diff --git a/checksum_file.sh b/checksum_file.sh
index bda0e0c..e1c228e 100755
--- a/checksum_file.sh
+++ b/checksum_file.sh
@@ -208,7 +208,7 @@ esac
 case ${ACTION} in
 ####### GET
 	get)
-	CHECKSUM_S=$(_get "$FILE")
+	CHECKSUM_S=$(_get "${FILE}")
 	
 	# Did we find a checksum?
 	if [ -n "${CHECKSUM_S}" ]; then
@@ -221,13 +221,13 @@ case ${ACTION} in
 
 ####### SET
 	set)
-	_set "$FILE" || \
+	_set "${FILE}" || \
 		do_log "ERROR: failed to set user.checksum.${DIGEST} for file ${FILE}!" 1
 	;;
 
 ####### GET-SET)
 	get-set)
-	CHECKSUM_S=$(_get "$FILE")
+	CHECKSUM_S=$(_get "${FILE}")
 	
 	# Did we find a checksum?
 	if [ -n "${CHECKSUM_S}" ]; then
@@ -235,28 +235,28 @@ case ${ACTION} in
 		echo "user.checksum.${DIGEST}: ${CHECKSUM_S}"
 	else
 		# Set checksum
-		_set "$FILE"
+		_set "${FILE}"
 	fi
 	;;
 		
 ####### CHECK-SET
 	check-set)
-	CHECKSUM_S=$(_get "$FILE")
+	CHECKSUM_S=$(_get "${FILE}")
 	
 	# Did we find a checksum?
 	if [ -n "${CHECKSUM_S}" ]; then
 		# Verify checksum
-		$0 check "$FILE"				# Calling ourselves!
+		$0 check "${FILE}"				# Calling ourselves!
 	else
 		# Set checksum
-		_set "$FILE"
+		_set "${FILE}"
 	fi
 	;;
 
 ####### CHECK
 	check)
-	CHECKSUM_C=$(_calc "$FILE")
-	CHECKSUM_S=$(_get  "$FILE")
+	CHECKSUM_C=$(_calc "${FILE}")
+	CHECKSUM_S=$(_get  "${FILE}")
 
 	# Bail out if there is no checksum to compare
 	[ -z  "${CHECKSUM_C}" ] || [ -z "${CHECKSUM_S}" ] && \
@@ -277,23 +277,23 @@ case ${ACTION} in
 	echo "Removing user.checksum.${DIGEST} from ${FILE}..."
 	case ${OS} in
 		Darwin)
-		xattr -d user.checksum.${DIGEST} "$FILE"
+		xattr -d user.checksum.${DIGEST} "${FILE}"
 		;;
 
 		FreeBSD)
-		pxattr -x user.checksum.${DIGEST} "$FILE"
+		pxattr -x user.checksum.${DIGEST} "${FILE}"
 		;;
 
 		NetBSD)
-		rmextattr user checksum.${DIGEST} "$FILE"
+		rmextattr user checksum.${DIGEST} "${FILE}"
 		;;
 
 		Linux)
-		setfattr --remove user.checksum.${DIGEST} -- "$FILE"
+		setfattr --remove user.checksum.${DIGEST} -- "${FILE}"
 		;;
 
 		SunOS)
-		runat "$FILE" rm user.checksum.${DIGEST}
+		runat "${FILE}" rm user.checksum.${DIGEST}
 		;;
 
 		*)
@@ -306,9 +306,9 @@ case ${ACTION} in
 	test)
 	# We need a temporary file, even on macOS
 	TEMP=$(mktemp -p . 2>/dev/null || mktemp ./tmp.XXXXXXX 2>/dev/null)
-	trap "rm -f $TEMP" EXIT INT TERM HUP
+	trap "rm -f ${TEMP}" EXIT INT TERM HUP
 
-	if [ ! -f "$TEMP" ]; then
+	if [ ! -f "${TEMP}" ]; then
 		do_log "Failed to create temporary file ${TEMP}!" 1
 	else
 		date > "${TEMP}"
diff --git a/convert-music.sh b/convert-music.sh
index 9094d39..d401872 100755
--- a/convert-music.sh
+++ b/convert-music.sh
@@ -19,7 +19,7 @@ if [ ! $# -eq 2 ] || [ ! -f "$2" ]; then
 else
 	CONVERSION="$1"
 	FILE="$2"
-	PATH=$PATH:/opt/lame/bin
+	PATH=${PATH}:/opt/lame/bin
 fi
 
 # LAME defaults
@@ -33,18 +33,18 @@ fi
 # --pad-id3v2		- ?
 LAMEARGS="-m j -q 5 --vbr-new -V 4 -s 44.1 --add-id3v2 --ignore-tag-errors"
 
-case $CONVERSION in
+case ${CONVERSION} in
 	flac2mp3)
 	# Convert FLAC to MP3
 	# https://wiki.archlinux.org/index.php/Convert_FLAC_to_MP3
 	# Software needed: flac, lame
 	OUTPUT=${FILE%.flac}.mp3
-	 TRACK=$(metaflac --show-tag=TRACKNUMBER "$FILE" | sed s/.*=//)
-	 TITLE=$(metaflac --show-tag=TITLE  "$FILE" | sed s/.*=//)
-	ARTIST=$(metaflac --show-tag=ARTIST "$FILE" | sed s/.*=//)
-	 ALBUM=$(metaflac --show-tag=ALBUM  "$FILE" | sed s/.*=//)
-	  DATE=$(metaflac --show-tag=DATE   "$FILE" | sed s/.*=//)
-	 GENRE=$(metaflac --show-tag=GENRE  "$FILE" | sed s/.*=//)
+	 TRACK=$(metaflac --show-tag=TRACKNUMBER "${FILE}" | sed s/.*=//)
+	 TITLE=$(metaflac --show-tag=TITLE  "${FILE}" | sed s/.*=//)
+	ARTIST=$(metaflac --show-tag=ARTIST "${FILE}" | sed s/.*=//)
+	 ALBUM=$(metaflac --show-tag=ALBUM  "${FILE}" | sed s/.*=//)
+	  DATE=$(metaflac --show-tag=DATE   "${FILE}" | sed s/.*=//)
+	 GENRE=$(metaflac --show-tag=GENRE  "${FILE}" | sed s/.*=//)
 	#
 	# lame options:
 	# -m j		joint stereo
@@ -54,46 +54,46 @@ case $CONVERSION in
 	# -s 44.1	sampling frequency
 	#
 	# Note: if GENRE is empty, use "12" (other). If TRACKNUMBER is empty, use "0".
-	flac --stdout --decode "$FILE" | \
+	flac --stdout --decode "${FILE}" | \
 	lame -m j -q 0 --vbr-new -V 0 -s 44.1 --add-id3v2 --pad-id3v2 \
-		--ignore-tag-errors --tn "${TRACK:-0}" --tt "$TITLE" \
-		--ta "$ARTIST" --tl "$ALBUM" --ty "$DATE" --tg "${GENRE:-12}" - "$OUTPUT"
+		--ignore-tag-errors --tn "${TRACK:-0}" --tt "${TITLE}" \
+		--ta "${ARTIST}" --tl "${ALBUM}" --ty "${DATE}" --tg "${GENRE:-12}" - "${OUTPUT}"
 	;;
 
 	m4a2mp3)
 	# Software needed: faad, lame
 	OUTPUT=${FILE%.m4a}.mp3
-	 TRACK=$(faad --info "$FILE" 2>&1 | grep ^track  | sed 's/^.*: //')
-	 TITLE=$(faad --info "$FILE" 2>&1 | grep ^title  | sed 's/^.*: //')
-	ARTIST=$(faad --info "$FILE" 2>&1 | grep ^artist | sed 's/^.*: //')
-	 ALBUM=$(faad --info "$FILE" 2>&1 | grep ^album  | sed 's/^.*: //')
-	  DATE=$(faad --info "$FILE" 2>&1 | grep ^date   | sed 's/^.*: //')
-	 GENRE=$(faad --info "$FILE" 2>&1 | grep ^genre  | sed 's/^.*: //')
+	 TRACK=$(faad --info "${FILE}" 2>&1 | grep ^track  | sed 's/^.*: //')
+	 TITLE=$(faad --info "${FILE}" 2>&1 | grep ^title  | sed 's/^.*: //')
+	ARTIST=$(faad --info "${FILE}" 2>&1 | grep ^artist | sed 's/^.*: //')
+	 ALBUM=$(faad --info "${FILE}" 2>&1 | grep ^album  | sed 's/^.*: //')
+	  DATE=$(faad --info "${FILE}" 2>&1 | grep ^date   | sed 's/^.*: //')
+	 GENRE=$(faad --info "${FILE}" 2>&1 | grep ^genre  | sed 's/^.*: //')
 
-	faad --stdio "$FILE" | lame "$LAMEARGS" --tn "${TRACK:-0}" --tt "$TITLE" \
-		--ta "$ARTIST" --tl "$ALBUM" --ty "$DATE" --tg "${GENRE:-12}" - "$OUTPUT"
+	faad --stdio "${FILE}" | lame "${LAMEARGS}" --tn "${TRACK:-0}" --tt "${TITLE}" \
+		--ta "${ARTIST}" --tl "${ALBUM}" --ty "${DATE}" --tg "${GENRE:-12}" - "${OUTPUT}"
 	;;
 
 	ogg2mp3)
 	OUTPUT=${FILE%.ogg}.mp3
-	eval $(ogginfo -qv "$FILE" | awk '/ARTIST/ || /TITLE/' | sed 's/^     //')
-#	echo "ARTIST: $ARTIST TITLE: $TITLE"
-	if [ -z "$ARTIST" ] || [ -z "$TITLE" ]; then
-		echo "WARNING: Not enough metadata, trying to gather track information from filename! ($FILE)"
-		 TRACK=$(ls "$FILE" | awk -F\  '{print $1}')
-		 TITLE=$(ls "$FILE" | sed 's/^[0-9]* - //;s/\.ogg//')
+	eval $(ogginfo -qv "${FILE}" | awk '/ARTIST/ || /TITLE/' | sed 's/^     //')
+#	echo "ARTIST: ${ARTIST} TITLE: ${TITLE}"
+	if [ -z "${ARTIST}" ] || [ -z "${TITLE}" ]; then
+		echo "WARNING: Not enough metadata, trying to gather track information from filename! (${FILE})"
+		 TRACK=$(ls "${FILE}" | awk -F\  '{print $1}')
+		 TITLE=$(ls "${FILE}" | sed 's/^[0-9]* - //;s/\.ogg//')
 
 		# Try to find the ARLBUM via the directory name
-		cd "$(dirname "$FILE")" || exit
+		cd "$(dirname "${FILE}")" || exit
 		ALBUM="$(basename $(pwd))"
-		echo "TRACK: $TRACK TITLE: $TITLE ALBUM: $ALBUM"
+		echo "TRACK: $TRACK TITLE: ${TITLE} ALBUM: ${ALBUM}"
 	fi
-	oggdec --quiet "$FILE" --output - | lame "$LAMEARGS" --tn "${TRACK:-0}" --tt "$TITLE" \
-		--tl "$ALBUM" - "$OUTPUT"
+	oggdec --quiet "${FILE}" --output - | lame "${LAMEARGS}" --tn "${TRACK:-0}" --tt "${TITLE}" \
+		--tl "${ALBUM}" - "${OUTPUT}"
 	;;
 
 	*)
-	echo "$(basename "$0"): conversion $CONVERSION unknow."
+	echo "$(basename "$0"): conversion ${CONVERSION} unknown"
 	exit 1
 	;;
 esac
diff --git a/find_dups.sh b/find_dups.sh
index 3131929..976b9df 100755
--- a/find_dups.sh
+++ b/find_dups.sh
@@ -83,7 +83,7 @@ case $MODE in
 	echo
 	echo "           All files: $(cat "$TEMP"             | wc -l)"
 	echo "Files with same size: $(cat "$TEMP".fallout     | wc -l)"
-	echo "     Duplicate files: $(expr $(egrep -c '^[[:alnum:]]' "$TEMP".fallout.dup) / 2)"
+	echo "     Duplicate files: $(expr $(grep -Ec '^[[:alnum:]]' "$TEMP".fallout.dup) / 2)"
 	echo "    Time to complete: $(expr "$END" - "$BEGIN") seconds"
 	echo
 	;;
@@ -98,7 +98,7 @@ case $MODE in
 	END=$(date +%s)
 	echo
 	echo "           All files: $(cat "$TEMP"             | wc -l)"
-	echo "     Duplicate files: $(expr $(egrep -c '^[[:alnum:]]' "$TEMP".dup) / 2)"
+	echo "     Duplicate files: $(expr $(grep -Ec '^[[:alnum:]]' "$TEMP".dup) / 2)"
 	echo "    Time to complete: $(expr "$END" - "$BEGIN") seconds"
 	;;
 
diff --git a/funiq.sh b/funiq.sh
index 9e7a6fa..cc3233a 100755
--- a/funiq.sh
+++ b/funiq.sh
@@ -57,4 +57,4 @@ awk 'BEGIN {CURRPAIRS=0;PAIRMATCHES=0;PREVPAIRS=0}
 	for (SUB in CURR) PREV[SUB]=CURR[SUB]
 	for (SUB in CURR) delete CURR[SUB]
 	PREVPAIRS=CURRPAIRS
-}' REQSIM=$SIM $@
+}' REQSIM=${SIM} $@
diff --git a/ipsec_iproute.sh b/ipsec_iproute.sh
index f5a5ce1..9cf235a 100755
--- a/ipsec_iproute.sh
+++ b/ipsec_iproute.sh
@@ -10,7 +10,7 @@
 # > “On the fly” IPsec VPN with iproute2
 # > https://backreference.org/2014/11/12/on-the-fly-ipsec-vpn-with-iproute2/
 #
-if [ $# -ne 7 ] || [ ! -f "$HOME/.xfrm-keys" ]; then
+if [ $# -ne 7 ] || [ ! -f "${HOME}/.xfrm-keys" ]; then
 	echo "Usage: $(basename "$0") [SRC LOCAL DEV] [DST REMOTE DEV] [start|stop|status]"
 	echo " Note: We also need a key file in \$HOME/.xfrm-keys, with NN bit keys and"
 	echo "       a 32 bit id, generated like this:"
@@ -32,69 +32,69 @@ else
 fi
 
 # Read keys
-eval $(grep -v ^\# "$HOME"/.xfrm-keys)
-if [ -z "$CIPHER" ] || [ -z "$KEY1" ] || [ -z "$KEY2" ] || [ -z "$ID" ]; then
-	echo "Could not read cipher/keys from $HOME/.xfrm-keys!"
+eval $(grep -Ev '^\#' "${HOME}/.xfrm-keys")
+if [ -z "${CIPHER}" ] || [ -z "${KEY1}" ] || [ -z "${KEY2}" ] || [ -z "${ID}" ]; then
+	echo "Could not read cipher/keys from ${HOME}/.xfrm-keys!"
 	exit 1
 fi
 
 # unset me!
 # DEBUG=echo
-# echo "DEBUG: SRC: $SRC LOCAL: $LOCAL DEVL: $DEVL / DST: $DST REMOTE: $REMOTE DEVR: $DEVR"
+# echo "DEBUG: SRC: ${SRC} LOCAL: ${LOCAL} DEVL: ${DEVL} / DST: ${DST} REMOTE: ${REMOTE} DEVR: ${DEVR}"
 
-case $ACTION in
+case ${ACTION} in
 	start)
 	# XFRM
-	$DEBUG ip xfrm state  add src "$SRC"    dst "$DST"    proto esp spi "$ID" reqid "$ID" mode tunnel auth sha256 "$KEY1" enc "$CIPHER" "$KEY2"
-	$DEBUG ip xfrm state  add src "$DST"    dst "$SRC"    proto esp spi "$ID" reqid "$ID" mode tunnel auth sha256 "$KEY1" enc "$CIPHER" "$KEY2"
-	$DEBUG ip xfrm policy add src "$LOCAL"  dst "$REMOTE" dir out tmpl src "$SRC" dst "$DST" proto esp reqid "$ID" mode tunnel
-	$DEBUG ip xfrm policy add src "$REMOTE" dst "$LOCAL"  dir in  tmpl src "$DST" dst "$SRC" proto esp reqid "$ID" mode tunnel
+	${DEBUG} ip xfrm state  add src "${SRC}"    dst "${DST}"    proto esp spi "${ID}" reqid "${ID}" mode tunnel auth sha256 "$KEY1" enc "$CIPHER" "$KEY2"
+	${DEBUG} ip xfrm state  add src "${DST}"    dst "${SRC}"    proto esp spi "${ID}" reqid "${ID}" mode tunnel auth sha256 "$KEY1" enc "$CIPHER" "$KEY2"
+	${DEBUG} ip xfrm policy add src "${LOCAL}"  dst "${REMOTE}" dir out tmpl src "${SRC}" dst "${DST}" proto esp reqid "${ID}" mode tunnel
+	${DEBUG} ip xfrm policy add src "${REMOTE}" dst "${LOCAL}"  dir in  tmpl src "${DST}" dst "${SRC}" proto esp reqid "${ID}" mode tunnel
 
 	# Routing
-	$DEBUG ip addr  add "$LOCAL"/32  dev lo
-	$DEBUG ip route add "$REMOTE"/32 dev "$DEVL" src "$LOCAL"
+	${DEBUG} ip addr  add "${LOCAL}/32"  dev lo
+	${DEBUG} ip route add "${REMOTE}/32" dev "${DEVL}" src "${LOCAL}"
 
 	# And again on the remote side
-	ssh "$DST" /bin/sh -x << EOF
+	ssh "${DST}" /bin/sh -x << EOF
 	    # XFRM
-	    $DEBUG ip xfrm state  add src $SRC    dst $DST    proto esp spi $ID reqid $ID mode tunnel auth sha256 $KEY1 enc "$CIPHER" $KEY2
-	    $DEBUG ip xfrm state  add src $DST    dst $SRC    proto esp spi $ID reqid $ID mode tunnel auth sha256 $KEY1 enc "$CIPHER" $KEY2
-	    $DEBUG ip xfrm policy add src $REMOTE dst $LOCAL  dir   out tmpl src $DST dst $SRC proto esp reqid $ID mode tunnel
-	    $DEBUG ip xfrm policy add src $LOCAL  dst $REMOTE dir   in  tmpl src $SRC dst $DST proto esp reqid $ID mode tunnel
+	    ${DEBUG} ip xfrm state  add src ${SRC}    dst ${DST}    proto esp spi ${ID} reqid ${ID} mode tunnel auth sha256 $KEY1 enc "$CIPHER" $KEY2
+	    ${DEBUG} ip xfrm state  add src ${DST}    dst ${SRC}    proto esp spi ${ID} reqid ${ID} mode tunnel auth sha256 $KEY1 enc "$CIPHER" $KEY2
+	    ${DEBUG} ip xfrm policy add src ${REMOTE} dst ${LOCAL}  dir   out tmpl src ${DST} dst ${SRC} proto esp reqid ${ID} mode tunnel
+	    ${DEBUG} ip xfrm policy add src ${LOCAL}  dst ${REMOTE} dir   in  tmpl src ${SRC} dst ${DST} proto esp reqid ${ID} mode tunnel
 	    # Routing
-	    $DEBUG ip addr  add $REMOTE/32 dev lo
-	    $DEBUG ip route add $LOCAL/32  dev $DEVR src $REMOTE
+	    ${DEBUG} ip addr  add ${REMOTE}/32 dev lo
+	    ${DEBUG} ip route add ${LOCAL}/32  dev ${DEVR} src ${REMOTE}
 EOF
 	;;
 
 	stop)
 	# Remote
-	ssh "$DST" /bin/sh -x << EOF
+	ssh "${DST}" /bin/sh -x << EOF
 	    # Routing
-	    $DEBUG ip route del $LOCAL/32  dev $DEVR src $REMOTE
-	    $DEBUG ip addr  del $REMOTE/32 dev lo
+	    ${DEBUG} ip route del ${LOCAL}/32  dev ${DEVR} src ${REMOTE}
+	    ${DEBUG} ip addr  del ${REMOTE}/32 dev lo
 	    # XFRM
-	    $DEBUG ip xfrm policy del src $LOCAL  dst $REMOTE dir   in
-	    $DEBUG ip xfrm policy del src $REMOTE dst $LOCAL  dir   out
-	    $DEBUG ip xfrm state  del src $DST    dst $SRC    proto esp spi $ID
-	    $DEBUG ip xfrm state  del src $SRC    dst $DST    proto esp spi $ID
+	    ${DEBUG} ip xfrm policy del src ${LOCAL}  dst ${REMOTE} dir   in
+	    ${DEBUG} ip xfrm policy del src ${REMOTE} dst ${LOCAL}  dir   out
+	    ${DEBUG} ip xfrm state  del src ${DST}    dst ${SRC}    proto esp spi ${ID}
+	    ${DEBUG} ip xfrm state  del src ${SRC}    dst ${DST}    proto esp spi ${ID}
 EOF
 	# Routing
-	$DEBUG ip route del "$REMOTE"/32 dev "$DEVL" src "$LOCAL"
-	$DEBUG ip addr  del "$LOCAL"/32  dev lo
+	${DEBUG} ip route del "${REMOTE}"/32 dev "${DEVL}" src "${LOCAL}"
+	${DEBUG} ip addr  del "${LOCAL}"/32  dev lo
 
 	# XFRM
-	$DEBUG ip xfrm policy del src "$REMOTE" dst "$LOCAL"  dir in
-	$DEBUG ip xfrm policy del src "$LOCAL"  dst "$REMOTE" dir out
-	$DEBUG ip xfrm state  del src "$DST"    dst "$SRC"    proto esp spi "$ID"
-	$DEBUG ip xfrm state  del src "$SRC"    dst "$DST"    proto esp spi "$ID"
+	${DEBUG} ip xfrm policy del src "${REMOTE}" dst "${LOCAL}"  dir in
+	${DEBUG} ip xfrm policy del src "${LOCAL}"  dst "${REMOTE}" dir out
+	${DEBUG} ip xfrm state  del src "${DST}"    dst "${SRC}"    proto esp spi "${ID}"
+	${DEBUG} ip xfrm state  del src "${SRC}"    dst "${DST}"    proto esp spi "${ID}"
 	;;
 
 	status)
-	$DEBUG ip xfrm state && ip xfrm policy
+	${DEBUG} ip xfrm state && ip xfrm policy
 	echo
-	ssh "$DST" /bin/sh -x << EOF
-		$DEBUG ip xfrm state && ip xfrm policy
+	ssh "${DST}" /bin/sh -x << EOF
+		${DEBUG} ip xfrm state && ip xfrm policy
 EOF
 	;;
 esac
diff --git a/keyboard-backlight.sh b/keyboard-backlight.sh
index 9c2f8bc..5e5c325 100755
--- a/keyboard-backlight.sh
+++ b/keyboard-backlight.sh
@@ -26,11 +26,11 @@
 # variable as you want it.
 #
 
- BACKLIGHT="/sys/class/leds/smc::kbd_backlight/brightness"
-BRIGHTNESS=$(cat $BACKLIGHT)
+ BACKLIGHT="/sys/class/leds/smc::kbd_backlight/brightness"		# TBD
+BRIGHTNESS=$(cat ${BACKLIGHT})
  INCREMENT=20
 
-if [ $(id -ru) -ne 0 ]; then
+if [ "$(id -ru)" -ne 0 ]; then
 	echo "Please run this program as superuser!"
 	exit 1
 fi
@@ -43,37 +43,37 @@ exit 1
 case $1 in
 	up)
 	# BRIGHTNESS will be capped at 255 anyway
-	if [ "$BRIGHTNESS" -lt 255 ]; then
-		expr "$BRIGHTNESS" + $INCREMENT > $BACKLIGHT
+	if [ "${BRIGHTNESS}" -lt 255 ]; then
+		echo $(( BRIGHTNESS + INCREMENT )) > ${BACKLIGHT}
 	else
-		die "$BRIGHTNESS"
+		die "${BRIGHTNESS}"
 	fi
 	;;
 
 	down)
-	if [ "$BRIGHTNESS" -gt 0 ]; then
-		VALUE=$(expr "$BRIGHTNESS" - $INCREMENT)
+	if [ "${BRIGHTNESS}" -gt 0 ]; then
+		VALUE=$(( BRIGHTNESS - INCREMENT ))
 
 		# BRIGHTNESS cannot be negative
 		[ "$VALUE" -lt 0 ] && VALUE=0
-		echo $VALUE > $BACKLIGHT
+		echo $VALUE > ${BACKLIGHT}
 	else
-		die "$BRIGHTNESS"
+		die "${BRIGHTNESS}"
 	fi
 	;;
 
 	total)
-	echo 255 > $BACKLIGHT
+	echo 255 > ${BACKLIGHT}
 	;;
 
 	off)
-	echo 0 > $BACKLIGHT
+	echo 0 > ${BACKLIGHT}
 	;;
 
-	[\-0-9]*)
+	[0-9]*)
 	VALUE=$1
 	if [ "$VALUE" -ge 0 ] && [ "$VALUE" -le 255 ]; then
-		echo "$VALUE" > $BACKLIGHT
+		echo "$VALUE" > ${BACKLIGHT}
 	else
 		echo "Invalid argument ($VALUE). Please provide a value from 0 to 255!"
 		exit 1
@@ -86,4 +86,4 @@ case $1 in
 	;;
 esac
 
-echo "Brightness set to $(cat $BACKLIGHT)"
+echo "Brightness set to $(cat ${BACKLIGHT})"
diff --git a/port-mgmt.sh b/port-mgmt.sh
index 56372c5..12d843b 100755
--- a/port-mgmt.sh
+++ b/port-mgmt.sh
@@ -4,7 +4,7 @@
 # MacPorts cleanup
 #
 PATH=/bin:/usr/bin:/opt/local/bin
-LAST="$HOME"/.ports.clean
+LAST="${HOME}/.ports.clean"
 umask 0022
 
 case $1 in
@@ -20,16 +20,16 @@ case $1 in
 	port selfupdate
 	port echo outdated 
 	port upgrade -u outdated
-	if [ -f "$LAST" ]; then
-		A=$(stat -f %m "$LAST")
+	if [ -f "${LAST}" ]; then
+		A=$(stat -f %m "${LAST}")
 		B=$(date +%s)
 		# Cleanup every 1209600 seconds (14 days)
-		if [ $(echo "$B" - "$A" | bc) -gt 1209600 ]; then
+		if [ $(( B - A )) -gt 1209600 ]; then
 			echo "port clean all..."
 			echo nice -n20 port clean -f --all all > /dev/null
 		fi
 	else
-		touch "$LAST"
+		touch "${LAST}"
 	fi
 	;;
 
diff --git a/qemu-tap.sh b/qemu-tap.sh
index c833afe..2718022 100755
--- a/qemu-tap.sh
+++ b/qemu-tap.sh
@@ -6,37 +6,37 @@
 # > How do I bridge a connection from Wi-Fi to TAP on Mac OS X? (for the emulator QEMU)
 # > https://superuser.com/a/766251
 #
-INTERFACE=en1
+INTERFACE="en1"
 
 # set to echo/sudo
-DEBUG=sudo
+DEBUG="sudo"
 
 # See how we were called
 case $(basename "$0") in
 	qemu-ifup)
 	# Needed for the symlink
 	umask 0022
-	$DEBUG ln -sf /dev/tap0 /dev/tap
-	$DEBUG sysctl -w net.inet.ip.forwarding=1
-	$DEBUG sysctl -w net.link.ether.inet.proxyall=1
-	$DEBUG sysctl -w net.inet.ip.fw.enable=1
-	$DEBUG ifconfig bridge0 create
-	$DEBUG ifconfig bridge0 addm $INTERFACE addm tap0
-	$DEBUG ifconfig bridge0 up
-	$DEBUG natd -interface en1
-	$DEBUG ipfw add divert natd ip from any to any via $INTERFACE
+	${DEBUG} ln -sf /dev/tap0 /dev/tap
+	${DEBUG} sysctl -w net.inet.ip.forwarding=1
+	${DEBUG} sysctl -w net.link.ether.inet.proxyall=1
+	${DEBUG} sysctl -w net.inet.ip.fw.enable=1
+	${DEBUG} ifconfig bridge0 create
+	${DEBUG} ifconfig bridge0 addm ${INTERFACE} addm tap0
+	${DEBUG} ifconfig bridge0 up
+	${DEBUG} natd -interface en1
+	${DEBUG} ipfw add divert natd ip from any to any via ${INTERFACE}
 	;;
 
 	qemu-ifdown)
-	$DEBUG ipfw del 00100
-	$DEBUG ipfw del $(sudo ipfw list | grep "ip from any to any via $INTERFACE" | sed -e 's/ .*//g')
-	$DEBUG killall -9 natd
-	$DEBUG sysctl -w net.inet.ip.forwarding=0
-	$DEBUG sysctl -w net.link.ether.inet.proxyall=0
-	$DEBUG sysctl -w net.inet.ip.fw.enable=1
-	$DEBUG ifconfig bridge0 deletem $INTERFACE deletem tap0
-	$DEBUG ifconfig bridge0 down
-	$DEBUG ifconfig bridge0 destroy
+	${DEBUG} ipfw del 00100
+	${DEBUG} ipfw del "$(sudo ipfw list | grep "ip from any to any via ${INTERFACE}" | sed -e 's/ .*//g')"
+	${DEBUG} killall -9 natd
+	${DEBUG} sysctl -w net.inet.ip.forwarding=0
+	${DEBUG} sysctl -w net.link.ether.inet.proxyall=0
+	${DEBUG} sysctl -w net.inet.ip.fw.enable=1
+	${DEBUG} ifconfig bridge0 deletem ${INTERFACE} deletem tap0
+	${DEBUG} ifconfig bridge0 down
+	${DEBUG} ifconfig bridge0 destroy
 	;;
 
 	*)
diff --git a/sensors_adt746x.sh b/sensors_adt746x.sh
index eec4b8e..0318c03 100755
--- a/sensors_adt746x.sh
+++ b/sensors_adt746x.sh
@@ -9,14 +9,14 @@ BASE=/sys/devices/temperatures
 
 case $1 in
 	-s|--short)
-	echo "CPU: $(cat $BASE/sensor1_temperature) ($(awk '/^clock/ {print $3}' /proc/cpuinfo \
+	echo "CPU: $(cat ${BASE}/sensor1_temperature) ($(awk '/^clock/ {print $3}' /proc/cpuinfo \
 			| sed 's/\.[0-9]*//')) Fan: $(sed 's/.*(//;s/ rpm)$//' \
-			< $BASE/sensor1_fan_speed) GPU: $(cat $BASE/sensor2_temperature)"
+			< ${BASE}/sensor1_fan_speed) GPU: $(cat ${BASE}/sensor2_temperature)"
 	;;
 
 	-b)
 	# If pmu_battery is present
-	find /sys/ -type f | grep batte | egrep -v 'uevent|srcversion|initstate|refcnt|sections/\.|autosuspend_delay_ms|note.gnu.build' | \
+	find /sys/ -type f | grep battery | grep -Ev 'uevent|srcversion|initstate|refcnt|sections/\.|autosuspend_delay_ms|note.gnu.build' | \
 		xargs grep . | sed 's/.*pmu-battery.[0-9]\///;s/:/		/'
 	;;
 
@@ -28,13 +28,13 @@ case $1 in
 	;;
 
 	*)
-	for p in $BASE/sensor1_location \
-		 $BASE/sensor1_fan_speed \
-		 $BASE/sensor1_temperature \
-		 $BASE/sensor1_limit \
-		 $BASE/sensor2_location \
-		 $BASE/sensor2_temperature \
-		 $BASE/sensor2_limit; do
+	for p in ${BASE}/sensor1_location \
+		 ${BASE}/sensor1_fan_speed \
+		 ${BASE}/sensor1_temperature \
+		 ${BASE}/sensor1_limit \
+		 ${BASE}/sensor2_location \
+		 ${BASE}/sensor2_temperature \
+		 ${BASE}/sensor2_limit; do
 		echo "$(basename $p)	$(cat $p)"
 	done
 	# As a bonus, print our current clockspeed
diff --git a/vbox-sysrq.sh b/vbox-sysrq.sh
index 9407e14..179551a 100755
--- a/vbox-sysrq.sh
+++ b/vbox-sysrq.sh
@@ -55,10 +55,10 @@ w|11		# show-blocked-tasks
 z|2C		# dump-ftrace-buffer
 " | grep -E "^${SYSRQ}" | cut -c3,4)
 
-if [ -n "$PRESS" ]; then
-	RELEASE=$(printf "%X\n" $((0x$PRESS + 0x80)))	# or: 'obase=16; ibase=16; $PRESS + 80 | bc'
+if [ -n "${PRESS}" ]; then
+	RELEASE=$(printf "%X\n" $((0x${PRESS} + 0x80)))	# or: 'obase=16; ibase=16; $PRESS + 80 | bc'
 	set -x
-	VBoxManage controlvm "$VM" keyboardputscancode 1d 38 54 "$PRESS" "$RELEASE" d4 b8 9d
+	VBoxManage controlvm "$VM" keyboardputscancode 1d 38 54 "${PRESS}" "${RELEASE}" d4 b8 9d
 else
 	echo
 	echo "Unknown sysrq key! (${SYSRQ})"