using Runtime.exec() in Java

Question

What do you have to do in Java to get the Runtime.exec() to run a program that is on the path? I'm trying to run gpsbabel which I have put into the path (/usr/local/bin).

public class GpxLib {

    public static void main(String[] args) {
     try
     {
      Runtime r = Runtime.getRuntime();
      Process p = r.exec("gpsbabel -i garmin -f usb: -o gpx -F -");
      InputStream is = p.getInputStream();
      BufferedReader br = new BufferedReader(new InputStreamReader(is));
      while (true)
      {
       String s = br.readLine();
       if (s == null)
        break;
       System.out.println(s);
      }
      br.readLine();
     } catch (IOException e) {
      e.printStackTrace(System.err);
     }
    }
}

Answer 1

Whatever you do, you must read this. No one should use Runtime.exec() without having read it.

Answer 2

It will inherit the path from the Java process. So whatever environment the Java process has, the spawned process will have as well. Here's how to check the environment:

Map<String, String> env = System.getenv();
for (String envName : env.keySet()) {
     System.out.format("%s=%s%n", envName, env.get(envName));
}

Have you set the PATH and exported it ? If you don't export it, then it's not available to subprocesses.

Additionally, you must consume stdout and stderr concurrently, to prevent blocking. Otherwise stuff will work in some circumstances, then your spawned process will output a different quantity of data and everything will grind to a halt.

See this answer for more details.

Answer 3

I added a call to System.out.println(System.getenv("PATH")); which only prints out

/usr/bin:/bin:/usr/sbin:/sbin

so for some reason /usr/local/bin doesn't show up. Looks like this is a MacOSX question or an Eclipse question, not a Java question. edit: asked this question on superuser instead.