Powershell: Generate a random Alphanumeric string

psRandomAlphaNumeric.ps1

# Generate a random Alphanumeric string

Function Get-RandomAlphanumericString {
	
	[CmdletBinding()]
	Param (
        [int] $length = 8
	)

	Begin{
	}

	Process{
        Write-Output ( -join ((0x30..0x39) + ( 0x41..0x5A) + ( 0x61..0x7A) | Get-Random -Count $length  | % {[char]$_}) )
	}	
}


# Write-Host ("Alfa Beta " | Tee-Object -Variable txt) ($txt.length)

Write-Host "A: "(Get-RandomAlphanumericString | Tee-Object -variable teeTime ) ("len=$($teeTime.length)")
Write-Host "B: "(Get-RandomAlphanumericString -length 22 | Tee-Object -variable teeTime ) ("len=$($teeTime.length)")

Very helpful, thanks!

teeTime ☕ Like it!

great!

A great solution for me! Thanks

Great that you all find the code useful!

Thanks. Pretty simple and useful. But sometimes it misses the numbers,,,
Like in this output:
JbTWkLOHJrWs

Yes, the selection is randomized and the string might not contain numbers. Likewise it could be a string with only numbers, which is more likely if you generate a short string. If you need a string with more even distribution of word character and digits there are likely better ways to generate then using my function.

Thanks Marc.

I found this topic useful too:
https://stackoverflow.com/questions/37256154/powershell-password-generator-how-to-always-include-number-in-string

Any idea why there is a limit of 62 chars?

The function creates string in the intervals 0-9A-Z a-z and then sample randomize character from that string. Why Get-Random stops sampling after 62 chars I don't know, but I guess it is dependent on the string length. The function was created to generate fairly randomized short string to be included in some test files back in history. I don't think I have used it to generate any strings longer then 10 chars so I didn't know about the 62 chars limit. I don't write any things for PowerShell at this moment and don't have easy access to a Windows environment so I'm unable to dig in and find out why the 62 chars limit but If anybody knows feel free to write a comment here.

Any idea why there is a limit of 62 chars?

I think I know why:

If you need a longer string (as I needed in a project), you can just add the characters again, like this:

Here is my final function with the reference to the source, which I modified a bit
Function Generate-Password
{
<#
https://stackoverflow.com/questions/37256154/powershell-password-generator-how-to-always-include-number-in-string

.EXAMPLE
Generate-Password -Size $PassParmINIObject.Values.MinLength -CharSets ULN -Exclude ABCde123
#>
Param
(
[Int]$Size = 8,
[Char[]]$CharSets = "ULNS",
[Char[]]$Exclude,
$SpecialCharactersList # = '!"#$%&''()*+,-./:;<=>?@[]^_`{|}~' # Default if the characters list is not set in passparm.ini
)

# Debug output of Special Characters received to the function instead of the default

# Write-Host $SpecialCharactersList -ForegroundColor Red
#pause
$Chars = @(); $TokenSet = @()

If (!$TokenSets) {$Global:TokenSets = @{
    U = [Char[]]'ABCDEFGHIJKLMNOPQRSTUVWXYZ'                                #Upper case
    L = [Char[]]'abcdefghijklmnopqrstuvwxyz'                                #Lower case
    N = [Char[]]'0123456789'                                                #Numerals
    S = [Char[]]$SpecialCharactersList                                      #Symbols
}}

$CharSets | ForEach {
    
    $Tokens = $TokenSets."$_" | ForEach {If ($Exclude -cNotContains $_) {$_}}
    If ($Tokens) {
        $TokensSet += $Tokens
        If ($_ -cle [Char]"Z") {$Chars += $Tokens | Get-Random}             #Character sets defined in upper case are mandatory
    }
}

While ($Chars.Count -lt $Size) 
    {
        $Chars += $TokensSet | Get-Random

        # Debug output of random chars to be sent to the string and string length
        # Write-Host "$Chars : $($Chars.Count) ######## Output Here ######### $Size" -ForegroundColor Red
    }
($Chars | Sort-Object {Get-Random}) -Join ""                                #Mix the (mandatory) characters and output string

} # End of Function Generate-Password

Great! Thanks for improving this tread!

This is a great solution to my issue of generating a password without special characters!

The only concern I had was that characters could not be re-used, which drastically reduces the randomness of the strings it makes. So I worked out a solution that hopefully can help some other people frustrated by the GeneratePassword forced random characters.

The 62 Character limit is because the Get-Random function will not get the same character twice. When it gets, it essentially pops that item out of the array and can no longer choose it.

Here is a way around it which seems to work quite well.

$length = 72
$pwd = ""; do { $pwd = $pwd + ((0x30..0x39) + (0x41..0x5A) + (0x61..0x7A) | Get-Random | % {[char]$_}) } until ($pwd.length -eq $length)

This may or may not use every character in the array, as the array is refreshed after each letter is added.

Btw, first time posting on git. Woot!