session in django

django中session选择文件形式存储，貌似没有自动垃圾清理的机制，所以会造成很多的无用session文件

删除30分钟没有活动的会话，这里默认每次页面访问都会读取session。

find /tmp/ -type f -name "sessionid*" -amin +30 | sudo xargs rm -f

附： 参考这里http://www.linuxselfhelp.com/gnu/findutils/html_chapter/find_2.html

文件的三种时间标志

Each file has three time stamps, which record the last time that certain operations were performed on the file:
   1. access (read the file's contents)
   2. change the status (modify the file or its attributes)
   3. modify (change the file's contents) 

对应的，find有如下时间比较条件

These tests are mainly useful with ranges (`+n' and `-n').

-atime n
-ctime n
-mtime n

True if the file was last accessed (or its status changed, or it was modified) n*24 hours ago. 

-amin n
-cmin n
-mmin n