linux shell全局变量在另一个窗口终端中不可用 [英] linux shell global variable does not available in another window terminal

问题描述

我在Linux操作系统中打开两个终端窗口. 在一个窗口中，键入命令

export a=10

但是在另一个窗口中，我输入

echo $a

它什么也不输出，所以为什么它不起作用.预先感谢.

解决方案

导出环境变量时，shell的子进程(例如:shell执行的命令)会获取该导出变量的副本. /p>

在两个不同的终端/窗口中运行的Shell就进程而言并不满足这种关系.

如果要设置环境变量，以便每个运行中的shell都可以获取自己的变量实例，请考虑在.bashrc中定义它(假设您正在使用bash).但是，您将无法将该变量作为所有正在运行的shell的共享对象"使用(每个shell都有其自己的变量副本).

I open tow terminal windows in my linux OS. In one window, I type the command

export a=10

but in another window, I enter

echo $a

it output nothing, so why it does not work. thanks in advance.

解决方案

When you export an environmental variable, the child processes of the shell (e.g.: the commands executed by the shell) do obtain a copy of that exported variable.

Shells running in two different terminals/windows do not fulfill this relationship in terms of processes.

If you want to set an environmental variable, so that every running shell will obtain a its own instance of the variable, consider defining it in .bashrc (assuming you are using bash). However, you won't be able to use this variable as a one "being shared" by all the running shells (each shell has its own copy of the variable).

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