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expect是一种能够按照脚本内容里面设定的方式与交互式程序进行“会话”的程序。根据脚本内容，Expect可以知道程序会提示或反馈什么内容以及 什么是正确的应答。它是一种可以提供“分支和嵌套结构”来引导程序流程的解释型脚本语言。

shell功能很强大,但是不能实现有交互功能的多机器之前的操作,例如ssh和ftp.而expect可以帮助我们来实现.

一,安装expect

yum install expect

其实expect根bash形势上差不多的.

二,实例

1,ssh实现自动登录,并停在登录服务器上

#!/usr/bin/expect -f
 set ip [lindex $argv 0 ]     //接收第一个参数,并设置IP
 set password [lindex $argv 1 ]   //接收第二个参数,并设置密码
 set timeout 10                   //设置超时时间
 spawn ssh root@$ip       //发送ssh请滶
 expect {                 //返回信息匹配
 "*yes/no" { send "yes\r"; exp_continue}  //第一次SSH连接会提示yes/no,继续
 "*password:" { send "$password\r" }      //出现密码提示,发送密码
 }
 interact          //交互模式,用户会停留在远程服务器上面.

运行结果如下:

root@Ubuntu:/home/zhangy# ./test.exp 192.168.1.130 admin
spawn SSH root@192.168.1.130
Last login: Fri Sep  7 10:47:43 2012 from 192.168.1.142
[root@linux ~]#

这个例子有统一的接口,根据IP和密码可以连接到不同的机器.如果你嫌输入IP和密码麻烦,看下面的例子

#!/usr/bin/expect -f
 set ip 192.168.1.130
 set password admin
 set timeout 10
 spawn SSH root@$ip
 expect {
 "*yes/no" { send "yes\r"; exp_continue}
 "*password:" { send "$password\r" }
 }
 interact

运行结果如下:

root@Ubuntu:/home/zhangy# ./web.exp
spawn SSH root@192.168.1.130
Last login: Fri Sep  7 12:59:02 2012 from 192.168.1.142
[root@linux ~]#

2,ssh远程登录到服务器,并且执行命令,执行完后并退出

#!/usr/bin/expect -f
 set ip 192.168.1.130
 set password admin
 set timeout 10
 spawn ssh root@$ip
 expect {
 "*yes/no" { send "yes\r"; exp_continue}
 "*password:" { send "$password\r" }
 }
 expect "#*"
 send "pwd\r"
 send  "exit\r"
 expect eof

运行结果如下:

root@Ubuntu:/home/zhangy# ./test3.exp
spawn ssh root@192.168.1.130
root@192.168.1.130's password:
Last login: Fri Sep  7 14:05:07 2012 from 116.246.27.90
[root@localhost ~]# pwd
/root
[root@localhost ~]# exit
logout
Connection to 192.168.1.130 closed.

3,远程登录到ftp,并且下载文件

#!/usr/bin/expect -f
 set ip [lindex $argv 0 ]
 set dir [lindex $argv 1 ]
 set file [lindex $argv 2 ]
 set timeout 10
 spawn ftp $ip
 expect "Name*"
 send "zwh\r"
 expect "Password:*"
 send "zwh\r"
 expect "ftp>*"
 send "lcd $dir\r"
 expect {
 "*file"  { send_user "local $_dir No such file or directory";send "quit\r" }
 "*now*"  { send "get $dir/$file $dir/$file\r"}
 }
 expect {
 "*Failed" { send_user "remote $file No such file";send "quit\r" }
 "*OK"     { send_user "$file has been download\r";send "quit\r"}
 }
 expect eof

运行结果如下:

root@Ubuntu:/home/zhangy# ./test2.exp 192.168.1.130 /var/www/www aaa.html
spawn ftp 192.168.1.130
Connected to 192.168.1.130.
220 (vsftpd 2.0.5)
Name (192.168.1.130:root): zwh
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> lcd /var/www/www
Local directory now /var/www/www
ftp> get /var/www/www/aaa.html /var/www/www/aaa.html
local: /var/www/www/aaa.html remote: /var/www/www/aaa.html
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for /var/www/www/aaa.html (66 bytes).
226 File send OK.
66 bytes received in 0.00 secs (515.6 kB/s)
quit aaa.html has been download
221 Goodbye.