NAME

vis, inv − make unprintable 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 into a visible form.  inv performs the inverse function, reading printable characters from each file, returning them to non-printable form, if appropriate, then writing them to standard output;

Non-printable 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 8-bit character whose ASCII code is the 3-digit octal number n.

\xn the 8-bit character whose ASCII code 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 characters 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 (character-by-character); 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. 

AUTHOR

vis was developed by HP. 

SEE ALSO

cat(1), echo(1), od(1). 

WARNINGS

Redirecting output to an input file destroys the original data.  Therefore, command forms such as

vis file1 file2 >file1

should be avoided unless the source file can be safely discarded. 

Hewlett-Packard Company  —  HP-UX Release 9.0: August 1992