{"id":913,"date":"2014-07-30T00:01:00","date_gmt":"2014-07-30T00:01:00","guid":{"rendered":"https:\/\/blogs.technet.microsoft.com\/heyscriptingguy\/2014\/07\/30\/use-powershell-to-write-verbose-output\/"},"modified":"2014-07-30T00:01:00","modified_gmt":"2014-07-30T00:01:00","slug":"use-powershell-to-write-verbose-output","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/scripting\/use-powershell-to-write-verbose-output\/","title":{"rendered":"Use PowerShell to Write Verbose Output"},"content":{"rendered":"

Summary<\/b>: Microsoft Scripting Guy, Ed Wilson, talks about using Windows PowerShell to write verbose output.<\/span><\/p>\n

 <\/p>\n

\"Hey, Hey, Scripting Guy! The other day, you said that I should not use Write-Host<\/b>. I even read that such usage is dangerous to the health of small canines in 2012 Scripting Games Commentary: STOP USING WRITE-HOST!<\/a>.<\/p>\n

—BP<\/p>\n

\"Hey, Hello BP,<\/p>\n

Microsoft Scripting Guy, Ed Wilson, is here. This morning I am sipping a cup of English Breakfast tea with a cinnamon stick and a squeeze of lemon. I am using my Surface Pro 2 to check my scripter@microsoft.com<\/a> email, and I saw another email from you. I decide to crank up Alan Parsons<\/a> on my 64-gig Zune HD<\/a>, and dive right in.<\/p>\n

Use Write-Verbose<\/h2>\n

To provide status updates, detailed tracking information, and the like, use the Write-Verbose<\/b> cmdlet The cool thing about using Write-Verbose<\/b> is that I never need to modify the script. For example, if I use a whole bunch of Write-Ho<\/b>st statements, eventually I may become tired of the clutter. But with Write-Verbose<\/b>, I can turn on the extra output only if I decide I need it. In addition, because Write-Verbose<\/b> writes to the verbose output stream, I can decide if I want to capture that output. This makes it a great option.<\/p>\n

Easy way to Write-Verbose<\/h2>\n

By default, Windows PowerShell is set up to use Write-Verbose<\/b>. The issue is that out of the box, verbose messages do not display. The $VerbosePreference<\/b> preference variable controls if Write-Verbose<\/b> statements appear. By default, the value of $VerbosePreference<\/b> is set to SilentlyContinue<\/b>, which means the messages do not appear. Because this is a simple preference variable, all I need to do is to change it in my profile. Now all verbose messages will appear in the output. This is probably not a good idea. If I want to change it, the statement is this:<\/p>\n

$VerbosePreference = "continue"<\/p>\n

If I do not want to make the change in my profile (we really, really do not want to make this change in our profiles), I can easily change it in my script. To do this, I first read the old value of $verbosePreference<\/b>, store that in a variable, and then change $verbosePreference<\/b> to continue<\/b>. <\/i>Here is the command to do this:<\/p>\n

  $oldverbose = $VerbosePreference<\/p>\n

  $VerbosePreference = "continue"<\/p>\n

Now, when I am done doing whatever I need to do, I simply set the old value. Here is that command:<\/p>\n

$VerbosePreference = $oldverbose<\/p>\n

To put this into a function, I create a switched parameter named $verbose<\/b>, and if I call that parameter, I change the existing value of $verbosePreference<\/b> to continue<\/b>, and then I can use Write-Verbose<\/b> to display progress, updates, and other information. Here is the complete function:<\/p>\n

Function test-verbose<\/p>\n

{<\/p>\n

 Param ([switch]$verbose)<\/p>\n

 if($verbose) {<\/p>\n

   $oldverbose = $VerbosePreference<\/p>\n

   $VerbosePreference = "continue" }<\/p>\n

 Write-Verbose "verbose output"<\/p>\n

 "Regular output"<\/p>\n

 $VerbosePreference = $oldverbose<\/p>\n

 }<\/p>\n

This is pretty simple. When I call the function the first time, only regular output displays. When I call the function with –verbose<\/b>, the verbose output appears along with the regular output. This is shown in the following image:<\/p>\n

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

Easier way to verbose output<\/h2>\n

The point of the earlier command is to show you how the preference variables effect the way Write-Verbose<\/b> works. (It is the same thing for other cmdlets, such as Write-Debug<\/b>). But there is a slightly easier way to do this, and it is to use the [cmdletbinding()]<\/b> attribute.<\/p>\n

Note<\/b>  There is a bit of confusion because that I must include Param() <\/b>in my function—even if I am not accepting parameterized input to the function. The reason is that I am using [cmdletbinding()]<\/b> as an attribute for my parameters. It does more than turn on automatic support for Write-Verbose<\/b>. See the following topic (which, incidentally, does not say anything about Write-Verbose<\/b>) for details: about_Functions_CmdletBindingAttribute<\/a>.<\/p>\n

All I need to do is add the [cmdletbinding()]<\/b> attribute over the Param()<\/b> <\/i>statement, and I automatically gain support for Write-Verbose<\/b>. Here is the command:<\/p>\n

Function Test-VerboseTwo<\/p>\n

{<\/p>\n

 [cmdletbinding()]<\/p>\n

 Param()<\/p>\n

 Write-Verbose "Verbose output"<\/p>\n

 "Regular output"<\/p>\n

}<\/p>\n

This is seven lines as opposed to ten lines of script. It saves me three lines. Of course, [cmdletbinding()]<\/b> does more than automatically wire Write-Verbose<\/b>, so the savings are potentially greater. To be honest, the script is not quite as easy to read, and [cmdletbinding()]<\/b> (which does not appear via Tab expansion in the ISE, nor does it really tell me what it is doing) behaves more like a black box. But hey, there is a whole topic that tells me what this little attribute does, so it is not really a black box.<\/p>\n

Here is the new function in action:<\/p>\n

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

It is all good, and pretty simple. Perhaps best of all, no small canines were harmed.<\/p>\n

BP, that is all there is to writing verbose output. Script Week will continue tomorrow when I will talk about more cool stuff.<\/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

Ed Wilson, Microsoft Scripting Guy<\/b><\/p>\n","protected":false},"excerpt":{"rendered":"

Summary: Microsoft Scripting Guy, Ed Wilson, talks about using Windows PowerShell to write verbose output.    Hey, Scripting Guy! The other day, you said that I should not use Write-Host. I even read that such usage is dangerous to the health of small canines in 2012 Scripting Games Commentary: STOP USING WRITE-HOST!. —BP  Hello BP, […]<\/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":[479,3,4,45],"class_list":["post-913","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-scripting","tag-output","tag-scripting-guy","tag-scripting-techniques","tag-windows-powershell"],"acf":[],"blog_post_summary":"

Summary: Microsoft Scripting Guy, Ed Wilson, talks about using Windows PowerShell to write verbose output.    Hey, Scripting Guy! The other day, you said that I should not use Write-Host. I even read that such usage is dangerous to the health of small canines in 2012 Scripting Games Commentary: STOP USING WRITE-HOST!. —BP  Hello BP, […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/913","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=913"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/913\/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=913"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/categories?post=913"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/tags?post=913"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}