Class UNIX_Process

  extended by java.lang.Process
      extended by PIRL.Utilities.UNIX_Process

public class UNIX_Process
extends Process

A UNIX_Process is an adapter for the UNIXProcess implementation of the abstract Process class that provides access to hidden information.

The API for the Java Process class, as of Java 1.6, has an unfortunate shortcoming: The user is unable to access the process identification (PID) of the executed process nor provide the timeout argument to the Object.wait method used by the waitFor method. Process is an abstract class that is implemented by a host OS dependent class - UNIXProcess for UNIX systems - which relies on JNI methods that make the necessary host process management system calls.

For the UNIXProcess class (as of Java 1.6) the PID value is held in the private "pid" variable. UNIX_Process provides an ID() method to get the PID value.

The ability to provide the timeout argument is a trivial modification of the waitFor method. UNIX_Process provides a waitFor(long) method that limits the wait for the process to exit to a timeout value.

An exited() method provides direct access to the running/exited flag for the process.

All Process API methods are simply passed to the underlying Process.

Bradford Castalia - UA/PIRL
See Also:

Field Summary
static String ID
          Class identification name with source code version and date.
Constructor Summary
UNIX_Process(Process process)
          Construct a UNIX_Process for a Process object on a UNIX system.
Method Summary
 void destroy()
 boolean exited()
          Test if the process has exited.
 int exitValue()
 InputStream getErrorStream()
 InputStream getInputStream()
 OutputStream getOutputStream()
 int ID()
          Get the Process ID that uniquely identifies the system process.
 int waitFor()
 int waitFor(long timeout)
          Wait for the process to exit up to a maximum timeout.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail


public static final String ID
Class identification name with source code version and date.

See Also:
Constant Field Values
Constructor Detail


public UNIX_Process(Process process)
             throws NoSuchFieldException,
Construct a UNIX_Process for a Process object on a UNIX system.

process - The Process object obtained from a ProcessBuilder's start method or a Runtime exec method.
NoSuchFieldException - If the process does not have one of the expected field variables. This will occur if the process is not implemented by a JFC UNIXProcess or the implementation has changed from what is expected.
SecurityException - If a JVM SecurityManager prevents access to the private field values of the process object.
See Also:
ProcessBuilder, Runtime
Method Detail


public OutputStream getOutputStream()
Specified by:
getOutputStream in class Process


public InputStream getInputStream()
Specified by:
getInputStream in class Process


public InputStream getErrorStream()
Specified by:
getErrorStream in class Process


public int waitFor()
            throws InterruptedException
Specified by:
waitFor in class Process


public int exitValue()
Specified by:
exitValue in class Process


public void destroy()
Specified by:
destroy in class Process


public int ID()
Get the Process ID that uniquely identifies the system process.

the integer ID used by the system to identify the process.


public int waitFor(long timeout)
            throws InterruptedException,
Wait for the process to exit up to a maximum timeout.

Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated or the timeout period has expired. This method returns immediately if the subprocess has already terminated. If the subprocess has not yet terminated, the calling thread will be blocked. If the subprocess exits while the thread is blocked the exit status of the subprocess will be returned. If the timeout period expires while the thread is blocked an IOException will be thrown.

timeout - The maximum amount of time, in milliseconds, to wait on subprocess exit. Wait forever if the value is <= 0 (the same as the waitFor() method}.
The exit value of the process.
InterruptedException - If the current thread is interrupted by another thread while it is waiting, then the wait is ended and an InterruptedException is thrown.
IOException - If the timeout occurred before the process exit occurred.


public boolean exited()
Test if the process has exited.

The running/exited flag will only be set true after the forked process has exited.

This method tests the value of the UNIXProcess flag. The Process API may be used to determine if the process has exited via the exitValue() method which will throw an IllegalThreadStateException if the process has not yet exited.

true if the process has exited; false if it is still running.


Copyright (C) \ 2003-2009 Bradford Castalia, University of Arizona