Linux环境变量引用其他变量 [英] Linux environment variables referencing other variables

问题描述

我正在使用网络供应商的引导脚本，我在RedHat 7.2上使用这个脚本。起始脚本使用几个变量来设置环境，但是我认为这些变量的设置不正确。

我已经将启动脚本添加到/ etc / environment中，我可以看到所有用户都定义了可用的变量。

这是脚本中变量定义的一个例子：

  export V1 = / opt / nameofsupplier / sdk / CentOS-RHEL-7-x86_64 
 export V2 = $ {V1} / lib / cam 
  

如果我从终端尝试这样的话，还有更多的东西：

  cd $ V1 
  

它工作正常，但是如果我尝试：

 code> cd $ V2 
  

我得到：

  base：cd $ V1 / lib / cam：没有这样的文件或目录
  

路径是有效的，如果我在shell中执行此操作：

  export V2 = $ {V1} / lib / cam 
 cd $ V2 
  

它没有任何错误，如何修复脚本？

解决方案

您可能会怀疑这些变量的不明确性。
/ etc / environment 只能包含变量定义 - 它不像普通脚本一样执行（请参阅其文档这里，其中变量扩展在/ etc / environment中不起作用。），所以在V2的定义发生。因此，V2未正确定义。


尝试在系统范围内$ 中的 / etc / environment etc / profile （或其等同，取决于用户的shell）或特定用户的〜/ .profile s。

作为最后的手段，您可以将 / etc / environment 各自的行复制到上述脚本中（但这将使维护更难）。 BR>

您还可以更正 / etc / environment 中的定义，而不是依赖扩展，即：

  export V2 = / opt / nameofsupplier / sdk / CentOS-RHEL-7-x86_64 / lib / cam 
  / pre> 
 
 
（假设没有太多的要更正）。但这也很难维护。
 
I am using a boot script from a network vendor, I am using this on RedHat 7.2  The start script sets up the environment with several variables, however I don't think these variables are set-up correctly.

I have added the start-up script to /etc/environment and I can see that the variables are defined and available to all users.

This is an example of how the variables are defined in the script:
    export V1=/opt/nameofsupplier/sdk/CentOS-RHEL-7-x86_64
    export V2=${V1}/lib/cam
There are many more, if I try this from a terminal:
    cd $V1
It works fine, however if I try:
    cd $V2
I get:
    base: cd $V1/lib/cam: No such file or directory
The path is valid, and if I do this in the shell:
    export V2=${V1}/lib/cam
    cd $V2
It works without any error, how do I fix the script?
解决方案
You may be right in suspecting an ill-definition of these variables.
/etc/environment can only contain variable definitions - it is not executed like a normal script (see its documentation here, which says Variable expansion does not work in /etc/environment.), so no variable expansion of V1 in the definition of V2 takes place. Therefore V2 is not correctly defined.


Try to source /etc/environment lines in the system-wide /etc/profile (or its equivalent, depending on the shells of your users) or in specific users' ~/.profiles.

As the last resort you can just plain copy the respective  lines of /etc/environment to the above mentioned scripts (but this will make it harder to maintain).


You could also correct the definitions in /etc/environment not to rely on expansion, i.e. like this:
export V2=/opt/nameofsupplier/sdk/CentOS-RHEL-7-x86_64/lib/cam
(assuming there are not too much of them to be corrected). But this will also be hard to maintain.

                        
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