替换现有文件中浮点数的精度 [英] Replacing precision of floating point numbers in existing file

问题描述

我有许多以下格式的大文件

I have a large number of big files in the following format

step 80
1.10045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
1.10045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
1.10045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
1.10045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
step 90
1.54045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
1.16545e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
1.10045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
1.10045e+07 1.10125e+07 1.20345e+07 2.40225e+07 4.30245e+07
...

数字都是不同的(由于我的懒惰，这里有些数字相同).

The numbers are all distinct (some are the same here because of my laziness).

我想更改浮点数的精度.也就是说，我想将以前的文件替换为:

I want to to change the precision of the floating-point numbers. That is, I want to replace the previous file with:

step 80
1.10e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
1.10e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
1.10e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
1.10e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
step 90
1.54e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
1.16e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
1.10e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
1.10e+07    1.10e+07    1.20e+07 2.40e+07   4.30e+07
...

如果所需的精度是小数点后2位.

if the desired precision is 2 digits after the decimal point.

如何以一种高效的方式做到这一点，并且内存使用率低(也就是说，我不必将整个文件加载到内存中).

How can I do this, in an efficient way, and low memory usage (that is, I don't to have to load the complete file to memory).

最好是使用bash脚本的解决方案.

Preferably a solution using a bash script.

推荐答案

您可以使用Perl逐行读取文件，并使用

You could use Perl to read the file line-by-line and reformat the numbers with sprintf():

perl -pe '!/^step/ && s/(\S+)/sprintf("%.2e", $1)/ge' file

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