shell 杂项...

目录：

1--- 获取系统时间

2---

3---

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1--- 获取系统时间

当前时间

 today=$(date -d "today" '+%Y%m%d %H:%M:%S')

 [root@localhost ~]# today=$(date -d "today" '+%Y%m%d %H:%M:%S')
 [root@localhost ~]# echo $today                                                             
 20100820 09:22:16                                                                                  

当前时间的前一天 

prevday=$(date -d "yesterday $today" '+%Y%m%d %H:%M:%S')

 [root@localhost ~]# prevday=$(date -d "yesterday $today" '+%Y%m%d %H:%M:%S')
 [root@localhost ~]# echo $prevday                                                                                
 20100819 09:22:16