freebsd-dev/lib/libc/stdio/ungetc.3

.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)ungetc.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dt UNGETC 3
.Os
.Sh NAME
.Nm ungetc
.Nd un-get character from input stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft int
.Fn ungetc "int c" "FILE *stream"
.Sh DESCRIPTION
The
.Fn ungetc
function pushes the character
.Fa c
(converted to an unsigned char)
back onto the input stream pointed to by
.Fa stream .
The pushed-back characters will be returned by subsequent reads on the
stream (in reverse order).
A successful intervening call,
using the same stream,
to one of the file positioning functions
.Xr ( fseek 3 ,
.Xr fsetpos 3 ,
or
.Xr rewind 3 )
will discard the pushed back characters.
.Pp
One character of push-back is guaranteed,
but as long as there is sufficient memory,
an effectively infinite amount of pushback is allowed.
.Pp
If a character is successfully pushed-back,
the end-of-file indicator for the stream is cleared.
The file-position indicator is decremented
by each successful call to
.Fn ungetc ;
if its value was 0 before a call, its value is unspecified after
the call.
.Sh RETURN VALUES
The
.Fn ungetc
function returns the character pushed-back after the conversion,
or
.Dv EOF
if the operation fails.
If the value of the argument
.Fa c
character equals
.Dv EOF ,
the operation will fail and the stream will remain unchanged.
.Sh SEE ALSO
.Xr fseek 3 ,
.Xr getc 3 ,
.Xr setvbuf 3 ,
.Xr ungetwc 3
.Sh STANDARDS
The
.Fn ungetc
function conforms to
.St -isoC .
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" Copyright (c) 1990, 1991, 1993`
			`.\" The Regents of the University of California. All rights reserved.`
			`.\"`
			`.\" This code is derived from software contributed to Berkeley by`
			`.\" Chris Torek and the American National Standards Committee X3,`
			`.\" on Information Processing Systems.`
			`.\"`
			`.\" Redistribution and use in source and binary forms, with or without`
			`.\" modification, are permitted provided that the following conditions`
			`.\" are met:`
			`.\" 1. Redistributions of source code must retain the above copyright`
			`.\" notice, this list of conditions and the following disclaimer.`
			`.\" 2. Redistributions in binary form must reproduce the above copyright`
			`.\" notice, this list of conditions and the following disclaimer in the`
			`.\" documentation and/or other materials provided with the distribution.`
Renumber copyright clause 4 Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96 2017-02-28 23:42:47 +00:00			`.\" 3. Neither the name of the University nor the names of its contributors`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" may be used to endorse or promote products derived from this software`
			`.\" without specific prior written permission.`
			`.\"`
			.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
			`.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE`
			`.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE`
			`.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE`
			`.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL`
			`.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS`
			`.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)`
			`.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT`
			`.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY`
			`.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF`
			`.\" SUCH DAMAGE.`
			`.\"`
			`.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\"`
			`.Dd June 4, 1993`
			`.Dt UNGETC 3`
			`.Os`
			`.Sh NAME`
			`.Nm ungetc`
			`.Nd un-get character from input stream`
Introduce ".Lb" macro to libc manpages. More libraries manpages updates following. 2000-04-21 09:42:15 +00:00			`.Sh LIBRARY`
			`.Lb libc`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SYNOPSIS`
mdoc(7) police: Use the new .In macro for #include statements. 2001-10-01 16:09:29 +00:00			`.In stdio.h`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Ft int`
			`.Fn ungetc "int c" "FILE *stream"`
			`.Sh DESCRIPTION`
			`The`
			`.Fn ungetc`
			`function pushes the character`
			`.Fa c`
			`(converted to an unsigned char)`
			`back onto the input stream pointed to by`
			`.Fa stream .`
Fix typo, reported by George Cox. Fix hard sentence breaks. Submitted by: George Cox <gjvc@sophos.com> 2000-04-12 13:38:26 +00:00			`The pushed-back characters will be returned by subsequent reads on the`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`stream (in reverse order).`
Fix typo, reported by George Cox. Fix hard sentence breaks. Submitted by: George Cox <gjvc@sophos.com> 2000-04-12 13:38:26 +00:00			`A successful intervening call,`
			`using the same stream,`
			`to one of the file positioning functions`
mdoc(7) police: Avoid using parenthesis enclosure macros (.Pq and .Po/.Pc) with plain text. Not only this slows down the mdoc(7) processing significantly, but it also has an undesired (in this case) effect of disabling hyphenation within the entire enclosed block. 2001-08-07 15:48:51 +00:00			`.Xr ( fseek 3 ,`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Xr fsetpos 3 ,`
			`or`
mdoc(7) police: Avoid using parenthesis enclosure macros (.Pq and .Po/.Pc) with plain text. Not only this slows down the mdoc(7) processing significantly, but it also has an undesired (in this case) effect of disabling hyphenation within the entire enclosed block. 2001-08-07 15:48:51 +00:00			`.Xr rewind 3 )`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`will discard the pushed back characters.`
			`.Pp`
			`One character of push-back is guaranteed,`
Fix typo, reported by George Cox. Fix hard sentence breaks. Submitted by: George Cox <gjvc@sophos.com> 2000-04-12 13:38:26 +00:00			`but as long as there is sufficient memory,`
			`an effectively infinite amount of pushback is allowed.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Pp`
			`If a character is successfully pushed-back,`
			`the end-of-file indicator for the stream is cleared.`
Describe file-position behaviour from POSIX 2001-09-01 14:01:52 +00:00			`The file-position indicator is decremented`
			`by each successful call to`
			`.Fn ungetc ;`
			`if its value was 0 before a call, its value is unspecified after`
			`the call.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh RETURN VALUES`
			`The`
			`.Fn ungetc`
Fix typo, reported by George Cox. Fix hard sentence breaks. Submitted by: George Cox <gjvc@sophos.com> 2000-04-12 13:38:26 +00:00			`function returns the character pushed-back after the conversion,`
			`or`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Dv EOF`
			`if the operation fails.`
			`If the value of the argument`
			`.Fa c`
			`character equals`
Back out disabling ungetc() at 0, use different solution: keep negative offset internally, but return 0 externally in ftell*() I.e. use 0 now as 'unspecified value' per POSIX ungetc() description. 2001-09-01 01:56:54 +00:00			`.Dv EOF ,`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`the operation will fail and the stream will remain unchanged.`
			`.Sh SEE ALSO`
			`.Xr fseek 3 ,`
Sort cross references. 1997-01-20 23:23:22 +00:00			`.Xr getc 3 ,`
Cross-reference between byte and wide-character stdio functions. Remove references to fputwc() and fgetwc() being macros while I'm at it. 2002-10-10 04:12:40 +00:00			`.Xr setvbuf 3 ,`
			`.Xr ungetwc 3`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh STANDARDS`
			`The`
			`.Fn ungetc`
			`function conforms to`
.St -ansiC -> .St -isoC 2001-02-26 13:23:47 +00:00			`.St -isoC .`