Passing newline character to PowerShell via Cmd - powershell

Question

I'm trying to run a PowerShell script from Windows cmd.exe. The input to the PowerShell script is a string, which contains newline characters using PowerShell backtick escaping - i.e:
`r`n
For demonstration purposes, the input string is then written to the console, and also dumped to a file.
The issue I have is that when the script is run from cmd.exe using the syntax
powershell.exe script.ps1 "TEST`r`nTEST"
The newline characters in the string are not treated as newline, and are included literally in both the console output and the output text file.
TEST`r`nTEST
However, if I run this from a PowerShell environment, I get the expected result (i.e. the newline characters are parsed correctly, and a newline is inserted in the appropriate location).
TEST
TEST
Similarly, if I pass in \r\n instead of the escaped newline characters through Windows cmd.exe, and do a .replace in the PowerShell script
$date = $data.replace("\r\n","`r`n")
I get the expected output:
TEST
TEST
Is anyone able to shed some light on why this happens?
The test script is as follows:
param([string]$data) # data to send
Write-Host $data
[IO.File]::WriteAllText('d:\temp.txt', $data)
return 0
And the file is called from the command line as:
powershell.exe script.ps1 "TEST`r`nTEST"
The script is running on Windows Server 2012 R2, using PowerShell v4.0

Answer 1

tl;dr
Use -Command and pass the entire PowerShell command as a single string; e.g.:
C:\> powershell -NoProfile -Command "script.ps1 \"TEST`r`nTEST\""
TEST
TEST
Note how the internal " instances are escaped as \", which PowerShell requires when called from the outside (alternatively, for full robustness, use "^"" (sic) in Windows PowerShell and "" in PowerShell (Core) v6+).
In your specific case,
powershell -NoProfile -Command script.ps1 "TEST`r`nTEST" would have worked too, but generally that only works as intended if the string has no embedded spaces.
Given that -Command is the default up to PSv5.1, your command - as currently posted - should work as-is.
As of PowerShell v5.1, arguments passed to powershell.exe from the outside:
ARE subject to interpretation by PowerShell, including string interpolation, by default and when you use -Command (i.e., specifying neither -File nor -Command currently defaults to -Command).
Caveat: The default behavior will change in v6: -File will be the default then - see the relevant change on GitHub.
are NOT subject to interpretation if you use -File to invoke a script - (after potential interpretation by cmd.exe) PowerShell treats all arguments as literal strings.
Caveat: This behavior is currently being discussed with respect to v6, given that it is overtly problematic in at least one case: trying to pass Boolean values.
Optional reading: Why you should pass the entire PowerShell command as a single argument when using -Command:
When you use -Command with multiple arguments, PowerShell essentially assembles them into a single command line behind the scenes before executing it.
Any "..."-quoting around the individual arguments is lost in the process, which can have unexpected results; e.g.:
C:\> powershell -NoProfile -Command "& { $args.count }" "line 1`r`nline 2"
3 # !! "line 1`r`nline 2" was broken into 3 arguments
Given that the outer "..." quoting was removed in the process of parsing the command line, the actual command line that PowerShell ended up executing was:
C:\ PS> & { $args.Count } line 1`r`nline 2
3
To illustrate why, let's look at an equivalent command that uses explicit quoting:
C:\ PS> & { $args.Count } "line" "1`r`nline" "2"
In other words: After the enclosing " were removed, the resulting token was broken into multiple arguments by spaces, as usual.

Answer 2

The parameter will need to be reinterpreted as a PowerShell string. Will this get you down the road?
The reason your -replace did not work is that the original string actually contains a backtick. It needs to be escaped in the search string.
C:\src\t>type p1.ps1
Param([string]$s)
Write-Host $s
$p = Invoke-Expression `"$s`"
Write-Host $p
$p2 = $s -replace "``r``n","`r`n"
Write-Host $p2
C:\src\t>powershell -noprofile -file .\p1.ps1 "TEST`r`nTEST"
TEST`r`nTEST
TEST
TEST
TEST
TEST

Answer 3

Carriage return and Linefeed are bytes with values 13 and 10, you can't write them, you can't see them.
As a convenience, when writing PowerShell code, the language will let you write:
"`r`n"
in a double quoted string, and when processing PowerShell source code (and at no other time), it will read those and replace them with bytes value 13 and 10.
It is this line of code in the PowerShell tokenizer which does it.
There is nothing special about backtick-n to the cmd.exe interpreter, and nothing special about having it in a string - you can put it there in a single quoted string
'`n'
or replacing it in a string - except that you have to note when the replacement happens. e.g. in your comment:
For example, if you pass in 'r'n and then replace 'r'n with 'r'n, the 'r'n is still output literally
Because your code
-replace "`r`n"
becomes
-replace "[char]13[char]10"
and your string passed in from outside contains
`r`n
and they don't match. Backtick-n in a string isn't magic, strings are not all interpreted by the PowerShell engine as PowerShell code, nor are parameters, or anything. And it's only in that context - when you write your -replace code, that is when the swap for actual newline characters happens.