How to use Crontab in CentOS

The crontab service requires root permissions. The following is an official explanation: SHELL =/bin/bashPATH =/sbin:/bin:/usr/sbin: /usr/binMAILTO = rootHOME =/# Fordetailsseeman4crontabs # Exampleofjobdefinition:

The crontab service requires the root permission for execution.

The following is an official explanation:

SHELL =/bin/bash
PATH =/sbin:/bin:/usr/sbin:/usr/bin
MAILTO = root
HOME =/


# For details see man 4 crontabs


# Example of job definition:
#. ---------------- Minute (0-59)
# |. ----------- Hour (0-23)
# |. ---------- Day of month (1-31)
# |. ------- Month (1-12) OR jan, feb, mar, apr...
# |. ---- Day of week (0-6) (Sunday = 0 or 7) OR sun, mon, tue, wed, thu, fri, sat
# |
# ***** User-name command to be executed

The usage is as follows:

New scheduling task

Run the crontab-e command to edit the scheduled task to be executed. you can also edit the content in the/etc/crontab file. The example is as follows: ceshi in this example. sh is the script stored in the/root directory.

* ***/Root/ceshi. sh: execute ceshi. sh once per second

30 5 ***/root/ceshi. sh execute ceshi. sh at 05:30 every day

** 1 1 */root/ceshi. sh: execute ceshi. sh every month on January 1, January 1.

30 5 */10 ** root/ceshi. sh run ceshi. sh at 05:30 every 10 days.

30 5 ** 1/root/ceshi. sh run ceshi. sh every Monday 05:30

View scheduled tasks

Run: crontab-l

Delete a scheduling task

Run: crontab-r

Save the output result of the scheduling task

Add>/path/file 2> & 1 after the task

For example

30 5 */10 ** root/ceshi. sh>/root/record.txt 2> & 1

Note: 2> & 1 redirects all execution results to the target file.