如果条件检查变量随时间变化，则猛击 [英] Bash if condition to check variable for changes over time

问题描述

想知道是否有可能将此逻辑(检查变量是否随时间变化并在true时运行循环)转换为bash if语句或while循环条件.我希望有这样的东西:

Wondering if it's possible to finagle this logic (checking a variable for changes over time and running a loop while true) into a bash if statement or while loop condition. I was hoping for something like:

var=$(du -h *flat*.vmdk)
var2=$(sleep 1 ; du -h *flat*.vmdk)

if [[ $var != $var2 ]]; then
    while true
    do 
        echo -ne $(du -h *flat*.vmdk)\\r
        sleep 1
    done
else
    echo "Transfer complete"
fi

我也玩过while loop，而不是没有运气的if then.

I've also played with a while loop, rather than an if then with no luck.

while [ $var != $var2 ] ; do echo -ne $(du -h *flat*.vmdk)\\r ; sleep 1 ; done

但是我看到不可能吗?或者我遇到了问题，这些问题正在错误地扩展.我对任何解决方案都持开放态度，尽管我受到非常基本的Shell(ESXi Shell)的限制，其中可能不存在许多常见的unix/shell工具.

But I'm seeing that's not possible? Or I'm having issues where things are incorrectly getting expanded. I'm open to any solution, although I am limited by a very basic shell (ESXi Shell) where many common unix/shell tools may not be present.

推荐答案

您正在做while [ $var != $var2 ]，但是从不更新任何这些变量..

You are doing while [ $var != $var2 ] but never updating any of these variables ..

我会做类似的事情:

function get_size() {
    echo $(du -h *flat*.vmdk)
}

var="$(get_size)"
sleep 1
var2="$(get_size)"

while [ $var != $var2 ]; do
    var=$var2
    var2="$(get_size)"
    echo -ne "$(get_size)\\r"
    sleep 1
done

echo "Transfer complete"

它的作用:

1. 使用函数，因为当您必须在同一行中编写两次或更多次时，它会在您的大脑中触发我应该使它成为函数".
2. 在while循环中更新$var和$var2，因此您不必每次都检查相同的精确值，而是检查最后一个值与当前值之间的差异.
3. 在代码中添加换行符，因为代码是由人而不是机器读取的，人类不喜欢单行代码:)

1. Use a function, because when you have to write two times or more a same line, it should trigger a "I should make it a function" in your brain.
2. Updating $var and $var2 within the while loop, so you don't check the same exact values each time, but check diff between last value and current one.
3. Add newlines to your code, because code is done to be read by humans, not machines, humans does not likes one-liners :)

我还没有测试

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