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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package java.lang;
import java.io.*;
import java.util.concurrent.TimeUnit;
/**
* 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.
*
* <p>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
* {@link #getOutputStream()},
* {@link #getInputStream()}, and
* {@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, or even deadlock.
*
* <p>Where desired, <a href="ProcessBuilder.html#redirect-input">
* subprocess I/O can also be redirected</a>
* using methods of the {@link ProcessBuilder} class.
*
* <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.
*
* <p>As of 1.5, {@link ProcessBuilder#start()} is the preferred way
* to create a {@code Process}.
*
* @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 of the process represented by this {@code Process} object.
*
* <p>If the standard input of the subprocess has been redirected using
* {@link ProcessBuilder#redirectInput(Redirect)
* ProcessBuilder.redirectInput}
* then this method will return a
* <a href="ProcessBuilder.html#redirect-input">null output stream</a>.
*
* <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
*/
public abstract OutputStream getOutputStream();
/**
* 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 {@code Process} object.
*
* <p>If the standard output of the subprocess has been redirected using
* {@link ProcessBuilder#redirectOutput(Redirect)
* ProcessBuilder.redirectOutput}
* then this method will return a
* <a href="ProcessBuilder.html#redirect-output">null input stream</a>.
*
* <p>Otherwise, if the standard error of the subprocess has been
* redirected using
* {@link ProcessBuilder#redirectErrorStream(boolean)
* ProcessBuilder.redirectErrorStream}
* then the input stream returned by this method will receive the
* merged standard output and the standard error of the subprocess.
*
* <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
*/
public abstract InputStream getInputStream();
/**
* 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 {@code Process} object.
*
* <p>If the standard error of the subprocess has been redirected using
* {@link ProcessBuilder#redirectError(Redirect)
* ProcessBuilder.redirectError} or
* {@link ProcessBuilder#redirectErrorStream(boolean)
* ProcessBuilder.redirectErrorStream}
* then this method will return a
* <a href="ProcessBuilder.html#redirect-output">null input stream</a>.
*
* <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 of
* the subprocess
*/
public abstract InputStream getErrorStream();
/**
* 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.
*/
public abstract int waitFor() throws InterruptedException;
/**
* Causes the current thread to wait, if necessary, until the
* subprocess represented by this {@code Process} object has
* terminated, or the specified waiting time elapses.
*
* <p>If the subprocess has already terminated then this method returns
* immediately with the value {@code true}. If the process has not
* terminated and the timeout value is less than, or equal to, zero, then
* this method returns immediately with the value {@code false}.
*
* <p>The default implementation of this methods polls the {@code exitValue}
* to check if the process has terminated. Concrete implementations of this
* class are strongly encouraged to override this method with a more
* efficient implementation.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the {@code timeout} argument
* @return {@code true} if the subprocess has exited and {@code false} if
* the waiting time elapsed before the subprocess has exited.
* @throws InterruptedException if the current thread is interrupted
* while waiting.
* @throws NullPointerException if unit is null
* @since 1.8
*/
public boolean waitFor(long timeout, TimeUnit unit)
throws InterruptedException
{
long startTime = System.nanoTime();
long rem = unit.toNanos(timeout);
do {
try {
exitValue();
return true;
} catch(IllegalThreadStateException ex) {
if (rem > 0)
Thread.sleep(
Math.min(TimeUnit.NANOSECONDS.toMillis(rem) + 1, 100));
}
rem = unit.toNanos(timeout) - (System.nanoTime() - startTime);
} while (rem > 0);
return false;
}
/**
* 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
*/
public abstract int exitValue();
/**
* Kills the subprocess. Whether the subprocess represented by this
* {@code Process} object is forcibly terminated or not is
* implementation dependent.
*/
public abstract void destroy();
/**
* Kills the subprocess. The subprocess represented by this
* {@code Process} object is forcibly terminated.
*
* <p>The default implementation of this method invokes {@link #destroy}
* and so may not forcibly terminate the process. Concrete implementations
* of this class are strongly encouraged to override this method with a
* compliant implementation. Invoking this method on {@code Process}
* objects returned by {@link ProcessBuilder#start} and
* {@link Runtime#exec} will forcibly terminate the process.
*
* <p>Note: The subprocess may not terminate immediately.
* i.e. {@code isAlive()} may return true for a brief period
* after {@code destroyForcibly()} is called. This method
* may be chained to {@code waitFor()} if needed.
*
* @return the {@code Process} object representing the
* subprocess to be forcibly destroyed.
* @since 1.8
*/
public Process destroyForcibly() {
destroy();
return this;
}
/**
* Tests whether the subprocess represented by this {@code Process} is
* alive.
*
* @return {@code true} if the subprocess represented by this
* {@code Process} object has not yet terminated.
* @since 1.8
*/
public boolean isAlive() {
try {
exitValue();
return false;
} catch(IllegalThreadStateException e) {
return true;
}
}
}