PowerShell: deleting file records based on a condition

Given a file like this, where the second column is [Gender] and the third column is [Human], give me only rows which are [F](offset 20 from 0 – note it is zero and not 1) and [Human] (offset 30). Write the result to a file [HumanFemales.txt].

Dennis M Y
Jan F Y
Emma F Y
Bonzo M N


This reads the source file content into a variable, counts the records, filters the records based on the condition into an array, and writes the array to a file:

$data = Get-Content -Path C:\temp\names.txt
$filteredData = @()
$data | % {if ($_[19] -eq "F" -and $_[29] -eq "Y") { $filteredData += $_} }
$filteredData | Out-File -FilePath c:\temp\HumanFemales.txt
gc C:\temp\HumanFemales.txt



For a file of about 50,000 records on a good I7 box, the records take about 3 minutes to write to the array, uses (depending on the record length) about 1GB of memory, and takes about 5 seconds to write to disk.




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