1.\" $OpenBSD: vis.1,v 1.16 2022/07/30 07:19:31 jsg Exp $ 2.\" $NetBSD: vis.1,v 1.5 1994/11/17 07:56:00 jtc Exp $ 3.\" 4.\" Copyright (c) 1989, 1991, 1993, 1994 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)vis.1 8.4 (Berkeley) 4/19/94 32.\" 33.Dd $Mdocdate: July 30 2022 $ 34.Dt VIS 1 35.Os 36.Sh NAME 37.Nm vis 38.Nd display non-printable characters in a visual format 39.Sh SYNOPSIS 40.Nm vis 41.Op Fl abcflnostw 42.Op Fl F Ar foldwidth 43.Op Ar 44.Sh DESCRIPTION 45.Nm 46is a filter for converting non-printable characters 47into a visual representation. 48It differs from 49.Ic cat -v 50in that 51the form can be unique and invertible. 52By default, all non-printing 53characters except space, tab, and newline are encoded, 54as are any meta-characters 55.Pq eighth bit set . 56A detailed description of the 57various visual formats is given in 58.Xr vis 3 . 59.Pp 60The options are as follows: 61.Bl -tag -width Ds 62.It Fl a 63Encode all characters, whether originally visible or not. 64.It Fl b 65Turns off prepending of backslash before up-arrow control sequences 66and meta-characters, and disables the doubling of backslashes. 67This produces output which is neither invertible nor precise, but does 68represent a minimum of change to the input. 69It is similar to 70.Ic cat -v . 71.It Fl c 72Request a format which displays a small subset of the 73non-printable characters using C-style backslash sequences. 74.It Fl F Ar foldwidth 75Causes 76.Nm 77to fold output lines to 78.Ar foldwidth 79columns, like 80.Xr fold 1 , 81except 82that a hidden newline sequence is used, (which is removed 83when inverting the file back to its original form with 84.Xr unvis 1 ) . 85If the last character in the encoded file does not end in a newline, 86a hidden newline sequence is appended to the output. 87This makes 88the output usable with various editors and other utilities which 89typically don't work with partial lines. 90.It Fl f 91Like 92.Fl F , 93except output is always folded to 80 columns. 94.It Fl l 95Mark newlines with the visible sequence 96.Ql \e$ , 97followed by the newline. 98.It Fl n 99Turns off any encoding, except for the fact that backslashes are 100still doubled and hidden newline sequences inserted if 101.Fl f 102or 103.Fl F 104is selected. 105When combined with the 106.Fl f 107flag, 108.Nm 109becomes like 110an invertible version of the 111.Xr fold 1 112utility. 113That is, the output 114can be unfolded by running the output through 115.Xr unvis 1 . 116.It Fl o 117Request a format which displays non-printable characters as 118an octal number, \eddd. 119.It Fl s 120Only characters considered unsafe to send to a terminal are encoded. 121This flag allows backspace, bell, and carriage return in addition 122to the default space, tab, and newline. 123Meta-characters that are considered graphic characters by 124.Xr isgraph 3 125are not encoded. 126.It Fl t 127Tabs are also encoded. 128.It Fl w 129White space (space-tab-newline) is also encoded. 130.El 131.Sh SEE ALSO 132.Xr unvis 1 , 133.Xr vis 3 134.Sh HISTORY 135The 136.Nm 137command appeared in 138.Bx 4.3 Reno . 139