1 files changed, 22 insertions, 0 deletions
diff --git a/bin/ean13 b/bin/ean13
new file mode 100755
index 0000000..6fd125a
--- /dev/null
+++ b/bin/ean13
@@ -0,0 +1,22 @@
+#!/bin/bash
+while [[ $1 ]]
+do
+[[ ${#1} -eq 13 ]] || [[ ${#1} -eq 12 ]] || {
+	printf >&2 'length is %d, should be 13\n' ${#1}
+	exit 1
+}
+declare -i checksum=0
+declare -i factor=1
+for i in {0..11}
+do
+	v=${1:i:1}
+	checksum=$((checksum+factor*v))
+	factor=$((factor^2))
+#printf >&2 'v: %s : cs=%d f=%d\n' "$v" $checksum $factor
+done
+if [[ ${#1} -eq 12 ]]
+then	echo "$1"$((10-checksum%10))
+else	[[ $((10-checksum%10)) -eq ${1:12} ]] || exit
+fi
+shift
+done