Shulou(Shulou.com)06/01 Report--

This article introduces how to use the interaction-free tool ecpect in the shell script, the content is very detailed, interested friends can refer to it, I hope it can be helpful to you.

Overview of Expect

Expect is a tool based on tcl, and Expect is a tool for automatic control and testing. Mainly solve the problem of non-interactive in shell script. It is very helpful for large-scale Linux operation and maintenance.

In Linux operation and development, we often need to log on to the server remotely. The login process is an interactive process, and we may need to enter yes/no, password and other information. To simulate this input, you can use an Expect script.

Expect installation

Yum install expect-y install the expect service

Expect basic command

1.send: sends a string to the process to simulate the user's input

This command cannot automatically enter to change the line, and usually add\ r (enter).

2.expect

An internal command of expect to determine whether the specified string is included in the last output, and return immediately if so, otherwise it will return after waiting for the timeout.

Only the output of processes started by spawn can be captured.

3.spawn: start the process and track subsequent interactions.

4.interact: maintain the interactive state after the execution is completed, and hand over the control to the console

5.Timeout: specify the timeout, and continue to execute subsequent instructions in the past

Unit is: seconds

Timeout-1 for never timeout

By default, timeout is 10 seconds

6.exp_continue

Allow expect to continue downward execution

7.send_user

Echo command, equivalent to echo

8.$argv parameter array

The expect script can accept parameters passed from bash, which can be obtained using [lindex,$argv n], where n starts at 0 and represents the first and second, respectively.

9.Expect scripts must end with interact or expect eof, and expect eof is usually enough to perform automated tasks

Expect eof is waiting for the end flag, and the command initiated by spawn produces an eof tag at the end, which expect eof is waiting for.

Expect syntax

Single grammatical branch

Expect "password" {send "mypassword";}

Multi-branch grammatical structure

Expect {"aaa" {send "AAA\ r"} "bbb" {send "BBB\ r"} "ccc" {send "CCC\ r"}

Example:

1. Use expect to complete the ssh login process

(1) Direct execution

#! / usr/bin/expectset timeout 6 environment settings log_flie test.loglog_user setting variable definition set hostname [lindex $argv 0] set password [lindex $argv 1] # launch spawnspawn ssh root@$hostname# matching condition expect {"(yes/no)" {send "yes\ r"; exp_continue} "password" {send "$password\ r"} # permissions are transferred to console interact

(2) embedded execution

#! / bin/bashhostname=$1password=$2/usr/bin/expect

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.