java.lang

Class Process

java.lang.Object

java.lang.Process

public abstract class Process
extends Object

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.

By default, 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, where they can be accessed via the streams obtained using the methods getOutputStream(), getInputStream(), and 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, or even deadlock.

Where desired, subprocess I/O can also be redirected using methods of the ProcessBuilder class.

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.

As of 1.5, ProcessBuilder.start() is the preferred way to create a Process.

Since:

JDK1.0

Constructor Summary

Constructors

Constructor and Description
Process()

Method Summary

Methods

Modifier and Type	Method and Description
abstract void	destroy() Kills the subprocess.
abstract int	exitValue() Returns the exit value for the subprocess.
abstract InputStream	getErrorStream() Returns the input stream connected to the error output of the subprocess.
abstract InputStream	getInputStream() Returns the input stream connected to the normal output of the subprocess.
abstract OutputStream	getOutputStream() Returns the output stream connected to the normal input of the subprocess.
abstract int	waitFor() Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Process

public Process()

Method Detail

getOutputStream

public abstract OutputStream getOutputStream()

Returns the output stream connected to the normal input of the subprocess. Output to the stream is piped into the standard input of the process represented by this Process object.

If the standard input of the subprocess has been redirected using ProcessBuilder.redirectInput then this method will return a null output stream.

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

getInputStream

public abstract InputStream getInputStream()

Returns the input stream connected to the normal output of the subprocess. The stream obtains data piped from the standard output of the process represented by this Process object.

If the standard output of the subprocess has been redirected using ProcessBuilder.redirectOutput then this method will return a null input stream.

Otherwise, if the standard error of the subprocess has been redirected using ProcessBuilder.redirectErrorStream then the input stream returned by this method will receive the merged standard output and the standard error of the subprocess.

Implementation note: It is a good idea for the returned input stream to be buffered.

Returns:

the input stream connected to the normal output of the subprocess

getErrorStream

public abstract InputStream getErrorStream()

Returns the input stream connected to the error output of the subprocess. The stream obtains data piped from the error output of the process represented by this Process object.

If the standard error of the subprocess has been redirected using ProcessBuilder.redirectError or ProcessBuilder.redirectErrorStream then this method will return a null input stream.

Implementation note: It is a good idea for the returned input stream to be buffered.

Returns:

the input stream connected to the error output of the subprocess

waitFor

public abstract int waitFor()
                     throws InterruptedException

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.

Returns:

the exit value of the subprocess represented by this Process object. By convention, the value 0 indicates normal termination.

Throws:

InterruptedException - if the current thread is interrupted by another thread while it is waiting, then the wait is ended and an InterruptedException is thrown.

exitValue

public abstract int exitValue()

Returns the exit value for the subprocess.

Returns:

the exit value of the subprocess represented by this Process object. By convention, the value 0 indicates normal termination.

Throws:

IllegalThreadStateException - if the subprocess represented by this Process object has not yet terminated

destroy

public abstract void destroy()

Kills the subprocess. The subprocess represented by this Process object is forcibly terminated.