12

Windows console:

  • Tool A can write binary data to a file, but has no option for telling it to use stdout.
  • Tool B can read binary data from stdin and process the info in it.

How can I get the output from A piped through B without using an intermediate file?

In other words: what is the Windows equivalent of /dev/stdout?

--jeroen

18

Windows does have an analogue for /dev/stdout, CON:

I imagine it still works, considering Microsoft's ongoing "legacy compatibility" program.

Ah.. found it. Microsoft Support gives a list of reserved names. You cannot name a file these names, and they have special meanings when used as inputs or outputs.

You MIGHT be able to use CON as an output device to send to stdout.

The list:

   Name    Function
   ----    --------
   CON     Keyboard and display
   PRN     System list device, usually a parallel port
   AUX     Auxiliary device, usually a serial port
   CLOCK$  System real-time clock
   NUL     Bit-bucket device
   A:-Z:   Drive letters
   COM1    First serial communications port
   LPT1    First parallel printer port
   LPT2    Second parallel printer port
   LPT3    Third parallel printer port
   COM2    Second serial communications port
   COM3    Third serial communications port
   COM4    Fourth serial communications port
  • 1
    Thanks, it really works (even in Win 8.1). We run build with Unity, in batch mode: Unity.exe -batchmode -projectPath C:\***\Application -logFile -buildWebPlayer web -quit. Without argument (filename) to -logFile - it must print output to console, but it doesn't. After adding CON (i.e. - -logFile CON) - it does :-) – setevoy Apr 15 '15 at 11:21
  • @setevoy this actually works for you with Unity on Windows? Can you give more details? Just causes Unity crash for me on Windows 7 and 10 using Unity.exe -batchmode -quit -projectPath "%cd%" -logFile CON -buildWindows64Player ".\GameBuild\Generic.exe". Command works fine without log file but I get no build output. – bbodenmiller Mar 11 '17 at 9:23
  • @bbodenmiller Sorry, but can't provide any more information - this project was finished almost 2 years ago :-) – setevoy Mar 11 '17 at 13:12
  • @bbodenmiller: Did you figure out how to accomplish this on windows 10? – 2manyprojects May 23 '17 at 12:23
  • 1
    @bbodenmiller It seems outputting the logfile to stdout is broken at the moment. See: issuetracker.unity3d.com/issues/… – Verox Sep 14 '17 at 14:25
4

Based on grawity's answer I've created an extended version which allows a process to be started directly without having to use multiple terminal windows.

General usage:

PipeServer [in|out] [process name] [argument 1] [argument 2] [...]

The string "{pipe}" is then replaced by the redirection path.

Real-World example:

PipeServer.exe in "C:\Keil\UV4\Uv4.exe" -b "C:\Project\Project.uvproj" -j0 -o "{pipe}"

This command-line can be inserted directly into, for example, Eclipse to redirect the build log of a certain external builder to StdOut.

This is probably the best it gets...

Link

4

Windows has no direct equivalent to /dev/stdout.


Here is my attempt at writing a C# program that creates a named pipe, which can be given to program A as a filename. Requires .NET v4.

(C# because the compiler comes with .NET runtime, and what computer doesn't have .NET these days?)

PipeServer.cs

using System;
using System.IO;
using System.IO.Pipes;

class PipeServer {
    static int Main(string[] args) {
        string usage = "Usage: PipeServer <name> <in | out>";
        if (args.Length != 2) {
            Console.WriteLine(usage);
            return 1;
        }

        string name = args[0];
        if (String.Compare(args[1], "in") == 0) {
            Pipe(name, PipeDirection.In);
        }
        else if (String.Compare(args[1], "out") == 0) {
            Pipe(name, PipeDirection.Out);
        }
        else {
            Console.WriteLine(usage);
            return 1;
        }
        return 0;
    }

    static void Pipe(string name, PipeDirection dir) {
        NamedPipeServerStream pipe = new NamedPipeServerStream(name, dir, 1);
        pipe.WaitForConnection();
        try {
            switch (dir) {
                case PipeDirection.In:
                    pipe.CopyTo(Console.OpenStandardOutput());
                    break;
                case PipeDirection.Out:
                    Console.OpenStandardInput().CopyTo(pipe);
                    break;
                default:
                    Console.WriteLine("unsupported direction {0}", dir);
                    return;
            }
        } catch (IOException e) {
            Console.WriteLine("error: {0}", e.Message);
        }
    }
}

Compile with:

csc PipeServer.cs /r:System.Core.dll

csc can be found in %SystemRoot%\Microsoft.NET\Framework64\<version>\csc.exe

For example, using .NET Client Profile v4.0.30319 on a 32-bit Windows XP:

"C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\csc.exe" PipeServer.cs /r:System.Core.dll

Run:

PipeServer foo in | programtwo

in window one, and:

programone \\.\pipe\foo

in window two.

  • +1 Now that is a cool solution! I will try that soon and let you know. Now first some Zzzzzzz :-) – Jeroen Wiert Pluimers Feb 3 '11 at 21:46
  • One more thought before doing Zzzz: what about closing the pipe? I'm going to think about what the best signalling mechanism is for programone to tell pipe, that it is done with \\.\pipe\foo – Jeroen Wiert Pluimers Feb 3 '11 at 21:55
  • @Jeroen: When programone is done outputting data, it will simply close the output file it was using. (From the client side, pipes work the same way as ordinary files.) When it does so, pipe.exe – more precisely, pipe.CopyTo(...) – will reach EOF and simply exit. – grawity Feb 3 '11 at 22:03
  • @Jeroen: Also, there's one thing I haven't figured out: when using the tool in the opposite (out) direction (copy stdin to pipe), it dies with "Broken pipe" error after the first 1 kB. Doesn't happen when copying a pipe to stdout (in), however, so it shouldn't affect your program. (As they say, patches welcome.) – grawity Feb 3 '11 at 22:13
  • thanks will try this later next week, something in the project came up with a higher prio (don't you love IT projects <g>) – Jeroen Wiert Pluimers Feb 4 '11 at 11:32

Your Answer

By clicking "Post Your Answer", you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.