{"id":1541,"date":"2009-06-11T07:00:36","date_gmt":"2009-06-11T15:00:36","guid":{"rendered":"http:\/\/www.sapien.com\/blog\/2009\/06\/11\/select-propertyvalue\/"},"modified":"2009-06-11T07:00:36","modified_gmt":"2009-06-11T15:00:36","slug":"select-propertyvalue","status":"publish","type":"post","link":"https:\/\/dev.sapien.com\/blog\/2009\/06\/11\/select-propertyvalue\/","title":{"rendered":"Select-PropertyValue"},"content":{"rendered":"

Because PowerShell is all about the objects, I often point out to beginners to use the Select-Object<\/strong> cmdlet to see all the properties of an object and their values.<\/p>\n

PS C:\\> get-process powershell | select *<\/font><\/p>\n

Using Get-Member<\/strong> is helpful to discover property names but sometimes you need to see a value to know which property or properties you really want to work with. That’s where my Select-Object<\/strong> suggestion comes in. Unfortunately not every property is defined for every object so you can end up with a lot of empty properties. What I wanted was a way to only display properties for an object that have a value. Here’s my solution.<\/p>\n

I wrote a filtering function called Select-PropertyValue.<\/p>\n

\n
\n
Filter Select-PropertyValue {<\/pre>\n
    Param([switch<\/span>]$NoWMISystem,[switch<\/span>]$debug)<\/pre>\n
 <\/pre>\n
    if<\/span> ($debug) {<\/pre>\n
        $debugPreference=\"Continue\"<\/span><\/pre>\n
     }<\/pre>\n
 <\/pre>\n
    Write-Debug \"In process\"<\/span><\/pre>\n
    if<\/span> (-Not $properties) {<\/pre>\n
        Write-Debug \"Creating property list\"<\/span><\/pre>\n
        #get properties for the pipelined object sorted by property name<\/span><\/pre>\n
        $properties=$_ | Get-Member -membertype Properties | sort Name<\/pre>\n
        <\/pre>\n
        #filter out WMI System properties if -NoWMISystem<\/span><\/pre>\n
        if<\/span> ($NoWMISystem) {<\/pre>\n
            Write-Debug \"Filtering out WMI System properties\"<\/span><\/pre>\n
            $properties=$properties | where {$_.name -notlike<\/span> \"__*\"<\/span>}<\/pre>\n
        }<\/pre>\n
        <\/pre>\n
        Write-Debug \"Found $($properties.count) properties\"<\/span><\/pre>\n
    }<\/pre>\n
    <\/pre>\n
     #create an empty custom object<\/span><\/pre>\n
     Write-Debug \"Creating empty object\"<\/span><\/pre>\n
     $obj=New-Object PSObject<\/pre>\n
    <\/pre>\n
    #enumerate the list of properties<\/span><\/pre>\n
    foreach<\/span> ($property in<\/span> $properties) { <\/pre>\n
        Write-Debug \"Checking $($property.name)\"<\/span><\/pre>\n
         #if object has a value for the current property<\/span><\/pre>\n
         if<\/span> ($_.($property.name)) {       <\/pre>\n
            Write-Debug \"found value $($_.($property.name))\"<\/span><\/pre>\n
            <\/pre>\n
            #assign properties<\/span><\/pre>\n
            $obj | Add-Member -MemberType Noteproperty -name $property.Name -value ($_.($property.name))<\/pre>\n
                 <\/pre>\n
         } #end If<\/span><\/pre>\n
    } #end ForEach<\/span><\/pre>\n
    <\/pre>\n
    #write the custom object to the pipeline<\/span><\/pre>\n
    write $obj<\/pre>\n
 <\/pre>\n
} #end  function<\/span><\/pre>\n<\/div>\n<\/div>\n
This function is designed to accept pipelined input. Normally you would write such a function with Begin, Process and End scriptblocks. However if you don’t use the Begin and End scriptblocks, you can create a filter as I’ve done. The filtering function’s code is what would be found in the Process scriptblock.<\/p>\n
The function can also take two parameters, -debug and -NoWMISystem. The former will enable debug messages throughout the function. I inserted Write-Debug<\/strong> commands throughout the function so I could track what was happening. Using -debug allows me to see the output of those commands. The second parameter will suppress the system classes associated with a WMI object such as __RELPATH and __GENUS. I rarely need to see this information.<\/p>\n
To use the function I first dot source the ps1 file as it also creates an alias for the function, spv. Now I can run command like this:<\/p>\n
PS C:\\> gwmi win32_bios | spv -noWMISystem<\/font><\/p>\n
The WIn32_Bios object is piped to the function. The first step the function takes is to build a variable with all of the property names for the pipelined object.<\/p>\n
\n
\n
if<\/span> (-Not $properties) {<\/pre>\n
        Write-Debug \"Creating property list\"<\/span><\/pre>\n
        #get properties for the pipelined object sorted by property name<\/span><\/pre>\n
        $properties=$_ | Get-Member -membertype Properties | sort Name<\/pre>\n<\/div>\n<\/div>\n
These are stored in a variable, $properties, that I only need to create once. It $properties already exists the function skips this step.<\/p>\n
If I’ve specified -nowmisystem, then $properties is filtered further to remove the system classes.<\/p>\n
\n
\n
#filter out WMI System properties if -NoWMISystem<\/span><\/pre>\n
 if<\/span> ($NoWMISystem) {<\/pre>\n
     Write-Debug \"Filtering out WMI System properties\"<\/span><\/pre>\n
     $properties=$properties | where {$_.name -notlike<\/span> \"__*\"<\/span>}<\/pre>\n
 }<\/pre>\n<\/div>\n<\/div>\n
The function is going to create a new custom object and copy the properties that have values so it first creates an empty object.<\/p>\n
\n
\n
#create an empty custom object<\/span><\/pre>\n
Write-Debug \"Creating empty object\"<\/span><\/pre>\n
$obj=New-Object PSObject<\/pre>\n<\/div>\n<\/div>\n
The $properties variable is enumerated one at a time. If the property of the pipelined object has a value, then the property name and value are added to the custom object.<\/p>\n
\n
\n
#enumerate the list of properties<\/span><\/pre>\n
foreach<\/span> ($property in<\/span> $properties) { <\/pre>\n
    Write-Debug \"Checking $($property.name)\"<\/span><\/pre>\n
     #if object has a value for the current property<\/span><\/pre>\n
     if<\/span> ($_.($property.name)) {       <\/pre>\n
        Write-Debug \"found value $($_.($property.name))\"<\/span><\/pre>\n
        <\/pre>\n
        #assign properties<\/span><\/pre>\n
        $obj | Add-Member -MemberType Noteproperty -name $property.Name -value ($_.($property.name))<\/pre>\n
             <\/pre>\n
     } #end If<\/span><\/pre>\n
} #end<\/span> ForEach<\/pre>\n<\/div>\n<\/div>\n
After all the properties have been checked the object is written to the pipeline.<\/p>\n
\n
\n
#write the custom object to the pipeline<\/span><\/pre>\n
write $obj<\/pre>\n<\/div>\n<\/div>\n
This is now more useful to me:<\/p>\n
PS C:\\> gwmi win32_bios | spv -n <\/font><\/p>\n
BiosCharacteristics  : {7, 8, 9, 11…}
BIOSVersion          : {FUJ    – 1180000}
Caption              : Default System BIOS
CurrentLanguage      : enUS
Description          : Default System BIOS
InstallableLanguages : 2
ListOfLanguages      : {enUS, jaJP}
Manufacturer         : FUJITSU \/\/ Phoenix Technologies Ltd.
Name                 : Default System BIOS
PrimaryBIOS          : True
ReleaseDate          : 20080602000000.000000+000
SerialNumber         : R6Y02331
SMBIOSBIOSVersion    : Version 1.18
SMBIOSMajorVersion   : 2
SMBIOSMinorVersion   : 4
SMBIOSPresent        : True
SoftwareElementID    : Default System BIOS
SoftwareElementState : 3
Status               : OK
Version              : FUJ    – 1180000<\/font> <\/p>\n
The function writes to the pipeline so I can pipe it to other cmdlets as well. This especially useful when you want to export as you’ll end up only exporting properties with values.<\/p>\n
PS C:\\> gwmi win32_service | spv -n | export-csv c:\\test\\servicedata.csv -notype<\/font><\/p>\n
\n
Download the script file with this function here.<\/a><\/p>\n<\/div>\n
Enjoy and if you extend functionality, I hope you’ll let me know.<\/p>\n","protected":false},"excerpt":{"rendered":"
Because PowerShell is all about the objects, I often point out to beginners to use the Select-Object cmdlet to see all the properties of an object and their values.<\/p>\n
get-process powershell | select *<\/p>\n
Using Get-Member is helpful to discover property names but sometimes you need to see a value to know which property or properties you really want to work with. That’s where my Select-Object suggestion comes in. Unfortunately not every property is defined for every object so you can end up with a lot of empty properties. What I wanted was a way to only display properties for an object that have a value. Here’s my solution.<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[25],"tags":[513,82,28,57,383],"class_list":["post-1541","post","type-post","status-publish","format-standard","hentry","category-windows-powershell","tag-filter","tag-objects","tag-powershell","tag-scripting","tag-select"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/posts\/1541","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/comments?post=1541"}],"version-history":[{"count":0,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/posts\/1541\/revisions"}],"wp:attachment":[{"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/media?parent=1541"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/categories?post=1541"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/tags?post=1541"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}