SSH命令中如何同时包含本地和远程变量 [英] How have both local and remote variable inside an SSH command
问题描述
如何在ssh命令中同时包含本地和远程变量?例如下面的示例代码:
How can I have both local and remote variable in an ssh command? For example in the following sample code:
A=3;
ssh host@name "B=3; echo $A; echo $B;"
我可以访问A，但无法访问B.
I have access to A but B is not accessible.
但是在以下示例中:
A=3;
ssh host@name 'B=3; echo $A; echo $B;'
我没有A，只能访问B.
I don't have A and just B is accessible.
是否可以同时访问A和B?
Is there any way that both A and B be accessible?
推荐答案
我认为这是您想要的:
A=3;
ssh host@name "B=3; echo $A; echo \$B;"
使用双引号:
您的shell会自动对前缀为$的变量进行自动扩展，因此在您的第一个示例中，当它看到
Your shell does auto expansion on variables prefixed with $, so in your first example, when it sees
ssh host@name "B=3; echo $A; echo $B;"
bash将其扩展为:
bash expands it to:
ssh host@name "B=3; echo 3; echo ;"
和然后将host@name "B=3; echo 3; echo ;"作为参数传递给ssh.这是因为您用A=3定义了A，但从未定义过B，所以$B在本地解析为空字符串.
and then passes host@name "B=3; echo 3; echo ;" as the argument to ssh. This is because you defined A with A=3, but you never defined B, so $B resolves to the empty string locally.
使用单引号:
用单引号引起来的所有内容都被解释为字符串文字，因此当您这样做时:
Everything enclosed by single-quotes are interpreted as string-literals, so when you do:
ssh host@name 'B=3; echo $A; echo $B;'
一旦登录到远程服务器，便会执行B=3; echo $A; echo $B;指令.您已经在远程外壳程序中定义了B，但是您从未告诉过A是什么，因此$A将解析为空字符串.
the instructions B=3; echo $A; echo $B; will be run once you log in to the remote server. You've defined B in the remote shell, but you never told it what A is, so $A will resolve to the empty string.
因此，当您使用\$时，如在解决方案中一样:
So when you use \$, as in the solution:
\$意味着按字面意义解释$字符，因此我们按字面意义将echo $B发送为远程执行的指令之一，而不是先在本地进行bash扩展$B.我们最终告诉ssh要做的事情等效于此:
\$ means to interpret the $ character literally, so we send literally echo $B as one of the instructions to execute remotely, instead of having bash expand $B locally first. What we end up telling ssh to do is equivalent to this:
ssh host@name 'B=3; echo 3; echo $B;'
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