processoutput4j

Simple Java library for capturing stdout/stderr of processes launched from within Java.

Maven

Add the following artifact to your dependencies of your pom.xml:

    <dependency>
      <groupId>com.github.fracpete</groupId>
      <artifactId>processoutput4j</artifactId>
      <version>0.0.14</version>
    </dependency>

Available schemes

The following schemes for capturing process output are available:

• CollectingProcessOutput - collects all the output and makes it available once the process has finished
• ConsoleOutputProcessOutput - simply outputs the process' output from stdout and stderr to the Java process' stdout and stderr as it occurrs rather than waiting till the process finishes.
• StreamingProcessOutput - requires an owner object that implements the StreamingProcessOwner interface, as it will receive the output collected from stdout/stderr for further processing in the owner.

Stopping

The AbstractProcessOutput class offers the destroy() method, which allows a currently running process to be killed off from another thread (the monitor methods are waiting for the process to finish).

Extending

Adding a new scheme for capturing the process output is quite simple. You basically need to implement two classes:

• a reader class, derived from AbstractProcessReader that does something with the data obtained from stdout and stderr of the process.
• an output class, derived from AbstractProcessOutput that instantiates the appropriate readers for stdout and stderr.

Examples

The following executes the process and outputs any data from stdout/stderr once the process has finished:

import com.github.fracpete.processoutput4j.output.ConsoleOutputProcessOutput;
...
String[] cmd = new String[]{"/bin/ls", "-la", "/some/where"};
ProcessBuilder builder = new ProcessBuilder();
builder.command(cmd);
new ConsoleOutputProcessOutput().monitor(builder);

The following executes the process and outputs any data from stdout/stderr once the process has finished:

import com.github.fracpete.processoutput4j.output.CollectingProcessOutput;
...
String[] cmd = new String[]{"/bin/ls", "-la", "/some/where"};
ProcessBuilder builder = new ProcessBuilder();
builder.command(cmd);
CollectingProcessOutput output = new CollectingProcessOutput();
output.monitor(builder);
System.out.println("exit code: " + output.getExitCode());
System.out.println(output.getStdOut());

The following executes the process and outputs any data from stdout/stderr as it occurs, as well as setting a maximum execution time of 10 seconds:

import com.github.fracpete.processoutput4j.output.CollectingProcessOutput;
...
String[] cmd = new String[]{"/usr/bin/find", "/"};
ProcessBuilder builder = new ProcessBuilder();
builder.command(cmd);
ConsoleOutputProcessOutput output = new ConsoleOutputProcessOutput();
output.setTimeOut(10);
output.monitor(builder);

You can use the hasTimedOut() method to check whether the process timed out.

If you want to process the output (stdout/stderr) from the process yourself, then you can use StreamingProcessOutput instead of ConsoleOutputProcessOutput. You only need to supply an object of a class implementing the StreamingProcessOwner interface. Below is an example that simply prefixes the output with either [OUT] or [ERR]:

import com.github.fracpete.processoutput4j.core.StreamingProcessOutputType;
import com.github.fracpete.processoutput4j.core.StreamingProcessOwner;
import com.github.fracpete.processoutput4j.output.StreamingProcessOutput;

public static class Output implements StreamingProcessOwner {
  public StreamingProcessOutputType getOutputType() {
    return StreamingProcessOutputType.BOTH;
  }
  public void processOutput(String line, boolean stdout) {
    System.out.println((stdout ? "[OUT] " : "[ERR] ") + line);
  }
}

...
String[] cmd = new String[]{"/usr/bin/find", "/etc"};
ProcessBuilder builder = new ProcessBuilder();
builder.command(cmd);
StreamingProcessOutput output = new StreamingProcessOutput(new Output());
output.monitor(builder);

Instead of implementing StreamingProcessOwner yourself, you can use one of the following implementations:

• com.github.fracpete.processoutput4j.core.impl.PrefixedStreamingProcessOwner

  Forwards the stdout/stderr output of the monitored process to this one's stdout, using either default prefixes for stdout/stderr or user-supplied ones (like the above example).

• com.github.fracpete.processoutput4j.core.impl.SimpleStreamingProcessOwner

  Forwards the stdout/stderr output of the monitored process to this one's stdout/stderr.