/*
* 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.
*
* <p>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.
*
* <p>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.
*
* <p>For example, to run {@code /system/bin/ping} to ping {@code android.com}:
* <pre> {@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();
* }
* }</pre>
*/
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
* <em>(stderr)</em> 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
* <em>(stdout)</em> 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
* <em>(stdin)</em> 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;
}