diff --git a/backup_script.sh b/backup_script.sh
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+++ b/backup_script.sh
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+#!/bin/sh
+
+#version 2
+#iansun2 2022/7/14
+
+
+#config (without "/"  eg. /DISKI/Backup)
+source_dir=
+output_dir=
+backup_count_max=
+
+
+#init
+year=$(date +"%Y") #get year
+month=$(date +"%m") #get month
+date=$(date +"%d") #get date
+
+file_name=${year}"_"${month}"_"${date}".7z" #new backup file name  eg. 2022_2_2.7z
+backup_count=$(find ${output_dir} -type f -iname "*.7z" -print | wc -l) #count file in $output_dir with name *.7z as $backup_count
+
+
+#check src/out dir
+if [ -d $source_dir ]
+then
+	echo "source dir found, ok"
+else
+	echo "source dir not found, exit"
+	exit 0
+fi
+
+
+if [ -d $output_dir ]
+then
+	echo "output dir found, enter"
+	cd $output_dir
+else
+        echo "output dir not found, exit"
+	exit 0
+fi
+
+
+#log dir
+if [ -d "log" ] #check log dir exist?
+then
+	echo "log dir exist"
+else
+	mkdir "log"
+	echo "log dir not exist, create"
+fi
+
+echo ${year}"_"${month}"_"${date} >> ${output_dir}"/log/backup_record" #save backup time in ${output_dir}/log/backup_record
+
+
+#clear old backup
+echo "check old backup"
+echo "old backup count: "${backup_count}
+while [ ${backup_count} -gt ${backup_count_max} ] #while $backup_count > $backup_count_max
+do
+	oldest_file=$(find ${output_dir} -type f -iname "*.7z" -print | sort -n | head -n 1) #find oldest *.7z file by name
+	rm $oldest_file
+	echo "remove "${oldest_file}
+	backup_count=$((backup_count-1))
+done
+
+find ${output_dir} -empty -type d -delete #delete empty dir
+
+
+#year dir
+if [ -d $year ]
+then
+	cd $year
+	echo "year dir exist, enter!"
+else
+	mkdir $year
+	cd $year
+	echo "year dir not exist, create!"
+fi
+
+
+#month dir
+if [ -d $month ]
+then
+	cd $month
+	echo "month dir exist, enter!"
+else
+	mkdir $month
+	cd $month
+	echo "month dir not exist, create!"
+fi
+
+
+
+echo "create backup"
+7z a ${file_name} ${source_dir}"/" -mx9
+
+
+#echo "[debug]"
+#find ${output_dir} -type f -print | sort -n
+
+#echo $backup_count
+#echo $source_dir
+#echo $file_name