Colouring a text file to highlight spaces, tabs, etc. See also cat -A

colouredtabs.sh

#!/bin/bash

RED=`echo -e '\033[41m\033[37m'`
BLUE=`echo -e '\033[44m\033[37m'`
NORMAL=`echo -e '\033[0m'`

cat "$1" | sed -e s/\ /${BLUE}\ ${NORMAL}/g | sed -e s/$'\t'/${RED}\ \ \ \ ${NORMAL}/g

Unfortunately doesn't play well with "less" (shows control chars) or "more" (shows blue spaces wrapping round entire lines, in some cases)

Solved: pipe the output to "less -R", which preserves the colour escape sequences