UNIX export命令 [英] UNIX export command

问题描述

我想了解使用导出命令。

我试着用男人的出口，但该命令没有手册。

I tried using man export, but there is no manual for this command.

任何人都可以请帮我了解使用 出口UNIX的？

Can anyone please help me out understanding the use of export in UNIX?

推荐答案

当你执行一个程序的子程序继承父的环境变量。例如，如果 $ HOME 在父设置为 /根那么孩子的 $ HOME 变量也被设置为 /根。

When you execute a program the child program inherits its environment variables from the parent. For instance if $HOME is set to /root in the parent then the child's $HOME variable is also set to /root.

这仅适用于被标记为出口环境变量。如果您设置在命令行的变量像

This only applies to environment variable that are marked for export. If you set a variable at the command-line like

$ FOO="bar"

该变量不会在子进程可见。除非你将其导出：

That variable will not be visible in child processes. Not unless you export it:

$ export FOO

您可以（在老学校SH但不是）这两个语句合并成一个单一在bash：

You can combine these two statements into a single one in bash (but not in old-school sh):

$ export FOO="bar"

下面是呈现出口和非出口变量之间的区别一个简单的例子。要了解发生了什么知道 SH -c 创建一个子shell进程它继承父shell的环境。

Here's a quick example showing the difference between exported and non-exported variables. To understand what's happening know that sh -c creates a child shell process which inherits the parent shell's environment.

$ FOO=bar
$ sh -c 'echo $FOO'

$ export FOO
$ sh -c 'echo $FOO'
bar

注意：：要得到帮助的外壳内置命令使用帮助出口。 shell内置的是你的shell的一部分，而不是独立的可执行文件一样的命令 /斌/ LS 。

Note: To get help on shell built-in commands use help export. Shell built-ins are commands that are part of your shell rather than independent executables like /bin/ls.

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