shell 一 判断文件是否存在 创建文件 拷贝文件

#!/bin/bash
back="null"
backpath="back"
#备份系统源
#判断是否存在备份文件夹

for being in `ls $HOME`;do
if [ $being = "back" ]
then
back="back"
break
fi
done
#不存在则创建
if [ $back = "null" ]
then
echo "+++++++创建备份文件 back+++++++"
`mkdir $HOME/back`
fi

#查找文件是否叫sources.list 是则输出
for file in `ls /etc/apt`;do
if  [ $file = "sources.list" ]
then
echo $file
`cp /etc/apt/$file $HOME/$backpath/`
cat "${HOME}/${backpath}/${file}"
fi
done