在子shell中向全局变量添加值不起作用 [英] Adding value to global variable in a subshell is not working

问题描述

我正在尝试获取计算机的总磁盘使用率.下面是脚本代码:

I am trying to get the total disk usage of my machine. Below is the script code:

#!/bin/sh
totalUsage=0
diskUse(){
    df -H | grep -vE '^Filesystem|cdrom' | awk '{ print $5 " " $1 }' | while read output;
    do
       diskUsage=$(echo $output | awk '{ print $1}' | cut -d'%' -f1  )
       totalUsage=$((totalUsage+diskUsage))
    done
}
diskUse
echo $totalUsage

虽然 totalUsage 是全局变量，但我尝试将以下行中的单个磁盘使用量汇总为 totalUsage :

While totalUsage is a global variable, I have tried to sum the individual disk usage to totalUsage in the line:

totalUsage = $(((totalUsage + diskUsage))

在 do 和 done 之间的 totalUsage 回显显示正确的值，但是当我在调用 diskUse 后尝试回显它时，它仍然会打印 0

An echo of totalUsage between do and done shows the correct value, but when I try to echo it after my call diskUse, it stills prints a 0

您能帮我吗，这是怎么了?

Can you please help me, what is wrong here?

推荐答案

子外壳中的变量 totalUsage 不会更改父外壳中的值.由于标记了bash，因此可以使用此处字符串修改循环:

The variable totalUsage in a sub-shell doesn't change the value in the parent shell. Since you tagged bash, you can use here string to modify your loop:

#!/bin/bash
totalUsage=0
diskUse(){
    while read output;
    do
       diskUsage=$(echo $output | awk '{ print $1}' | cut -d'%' -f1 )
       totalUsage=$((totalUsage+diskUsage))
    done <<<"$(df -H | grep -vE '^Filesystem|cdrom' | awk '{ print $5 " " $1 }')"
}
diskUse
echo $totalUsage

这篇关于在子shell中向全局变量添加值不起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！