{"id":71942,"date":"2015-07-25T00:01:00","date_gmt":"2015-07-25T00:01:00","guid":{"rendered":"https:\/\/blogs.technet.microsoft.com\/heyscriptingguy\/2015\/07\/25\/weekend-scripter-replace-one-powershell-function-with-another\/"},"modified":"2022-06-22T12:34:00","modified_gmt":"2022-06-22T19:34:00","slug":"weekend-scripter-replace-one-powershell-function-with-another","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/scripting\/weekend-scripter-replace-one-powershell-function-with-another\/","title":{"rendered":"Weekend Scripter: Replace One PowerShell Function with Another"},"content":{"rendered":"

Summary<\/b>: Ed Wilson, Microsoft Scripting Guy, talks about replacing one Windows PowerShell function with a different one.<\/span><\/p>\n

Microsoft Scripting Guy, Ed Wilson, is here. One of the problems with writing Windows PowerShell code every day is that you eventually…<\/p>\n

No, it\u2019s not what you think.<\/p>\n

I am often asked if I run out of ideas, and the answer is, “No, I don\u2019t.”<\/p>\n

There is so much I can do with Windows PowerShell that, in fact, a new version of Windows PowerShell will be out before I ever run out of ideas of what to do with the last version. No, the problem is not that I run out of ideas, but it is that I often forget what I have written. In fact, this week is a case in point.<\/p>\n

Code cleanup<\/h2>\n

I wrote a cool function that creates a Windows PowerShell transcript log file name from the date. In it, I replace invalid file-name characters. Here is the function:<\/p>\n

\n Function Get-TranscriptName\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0$invalidChars = [io.path]::GetInvalidFileNamechars()\n<\/p>\n

\n \u00a0$date = Get-Date -format s\n<\/p>\n

\n \u00a0 “{0}.{1}.{2}.txt” -f “PowerShell_Transcript”, $env:COMPUTERNAME,\n<\/p>\n

\n \u00a0 ($date.ToString() -replace “[$invalidChars]”,”-“) }\n<\/p>\n

There is absolutely nothing in the world wrong with it. It works fine (that is, if I don\u2019t start Windows PowerShell twice in the same second, which on my laptop is virtually impossible to do).<\/p>\n

The problem is that I have already written a cool Windows PowerShell function that will remove invalid characters from the file name. So THAT is why I knew about [io.path]::GetInvalidFileNameChars<\/strong>. I didn\u2019t even have to look it up\u2014I remembered it because I have used it before. Here is that function:<\/p>\n

\n Function Replace-InvalidFileCharacters\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0Param ($stringIn,\n<\/p>\n

\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 $replacementChar)\n<\/p>\n

\n \u00a0# Replace-InvalidFileCharacters “my?string”\n<\/p>\n

\n \u00a0# Replace-InvalidFileCharacters (get-date).tostring()\n<\/p>\n

\n \u00a0$stringIN -replace “[$( [System.IO.Path]::GetInvalidFileNameChars() )]”, $replacementChar\n<\/p>\n

\n }\n<\/p>\n

It is obvious, that the code is essentially the same, but it has the added advantage that I can use it for any string, not just for the date. So, I decided that I want to add this function to my Windows PowerShell profile and cleanup the Windows PowerShell transcript name function a bit. But how?<\/p>\n

How do I bring in this function and cleanup the other function, when the Get-TranscriptName<\/strong> function has the functionality embedded into a rather complex line of Windows PowerShell code?<\/p>\n

Add them to a blank page in the ISE<\/h2>\n

The answer is pretty simple:<\/p>\n

I open a new tab in the Windows PowerShell ISE, and I test it out. First I open my Windows PowerShell profile from the Windows PowerShell console by using my function Edit-Profile Windows PowerShell<\/a>.<\/p>\n

Then I add a new blank page to the Windows PowerShell ISE, and I copy the Get-TranscriptName<\/strong> and the Replace-InvalidFileCharacters<\/strong> functions to it. This is shown here:<\/p>\n

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

Reduce duplication<\/h2>\n

Now I need to look at what the Replace-InvalidFileCharacters<\/strong> function does and what I need to have in the Get-TranscriptName<\/strong> function. It is obvious that the key to both functions is the call to GetInvalidFileNameChars<\/strong> static method. So, I can comment out the first line in the **Get-TranscriptName **function:<\/p>\n

\n Function Get-TranscriptName\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0#$invalidChars = [io.path]::GetInvalidFileNamechars()\n<\/p>\n

\n \u00a0$date = Get-Date -format s\n<\/p>\n

\n \u00a0 “{0}.{1}.{2}.txt” -f “PowerShell_Transcript”, $env:COMPUTERNAME,\n<\/p>\n

\n \u00a0 ($date.ToString() -replace “[$invalidChars]”,”-“) }\n<\/p>\n

The next thing that the Replace-InvalidFileCharacters<\/strong> function does is call the \u2013Replace<\/strong> operator to replace the invalid characters with the character supplied when the function is called. So I can also replace that line in my Get-TranscriptName<\/strong> function:<\/p>\n

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

In the previous image, you can see that the two commands are essentially the same:<\/p>\n

\n -Replace (characters to replace), (character to replace with)\n<\/p>\n

Because the Replace-InvalidFileCharacters<\/strong> function performs the same thing as the code highlighted in the Get-TranscriptName<\/strong>, I can substitute the code in the Get-TranscriptName<\/strong> function with a call to the Replace-InvalidFileCharacters<\/strong> function.<\/p>\n

I need to first load the Replace-InvalidFileCharacters<\/strong> function into memory in my Windows PowerShell ISE so I can test it to make sure everything works properly.<\/p>\n

The other thing I need to realize is that the (Get-Date).tostring()<\/strong> portion in my Get-TranscriptFileName<\/strong> function will need to be supplied as input to the Replace-InvalidFileCharacters<\/strong> function. So, here is the replacement:<\/p>\n

\n Function Get-TranscriptName\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0$date = Get-Date -format s\n<\/p>\n

\n \u00a0 “{0}.{1}.{2}.txt” -f “PowerShell_Transcript”, $env:COMPUTERNAME,\n<\/p>\n

\n \u00a0 (Replace-InvalidFileCharacters -stringIn $date.ToString() -replacementChar “-“) }\n<\/p>\n

Now, in keeping with my tenant that I like to create aliases for my functions, I create a new alias for Replace-InvalidFileCharacters<\/strong> that will be easier to type. I decide to see if RIFC<\/strong> is taken. I test it with Get-Alias<\/strong>:<\/p>\n

\n PS C:\\> Get-Alias rifc\n<\/p>\n

\n Get-Alias : This command cannot find a matching alias because an alias with the name ‘rifc’ does not exist.\n<\/p>\n

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

\n + Get-Alias rifc\n<\/p>\n

\n + ~~~~~~~~~~~~~~\n<\/p>\n

\n \u00a0\u00a0\u00a0 + CategoryInfo\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : ObjectNotFound: (rifc:String) [Get-Alias], ItemNotFoundException\n<\/p>\n

\n \u00a0\u00a0\u00a0 + FullyQualifiedErrorId : ItemNotFoundException,Microsoft.PowerShell.Commands.GetAliasCommand\n<\/p>\n

It appears to be available, so I add this alias:<\/p>\n

\n Set-Alias -Name rifc -Value Replace-InvalidFileCharacters | out-null\n<\/p>\n

Then I copy the two functions to my Windows PowerShell profile after I replace the long command name. The complete profile is shown here:<\/p>\n

\n #——————————————————————————\n<\/p>\n

\n #\n<\/p>\n

\n # PowerShell console profile\n<\/p>\n

\n # ed wilson, msft\n<\/p>\n

\n #\n<\/p>\n

\n # NOTES: contains five types of things: aliases, functions, psdrives,\n<\/p>\n

\n # variables and commands.\n<\/p>\n

\n # version 1.1\n<\/p>\n

\n # 7\/20\/2015\n<\/p>\n

\n # HSG 7-23-2015\n<\/p>\n

\n #——————————————————————————\n<\/p>\n

\n #Aliases\n<\/p>\n

\n Set-Alias -Name ep -Value edit-profile | out-null\n<\/p>\n

\n Set-Alias -Name tch -Value Test-ConsoleHost | out-null\n<\/p>\n

\n Set-Alias -Name gfl -Value Get-ForwardLink | out-null\n<\/p>\n

\n Set-Alias -Name gwp -Value Get-WebPage | out-null\n<\/p>\n

\n Set-Alias -Name rifc -Value Replace-InvalidFileCharacters | out-null\n<\/p>\n

\n #Functions\n<\/p>\n

\n Function Edit-Profile\n<\/p>\n

\n { ISE $profile }\n<\/p>\n

\n Function Test-ConsoleHost\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0if(($host.Name -match ‘consolehost’)) {$true}\n<\/p>\n

\n \u00a0Else {$false}\u00a0\u00a0\n<\/p>\n

\n }\n<\/p>\n

\n Function Replace-InvalidFileCharacters\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0Param ($stringIn,\n<\/p>\n

\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 $replacementChar)\n<\/p>\n

\n \u00a0# Replace-InvalidFileCharacters “my?string”\n<\/p>\n

\n \u00a0# Replace-InvalidFileCharacters (get-date).tostring()\n<\/p>\n

\n \u00a0$stringIN -replace “[$( [System.IO.Path]::GetInvalidFileNameChars() )]”, $replacementChar\n<\/p>\n

\n }\n<\/p>\n

\n Function Get-TranscriptName\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0$date = Get-Date -format s\n<\/p>\n

\n \u00a0 “{0}.{1}.{2}.txt” -f “PowerShell_Transcript”, $env:COMPUTERNAME,\n<\/p>\n

\n \u00a0 (rifc -stringIn $date.ToString() -replacementChar “-“) }\n<\/p>\n

\n Function Get-WebPage\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0Param($url)\n<\/p>\n

\n \u00a0# Get-WebPage -url (Get-CmdletFwLink get-process)\n<\/p>\n

\n \u00a0(New-Object -ComObject shell.application).open($url)\n<\/p>\n

\n }\n<\/p>\n

\n Function Get-ForwardLink\n<\/p>\n

\n {\n<\/p>\n

\n \u00a0Param($cmdletName)\n<\/p>\n

\n \u00a0# Get-WebPage -url (Get-CmdletFwLink get-process)\n<\/p>\n

\n \u00a0(Get-Command $cmdletName).helpuri\n<\/p>\n

\n }\n<\/p>\n

\n #Variables\n<\/p>\n

\n New-Variable -Name doc -Value “$home\\documents”\n<\/p>\n

\n #PS_Drives\n<\/p>\n

\n New-PSDrive -Name Mod -Root ($env:PSModulePath -split ‘;’)[0] `\n<\/p>\n

\n \u00a0-PSProvider FileSystem | out-null\n<\/p>\n

\n #Commands\n<\/p>\n

\n Set-Location c:\\\n<\/p>\n

\n If(tch) {Start-Transcript -Path (Join-Path -Path `\n<\/p>\n

\n \u00a0$doc -ChildPath $(Get-TranscriptName))}\n<\/p>\n

On Monday, I’ll wrap up Profile Week, and I’ll be talking about adding variable descriptions to my profile. 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<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

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