{"id":12381,"date":"2011-10-16T00:01:00","date_gmt":"2011-10-16T00:01:00","guid":{"rendered":"https:\/\/blogs.technet.microsoft.com\/heyscriptingguy\/2011\/10\/16\/dealing-with-powershell-hash-table-quirks\/"},"modified":"2011-10-16T00:01:00","modified_gmt":"2011-10-16T00:01:00","slug":"dealing-with-powershell-hash-table-quirks","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/scripting\/dealing-with-powershell-hash-table-quirks\/","title":{"rendered":"Dealing with PowerShell Hash Table Quirks"},"content":{"rendered":"

Summary:<\/strong> Microsoft Scripting Guy Ed Wilson shows how to deal with two Windows PowerShell hash table quirks.<\/p>\n

 <\/p>\n

Microsoft Scripting Guy Ed Wilson here. Our week in Ottawa draws to a close. We leave for Montreal today, and are really excited about the Windows PowerShell people we will meet while we are there. I enjoyed working on my Windows PowerShell Quiz scripts this week. The point of the articles was not so much about creating a quiz engine, but the fact that it offered a good exercise for working on function design and with hash tables.<\/p>\n

Today, I want to focus in on two aspects of hash tables that came up this week while I was writing the scripts. The first aspect I want talk about is piping a hash table to other cmdlets. This also comes into play when supplying a hash table to a cmdlet as an inputobject<\/b>. As an example, I will use the hash table created in yesterday’s post, Easily Create a PowerShell Hash Table<\/a>. <\/i><\/p>\n

Here is the DemoHashtableWithProcesses.ps1 script that creates a hash table from process information:<\/p>\n

$hash = $null<\/p>\n

$hash = @{}<\/p>\n

$proc = get-process | Sort-Object -Property name -Unique<\/p>\n

 <\/p>\n

foreach ($p in $proc)<\/p>\n

{<\/p>\n

 $hash.add($p.name,$p.id)<\/p>\n

}<\/p>\n

$hash<\/p>\n

 <\/p>\n

The $hash<\/b> variable contains a hash table with a number of key value pairs in it. The count<\/b> <\/i>property tells me how many items are in the hash table. When I pipe the hash table to the Get-Random<\/b> cmdlet and tell the Get-Random<\/b> cmdlet to return one random key value pair, the results are confusing. Here is the command I am talking about:<\/p>\n

$hash | Get-Random -Count 1<\/p>\n

\"Image<\/a><\/p>\n

As seen in the previous figure, all the key value pairings from the hash table are returned. I was expecting a single, randomly selected pair. I see this same problem when using the Sort-Object <\/b>cmdlet. For example, when I type the following command, I expect to see the processes sorted by name:<\/p>\n

$hash | Sort-Object -Property name<\/p>\n

But as shown in the following figure, the sort is not working.<\/p>\n

\"Image<\/a><\/p>\n

The problem extends itself even to the Where-Object<\/b>. The following command returns nothing, even though there is a process with a value of 6108:<\/p>\n

$hash | Where-Object { $_.value -eq 6108}<\/p>\n

I solved this problem earlier in the week in Create a PowerShell Quiz Script<\/a> post by getting a collection of keys, walking through the keys, and using the item<\/b> <\/i>method to retrieve the associated value.<\/p>\n

The applicable line of code is shown here:<\/p>\n

Function New-Question<\/p>\n

{<\/p>\n

 Param(<\/p>\n

  [hashtable]$Puzzle<\/p>\n

 )<\/p>\n

  Foreach ($p in $puzzle.KEYS)<\/p>\n

   {<\/p>\n

    $rtn = Read-host “What is the cmdlet name $($puzzle.item($P))”<\/p>\n

    If($puzzle.contains($rtn))<\/p>\n

     { “Correct $($puzzle.item($P)) equals $p” }<\/p>\n

    ELSE<\/p>\n

     {“Sorry. $rtn is not right. $($puzzle.item($P)) is $p” }<\/p>\n

    } #end foreach $P<\/p>\n

}
#end function New-Question<\/p>\n

Though this methodology works just fine for the Windows PowerShell Quiz script, it is too much trouble to do for a simple pipeline operation. There needs to be an easier way to walk through a hash table. And there is! The secret is to use the getEnumerator<\/b> <\/i>method from the hashtable <\/b>object. If I want to choose a random key value pair from a hash table, I call the getenumerator<\/b> <\/i>method prior to passing it to the Get-Random<\/b> cmdlet. The command is shown here:<\/p>\n

$hash.getenumerator() | Get-Random -Count 1<\/p>\n

The GetEnumerator<\/b> <\/i>method works the same way with the Where-Object<\/b> cmdlet. The command is shown here:<\/p>\n

$hash.GetEnumerator() | Where-Object { $_.value -eq 6108}<\/p>\n

It also works with the Sort-Object<\/b> cmdlet, as shown here:<\/p>\n

$hash.GetEnumerator() | Sort-Object -Property name<\/p>\n

All three of these commands and their associated output are shown in the following figure.<\/p>\n

\"Image<\/a><\/p>\n

 <\/p>\n

The second topic I want to talk about came up while I was writing Create a PowerShell Quiz by Reading a Text File<\/a>. <\/i><\/p>\n

All the examples of using the ConvertFrom-StringData <\/b>cmdlet illustrate using a Here-String <\/b>or similar hardcoded string data to create a hash table. This technique will not work for me because I wanted to read a text file. My first attempt generated the error shown here:<\/p>\n

PS C:\\> ConvertFrom-StringData C:\\fso\\Questions.txt<\/p>\n

ConvertFrom-StringData : Data line ‘C:\\fso\\Questions.txt’ is not in ‘name=value’ format.<\/p>\n

At line:1 char:23<\/p>\n

+ ConvertFrom-StringData <<<< C:\\fso\\Questions.txt<\/p>\n

    + CategoryInfo          : InvalidOperation: (:) [ConvertFrom-StringData], PSInvalidOperationException<\/p>\n

    + FullyQualifiedErrorId : InvalidOperation,Microsoft.PowerShell.Commands.ConvertFromStringDataCommand<\/p>\n

The error basically says that my input file is not in name=value<\/b> format. But as shown in the following figure, that is not true.<\/p>\n

\"Image<\/a><\/p>\n

So, I thought I needed to read the content of the file first. This time I got the error shown here:<\/p>\n

PS C:\\> ConvertFrom-StringData (Get-content C:\\fso\\Questions.txt)<\/p>\n

ConvertFrom-StringData : Cannot convert ‘System.Object[]’ to the type ‘System.String’ required by parameter ‘StringData<\/p>\n

‘. Specified method is not supported.<\/p>\n

At line:1 char:23<\/p>\n

+ ConvertFrom-StringData <<<<  (Get-content C:\\fso\\Questions.txt)<\/p>\n

    + CategoryInfo          : InvalidArgument: (:) [ConvertFrom-StringData], ParameterBindingException<\/p>\n

    + FullyQualifiedErrorId : CannotConvertArgument,Microsoft.PowerShell.Commands.ConvertFromStringDataCommand<\/p>\n

Next, I got the idea to pipe the information to the cmdlet. When I did this, it appeared I had hit upon a successful combination:<\/p>\n

PS
C:\\> Get-Content C:\\fso\\Questions.txt | ConvertFrom-StringData<\/p>\n

 <\/p>\n

Name                           Value<\/p>\n

—-                           —–<\/p>\n

Canberra                       Australia<\/p>\n

Berlin                         Germany<\/p>\n

Ottawa                         Canada<\/p>\n

I then tried to use my hash table. So I stored the hash table in a variable, and attempted to access the keys<\/b> <\/i>property, as shown here:<\/p>\n

PS C:\\> $hash = Get-Content C:\\fso\\Questions.txt | ConvertFrom-StringData<\/p>\n

PS C:\\> $hash.keys<\/p>\n

Nothing came back. There are no keys? So, I examined the $hash<\/b> variable by using the Get-Member <\/b> cmdlet (gm<\/b> is an alias). The results of this exploration are shown here:<\/p>\n

PS C:\\> $hash | gm<\/p>\n

 <\/p>\n

   TypeName: System.Collections.Hashtable<\/p>\n

 <\/p>\n

Name<\/span>                           MemberType<\/span>                  Definition<\/span><\/p>\n

Add                              Method                            System.Void Add(System.Object key, System.Object value)<\/p>\n

Clear                             Method                           System.Void Clear()<\/p>\n

Clone                            Method                            System.Object Clone()<\/p>\n

Contains                        Method                            bool Contains(System.Object key)<\/p>\n

ContainsKey                   Method                           bool ContainsKey(System.Object key)<\/p>\n

ContainsValue                Method                           bool ContainsValue(System.Object value)<\/p>\n

CopyTo                         Method                         System.Void CopyTo(array array, int arrayIndex)<\/p>\n

Equals                           Method                         bool Equals(System.Object obj)<\/p>\n

GetEnumerator              Method                         System.Collections.IDictionaryEnumerator GetEnumerator()<\/p>\n

GetHashCode                Method                         int GetHashCode()<\/p>\n

GetObjectData               Method                         System.Void GetObjectData(System.Runtime.Serialization.SerializationInfo inf…<\/p>\n

GetType                        Method                         type GetType()<\/p>\n

OnDeserialization           Method                         System.Void OnDeserialization(System.Object sender)<\/p>\n

Remove                         Method                         System.Void Remove(System.Object key)<\/p>\n

ToString                        Method                         string ToString()<\/p>\n

Item                              ParameterizedProperty   System.Object Item(System.Object key) {get;set;}<\/p>\n

Count                            Property                        System.Int32 Count {get;}<\/p>\n

IsFixedSize                     Property                        System.Boolean IsFixedSize {get;}<\/p>\n

IsReadOnly                    Property                        System.Boolean IsReadOnly {get;}<\/p>\n

IsSynchronized               Property                        System.Boolean IsSynchronized {get;}<\/p>\n

Keys                              Property                        System.Collections.ICollection Keys {get;}<\/p>\n

SyncRoot                       Property                        System.Object SyncRoot {get;}<\/p>\n

Values                           Property                        System.Collections.ICollection Values {get;}<\/p>\n

 <\/p>\n

Well, it looks like it is a hash table. So how about looking at the values<\/b> <\/i>property? The results are shown here—nothing. Next, I use the count<\/b> <\/i>property, and it tells me I have three items in the hash table.<\/p>\n

PS C:\\> $hash.values<\/p>\n

PS C:\\> $hash.count<\/p>\n

3<\/p>\n

This looks really weird. Then I had an idea: I wonder if somehow I obtained an array. I index into the array, and sure enough, I have an array of hash tables. This is shown here:<\/p>\n

PS C:\\> $hash[0]<\/p>\n

Name<\/span>                           Value<\/span><\/p>\n

Canberra                       Australia<\/p>\n

 <\/p>\n

PS C:\\> $hash[1]<\/p>\n

Name<\/span>                           Value<\/span><\/p>\n

Berlin                            Germany<\/p>\n

 <\/p>\n

PS C:\\> $hash[2]<\/p>\n

Name<\/span>                           Value<\/span><\/p>\n

Ottawa                          Canada<\/p>\n

I have an array of hash tables because of the way that Get-Content<\/b> returns information. It returns an array. One element for each line of the file is a behavior that is normally fine. But in this example, the behavior causes problems. The easy way around this is to use the ReadAlltext<\/b> <\/i>static method from the io.file <\/b>.NET Framework class. This technique is shown here:<\/p>\n

PS C:\\> ConvertFrom-StringData ([io.file]::ReadAllText(“C:\\fso\\Questions.txt”))<\/p>\n

Name<\/span>                           Value<\/span><\/p>\n

Berlin                            Germany<\/p>\n

Canberra                       Australia<\/p>\n

Ottawa                          Canada<\/p>\n

 <\/p>\n

That’s it for today. Join me tomorrow for more Windows PowerShell goodness. See you then.<\/p>\n

I invite you to follow me on Twitter<\/a> and Facebook<\/a>. If you have any questions, send email to me at scripter@microsoft.com<\/a>, or post your questions on the Official Scripting Guys Forum<\/a>. See you tomorrow. Until then, peace.<\/p>\n

 <\/p>\n

Ed Wilson, Microsoft Scripting Guy<\/b><\/p>\n

 <\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Summary: Microsoft Scripting Guy Ed Wilson shows how to deal with two Windows PowerShell hash table quirks.   Microsoft Scripting Guy Ed Wilson here. Our week in Ottawa draws to a close. We leave for Montreal today, and are really excited about the Windows PowerShell people we will meet while we are there. I enjoyed […]<\/p>\n","protected":false},"author":596,"featured_media":87096,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[292,3,4,45],"class_list":["post-12381","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-scripting","tag-arrays-hashtables-and-dictionary-objects","tag-scripting-guy","tag-scripting-techniques","tag-windows-powershell"],"acf":[],"blog_post_summary":"

Summary: Microsoft Scripting Guy Ed Wilson shows how to deal with two Windows PowerShell hash table quirks.   Microsoft Scripting Guy Ed Wilson here. Our week in Ottawa draws to a close. We leave for Montreal today, and are really excited about the Windows PowerShell people we will meet while we are there. I enjoyed […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/12381","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/users\/596"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/comments?post=12381"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/12381\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/media\/87096"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/media?parent=12381"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/categories?post=12381"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/tags?post=12381"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}