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/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.lang;

import java.io.InputStream;
import java.io.OutputStream;

/**
 * Represents an external process. Enables writing to, reading from, destroying,
 * and waiting for the external process, as well as querying its exit value. Use
 * {@link ProcessBuilder} to create processes.
 *
 * 

The child process writes its output to two streams, {@code out} and * {@code err}. These streams should be read by the parent process using {@link * #getInputStream()} and {@link #getErrorStream()} respectively. If these * streams are not read, the target process may block while it awaits buffer * space. It isn't sufficient to read the streams in sequence; to avoid blocking * each of the two streams must have its own reader thread. If you are not * interested in differentiating the out and err streams, use {@link * ProcessBuilder#redirectErrorStream(boolean) redirectErrorStream(true)} to * merge the two streams. This simplifies your reading code and makes it easier * to avoid blocking the target process. * *

Running processes hold resources. When a process is no longer used, the * process should be closed by calling {@link #destroy}. This will kill the * process and release the resources that it holds. * *

For example, to run {@code /system/bin/ping} to ping {@code android.com}: *

   {@code
 *   Process process = new ProcessBuilder()
 *       .command("/system/bin/ping", "android.com")
 *       .redirectErrorStream(true)
 *       .start();
 *   try {
 *     InputStream in = process.getInputStream();
 *     OutputStream out = process.getOutputStream();
 *
 *     readStream(in);
 *
 *   } finally {
 *     process.destroy();
 *   }
 * }
*/ public abstract class Process { /** * Terminates this process and closes any associated streams. */ public abstract void destroy(); /** * Returns the exit value of the native process represented by this object. * It is available only when the native process has terminated. * * @return the exit value of this process. * @throws IllegalThreadStateException * if this process has not terminated. */ public abstract int exitValue(); /** * Returns an input stream that is connected to the error stream * (stderr) of the native process represented by this object. * * @return the input stream to read from the error stream associated with * the native process. */ public abstract InputStream getErrorStream(); /** * Returns an input stream that is connected to the standard output stream * (stdout) of the native process represented by this object. * * @return the input stream to read from the output stream associated with * the native process. */ public abstract InputStream getInputStream(); /** * Returns an output stream that is connected to the standard input stream * (stdin) of the native process represented by this object. * * @return the output stream to write to the input stream associated with * the native process. */ public abstract OutputStream getOutputStream(); /** * Causes the calling thread to wait for the native process associated with * this object to finish executing. * * @return the exit value of the native process being waited on. * @throws InterruptedException * if the calling thread is interrupted. */ public abstract int waitFor() throws InterruptedException; }




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