子外壳程序进程无法访问父外壳程序中定义的变量和函数 [英] Sub-shell process not be able to access variables and functions defined in parent shell

问题描述

我在同一目录中有3个脚本，请在下面找到x.sh，y.sh和z.sh的内容:-

I have 3 scripts in the same directory, please find below contents of x.sh, y.sh and z.sh :-

x.sh:-

xData="DataOfX"

function xInit(){
    echo "xInit : data of a >$xData<"
}

y.sh:-

. x.sh

xInit

sh z.sh zInit

z.sh:-

function zInit(){
    echo "zInit of z"
    xInit
}

$@

执行

. y.sh

. y.sh

同一目录中的

给出以下输出:-

in the same directory gives below output :-

xInit : data of a >DataOfX<
zInit of z
z.sh: line 3: xInit: command not found

子shell进程如何访问在父shell中初始化的变量和函数?

How can a sub-shell process can access the variables and functions initialised in the parent shell?

推荐答案

术语"sub-shell"是有问题的，甚至man bash的使用方式也不一致.严格来说，子shell是另一个shell环境，它继承了父级的所有功能，包括所有变量.

The term "sub-shell" is problematic, and even man bash is inconsistent in the way it is used. Strictly speaking a sub-shell is another shell environment which inherits all features, including all variables, of the parent.

括号给一个子壳.变量BASH_SUBSHELL给出子外壳的 level ，而$$给出外壳的PID(在子外壳中，它被伪造为父对象的PID).

Parentheses gives a subshell. The variable BASH_SUBSHELL gives the level of subshell, and $$ gives the PID of the shell (in subshells it is faked to be the PID of the parent).

$ x=42

$ echo $BASH_SUBSHELL, $x, $$
0, 42, 1130
$ (echo $BASH_SUBSHELL, $x, $$)
1, 42, 1130
$ ( (echo $BASH_SUBSHELL, $x, $$) )
2, 42, 1130

执行脚本时，不是子shell .用以下脚本获取gash.sh脚本:

When you execute a script, that is not a subshell. Take a script gash.sh with:

echo $BASH_SUBSHELL, $x, $$

将其运行为:

$ ./gash.sh
0, , 8419

请注意空白，因为未复制x.它不是子shell，并且PID不同.甚至

Notice the blank because x is not copied. It is not a subshell, and the PID is different. Even

$ (./gash.sh)
1, , 8421

这是一个运行子进程的子外壳，因此也不起作用.

that is a subshell running a child process, so that doesn't work either.

您需要将变量移动到 environment块，使用export将其复制到子进程中:

You need to move the variable to the environment block, which is copied to child processes, using export:

$ export x
$ ./gash.sh
0, 42, 8423

未导出的变量仅在使用( )的子外壳中可用，而在其他子进程中则不可用.对于功能，请使用export -f.

Variables that are not exported are only available in subshells using ( ), not other child processes. For functions use export -f.

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