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I'm trying to pipe a string into a program's STDIN *without* any trailing linefeeds (unless that string itself actually ends in a linefeed). I tried googling around, but I only found people trying to print to the *console* without a trailing linefeed, in which case `Write-Host` takes a parameter `-NoNewLine`. However, to pipe it on to another program, I need `Write-Output` or similar which doesn't have such a parameter. Now it seems like `Write-Output` isn't even the problem:

Z:\> (Write-Output "abc").Length
3

But as soon as I pipe it to another program and read the string there, I get an additional linefeed. For instance, I tried this Ruby snippet:

Z:\> Write-Output "abc" | ruby -e "p ARGF.read"
"abc\n"

I checked that the actual string received is `abc\n`. The same happens in several other languages (at least C#, Java and Python), so I believe it's an issue with PowerShell, not the language doing the reading.

As a further test, I replaced `Write-Output` itself with another Ruby script:

Z:\> ruby -e "$> << 'abc'"
abcZ:\>

(That is, there is definitely no `\n` on the script's STDOUT.)

But again, when I pipe it into another script:

Z:\> ruby -e "$> << 'abc'" | ruby -e "p ARGF.read"
"abc\n"

I'm fairly convinced that it's the pipe which adds the linefeed. How do I avoid that? I actually want to be able to control whether the input ends in a linefeed or not (by including it in the input or omitting it).

(For reference, I also tested strings which already contain a trailing linefeed, and in that case the pipe *doesn't* add another one, so I guess it just ensures a trailing linefeed.)

I originally encountered this in PowerShell v3, but I'm now using v5 and still have the same issue.

Bruteforce approach: feed binary data to process' stdin. I've tested this code on the `cat.exe` from [UnixUtils][1] and it seems to do what you want:



# Text to send
$InputVar = "No Newline, No NewLine,`nNewLine, No NewLine,`nNewLine, No NewLine"

# Buffer & initial size of MemoryStream
$BufferSize = 4096

# Convert text to bytes and write to MemoryStream
[byte[]]$InputBytes = [Text.Encoding]::UTF8.GetBytes($InputVar)
$MemStream = New-Object -TypeName System.IO.MemoryStream -ArgumentList $BufferSize
$MemStream.Write($InputBytes, 0, $InputBytes.Length)
[Void]$MemStream.Seek(0, 'Begin')

# Setup stdin\stdout redirection for our process
$StartInfo = New-Object -TypeName System.Diagnostics.ProcessStartInfo -Property @{
FileName = 'MyLittle.exe'
UseShellExecute = $false
RedirectStandardInput = $true
}

# Create new process
$Process = New-Object -TypeName System.Diagnostics.Process

# Assign previously created StartInfo properties
$Process.StartInfo = $StartInfo
# Start process
[void]$Process.Start()

# Pipe data
$Buffer = New-Object -TypeName byte[] -ArgumentList $BufferSize
$StdinStream = $Process.StandardInput.BaseStream

try
{
do
{
$ReadCount = $MemStream.Read($Buffer, 0, $Buffer.Length)
$StdinStream.Write($Buffer, 0, $ReadCount)
$StdinStream.Flush()
}
while($ReadCount -gt 0)
}
catch
{
throw 'Houston, we have a problem!'
}
finally
{
# Close streams
$StdinStream.Close()
$MemStream.Close()
}

# Cleanup
'Process', 'StdinStream', 'MemStream' |
ForEach-Object {
(Get-Variable $_ -ValueOnly).Dispose()
Remove-Variable $_ -Force
}

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