From 75b23ce1ff0daab363725a2a5755ea80bbeaa68e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20W=C3=BChrer?= <def@gmx.at>
Date: Sun, 17 Mar 2024 11:55:29 +0100
Subject: ean13

---
 ean13 | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100755 ean13

(limited to 'ean13')

diff --git a/ean13 b/ean13
new file mode 100755
index 0000000..6fd125a
--- /dev/null
+++ b/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
-- 
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