NAME
vis, inv — make unprintable and non-ASCII characters in a file visible or invisible
SYNOPSIS
vis
[-n]
[-s]
[-t]
[-u]
[-x]
file ...
inv
[-n]
[-s]
[-t]
[-u]
[-x]
file ...
DESCRIPTION
vis
reads characters from each
file
in sequence and writes them to the standard output,
converting those that are not printable or not ASCII into a visible form.
inv
performs the inverse function, reading printable characters from each
file,
returning them to non-printable or non-ASCII form, if appropriate,
then writing them to standard output;
Non-printable ASCII characters are represented using C-like escape conventions:
- \\
backslash
- \b
backspace
- \e
escape
- \f
form-feed
- \n
new-line
- \r
carriage return
- \s
space
- \t
horizontal tab
- \v
vertical tab
- \n
the character whose
ASCII
code is the 3-digit octal number
n.
- \xn
the character whose
ASCII
code is the 2-digit hexadecimal number
n.
Non-ASCII single- or multi-byte characters are examined one byte at a time.
For each byte, if it can be displayed as an ASCII character,
it is treated as if it is an ASCII character;
Otherwise, it is represented in the following conventions:
- \n
the 8-bit character whose
code value is the 3-digit octal number
n.
- \xn
the 8-bit character whose
code value is the 2-digit hexadecimal number
n.
Space, horizontal-tab, and new-line characters
can be treated as printable
(and therefore passed unaltered to the output)
or non-printable depending on the options selected.
Backslash, although printable, is expanded by
vis,
to a pair of backslashes so that when they are passed back through
inv,
they convert back to a single backslash.
If no input file is given, or if the argument
-
is encountered,
vis
and
inv
read from the standard input.
Options
vis
and
inv
recognize the following options:
- -n
Treat new-line, space, and horizontal tab as non-printable characters.
vis
expands them visibly as
\n,
\s,
and
\t,
rather than passing them directly to the output.
inv
discards these characters,
expecting only the printable expansions.
New-line characters are inserted by
vis
every 16 bytes so that the output
will be in a form that is usable by most editors.
- -s
Make
vis
and
inv
silent about non-existent files,
identical input and output, and write errors.
Normally, no input file can be the same as the output file
unless it is a special file.
- -t
Treat horizontal-tab and space characters as non-printable
in the same manner that
-n
treats them.
- -u
Cause output to be unbuffered (byte-by-byte);
normally, output is buffered.
- -x
Cause
vis
output to be in hexadecimal form rather than the default octal form.
Either form is accepted to
inv
as input.
EXTERNAL INFLUENCES
Environment Variables
LANG
determines the language in which messages are displayed.
International Code Set Support
Single- and multi-byte character code sets are supported.
WARNINGS
Redirecting output to an input file destroys the original data.
Therefore, command forms such as
should be avoided unless the source file can be safely discarded.
AUTHOR
vis
was developed by HP.
Printable version
