Question

I am trying to decrypt using gpg.exe --passphrase-file my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg (without –batch and –yes option). I am also providing the encryption command if anyone cares to use it for testing gpg.exe --passphrase-file ..\BE\src\my.passphrase --symmetric --output MTR241_20111124.htm.gpg MTR241_20111124.htm.

There are two cases.
case 1: MTR241_20111124.htm file does not exist in the output dir. Both command prompt and captured output stream of exec gives same output.

C:\Eclipse\workspace2\sync_inbox>gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
Reading passphrase from file descriptor 3
gpg: CAST5 encrypted data
gpg: encrypted with 1 passphrase
gpg: WARNING: message was not integrity protected

The same messags gets printed by java exec and command prompt.

C:\Eclipse\workspace2\sync_inbox>gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
inp>gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
gpg: CAST5 encrypted data
gpg: encrypted with 1 passphrase
gpg: WARNING: message was not integrity protected

So far good enough

Case2: When the output file already exists as expected in command prompt it asked if I want to replace.

C:\Eclipse\workspace2\sync_inbox>gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
Reading passphrase from file descriptor 3
gpg: CAST5 encrypted data
gpg: encrypted with 1 passphrase
File `MTR241_20111124.htm' exists. Overwrite? (y/N) y
gpg: WARNING: message was not integrity protected

But this output is from java program which hangs after this first line. It does not print any line on console. If I enter ‘y’ in console, it does not accept the input and process. It simply hangs. I have to manually kill the process taskkill /F /IM gpg.exe only then the java console program accepts more commands and process.

C:\Eclipse\workspace2\sync_inbox>gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
inp>gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
gpg.exe  --passphrase-file ..\BE\src\my.passphrase --decrypt --output MTR241_20111124.htm MTR241_20111124.htm.gpg
    --hangs here-- 

The normal interactive commands of course works, say for ex:

F:\eclipse\workspace\HTMLProcessor\BEQuery>copy hello.txt world.txt
inp>copy hello.txt world.txt
copy hello.txt world.txt
Overwrite world.txt? (Yes/No/All): y
inp>y
y
        1 file(s) copied.

So here is my question why does it fail to capture output stream of gpg only when it asks for the prompt whether to replace the existing output file.

I already tried Runtime.exec(), ProcessBuilder, Plexus-Utils, ExpectJ, Ant to run this gpg.exe inside the java program all of them are showing the same result fails to capture output stream of the process in that special case. I even tried to write a .bat file to run the gpg --decrypt but even in that also it fails to capture output stream in above special case.

I think it matters, the origin of gpg.exe. Well I got it in portable git distribution, in the bin folder gpg.exe is available.

My question became really long and boring, but still for those who like to point out errors java code

package com.ycs.ezlink.scheduler.cmd;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import org.apache.log4j.Logger;

public class CmdRunner {
    private static Logger logger = Logger.getLogger(CmdRunner.class);

    static class StreamGobbler extends Thread
    {
        InputStream is;
        String type;

        StreamGobbler(InputStream is, String type)
        {
            this.is = is;
            this.type = type;
        }

        public void run() {
            try {
                System.out.println("in run!");
                    System.out.println(type);
                    final byte[] buffer = new byte[1];
                    for (int length = 0; (length = is.read(buffer)) != -1;) {
                        System.out.write(buffer, 0, length);
                    }
                } catch (IOException ioe) {
                    ioe.printStackTrace();
                }
        }
    }

    public static int process(String cmd){
        int exitVal = 0; 
        try {
            Runtime rt = Runtime.getRuntime();
             Process proc = rt.exec(cmd);
             // any error message?
             StreamGobbler errorGobbler = new 
                 StreamGobbler(proc.getErrorStream(), "ERROR");            

             // any output?
             StreamGobbler outputGobbler = new 
                 StreamGobbler(proc.getInputStream(), "OUTPUT");

             // kick them off
             errorGobbler.start();
             outputGobbler.start();

             // any error???
             System.out.println("Waiting for cmd process to complete " );
            exitVal = proc.waitFor();
             System.out.println("ExitValue: " + exitVal);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }    
        return exitVal;
    }

    public static void main(String[] a) throws IOException, InterruptedException, TimeoutException, ExpectJException {
        String gzipCmd = "gpg.exe  --passphrase-file C:/Eclipse/workspace2/BE/src/my.passphrase --decrypt --output C:/Eclipse/workspace2/sync_inbox/MTR241_20111124.htm C:/Eclipse/workspace2/sync_inbox/MTR241_20111124.htm.gpg";  
        //CmdRunner.process(gzipCmd); ///--fails
        //ProcessBuilder pb = new ProcessBuilder("gpg", "--passphrase-file", "C:/Eclipse/workspace2/BE/src/my.passphrase",
        "--decrypt","--output","C:/Eclipse/workspace2/sync_inbox/MTR241_20111124.htm",
        "C:/Eclipse/workspace2/sync_inbox/MTR241_20111124.htm.gpg"); ///--fails
        ProcessBuilder pb = new ProcessBuilder ("cmd");
        pb.redirectErrorStream(true);
        Process process = pb.start();
        OutputStream stdin = process.getOutputStream ();
        InputStream stderr = process.getErrorStream ();
        InputStream stdout = process.getInputStream ();
         StreamGobbler errorGobbler = new StreamGobbler(stderr, "ERROR");            
         errorGobbler.start();
         StreamGobbler stdoutGobbler = new StreamGobbler(stdout, "DEBUG");            
         stdoutGobbler.start();

         BufferedReader scan = new BufferedReader(new InputStreamReader(System.in));
         String line;
         while ((line = scan.readLine())!= null) {
                String input = line;
                System.out.println("inp>"+input);
                if (input.trim().equals("exit")) {
                    stdin.write("exit\r\n".getBytes()); 
                    stdin.flush();
                    break;
                } else {
                     stdin.write((input+"\r\n").getBytes());
                     stdin.flush();
                }
            }
         System.out.println("exited..");
        int returnCode  = process.waitFor();
        System.out.println(returnCode);
    }
}

One last word if I use the gpg --batch option, it no more prompts for the y/N input, so then it runs smoothly. But I am just curious to know, why would there be this problem. Although I have a feeling that gpg.exe was originally written for Unix/Linux like platform, so there might be some input output file redirection, but I would like to know more on the root cause of it, so that next time I know what to look for.

Answer 1

The output that you see in the terminal is a merged result from the standard output stream, standard error stream and console. You can capture standard output and standard error stream. But you cannot capture console. This is why gpg intentionally uses console directly, to prevent you from capturing. Why they do this is debatable.

Bottom line: you will not be able to capture Input or Output Stream of a program that deals directly with the console.