1 /*
   2  * Copyright (c) 2014, 2017, 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 #descendants}, {@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.base/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 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 pid();
 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      * The {@link #parent} of a direct child process is the process.
 153      * Typically, a process that is {@link #isAlive not alive} has no children.
 154      * <p>
 155      * <em>Note that processes are created and terminate asynchronously.
 156      * There is no guarantee that a process is {@link #isAlive alive}.
 157      * </em>
 158      *
 159      * @return a sequential Stream of ProcessHandles for processes that are
 160      *         direct children of the process
 161      * @throws SecurityException if a security manager has been installed and
 162      *         it denies RuntimePermission("manageProcess")
 163      */
 164     Stream<ProcessHandle> children();
 165 
 166     /**
 167      * Returns a snapshot of the descendants of the process.
 168      * The descendants of a process are the children of the process
 169      * plus the descendants of those children, recursively.
 170      * Typically, a process that is {@link #isAlive not alive} has no children.
 171      * <p>
 172      * <em>Note that processes are created and terminate asynchronously.
 173      * There is no guarantee that a process is {@link #isAlive alive}.
 174      * </em>
 175      *
 176      * @return a sequential Stream of ProcessHandles for processes that
 177      *         are descendants of the process
 178      * @throws SecurityException if a security manager has been installed and
 179      *         it denies RuntimePermission("manageProcess")
 180      */
 181     Stream<ProcessHandle> descendants();
 182 
 183     /**
 184      * Returns a snapshot of all processes visible to the current process.
 185      * <p>
 186      * <em>Note that processes are created and terminate asynchronously. There
 187      * is no guarantee that a process in the stream is alive or that no other
 188      * processes may have been created since the inception of the snapshot.
 189      * </em>
 190      *
 191      * @return a Stream of ProcessHandles for all processes
 192      * @throws SecurityException if a security manager has been installed and
 193      *         it denies RuntimePermission("manageProcess")
 194      * @throws UnsupportedOperationException if the implementation
 195      *         does not support this operation
 196      */
 197     static Stream<ProcessHandle> allProcesses() {
 198         return ProcessHandleImpl.children(0);
 199     }
 200 
 201     /**
 202      * Returns a snapshot of information about the process.
 203      *
 204      * <p> A {@link ProcessHandle.Info} instance has accessor methods that return
 205      * information about the process if it is available.
 206      *
 207      * @return a snapshot of information about the process, always non-null
 208      */
 209     Info info();
 210 
 211     /**
 212      * Information snapshot about the process.
 213      * The attributes of a process vary by operating system and are not available
 214      * in all implementations.  Information about processes is limited
 215      * by the operating system privileges of the process making the request.
 216      * The return types are {@code Optional<T>} allowing explicit tests
 217      * and actions if the value is available.
 218      * @since 9
 219      */
 220     public interface Info {
 221         /**
 222          * Returns the executable pathname of the process.
 223          *
 224          * @return an {@code Optional<String>} of the executable pathname
 225          *         of the process
 226          */
 227         public Optional<String> command();
 228 
 229         /**
 230          * Returns the command line of the process.
 231          * <p>
 232          * If {@link #command command()} and  {@link #arguments arguments()} return
 233          * non-empty optionals, this is simply a convenience method which concatenates
 234          * the values of the two functions separated by spaces. Otherwise it will return a
 235          * best-effort, platform dependent representation of the command line.
 236          *
 237          * @apiNote Note that the returned executable pathname and the
 238          *          arguments may be truncated on some platforms due to system
 239          *          limitations.
 240          *          <p>
 241          *          The executable pathname may contain only the
 242          *          name of the executable without the full path information.
 243          *          It is undecideable whether white space separates different
 244          *          arguments or is part of a single argument.
 245          *
 246          * @return an {@code Optional<String>} of the command line
 247          *         of the process
 248          */
 249         public Optional<String> commandLine();
 250 
 251         /**
 252          * Returns an array of Strings of the arguments of the process.
 253          *
 254          * @apiNote On some platforms, native applications are free to change
 255          *          the arguments array after startup and this method may only
 256          *          show the changed values.
 257          *
 258          * @return an {@code Optional<String[]>} of the arguments of the process
 259          */
 260         public Optional<String[]> arguments();
 261 
 262         /**
 263          * Returns the start time of the process.
 264          *
 265          * @return an {@code Optional<Instant>} of the start time of the process
 266          */
 267         public Optional<Instant> startInstant();
 268 
 269         /**
 270          * Returns the total cputime accumulated of the process.
 271          *
 272          * @return an {@code Optional<Duration>} for the accumulated total cputime
 273          */
 274         public Optional<Duration> totalCpuDuration();
 275 
 276         /**
 277          * Return the user of the process.
 278          *
 279          * @return an {@code Optional<String>} for the user of the process
 280          */
 281         public Optional<String> user();
 282     }
 283 
 284     /**
 285      * Returns a {@code CompletableFuture<ProcessHandle>} for the termination
 286      * of the process.
 287      * The {@link java.util.concurrent.CompletableFuture} provides the ability
 288      * to trigger dependent functions or actions that may be run synchronously
 289      * or asynchronously upon process termination.
 290      * When the process has terminated the CompletableFuture is
 291      * {@link java.util.concurrent.CompletableFuture#complete completed} regardless
 292      * of the exit status of the process.
 293      * The {@code onExit} method can be called multiple times to invoke
 294      * independent actions when the process exits.
 295      * <p>
 296      * Calling {@code onExit().get()} waits for the process to terminate and returns
 297      * the ProcessHandle. The future can be used to check if the process is
 298      * {@link java.util.concurrent.CompletableFuture#isDone done} or to
 299      * {@link java.util.concurrent.Future#get() wait} for it to terminate.
 300      * {@link java.util.concurrent.Future#cancel(boolean) Cancelling}
 301      * the CompleteableFuture does not affect the Process.
 302      * @apiNote
 303      * The process may be observed to have terminated with {@link #isAlive}
 304      * before the ComputableFuture is completed and dependent actions are invoked.
 305      *
 306      * @return a new {@code CompletableFuture<ProcessHandle>} for the ProcessHandle
 307      *
 308      * @throws IllegalStateException if the process is the current process
 309      */
 310     CompletableFuture<ProcessHandle> onExit();
 311 
 312     /**
 313      * Returns {@code true} if the implementation of {@link #destroy}
 314      * normally terminates the process.
 315      * Returns {@code false} if the implementation of {@code destroy}
 316      * forcibly and immediately terminates the process.
 317      *
 318      * @return {@code true} if the implementation of {@link #destroy}
 319      *         normally terminates the process;
 320      *         otherwise, {@link #destroy} forcibly terminates the process
 321      */
 322     boolean supportsNormalTermination();
 323 
 324     /**
 325      * Requests the process to be killed.
 326      * Whether the process represented by this {@code ProcessHandle} object is
 327      * {@link #supportsNormalTermination normally terminated} or not is
 328      * implementation dependent.
 329      * Forcible process destruction is defined as the immediate termination of the
 330      * process, whereas normal termination allows the process to shut down cleanly.
 331      * If the process is not alive, no action is taken.
 332      * The operating system access controls may prevent the process
 333      * from being killed.
 334      * <p>
 335      * The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
 336      * {@link java.util.concurrent.CompletableFuture#complete completed}
 337      * when the process has terminated.
 338      * <p>
 339      * Note: The process may not terminate immediately.
 340      * For example, {@code isAlive()} may return true for a brief period
 341      * after {@code destroy()} is called.
 342      *
 343      * @return {@code true} if termination was successfully requested,
 344      *         otherwise {@code false}
 345      * @throws IllegalStateException if the process is the current process
 346      */
 347     boolean destroy();
 348 
 349     /**
 350      * Requests the process to be killed forcibly.
 351      * The process represented by this {@code ProcessHandle} object is
 352      * forcibly terminated.
 353      * Forcible process destruction is defined as the immediate termination of the
 354      * process, whereas normal termination allows the process to shut down cleanly.
 355      * If the process is not alive, no action is taken.
 356      * The operating system access controls may prevent the process
 357      * from being killed.
 358      * <p>
 359      * The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
 360      * {@link java.util.concurrent.CompletableFuture#complete completed}
 361      * when the process has terminated.
 362      * <p>
 363      * Note: The process may not terminate immediately.
 364      * For example, {@code isAlive()} may return true for a brief period
 365      * after {@code destroyForcibly()} is called.
 366      *
 367      * @return {@code true} if termination was successfully requested,
 368      *         otherwise {@code false}
 369      * @throws IllegalStateException if the process is the current process
 370      */
 371     boolean destroyForcibly();
 372 
 373     /**
 374      * Tests whether the process represented by this {@code ProcessHandle} is alive.
 375      * Process termination is implementation and operating system specific.
 376      * The process is considered alive as long as the PID is valid.
 377      *
 378      * @return {@code true} if the process represented by this
 379      *         {@code ProcessHandle} object has not yet terminated
 380      */
 381     boolean isAlive();
 382 
 383     /**
 384      * Returns a hash code value for this ProcessHandle.
 385      * The hashcode value follows the general contract for {@link Object#hashCode()}.
 386      * The value is a function of the {@link #pid pid()} value and
 387      * may be a function of additional information to uniquely identify the process.
 388      * If two ProcessHandles are equal according to the {@link #equals(Object) equals}
 389      * method, then calling the hashCode method on each of the two objects
 390      * must produce the same integer result.
 391      *
 392      * @return a hash code value for this object
 393      */
 394     @Override
 395     int hashCode();
 396 
 397     /**
 398      * Returns {@code true} if {@code other} object is non-null, is of the
 399      * same implementation, and represents the same system process;
 400      * otherwise it returns {@code false}.
 401      * @implNote
 402      * It is implementation specific whether ProcessHandles with the same PID
 403      * represent the same system process. ProcessHandle implementations
 404      * should contain additional information to uniquely identify the process.
 405      * For example, the start time of the process could be used
 406      * to determine if the PID has been re-used.
 407      * The implementation of {@code equals} should return {@code true} for two
 408      * ProcessHandles with the same PID unless there is information to
 409      * distinguish them.
 410      *
 411      * @param other another object
 412      * @return {@code true} if the {@code other} object is non-null,
 413      *         is of the same implementation class and represents
 414      *         the same system process; otherwise returns {@code false}
 415      */
 416     @Override
 417     boolean equals(Object other);
 418 
 419     /**
 420      * Compares this ProcessHandle with the specified ProcessHandle for order.
 421      * The order is not specified, but is consistent with {@link Object#equals},
 422      * which returns {@code true} if and only if two instances of ProcessHandle
 423      * are of the same implementation and represent the same system process.
 424      * Comparison is only supported among objects of same implementation.
 425      * If attempt is made to mutually compare two different implementations
 426      * of {@link ProcessHandle}s, {@link ClassCastException} is thrown.
 427      *
 428      * @param other the ProcessHandle to be compared
 429      * @return a negative integer, zero, or a positive integer as this object
 430      * is less than, equal to, or greater than the specified object.
 431      * @throws NullPointerException if the specified object is null
 432      * @throws ClassCastException if the specified object is not of same class
 433      *         as this object
 434      */
 435     @Override
 436     int compareTo(ProcessHandle other);
 437 
 438 }