Powershell: Replace only fist occurence of a line/string in entire file-CodePudding

I have following beggining of a Powershell script in which I would like to replace the values of variables for different enviroment.

$SomeVar1 = "C:\path\to\file\a"
$SomeVar1 = "C:\path\to\file\a" # Copy for test - Should not be rewriten
$SomeVar2 = "C:\path\to\file\b" 
# Note $SomeVar1 = "C:\path\to\file\a" - Should not be rewriten

When I run the rewrite script, the result should look like this:

$SomeVar1 = "F:\different\path\to\file\a"
$SomeVar1 = "C:\path\to\file\a" # Copy for test - Should not be rewrite
$SomeVar2 = "F:\different\path\to\file\b" 
# Note $SomeVar1 = "C:\path\to\file\a" - Should not be rewriten

Current script that does(n't) rewrite:

$arr = @(
   [PSCustomObject]@{Regex = '$SomeVar1 = "';  Replace = '$SomeVar1 = "F:\different\path\to\file\a"'}
   [PSCustomObject]@{Regex = '$SomeVar2 = "';  Replace = '$SomeVar1 = "F:\different\path\to\file\b"'}
)

for ($i = 0; $i -lt $arr.Length; $i  ) {

   $ArrRegex = [Regex]::Escape($arr[$i].Regex)
   $ArrReplace = $arr[$i].Replace
   
   # Get full line for replacement
   $Line = Get-Content $Workfile | Select-String $ArrRegex | Select-Object -First 1 -ExpandProperty Line

   # Rewrite part
   $Line = [Regex]::Escape($Line)
   $Content = Get-Content $Workfile
   $Content -replace "^$Line",$ArrReplace | Set-Content $Workfile
}

This replaces all the occurences in file on the start of the line (and I need only the 1st one) and doest not replace the one in Note which is okay.

Then I found this Powershell: Replace last occurence of a line in a file which does the exact oposite of what I need, only rewrites the last occurence of the string and it does it in the Note aswell and I would somehow like to change it to do the opposite - 1st occurence, line begining (Wont target the Note)

Code in my case looks like this:

# Rewrite part
$Line = [Regex]::Escape($Line)
$Content = Get-Content $Workfile -Raw
$Line = "(?s)(.*)$Line"
$ArrReplace = "`$1$ArrReplace"
$Content -replace $Line,$ArrReplace | Set-Content $Workfile

Do you have any recommendations on how to archive my goal, or is there a more sothisticated way to replace variables for powershell scripts like this?

Thanks in advance.

CodePudding user response：

You could possibly use flag variables like below to only do the first replacement for each of your regex patterns.

$Altered = Get-Content -Path $Workfile |
    Foreach-Object {
        if(-not $a) { #If replacement hasn't been done, replace
            $_ = $_ -replace 'YOUR_REGEX1','YOUR_REPLACEMENT1'
            if($_ -match 'YOUR_REPLACEMENT1') { $a = 'replacement done' } #Set Flag
        }
        if(-not $b) { #If replacement hasn't been done, replace
            $_ = $_ -replace 'YOUR_REGEX2','YOUR_REPLACEMENT2'
            if($_ -match 'YOUR_REPLACEMENT2') { $b = 'replacement done' } #Set Flag
        }
        $_ # Pipe back to $Altered
    } 
$Altered | Set-Content -Path $WorkFile

CodePudding user response：

Just reverse the RegEx, if that is what you are after:

Clear-Host
@'
abc
abc
abc
'@ -replace '^(.*?)\babc\b', '$1HelloWorld'

# Results
<#
HelloWorld
abc
abc
#>