Powershell Replace – Special characters – Nginx

• Since you want to match across lines, you cannot use the line-by-line processing that Get-Content does by default. Use the -Raw switch to read the entire file at once, into a single, multi-line string.

• Since both your search string and the replacement string passed to the regex-based -replace operator contain metacharacters, you must escape them.

  • Note: If all you need is literal (verbatim) substring matching, including not needing to assert where the substring must match (start of the string, word boundary, …), using [string]::Replace() is the simpler option, however:

    • In Windows PowerShell [string]::Replace() is invariably, case-sensitive, in PowerShell (Core) 7+ it is by default, unlike PowerShell’s operators – see this answer for guidance on when to use -replace vs. [string]::Replace()

  • The search string must be escaped with [regex]::Escape(), so that the .NET regex engine, which the -replace operator invariably uses, treats it as a literal.

  • The substitution string must have any embedded $ characters escaped as $$, so that $ isn’t mistaken for the start of a capture-group reference.

  • For a comprehensive overview of how -replace works, see this answer.

# Escape the search string.
$reSearch = [regex]::Escape(@'
location ~* "^/(888888-localhost/client)(.*)$" {
            proxy_pass https://localhost:32583;
@')

# Escape the substitution string.
$substitution = @"
location ~* "^/(888888-localhost/client)(.*)$" {
            proxy_pass https://localhost:$proxy;
"@.Replace('$', '$$')

# ...
  ($_ | Get-Content -Raw) -replace $reSearch, $substitution |
    Set-Content -LiteralPath $_.FullName
# ...

Note the use of both verbatim and expandable here-strings to facilitate declaring the strings.

As for a potential simplification of your -replace operation:

• Abraham Zinala points out that ultimately you’re looking to only replace the port number in the matched substring, so you could use a positive look-behind assertion ((?<=...)), as shown in this simplified example:

  $proxy = 8080
  'a https://localhost:80; z' -replace '(?<=https://localhost:)d+', $proxy
  

  • Output is: a https://localhost:8080; z

Caveat re newlines:

• The above assumes that your script file uses the same newline format (Windows-format CRLF vs. Unix-format LF) as the input file.

• If you’re not sure, and you want to match either format, replace the n escape sequence in $reSearch with r?n ($reSearch = $reSearch.Replace('n', 'r?n') and possibly replace the literal newline in $substitution with `r`n or `n, as needed.