1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
266 lines
6.5 KiB
Groff
266 lines
6.5 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" From: @(#)vis.3 8.1 (Berkeley) 6/9/93
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.\" $FreeBSD$
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.\"
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.Dd July 25, 1996
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.Dt VIS 3
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.Os
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.Sh NAME
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.Nm vis
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.Nd visually encode characters
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.Sh SYNOPSIS
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.Fd #include <vis.h>
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.Ft char *
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.Fn vis "char *dst" "char c" "int flag" "char nextc"
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.Ft int
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.Fn strvis "char *dst" "char *src" "int flag"
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.Ft int
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.Fn strvisx "char *dst" "char *src" "int len" "int flag"
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.Sh DESCRIPTION
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The
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.Fn vis
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function
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copies into
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.Fa dst
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a string which represents the character
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.Fa c .
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If
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.Fa c
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needs no encoding, it is copied in unaltered. The string is
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null terminated, and a pointer to the end of the string is
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returned. The maximum length of any encoding is four
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characters (not including the trailing
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.Dv NUL ) ;
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thus, when
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encoding a set of characters into a buffer, the size of the buffer should
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be four times the number of characters encoded, plus one for the trailing
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.Dv NUL .
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The flag parameter is used for altering the default range of
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characters considered for encoding and for altering the visual
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representation.
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The additional character,
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.Fa nextc ,
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is only used when selecting the
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.Dv VIS_CSTYLE
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encoding format (explained below).
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.Pp
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The
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.Fn strvis
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and
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.Fn strvisx
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functions copy into
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.Fa dst
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a visual representation of
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the string
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.Fa src .
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The
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.Fn strvis
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function encodes characters from
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.Fa src
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up to the
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first
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.Dv NUL .
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The
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.Fn strvisx
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function encodes exactly
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.Fa len
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characters from
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.Fa src
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(this
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is useful for encoding a block of data that may contain
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.Dv NUL Ns 's).
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Both forms
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.Dv NUL
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terminate
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.Fa dst .
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The size of
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.Fa dst
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must be four times the number
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of characters encoded from
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.Fa src
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(plus one for the
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.Dv NUL ) .
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Both
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forms return the number of characters in dst (not including
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the trailing
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.Dv NUL ) .
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.Pp
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The encoding is a unique, invertible representation composed entirely of
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graphic characters; it can be decoded back into the original form using
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the
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.Xr unvis 3
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or
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.Xr strunvis 3
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functions.
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.Pp
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There are two parameters that can be controlled: the range of
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characters that are encoded, and the type
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of representation used.
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By default, all non-graphic characters.
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except space, tab, and newline are encoded.
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(See
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.Xr isgraph 3 . )
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The following flags
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alter this:
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.Bl -tag -width VIS_WHITEX
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.It Dv VIS_SP
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Also encode space.
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.It Dv VIS_TAB
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Also encode tab.
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.It Dv VIS_NL
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Also encode newline.
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.It Dv VIS_WHITE
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Synonym for
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.Dv VIS_SP
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\&|
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.Dv VIS_TAB
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\&|
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.Dv VIS_NL .
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.It Dv VIS_SAFE
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Only encode "unsafe" characters. Unsafe means control
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characters which may cause common terminals to perform
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unexpected functions. Currently this form allows space,
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tab, newline, backspace, bell, and return - in addition
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to all graphic characters - unencoded.
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.El
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.Pp
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There are three forms of encoding.
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All forms use the backslash character
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.Ql \e
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to introduce a special
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sequence; two backslashes are used to represent a real backslash.
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These are the visual formats:
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.Bl -tag -width VIS_CSTYLE
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.It (default)
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Use an
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.Ql M
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to represent meta characters (characters with the 8th
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bit set), and use carat
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.Ql ^
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to represent control characters see
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.Pf ( Xr iscntrl 3 ) .
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The following formats are used:
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.Bl -tag -width xxxxx
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.It Dv \e^C
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Represents the control character
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.Ql C .
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Spans characters
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.Ql \e000
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through
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.Ql \e037 ,
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and
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.Ql \e177
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(as
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.Ql \e^? ) .
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.It Dv \eM-C
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Represents character
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.Ql C
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with the 8th bit set.
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Spans characters
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.Ql \e241
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through
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.Ql \e376 .
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.It Dv \eM^C
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Represents control character
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.Ql C
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with the 8th bit set.
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Spans characters
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.Ql \e200
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through
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.Ql \e237 ,
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and
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.Ql \e377
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(as
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.Ql \eM^? ) .
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.It Dv \e040
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Represents
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.Tn ASCII
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space.
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.It Dv \e240
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Represents Meta-space.
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.El
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.Pp
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.It Dv VIS_CSTYLE
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Use C-style backslash sequences to represent standard non-printable
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characters.
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The following sequences are used to represent the indicated characters:
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.Bd -unfilled -offset indent
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.Li \ea Tn - BEL No (007)
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.Li \eb Tn - BS No (010)
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.Li \ef Tn - NP No (014)
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.Li \en Tn - NL No (012)
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.Li \er Tn - CR No (015)
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.Li \et Tn - HT No (011)
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.Li \ev Tn - VT No (013)
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.Li \e0 Tn - NUL No (000)
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.Ed
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.Pp
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When using this format, the nextc parameter is looked at to determine
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if a
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.Dv NUL
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character can be encoded as
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.Ql \e0
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instead of
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.Ql \e000 .
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If
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.Fa nextc
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is an octal digit, the latter representation is used to
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avoid ambiguity.
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.It Dv VIS_OCTAL
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Use a three digit octal sequence. The form is
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.Ql \eddd
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where
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.Em d
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represents an octal digit.
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.El
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.Pp
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There is one additional flag,
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.Dv VIS_NOSLASH ,
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which inhibits the
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doubling of backslashes and the backslash before the default
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format (that is, control characters are represented by
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.Ql ^C
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and
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meta characters as
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.Ql M-C ) .
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With this flag set, the encoding is
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ambiguous and non-invertible.
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.Sh SEE ALSO
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.Xr unvis 1 ,
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.Xr strunvis 3 ,
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.Xr unvis 3
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.Sh HISTORY
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These functions first appeared in
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.Bx 4.4 .
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