Import single line from text file into json file

I have a really simple question which I am sure someone can answer really quickly for me.

I have one text file (password.txt) containing a random string of characters which has been generated by a Poweshell script to be used as a wifi password.

I have another script (change-password.ps1) which logs into my router and changes the password. I have managed to get this script to look at a json file (config.json) and use one of static passphrases.

This is my json file

{ "PSKs": {
            "01":"PSKforJanuary123!!",
            "02":"PSKforFebruary123!",
            "03":"PSKforMarch123!",
            "04":"PSKforApril123!",
            "05":"PSKforMay123!",
            "06":"PSKforJune123!",
            "07":"PSKforJuly123!",
            "08":"PSKforAugust123!",
            "09":"PSKforSeptember123!",
            "10":"PSKforOctober123!",
            "11":"PSKforNovember123!",
            "12":"PSKforDecember123!"
        }
    }

So instead of using one of these from the list above, how can I replace the "PSKfor***123!" with the line of text from my password.txt?

Or is there a way I can create this random string of characters within my json file without having to run another script to generate it?

Thanks in advance!

Solution

How to update all properties in the Json using a password stored in a file:

$json = Get-Content path\to\json.txt -Raw | ConvertFrom-Json
$pass = Get-Content path\to\password.txt
$json.PSKs.PSObject.Properties | ForEach-Object { $_.Value = $pass }
$json | ConvertTo-Json | Set-Content path\to\json.txt

How to update a single property in the Json using a password stored in a file, say for example, to dynamically update the property that corresponds with the current month:

$json = Get-Content path\to\json.txt -Raw | ConvertFrom-Json
$pass = Get-Content path\to\password.txt
$month = [datetime]::Now.ToString('MM')
# `$json.PSKs.$month` would work too here
$json.PSKs.PSObject.Properties[$month].Value = $pass
$json | ConvertTo-Json | Set-Content path\to\json.txt

How to update all properties using a randomly generated password, for this you will need to figure out what logic you want to use to generate a random password. A very easy way is via RandomNumberGenerator.GetString(ReadOnlySpan<Char>, Int32) Method but this method only works in PowerShell 7.

# `$chars` can be whatever you like, this is just an example
$chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!@#$%&_-+='.ToCharArray()
$json = Get-Content path\to\json.txt -Raw | ConvertFrom-Json
$json.PSKs.PSObject.Properties | ForEach-Object {
    # `20` is for the string length
    $_.Value = [System.Security.Cryptography.RandomNumberGenerator]::GetString($chars, 20)
}
$json | ConvertTo-Json | Set-Content path\to\json.txt