Linux Shell Study Notes day 5

Day 5: function and Task Scheduling

Function advantages

Divide and conquer f

Collaboration

Convenient Management

Easy to maintain

Function Structure

Function Name ()

{

Command 1

Command 2

Command 3

}

Function parameter transfer

Passing parameters to a function is like using special variables $1, $2, $3… in a general script... $9 is the same. The function gets the passed parameters and returns the original parameters to the shell script. Therefore, it is best to reset the variable in the function to save the passed parameters. In this way, if the function has a slight error, you can quickly track it through the localized variable name.

Function File

When you use some frequently-used functions on your mobile phone, you can put them into the function file and load the file into shell.

The file header should contain statements #! /Bin/bash: the file name can be selected at will, but it is best to have some practical relationship with related tasks.

#! /Bin/bash

# Note

Function1 ()

{

}

Function file example

Functions. main

#! /Bin/bash

# Functions. main

Findit ()

{

If [$ #-lt 1]; then

Echo "usage: findit file"

Return 1

Fi

Find/-name $1-peint

}

Function example

. Functions. main load function

Set to check whether the function is loaded

Findit call Function

Findit functions. main calls the Function

Unset findit Delete findit Function

Single Task Scheduling

At is used to schedule a one-time task at a specified time.

Format:

At [Option] time

-F Read commands or scripts from files

-M sends an email to the user after the job is completed.

-V: display the job execution time

Start and Stop a service

Service atd start

Service atd stop

Delete task atrm

Example of one-time Task Scheduling

At-f mycrontest. sh 10: 00 pm tomorrow

At-f mycrontest. sh 2: 00 am Tues

At-f mycrontest. sh 2: 00 pm Feb

At-f mycrontest. sh 2: 00 pm next we

Cyclic Scheduling crontab

Crontab can regularly run some job tasks. It is a script that is automatically started every time linux is started.

Format:

Crontab [-e [UserName] |-l [UserName] |-r [UserName]

-E. Execute the text editor to set the time table.

-L list text editors to set time tables

-R: Delete the current time table.

-V: list the statuses of user cron jobs

Crontab Configuration

Crontab can regularly run some job tasks. It is a script that is automatically started every time linux is started.

Global configuration file/etc/crontab

User configuration file/var/spool/cron/

Crontab User Configuration

/Etc/cron. allow

/Etc/cron. deny

/Etc/crontab

SHELL =/bin/bash

PATH =/sbin;/bin:/usr/sbin;/usr/bin

MAILTO = root

HOME =/

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

02 4 *** root run-parts/etc/cron. daily

22 4 ** 0 root run-parts/etc/cron. weekly

42 41 ** root run-parts/etc/cron. monthly

Five fields: hour, day, month, week

Crontab Application Scenario

Test whether to connect to the gateway 192.168.1.254 every five minutes */5 ****

User alex backs up samba configuration files at every Sunday.

0 12 ** 0 tar-czvf samba.tar.gz/etc/samba/smb. conf

Summary

Function advantages

Collaboration

Easy to check

Advanced and flexible

Task Scheduling Method

At

Crontab