Powershell array ignorance - arrays

'scuse my ignorance...
I use #($var).Count so I can get a count even if $var contains 1 "item".
When my search returns nothing why does my array contain one item?
i.e.
PS C:\Windows\system32> $Groups = $null
Import-Module -Name "activedirectory"
$search = "aaaarggg"
$searchPat = `"*"` + $search + `"*"`
$Groups = Get-ADGroup -Filter {(name -like $searchPat)}
if ($Groups -eq $null) {
"No matches"
#($Groups).Count
}
else {
"Matches"
#($Groups).Count
}
No matches
1

As Lee said you create array which contains one item and the item is null. It may seem illogical, but it is done this way to give you consistent results when decrementing or incrementing the amount of items in the array. Look at the example below. If the #($null).count returned 0 you would jump from 2 to 0.
#($null,$null,$null).Count #output 3
#($null,$null).Count #output 2
#($null).Count #output 1
#().Count #output 0
Ingoring $null values inside the #() operator would also render such situations impossible to handle:
$("a",$null,"c").count #output 3
$("a","b","c").count #output 3

From the Powershell doc
You create an empty array as $a = #()
To count the elements you can simply do
$a.Count
$x = #()
$x.Count
0
As for processing the results of Get-ADGroup, that depends on what it returns. I think you'll find that simply doing
if ($Groups.Count -eq 0 ) {
# process
}
will work for you.

Related

How to declare a multidimensional 2D array in Powershell? [duplicate]

I have a way of doing Arrays in other languagues like this:
$x = "David"
$arr = #()
$arr[$x]["TSHIRTS"]["SIZE"] = "M"
This generates an error.
You are trying to create an associative array (hash). Try out the following
sequence of commands
$arr=#{}
$arr["david"] = #{}
$arr["david"]["TSHIRTS"] = #{}
$arr["david"]["TSHIRTS"]["SIZE"] ="M"
$arr.david.tshirts.size
Note the difference between hashes and arrays
$a = #{} # hash
$a = #() # array
Arrays can only have non-negative integers as indexes
from powershell.com:
PowerShell supports two types of multi-dimensional arrays: jagged arrays and true multidimensional arrays.
Jagged arrays are normal PowerShell arrays that store arrays as elements. This is very cost-effective storage because dimensions can be of different size:
$array1 = 1,2,(1,2,3),3
$array1[0]
$array1[1]
$array1[2]
$array1[2][0]
$array1[2][1]
True multi-dimensional arrays always resemble a square matrix. To create such an array, you will need to access .NET. The next line creates a two-dimensional array with 10 and 20 elements resembling a 10x20 matrix:
$array2 = New-Object 'object[,]' 10,20
$array2[4,8] = 'Hello'
$array2[9,16] = 'Test'
$array2
for a 3-dimensioanl array 10*20*10
$array3 = New-Object 'object[,,]' 10,20,10
To extend on what manojlds said above is that you can nest Hashtables. It may not be a true multi-dimensional array but give you some ideas about how to structure the data. An example:
$hash = #{}
$computers | %{
$hash.Add(($_.Name),(#{
"Status" = ($_.Status)
"Date" = ($_.Date)
}))
}
What's cool about this is that you can reference things like:
($hash."Name1").Status
Also, it is far faster than arrays for finding stuff. I use this to compare data rather than use matching in Arrays.
$hash.ContainsKey("Name1")
Hope some of that helps!
-Adam
Knowing that PowerShell pipes objects between cmdlets, it is more common in PowerShell to use an array of PSCustomObjects:
$arr = #(
[PSCustomObject]#{Name = 'David'; Article = 'TShirt'; Size = 'M'}
[PSCustomObject]#{Name = 'Eduard'; Article = 'Trouwsers'; Size = 'S'}
)
Or for older PowerShell Versions (PSv2):
$arr = #(
New-Object PSObject -Property #{Name = 'David'; Article = 'TShirt'; Size = 'M'}
New-Object PSObject -Property #{Name = 'Eduard'; Article = 'Trouwsers'; Size = 'S'}
)
And grep your selection like:
$arr | Where {$_.Name -eq 'David' -and $_.Article -eq 'TShirt'} | Select Size
Or in newer PowerShell (Core) versions:
$arr | Where Name -eq 'David' | Where Article -eq 'TShirt' | Select Size
Or (just get the size):
$arr.Where{$_.Name -eq 'David' -and $_.Article -eq 'TShirt'}.Size
Addendum 2020-07-13
Syntax and readability
As mentioned in the comments, using an array of custom objects is straighter and saves typing, if you like to exhaust this further you might even use the ConvertForm-Csv (or the Import-Csv) cmdlet for building the array:
$arr = ConvertFrom-Csv #'
Name,Article,Size
David,TShirt,M
Eduard,Trouwsers,S
'#
Or more readable:
$arr = ConvertFrom-Csv #'
Name, Article, Size
David, TShirt, M
Eduard, Trouwsers, S
'#
Note: values that contain spaces or special characters need to be double quoted
Or use an external cmdlet like ConvertFrom-SourceTable which reads fixed width table formats:
$arr = ConvertFrom-SourceTable '
Name Article Size
David TShirt M
Eduard Trouwsers S
'
Indexing
The disadvantage of using an array of custom objects is that it is slower than a hash table which uses a binary search algorithm.
Note that the advantage of using an array of custom objects is that can easily search for anything else e.g. everybody that wears a TShirt with size M:
$arr | Where Article -eq 'TShirt' | Where Size -eq 'M' | Select Name
To build an binary search index from the array of objects:
$h = #{}
$arr | ForEach-Object {
If (!$h.ContainsKey($_.Name)) { $h[$_.Name] = #{} }
If (!$h[$_.Name].ContainsKey($_.Article)) { $h[$_.Name][$_.Article] = #{} }
$h[$_.Name][$_.Article] = $_ # Or: $h[$_.Name][$_.Article]['Size'] = $_.Size
}
$h.david.tshirt.size
M
Note: referencing a hash table key that doesn't exist in Set-StrictMode will cause an error:
Set-StrictMode -Version 2
$h.John.tshirt.size
PropertyNotFoundException: The property 'John' cannot be found on this object. Verify that the property exists.
Here is a simple multidimensional array of strings.
$psarray = #(
('Line' ,'One' ),
('Line' ,'Two')
)
foreach($item in $psarray)
{
$item[0]
$item[1]
}
Output:
Line
One
Line
Two
Two-dimensional arrays can be defined this way too as jagged array:
$array = New-Object system.Array[][] 5,5
This has the nice feature that
$array[0]
outputs a one-dimensional array, containing $array[0][0] to $array[0][4].
Depending on your situation you might prefer it over $array = New-Object 'object[,]' 5,5.
(I would have commented to CB above, but stackoverflow does not let me yet)
you could also uses System.Collections.ArrayList to make a and array of arrays or whatever you want.
Here is an example:
$resultsArray= New-Object System.Collections.ArrayList
[void] $resultsArray.Add(#(#('$hello'),2,0,0,0,0,0,0,1,1))
[void] $resultsArray.Add(#(#('$test', '$testagain'),3,0,0,1,0,0,0,1,2))
[void] $resultsArray.Add("ERROR")
[void] $resultsArray.Add(#(#('$var', '$result'),5,1,1,0,1,1,0,2,3))
[void] $resultsArray.Add(#(#('$num', '$number'),3,0,0,0,0,0,1,1,2))
One problem, if you would call it a problem, you cannot set a limit. Also, you need to use [void] or the script will get mad.
Using the .net syntax (like CB pointed above)
you also add coherence to your 'tabular' array...
if you define a array...
and you try to store diferent types
Powershell will 'alert' you:
$a = New-Object 'byte[,]' 4,4
$a[0,0] = 111; // OK
$a[0,1] = 1111; // Error
Of course Powershell will 'help' you
in the obvious conversions:
$a = New-Object 'string[,]' 2,2
$a[0,0] = "1111"; // OK
$a[0,1] = 111; // OK also
Another thread pointed here about how to add to a multidimensional array in Powershell. I don't know if there is some reason not to use this method, but it worked for my purposes.
$array = #()
$array += ,#( "1", "test1","a" )
$array += ,#( "2", "test2", "b" )
$array += ,#( "3", "test3", "c" )
Im found pretty cool solvation for making arrays in array.
$GroupArray = #()
foreach ( $Array in $ArrayList ){
$GroupArray += #($Array , $null)
}
$GroupArray = $GroupArray | Where-Object {$_ -ne $null}
Lent from above:
$arr = ConvertFrom-Csv #'
Name,Article,Size
David,TShirt,M
Eduard,Trouwsers,S
'#
Print the $arr:
$arr
Name Article Size
---- ------- ----
David TShirt M
Eduard Trouwsers S
Now select 'David'
$arr.Where({$_.Name -eq "david"})
Name Article Size
---- ------- ----
David TShirt M
Now if you want to know the Size of 'David'
$arr.Where({$_.Name -eq "david"}).size
M

Query PSCustomObject Array for row with largest value

I'm trying to find the row with an attribute that is larger than the other row's attributes. Example:
$Array
Name Value
---- ----
test1 105
test2 101
test3 512 <--- Selects this row as it is the largest value
Here is my attempt to '1 line' this but It doesn't work.
$Array | % { If($_.value -gt $Array[0..($Array.Count)].value){write-host "$_.name is the largest row"}}
Currently it outputs nothing.
Desired Output:
"test1 is the largest row"
I'm having trouble visualizing how to do this efficiently with out some serious spaghetti code.
You could take advantage of Sort-Object to rank them by the property "Value" like this
$array = #(
[PSCustomObject]#{Name='test1';Value=105}
[PSCustomObject]#{Name='test2';Value=101}
[PSCustomObject]#{Name='test3';Value=512}
)
$array | Sort-Object -Property value -Descending | Select-Object -First 1
Output
Name Value
---- -----
test3 512
To incorporate your write host you can just run the one you select through a foreach.
$array | Sort-Object -Property value -Descending |
Select-Object -First 1 | Foreach-Object {Write-host $_.name,"has the highest value"}
test3 has the highest value
Or capture to a variable
$Largest = $array | Sort-Object -Property value -Descending | Select-Object -First 1
Write-host $Largest.name,"has the highest value"
test3 has the highest value
PowerShell has many built in features to make tasks like this easier.
If this is really an array of PSCustomObjects you can do something like:
$Array =
#(
[PSCustomObject]#{ Name = 'test1'; Value = 105 }
[PSCustomObject]#{ Name = 'test2'; Value = 101 }
[PSCustomObject]#{ Name = 'test3'; Value = 512 }
)
$Largest = ($Array | Sort-Object Value)[-1].Name
Write-host $Largest,"has the highest value"
This will sort your array according to the Value property. Then reference the last element using the [-1] syntax, then return the name property of that object.
Or if you're a purist you can assign the variable like:
$Largest = $Array | Sort-Object Value | Select-Object -Last 1 -ExpandProperty Name
If you want the whole object just remove .Name & -ExpandProperty Name respectively.
Update:
As noted PowerShell has some great tools to help with common tasks like sorting & selecting data. However, that doesn't mean there's never a need for looping constructs. So, I wanted to make a couple of points about the OP's own answer.
First, if you do need to reference array elements by index use a traditional For loop, which might look something like:
For( $i = 0; $i -lt $Array.Count; ++$i )
{
If( $array[$i].Value -gt $LargestValue )
{
$LargestName = $array[$i].Name
$LargestValue = $array[$i].Value
}
}
$i is commonly used as an iteration variable, and within the script block is used as the array index.
Second, even the traditional loop is unnecessary in this case. You can stick with the ForEach loop and track the largest value as and when it's encountered. That might look something like:
ForEach( $Row in $array )
{
If( $Row.Value -gt $LargestValue )
{
$LargestName = $Row.Name
$LargestValue = $Row.Value
}
}
Strictly speaking you don't need to assign the variables beforehand, though it may be a good practice to precede either of these with:
$LargestName = ""
$LargestValue = 0
In these examples you'd have to follow with a slightly modified Write-Host command
Write-host $LargestName,"has the highest value"
Note: Borrowed some of the test code from Doug Maurer's Fine Answer. Considering our answers were similar, this was just to make my examples more clear to the question and easier to test.
Figured it out, hopefully this isn't awful:
$Count = 1
$CurrentLargest = 0
Foreach($Row in $Array) {
# Compare This iteration vs the next to find the largest
If($Row.value -gt $Array.Value[$Count]){$CurrentLargest = $Row}
Else {$CurrentLargest = $Array[$Count]}
# Replace the existing largest value with the new one if it is larger than it.
If($CurrentLargest.Value -gt $Largest.Value){ $Largest = $CurrentLargest }
$Count += 1
}
Write-host $Largest.name,"has the highest value"
Edit: its awful, look at the other answers for a better way.

Appending objects to arrays in Powershell

I have the following code:
$DataType = "X,Y,Z"
$Data = "1,2,3"
$Table = #()
for ($i = 0; $i -le ($DataType.Count-1); $i++)
{
$Properties = #{$DataType[$i]=$Data[$i]}
$Object = New-Object -TypeName PSCustomObject -Property $Properties
$Table += $Object
}
$Table | Format-Table -AutoSize
I get this output:
X
-
1
What I would like to get is:
X Y Z
- - -
1 2 3
Thanks for your help!
Cutting a long story short:
$DataType, $Data | ConvertFrom-Csv
X Y Z
- - -
1 2 3
Ok, it needs a little explanation:
PowerShell will automatically unroll the array of strings ($DataType, $Data) and supply it as individual line items to the pipeline. The ConvertFrom-Csv cmdlet supports supplying the input table through the pipeline as separate lines (strings).
You can do the following instead:
$DataType = "X","Y","Z"
$Data = 1,2,3
$hash = [ordered]#{}
for ($i = 0; $i -lt $DataType.Count; $i++) {
$hash.Add($DataType[$i],$Data[$i])
}
$table = [pscustomobject]$hash
Explanation:
The code creates two collections, $DataType and $Data, of three items. $hash is an ordered hash table. [ordered] is used to preserve the order at which key-value pairs are added to the hash table. Since $hash is the object type hashtable, it contains the .Add(key,value) method for adding key-value pairs.
Since the [pscustomobject] type accelerator can be cast on a hash table, we can simply use the syntax [pscustomobject]$hash to create a new object.
If we consider your attempt, your variables are actually single strings rather than collections. Surrounding a value with quotes causes PowerShell to expand the inner contents as a string. When you index a string rather than a collection, you index the characters in the string rather than the entire item. You need to quote the individual elements between the commas so that the , acts as a separator rather than part of the string. You can see this behavior in the code below:
# DataType as a string
$DataType = "X,Y,Z"
$DataType[1]
,
# DataType as an array or collection
$DataType = "X","Y","Z"
$DataType[1]
Y
If you receive your data from another output in the current format, you can manipulate using $DataType = $DataType.Split(',') in order to create a collection. Alternatively you can treat the data as comma-separated and use the Import-Csv or ConvertFrom-Csv commands as in iRon's answer provided you order your strings properly.
Inside of your loop, you are adding three new objects to your collection $table rather than creating one object with three properties. $table += $Object creates an array called $table that appends a new item to the previous list from $table. If this was your original intention, you can view your collection by running $table | Format-List once you fix your $DataType and $Data variables.
When a collection is enumerated, the default table view displays the properties of the first object in a collection. Any succeeding objects will only display values for the first object's matching properties. So if object1 has properties X and Y and object2 has properties Y and Z, the console will only display values for properties X and Y for both objects. Format-List overrides this view and displays all properties of all objects. See below for an example of this behavior:
$obj1
X Y
- -
1 2
$obj2
Y Z
- -
3 4
$array = $obj1,$obj2
# Table View
$array
X Y
- -
1 2
3
# List View
$array | Format-List
X : 1
Y : 2
Y : 3
Z : 4
It seems that you want to create a single object with a property for each value in the arrays $DataType/$Data, but the problems are...
Neither $DataType nor $Data are arrays.
By creating your object inside the for loop you will create one object per iteration.
Since $DataType is a scalar variable $DataType.Count returns 1. Ordinarily, testing for $DataType.Count-1 would mean the loop never gets entered, but by the grace of using -le (so 0 -le 0 returns $true) instead of -lt, it does for exactly one iteration. Thus, you do get your single result object, but with only the first property created.
To fix this, let's create $DataType and $Data as arrays, as well as creating one set of properties before the loop to be used to create one result object after the loop...
...
$DataType = "X,Y,Z" -split ','
$Data = "1,2,3" -split ','
$Properties = #{}
for ($i = 0; $i -lt $DataType.Count; $i++)
{
$Properties[$DataType[$i]] = $Data[$i]
}
New-Object -TypeName PSCustomObject -Property $Properties | Format-Table -AutoSize
You'll also notice that $i -le ($DataType.Count-1) has been simplified to $i -lt $DataType.Count. On my system the above code outputs...
Y Z X
- - -
2 3 1
The properties are correct, but the order is not what you wanted. This is because Hashtable instances, such as $Properties, have no ordering among their keys. To ensure that the properties are in the order you specified in the question, on PowerShell 3.0 and above you can use this to preserve insertion order...
$Properties = [Ordered] #{}
What if you initialized $Table as an appendable like so:
$Table = New-Object System.Collections.ArrayList
for ($i = 0; $i -le ($DataType.Count-1); $i++)
{
$Properties = #{$DataType[$i]=$Data[$i]}
$Object = New-Object -TypeName PSCustomObject -Property $Properties
$Table.Add ( $Object )
}
Reformat your logic as needed.
One solution to this problem (if the inputs were two separate arrays):
$DataType = #( 'X','Y','Z' )
$Data = #( '1','2','3' )
$Table = New-Object psobject
for ($i = 0; $i -le ( $DataType.Count-1 ); $i++)
{
$Table | Add-Member -Name "$( $DataType[$i] )" -Value ( $Data[$i] ) -MemberType NoteProperty
}
$Table

Array.Find and IndexOf for multiple elements that are exactly the same object

I have trouble of getting index of the current element for multiple elements that are exactly the same object:
$b = "A","D","B","D","C","E","D","F"
$b | ? { $_ -contains "D" }
Alternative version:
$b = "A","D","B","D","C","E","D","F"
[Array]::FindAll($b, [Predicate[String]]{ $args[0] -contains "D" })
This will return:
D
D
D
But this code:
$b | % { $b.IndexOf("D") }
Alternative version:
[Array]::FindAll($b, [Predicate[String]]{ $args[0] -contains "D" }) | % { $b.IndexOf($_) }
Returns:
1
1
1
so it's pointing at the index of the first element. How to get indexes of the other elements?
You can do this:
$b = "A","D","B","D","C","E","D","F"
(0..($b.Count-1)) | where {$b[$_] -eq 'D'}
1
3
6
mjolinor's answer is conceptually elegant, but slow with large arrays, presumably due to having to build a parallel array of indices first (which is also memory-inefficient).
It is conceptually similar to the following LINQ-based solution (PSv3+), which is more memory-efficient and about twice as fast, but still slow:
$arr = 'A','D','B','D','C','E','D','F'
[Linq.Enumerable]::Where(
[Linq.Enumerable]::Range(0, $arr.Length),
[Func[int, bool]] { param($i) $arr[$i] -eq 'D' }
)
While any PowerShell looping solution is ultimately slow compared to a compiled language, the following alternative, while more verbose, is still much faster with large arrays:
PS C:\> & { param($arr, $val)
$i = 0
foreach ($el in $arr) { if ($el -eq $val) { $i } ++$i }
} ('A','D','B','D','C','E','D','F') 'D'
1
3
6
Note:
Perhaps surprisingly, this solution is even faster than Matt's solution, which calls [array]::IndexOf() in a loop instead of enumerating all elements.
Use of a script block (invoked with call operator & and arguments), while not strictly necessary, is used to prevent polluting the enclosing scope with helper variable $i.
The foreach statement is faster than the Foreach-Object cmdlet (whose built-in aliases are % and, confusingly, also foreach).
Simply (implicitly) outputting $i for each match makes PowerShell collect multiple results in an array.
If only one index is found, you'll get a scalar [int] instance instead; wrap the whole command in #(...) to ensure that you always get an array.
While $i by itself outputs the value of $i, ++$i by design does NOT (though you could use (++$i) to achieve that, if needed).
Unlike Array.IndexOf(), PowerShell's -eq operator is case-insensitive by default; for case-sensitivity, use -ceq instead.
It's easy to turn the above into a (simple) function (note that the parameters are purposely untyped, for flexibility):
function get-IndicesOf($Array, $Value) {
$i = 0
foreach ($el in $Array) {
if ($el -eq $Value) { $i }
++$i
}
}
# Sample call
PS C:\> get-IndicesOf ('A','D','B','D','C','E','D','F') 'D'
1
3
6
You would still need to loop with the static methods from [array] but if you are still curious something like this would work.
$b = "A","D","B","D","C","E","D","F"
$results = #()
$singleIndex = -1
Do{
$singleIndex = [array]::IndexOf($b,"D",$singleIndex + 1)
If($singleIndex -ge 0){$results += $singleIndex}
}While($singleIndex -ge 0)
$results
1
3
6
Loop until a match is not found. Assume the match at first by assigning the $singleIndex to -1 ( Which is what a non match would return). When a match is found add the index to a results array.

In Powershell how can I check if all items from one array exist in a second array?

So let's say I have this array:
$requiredFruit= #("apple","pear","nectarine","grape")
And I'm given a second array called $fruitIHave. How can I check that $fruitIHave has everything in $requiredFruit. It doesn't matter if there are more items in $fruitIHave just as long as everything in $requiredFruit is there.
I know I could just iterate over the list, but that seems inefficient, is there a built-in method for doing this?
Do you try Compare-Object :
$requiredFruit= #("apple","pear","nectarine","grape")
$HaveFruit= #("apple","pin","nectarine","grape")
Compare-Object $requiredFruit $haveFruit
InputObject SideIndicator
----------- -------------
pin =>
pear <=
Compare-Object $requiredFruit $haveFruit | where {$_.sideindicator -eq "<="} | % {$_.inputobject}
pear
If you have the arrays:
$requiredFruit= #("apple","pear","nectarine","grape")
$someFruit= #("apple","banana","pear","nectarine","orange","grape")
$moreFruit= #("apple","banana","nectarine","grape")
You can get a boolean result with:
'Check $someFruit for $requiredFruit'
-not #($requiredFruit| where {$someFruit -notcontains $_}).Count
'Check $moreFruit for $requiredFruit'
-not #($requiredFruit| where {$moreFruit -notcontains $_}).Count
Using the count of an array protects against a single value not matching that evaluates as False. For example:
# Incorrect result
-not (0| where {(1,2) -notcontains $_})
# Correct result
-not #(0| where {(1,2) -notcontains $_}).Count
With PowerShell v3, you can use select -first 1 to stop the pipeline when the first mismatch is found (in v2 select -first 1 allows only one object through, but previous elements of the pipeline continue to process).
-not #($requiredFruit| where {$moreFruit -notcontains $_}| select -first 1).Count
Not exactly "builtin" but:
[regex] $RF_regex = ‘(?i)^(‘ + (($requiredFruit |foreach {[regex]::escape($_)}) –join “|”) + ‘)$’
($fruitIHave -match $RF_regex).count -eq $requiredFruit.count
That creates an alternating regex from the elements of $requiredFruit. Matched against $fruitIHave, it will return all the items that matched. If $fruitIhave could potentially have duplicates of the same fruit you may need to run that match result through get-unique before you do the count. It may be slower than iterating over the list for a single comparison, but once you have the regex built it will do repetitive matches very efficiently.
One way or the other, you're going to have to iterate through one or both arrays. Here's a one-liner approach:
$hasAllRequiredFruit = ($requiredFruit | Where-Object { $fruitIHave -contains $_ }).Length -eq $requiredFruit.Length;
A foreach loop would be better because you can stop iterating as soon as you find a required fruit that is missing:
$hasAllRequiredFruit = $true;
foreach ($f in $requiredFruit)
{
if ($fruitIHave -notcontains $f)
{
$hasAllRequiredFruit = $false;
break;
}
}

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