Unable to get output from Apache Commons Exec

Question

Although the titles are very similar, this questions is NOT a duplicate of Process output from apache-commons exec.

I am trying to get the output of a command by using apache-commons exec. Here is what I am doing

import org.apache.commons.exec.*;
import java.io.ByteArrayOutputStream;

public class Sample {


    private static void runCommand(String cmd) throws Exception {
        ByteArrayOutputStream stdout = new ByteArrayOutputStream();
        PumpStreamHandler psh = new PumpStreamHandler(stdout);
        CommandLine cl = CommandLine.parse(cmd);
        DefaultExecutor exec = new DefaultExecutor();
        exec.setStreamHandler(psh);
        exec.execute(cl);
        System.out.println(stdout.toString());
    }

    public static void main(String... args) throws Exception {

        String cmd1 = "python -c \"print(10)\"";
        String cmd2 = "python -c \"import datetime; print(datetime.datetime.now())\"";

        runCommand(cmd1); // prints 10
        runCommand(cmd2); // should print the current datetime, but does not!
    }
}

The problem is that runCommand(cmd2) does not print anything to the output. When I try running the command on terminal, it works fine.

I have tried this program with and without the IDE so I'm sure this has nothing to do with the IDE console.

Here's a screenshot

Here's a screenshot of the terminal

Python command running on the terminal

Woland · Answer 1 · 2017-10-25T20:11:12.130

1

It works fine on mine PC from IDEA. Try to recreate the project. Add more information about your environment. Try to put your python code into .py file and run it like "python test.py".

edited Oct 25 '17 at 20:11

answered Oct 25 '17 at 16:17

Woland

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Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackoverflow.com/rooms/157525/discussion-on-answer-by-woland-unable-to-get-output-from-apache-commons-exec). – Andy Oct 26 '17 at 01:01

score 0 · Accepted Answer · answered Oct 26 '17 at 05:55

A colleague was able to come up with a solution to this problem. Changing

CommandLine cl = CommandLine.parse(cmd);

to

CommandLine cl = new CommandLine("/bin/sh");
cl.addArguments("-c");
cl.addArguments("'" + cmd + "'", false);

solved the issue.

The complete code looks as follows:

import org.apache.commons.exec.*;
import java.io.ByteArrayOutputStream;

public class Sample {
    private static void runCommand(String cmd) throws Exception {
        ByteArrayOutputStream stdout = new ByteArrayOutputStream();
        PumpStreamHandler psh = new PumpStreamHandler(stdout);

        // CommandLine cl = CommandLine.parse(cmd);
        CommandLine cl = new CommandLine("/bin/sh");
        cl.addArguments("-c");
        cl.addArguments("'" + cmd + "'", false);

        DefaultExecutor exec = new DefaultExecutor();
        exec.setStreamHandler(psh);
        exec.execute(cl);
        System.out.println(stdout.toString());
    }

    public static void main(String[] args) throws Exception {
        String cmd1 =  "python -c \"print(10)\"";
        String cmd2 =  "python -c \"import datetime; print(datetime.datetime.now())\"";

        runCommand(cmd1); // prints 10
        runCommand(cmd2);
    }
}

Unable to get output from Apache Commons Exec

2 Answers2