{"id":304,"date":"2006-10-30T11:04:38","date_gmt":"2006-10-30T19:04:38","guid":{"rendered":"http:\/\/testblog.sapien.com\/index.php\/2006\/10\/30\/funky-times-with-write-host-and-out-host\/"},"modified":"2006-10-30T11:04:38","modified_gmt":"2006-10-30T19:04:38","slug":"funky-times-with-write-host-and-out-host","status":"publish","type":"post","link":"https:\/\/dev.sapien.com\/blog\/2006\/10\/30\/funky-times-with-write-host-and-out-host\/","title":{"rendered":"Funky times with Write-Host and Out-Host"},"content":{"rendered":"
\n

As you know, things aren’t always what they seem in WindowsPowerShell. Take this short script:<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

"PART 1 ————"<\/o:p><\/span><\/font><\/p>\n

"Hello1"<\/o:p><\/span><\/font><\/p>\n

out-host -input "Hello2"<\/o:p><\/span><\/font><\/p>\n

write-host "Hello3"<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

Function TestFunc {<\/o:p><\/span><\/font><\/p>\n

  "Function1"<\/o:p><\/span><\/font><\/p>\n

  Out-Host -input"Function2"<\/o:p><\/span><\/font><\/p>\n

  Write-Host "Function3"<\/o:p><\/span><\/font><\/p>\n

  Return "Function4"<\/o:p><\/span><\/font><\/p>\n

}<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

"PART 2 ————"<\/o:p><\/span><\/font><\/p>\n

$out = TestFunc<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

"PART 3 ————"<\/o:p><\/span><\/font><\/p>\n

$out<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

The output of the first part is what you’d expect:<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

PART 1 ————<\/o:p><\/span><\/font><\/p>\n

Hello1<\/o:p><\/span><\/font><\/p>\n

Hello2<\/o:p><\/span><\/font><\/p>\n

Hello3<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

All three of the command shown produce output. Fine.However, the second part calls function TestFunc, and produces the followingoutput:<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

PART 2 ————<\/o:p><\/span><\/font><\/p>\n

Function2<\/o:p><\/span><\/font><\/p>\n

Function3<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

Here, both Out-Host and Write-Host are actually spitting outtext to the console. This occurred when thefunction ran; <\/span><\/i>this “Part 2” output wasn’t part ofthe function’s actual return value. When you look at what was returned<\/span><\/i> by the function:<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

PART 3 ————<\/o:p><\/span><\/font><\/p>\n

Function1<\/o:p><\/span><\/font><\/p>\n

Function4<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

You can see that anything within a function which is just “output”(that is, without using a cmdlet) becomes concatenated to the function’stotal return. This is in addition to anything explicitly returned using theReturn keyword. <\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

So you have to be careful in how you produce output. Withina script, it’s nearly always safer to produce output by using an outputcmdlet, because within a function any other means won’t produce output, <\/span><\/i>it’ll produce return values<\/span><\/i> from the function. I preferto produce all my return values using the Return keyword. In summary, producingoutput like this:<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

“This is output”<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

That is, not using a cmdlet, is a bad practice (for me, atleast), because it can create inconsistent results depending on where that codeactually occurs. This leaves the question: What’s the difference betweenOut-Host and Write-Host? I know Write-Host doesn’t work properly when you’rehosting PowerShell within another application: Anything produced by Write-Hostproduces a “function not defined” (or some such) error which Ihaven’t wrapped my head around yet. Perhaps perusing the SDK in moredetail will reveal the subtleties there. Stay tuned!<\/o:p><\/span><\/font><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

\n

As you know, things aren’t always what they seem in WindowsPowerShell. Take this short script:<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

"PART 1 ————"<\/o:p><\/span><\/font><\/p>\n

"Hello1"<\/o:p><\/span><\/font><\/p>\n

out-host -input "Hello2"<\/o:p><\/span><\/font><\/p>\n

write-host "Hello3"<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

Function TestFunc {<\/o:p><\/span><\/font><\/p>\n

  "Function1"<\/o:p><\/span><\/font><\/p>\n

  Out-Host -input"Function2"<\/o:p><\/span><\/font><\/p>\n

  Write-Host "Function3"<\/o:p><\/span><\/font><\/p>\n

  Return "Function4"<\/o:p><\/span><\/font><\/p>\n

}<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

"PART 2 ————"<\/o:p><\/span><\/font><\/p>\n

$out = TestFunc<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

"PART 3 ————"<\/o:p><\/span><\/font><\/p>\n

$out<\/o:p><\/span><\/font><\/p>\n

 <\/o:p><\/span><\/font><\/p>\n

The output of the …<\/p>\n","protected":false},"author":2,"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":[],"class_list":["post-304","post","type-post","status-publish","format-standard","hentry","category-windows-powershell"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/posts\/304","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\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/comments?post=304"}],"version-history":[{"count":0,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/posts\/304\/revisions"}],"wp:attachment":[{"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/media?parent=304"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/categories?post=304"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dev.sapien.com\/blog\/wp-json\/wp\/v2\/tags?post=304"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}