mirror of https://github.com/mkerrisk/man-pages
88 lines
3.0 KiB
Plaintext
88 lines
3.0 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "UNGETWC" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" ungetwc
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.SH NAME
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ungetwc \- push wide-character code back into the input stream
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.SH SYNOPSIS
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.LP
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\fB#include <stdio.h>
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.br
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#include <wchar.h>
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.br
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.sp
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wint_t ungetwc(wint_t\fP \fIwc\fP\fB, FILE *\fP\fIstream\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIungetwc\fP() function shall push the character corresponding
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to the wide-character code specified by \fIwc\fP back onto
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the input stream pointed to by \fIstream\fP. The pushed-back characters
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shall be returned by subsequent reads on that stream in
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the reverse order of their pushing. A successful intervening call
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(with the stream pointed to by \fIstream\fP) to a
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file-positioning function ( \fIfseek\fP(), \fIfsetpos\fP(), or \fIrewind\fP())
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discards any
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pushed-back characters for the stream. The external storage corresponding
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to the stream is unchanged.
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.LP
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At least one character of push-back shall be provided. If \fIungetwc\fP()
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is called too many times on the same stream without
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an intervening read or file-positioning operation on that stream,
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the operation may fail.
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.LP
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If the value of \fIwc\fP equals that of the macro WEOF, the operation
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shall fail and the input stream shall be left
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unchanged.
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.LP
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A successful call to \fIungetwc\fP() shall clear the end-of-file indicator
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for the stream. The value of the file-position
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indicator for the stream after reading or discarding all pushed-back
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characters shall be the same as it was before the characters
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were pushed back. The file-position indicator is decremented (by one
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or more) by each successful call to \fIungetwc\fP(); if its
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value was 0 before a call, its value is unspecified after the call.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fIungetwc\fP() shall return the wide-character
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code corresponding to the pushed-back character.
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Otherwise, it shall return WEOF.
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.SH ERRORS
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.LP
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The \fIungetwc\fP() function may fail if:
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.TP 7
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.B EILSEQ
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An
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invalid character sequence is detected, or a wide-character code does
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not correspond to a valid character.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIfseek\fP() , \fIfsetpos\fP() , \fIread\fP() ,
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\fIrewind\fP() , \fIsetbuf\fP() , the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, \fI<stdio.h>\fP, \fI<wchar.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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