Powershell Script to replace characters in path strings errors out due to "(" or ")"

Question

I have written a Powershell script that receives N number of characters that have to be replaced by another given character from a user. For example, the user wants to replace (, ), and -. The user enters the characters that have to be replaced through this loop:

#Declare array for special characters to replace
$replaceChars = @( )

#Instruct the user about entering characters to replace
Write-Host
Write-Host "Please enter what you would like to replace in your names. This can contain one or more characters. Example: (2) or ^ or _" -ForegroundColor Cyan
Write-Host "Enter -1 to end your input and continue." -ForegroundColor Cyan

#Get values until sentinal is passed
$input = "" #input from user declared to blank

#loop for special characters
while($input -ne -1) {

    #get the input from the user
    $input = Read-Host -Prompt "Enter what you would like to replace (-1 to finish)"

    #if the input isn't sentinal, put it in the replaceChars array
    if($replaceChars.Length -gt 0 -and $input -eq -1) {
        Write-Host
        Write-Host "Your entries have been stored." -ForegroundColor Green
    } #end-if
    elseif($replaceChars.Length -eq 0 -and $input -eq -1) {
        Write-Host
        Write-Host "ERROR: You must enter at least one character to continue." -ForegroundColor Red
        $input = $NULL
    }
    elseif($input -eq '') {
    Write-Host
    Write-Host "Invalid entry. Entry cannot be blank, please enter a value." -ForegroundColor Red
    }#end-elseif
    elseif($input.IndexOfAny([System.IO.Path]::GetInvalidFileNameChars()) -ge 0) {
        Write-Host
        Write-Host "Invalid entry. File names cannot contain / \ : * ? `" < > |" -ForegroundColor Red
    }#end-elseif
    else {
        $replaceChars += $input
    } #end-else

}#end-while

The user then enters the replacement character through this code:

#Get the char to replace to
Write-Host
Write-Host "Please enter what you want to replace the selected characters with. Leave blank and hit enter to delete the old characters." -ForegroundColor Cyan
$newChar = Read-Host -Prompt "Please enter new character(s)"
while($newChar.IndexOfAny([System.IO.Path]::GetInvalidFileNameChars()) -ge 0) {
    Write-Host
    Write-Host "The entry is invalid for file names. File names cannot contain / \ : * ? `" < > |" -ForegroundColor Red
    $newChar = Read-Host -Prompt "Please enter new character(s)"
}
Write-Host
Write-Host "New character has been stored" -ForegroundColor Green

I am then processing the entries with this:

#Iterate through each character 
foreach($char in $replaceChars) {
    if($type -eq 1) {
        gci -File -Path "$path" | Where-Object { $_.Name -match $char } | ForEach-Object { $_ | rename-item  -NewName $_.Name.Replace($char, $newChar) }
    } elseif ($type -eq 2) { #end-if
        gci -Directory -Path "$path" | Where-Object { $_.Name -match $char } | ForEach-Object { $_ | rename-item  -NewName $_.Name.Replace($char, $newChar) }
    } else { #end-elseif 
        gci -Path "$path" | Where-Object { $_.Name -match $char } | ForEach-Object { $_ | rename-item  -NewName $_.Name.Replace($char, $newChar) }
    }#end-else
} #end-foreach

THE ERROR: If a user enters something like ( or ), then the last part of the script fails out with the following error code:

parsing "(" - Not enough )'s.
At <path to script>:109 char:50
+ ... gci -File -Path "$path" | Where-Object { $_.Name -match $char } | For ...
+                                              ~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [], ArgumentException
    + FullyQualifiedErrorId : System.ArgumentException

MY SOLUTIONS: I have attempted to use [regex]::Escape() to escape the $char and $newChar variables to fix the parentheses error. I have also attempted to resolve this by enclosing the variables with single and double quotes; however, this prevents the actual character replacement from occuring. I understand the parentheses/special characters is what is causing the issue, and I need to escape those somehow; however, the [regex]::Escape() solution breaks the character matching and ends up not replacing any of the user's entered characters.

MY QUESTION: How can I successfully escape the $char and $newChar variables in the GCI cmdlet and still replace special characters like ( or )

gci -Path "$path" | Where-Object { $_.Name -match $char } | ForEach-Object { $_ | rename-item  -NewName $_.Name.Replace($char, $newChar) }

Once you have this script under control doing what you want it to do I recommend going over to CodeReview.SE to have the experts there give you some suggestions on how to improve your script. — Matt, Oct 20 '17 at 19:33
Well don't I feel noobtastic... I've never visited CodeReview.SE, looks like I have a new site to catch up on if I get any downtime. Thanks for the pointer Matt! — TheMadTechnician, Oct 20 '17 at 19:44
@TheMadTechnician We need more PowerShellers there. If I keep answering question I am never going to learn anything. — Matt, Oct 20 '17 at 19:48
@Matt Thank you for the recommendation. I will certainly be looking at that. — Andrew, Oct 20 '17 at 20:45
@Andrew please don't add you answer in the question add it as a separate answer see [tour] — Petter Friberg, Oct 20 '17 at 21:07

Matt · Accepted Answer · 2017-10-20T19:47:42.977

1

How did you try to implement [regex]::Escape() exactly? If you tried to save $char before hand as escaped I see your problem. Since your .replace() method does not use regex. This should leave you with a few options

Just update the where clause to use the escape character just for the comparison. That was $char is not permanently changed. This would be a good idea regardless if you plan on using -match and not supporting regex characters.
```
gci -Path "$path" | Where-Object { $_.Name -match [regex]::Escape($char) } | ...
```

Save $char as escaped and use the -replace operator which also supports regex.

gci -Path "$path" | Where-Object { $_.Name -match $char } | 
    ForEach-Object { $_ | rename-item  -NewName ($_.Name -replace $char, $newChar))

Not use regex operators at all

gci -Path "$path" | Where-Object { $_.Name.Contains($char) } | ...

Couple points of review

Don't use the name $input. It is a reserved variable name. See about_automatic_variables
Since you are working with the fullname of the file I would caution that you could also accidentally edit the extension of the file. The basename property might be useful to you in that case.
As TheMadTechnician points out you can avoid the regex/non-regex issue by filtering at the Get-ChildItem level instead.
```
gci -Path "$path" -Filter "*$char*" | Rename-Item  -NewName {$_.Name.Replace($char, $newChar)}
```

edited Oct 20 '17 at 19:47

answered Oct 20 '17 at 19:32

Matt

45,022
8
78
119

Better yet, make the FileSystem provider filter results rather than getting all results and making PowerShell filter things. `gci -Path $path -Filter "*$char*"|%{renaming stuff here}` – TheMadTechnician Oct 20 '17 at 19:36
I'm working on it. There are several points that need to be addressed here. I was trying to suggest what to do with fewer changes as possible. There are some lessons to be learned here I didn't want to skip. – Matt Oct 20 '17 at 19:37
@Matt Thank you for your response! I attempted to implement `[regex]::Escape()` in the same fashion as you in your first example. This resulted in the characters not being found and no getting replaced. – Andrew Oct 20 '17 at 20:26
@Matt I have successfully implemented the script by following your third suggestion. I've also fixed the `$input` var and am altering the basename instead of the name. Here is the solution: `gci -Path "$path" | Where-Object { $_.Basename.Contains($char) } | ForEach-Object { $_ | rename-item -NewName ($_.Basename.Replace($char, $newChar) + $_.extension) }` – Andrew Oct 20 '17 at 21:01

score 0 · Answer 2 · answered Oct 23 '17 at 14:30

THE SOLUTION: I have implemented the suggestions by @Matt and solved the errors with the following:

#Iterate through each character 
foreach($char in $replaceChars) {
    if($type -eq 1) {
        gci -File -Path "$path" | Where-Object { $_.Basename.Contains($char) } | ForEach-Object { $_ | rename-item -NewName ($_.Basename.Replace($char, $newChar) + $_.extension) }
    } elseif ($type -eq 2) { #end-if
        gci -Directory -Path "$path" | Where-Object { $_.Basename.Contains($char) } | ForEach-Object { $_ | rename-item -NewName ($_.Basename.Replace($char, $newChar) + $_.extension) }
    } else { #end-elseif 
        gci -Path "$path" | Where-Object { $_.Basename.Contains($char) } | ForEach-Object { $_ | rename-item -NewName ($_.Basename.Replace($char, $newChar) + $_.extension) }
    }#end-else
} #end-foreach

Powershell Script to replace characters in path strings errors out due to "(" or ")"

2 Answers2