diff-kernel-configs

#!/bin/bash -eu
#
# Diff two or more kernel config files
#

function read_configfile()
{
	local array=${1} configfile=${2}
	local line config val

	while IFS= read -r line ; do
		case "${line}" in
			"# CONFIG_"*)
				config=${line#\# CONFIG_}
				config=${config%% *}
				val="n"
				;;
			"CONFIG_"*)
				config=${line#CONFIG_}
				config=${config%%=*}
				val=${line#*=}
				;;
			*)
				continue
				;;
		esac
		eval "${array}[${config}]=${val}"
	done < <(cat "${configfile}")
}

function usage()
{
	cat <<EOF
Usage: diff-kernel-configs [-d] [-h] CONFIGFILE CONFIGFILE [CONFIGFILE...]

Diff two or more kernel config files.

Optional arguments:
  -d. --diff-only  Only show differences.
  -h, --help       Show this help text and exit.
EOF
}

diff_only=0
files=()

while [ $# -gt 0 ] ; do
	case "${1}" in
		-d|--diff-only)
			diff_only=1
			;;
		-h|--help)
			usage
			exit
			;;
		-*)
			echo "Invalid argument: ${1}" >&2
			exit 2
			;;
		*)
			if ! [ -f "${1}" ] ; then
				echo "No such file: ${1}" >&2
				exit 1
			fi
			files+=("${1}")
			;;
	esac
	shift
done

if [ ${#files[@]} -lt 2 ] ; then
	usage
	exit 2
fi

# Read the configs files into associative arrays
for i in $(seq 0 $((${#files[@]} - 1))) ; do
	declare -A "CONFIGS_${i}"
	read_configfile "CONFIGS_${i}" "${files[${i}]}"
done

# Print a header line
printf "%-40s" "CONFIG"
for f in "${files[@]}" ; do
	printf "%-40s" "${f::39}"
done
printf "\n"


# Print the config values
while IFS= read -r line ; do
	config=${line#*CONFIG_}
	config=${config%% *}
	config=${config%%=*}

	# first value (reference)
	ref_val=${CONFIGS_0[${config}]}

	diff=0
	line=$(printf "%-40s%-40s" "${config}" "${ref_val}")
	for i in $(seq 1 $((${#files[@]} - 1))) ; do
		var=CONFIGS_${i}[${config}]
		val="${!var:--}"
		if [ "${val}" = "${ref_val}" ] ; then
			color="\e[32m"  # green
		else
			diff=1
			color="\e[93m"  # orange
		fi
		line=${line}$(printf "%-49s" "$(echo -e "${color}${val}\e[0m")")
	done
	if [ ${diff_only} -eq 0 ] || [ ${diff} -eq 1 ]  ; then
		echo "${line}"
	fi

done < <(grep -P '^(# )?CONFIG_' "${files[0]}")