PowerShell: how to count number of rows in csv file?

Get-Content and Measure-Object are fine for small files, but both are super inefficient with memory. I had real problems with large files.

When counting rows in a 1GB file using either method, Powershell gobbled up all available memory on the server (8GB), then started paging to disk. I left it over an hour, but it was still paging to disk so I killed it.

The best method I found for large files is to use IO.StreamReader to load the file from disk and count each row using a variable. This keeps memory usage down to a very reasonable 25MB and is much, much quicker, taking around 30 seconds to count rows in a 1GB file or a couple of minutes for a 6GB file. It never eats up unreasonable amounts of RAM, no matter how large your file is:

[int]$LinesInFile = 0$reader = New-Object IO.StreamReader 'c:\filename.csv' while($reader.ReadLine() -ne $null){ $LinesInFile++ }

The above snippet can be inserted wherever you would use get-content or measure-object, simply refer to the $LinesInFile variable to get the row count of the file.

Pipe it to the Measure-Object cmdlet

Import-Csv C:\Directory\file.csv | Measure-Object

Generally (csv or not)

@(Get-Content c:\file.csv).Length

If the file has only one line, then, it will fail. (You need the @ prefix...otherwise if the file has one line, it will only count the number of characters in that line.

Get-Content c:\file.csv | Measure-Object -line

But both will fail if any record takes more than one row. Then better import csv and measure:

Import-Csv c:\file.csv | Measure-Object | Select-Object -expand count