Crontab 格式
* * * * * command to be executed
- - - - -
| | | | |
| | | | ----- Day of week (0 - 7) (Sunday=0 or 7)
| | | ------- Month (1 - 12)
| | --------- Day of month (1 - 31)
| ----------- Hour (0 - 23)
------------- Minute (0 - 59)
*/5 * * * * per 5 minutes
常用指令
列出現有 CronJobs
# crontab -l
# crontab -u username -l
移除現有 CronJobs，注意: 不建議使用，移除 Job 建議使用編輯或註解的方式
# crontab -r
# crontab -r -u username
使用特殊字元
| Special 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 * * * *". |
範例：
使用特殊字元取代前五個時間格式的表示式
@hourly /path/to/ntpdate
每個月的最後一天
if test $(TZ=GMT-24 date +%d) = 1; then
/path/to/job
fi
OR
if test `TZ=GMT-24 date +%d` = 1; then
/path/to/job
fi
關閉惱人的郵件通知
在每一個 CronJob 後面加上 > /dev/null 2>&1。
0 3 * * * /root/backup.sh >/dev/null 2>&1
或者在最上面加上這一行
MAILTO=""
防止輸出訊息 'TERM environment variable not set'
在 shell script 加上
reference to undefined name 'syntax' Exception of type 'MindTouch.Deki.Script.Runtime.DekiScriptUndefinedNameException' was thrown. (click for details)Callstack:
at User:Alang/Linux_&_UNIX_工作筆記/Linux_SHELL/CronJob_進階技巧
MindTouch.Deki.Script.Runtime.DekiScriptUndefinedNameException: reference to undefined name 'syntax' Exception of type 'MindTouch.Deki.Script.Runtime.DekiScriptUndefinedNameException' was thrown.
at MindTouch.Deki.Script.Compiler.DekiScriptExpressionEvaluation.Visit (MindTouch.Deki.Script.Expr.DekiScriptVar expr, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Expr.DekiScriptVar.VisitWith[DekiScriptExpressionEvaluationState,Range] (IDekiScriptExpressionVisitor`2 visitor, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Compiler.DekiScriptExpressionEvaluation.Evaluate (MindTouch.Deki.Script.Expr.DekiScriptAccess expr, DekiScriptExpressionEvaluationState state, Boolean evaluateProperties) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Compiler.DekiScriptExpressionEvaluation.Visit (MindTouch.Deki.Script.Expr.DekiScriptAccess expr, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Expr.DekiScriptAccess.VisitWith[DekiScriptExpressionEvaluationState,Range] (IDekiScriptExpressionVisitor`2 visitor, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Compiler.DekiScriptExpressionEvaluation.Visit (MindTouch.Deki.Script.Expr.DekiScriptCall expr, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Expr.DekiScriptCall.VisitWith[DekiScriptExpressionEvaluationState,Range] (IDekiScriptExpressionVisitor`2 visitor, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Compiler.DekiScriptExpressionEvaluation.Visit (MindTouch.Deki.Script.Expr.DekiScriptSequence expr, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Expr.DekiScriptSequence.VisitWith[DekiScriptExpressionEvaluationState,Range] (IDekiScriptExpressionVisitor`2 visitor, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
at MindTouch.Deki.Script.Compiler.DekiScriptExpressionEvaluation.Visit (MindTouch.Deki.Script.Expr.DekiScriptReturnScope expr, DekiScriptExpressionEvaluationState state) [0x00000] in <filename unknown>:0
