Linux Shell Learning Notes fourth Day _ other

The script for this lesson is also shared in the share.

Day Fourth: Circular structure

Content outline:

application Example Analysis

For loop

While loop

The principle of the For loop

Achieve effect

Modified according to yesterday's menu. Selecting 1, 2, 3 also prompts you to continue with the selected feature. Option 4 is still an exit operation.

For variable in list variable lists pool

Todo

Command1

Command2

Done

Instance One

forlist.sh

#!/bin/bash

#for with List

For loop in 1 2 3 4 5 variables that define loops 1 2 3 4 5 is a list of variables

Todo

Echo ${loop}

Done

When not followed, that is equal to 0, then stop the loop.

Example Two

Var.txt to prove that a variable is a carriage return or a space-delimited, unless double quotes are specifically delimited

1 22

3

4

5

6

forfile.sh

#!/bin/bash

For loop in ' Cat Var.txt '

Todo

Echo ${loop}

Done

Example Three

Write a script to automatically generate a class C IP address segment

The IP address segment network portion is specified by the user

./ipaddr.sh 192.168.1

192.168.1.1

192.168.1.2

......

192.168.1.254

#!/bin/bash

For IP in ' seq 1 254 ' seq produces a step of 1, or 1-254 value

Todo

Echo ${1}.${ip}

Done

For loop nesting

For variable name 1 in List 1

Todo

For variable name 2 in List 2

Todo

Command 1

...

Done

Done

Example Four

Write a script to automatically generate a class C IP address segment

The IP address segment network portion is specified by the user and the host end is specified by the user

./ipaddr2.sh 192.168.1 100

192.168.1.1

192.168.1.2

......

192.168.168.1.100

#!/bin/bash

For IP4 in ' seq 1 ${2} '

Todo

Echo ${1}.${IP4}

Done

#!/bin/bash

For IP3 in ' SEQ 1 5 '

Todo

For IP4 in ' seq 1 ${2} '

Todo

Echo ${1}.${IP3}.${IP4}

Done

Done

The principle of the while loop

Boundary test = condition test

True and false test.

If it has been true, it will not stop, dead loop.

The while format

While condition

Todo

Command 1

Command 2

Done

While application scenario

While Dead loop

While ["1" = "1"]

Todo

...

Done

While condition loop

While [${num}–lt 10] is less than 101 straight loop

Todo

...

Done

Solve the problem.

Use while to produce a dead loop

Exits to exit the entire script

menu-while.sh

#!/bin/bash

While ["1" = "1"]

Todo

Clear

echo "—————— –menu ————— –"

echo "1" Show Time "

echo "2) CPU Load"

echo "3" Memory free "

echo "0 Exit"

echo "—————————————— –"

Echo-n "Enter you chose [0-3]:"

Read chose

Case ${chose} in

0) exit;;

1) date +%t;;

2) Uptime | Awk-f ' [,:] ' {print $} ';;

3) free-m | awk ' $1== ' Mem: "{print $}";;

*) echo "This isn't between 0-3.";;

Esac

Echo-n "Do you contine [y/n]:"

Read Contine

if ["${contine}" = = "n"-o "${contine}" = = "N"]

Then

Exit

Fi

Done

Practice after class

Write a script that produces a level two menu.

The first level has three function items: CPU info, memory info, exit

CPU Info There are four feature items in the second level: Show CPU type, show CPU load, return main menu, exit script

Memory There are four functional items in the second level: Display the memory surplus, the remaining amount of swap, return to the main menu, exit the script.

Summary review

Attributes for A For loop

He is not the same as C and Java, not according to the judgment statement to control the number of times

For implementing a dead loop is difficult. While doing a dead loop is simple.