103 lines
3.2 KiB
Groff
103 lines
3.2 KiB
Groff
.\" $NetBSD: ungetc.3,v 1.10 2010/04/30 05:56:14 jruoho Exp $
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.\"
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.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd April 30, 2010
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.Dt UNGETC 3
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.Os
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.Sh NAME
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.Nm ungetc
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.Nd un-get character from input stream
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdio.h
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.Ft int
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.Fn ungetc "int c" "FILE *stream"
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.Sh DESCRIPTION
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The
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.Fn ungetc
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function pushes the character
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.Fa c
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(converted to an unsigned char)
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back onto the input stream pointed to by
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.Fa stream .
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The pushed-backed characters will be returned by subsequent reads on the
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stream (in reverse order).
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A successful intervening call, using the same stream, to one of the file
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positioning functions
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.Po
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.Xr fseek 3 ,
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.Xr fsetpos 3 ,
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or
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.Xr rewind 3
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.Pc
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will discard the pushed back characters.
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.Pp
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One character of push-back is guaranteed,
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but as long as there is
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sufficient memory, an effectively infinite amount of pushback is allowed.
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.Pp
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If a character is successfully pushed-back,
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the end-of-file indicator for the stream is cleared.
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.Sh RETURN VALUES
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The
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.Fn ungetc
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function
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returns
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the character pushed-back after the conversion, or
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.Dv EOF
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if the operation fails.
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If the value of the argument
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.Fa c
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character equals
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.Dv EOF ,
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the operation will fail and the stream will remain unchanged.
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.Sh SEE ALSO
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.Xr fseek 3 ,
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.Xr getc 3 ,
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.Xr setvbuf 3
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.Sh STANDARDS
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The
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.Fn ungetc
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function conforms to
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.St -ansiC
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and
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.St -p1003.1-2001 .
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.Sh HISTORY
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An
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.Fn ungetc
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function appeared in
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.At v7 .
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