本节内容：
保留文件系统下剩余指定数目的文件
例子：
#!/bin/bash
#-------------------------------
#Description: Back up your files
#site: www.jb51.net
#-------------------------------
#shell 变量
path_source=/mnt/fifth/shell
path_backup=/mnt/fifth/backup/shellbackup
path_delete=/mnt/fifth/tmp/rubbish/
limit_num=15
fileBackup()
{
set -x
#备份文件
#cp -r $1 $2/shell-`date +%Y-%m-%d-%H-%M-%S`
count=`ls $1 | wc -w`
if [ "$count" -gt "$3" ];then
echo "-----------------limit is : $3 ----------------------"
echo "-----------------The number of files is : $count -------"
num=`expr $count - $3`
echo "-----------------The excess number of files is : $num ---------"
#移动文件
ls $1 -1rt | head -n $num|xargs -n1 -i mv $1/{} $2
set +x
ls -1rt $2
echo "-----------------Moving end!-----------------"
else
ls -1rt $2
echo "-----------------The file is too little!-------------------"
fi
}
#备份shell脚本
fileBackup $path_backup $path_delete $limit_num
