I'm learning PowerShell and trying to set variable values inside a loop. Using these strings:
$Apple = 'Apple'
$Banana = 'Banana'
$Orange = 'Orange'
I'm trying to join the strings inside a loop:
$Fruits = #($Apple, $Banana, $Orange)
foreach ($Fruit in $Fruits)
{
$Fruit = $Fruit + '.' + "Test"
$Fruit
}
This works inside the scope of the loop. But how can I set the value of $Apple, $Banana and $Orange permanently?
You could use a combination of Get-Variable and Set-Variable. Bear in mind the array contains the variable names, not their values.
$Apple = 'Apple'
$Banana = 'Banana'
$Orange = 'Orange'
$FruitVariables = #('Apple','Banana','Orange')
foreach ($Fruit in $FruitVariables)
{
Set-Variable -Name $Fruit -Value ((Get-Variable -Name $Fruit).Value + ".Test")
}
If you're only interested in setting the values in the array, you could use index:
$Fruits = #($Apple, $Banana, $Orange)
foreach ($i in 0..($Fruits.Count - 1))
{
$Fruits[$i] = $Fruits[$i] + '.' + "Test"
$Fruits[$i]
}
I feel like there may be a more elegant solution using [ref], but the above is what's in the scope of my knowledge.
Related
Ok I guess this question has already been answered somewhere but I do not find it. So here is my few lines of codes
$a = 0
$b = 0
$c = 0
$array = #($a, $b, $c)
foreach ($var in $array) {
$var = 3
}
Write-Host "$a : $b : $c"
What I try to do is loop into $array and modify a, b and c variables to get 3 : 3 : 3 ... I find something about [ref] but I am not sure I understood how to use it.
You'll need to wrap the values in objects of a reference type (eg. a PSObject) and then assign to a property on said object:
$a = [pscustomobject]#{ Value = 0 }
$b = [pscustomobject]#{ Value = 0 }
$c = [pscustomobject]#{ Value = 0 }
$array = #($a, $b, $c)
foreach ($var in $array) {
$var.Value = 3
}
Write-Host "$($a.Value) : $($b.Value) : $($c.Value)"
Since $a and $array[0] now both contain a reference to the same object, updates to properties on either will be reflected when accessed through the other
As you mentioned you can use the [ref] keyword, it will create an object with a "Value" property and that's what you have to manipulate to set the original variables.
$a = 1
$b = 2
$c = 3
$array = #(
([ref] $a),
([ref] $b),
([ref] $c)
)
foreach ($item in $array)
{
$item.Value = 3
}
Write-Host "a: $a, b: $b, c: $c" # a: 3, b: 3, c: 3
You could also use the function Get-Variable to get variables:
$varA = Get-Variable -Name a
This way you can get more information about the variable like the name.
And if your variables have some kind of prefix you could get them all using a wildcard.
$variables = Get-Variable -Name my*
And you would get all variables that start with "my".
This question already has answers here:
Powershell create array of arrays
(3 answers)
Closed 5 years ago.
This is building $ret into a long 1 dimensional array rather than an array of arrays. I need it to be an array that is populated with $subret objects. Thanks.
$ret = #()
foreach ($item in $items){
$subret = #()
$subRet = $item.Name , $item.Value
$ret += $subret
}
there might be other ways but arraylist normally works for me, in this case I would do:
$ret = New-Object System.Collections.ArrayList
and then
$ret.add($subret)
The suspected preexisting duplicate question is indeed a duplicate:
Given that + with an array as the LHS concatenates arrays, you must nest the RHS with the unary form of , (the array-construction operator) if it is an array that should be added as a single element:
# Sample input
$items = [pscustomobject] #{ Name = 'n1'; Value = 'v1'},
[pscustomobject] #{ Name = 'n2'; Value = 'v2'}
$ret = #() # create an empty *array*
foreach ($item in $items) {
$subret = $item.Name, $item.Value # use of "," implicitly creates an array
$ret += , $subret # unary "," creates a 1-item array
}
# Show result
$ret.Count; '---'; $ret[0]; '---'; $ret[1]
This yields:
2
---
n1
v1
---
n2
v2
The reason the use of [System.Collections.ArrayList] with its .Add() method worked too - a method that is generally preferable when building large arrays - is that .Add() only accepts a single object as the item to add, irrespective of whether that object is a scalar or an array:
# Sample input
$items = [pscustomobject] #{ Name = 'n1'; Value = 'v1'},
[pscustomobject] #{ Name = 'n2'; Value = 'v2'}
$ret = New-Object System.Collections.ArrayList # create an *array list*
foreach ($item in $items) {
$subret = $item.Name, $item.Value
# .Add() appends whatever object you pass it - even an array - as a *single* element.
# Note the need for $null = to suppress output of .Add()'s return value.
$null = $ret.Add($subret)
}
# Produce sample output
$ret.Count; '---'; $ret[0]; '---'; $ret[1]
The output is the same as above.
Edit
It is more convoluted to create an array of tuples than fill an array with PsObjects containing Name Value as the two properties.
Select the properties you want from $item then add them to the array
$item = $item | select Name, Value
$arr = #()
$arr += $item
You can reference the values in this array by doing this
foreach($obj in $arr)
{
$name = $obj.Name
$value = $obj.Value
# Do actions with the values
}
I am new to powershell scripts and not sure how to achieve the below:
$finalArray = #()
$tempArray0 = 'A'
$tempArray1 = 'B'
$tempArray2 = 'C'
FOR (i=0; i -eq 5; i++) {$finalArray += $tempArray[i]}
$finalArray
Output Should be:
A
B
C
If the variable name is itself variable, you'll have to use the Get-Variable cmdlet to retrieve its value:
$finalArray = #()
$tempArray0 = 'A'
$tempArray1 = 'B'
$tempArray2 = 'C'
for($i=0; $i -le 2; $i++) {
$finalArray += (Get-Variable "temparray$i" -ValueOnly)
}
$finalArray
If you want to create variables with variable names, use the New-Variable cmdlet:
$Values = 'A','B','C'
for($i = 0; $i -lt $Values.Count; $i++){
New-Variable -Name "tempvalue$i" -Value $Values[$i]
}
which would result in:
PS C:\> $tempvalue1
B
Although the above will solve the example you've presented, I can think of very few cases where you wouldn't be better of using a [hashtable] instead of variable variable names - they're usually an over-complication, and you'll end up with unnecessary code anyways because you need to calculate the variable names at least twice (during creation and again when reading the value).
From the comments, it sounds like you're trying to generate input for a password generator. This can be simplified grossly, without resorting to variable variable names:
# Create a hashtable and generate the characters
$CharArrays = #{
Letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray()
Numbers = 0..9
}
# Generate some letters for the password
$PasswordChars = $CharArrays['Letters'] |Get-Random -Count 10
# Generate a few digits
$PasswordChars += $CharArrays['Numbers'] |Get-Random -Count 4
# Shuffle them around a bit
$PasswordChars = $PasswordChars |Sort-Object {Get-Random}
# Create your password
$Password = $PasswordChars -join ''
Say I have 2 powershell hashtables one big and one small and, for a specific purpose I want to say they are equal if for the keys in the small one, the keys on the big hastable are the same.
Also I don't know the names of the keys in advance. I can use the following function that uses Invoke-Expression but I am looking for nicer solutions, that don't rely on this.
Function Compare-Subset {
Param(
[hashtable] $big,
[hashtable] $small
)
$keys = $small.keys
Foreach($k in $keys) {
$expression = '$val = $big.' + "$k" + ' -eq ' + '$small.' + "$k"
Invoke-Expression $expression
If(-not $val) {return $False}
}
return $True
}
$big = #{name='Jon'; car='Honda'; age='30'}
$small = #{name = 'Jon'; car='Honda'}
Compare-Subset $big $small
A simple $true/$false can easily be gotten. This will return $true if there are no differences:
[string]::IsNullOrWhiteSpace($($small|Select -Expand Keys|Where{$Small[$_] -ne $big[$_]}))
It checks for all keys in $small to see if the value of that key in $small is the same of the value for that key in $big. It will only output any values that are different. It's wrapped in a IsNullOrWhitespace() method from the [String] type, so if any differences are found it returns false. If you want to list differences just remove that method.
This could be the start of something. Not sure what output you are looking for but this will output the differences between the two groups. Using the same sample data that you provided:
$results = Compare-Object ($big.GetEnumerator() | % { $_.Name }) ($small.GetEnumerator() | % { $_.Name })
$results | ForEach-Object{
$key = $_.InputObject
Switch($_.SideIndicator){
"<="{"Only reference object has the key: '$key'"}
"=>"{"Only difference object has the key: '$key'"}
}
}
In primetime you would want something different but just to show you the above would yield the following output:
Only reference object has the key: 'age'
What I'm trying to do is create array variable names dynamically, and then with a loop, add the object to its relevant array based on the hash table value being equal to the counter variable.
$hshSite = #{} # Values like this CO,1 NE,2 IA,3
$counter = $hshSite.count
For($i = $counter; $i -gt 0; $i--) {
New-Variable -Name "arr$i" -Value #()
}
If $counter = 3, I would create arrays $arr1, $arr2, $arr3
$csv = Import-CSV....
ForEach ($x in $csv) {
#if $hshSite.Name = $x.location (ie CO), look up hash value (1),
and add the object to $arr1. If $hshSite.Name = NE, add to $arr2
I tried creating the dynamic arrays with New-Variable, but having issues trying to add to those arrays. Is it possible to concatenate 2 variables names into a single variable name? So taking $arr + $i to form $arr1 and $arr2 and $arr3, and then I can essentially just do $arr0 += $_
The end goal is to group things based on CO, NE, IA for further sorting/grouping/processing. And I'm open to other ideas of getting this accomplished. Thanks for your help!
Just make your hash table values the arrays, and accumulate the values to them directly:
$Sites = 'CO','NE','IA'
$hshSite = #{}
Foreach ($Site in $Sites){$hshSite[$Site] = #()}
ForEach ($x in $csv)
{
$hshSite[$x.location] += <whatever it is your adding>
}
If there's a lot of entries in the csv, you might consider creating those values as arraylists instead of arrays.
$Sites = 'CO','NE','IA'
$hshSite = #{}
Foreach ($Site in $Sites){ $hshSite[$Site] = New-Object Collections.Arraylist }
ForEach ($x in $csv)
{
$hshSite[$x.location].add('<whatever it is your adding>') > $nul
}
You could quite easily do add items to a dynamically named array variable using the Get-Variable cmdlet. Similar to the following:
$MyArrayVariable123 = #()
$VariableNamePrefix = "MyArrayVariable"
$VariableNameNumber = "123"
$DynamicallyRetrievedVariable = Get-Variable -Name ($VariableNamePrefix + $VariableNameNumber)
$DynamicallyRetrievedVariable.Value += "added item"
After running the above code the $MyArrayVariable123 variable would be an array holding the single string added item.