Program output is different when executed through Powershell remote session

Question

I'm developing a Windows Console Application, using Visual Studio 2010, which prints progress percentage on screen such that the last number gets overwritten with the current number. I'm using carriage return to achieve this like so:

std::wcout
    << "[Running: "
    << std::setw(3)
    << std::setprecision(3)
    << percent
    << "%]"
    << '\r'
;

When I execute this program through PowerShell on a remote host using PSSesion:

Enter-PSSession WWW.XXX.YYY.ZZZ -credential <UserName>
[WWW.XXX.YYY.ZZZ]: PS C:\> .\test.exe

it behaves differently compared to when its executed locally either in PowerShell or in cmd.exe. I face following three problems:

1) The console output of the program is different, in that, instead of overwriting [Running xx%] its printing in the next line like so:

[Running  1%]
[Running  2%]
[Running  3%]
[Running  4%]
...

This is similar to what happens when output of a program is redirected to a file (lone carriage returns or newlines are replaced with carriage returns+newlines combinations).

2) The output doesn't shows up as and when the program writes something to cout. It comes at once at the end of execution. Does powershell caches the output of remote program and sends to the caller only once? If there is significant time difference between two lines (line meaning all the output between two newlines) then the first line gets printed as if it waits for some time for another newline and if received, it again goes to waiting state, if not received within certain time period (~500ms), it sends the output till last newline (and not all the accumulated output) to the caller. As can be seen from my code, there is no newline resulting in all the [Running xx%] being printed at once at the end.

3) At certain point in the program I need user's confirmation, but cin.fail() returns true in remote execution. So, is there any way to take user input in such an execution environment? Or is there any way to detect that the program is being executed remotely through Powershell (eg. some env variable)?

Any help related to any point will be greatly appreciated. :)

@Solaflex : In the hope that there might be some c or c++ library api that can control this behaviour. — anni
– anni, Commented May 9, 2013 at 15:07

x0n · Accepted Answer · 2013-05-10 14:24:58Z

1

With respect to 1), the WinRM protocol for PowerShell Remoting is really just an input/output stream for commands and their serialized output. It has no terminal emulation capabilities, so when you run things remotely, their output is fed back sequentially one line at a time. If you used SSH or Telnet to a remote shell of powershell.exe, you would likely see what you expect.

As for 2), the default output buffermode appears to be "Block" so this would explain the behaviour you're seeing. You can change this with the New-PSSessionOption cmdlet to create a configuration for a session created by New-PSSession that can be passed to the -Session parameter on remoting aware cmdlets. The option is OutputBufferingMode. If you set it to None, you should get the desired behaviour.

# default output buffering mode is "none" for default options
$s = new-pssession localhost -sessionoption (new-pssessionoption)
enter-pssession $s

For 3), ~~you should be able to accept input interactively IIRC.~~ Looks like interactive stuff doesn't work right - I may have completely misremembered this.

edited May 10, 2013 at 14:24

answered May 9, 2013 at 15:57

x0n

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3 Comments

anni Over a year ago

For 1) If the output is simply fed back, how are '\r' getting replaced by '\r\n' sequence? For 2) Is there any way to turn it off or is it possible to flush the output from within the program? 3) As I said, cin stream is in an invalid state. Do you know how to handle this?

x0n Over a year ago

For 1), it's probably an artifact of the xml serialization/deserialization process. For 2) and 3), I'll try to get back to you later with POC.

anni Over a year ago

I tried New-PSSessionOption but the result is still the same. From the description of OutputBufferingMode, it seems like it defines the behaviour in case of disconnected session and not the running sessions.

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