Using a ForEach loop to reverse csv files - powershell

Question

What I need to do is to take a number of text files (csv, all in one directory) and create files where the entire output is reversed line by line, but keeping the header at the top instead of ending up at the bottom.
I am able to take one file (by name) and copy the first line and create a new file with just that line in it. Then I take the original file minus the first line, read it into an array and reverse it. I then append that to the file that only has the header. It works fine, except for the output name, which I'd like to be [file-REV.csv] but so far I've only gotten to [file.csv-REV]...
So, once I had that working, I thought it was time to have the program find all of the csv's in the directory and loop through them, creating a reverse file for each.
This is what I have so far:
cd c:\users\$([Environment]::UserName)\working
$Path = "c:\users\$([Environment]::UserName)\working\"
ForEach ($file in Get-ChildItem -Filter *.csv) {
Get-Content $file -totalcount 1 | Set-Content .\$file-REV.csv
$flip = (get-content | select -Skip 1)
[array]::Reverse($flip)
$flip | add-content "$file-REV.csv"
}
Here is the message I receive when executing the script:
cmdlet Get-Content at command pipeline position 1
Supply values for the following parameters:
Path[0]:
I've tried to put in the entire path Get-Content -Path c:\users\jmurphy\working\ and then it complains that it can't find the entire path.

Answer 1

Couple things. First you are defining the folder to work in a variable, so use that in the Get-ChildItem. (I change the name to $Folder out of habit because $Path is already used variable in the Environment scope. Also $env: is a quicker way to read the variables out of the Environment scope.).
$Folder = "C:\Users\$env:UserName\working\"
$Files = Get-ChildItem $Folder -Filter *.csv
Second, you'll just want to use the Fullname property from what's returned from Get-ChildItem because that's the full path of each file.
ForEach ($File in $Files) {
So you'll want to use that full path to the file in your Get-Content
Get-Content $File.Fullname -totalcount 1 | Set-Content .\$($file.Basename)-REV.csv
and you'll want to use $File again as the path to the file when you call Get-Content again:
$Flip = (Get-Content $File.Fullname | Select -Skip 1)
Basename is the property from Get-Childitem with just the filename without the extension. You can force an evaluation of a property of a variable inside double quotes by enclosing in $().
$Flip | Add-Content "$($file.Basename)-REV.csv"
All together the script should look like this:
$Folder = "C:\Users\$env:UserName\working\"
$Files = Get-ChildItem $Folder -Filter *.csv
ForEach ($File in $Files) {
Get-Content $File.Fullname -totalcount 1 | Set-Content .\$($file.Basename)-REV.csv
$Flip = (Get-Content $File.Fullname | select -Skip 1)
[array]::Reverse($Flip)
$Flip | Add-Content "$($file.basename)-REV.csv"
}

Answer 2

Joe, you are doing great at learning PowerShell. You just need to harness the power of object orientation a little more.
You already know that Get-ChildItem will return an object about the file(s). What you need to know are the members included in that object. Use Get-Member to find that out.
$file = Get-ChildItem .\t.csv
$file | Get-Member
Once you find an interesting member, see what its value is.
$file.Name
$file.Extension
$file.BaseName
From this, you can construct a new file name.
$newFilename = $file.Basename + '-REV' + $file.Extension
Put this before the Get-Content line. Then use $newFilename with Add-Content.