Shell Loop Statement Application Example

1 for statement

Syntax format

For variable in value (or loop condition)

Do

Command

Done

Send mail to multiple users

#！ /bin/bash

Domain=163.com

For user in Tom Hom Jem

Do

Mail-s "Happy New Year" [email protected] $domain </var/log/messages

Done

To print 9*9 multiplication formulas

#!/bin/bash

For i in {1..9}

Do

For ((j=1,j<=i,j++))

Do

printf "%-8s" $j * $i =$ ((j*i))

Done

Echo

Done

2 While statement

Syntax format

While condition do command done

While read-r command done < file

Add 20 users in bulk, user name usern,n to 1 to 20 digits

#!/bin/bash

U=1

While [$u-le 20]

Do

Useradd user${$u}

u=$ ((u+1))

Done

Read the print NIC profile by line

#!/bin/bash

File=/etc/sysconfig/network-scripts/ifcfg-eth0

While Read-r line

Do

Echo $line

Done < $FILE

3 until statements

Syntax format

Until condition do command done

Bulk delete users, user name Usern,n 1 to 20 digits

#!/bin/bash

U=20

Until [$u-eq 0]

Do

Userdel user${$u}

u=$ ((u-1))

Done

4 SELECT statement

Generate a Query menu with SELECT

#！ /bin/bash

echo "Where is You"

Select Var in "Shenzhen" "Guangzhou" "Meiguo" "Xianggang"

Do

Break

Done

echo "You is from $var"

5 Control statements

Shift shifts the position parameter one bit to the left, that is, after shift is executed, it becomes $

Countinue interrupts the current loop and enters the next loop

Break ends the entire loop

Exit to end the run of the script

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Shell Loop Statement Application Example