1 /*
2 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import java.io.*;
29
30 /**
31 * The {@link ProcessBuilder#start()} and
32 * {@link Runtime#exec(String[],String[],File) Runtime.exec}
33 * methods create a native process and return an instance of a
34 * subclass of {@code Process} that can be used to control the process
35 * and obtain information about it. The class {@code Process}
36 * provides methods for performing input from the process, performing
37 * output to the process, waiting for the process to complete,
38 * checking the exit status of the process, and destroying (killing)
39 * the process.
40 *
41 * <p>The methods that create processes may not work well for special
42 * processes on certain native platforms, such as native windowing
43 * processes, daemon processes, Win16/DOS processes on Microsoft
44 * Windows, or shell scripts.
45 *
46 * <p>By default, the created subprocess does not have its own terminal
47 * or console. All its standard I/O (i.e. stdin, stdout, stderr)
48 * operations will be redirected to the parent process, where they can
49 * be accessed via the streams obtained using the methods
50 * {@link #getOutputStream()},
51 * {@link #getInputStream()}, and
52 * {@link #getErrorStream()}.
53 * The parent process uses these streams to feed input to and get output
54 * from the subprocess. Because some native platforms only provide
55 * limited buffer size for standard input and output streams, failure
56 * to promptly write the input stream or read the output stream of
57 * the subprocess may cause the subprocess to block, or even deadlock.
58 *
59 * <p>Where desired, <a href="ProcessBuilder.html#redirect-input">
60 * subprocess I/O can also be redirected</a>
61 * using methods of the {@link ProcessBuilder} class.
62 *
63 * <p>The subprocess is not killed when there are no more references to
64 * the {@code Process} object, but rather the subprocess
65 * continues executing asynchronously.
66 *
67 * <p>There is no requirement that a process represented by a {@code
68 * Process} object execute asynchronously or concurrently with respect
69 * to the Java process that owns the {@code Process} object.
70 *
71 * <p>As of 1.5, {@link ProcessBuilder#start()} is the preferred way
72 * to create a {@code Process}.
73 *
74 * @since JDK1.0
75 */
76 public abstract class Process {
77 /**
78 * Returns the output stream connected to the normal input of the
79 * subprocess. Output to the stream is piped into the standard
80 * input of the process represented by this {@code Process} object.
81 *
82 * <p>If the standard input of the subprocess has been redirected using
83 * {@link ProcessBuilder#redirectInput(Redirect)
84 * ProcessBuilder.redirectInput}
85 * then this method will return a
86 * <a href="ProcessBuilder.html#redirect-input">null output stream</a>.
87 *
88 * <p>Implementation note: It is a good idea for the returned
89 * output stream to be buffered.
90 *
91 * @return the output stream connected to the normal input of the
92 * subprocess
93 */
94 abstract public OutputStream getOutputStream();
95
96 /**
97 * Returns the input stream connected to the normal output of the
98 * subprocess. The stream obtains data piped from the standard
99 * output of the process represented by this {@code Process} object.
100 *
101 * <p>If the standard output of the subprocess has been redirected using
102 * {@link ProcessBuilder#redirectOutput(Redirect)
103 * ProcessBuilder.redirectOutput}
104 * then this method will return a
105 * <a href="ProcessBuilder.html#redirect-output">null input stream</a>.
106 *
107 * <p>Otherwise, if the standard error of the subprocess has been
108 * redirected using
109 * {@link ProcessBuilder#redirectErrorStream(boolean)
110 * ProcessBuilder.redirectErrorStream}
111 * then the input stream returned by this method will receive the
112 * merged standard output and the standard error of the subprocess.
113 *
114 * <p>Implementation note: It is a good idea for the returned
115 * input stream to be buffered.
116 *
117 * @return the input stream connected to the normal output of the
118 * subprocess
119 */
120 abstract public InputStream getInputStream();
121
122 /**
123 * Returns the input stream connected to the error output of the
124 * subprocess. The stream obtains data piped from the error output
125 * of the process represented by this {@code Process} object.
126 *
127 * <p>If the standard error of the subprocess has been redirected using
128 * {@link ProcessBuilder#redirectError(Redirect)
129 * ProcessBuilder.redirectError} or
130 * {@link ProcessBuilder#redirectErrorStream(boolean)
131 * ProcessBuilder.redirectErrorStream}
132 * then this method will return a
133 * <a href="ProcessBuilder.html#redirect-output">null input stream</a>.
134 *
135 * <p>Implementation note: It is a good idea for the returned
136 * input stream to be buffered.
137 *
138 * @return the input stream connected to the error output of
139 * the subprocess
140 */
141 abstract public InputStream getErrorStream();
142
143 /**
144 * Causes the current thread to wait, if necessary, until the
145 * process represented by this {@code Process} object has
146 * terminated. This method returns immediately if the subprocess
147 * has already terminated. If the subprocess has not yet
148 * terminated, the calling thread will be blocked until the
149 * subprocess exits.
150 *
151 * @return the exit value of the subprocess represented by this
152 * {@code Process} object. By convention, the value
153 * {@code 0} indicates normal termination.
154 * @throws InterruptedException if the current thread is
155 * {@linkplain Thread#interrupt() interrupted} by another
156 * thread while it is waiting, then the wait is ended and
157 * an {@link InterruptedException} is thrown.
158 */
159 abstract public int waitFor() throws InterruptedException;
160
161 /**
162 * Returns the exit value for the subprocess.
163 *
164 * @return the exit value of the subprocess represented by this
165 * {@code Process} object. By convention, the value
166 * {@code 0} indicates normal termination.
167 * @throws IllegalThreadStateException if the subprocess represented
168 * by this {@code Process} object has not yet terminated
169 */
170 abstract public int exitValue();
171
172 /**
173 * Kills the subprocess. The subprocess represented by this
174 * {@code Process} object is forcibly terminated.
175 */
176 abstract public void destroy();
177 }