Powershell - Variable problems - powershell

Question

I wrote a script that will pull data from a .properties file (basically a config file). Some of the data from the properties file has environment data (i.e. %UserProfile%), so I run it through a function (Resolve–EnvVariable) that will replace the environment variable with the actual value. The replace works perfectly, but somehow the data seems to be altered.
When I try to use the values that have been run through the function, they no longer work (see results down below).
This is the file contents of c:\work\test.properties
types="*.txt"
in="%UserProfile%\Downloads"
This is my PowerShell Script
Clear-Host
#Read the properties file and replace the parameters when specified
if (Test-Path C:\work\test.properties) {
$propertiesFile = Get-Content C:\work\test.properties
Write-Host "Parameters will be substituded from properties file" -ForegroundColor Yellow
foreach ($line in $propertiesFile) {
Write-Host ("from Properties file $line")
$propSwitch = $line.Split("=")[0]
$propValue = Resolve–EnvVariable($line.Split("=")[1])
switch ($propSwitch) {
"types" { $types = $propValue }
"in" { $in = $propValue }
}
}
}
write-host ("After running through function `n in=" + $in + "<- types=" + $types + "<-")
# This function resolves environment variables
Function Resolve–EnvVariable {
[cmdletbinding()]
Param(
[Parameter(Position = 0, ValueFromPipeline = $True, Mandatory = $True,
HelpMessage = "Enter string with env variable i.e. %APPDATA%")]
[ValidateNotNullOrEmpty()]
[string]$String
)
Begin {
Write-Verbose "Starting $($myinvocation.mycommand)"
} #Begin
Process {
#if string contains a % then process it
if ($string -match "%\S+%") {
Write-Verbose "Resolving environmental variables in $String"
#split string into an array of values
$values = $string.split("%") | Where-Object { $_ }
foreach ($text in $values) {
#find the corresponding value in ENV:
Write-Verbose "Looking for $text"
[string]$replace = (Get-Item env:$text -erroraction "SilentlyContinue").Value
if ($replace) {
#if found append it to the new string
Write-Verbose "Found $replace"
$newstring += $replace
}
else {
#otherwise append the original text
$newstring += $text
}
} #foreach value
Write-Verbose "Writing revised string to the pipeline"
#write the string back to the pipeline
Write-Output $NewString
} #if
else {
#skip the string and write it back to the pipeline
Write-Output $String
}
} #Process
End {
Write-Verbose "Ending $($myinvocation.mycommand)"
} #End
} #end Resolve-EnvVariable
# Hardcoded values work
$test1 = Get-ChildItem -Path "C:\Users\Paul\Downloads" -Recurse -Include "*.txt"
# Values pulled and updated through function do not work
$test2 = Get-ChildItem -Path $in -Recurse -Include $types
# If I manually assign the values, it works
$in = "C:\Users\Paul\Downloads"
$types = "*.txt"
$test3 = Get-ChildItem -Path $in -Recurse -Include $types
foreach ($test in $test1) { write-host "test1 $test" }
foreach ($test in $test2) { write-host "test2 $test" }
foreach ($test in $test3) { write-host "test3 $test" }
Results
Parameters will be substituded from properties file
from Properties file types="*.txt"
from Properties file in="%UserProfile%\Downloads"
After running through function
in="C:\Users\Paul\Downloads"<- types="*.txt"<-
test1 C:\Users\Paul\Downloads\Test\testPaul.txt
test1 C:\Users\Paul\Downloads\Test2\File1.txt
test3 C:\Users\Paul\Downloads\Test\testPaul.txt
test3 C:\Users\Paul\Downloads\Test2\File1.txt

Answer 1

Two alternatives:
1. Use Environment.ExpandEnvironmentVariables()
If you switched to non-qualified string values and escaped your \, it would be as simple as piping the file to ConvertFrom-StringData, at which point you could expand the variable values with Environment.ExpandEnvironmentVariables():
Properties file:
types=*.txt
in=%UserProfile%\\Downloads
Script:
# Convert file to hashtable
$properties = Get-Content file.properties -Raw |ConvertFrom-StringData
# Copy value to new hashtable, but expand env vars first
$expanded = #{}
foreach($entry in $properties.GetEnumerator()){
$expanded[$entry.Key] = [Environment]::ExpandEnvironmentVariables($entry.Value)
}
Should give you the desired values:
PS C:\> $expanded
Name Value
---- -----
in C:\Users\username\Downloads
types *.txt
2. Use and dot-source a PowerShell script for your properties
This is lifted straight out of a page of the original Exchange Server modules - place all configuration variables in separate scripts, which are in turn dot-sourced when initializing a new session:
Properties file:
$types = "*.txt"
$in = Join-Path $env:USERPROFILE Downloads
Script:
# dot source the variables
. (Join-Path $PSScriptRoot properties.ps1)
# do the actual work
Get-ChildItem $in -Include $types