#!/bin/sh

# Underlines non-printable characters in the input stream.
# Underlining is done by means of a line which is a sequence
# of spaces and '^'-characters.
#
# terminfo(5) is used to additionally highlight the underlined places.

STANDOUT="$(tput smso)"
offSTANDOUT="$(tput rmso)"

BOLD="$(tput bold)"
offBOLD="$(tput sgr0)"

#UNDERLINE="$(tput smul)"
#offUNDERLINE="$(tput rmul)"

sed -e "/[^[:print:]]/{ h; s/[^[:print:]]/$STANDOUT&$offSTANDOUT/g; 
                     p; g; s/[[:print:]]/ /g; s/[^[:print:]]/$BOLD^$offBOLD/g;
                      }"