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.TH UNGETWC 3C "Aug 14, 2002"
.SH NAME
ungetwc \- push wide-character code back into input stream
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>
#include <wchar.h>

\fBwint_t\fR \fBungetwc\fR(\fBwint_t\fR \fIwc\fR, \fBFILE *\fR\fIstream\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBungetwc()\fR function pushes the character corresponding to the wide
character code specified by \fIwc\fR back onto the input stream pointed to by
\fIstream\fR. The pushed-back characters will 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 \fIstream\fR) to a file-positioning
function ( \fBfseek\fR(3C), \fBfsetpos\fR(3C) or \fBrewind\fR(3C)) discards any
pushed-back characters for the stream. The external storage corresponding to
the stream is unchanged.
.sp
.LP
One character of push-back is guaranteed. If \fBungetwc()\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.
.sp
.LP
If the value of \fIwc\fR equals that of the macro \fBWEOF\fR, the operation
fails and the input stream is unchanged.
.sp
.LP
A successful call to \fBungetwc()\fR clears the end-of-file indicator for the
stream. The value of the file-position indicator for the stream after reading
or discarding all pushed-back characters will 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 \fBungetwc()\fR; if its value was 0 before
a call, its value is indeterminate after the call.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBungetwc()\fR returns the wide-character code
corresponding to the pushed-back character. Otherwise it returns \fBWEOF\fR.
.SH ERRORS
.sp
.LP
The \fBungetwc()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEILSEQ\fR\fR
.ad
.RS 10n
An invalid character sequence is detected, or a wide-character code does not
correspond to a valid character.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBread\fR(2), \fBfseek\fR(3C), \fBfsetpos\fR(3C), \fBrewind\fR(3C),
\fBsetbuf\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)