PowerShell: How to remove columns from delimited text input? - powershell

Question

I have a text file with 5 columns of text delimited by whitespace. For example:
10 45 5 23 78
89 3 56 12 56
999 4 67 93 5
Using PowerShell, how do I remove the rightmost two columns? The resulting file should be:
10 45 5
89 3 56
999 4 67
I can extract the individual items using the -split operator. But, the items appear on different lines and I do not see how I can get them back as 3 items per line.
And to make the question more generic (and helpful to others): How to use PowerShell to remove the data at multiple columns in the range [0,n-1] given an input that has lines with delimited data of n columns each?

Answer 1

Read the file content, convert it to a csv and select just the first 3 columns:
Import-Csv .\file.txt -Header col1,col2,col3,col4,col5 -Delimiter ' ' | Select-Object col1,col2,col3
If you want just the values (without a header):
Import-Csv .\file.txt -Header col1,col2,col3,col4,col5 -Delimiter ' ' | Select-Object col1,col2,col3 | Format-Table -HideTableHeaders -AutoSize
To save back the results to the file:
(Import-Csv .\file.txt -Header col1,col2,col3,col4,col5 -Delimiter ' ') | Foreach-Object { "{0} {1} {2}" -f $_.col1,$_.col2,$_.col3} | Out-File .\file.txt
UPDATE:
Just another option:
(Get-Content .\file.txt) | Foreach-Object { $_.split()[0..2] -join ' ' } | Out-File .\file.txt

Answer 2

One way is:
gc input.txt | %{[string]::join(" ",$_.split()[0..2]) } | out-file output.txt
(replace 2 by n-1)

Answer 3

Here is the generic solution:
param
(
# Input data file
[string]$Path = 'data.txt',
# Columns to be removed, any order, dupes are allowed
[int[]]$Remove = (4, 3, 4, 3)
)
# sort indexes descending and remove dupes
$Remove = $Remove | Sort-Object -Unique -Descending
# read input lines
Get-Content $Path | .{process{
# split and add to ArrayList which allows to remove items
$list = [Collections.ArrayList]($_ -split '\s')
# remove data at the indexes (from tail to head due to descending order)
foreach($i in $Remove) {
$list.RemoveAt($i)
}
# join and output
$list -join ' '
}}