Using a variable to define a hashtable name in Powershell

Question

I am reading a series of text files into hashtables so I can reference back to them in a script. The text files are well formatted to do so as name/value pairs. The text file is formatted as:

a b
c d
e f
g h

where 'a, c, e, g' are the keys and 'b,d,f,h' are the values... except there are more than 1000 lines.

For example, I have successfully named an empty hashtable after a portion of my file name with:

$FileName = 'testName' #example

$hashName = new-variable -Name $FileName -Value @{}

Ref. Stack Overflow article Calling/Setting a variable with a variable in the name

I now have an empty hashtable called testName. However, I cannot add to testName through the variable $hashName.

"$hashName".Add(1,2)

fails because [System.String] does not contain a method named 'Add'.

$hashName.Add(1,2)

fails because [System.Management.Automation.PSVariable] does not contain a method named 'Add'. (makes sense)

Note that $testName.Add(1,2) works just fine, but in this does me no good, as I'd like to loop through several variables of $testName that I extract from the multiple files that I'd like to read.

Answer 1

It's probably not the variable you want to name based on file names - you'll want to use the file names as entry keys in the hashtable instead.

You can then nest other hashtables in the first one, one for each file for example:

# Create hashtable, assign to a variable named 'fileContents'
$fileContents = @{}

# Loop through all the text files with ForEach-Object
Get-ChildItem path\to\folder -File -Filter *.txt |ForEach-Object {
    # Now we can use the file name to create entries in the hashtable
    # Let's create a (nested) hashtable to contain the key-value pairs from the file
    $fileContents[$_.Name] = @{}

    Get-Content -LiteralPath $_.FullName |ForEach-Object {
        # split line into key-value pair
        $key,$value = -split $_

        # populate nested hashtable
        $fileContents[$_.Name][$key] = $value
    }
}

$fileContents will now contain a hashtable where each entry has a file name as its key, and another hashtable containing the key-value pairs from the corresponding file as its value.

To access the contents of key c file named data.txt for example, you'd use the name and key as indices:

$fileName = 'data.txt'
$key = 'c'
$fileContents[$fileName][$key] # this will contain the string `d`, given your sample input