The Android Open Source Project | b5de22c | 2012-04-01 00:00:00 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Licensed to the Apache Software Foundation (ASF) under one or more |
| 3 | * contributor license agreements. See the NOTICE file distributed with |
| 4 | * this work for additional information regarding copyright ownership. |
| 5 | * The ASF licenses this file to You under the Apache License, Version 2.0 |
| 6 | * (the "License"); you may not use this file except in compliance with |
| 7 | * the License. You may obtain a copy of the License at |
| 8 | * |
| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | * |
| 11 | * Unless required by applicable law or agreed to in writing, software |
| 12 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | * See the License for the specific language governing permissions and |
| 15 | * limitations under the License. |
| 16 | */ |
| 17 | |
| 18 | package java.lang; |
| 19 | |
| 20 | import java.io.InputStream; |
| 21 | import java.io.OutputStream; |
| 22 | |
| 23 | /** |
| 24 | * Represents an external process. Enables writing to, reading from, destroying, |
| 25 | * and waiting for the external process, as well as querying its exit value. Use |
| 26 | * {@link ProcessBuilder} to create processes. |
| 27 | * |
| 28 | * <p>The child process writes its output to two streams, {@code out} and |
| 29 | * {@code err}. These streams should be read by the parent process using {@link |
| 30 | * #getInputStream()} and {@link #getErrorStream()} respectively. If these |
| 31 | * streams are not read, the target process may block while it awaits buffer |
| 32 | * space. It isn't sufficient to read the streams in sequence; to avoid blocking |
| 33 | * each of the two streams must have its own reader thread. If you are not |
| 34 | * interested in differentiating the out and err streams, use {@link |
| 35 | * ProcessBuilder#redirectErrorStream(boolean) redirectErrorStream(true)} to |
| 36 | * merge the two streams. This simplifies your reading code and makes it easier |
| 37 | * to avoid blocking the target process. |
| 38 | * |
| 39 | * <p>Running processes hold resources. When a process is no longer used, the |
| 40 | * process should be closed by calling {@link #destroy}. This will kill the |
| 41 | * process and release the resources that it holds. |
| 42 | * |
| 43 | * <p>For example, to run {@code /system/bin/ping} to ping {@code android.com}: |
| 44 | * <pre> {@code |
| 45 | * Process process = new ProcessBuilder() |
| 46 | * .command("/system/bin/ping", "android.com") |
| 47 | * .redirectErrorStream(true) |
| 48 | * .start(); |
| 49 | * try { |
| 50 | * InputStream in = process.getInputStream(); |
| 51 | * OutputStream out = process.getOutputStream(); |
| 52 | * |
| 53 | * readStream(in); |
| 54 | * |
| 55 | * } finally { |
| 56 | * process.destroy(); |
| 57 | * } |
| 58 | * }</pre> |
| 59 | */ |
| 60 | public abstract class Process { |
| 61 | |
| 62 | /** |
| 63 | * Terminates this process and closes any associated streams. |
| 64 | */ |
| 65 | public abstract void destroy(); |
| 66 | |
| 67 | /** |
| 68 | * Returns the exit value of the native process represented by this object. |
| 69 | * It is available only when the native process has terminated. |
| 70 | * |
| 71 | * @return the exit value of this process. |
| 72 | * @throws IllegalThreadStateException |
| 73 | * if this process has not terminated. |
| 74 | */ |
| 75 | public abstract int exitValue(); |
| 76 | |
| 77 | /** |
| 78 | * Returns an input stream that is connected to the error stream |
| 79 | * <em>(stderr)</em> of the native process represented by this object. |
| 80 | * |
| 81 | * @return the input stream to read from the error stream associated with |
| 82 | * the native process. |
| 83 | */ |
| 84 | public abstract InputStream getErrorStream(); |
| 85 | |
| 86 | /** |
| 87 | * Returns an input stream that is connected to the standard output stream |
| 88 | * <em>(stdout)</em> of the native process represented by this object. |
| 89 | * |
| 90 | * @return the input stream to read from the output stream associated with |
| 91 | * the native process. |
| 92 | */ |
| 93 | public abstract InputStream getInputStream(); |
| 94 | |
| 95 | /** |
| 96 | * Returns an output stream that is connected to the standard input stream |
| 97 | * <em>(stdin)</em> of the native process represented by this object. |
| 98 | * |
| 99 | * @return the output stream to write to the input stream associated with |
| 100 | * the native process. |
| 101 | */ |
| 102 | public abstract OutputStream getOutputStream(); |
| 103 | |
| 104 | /** |
| 105 | * Causes the calling thread to wait for the native process associated with |
| 106 | * this object to finish executing. |
| 107 | * |
| 108 | * @return the exit value of the native process being waited on. |
| 109 | * @throws InterruptedException |
| 110 | * if the calling thread is interrupted. |
| 111 | */ |
| 112 | public abstract int waitFor() throws InterruptedException; |
| 113 | } |