diff --git a/contrib/gbdiff.bash b/contrib/gbdiff.bash
index 39014040..2cf7ecd2 100755
--- a/contrib/gbdiff.bash
+++ b/contrib/gbdiff.bash
@@ -31,29 +31,29 @@ diff <(xxd $1) <(xxd $2) | while read -r LINE; do
 		# Separator between files switches states
 		echo $LINE
 		STATE=3
-	elif echo $LINE | grep -Eq '^[0-9]+(,[0-9]+)?c[0-9]+(,[0-9]+)?'; then
+	elif grep -Eq '^[0-9]+(,[0-9]+)?[cd][0-9]+(,[0-9]+)?' <<< "$LINE"; then
 		# Line info resets the whole thing
 		STATE=1
 	elif [ $STATE -eq 1  -o  $STATE -eq 3 ]; then
 		# Compute the GB address from the ROM offset
-		OFS=$(echo $LINE | cut -d ' ' -f 2 | tr -d ':')
+		OFS=$(cut -d ' ' -f 2 <<< "$LINE" | tr -d ':')
 		BANK=$((0x$OFS / 0x4000))
 		ADDR=$((0x$OFS % 0x4000 + ($BANK != 0) * 0x4000))
 		# Try finding the preceding symbol closest to the diff
 		if [ $STATE -eq 1 ]; then
 			STATE=2
-			SYMFILE=$(echo $1 | cut -d '.' -f 1).sym
+			SYMFILE=${1%.*}.sym
 		else
 			STATE=4
-			SYMFILE=$(echo $2 | cut -d '.' -f 1).sym
+			SYMFILE=${2%.*}.sym
 		fi
 		EXTRA=$(if [ -f "$SYMFILE" ]; then
 			# Read the sym file for such a symbol
 			# Ignore comment lines, only pick matching bank
-			grep -Fv ';' "$SYMFILE" |
+			cut -d ';' -f 1 "$SYMFILE" |
 			 grep -Ei $(printf "^%02x:" $BANK) |
 			 while read -r SYMADDR SYM; do
-				SYMADDR=$((0x$(echo $SYMADDR | cut -d ':' -f 2)))
+				SYMADDR=$((0x${SYMADDR#*:}))
 				if [ $SYMADDR -le $ADDR ]; then
 					printf " (%s+%#x)\n" $SYM $(($ADDR - $SYMADDR))
 				fi
@@ -63,9 +63,9 @@ diff <(xxd $1) <(xxd $2) | while read -r LINE; do
 		printf "%02x:%04x %s\n" $BANK $ADDR $EXTRA
 	fi
 	if [ $STATE -eq 2  -o  $STATE -eq 4 ]; then
-		OFS=$(echo $LINE | cut -d ' ' -f 2 | tr -d ':')
+		OFS=$(cut -d ' ' -f 2 <<< "$LINE" | tr -d ':')
 		BANK=$((0x$OFS / 0x4000))
 		ADDR=$((0x$OFS % 0x4000 + ($BANK != 0) * 0x4000))
-		printf "%s %02x:%04x: %s\n" "$(echo $LINE | cut -d ' ' -f 1)" $BANK $ADDR "$(echo $LINE | cut -d ' ' -f 3-)"
+		printf "%s %02x:%04x: %s\n" "${LINE:0:1}" $BANK $ADDR "${LINE#*: }"
 	fi
 done