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package java.lang;

import java.io.*;


The ProcessBuilder.start() and Runtime.exec methods create a native process and return an instance of a subclass of Process that can be used to control the process and obtain information about it. The class Process provides methods for performing input from the process, performing output to the process, waiting for the process to complete, checking the exit status of the process, and destroying (killing) the process. 
The methods that create processes may not work well for special processes on certain native platforms, such as native windowing processes, daemon processes, Win16/DOS processes on Microsoft Windows, or shell scripts. The created subprocess does not have its own terminal or console. All its standard I/O (i.e. stdin, stdout, stderr) operations will be redirected to the parent process through three streams (getOutputStream(), getInputStream(), getErrorStream()). The parent process uses these streams to feed input to and get output from the subprocess. Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, and even deadlock. 
The subprocess is not killed when there are no more references to the Process object, but rather the subprocess continues executing asynchronously. 
There is no requirement that a process represented by a 
Process object execute asynchronously or concurrently with respect to the Java process that owns the Process object. 
Author: unascribed
See Also:
Since:  JDK1.0
/**
 * The {@link ProcessBuilder#start()} and
 * {@link Runtime#exec(String[],String[],File) Runtime.exec}
 * methods create a native process and return an instance of a
 * subclass of {@code Process} that can be used to control the process
 * and obtain information about it.  The class {@code Process}
 * provides methods for performing input from the process, performing
 * output to the process, waiting for the process to complete,
 * checking the exit status of the process, and destroying (killing)
 * the process.
 *
 * <p>The methods that create processes may not work well for special
 * processes on certain native platforms, such as native windowing
 * processes, daemon processes, Win16/DOS processes on Microsoft
 * Windows, or shell scripts.  The created subprocess does not have
 * its own terminal or console.  All its standard I/O (i.e. stdin,
 * stdout, stderr) operations will be redirected to the parent process
 * through three streams
 * ({@link #getOutputStream()},
 * {@link #getInputStream()},
 * {@link #getErrorStream()}).
 * The parent process uses these streams to feed input to and get output
 * from the subprocess.  Because some native platforms only provide
 * limited buffer size for standard input and output streams, failure
 * to promptly write the input stream or read the output stream of
 * the subprocess may cause the subprocess to block, and even deadlock.
 *
 * <p>The subprocess is not killed when there are no more references to
 * the {@code Process} object, but rather the subprocess
 * continues executing asynchronously.
 *
 * <p>There is no requirement that a process represented by a {@code
 * Process} object execute asynchronously or concurrently with respect
 * to the Java process that owns the {@code Process} object.
 *
 * @author  unascribed
 * @see     ProcessBuilder
 * @since   JDK1.0
 */
public abstract class Process {
    
Returns the output stream connected to the normal input of the subprocess. Output to the stream is piped into the standard input stream of the process represented by this Process object. 
Implementation note: It is a good idea for the returned
output stream to be buffered.

Returns:the output stream connected to the normal input of the
        subprocess
/**
     * Returns the output stream connected to the normal input of the
     * subprocess.  Output to the stream is piped into the standard
     * input stream of the process represented by this {@code Process}
     * object.
     *
     * <p>Implementation note: It is a good idea for the returned
     * output stream to be buffered.
     *
     * @return the output stream connected to the normal input of the
     *         subprocess
     */
    abstract public OutputStream getOutputStream();

    
Returns the input stream connected to the normal output of the subprocess. The stream obtains data piped from the standard output stream of the process represented by this 
Process object. 
Implementation note: It is a good idea for the returned
input stream to be buffered.

See Also:
Returns:the input stream connected to the normal output of the
        subprocess
/**
     * Returns the input stream connected to the normal output of the
     * subprocess.  The stream obtains data piped from the standard
     * output stream of the process represented by this {@code
     * Process} object.
     *
     * <p>Implementation note: It is a good idea for the returned
     * input stream to be buffered.
     *
     * @return the input stream connected to the normal output of the
     *         subprocess
     * @see ProcessBuilder#redirectErrorStream()
     */
    abstract public InputStream getInputStream();

    
Returns the input stream connected to the error output stream of the subprocess. The stream obtains data piped from the error output stream of the process represented by this Process object. 
Implementation note: It is a good idea for the returned
input stream to be buffered.

See Also:
Returns:the input stream connected to the error output stream of
        the subprocess
/**
     * Returns the input stream connected to the error output stream of
     * the subprocess.  The stream obtains data piped from the error
     * output stream of the process represented by this {@code Process}
     * object.
     *
     * <p>Implementation note: It is a good idea for the returned
     * input stream to be buffered.
     *
     * @return the input stream connected to the error output stream of
     *         the subprocess
     * @see ProcessBuilder#redirectErrorStream()
     */
    abstract public InputStream getErrorStream();

    
Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated. This method returns immediately if the subprocess has already terminated. If the subprocess has not yet terminated, the calling thread will be blocked until the subprocess exits. 
Throws:
Returns:the exit value of the subprocess represented by this Process object. By convention, the value 0 indicates normal termination.
/**
     * Causes the current thread to wait, if necessary, until the
     * process represented by this {@code Process} object has
     * terminated.  This method returns immediately if the subprocess
     * has already terminated.  If the subprocess has not yet
     * terminated, the calling thread will be blocked until the
     * subprocess exits.
     *
     * @return the exit value of the subprocess represented by this
     *         {@code Process} object.  By convention, the value
     *         {@code 0} indicates normal termination.
     * @throws InterruptedException if the current thread is
     *         {@linkplain Thread#interrupt() interrupted} by another
     *         thread while it is waiting, then the wait is ended and
     *         an {@link InterruptedException} is thrown.
     */
    abstract public int waitFor() throws InterruptedException;

    
Returns the exit value for the subprocess.

Throws:
Returns:the exit value of the subprocess represented by this Process object. By convention, the value 0 indicates normal termination.
/**
     * Returns the exit value for the subprocess.
     *
     * @return the exit value of the subprocess represented by this
     *         {@code Process} object.  By convention, the value
     *         {@code 0} indicates normal termination.
     * @throws IllegalThreadStateException if the subprocess represented
     *         by this {@code Process} object has not yet terminated
     */
    abstract public int exitValue();

    
Kills the subprocess. The subprocess represented by this Process object is forcibly terminated. 
/**
     * Kills the subprocess. The subprocess represented by this
     * {@code Process} object is forcibly terminated.
     */
    abstract public void destroy();
}