()),
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
\fIungetwc\fR();
if its value was 0 before a call, its value is unspecified after the call.
.SH "RETURN VALUE"
Upon successful completion,
\fIungetwc\fR()
shall return the wide-character code corresponding to the pushed-back
character. Otherwise, it shall return WEOF.
.SH ERRORS
The
\fIungetwc\fR()
function may fail if:
.TP
.BR EILSEQ
An invalid character sequence is detected, or a wide-character code
does not correspond to a valid character.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "Section 2.5" ", " "Standard I/O Streams",
.IR "\fIfseek\fR\^(\|)",
.IR "\fIfsetpos\fR\^(\|)",
.IR "\fIread\fR\^(\|)",
.IR "\fIrewind\fR\^(\|)",
.IR "\fIsetbuf\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "\fB<stdio.h>\fP",
.IR "\fB<wchar.h>\fP"
.SH COPYRIGHT
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 .