VIS(1)

NAME
vis - display non-printable characters in a visual format

SYNOPSIS
vis [-cbflnostw] [-F foldwidth] [file ...]

DESCRIPTION
The vis utility 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:

-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”.

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

-F  Causes vis to 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 do not work with partial lines.

-f  Same as -F.

-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.

-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.

BUGS
Due to limitations in the underlying vis(3) function, the vis utility does not recognize multibyte characters, and thus may consider them to be non-printable when they are in fact printable (and vice versa).