在while循环外无法读取在while循环内存储的变量 [英] Can't read variable that was stored from within a while loop, when out of the while loop

问题描述

我一生都无法理解为什么我无法在 while 循环之外读取 postPrioity.我试过 "export postPrioity="500"" 还是不行.

I can't for the life of me see why I can not read the postPrioity outside the while loop. I tried "export postPrioity="500"" still didn't work.

有什么想法吗?

-- 或在计划文本中 --

-- or in plan text --

#!/bin/bash
cat "/files.txt" | while read namesInFile; do   
            postPrioity="500"
            #This one shows the "$postPrioity" varible, as '500'
            echo "weeeeeeeeee ---> $postPrioity <--- 1"
done
            #This one comes up with "" as the $postPrioity varible. GRRR
            echo "weeeeeeeeee ---> $postPrioity <--- 2"

输出:(我在files.txt中只有3个文件名)

OUTPUT: (I only have 3 file names in files.txt)

weeeeeeeeee ---> 500 <--- 1
weeeeeeeeee ---> 500 <--- 1
weeeeeeeeee ---> 500 <--- 1
weeeeeeeeee --->  <--- 2

推荐答案

管道操作符创建子shell，参见BashPitfalls 和 BashFAQ.解决办法:不要用cat，反正也没用.

The pipe operator creates a subshell, see BashPitfalls and BashFAQ. Solution: Don't use cat, it's useless anyway.

#!/bin/bash
postPriority=0
while read namesInFile
do   
    postPrioity=500
    echo "weeeeeeeeee ---> $postPrioity <--- 1"
done < /files.txt
echo "weeeeeeeeee ---> $postPrioity <--- 2"

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