Process after Linux Study Notes (cron and crontab)

Process after Linux Study Notes (cron and crontab)

. Set the crontab file and use it to submit the job.
. Use the AT command to submit a job
. Submit a job in the background
. Use the nohup command to submit a job

Cron system scheduling process, which is used to run jobs during off-peak hours every day, or run jobs during different periods in one week or one month.
At command to run some special jobs at specific time
& Use it to run a process that takes no longer time in the background
Nohup uses it to run a command in the background, even if the user exits, it will not be affected.

3.1 cron and crontab

Cron is a system scheduling process that runs jobs without human intervention.
The crontab command allows you to submit, edit, or delete a job. Each user has a crontab file to save scheduling information,

3.1.1 crontab Field

1st columns minute 1 ~ 59
2nd columns hour 1 ~ 23
3rd columns, Day 1-31
4th columns Month 1 ~ 12
5th columns in a week 0 ~ 6
6th columns of commands to run

3.1.2 example
30 21 ***/apps/bin/clearnup. Sh
Run cleanup. Sh in the/apps/bin directory at every night.

45 4, 10, 22 **/apps/bin/backup. Sh
Execute backup. Sh in the/apps/bin directory at on November 22 ,.

10 1 ** 6, 0/bin/find-name "core" RM {}/;
Every Saturday. Run a find command

0, 30 18-23 ***/apps/bin/dbcheck. Sh
Every day between and ~ Run dbcheck. Sh in the/apps/bin directory every 30 minutes.

0 23 ** 6/apps/bin/qtrend. Sh
Execute/apps/bin/qtrend. Sh at every Saturday.

3.1.3 crontab command options

Crontab [-u user]-E-l-R

-U User Name
-E: edit the crontab file
-L list the contents of the crontab file
-R: Delete the crontab file.

3.1.4 create a crontab file
Crontab faintbearcron
3.1.5 list crontab Files
Crontab-l

Crontab-L> $ home/faintbearcron
(Backup)
3.1.6 edit the crontab file
Crontab-e
3.1.7 Delete the crontab file
Crontab-R
3.1.8 restore the lost crontab file
Crontab <FILENAME>
<FILENAME> indicates the file name of the copy in the $ home directory.