Replace()

https://ss64.com/ps/replace.html

Replace characters within a string.

Syntax
      .Replace(strOldChar, strNewChar)

Key
   strOldChar  The characters to find.

   strNewChar  The characters to replace them with.

Examples

Replace characters in a string:

PS C:\> "abcdef" -replace "dEf","xyz"

Replace characters in a variable:

PS C:\> $demo = "abcdef"
PS C:\> $demo.replace("dEf","xyz")
abcxyz

Multiple replacements can be chained together in one command:

PS C:\> "abcdef" -replace "dEf","xyz" -replace "cx","-"
ab-yz

Search and Replace characters in a file:

PS C:\> $oldfile = "C:\demo\sourcetext.txt"PS C:\> $newfile = "C:\demo\newfile.txt"

PS C:\> $text = (Get-Content -Path $oldfile -ReadCount 0) -join "`n"
PS C:\> $text -replace 'dEf', 'xyz' | Set-Content -Path $newfile

Search and Replace using a hash table:

 $text = 'Any old text string'
 
 $hash = @{}
 $hash.'old' = 'new'
 $hash.A = 'B'
 $hash.' ' = '_'

 Foreach ($key in $hash.Keys) {
    $text = $text.Replace($key, $hash.$key)
 }
 $text

#This technique can also be used to replace common unicode characters.

Rename file extensions from .log to .txt

PS C:\> dir *.log | rename-item $_ -newname { $_.Name -replace '\.log','.txt' }

Using single quotes around the search strings will ensure that all punctuation is ignored by PowerShell.

An alternative method to read an entire file as a single long text string is the .Net ::ReadAllText method:
$allTheText = [System.Io.File]::ReadAllText($filePath)

More complex replacements can be done by combining -match or -replace with a regular expression.