有關Crontab設定

Crontab 主要是在做排程設定, 一般寫法如下:
分 時 日 月 週 指令
範例：0 0 * * * /usr/local/backup/appbackup.sh

field allowed values
----- --------------
minute 0-59
hour 0-23
day of month 1-31
month 1-12 (or names, see below)
day of week 0-7 (0 or 7 is Sun, or use names)

上面範例寫法另外可寫成：@daily /usr/local/backup/appbackup.sh

string meaning
------ -------
@reboot Run once, at startup
@yearly Run once a year, "0 0 1 1 *"
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *"
@weekly Run once a week, "0 0 * * 0"
@daily Run once a day, "0 0 * * *"
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *"

在寫crontab指令時須注意要用絕對路徑如 rm 執行檔必須寫成 /usr/bin/rm