Shell script for Loop

Shell Loop: For

The number of cycles is fixed

=====================

Shell:

For variable name [in value list]

Do

Loop body

Done

C Language:

for (initial value; condition; step))

Do

Loop body

Done

=====================

Shell loop: While until

The number of cycles is not necessarily fixed

can be fixed

Can not be fixed

While statement:

While condition test

Do

Loop body

Done

Function: When the condition test is established (the condition test is true), the loop body is executed.

=====================

Until statement:

Until condition test

Do

Loop body

Done

Function: When the condition test is established (the condition test is false), the loop body is executed.

=====================

Case 1: The value of the cyclic output variable i. The following example can be tested directly at the command line.

For i in a B c D

Do

Echo $i

Done

=====================

Case 2: Batch ping test host, concurrency mode.

VI pi.sh script code is as follows

#!/usr/bin/env Bash

Trap "echo ok;exit 3" INT

For i in {1..254}

Do

(

ip=192.168.100. $i

PING-W.2-I.1-C1 $ip | Grep-q ' TTL '

[ $? -eq 0] && echo "$ip is up" | | echo "$ip is down"

) &

Done

Wait

echo "Finish ...."

Test efficiency: Time SH pi.sh

=====================

Case 1: Write script s1.sh. Prompts the user to enter a feature option and executes the associated command after carriage return.

VI s1.sh script code is as follows

#!/bin/bash

#trap "Echo ok;exit;" HUP INT QUIT TSTP

While:

Do

Cat <<-eof

1.web1

2.web2

3.mysql1

Eof

Read-p "Input number[1-3]:" num

Case $num in

1)

#ssh [email protected]

Ping-c 4 127.0.0.1

;;

2)

#ssh [email protected]

Ping-c 4 127.0.0.2

;;

3)

#ssh [email protected]

Ping-c 4 127.0.0.3

;;

‘‘)

True

;;

*)

echo "Error"

Break

;;

Esac

Done

----------------------------------------

Case 3: Multi-host push public key.

VI skey.sh

#!/usr/bin/env Bash

#get IP

>/tmp/ip_yes.txt

>/tmp/ip_no.txt

if [!-F ~/.ssh/id_rsa];then

Ssh-keygen-t rsa-p ""-F ~/.ssh/id_rsa

Fi

Rpm-q expect &>/dev/null

If [$?-ne 0];then

Yum Install-y expect

Fi

For i in {1..254}

Do

{

ip=192.168.100. $i

PING-W.2-I.1-C1 $ip &>/dev/null

If [$? -eq 0];then

echo "$ip is up" | Tee-a/tmp/ip_yes.txt

/usr/bin/expect <<-eof

Set Timeout 10

Spawn Ssh-copy-id $ip

Expect {

"Yes/no" {send "yes\r"; Exp_continue}

"Password:" {send "012\r"}

}

Expect EOF

Eof

Else

echo "$ip is down" | Tee-a/tmp/ip_no.txt

Fi

}&

Done

Wait

echo "Finish ...."

=====================

Case 4:{}& Concurrently batch modify the Sshd_config configuration file on the SSH server, the SELinux profile, and turn off the firewall.

1th Step: Prepare the/opt/ip.txt file.

Cat >/opt/ip.txt <<eof

192.168.10.2

192.168.10.25

192.168.10.26

Eof

2nd step: Create a script.

VI ssh.sh

#!/usr/bin/env Bash

For IP in $ (cat/opt/ip.txt)

Do

{

SSH $ip "Sed-ri '/^ #UseDNS/c\usedns no '/etc/ssh/sshd_config"

SSH $ip "Sed-ri '/^gssapiauthentication yes/c\gssapiauthentication no '/etc/ssh/sshd_config"

SSH $ip "service iptables stop;chkconfig iptables off"

SSH $ip "Sed-ri '/^selinux/c\selinux=permissive '/etc/selinux/config"

SSH $ip "Setenforce 0"

}&

Done

Wait

echo "Finish ..."

=====================

Case 4: Multi-host Change password.

VI modify_passwd.sh

#!/usr/bin/env Bash

#change Password

#v1.0 by Flyer 08/10/2017

Read-p "Please input a New Password:" Pass

For i in {1..100}

Do

{

ip=192.168.100. $i

PING-C1-W1 $ip &>/dev/null

If [$?-eq 0];then

SSH $ip "echo $pass | passwd--stdin Root "&>/dev/null

If [$? -eq 0];then

echo "$ (date +%f) $ip up" >>/tmp/ok.txt

Else

echo "$ (date +%f) $ip down" >>/tmp/fail.txt

Fi

Else

echo "$ (date +%f) $ip down" >>/tmp/fail.txt

Fi

}&

Done

Wait

echo "All OK ..."

=====================

Case: for bulk user creation.

1th Step: Prepare the user list file.

Cat >/tmp/user.txt <<eof

Tom

Jack

Lucy

Eof

2nd step: Create a script file.

VI useradd.sh

#!/usr/bin/env Bash

#useradd2

pass=111

Red_col= "\e[1;31m"

Reset_col= "\e[0m"

If [$#-eq 0];then

echo "Usage: $ (basename $) file"

Exit 1

Fi

if [!-F $];then

echo "Error file!"

Exit 2

Fi

For user in $ (cat $)

Do

ID $user &>/dev/null

If [$? -eq 0];then

echo "$user already Exites"

Else

Useradd $user

echo "$pass" | passwd--stdin $user &>/dev/null

If [$?-eq 0];then

Echo-e "${red_col}${user}${reset_col} create"

Fi

Fi

Done

3rd Step: Test the syntax and test the execution of the script.

Sh-n useradd.sh

chmod +x useradd.sh

./useradd.sh/tmp/user.txt

===============================================

Case: Create a user in bulk.

VI useradd3.sh

#!/bin/bash

While:

Do

Read-p "Please enter name & password & num & Mode[add/del]:" Name pass num mode

printf "User information:

-----------------------------

User name: $name

User passwd: $pass

User number: $num

User mode: $mode

-----------------------------

"

Read-p "Is you sure?" [y/n]: "Action

If ["$action" = "Y"];then

Break

Fi

Done

Case $mode in

Add

For I in $ (seq-w $num)

Do

User=${name}${i}

Useradd $user

echo "$pass" | passwd--stdin $user &>/dev/null

If [$?-eq 0];then

echo "$user is created"

Fi

Done

;;

Del

For I in $ (seq-w $num)

Do

User=${name}${i}

Userdel-r $user &>/dev/null

If [$?-eq 0];then

echo "$user is deleted"

Fi

Done

;;

*)

echo "Program Exit"

Exit 0

;;

Esac

-----------------------------

Case: Write a basic script for a batch ping with a for C style.

VI pi2.sh

#!/bin/bash

For ((i=1;i<=10;i++))

Do

{

ip=192.168.100. $i

Ping-c 1-w1 $ip |grep ttl

}&

Done

Wait

echo "Finish ..."

=============================

Case: While automatically switching gateways.

VI gw.sh

#!/bin/bash

gw1=192.168.100.3

gw2=192.168.100.2

While:

Do

IP r del Default

IP r add via $GW 1

While PING-C1 $GW 1 &>/dev/null

Do

Sleep 1

Done

IP r del Default

IP r add default via $GW 2

Until PING-C1 $GW 1 &>/dev/null

Do

Sleep 1

Done

Done &

This article is from the "Network Technology World" blog, please be sure to keep this source http://1364952.blog.51cto.com/1354952/1955276

Shell script for Loop