打印经过时间的秒三的尾部位数 [英] Print elapsed time in secs with three trailing digits

问题描述

有关框架我写，我想衡量一块（bash）的code多少需要执行，然后打印所用的时间以秒为单位。

For a framework I'm writing I would like to measure how much a piece of (bash) code takes to execute and then print the elapsed time in seconds.

有关测量，我做到以下几点：

For measuring, I do the following:

start=$(date +%s%N)

# do something here

elapsed_time=$(($(date +%s%N) - start))

这给了我经过毫微秒串接经过秒。如果我现在乘以1000000把这个，我会在毫秒时间

This gives me the elapsed seconds concatenated with the elapsed nanos. If I now divide this by 1000000, I'll get the time in ms

elapsed_time_in_ms=$(($elapsed time / 1000000))

这是所有好的，似乎工作，但真正的问题是，我想打印格式为：

This is all nice and seems to work but the real problem is that I want to print it in this format:

12.789s

，其中前。是秒，小数点后是毫秒值的最后3位数字。

where before the . are the seconds and after the dot are last 3 digits of the ms value.

我将如何实现这样的事情？

How would I achieve something like that?

修改

我知道时间很可能没有多大用处的，我还是想实现这个（即使只是化妆品的原因： - ）。）

I am aware that the time would probably not of much use, still I would like to implement this (even if only for cosmetic reasons :-)).

编辑2

对于任何人面临同样的问题：

For anyone facing the same problem:

在最后，我选择了使用时间，因为它不需要叉，似乎是最便携的解决方案。

In the end I've chosen to use time as it doesn't require a fork and seems to be the most portable solution.

有一个看是函数和全局 total_elapsed_time 变量的此处看到我是如何实现这一点。

Have a look at the it function and the global total_elapsed_time variable here to see how I implemented this.

推荐答案

您可以使用 BC 命令：

elapsed_time_in_ms=$(echo "scale=3;$elapsed_time/1000000" | bc)

的比例基本设置后，你想要的位数的。

The scale basically sets the number of digits you want after the .

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