Powershell - Using ConvertFrom-csv

Question

I'm brand new to Powershell. I have a variable that contains comma separated values. What I want to do is read each entry in the csv string variable, and assign it to a variable. I am using ConvertFrom-csv to separate the data with headers.

How can I assign each value to a variable, or even better, use ConvertTo-csv to create a new csv string which only has, for example, columns 2/3/6/7 in it?

I would ultimately want to write that data out to a new csv file.

Here is my test code:

#Setup the variable
$Data = "test1,test2,test3,1234,5678,1/1/2021,12/31/2021" 
 
$Data | ConvertFrom-csv -Header Header1,Header2, Header3, Header4, Header5, Header6, Header7
 
# Verify that an object has been created.
$Data | 
    ConvertFrom-csv -Header Header1,Header2, Header3, Header4, Header5, Header6, Header7 |
    Get-Member


#Show header1
    Write-Host "--------Value from $Data----------------------------------------"
    $Data[0]   #doesn't work, only displays the first character of the string
    Write-Host "-----------------------------------------------------------------"

Walter Mitty · Accepted Answer · 2021-11-05 11:40:29Z

Let me suggest a different approach. If you use ConvertFrom-Csv and assign the result of a variable ($data), this will be an array of Custom Objects. You can run this through a loop that steps through the elements of the array , one at a time, and then through an inner loop that steps through the properties of each object one at a time, setting a variable with the same name as the field header and the same value as the current record's value.

I don't have code that does exactly what you want. But I'm including code that I wrote a few years back that does something similar only using Import-Csv instead of ConverFrom-Csv.

   Import-Csv $driver | % {
       $_.psobject.properties | % {Set-variable -name $_.name -value $_.value}
       Get-Content $template | % {$ExecutionContext.InvokeCommand.ExpandString($_)} 
   }

Focus on the first inner loop. Each property of the current object will have a name that came from the header and a value that came from the current record of the Csv file. You can ignore the line that says ExpandString. That's just what I choose to do with the variables once they have been defined.

Santiago Squarzon · Accepted Answer · 2021-11-05 05:00:10Z

1

How can I assign each value to a variable, or even better, use ConvertTo-Csv to create a new csv string which only has, for example, columns 2/3/6/7 in it?

This is one way of automating this:

# Define the CSV without headers
$Data = "test1,test2,test3,1234,5678,1/1/2021,12/31/2021"

# Set the number of headers needed
$headers = $Data.Split(',') | ForEach-Object -Begin { $i = 1 } -Process {
    "Header$i"; $i++
}

# Set the desired columns we want
$desiredColumns = 2,3,6,7 | ForEach-Object { $_ - 1 } | ForEach-Object {
    $headers[$_]
}

# Convert to CSV and filter by Desired Columns
$Data | ConvertFrom-Csv -Header $headers | Select-Object $desiredColumns

Result

Header2 Header3 Header6  Header7   
------- ------- -------  -------   
test2   test3   1/1/2021 12/31/2021

Result as CSV

$Data | ConvertFrom-Csv -Header $headers |
Select-Object $desiredColumns | ConvertTo-Csv -NoTypeInformation

"Header2","Header3","Header6","Header7"
"test2","test3","1/1/2021","12/31/2021"

edited Nov 5, 2021 at 5:00

answered Nov 5, 2021 at 4:52

Santiago Squarzon

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3 Comments

HurricaneCoffee Over a year ago

Thanks Santiago! That works great. One more question, is there any way to remove the quotation marks from the data being written to the new csv string?

Theo Over a year ago

@HurricaneCoffee ConvertTo-CsvNoQuotes

HurricaneCoffee Over a year ago

Thanks Theo! That's super helpful.

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