{"id":6351,"date":"2008-04-20T19:59:33","date_gmt":"2008-04-20T19:59:33","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/powershell\/2008\/04\/20\/mindwarpingpower-cmdlets-scriptblock_parameters\/"},"modified":"2019-02-18T13:16:02","modified_gmt":"2019-02-18T20:16:02","slug":"mindwarpingpower-cmdlets-scriptblock_parameters","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/powershell\/mindwarpingpower-cmdlets-scriptblock_parameters\/","title":{"rendered":"$MindWarpingPower = $Cmdlets + $ScriptBlock_Parameters"},"content":{"rendered":"

A while ago I blogged about the power of Flexible Pipeling Scriptblock parameters<\/a>.  The mechanics of this are quite simple:  In a pipeline environment, if you provide a SCRIPTBLOCK to a parameter which does not take a SCRIPTBLOCK or an OBJECT, the PowerShell engine assigns the current pipeline object to the variable "$_", runs the scriptblock and uses whatever value it returns for the value of that parameter.  <\/p>\n

 <\/p>\n

Looking back at this, I don’t think we’ve done a good enough job explaining it or promulgating its use because it is incredibly powerful and I just don’t see it being used enough.  Let me give a couple of simple examples of how I used it this morning.  It is a technique that is well worth learning because you can do MIND-WARPING things once you figure out how to leverage it’s power.<\/p>\n

 <\/p>\n

This morning I wanted to email a set of PS1 files to someone.  Exchange blocks PS1 files so what I do is to rename these by added ".txt" to them.  I’ve see number of people sharing scripts that do something similar using the following technique:<\/p>\n

 <\/p>\n

foreach ($file in dir *.ps1) {
    $newName = $file.Name + ".TXT"
    copy-item -Path $file.Name -Destination $newName
}<\/font><\/p>\n

 <\/p>\n

That works but heavens, why do all that when you could just use ScriptBlock Parameters?  Now when you start using scriptblocks, you might what to leverage our friend -WHATIF until you are comfortable with how it works (isn’t -WHATIF da bomb?).<\/p>\n

Dir *.ps1 | Copy-Item -Destination {$_.Name + ".TXT"} -Whatif<\/font><\/p>\n

 <\/p>\n

On the way back, you can do this:<\/p>\n

Dir *.ps1.txt |Rename-item -NewName {$_.Name -replace ".txt"} -whatif<\/font><\/p>\n

 <\/p>\n

Now the scriptblock can be as large as you like you can do anything you want in it so feel free to get creative.  Imagine that you wanted to normalize\/serialize the names of a set of scripts.  You could do it this way:<\/p>\n

$Global:x=0; dir *.ps1 |copy-Item -Destination {"ScriptFile{0:000}" -f $global:x++} -whatif<\/font><\/p>\n

Here is an fun one:<\/p>\n

dir *.ps1 |copy-Item -Destination {if ($_.length -ge 100) {$_.Name + ".BIG"} else {$_.Name + ".SMALL"}} -whatif<\/font><\/p>\n

 <\/p>\n

Experiment and Enjoy!<\/p>\n

Jeffrey Snover [MSFT]
Windows Management Partner Architect
Visit the Windows PowerShell Team blog at:    http:\/\/blogs.msdn.com\/PowerShell<\/a>
Visit the Windows PowerShell ScriptCenter at:  http:\/\/www.microsoft.com\/technet\/scriptcenter\/hubs\/msh.mspx<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

A while ago I blogged about the power of Flexible Pipeling Scriptblock parameters.  The mechanics of this are quite simple:  In a pipeline environment, if you provide a SCRIPTBLOCK to a parameter which does not take a SCRIPTBLOCK or an OBJECT, the PowerShell engine assigns the current pipeline object to the variable "$_", runs the […]<\/p>\n","protected":false},"author":600,"featured_media":13641,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-6351","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-powershell"],"acf":[],"blog_post_summary":"

A while ago I blogged about the power of Flexible Pipeling Scriptblock parameters.  The mechanics of this are quite simple:  In a pipeline environment, if you provide a SCRIPTBLOCK to a parameter which does not take a SCRIPTBLOCK or an OBJECT, the PowerShell engine assigns the current pipeline object to the variable "$_", runs the […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts\/6351","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/users\/600"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/comments?post=6351"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts\/6351\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/media\/13641"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/media?parent=6351"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/categories?post=6351"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/tags?post=6351"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}