tabsmell

#!/bin/bash
# Copyright © 2013 Vít Šesták <http://contact.v6ak.com>
# This work is free. It comes without any warranty, to the extent
# permitted by applicable law. You can redistribute it and/or modify it
# under the terms of the Do What The Fuck You Want To Public License,
# Version 2, as published by Sam Hocevar. See http://www.wtfpl.net/ for
# more details.
########################################################################
# Looks for bad usage of tab characters.
#
# It is OK when you use tabs for indentation, e.g.:
# GOOD tab practice:
#   <TAB>appendDup_X1(OBJECT, OBJECT)
#   <TAB>appendSwap(OBJECT, OBJECT)
#
# However, if you use a tab after a non-tab characted, it smells. It may break when you change tab size in your editor. For example:
# BAD tab practice:
#   <TAB>appendDup_X1(OBJECT, OBJECT)<TAB><TAB><TAB><TAB><TAB><TAB>// OS: r hu wv hu
#   <TAB>appendSwap(OBJECT, OBJECT)<TAB><TAB><TAB><TAB><TAB><TAB><TAB>// OS: r hu hu wv
# While this will look OK for tab size = 4, it can break for other tab sizes. So you should use spaces rather than tabs there.
#
# This script also detects bad tab and spaces mixing. It is expected that you use tabs for indentation.
# Any space used for indentation is considered as bad. For example:
# BAD tab practice:
#   <TAB>appendDup_X1(OBJECT, OBJECT)
#   <SPACE><SPACE>appendSwap(OBJECT, OBJECT)
# This works well if and only if tab size is exactly 2.
#
# All tabs on the output are replaced by red "<TAB>" text.
# Line numbers are added to the output.
# When you add multiple files, they all are checked. File names are also added to the output in such case.
########################################################################
grep -n -E $'([^\t]\t)|(^(\t*) )' "$@" | sed 's/\t/'`printf "\033[31m<TAB>\033[0m"`'/g'