变量值迷失在子shell [英] Variables value gets lost in subshell

问题描述

本bash脚本并置的jar文件名到​​类路径（可变CP），while循环的值是正确的，但在子shell丢失在此相关的问题<一descibed href=\"http://stackoverflow.com/questions/124167/bash-variable-scope\">http://stackoverflow.com/questions/124167/bash-variable-scope

 ＃！/斌/庆典
CP =AAA
FUNC（）{
        LS -1 |而读JAR
        做
                如果[！ -z$ CP];然后
                        CP = $ {} CP'：'
                科幻
                CP = $ {CP} $ {} JAR
        DONE
        回声$＃CP＆LT;  - 打印AAA
}FUNC
 

我的问题是，因为我不能找出哪些元素将是最后一次，怎么能值被保存。

我是不是真的有（反复循环）的当前值保存到一个文件？

编辑：

一个同事想出了效果很好此命令序列

  LS | xargs的回声| TR''：
 

解决方案

这里的问题是，在管道中使用，而创建一个子shell和子shell不能影响它的家长。你可以解决这个问题在几个方面。对于你现在在做什么，这样就足够了：

 为JAR的*;做
    ＃ 你的东西
DONE
 

另外要注意的是，你不应该依赖解析 LS

这还显示方式，以避免子shell。

This bash script concatenates the names for jar files to a classpath (variable CP), in the while loop the value is correct but is lost in the subshell as descibed in this related question http://stackoverflow.com/questions/124167/bash-variable-scope

#!/bin/bash
CP="AAA"
func() {
        ls -1 | while read JAR
        do
                if [ ! -z "$CP" ]; then
                        CP=${CP}':'
                fi
                CP=${CP}${JAR}
        done
        echo $CP # <-- prints AAA
}

func

My question is, since I can't figure out which element will be the last one, how can the value be saved.

Do I actually have to save the current value (repeatedly in the loop) to a file?

EDIT:

A colleague came up with this command sequence which works well

ls | xargs echo|tr ' ' :

解决方案

The issue here is that using while in a pipeline creates a subshell, and a subshell cannot affect its parent. You can get around this in a few ways. For what you are doing now, this will suffice:

for JAR in *; do
    # Your stuff
done

Another thing to note is that you shouldn't rely on parsing ls

This also shows you ways to avoid the subshell.

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