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\"     @(#)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
$ printf "\\x10\\n\\t\\n" | 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
$ printf "\\x10\\n\\t\\n" | vis -w -t -l
\\^P\\$
\\011\\$
Ed
Pp
Visualize string using URI encoding:
Bd -literal -offset indent
$ printf https://www.NetBSD.org | vis -h
https%3a%2f%2fwww.NetBSD.org
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 .

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