Extract multiple columns from multiple test files in powershell - windows

Question

I got 450 files from computational model calculations for a nanosystem. Each of these files contain top three lines with Title, conditions and date/time. The fourth line has column labels (x y z t n m lag lead bus cond rema dock). From fifth line data starts upto 55th line. There are multiple spaces as delimiter. Spaces are not fixed.
I want to
I) create new text files with only x y z n m rema columns
Ii
II) I want only x y z and n values of all txt files in a single file
How to do it in powershell, plz help!

Answer 1

Based on your description, I guess the content of your files looks something like this:
Title: MyFile
Conditions: Critical
Date: 2020-02-23T11:33:02
x y z t n m lag lead bus cond rema dock
sdasd asdfafd awef wefaewf aefawef aefawrgt eyjrteujer bhtnju qerfqeg 524rwefqwert q3tgqr4fqr4 qregq5g
avftgwb ryhwtwtgqreg efqerfe rgwetgq ergqreq erwf ef 476j q4 w4th2 ef 42r13gg asdfasdrv
You can always read files like that by typing them out, line by line and only keep the lines you actually want. In your case, the data is in line 4-55 (including headers).
To get to that data, you can use this command:
Get-Content MyFile.txt | Select-Object -skip 3 -First 51
If you can confirm, that the data is the data you want, you can start working on the next issue - the multiple spaces delimiter issue.
Since (the number of) spaces are not fixed, you need to replace multiple spaces by a single space. Assuming that the values you are looking for are without spaces, you can add this to your pipeline:
Get-Content C:\MyFile.txt | Select-Object -skip 3 -First 51 | ForEach-Object {$_ -replace '( )+',' '}
The '( )+' part means one or more spaces.
Now you have proper csv data. To convert this to a proper object, you just need to convert the data from csv like this:
ConvertFrom-Csv -InputObject (Get-Content C:\MyFile.txt | Select-Object -skip 3 -First 51 | ForEach-Object {$_ -replace '( )+',' '}) -Delimiter ' '
From here it is pretty simple to select the values you want:
ConvertFrom-Csv -InputObject (Get-Content C:\MyFile.txt | Select-Object -skip 3 -First 51 | ForEach-Object {$_ -replace '( )+',' '}) -Delimiter ' ' | Select-Object x,y,z,n,m,rema
You also need to get all the files done, so you might start by getting the files like this:
foreach ($file in (Get-Content C:\MyFiles)){
ConvertFrom-Csv -InputObject (Get-Content $file.fullname | Select-Object -skip 3 -First 51 | ForEach-Object {$_ -replace '( )+',' '}) -Delimiter ' ' | Select-Object x,y,z,n,m,rema
}
You might want to split up the code into a more read-able format, but this should pretty much cover it.