expect命令在linux下实现批量ssh免密
<p>有时候我们需要批量发送ssh命令给服务器，但是有可能有些服务器是新加入的，还没有配置ssh免密，这个时候就会提示我们输入yes/no 或者password等，expect脚本命令就是用于在提示这些的时候，自动为我们输入相应的文字.</p>
<p>
expect脚本</p>
<p>
先看一段shell脚本，实现了ssh自动连接</p>
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<code class="xhtml plain">#!/usr/bin/expect </code>
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<code class="xhtml plain">spawn ssh 192.168.1.241</code>
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<code class="xhtml plain">expect "password"</code>
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<code class="xhtml plain">send "123456\r"</code>
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<code class="xhtml plain">expect "]#" {send "ls -la\r"}</code>
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<code class="xhtml plain">interact</code>
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<p>
注意第一行使用的是#!/usr/bin/expect而不是普通的bash脚本那样</p>
<p>
spawn就是用来启动新的进程</p>
<p>
expect “password" ,注意这个是expect脚本里面内部的命令，代表用来等待进程反馈，可以接受字符串和正则表达式，这段的意思就是将spawn启动的进程的输出当作expect命令的输入，如果包含password脚本，就会向着标准输出 输出123456\r<br>
,注意\r代表换行，跟我们输入完一个命令换行是一个道理。</p>
<p>
send:发送交互值，代替我们手动输入</p>
<p>
接着我们进入了241的服务器里面， 窗口会输出# ,跟我们的]# 匹配上了，于是向控制台输出 ls -la命令并且换行。这里我们的expect后面是带了大括号，跟上面的写在两行的效果一直。可以理解为另一种写法。</p>
<p>
interact的作用很特殊，代表等待spawn命令结束，并且停留在241服务端进行继续交互，如果没有这个，那么有可能expect对应的刚匹配上还没执行send就已经结束了。对应的我们可以使用expect eof，替代interact代表等待spawn结束后退出（在spawn进程结束后会向expect发送eof）</p>
<p>
多分支语法</p>
<p>
上面的这种expect属于单一分支模式，代表就匹配这一种，如果匹配的不是，那么就要自己输入了，但是我们有可能在第一次有不同的提示，这个时候就需要使用多分支语法</p>
<p>
expect 只要匹配到aaa 或者password其中的一种就会输出。</p>
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<code class="xhtml plain">#!/usr/bin/expect</code>
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<code class="xhtml plain">spawn ssh 192.168.1.241</code>
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<code class="xhtml plain">expect {</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">"aaa" {send "bbb\r"}</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">"password" { send "nf123456\r"}</code>
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<code class="xhtml plain">}</code>
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<code class="xhtml plain">expect "]#" {send "ls -la\r"}</code>
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<code class="xhtml plain">interact</code>
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<p>
expect命令行参数</p>
<p>
上面的expect脚本功能可能都达到了，为了避免有很多expect脚本，我更推荐使用expect命令</p>
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<code class="xhtml plain">#!/bin/bash</code>
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<code class="xhtml plain">SERVER="192.168.1.241"</code>
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<code class="xhtml plain">PASSWD=nf123456</code>
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<code class="xhtml plain">expect -c "</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">spawn ssh $SERVER;</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect {</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">\"yes/no\" { send \"yes\r\" ;exp_contine; }</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">\"password:\" { send \"$PASSWD\r\"; }</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">};</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect \"]#\" { send \"ls -la \r\" };</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect \"]#\" { send \"exit \r\" };</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect eof;</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">"</code>
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<p>
上面的shell功能和expect脚本实现的功能一致，都是通过ssh登录进去后输入，ls -la 命令</p>
<p>
set timeout -1 设置超时时间</p>
<p>
expect 后面需要加上-c</p>
<p>
expect 命令用“双引号包围起来的，这点要注意</p>
<p>
里面如果有”需要用\"转义。</p>
<p>
第15行代表ls -la 命令结束后发送一个退出命令，一般需要加上，防止阻塞</p>
<p>
expect eof 匹配spawn结束</p>
<p>
ssh批量免密demo</p>
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<code class="xhtml plain">#!/bin/bash</code>
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<code class="xhtml plain">SERVERS="192.168.1.241 192.168.1.242"</code>
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<code class="xhtml plain">PASSWD="123456"</code>
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<code class="xhtml plain">function sshcopyid</code>
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<code class="xhtml plain">{</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect -c "</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">set timeout -1;</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">spawn ssh-copy-id $1;</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect {</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">\"yes/no\" { send \"yes\r\" ;exp_contine; }</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">\"password:\" { send \"$PASSWD\r\";exp_continue; }</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">};</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">expect eof;</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">"</code>
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<code class="xhtml plain">}</code>
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<code class="xhtml plain">for server in $SERVERS</code>
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<code class="xhtml plain">do</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">sshcopyid $server</code>
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<code class="xhtml plain">done</code>
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<p>
以上就是本次介绍的expect命令在linux下实现批量ssh免密的全部过程，希望能够帮助到你。</p>
<p>
原文链接：http://www.cnblogs.com/nfcm/p/7899831.html</p>
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