1.\" $NetBSD: vis.1,v 1.23 2015/05/24 19:42:39 christos Exp $ 2.\" 3.\" Copyright (c) 1989, 1991, 1993, 1994 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)vis.1 8.4 (Berkeley) 4/19/94 31.\" 32.Dd April 11, 2018 33.Dt VIS 1 34.Os 35.Sh NAME 36.Nm vis 37.Nd display non-printable characters in a visual format 38.Sh SYNOPSIS 39.Nm 40.Op Fl bcfhlMmNnoSstw 41.Op Fl e Ar extra 42.Op Fl F Ar foldwidth 43.Op Ar file ... 44.Sh DESCRIPTION 45.Nm 46is a filter for converting non-printable characters 47into a visual representation. 48It differs from 49.Ql cat -v 50in that 51the form is unique and invertible. 52By default, all non-graphic 53characters except space, tab, and newline are encoded. 54A detailed description of the 55various visual formats is given in 56.Xr vis 3 . 57.Pp 58The options are as follows: 59.Bl -tag -width Ds 60.It Fl b 61Turns off prepending of backslash before up-arrow control sequences 62and meta characters, and disables the doubling of backslashes. 63This 64produces output which is neither invertible or precise, but does 65represent a minimum of change to the input. 66It is similar to 67.Dq Li cat -v . 68.Pq Dv VIS_NOSLASH 69.It Fl c 70Request a format which displays a small subset of the 71non-printable characters using C-style backslash sequences. 72.Pq Dv VIS_CSTYLE 73.It Fl e Ar extra 74Also encode characters in 75.Ar extra , 76per 77.Xr svis 3 . 78.It Fl F Ar foldwidth 79Causes 80.Nm 81to fold output lines to foldwidth columns (default 80), like 82.Xr fold 1 , 83except 84that a hidden newline sequence is used, (which is removed 85when inverting the file back to its original form with 86.Xr unvis 1 ) . 87If the last character in the encoded file does not end in a newline, 88a hidden newline sequence is appended to the output. 89This makes 90the output usable with various editors and other utilities which 91typically don't work with partial lines. 92.It Fl f 93Same as 94.Fl F . 95.It Fl h 96Encode using the URI encoding from RFC 1808. 97.Pq Dv VIS_HTTPSTYLE 98.It Fl l 99Mark newlines with the visible sequence 100.Ql \e$ , 101followed by the newline. 102.It Fl M 103Encode all shell meta characters (implies 104.Fl S , 105.Fl w , 106.Fl g ) 107.Pq Dv VIS_META 108.It Fl m 109Encode using the MIME Quoted-Printable encoding from RFC 2045. 110.Pq Dv VIS_MIMESTYLE 111.It Fl N 112Turn on the 113.Dv VIS_NOLOCALE 114flag which encodes using the 115.Dq C 116locale, removing any encoding dependencies caused by the current 117locale settings specified in the environment. 118.It Fl n 119Turns off any encoding, except for the fact that backslashes are 120still doubled and hidden newline sequences inserted if 121.Fl f 122or 123.Fl F 124is selected. 125When combined with the 126.Fl f 127flag, 128.Nm 129becomes like 130an invertible version of the 131.Xr fold 1 132utility. 133That is, the output can be unfolded by running the output through 134.Xr unvis 1 . 135.It Fl o 136Request a format which displays non-printable characters as 137an octal number, \eddd. 138.Pq Dv VIS_OCTAL 139.It Fl S 140Encode shell meta-characters that are non-white space or glob. 141.Pq Dv VIS_SHELL 142.It Fl s 143Only characters considered unsafe to send to a terminal are encoded. 144This flag allows backspace, bell, and carriage return in addition 145to the default space, tab and newline. 146.Pq Dv VIS_SAFE 147.It Fl t 148Tabs are also encoded. 149.Pq Dv VIS_TAB 150.It Fl w 151White space (space-tab-newline) is also encoded. 152.Pq Dv VIS_WHITE 153.El 154.Sh MULTIBYTE CHARACTER SUPPORT 155.Nm 156supports multibyte character input. 157The encoding conversion is influenced by the setting of the 158.Ev LC_CTYPE 159environment variable which defines the set of characters that can be 160copied without encoding. 161.Pp 162When 8-bit data is present in the input, 163.Ev LC_CTYPE 164must be set to the correct locale or to the C locale. 165If the locales of the data and the conversion are mismatched, multibyte 166character recognition may fail and encoding will be performed byte-by-byte 167instead. 168.Sh ENVIRONMENT 169.Bl -tag -width ".Ev LC_CTYPE" 170.It Ev LC_CTYPE 171Specify the locale of the input data. 172Set to C if the input data locale is unknown. 173.El 174.Sh SEE ALSO 175.Xr unvis 1 , 176.Xr svis 3 , 177.Xr vis 3 178.Sh HISTORY 179The 180.Nm 181command appeared in 182.Bx 4.4 . 183Multibyte character support was added in 184.Nx 7.0 185and 186.Fx 9.2 . 187