One ,expect

1. expect summary

Based on the tcl A tool based on language , It is often used for automatic control and testing , solve shell Interaction related issues in scripts

The main role ：

1. Track instructions that require interaction

2. Capture keywords that prompt interaction

3. Incoming interactive instruction , Enter to execute

2. expect Basic installation of

• expect It's a program , So it also needs to be installed in advance before it can be used

[[email protected]]# rpm -q expect
[[email protected]]# rpm -q tcl 
[[email protected]]# yum install expect -y // install expect When the tcl Install as a dependent package 

3. Basic commands

3.1 Script interpreter

expect The script first introduces the file , Indicate which one is used shell
#!/usr/bin/expect

3.2 spawn

spawn Usually followed by a Linux Carry out orders , Open a conversation 、 Start the process , And track subsequent interaction information .
 for example ：
	spawn passwd root

3.3 expect

• Judge whether the last output result contains the specified string , If so, return immediately , Otherwise, it will wait for the timeout to return
• Can only be captured by spawn The output of the started process
• Used to receive output after command execution , And then match the expected string

3.4 send

• Send string to process , Used to simulate user input ; This command does not automatically enter to wrap lines , Generally, we need to add \r ( enter ） perhaps \n

 Mode one ：
	expect " password "{
     send "abc123\r" }		// The same line send There should be {
    }

 Mode two ：
	expect " password "
	send "abc123\r"						// Line break send Part of it doesn't need to have {
    }

 Mode three ：
	expect Supports multiple branches 
	expect		// Just match one of the cases , Execute corresponding send Statement to exit the expect sentence 
	" password 1"{
     send "abc123\r" }
	" password 2"{
     send "123456\r" }
	" password 3"{
     send "123123\r" }

3.5 Terminator

• expect eof

Indicates the end of the interaction , Waiting for execution to end , Return to the original user , And spawn Corresponding .
For example, switch to root user ,expect The script default is to wait 10s, When the command is finished , Default stay 10s after , Automatically switched back to the original user

• interact

Keep interactive after execution , Give control to the console , Will stay at the target terminal without returning to the original terminal , At this time, it can be operated by hand ,interact The last order doesn't work , such as interact Add exit, It's not going to quit root user . And if not interact Will exit after login , Instead of staying on the remote terminal .

• Be careful ：expect eof And interact You can only choose one

3.6 set

expect  The default timeout is 10 second , adopt  set Command to set the session timeout , If the timeout is not limited, it should be set to -1.
 example : 
	set timeout 30

3.7 exp_continue

Attached to a expect After the judgment , After the item is matched , Can continue to match the expect- Determine other items in the statement .exp_continue Similar to... In a control statement continue sentence . It means to allow expect Continue down the instruction

 for example : The following example will determine if there is yes/no  or *password. If the match  yes/no  The output  yes And execute judgment again ;
 If the match *password The output abc123 And end the paragraph expect sentence .

expect{
    
	"(yes/no)"
	{
     send "yes\r";exp_continue;}
	"*password"
	{
     set timeout 300;send "abc123\r";}
}
# Be careful : Use exp continue when , If tracking is like passwd This is the command to end the process after entering the password ,expect{} Don't add expect eof
# because spawn At the end of the process, it will default to expect send out eof, It will lead to the following expect eof Error report in execution 

# notes ： Indicates that users are allowed to interact , Always keep the call back connection 

3.8 send user

• send user Represents the echo command , amount to echo

3.9 Receiving parameters

expect Scripts can accept from bash Parameters passed from the command line , Use [lindex $argvn] get .
 among n from o Start , They are the first , the second , Third .. Parameters . example :
set hostname [ lindex $argy 0 ]
 amount to hostname=$1

set password [ lindex $argy 1 ]
 amount to password=$2

4. use expect Write a script

example ：ssh No interactive login to the remote server

[[email protected] ~]# cat ss.sh
#!/usr/bin/expect
spawn ssh [email protected]
expect {
    
     "(yes/no)*"
    {
     send "yes\r"; exp_continue; }
    "password:"
     {
     send "123456\r"; }
}
interact

4.1 stay shell Call in script expect

#!/bin/bash
username=$1

useradd $username

/usr/bin/expect <<-EOF spawn passwd $username expect { " The new code " // Be careful ： The obtained content and the sent content cannot be on the same line, otherwise the execution will not succeed  {send "123456\r";exp_continue} " Retype the new password " {send "123456\r";} } EOF

 The verification results ：
[[email protected]]# ./add.sh wangwu
spawn passwd wangwu
 Change user  wangwu  Password  .
 new   password ：
 Invalid password ：  The password is less than  8  Characters 
 Reenter the new   password ：
passwd： All authentication tokens have been successfully updated .

3456\r";}
}
EOF

The verification results ：
[[email protected]]# ./add.sh wangwu
spawn passwd wangwu
Change user wangwu Password .
new password ：
Invalid password ： The password is less than 8 Characters
Reenter the new password ：
passwd： All authentication tokens have been successfully updated .