NAME
vis —
display non-printable characters in a
visual format
SYNOPSIS
vis |
[-abcfhlMmNnoSstw] [-e
extra] [-F
foldwidth] [file ...] |
DESCRIPTION
vis is a filter for converting non-printable characters
into a visual representation. It differs from ‘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
vis(3).
The options are as follows:
-a- Encode all characters, whether originally visible or not.
(
VIS_ALL) -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
“
cat -v”. (VIS_NOSLASH) -c- Request a format which displays a small subset of the non-printable
characters using C-style backslash sequences.
(
VIS_CSTYLE) -eextra- Also encode characters in extra, per svis(3).
-Ffoldwidth- Causes
visto fold output lines to foldwidth columns (default 80), like fold(1), except that a hidden newline sequence is used, (which is removed when inverting the file back to its original form with 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. -f- Same as
-F. -h- Encode using the URI encoding from RFC 1808.
(
VIS_HTTPSTYLE) -l- Mark newlines with the visible sequence
‘
\$’, followed by the newline. -M- Encode all shell meta characters (implies
-S,-w,-g) (VIS_META) -m- Encode using the MIME Quoted-Printable encoding from RFC 2045.
(
VIS_MIMESTYLE) -N- Turn on the
VIS_NOLOCALEflag which encodes using the “C” locale, removing any encoding dependencies caused by the current locale settings specified in the environment. -n- Turns off any encoding, except for the fact that backslashes are still
doubled and hidden newline sequences inserted if
-for-Fis selected. When combined with the-fflag,visbecomes like an invertible version of the fold(1) utility. That is, the output can be unfolded by running the output through unvis(1). -o- Request a format which displays non-printable characters as an octal
number, \ddd. (
VIS_OCTAL) -S- Encode shell meta-characters that are non-white space or glob.
(
VIS_SHELL) -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. (
VIS_SAFE) -t- Tabs are also encoded. (
VIS_TAB) -w- White space (space-tab-newline) is also encoded.
(
VIS_WHITE)
MULTIBYTE CHARACTER SUPPORT
vis supports multibyte character input.
The encoding conversion is influenced by the setting of the
LC_CTYPE environment variable which defines the set
of characters that can be copied without encoding.
When 8-bit data is present in the input,
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.
ENVIRONMENT
LC_CTYPE- Specify the locale of the input data. Set to C if the input data locale is unknown.
SEE ALSO
HISTORY
The vis command appeared in
4.4BSD. Multibyte character support was added in
NetBSD 7.0 and FreeBSD
9.2.