Setup crontab Configuration Guide for Linux timed tasks

To create a cron service for the current user

1. Type CRONTAB-E edit crontab service file

For example, the contents of the file are:

*/2 * * * */bin/sh/home/admin/jiaoben/buy/deletefile.sh

Save the file and exit

*/2 * * * */bin/sh/home/admin/jiaoben/buy/deletefile.sh

*/2 * * * * This field allows you to set when to execute the script

/bin/sh/home/admin/jiaoben/buy/deletefile.sh This field can set the script you want to execute, note here that bin/sh refers to the path that the script holds after the command that runs the script

2. See if the Crontab service under this user was created successfully with the CRONTAB-L command

3. Start the crontab service

General start-up service with/sbin/service Crond start if the root user's cron service can be crond start with sudo services, it is also important to note that the commands for the different versions of the Linux system-initiated service are different, like my virtual machine only needs sudo service cron Restart can be started if you type service cron start directly under root

4. See if the service is already running with Ps-ax | grep cron

5. Crontab command

The Cron service provides the crontab command to set the Cron service, and here are some of the parameters and instructions for this command:

Crontab-u//Set a user's Cron service, which is usually required by the root user when executing this command
CRONTAB-L//list details of a user cron service
Crontab-r//Delete a cron service with no users
CRONTAB-E//Edit a user's cron service
For example, root to view your cron settings: Crontab-u root-l
Again, for example, Root wants to delete Fred's cron settings: Crontab-u fred-r
When editing the Cron service, the edited content has some formatting and conventions, input: Crontab-u root-e
Enter VI edit mode, the content of the edits must conform to the following format: */1 * * * * ls >>/tmp/ls.txt
Crond resident command for task scheduling
Crond is a command that Linux uses to execute programs on a regular basis. When the operating system is installed, the default is to start the

The Task Dispatch command. The Crond command periodically checks if there is any work to be done,

The work will be performed automatically.

6. crontab Command options:

-u Specifies a user

-l lists a user's task schedule

-R Delete a user's task

-e Edit a user's tasks

7. cron file Syntax:

Hour of the week order

0-59 0-23 1-31 1-12 0-6 Command (value range, 0 for Sunday One a row corresponds to a task)

Remember the meanings of several special symbols:

"*" represents a number in the range of values,
"/" stands for "every",
"-" represents a number to a number,
"," separate a few discrete numbers

8. Writing the Task Scheduler settings file
The CRONTAB-E command can be used to edit, edit the corresponding user's cron file under/var/spool/cron, or modify the/etc/crontab file directly.
The specific format is as follows:
Minute Hour Day Month Dayofweek command
Minutes hours days months days per week order
Each field represents the following meanings:
Minute the first few minutes of every hour to perform the task
Hour the first few hours of the day to perform this task
Day of the month to perform the task
Month months of the year to perform this task
DayOfWeek the day of the week to perform the task
Command Specifies the program to execute
In these fields, other fields are optional except that the Command is a field that must be specified each time.

field, depending on your needs. For a field that is not specified, "*" is used to fill its position.
Examples are as follows:
5 * * * ls Specifies the first 5 minutes of every hour to execute the LS command
5 * * * ls specifies the 5:30 execute LS command per day
7 8 * * ls specifies 7:30 minutes of 8th per month to execute the LS command
5 8 6 * ls specifies that the LS command be executed every June 8 5:30
6 * * 0 ls specifies 6:30 execute ls command per Sunday [Note: 0 for Sunday, 1 for Week 1,

And so on, can also be expressed in English, Sun said Sunday, Mon said Monday and so on. ]

3 10,20 * * ls 3:30 for each month 10th and 20th executes the LS command [note: "," used to connect multiple discontinuous periods]

8-11 * * * ls command is executed at 25 minutes per day at 8-11 Pips [Note: "-" used to connect a continuous period of time]

*/15 * * * * ls is executed every 15 minutes with the LS command [i.e. No. 0 15 30 45 60 minutes per hour to execute the LS command]

6 */10 * ls command is executed every 10 days each month (1, 11, 21, 31st). 6:30 executes the LS command once. ]

Every day 7:50 executes all executables in the/etc/cron.daily directory as root

7 * * * Root run-parts/etc/cron.daily [Note: The Run-parts parameter indicates that all executables in the following directory are executed. ]

9. New Scheduling task

There are two ways to add a dispatch task:
1), at the command line input: CRONTAB-E and then add the corresponding task, Wq save the disk to exit.
2), directly edit the/etc/crontab file, that is, vi/etc/crontab, add the corresponding task.

10. View scheduling Tasks
Crontab-l//List all current Scheduled tasks
Crontab-l-u JP//List all scheduling tasks for user JP

11. Delete Task Scheduling work
Crontab-r//Delete all task scheduling work

12. Steering of task scheduling execution results
Example 1: Execute the LS command 5:30 every day and output the results to the/jp/test file
5 * * * ls >/jp/test 2>&1
Note: 2>&1 indicates execution results and error messages.
Edit/etc/crontab File Configuration cron

Cron service every minute not only to read all the files within/var/spool/cron, but also to read a/etc/crontab, so we configure this file can also use the Cron service to do something. The crontab configuration is for a user, while the edit/etc/crontab is a task for the system. The file format for this file is:

Shell=/bin/bash

Path=/sbin:/bin:/usr/sbin:/usr/bin

Mailto=root//If an error occurs, or if there is data output, the data is sent to this account as an email

home=///user-run path, here is the root directory
# Run-parts

* * * * * root run-parts/etc/cron.hourly//hourly execution

Scripts within the/etc/cron.hourly

4 * * * Root run-parts/etc/cron.daily//daily execution of scripts within/etc/cron.daily

4 * * 0 root run-parts/etc/cron.weekly//weekly execution of scripts within/etc/cron.weekly

4 1 * * Root run-parts/etc/cron.monthly//monthly to execute scripts within/etc/cron.monthly
Attention to the "run-parts" parameter, if you remove this parameter, you can write a script name to run, instead of the folder name

For example:

1) in the command line input: Crontab-e then add the corresponding task, Wq save the disk to exit.

2) Edit the/etc/crontab file directly, i.e. Vi/etc/crontab, add the corresponding task
2 * RM-RF/MNT/FB

Setup crontab Configuration Guide for Linux timed tasks