1 /* 2 * Copyright (c) 2014, 2015, 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 package java.lang; 26 27 import java.time.Duration; 28 import java.time.Instant; 29 import java.util.Optional; 30 import java.util.concurrent.CompletableFuture; 31 import java.util.stream.Stream; 32 33 /** 34 * ProcessHandle identifies and provides control of native processes. Each 35 * individual process can be monitored for liveness, list its children, 36 * get information about the process or destroy it. 37 * By comparison, {@link java.lang.Process Process} instances were started 38 * by the current process and additionally provide access to the process 39 * input, output, and error streams. 40 * <p> 41 * The native process ID is an identification number that the 42 * operating system assigns to the process. 43 * The range for process id values is dependent on the operating system. 44 * For example, an embedded system might use a 16-bit value. 45 * Status information about a process is retrieved from the native system 46 * and may change asynchronously; processes may be created or terminate 47 * spontaneously. 48 * The time between when a process terminates and the process id 49 * is reused for a new process is unpredictable. 50 * Race conditions can exist between checking the status of a process and 51 * acting upon it. When using ProcessHandles avoid assumptions 52 * about the liveness or identity of the underlying process. 53 * <p> 54 * Each ProcessHandle identifies and allows control of a process in the native 55 * system. ProcessHandles are returned from the factory methods {@link #current()}, 56 * {@link #of(long)}, 57 * {@link #children}, {@link #allChildren}, {@link #parent()} and 58 * {@link #allProcesses()}. 59 * <p> 60 * The {@link Process} instances created by {@link ProcessBuilder} can be queried 61 * for a ProcessHandle that provides information about the Process. 62 * ProcessHandle references should not be freely distributed. 63 * 64 * <p> 65 * A {@link java.util.concurrent.CompletableFuture} available from {@link #onExit} 66 * can be used to wait for process termination, and possibly trigger dependent 67 * actions. 68 * <p> 69 * The factory methods limit access to ProcessHandles using the 70 * SecurityManager checking the {@link RuntimePermission RuntimePermission("manageProcess")}. 71 * The ability to control processes is also restricted by the native system, 72 * ProcessHandle provides no more access to, or control over, the native process 73 * than would be allowed by a native application. 74 * 75 * @implSpec 76 * In the case where ProcessHandles cannot be supported then the factory 77 * methods must consistently throw {@link java.lang.UnsupportedOperationException}. 78 * The methods of this class throw {@link java.lang.UnsupportedOperationException} 79 * if the operating system does not allow access to query or kill a process. 80 * 81 * <p> 82 * The {@code ProcessHandle} static factory methods return instances that are 83 * <a href="{@docRoot}/java/lang/doc-files/ValueBased.html">value-based</a>, 84 * immutable and thread-safe. 85 * Use of identity-sensitive operations (including reference equality 86 * ({@code ==}), identity hash code, or synchronization) on these instances of 87 * {@code ProcessHandle} may have unpredictable results and should be avoided. 88 * Use {@link #equals(Object) equals} or 89 * {@link #compareTo(ProcessHandle) compareTo} methods to compare ProcessHandles. 90 * 91 * @see Process 92 * @since 1.9 93 */ 94 public interface ProcessHandle extends Comparable<ProcessHandle> { 95 96 /** 97 * Returns the native process ID of the process. The native process ID is an 98 * identification number that the operating system assigns to the process. 99 * The operating system may reuse the process ID after a process terminates. 100 * Use {@link #equals(Object) equals} or 101 * {@link #compareTo(ProcessHandle) compareTo} to compare ProcessHandles. 102 * 103 * @return the native process ID of the process 104 * @throws UnsupportedOperationException if the implementation 105 * does not support this operation 106 */ 107 long getPid(); 108 109 /** 110 * Returns an {@code Optional<ProcessHandle>} for an existing native process. 111 * 112 * @param pid a native process ID 113 * @return an {@code Optional<ProcessHandle>} of the PID for the process; 114 * the {@code Optional} is empty if the process does not exist 115 * @throws SecurityException if a security manager has been installed and 116 * it denies RuntimePermission("manageProcess") 117 * @throws UnsupportedOperationException if the implementation 118 * does not support this operation 119 */ 120 public static Optional<ProcessHandle> of(long pid) { 121 return ProcessHandleImpl.get(pid); 122 } 123 124 /** 125 * Returns a ProcessHandle for the current process. The ProcessHandle cannot be 126 * used to destroy the current process, use {@link System#exit System.exit} instead. 127 * 128 * @return a ProcessHandle for the current process 129 * @throws SecurityException if a security manager has been installed and 130 * it denies RuntimePermission("manageProcess") 131 * @throws UnsupportedOperationException if the implementation 132 * does not support this operation 133 */ 134 public static ProcessHandle current() { 135 return ProcessHandleImpl.current(); 136 } 137 138 /** 139 * Returns an {@code Optional<ProcessHandle>} for the parent process. 140 * Note that Processes in a zombie state usually don't have a parent. 141 * 142 * @return an {@code Optional<ProcessHandle>} of the parent process; 143 * the {@code Optional} is empty if the child process does not have a parent 144 * or if the parent is not available, possibly due to operating system limitations 145 * @throws SecurityException if a security manager has been installed and 146 * it denies RuntimePermission("manageProcess") 147 */ 148 Optional<ProcessHandle> parent(); 149 150 /** 151 * Returns a snapshot of the current direct children of the process. 152 * A process that is {@link #isAlive not alive} has zero children. 153 * <p> 154 * <em>Note that processes are created and terminate asynchronously. 155 * There is no guarantee that a process is {@link #isAlive alive}. 156 * </em> 157 * 158 * @return a Stream of ProcessHandles for processes that are direct children 159 * of the process 160 * @throws SecurityException if a security manager has been installed and 161 * it denies RuntimePermission("manageProcess") 162 */ 163 Stream<ProcessHandle> children(); 164 165 /** 166 * Returns a snapshot of the current direct and indirect children of the process. 167 * A process that is {@link #isAlive not alive} has zero children. 168 * <p> 169 * <em>Note that processes are created and terminate asynchronously. 170 * There is no guarantee that a process is {@link #isAlive alive}. 171 * </em> 172 * 173 * @return a Stream of ProcessHandles for processes that are direct and 174 * indirect children of the process 175 * @throws SecurityException if a security manager has been installed and 176 * it denies RuntimePermission("manageProcess") 177 */ 178 Stream<ProcessHandle> allChildren(); 179 180 /** 181 * Returns a snapshot of all processes visible to the current process. 182 * <p> 183 * <em>Note that processes are created and terminate asynchronously. There 184 * is no guarantee that a process in the stream is alive or that no other 185 * processes may have been created since the inception of the snapshot. 186 * </em> 187 * 188 * @return a Stream of ProcessHandles for all processes 189 * @throws SecurityException if a security manager has been installed and 190 * it denies RuntimePermission("manageProcess") 191 * @throws UnsupportedOperationException if the implementation 192 * does not support this operation 193 */ 194 static Stream<ProcessHandle> allProcesses() { 195 return ProcessHandleImpl.children(0); 196 } 197 198 /** 199 * Returns a snapshot of information about the process. 200 * 201 * <p> An {@code Info} instance has various accessor methods that return 202 * information about the process, if the process is alive and the 203 * information is available. 204 * 205 * @return a snapshot of information about the process, always non-null 206 */ 207 Info info(); 208 209 /** 210 * Information snapshot about the process. 211 * The attributes of a process vary by operating system and are not available 212 * in all implementations. Information about processes is limited 213 * by the operating system privileges of the process making the request. 214 * The return types are {@code Optional<T>} allowing explicit tests 215 * and actions if the value is available. 216 * @since 1.9 217 */ 218 public interface Info { 219 /** 220 * Returns the executable pathname of the process. 221 * 222 * @return an {@code Optional<String>} of the executable pathname 223 * of the process 224 */ 225 public Optional<String> command(); 226 227 /** 228 * Returns an array of Strings of the arguments of the process. 229 * 230 * @return an {@code Optional<String[]>} of the arguments of the process 231 */ 232 public Optional<String[]> arguments(); 233 234 /** 235 * Returns the start time of the process. 236 * 237 * @return an {@code Optional<Instant>} of the start time of the process 238 */ 239 public Optional<Instant> startInstant(); 240 241 /** 242 * Returns the total cputime accumulated of the process. 243 * 244 * @return an {@code Optional<Duration>} for the accumulated total cputime 245 */ 246 public Optional<Duration> totalCpuDuration(); 247 248 /** 249 * Return the user of the process. 250 * 251 * @return an {@code Optional<String>} for the user of the process 252 */ 253 public Optional<String> user(); 254 } 255 256 /** 257 * Returns a {@code CompletableFuture<ProcessHandle>} for the termination 258 * of the process. 259 * The {@link java.util.concurrent.CompletableFuture} provides the ability 260 * to trigger dependent functions or actions that may be run synchronously 261 * or asynchronously upon process termination. 262 * When the process terminates the CompletableFuture is 263 * {@link java.util.concurrent.CompletableFuture#complete completed} regardless 264 * of the exit status of the process. 265 * The {@code onExit} method can be called multiple times to invoke 266 * independent actions when the process exits. 267 * <p> 268 * Calling {@code onExit().get()} waits for the process to terminate and returns 269 * the ProcessHandle. The future can be used to check if the process is 270 * {@link java.util.concurrent.CompletableFuture#isDone done} or to 271 * {@link java.util.concurrent.Future#get() wait} for it to terminate. 272 * {@link java.util.concurrent.Future#cancel(boolean) Cancelling} 273 * the CompleteableFuture does not affect the Process. 274 * <p> 275 * If the process is {@link #isAlive not alive} the {@link CompletableFuture} 276 * returned has been {@link java.util.concurrent.CompletableFuture#complete completed}. 277 * 278 * @return a new {@code CompletableFuture<ProcessHandle>} for the ProcessHandle 279 * 280 * @throws IllegalStateException if the process is the current process 281 */ 282 CompletableFuture<ProcessHandle> onExit(); 283 284 /** 285 * Returns {@code true} if the implementation of {@link #destroy} 286 * normally terminates the process. 287 * Returns {@code false} if the implementation of {@code destroy} 288 * forcibly and immediately terminates the process. 289 * 290 * @return {@code true} if the implementation of {@link #destroy} 291 * normally terminates the process; 292 * otherwise, {@link #destroy} forcibly terminates the process 293 */ 294 boolean supportsNormalTermination(); 295 296 /** 297 * Requests the process to be killed. 298 * Whether the process represented by this {@code ProcessHandle} object is 299 * {@link #supportsNormalTermination normally terminated} or not is 300 * implementation dependent. 301 * Forcible process destruction is defined as the immediate termination of the 302 * process, whereas normal termination allows the process to shut down cleanly. 303 * If the process is not alive, no action is taken. 304 * The operating system access controls may prevent the process 305 * from being killed. 306 * <p> 307 * The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is 308 * {@link java.util.concurrent.CompletableFuture#complete completed} 309 * when the process has terminated. 310 * <p> 311 * Note: The process may not terminate immediately. 312 * For example, {@code isAlive()} may return true for a brief period 313 * after {@code destroy()} is called. 314 * 315 * @return {@code true} if termination was successfully requested, 316 * otherwise {@code false} 317 * @throws IllegalStateException if the process is the current process 318 */ 319 boolean destroy(); 320 321 /** 322 * Requests the process to be killed forcibly. 323 * The process represented by this {@code ProcessHandle} object is 324 * forcibly terminated. 325 * Forcible process destruction is defined as the immediate termination of the 326 * process, whereas normal termination allows the process to shut down cleanly. 327 * If the process is not alive, no action is taken. 328 * The operating system access controls may prevent the process 329 * from being killed. 330 * <p> 331 * The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is 332 * {@link java.util.concurrent.CompletableFuture#complete completed} 333 * when the process has terminated. 334 * <p> 335 * Note: The process may not terminate immediately. 336 * For example, {@code isAlive()} may return true for a brief period 337 * after {@code destroyForcibly()} is called. 338 * 339 * @return {@code true} if termination was successfully requested, 340 * otherwise {@code false} 341 * @throws IllegalStateException if the process is the current process 342 */ 343 boolean destroyForcibly(); 344 345 /** 346 * Tests whether the process represented by this {@code ProcessHandle} is alive. 347 * Process termination is implementation and operating system specific. 348 * The process is considered alive as long as the PID is valid. 349 * 350 * @return {@code true} if the process represented by this 351 * {@code ProcessHandle} object has not yet terminated 352 */ 353 boolean isAlive(); 354 355 /** 356 * Returns a hash code value for this ProcessHandle. 357 * The hashcode value follows the general contract for {@link Object#hashCode()}. 358 * The value is a function of the {@link #getPid getPid()} value and 359 * may be a function of additional information to uniquely identify the process. 360 * If two ProcessHandles are equal according to the {@link #equals(Object) equals} 361 * method, then calling the hashCode method on each of the two objects 362 * must produce the same integer result. 363 * 364 * @return a hash code value for this object 365 */ 366 @Override 367 int hashCode(); 368 369 /** 370 * Returns {@code true} if {@code other} object is non-null, is of the 371 * same implementation, and represents the same system process; 372 * otherwise it returns {@code false}. 373 * @implNote 374 * It is implementation specific whether ProcessHandles with the same PID 375 * represent the same system process. ProcessHandle implementations 376 * should contain additional information to uniquely identify the process. 377 * For example, the start time of the process could be used 378 * to determine if the PID has been re-used. 379 * The implementation of {@code equals} should return {@code true} for two 380 * ProcessHandles with the same PID unless there is information to 381 * distinguish them. 382 * 383 * @param other another object 384 * @return {@code true} if the {@code other} object is non-null, 385 * is of the same implementation class and represents 386 * the same system process; otherwise returns {@code false} 387 */ 388 @Override 389 boolean equals(Object other); 390 391 /** 392 * Compares this ProcessHandle with the specified ProcessHandle for order. 393 * The order is not specified, but is consistent with {@link Object#equals}, 394 * which returns {@code true} if and only if two instances of ProcessHandle 395 * are of the same implementation and represent the same system process. 396 * Comparison is only supported among objects of same implementation. 397 * If attempt is made to mutually compare two different implementations 398 * of {@link ProcessHandle}s, {@link ClassCastException} is thrown. 399 * 400 * @param other the ProcessHandle to be compared 401 * @return a negative integer, zero, or a positive integer as this object 402 * is less than, equal to, or greater than the specified object. 403 * @throws NullPointerException if the specified object is null 404 * @throws ClassCastException if the specified object is not of same class 405 * as this object 406 */ 407 @Override 408 int compareTo(ProcessHandle other); 409 410 }