shell备份脚本(改进版)

#!/bin/bash
olddir=~/shell
newdir=/media/LinuxShare/backup

# 若切换目录成功，则返回0，否则返回1
cd $newdir 2> /dev/null    && cd $olddir 2> /dev/null
if [ $? != 0 ]
then
    echo "Can not find directory $newdir or $olddir,backup fails." | mailx -s "Backup Notification" [e-mail]
    exit
fi

i=0

cd $olddir
# 遍历目录所有文件
for filename in *
do
    cd $newdir
    if [ -e "$filename" ]
    then
        if ! diff $newdir/$filename $olddir/$filename > /dev/null
        then    # return 0
            mv $newdir/$filename $newdir/$filename.$(date +%Y-%m-%d)
            cp $olddir/$filename $newdir
            ((i++))
        fi
    elif [ ! -e "$filename" ]
    then
        cp $olddir/$filename $newdir
        ((i++))
    fi
done

if [ $i -gt 0 ]
then
    echo "$i file(s) have been updated.Backup succeed." | mailx -s "Backup Notification" [e-mail]
else
    echo "Nothing new to backup." | mailx -s "Backup Notification" [e-mail]
fi