如何在 Java 中捕获所有 Bash 输出

Question

I already have Java code that can handle all the output from stdout and stderr, and that all works fine. It uses getInputStream() and getErrorStream();

If I enter a command like this in a Bash terminal:

export ANDROID_HOME=/usr/local/bin/android-sdk-linux;export PATH=${PATH}:/usr/local/bin/gradle-1.8/bin;cd /var/local/android/dev/GradleHelloWorld;gradle clean

It gets extra output like:

> Loading

>Loading Resolving dependencies ...

>Building

Until it gets the regular "end" output:

:clean UP-TO-DATE

BUILD SUCCESSFUL

Total time: 2 mins 37.424 secs

But after trying many different combinations of, the below, with and without the "-c":

processBuilder = new ProcessBuilder("bash", "-c", sCmd);

proc = rt.exec(new String[] {"/bin/bash", "-c", commandS});

I know those are pretty much the same, but you get the idea. It only shows the "end" result, and not any of the other output before it.

For Windows I can get all the output with no problem, using:

proc = rt.exec("cmd.exe");

and the command string.

I don't know that much about Bash, so is there any other options I can try, or a different Java statement I can use to try to capture all the output using Java?

Update:

I'm already doing this (most of the code):

while ( true )
{

    if ( error_is.available() > 0 ) // Check Error Stream..
    {
        iBytesRead = error_is.read(tempBuf, 0, iTmpLength);
        if ( iBytesRead == -1 )
        {
             break;
        }

        baos.write(tempBuf, 0, iBytesRead);
   }
   else if ( out_is.available() > 0 )   // Check Output Stream..
   {
        iBytesRead = out_is.read(tempBuf, 0, iTmpLength);
        if ( iBytesRead == -1 )
        {
            break;
        }

        baos.write(tempBuf, 0, iBytesRead);
   }
}

It works fine in Windows using cmd.exe so I know it works, and it gets everything, but for Linux users, I have to use Bash, and I'm not getting some of the output, so that's my question..

Answer 1

You can use InputStreamReader in conjunction with BufferedReader to get the output of the command:

    ProcessBuilder pb = new ProcessBuilder("your-command");
    Process p = pb.start();
    InputStreamReader isr = new InputStreamReader(p.getInputStream());
    BufferedReader br = new BufferedReader(isr);

    String lineRead;
    while ((lineRead = br.readLine()) != null) {
        LOGGER.info(lineRead);
    }
    int rc = p.waitFor();
    return rc; // successful return code should be zero!

Answer 2

I've been struggling with this too. After multiple readings of the source code for the unix implementation of Process at https://github.com/AdoptOpenJDK/openjdk-jdk11/blob/master/src/java.base/unix/classes/java/lang/ProcessImpl.java it seems that the standard redirects will always swallow to a ProcessBuilder.NullInputStream :

if (redirects[1] == Redirect.PIPE) {
                    std_fds[1] = -1;
}...

and

stdout = (fds[1] == -1 || forceNullOutputStream) ?
                         ProcessBuilder.NullInputStream.INSTANCE :
                         new ProcessPipeInputStream(fds[1]);

(The same code repeats for stdIn, stdOut and stdErr streams)

The only workaround I have found, which feels very clumsy is to use a temp File:

File stdOutTmp;  // create and destroy however you see fit
ProcessBuilder pb = ...;
pb.redirectOutput(ProcessBuilder.Redirect.to(stdOutTmp));
...

There are other static factory methods ( Redirect.appendTo(File) to append to an existing file rather than overwrite an existing file, and Redirect.from(File) for stdIn)