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258 lines
6.4 KiB
Groff
258 lines
6.4 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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.\" $Id: vis.3,v 1.1 1999/01/07 05:17:24 gdr-ftp Exp $
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.\"
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.TH VIS 3 "3 January 1999" GNO "Library Routines"
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.SH NAME
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.BR vis
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\- visually encode characters
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.SH SYNOPSIS
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.BR "#include <vis.h>"
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.sp 1
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char *\fBvis\fR
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.RI "(char *" dst ,
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.RI "int " c ,
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.RI "int " flag ,
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.RI "int " nextc );
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.br
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int
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.BR strvis
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.RI "(char *" dst ,
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.RI "const char *" src ,
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.RI "int " flag );
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.br
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int
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.BR strvisx
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.RI "(char *" dst ,
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.RI "const char *" src ,
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.RI "size_t " len ,
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.RI "int " flag );
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.SH DESCRIPTION
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The
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.BR vis
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function copies into
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.IR dst
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a string which represents the character
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.IR c .
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If
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.IR 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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NULL);
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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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NULL.
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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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.IR nextc ,
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is only used when selecting the
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.IR VIS_CSTYLE
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encoding format (explained below).
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.PP
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The
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.BR strvis
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and
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.BR strvisx
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functions copy into
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.IR dst
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a visual representation of
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the string
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.IR src .
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The
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.BR strvis
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function encodes characters from
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.IR src
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up to the
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first
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NULL.
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The
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.BR strvisx
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function encodes exactly
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.IR len
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characters from
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.IR 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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NULL's).
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Both forms
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NULL
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terminate
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.IR dst .
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The size of
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.IR dst
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must be four times the number
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of characters encoded from
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.IR src
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(plus one for the
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NULL).
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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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NULL).
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.PP
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The encoding is a unique, invertible representation comprised 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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.BR unvis (3)
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or
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.BR 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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.BR isgraph (3).)
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The following flags
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alter this:
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.IP VIS_SP
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Also encode space.
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.IP VIS_TAB
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Also encode tab.
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.IP VIS_NL
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Also encode newline.
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.IP VIS_WHITE
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Synonym for
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VIS_SP
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\&|
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VIS_TAB
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\&|
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VIS_NL .
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.IP 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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.PP
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There are three forms of encoding.
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All forms use the backslash character '\e' 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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.de zb
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.br
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.in +0.8i
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..
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.de ze
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.sp 1
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.in -0.8i
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..
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.IP (default)
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Use an '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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.BR ^
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to represent control characters see
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.BR iscntrl (3).
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The following formats are used:
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.sp 1
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\e^C
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.zb
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Represents the control character
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.BR C .
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Spans characters '\e000' through '\e037',
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and '\e177' (as '\e^?').
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.ze
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\eM-C
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.zb
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Represents character
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.RB ' C '
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with the 8th bit set.
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Spans characters '\e241'
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through '\e376'.
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.ze
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\eM^C
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.zb
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Represents control character
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.BR C
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with the 8th bit set.
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Spans characters '\e200' through '\e237', and '\e377' (as '\eM^?').
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.ze
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\e040
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.zb
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Represents ASCII space.
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.ze
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\e240
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.zb
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Represents Meta-space.
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.ze
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.IP 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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.nf
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\\a - BEL (007)
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\\b - BS (010)
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\\f - NP (014)
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\\n - NL (012)
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\\r - CR (015)
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\\t - HT (011)
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\\v - VT (013)
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\\0 - NULL (000)
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.fi
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.sp 1
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When using this format, the nextc parameter is looked at to determine
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if a NULL character can be encoded as '\\0' instead of '\\000'. If
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.IR 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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.IP VIS_OCTAL
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Use a three digit octal sequence. The form is '\\ddd' where
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.IR d
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represents an octal digit.
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.PP
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There is one additional flag,
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.IR 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 '^C'
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and meta characters as '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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.BR unvis (1),
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.BR strunvis (3),
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.BR unvis (3)
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.SH HISTORY
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These functions first appeared in 4.4BSD.
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