No interaction in shell programming

Posted by corporateboy on Sun, 27 Feb 2022 05:54:00 +0100

Here Document interaction free

Cross free mutual definition

Here Document overview:

Use I/O redirection to provide a list of commands to interactive programs or commands, such as ftp, cat, or read commands

Here Document is an alternative to standard input, which can help script developers not use temporary files to build input information, but directly produce a file in place and use it as standard input for commands. Here Document can be used with non interactive programs and commands

Syntax format

Syntax format

command << sign

....
Input content
......

sign

Precautions for use of Here Document:

The tag can use any legal character (the common character is EOF)

The mark at the end must be written in the top grid, and there must be no characters (including spaces) in front of it

There must also be no characters (including spaces) after the tag at the end

Spaces before and after the opening mark are omitted

example

1. Output the input command line directly

2. Save the input content to a file

3. Input and save the additional content to the file

Here Document variable setting

Here Document also supports the use of variables. If variables are used between tags, the variable value will be replaced first. If you want to write some content to a file, in addition to the conventional method, you can also use Here Document. If the written content contains variables, the variables should be replaced with the actual values before writing the file, and the writing is completed in combination with the cat command

Example:

1.When writing a file, the variable will be replaced with the actual value first, and then combined cat The command completes writing

2.Support variable replacement
 When writing a file, the variable will be replaced with the actual value first, and then combined cat The command completes writing

[root@localhost ~]# vim kk.sh

#!/bin/bash
doc_file="yy.txt"
i="0.0"
cat > $doc_file << EOF
kuai le $i
EOF

echo  this is $i

[root@localhost ~]# chmod +x kk.sh
[root@localhost ~]# ./kk.sh 
this is 0.0
[root@localhost ~]# cat yy.txt 
kuai le 0.0

3. Assign a value to a variable as a whole, and then print the variable value through echo command

[root@localhost ~]# vim kk.sh

#!/bin/bash
ar="So Happy"
arr=$(cat << EOF
 to be on holiday
$ar 
EOF
)
echo $arr

[root@localhost ~]# chmod +x kk.sh

[root@localhost ~]# ./kk.sh 
to be on holiday So Happy

Format control

Turn off the function of variable replacement and output the characters as they are without any modification or replacement

Example:

1. Turn off variable replacement: add a single quotation mark to the tag to turn off variable replacement

[root@localhost ~]# vim kk.sh

#!/bin/bash
i="hello"
kk=$(cat <<'EOF'
$i
EOF

)
echo $kk

[root@localhost ~]# chmod +x kk.sh 
[root@localhost ~]# ./kk.sh 
$i

2. Remove the tab character before each line
Add '-' before the mark in the first line, which means to suppress the role of the first tab in each line

[root@localhost ~]# vim kk.sh

#!/bin/bash
cat <<EOF
        hello world
EOF
cat <<-EOF
        hello world
EOF

[root@localhost ~]# chmod +x kk.sh 
[root@localhost ~]# ./kk.sh 
	hello world
hello world

multiline comment

Bash's default annotation is "#". This annotation method only supports single line annotation. In the work of shell script, bash will ignore any string to the right of "#". The introduction of Here Document solves the problem of multi line annotation.
":" (colon) represents an empty command that does nothing. The contents of the middle mark area will not be executed and will be ignored by bash, so the effect of batch annotation can be achieved

[root@localhost ~]# vim kk.sh

#!/bin/bash
a=123456
: <<-EOF
this is 
test line
echo $a
EOF
echo "0.0"

[root@localhost ~]# chmod +x kk.sh 
[root@localhost ~]# ./kk.sh 
0.0

Expect

Expect definition

A tool based on tcl

For automatic control and testing

Solve interaction related problems in shell scripts

Expect installation

rpm -q expect

rpm -q tcl

yum install -y expect

Expect related commands

script interpreter

The expect script first introduces a file to indicate what kind of shell is used
#!/usr/bin/expect
spawn

Spawn is usually followed by a Linux execution command, which means to start a session, start a process, and track the subsequent interaction information, for example: spawn passwd root

expect

Judge whether the last output result contains the specified string. If so, it will be returned immediately. Otherwise, it will be returned after the timeout time;
Only the output of the process started by spawn can be captured;
It is used to receive the output after the command is executed, and then match the expected string
send

Send a string to the process to simulate the user's input;

This command cannot automatically enter and line feed. Generally, it needs to add \ r (enter) or \ n

Terminator

1.expect eof

Indicates the end of interaction, waiting for the end of execution, returning to the original user, and spawn corresponding

For example, switch to root Users, expect By default, the script waits for 10 minutes s When the command is executed, it will stay 10 by default s After, it automatically switches back to the original user

2.interact

1.After execution, keep the interactive state and hand over the control to the console. It will stay at the target terminal without returning to the original terminal. At this time, it can be operated manually, interact Life after death.It doesn't work;

such as interact Add after exit´╝îIt won't quit root User. And if not interact Then it will exit after login, rather than stay on the remote terminal.

use interact Will remain at the terminal without returning to the original terminal;

set

expect The default timeout is 10 seconds set The command can set the session timeout. If the timeout is not limited, it should be set to-1

example: set time out 30

exp_continue

exp_ continue Similar to in a control statement continue sentence. Express permission expect Continue to execute the instruction downward
send_users

Indicates echo commands and echo identical
 Receive parameters

The expect script can accept passing parameters from the bash command line and obtain them using [lindex $argv n]. Where you start from 0 and represent the first, second and third... Parameters respectively
set hostname [lindex $argv 0]
Equivalent to hostname=

set password [lindex $argv 1]
Equivalent to passswd=

example

1.ssh has no interactive login to the remote server

[root@localhost ~]# vim kk.sh

#!/usr/bin/expect
spawn ssh root@192.168.146.10

expect {
        "password:"
        { send "123456\r"; }
}

interact

[root@localhost ~]# chmod +x kk.sh 
[root@localhost ~]# ./kk.sh 
spawn ssh root@192.168.146.10
root@192.168.146.10's password: 
Last login: Mon Feb 14 12:12:35 2022 from 192.168.146.20
[root@localhost ~]# 

2. Operate on the remote login server and then exit

[root@localhost ~]# vim kk.sh

#!/usr/bin/expect
spawn ssh root@192.168.146.10

expect {
        "password:"
        { send "123456\r"; }
}

expect "#"
send "ls\r"
send "ifconfig ens33\r"
send "exit\r"

expect eof

[root@localhost ~]# chmod +x kk.sh 
[root@localhost ~]# ./kk.sh 
spawn ssh root@192.168.146.10
root@192.168.146.10's password: 
Last login: Mon Feb 14 16:42:02 2022 from 192.168.146.20
[root@localhost ~]# ls
anaconda-ks.cfg  initial-setup-ks.cfg
[root@localhost ~]# ifconfig ens33
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.146.10  netmask 255.255.255.0  broadcast 192.168.146.255
        inet6 fe80::33b3:2fac:9c4b:5e89  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:01:3e:a5  txqueuelen 1000  (Ethernet)
        RX packets 210547  bytes 310074122 (295.7 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 98024  bytes 5939781 (5.6 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@localhost ~]# exit
 Log out
Connection to 192.168.146.10 closed.

3. The second way to write SSH free interactive login

[root@localhost ~]# vim kkk.sh

#!/usr/bin/expect

set timeout 10
log_file kkk.log
log_user 1
set ip [lindex $argv 0]
set password [lindex $argv 1]
spawn ssh root@${ip}
expect {
        "(yes/no)"
        {send "yes\r"; exp_continue} "*password"
        {send "$password\r"}

}
interact
  
[root@localhost ~]# chmod +x kkk.sh 
[root@localhost ~]# ./kkk.sh 192.168.146.10 123456
spawn ssh root@192.168.146.10
root@192.168.146.10's password: 
Last login: Mon Feb 14 21:57:36 2022 from 192.168.146.20
[root@localhost ~]#       
[root@localhost ~]# vim yong.sh

#!/bin/bash

username=$1

useradd $username

/usr/bin/expect <<-EOF

spawn passwd $username
expect {
        "password"
        {send "123456\r";exp_continue}
        "New password"
        {send "123456\r";}
}
EOF

[root@localhost ~]# chmod +x yong.sh 
[root@localhost ~]# ./yong.sh nan
spawn passwd nan
 Change user nan Your password.
123456
 New password:
Invalid password: password is less than 8 characters
 Re enter the new password:
passwd: All authentication tokens have been successfully updated.
[root@localhost ~]# vim ftp.sh 

#!/usr/bin/expect -f

set timeout 10
spawn ftp 192.168.146.10
expect "Name*"
send "ftp\r"
expect "Passwd:*"
send "\r"
expect "ftp>*"
interact

[root@localhost ~]# chmod +x ftp.sh 
[root@localhost ~]# ./ftp.sh 
spawn ftp 192.168.146.10
Connected to 192.168.146.10 (192.168.146.10).
220 (vsFTPd 3.0.2)
Name (192.168.146.10:root): ftp
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> 

summary

1. Usage of here document
2.Expect basic commands
3.Expect usage

Topics: Linux ssh server