xref: /freebsd/contrib/vis/vis.1 (revision 15fccd86b9dd17ca2cc1a70b060a2b1a1bf8470b)

.\"	$NetBSD: vis.1,v 1.25 2021/02/20 09:31:51 nia Exp $
.\"
.\" Copyright (c) 1989, 1991, 1993, 1994
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" 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.
.\"
.\"     @(#)vis.1	8.4 (Berkeley) 4/19/94
.\"
.Dd February 18, 2021
.Dt VIS 1
.Os
.Sh NAME
.Nm vis
.Nd display non-printable characters in a visual format
.Sh SYNOPSIS
.Nm
.Op Fl bcfhlMmNnoSstw
.Op Fl e Ar extra
.Op Fl F Ar foldwidth
.Op Ar file ...
.Sh DESCRIPTION
.Nm
is a filter for converting non-printable characters
into a visual representation.
It differs from
.Ql cat -v
in that
the form is unique and invertible.
By default, all non-graphic
characters except space, tab, and newline are encoded.
A detailed description of the
various visual formats is given in
.Xr vis 3 .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b
Turns off prepending of backslash before up-arrow control sequences
and meta characters, and disables the doubling of backslashes.
This
produces output which is neither invertible or precise, but does
represent a minimum of change to the input.
It is similar to
.Dq Li cat -v .
.Pq Dv VIS_NOSLASH
.It Fl c
Request a format which displays a small subset of the
non-printable characters using C-style backslash sequences.
.Pq Dv VIS_CSTYLE
.It Fl e Ar extra
Also encode characters in
.Ar extra ,
per
.Xr svis 3 .
.It Fl F Ar foldwidth
Causes
.Nm
to fold output lines to foldwidth columns (default 80), like
.Xr fold 1 ,
except
that a hidden newline sequence is used, (which is removed
when inverting the file back to its original form with
.Xr unvis 1 ) .
If the last character in the encoded file does not end in a newline,
a hidden newline sequence is appended to the output.
This makes
the output usable with various editors and other utilities which
typically don't work with partial lines.
.It Fl f
Same as
.Fl F .
.It Fl h
Encode using the URI encoding from RFC 1808.
.Pq Dv VIS_HTTPSTYLE
.It Fl l
Mark newlines with the visible sequence
.Ql \e$ ,
followed by the newline.
.It Fl M
Encode all shell meta characters (implies
.Fl S ,
.Fl w ,
.Fl g )
.Pq Dv VIS_META
.It Fl m
Encode using the MIME Quoted-Printable encoding from RFC 2045.
.Pq Dv VIS_MIMESTYLE
.It Fl N
Turn on the
.Dv VIS_NOLOCALE
flag which encodes using the
.Dq C
locale, removing any encoding dependencies caused by the current
locale settings specified in the environment.
.It Fl n
Turns off any encoding, except for the fact that backslashes are
still doubled and hidden newline sequences inserted if
.Fl f
or
.Fl F
is selected.
When combined with the
.Fl f
flag,
.Nm
becomes like
an invertible version of the
.Xr fold 1
utility.
That is, the output can be unfolded by running the output through
.Xr unvis 1 .
.It Fl o
Request a format which displays non-printable characters as
an octal number, \eddd.
.Pq Dv VIS_OCTAL
.It Fl S
Encode shell meta-characters that are non-white space or glob.
.Pq Dv VIS_SHELL
.It Fl s
Only characters considered unsafe to send to a terminal are encoded.
This flag allows backspace, bell, and carriage return in addition
to the default space, tab and newline.
.Pq Dv VIS_SAFE
.It Fl t
Tabs are also encoded.
.Pq Dv VIS_TAB
.It Fl w
White space (space-tab-newline) is also encoded.
.Pq Dv VIS_WHITE
.El
.Sh MULTIBYTE CHARACTER SUPPORT
.Nm
supports multibyte character input.
The encoding conversion is influenced by the setting of the
.Ev LC_CTYPE
environment variable which defines the set of characters that can be
copied without encoding.
.Pp
When 8-bit data is present in the input,
.Ev LC_CTYPE
must be set to the correct locale or to the C locale.
If the locales of the data and the conversion are mismatched, multibyte
character recognition may fail and encoding will be performed byte-by-byte
instead.
.Sh ENVIRONMENT
.Bl -tag -width ".Ev LC_CTYPE"
.It Ev LC_CTYPE
Specify the locale of the input data.
Set to C if the input data locale is unknown.
.El
.Sh EXAMPLES
Visualize characters encoding white spaces and tabs:
.Bd -literal -offset indent
$ echo -e "\\x10\\n\\t" | vis -w -t
\\^P\\012\\011\\012
.Ed
.Pp
Same as above but using `\\$' for newline followed by an actual newline:
.Bd -literal -offset indent
$ echo -e "\\x10\\n\\t" | vis -w -t -l
\\^P\\$
\\011\\$
.Ed
.Pp
Visualize string using URI encoding:
.Bd -literal -offset indent
$ echo http://www.freebsd.org | vis -h
http%3a%2f%2fwww.freebsd.org%0a
.Ed
.Sh SEE ALSO
.Xr unvis 1 ,
.Xr svis 3 ,
.Xr vis 3
.Sh HISTORY
The
.Nm
command appears in
.Bx 4.4 .
Multibyte character support was added in
.Nx 7.0
and
.Fx 9.2 .