ubuntu下使用crontab

建立crontab任務

參考：https://www.cnblogs.com/Icanflyssj/p/5138851.html

3. crontab經常使用的幾個命令格式

crontab -l //顯示用戶的crontab文件的內容

crontab -e //編輯用戶的crontab文件的內容

crontab -r //刪除用戶的crontab文件

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在第一次使用crontab -e，會要求選擇編輯器，我選擇是vim.basic

編輯文件，內容以下

root@ubuntu:/var/log# crontab -e
# Edit this file to introduce tasks to be run by cron.
# 
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# 
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').# 
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# 
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 
# For more information see the manual pages of crontab(5) and cron(8)
# 
# m h  dom mon dow   command
* * * * * /home/xwdreamer/eclipse-workspace/RELEASED_V2_10_20180331/iotkit-embedded/output/release/bin/linkkit-example

 

 其餘間隔執行時間設定

每分鐘執行      * * * * *
每五分鐘執行    */5 * * * *
每小時執行      0 * * * *
天天執行       0 0 * * *
每週執行       0 0 * * 0
每個月執行       0 0 1 * *
每一年執行       0 0 1 1 *

 

 

 

 

日誌服務

參考：https://blog.csdn.net/ggz631047367/article/details/50185425

ubuntu默認沒有開啓cron日誌記錄 
1. 修改rsyslog 
sudo vim /etc/rsyslog.d/50-default.conf 
cron.* /var/log/cron.log #將cron前面的註釋符去掉 
2.重啓rsyslog 
sudo service rsyslog restart 
3.查看crontab日誌 
less /var/log/cron.log

注意：這裏必須重啓日誌服務，重啓之後使用less查看可能尚未日誌，須要等任務執行之後才能看到日誌。

 

查看cron日誌

vim /var/log/cron.log 

在日誌中找到

No MTA installed, discarding output 

 

解決方案：將日誌輸出到指定文件

*/5 * * * * /home/xwdreamer/iotkit/linkkit-example_INV/linkkit-example_INV > linkkit-example_INV_temp.log

 

完整以下

root@ubuntu:~# crontab -e
# Edit this file to introduce tasks to be run by cron.
# 
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# 
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').# 
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# 
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 
# For more information see the manual pages of crontab(5) and cron(8)
# 
# m h  dom mon dow   command
*/5 * * * * /home/xwdreamer/iotkit/linkkit-example_INV/linkkit-example_INV > linkkit-example_INV_temp.log 
*/5 * * * * /home/xwdreamer/iotkit/linkkit-example_penguan/linkkit-example_penguan > linkkit-example_penguan_temp.log

 

最後日誌會被輸出到當前帳戶下的目錄，好比當前這個文件被輸出到/root目錄下

root@ubuntu:/home/xwdreamer/iotkit# find / -name linkkit-example_INV_temp.log
find: ‘/run/user/1000/gvfs’: Permission denied
/root/linkkit-example_INV_temp.log
find: ‘/mnt/hgfs’: Protocol error