set OutputStream for a process

问题:

Here is a snipped code of my problem:

Process process = Runtime.getRuntime().exec(command);
    if (process.waitFor() != 0)
        throw new Exception("error");
    reader = 
        new BufferedReader(new InputStreamReader(process.getInputStream()));

The running process is producing a huge output. If i redirect the output to a file, the process terminates quicker then printing the output on screen (standard output). I do not wish to redirect the output to a file, due to low performance of the disk, filesystem permission, etc..

When process.waitFor() is executed, Java is being blocked until the process (callee) is terminated, and that can take a long time. So in order to bypass this issue, I would like to redirect the process' standard output to reader's stream input (last line at the code). i.e., the callee should produce an output to a stream linked with the reader, instead to print the output on screen.

Hope I was clear enough. I wonder how may I do that? Any assistance will be great.

回答1:

If you don't care about the output of the process, just redirect to the null device which is > /dev/null on Unix or > NUL on Windows. All the output will be discarded and you won't have to worry about file permissions, performance etc.

If you do care about the output, take a look at this post which shows you the right way of reading the stdout/stderr of a process using a StreamGobbler.

回答2:

You need to read the output before calling waitFor(). At the moment you are waiting for it to finish, which it can only do when it has finished producing output, which it can't do because you aren't reading the output, so its buffers are full and it is blocking.