Linux的/tmp定期的刪除說明
/tmp是Linux 用來放暫存資料的地方，
系統有支排程在 /etc/cron.daily/tmpwatch（That depends on your distribution. On some system, it's deleted only when booted, others have cronjobs running deleting items older than n hours.
On Debian-like systems, the rules are defined in /etc/default/rcS. RedHat-like, it's /etc/cron.daily/tmpwatch and /etc/conf.d/bootmisc for Gentoo.）
flags=-umc
/usr/sbin/tmpwatch "$flags" -x /tmp/.X11-unix -x /tmp/.XIM-unix
-x /tmp/.font-unix -x /tmp/.ICE-unix -x /tmp/.Test-unix 240 /tmp
/usr/sbin/tmpwatch "$flags" 720 /var/tmp
for d in /var/{cache/man,catman}/{cat?,X11R6/cat?,local/cat?}; do
if [ -d "$d" ]; then
/usr/sbin/tmpwatch "$flags" -f 720 "$d"
fi
done
它每天執行，來掃 /tmp 目錄下的檔案或目錄，已超過10天的就把它刪除
第三行的 240 數值代表是小時，等於10天
第四行則是30天來清 /var/tmp
-x 參數代表要排除不刪的
