1,shell 脚本获取时间
1）获取当前时间 date
date "+%Y-%m-%d %H:%M:%S" 2016-01-27 17:37:31
2）前后时间，加ago就是前，没有ago就是后
$date -d ‘1 years ago‘ "+%Y-%m-%d %H:%M:%S"
date -d "1 years ago" "+%Y-%m-%d %H:%M:%S" 2015-01-27 17:54:39 $date -d ‘1 months ago‘ "+%Y-%m-%d %H:%M:%S"
date -d "1 months ago" "+%Y-%m-%d %H:%M:%S" 2015-12-27 17:54:45 days,hours,minutes 类似
 
date -d "-k days" "+%Y-%m-%d %H:%M:%S" 返回k天前的具体时间

3）传参获取时间
start_date=20160127
date?d"start_date+1days" +%Y%m%d   20160128

4）修改时间格式
today=`date -d "$start_date+1days" +%Y-%m-%d`  
today = 2016-01-28
yestoday=`date -d "$start_date" +%Y-%m-%d`  
yestoday = 2016-01-27