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NAME

vis — display non-printable characters in a visual format

SYNOPSIS

DESCRIPTION

vis is a filter for converting non-printable characters into a visual representation. It differs from cat -v in that the form can be unique and invertible. By default, all non-printing characters except space, tab, and newline are encoded, as are any meta-characters (eighth bit set). 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.

-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 nor precise, but does represent a minimum of change to the input. It is similar to cat -v.

-c

Request a format which displays a small subset of the non-printable characters using C-style backslash sequences.

-F foldwidth

Causes vis to fold output lines to foldwidth columns, 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

Like -F, except output is always folded to 80 columns.

-l

Mark newlines with the visible sequence ‘\$’, followed by the newline.

-n

Turns off any encoding, except for the fact that backslashes are still doubled and hidden newline sequences inserted if -f or -F is selected. When combined with the -f flag, vis becomes 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.

-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. Meta-characters that are considered graphic characters by isgraph(3) are not encoded.

-t

Tabs are also encoded.

-w

White space (space-tab-newline) is also encoded.

SEE ALSO

unvis(1), vis(3)

HISTORY

The vis command appeared in 4.4BSD.