How can I replace newlines using PowerShell?

If you want to remove all new line characters and replace them with some character (say comma) then you can use the following.

(Get-Content test.txt) -join ","

This works because Get-Content returns array of lines. You can see it as tokenize function available in many languages.

In my understanding, Get-Content eliminates ALL newlines/carriage returns when it rolls your text file through the pipeline. To do multiline regexes, you have to re-combine your string array into one giant string. I do something like:

$text = [string]::Join("`n", (Get-Content test.txt))
[regex]::Replace($text, "t`n", "ting`na ", "Singleline")

Clarification: small files only folks! Please don't try this on your 40 GB log file :)

With -Raw you should get what you expect

A CRLF is two characters, of course, the CR and the LF. However, `n consists of both. For example:

PS C:\> $x = "Hello
>> World"

PS C:\> $x
Hello
World
PS C:\> $x.contains("`n")
True
PS C:\> $x.contains("`r")
False
PS C:\> $x.replace("o`nW","o There`nThe W")
Hello There
The World
PS C:\>

I think you're running into problems with the `r. I was able to remove the `r from your example, use only `n, and it worked. Of course, I don't know exactly how you generated the original string so I don't know what's in there.