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/*
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* Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang;
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import java.time.Duration;
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import java.time.Instant;
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import java.util.Optional;
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import java.util.concurrent.CompletableFuture;
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import java.util.stream.Stream;
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/**
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* ProcessHandle identifies and provides control of native processes. Each
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* individual process can be monitored for liveness, list its children,
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* get information about the process or destroy it.
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* By comparison, {@link java.lang.Process Process} instances were started
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* by the current process and additionally provide access to the process
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* input, output, and error streams.
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* <p>
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* The native process ID is an identification number that the
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* operating system assigns to the process.
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* The range for process id values is dependent on the operating system.
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* For example, an embedded system might use a 16-bit value.
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* Status information about a process is retrieved from the native system
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* and may change asynchronously; processes may be created or terminate
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* spontaneously.
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* The time between when a process terminates and the process id
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* is reused for a new process is unpredictable.
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* Race conditions can exist between checking the status of a process and
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* acting upon it. When using ProcessHandles avoid assumptions
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* about the liveness or identity of the underlying process.
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* <p>
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* Each ProcessHandle identifies and allows control of a process in the native
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* system. ProcessHandles are returned from the factory methods {@link #current()},
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* {@link #of(long)},
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* {@link #children}, {@link #allChildren}, {@link #parent()} and
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* {@link #allProcesses()}.
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* <p>
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* The {@link Process} instances created by {@link ProcessBuilder} can be queried
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* for a ProcessHandle that provides information about the Process.
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* ProcessHandle references should not be freely distributed.
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*
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* <p>
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* A {@link java.util.concurrent.CompletableFuture} available from {@link #onExit}
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* can be used to wait for process termination, and possibly trigger dependent
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* actions.
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* <p>
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* The factory methods limit access to ProcessHandles using the
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* SecurityManager checking the {@link RuntimePermission RuntimePermission("manageProcess")}.
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* The ability to control processes is also restricted by the native system,
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* ProcessHandle provides no more access to, or control over, the native process
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* than would be allowed by a native application.
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* <p>
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* @implSpec
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* In the case where ProcessHandles cannot be supported then the factory
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* methods must consistently throw {@link java.lang.UnsupportedOperationException}.
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* The methods of this class throw {@link java.lang.UnsupportedOperationException}
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* if the operating system does not allow access to query or kill a process.
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*
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* @see Process
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* @since 1.9
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*/
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public interface ProcessHandle extends Comparable<ProcessHandle> {
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/**
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* Returns the native process ID of the process. The native process ID is an
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* identification number that the operating system assigns to the process.
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*
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* @return the native process ID of the process
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* @throws UnsupportedOperationException if the implementation
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* does not support this operation
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*/
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long getPid();
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/**
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* Returns an {@code Optional<ProcessHandle>} for an existing native process.
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*
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* @param pid a native process ID
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* @return an {@code Optional<ProcessHandle>} of the PID for the process;
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* the {@code Optional} is empty if the process does not exist
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* @throws SecurityException if a security manager has been installed and
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* it denies RuntimePermission("manageProcess")
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* @throws UnsupportedOperationException if the implementation
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* does not support this operation
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*/
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public static Optional<ProcessHandle> of(long pid) {
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return ProcessHandleImpl.get(pid);
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}
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/**
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* Returns a ProcessHandle for the current process. The ProcessHandle cannot be
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* used to destroy the current process, use {@link System#exit System.exit} instead.
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*
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* @return a ProcessHandle for the current process
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* @throws SecurityException if a security manager has been installed and
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* it denies RuntimePermission("manageProcess")
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* @throws UnsupportedOperationException if the implementation
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* does not support this operation
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*/
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public static ProcessHandle current() {
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return ProcessHandleImpl.current();
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}
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/**
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* Returns an {@code Optional<ProcessHandle>} for the parent process.
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* Note that Processes in a zombie state usually don't have a parent.
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*
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* @return an {@code Optional<ProcessHandle>} of the parent process;
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* the {@code Optional} is empty if the child process does not have a parent
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* or if the parent is not available, possibly due to operating system limitations
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* @throws SecurityException if a security manager has been installed and
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* it denies RuntimePermission("manageProcess")
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*/
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Optional<ProcessHandle> parent();
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/**
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* Returns a snapshot of the current direct children of the process.
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* A process that is {@link #isAlive not alive} has zero children.
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* <p>
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* <em>Note that processes are created and terminate asynchronously.
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* There is no guarantee that a process is {@link #isAlive alive}.
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* </em>
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*
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* @return a Stream of ProcessHandles for processes that are direct children
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* of the process
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* @throws SecurityException if a security manager has been installed and
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* it denies RuntimePermission("manageProcess")
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*/
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Stream<ProcessHandle> children();
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/**
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* Returns a snapshot of the current direct and indirect children of the process.
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* A process that is {@link #isAlive not alive} has zero children.
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* <p>
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* <em>Note that processes are created and terminate asynchronously.
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* There is no guarantee that a process is {@link #isAlive alive}.
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* </em>
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*
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* @return a Stream of ProcessHandles for processes that are direct and
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* indirect children of the process
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* @throws SecurityException if a security manager has been installed and
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* it denies RuntimePermission("manageProcess")
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*/
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Stream<ProcessHandle> allChildren();
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/**
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* Returns a snapshot of all processes visible to the current process.
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* <p>
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* <em>Note that processes are created and terminate asynchronously. There
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* is no guarantee that a process in the stream is alive or that no other
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* processes may have been created since the inception of the snapshot.
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* </em>
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*
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* @return a Stream of ProcessHandles for all processes
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* @throws SecurityException if a security manager has been installed and
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* it denies RuntimePermission("manageProcess")
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* @throws UnsupportedOperationException if the implementation
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* does not support this operation
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*/
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static Stream<ProcessHandle> allProcesses() {
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return ProcessHandleImpl.children(0);
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}
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/**
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* Returns a snapshot of information about the process.
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*
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* <p> An {@code Info} instance has various accessor methods that return
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* information about the process, if the process is alive and the
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* information is available.
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*
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* @return a snapshot of information about the process, always non-null
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*/
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Info info();
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/**
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* Information snapshot about the process.
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* The attributes of a process vary by operating system and are not available
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* in all implementations. Information about processes is limited
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* by the operating system privileges of the process making the request.
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* The return types are {@code Optional<T>} allowing explicit tests
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* and actions if the value is available.
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* @since 1.9
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*/
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public interface Info {
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/**
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* Returns the executable pathname of the process.
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*
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* @return an {@code Optional<String>} of the executable pathname
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* of the process
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*/
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public Optional<String> command();
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/**
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* Returns an array of Strings of the arguments of the process.
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*
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* @return an {@code Optional<String[]>} of the arguments of the process
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*/
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public Optional<String[]> arguments();
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/**
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* Returns the start time of the process.
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*
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* @return an {@code Optional<Instant>} of the start time of the process
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*/
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public Optional<Instant> startInstant();
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/**
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* Returns the total cputime accumulated of the process.
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*
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* @return an {@code Optional<Duration>} for the accumulated total cputime
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*/
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public Optional<Duration> totalCpuDuration();
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/**
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* Return the user of the process.
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*
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* @return an {@code Optional<String>} for the user of the process
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*/
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public Optional<String> user();
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}
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/**
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* Returns a {@code CompletableFuture<ProcessHandle>} for the termination
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* of the process.
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* The {@link java.util.concurrent.CompletableFuture} provides the ability
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* to trigger dependent functions or actions that may be run synchronously
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* or asynchronously upon process termination.
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* When the process terminates the CompletableFuture is
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* {@link java.util.concurrent.CompletableFuture#complete completed} regardless
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* of the exit status of the process.
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* The {@code onExit} method can be called multiple times to invoke
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* independent actions when the process exits.
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* <p>
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* Calling {@code onExit().get()} waits for the process to terminate and returns
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* the ProcessHandle. The future can be used to check if the process is
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* {@link java.util.concurrent.CompletableFuture#isDone done} or to
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* {@link java.util.concurrent.Future#get() wait} for it to terminate.
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* {@link java.util.concurrent.Future#cancel(boolean) Cancelling}
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* the CompleteableFuture does not affect the Process.
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* <p>
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* If the process is {@link #isAlive not alive} the {@link CompletableFuture}
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* returned has been {@link java.util.concurrent.CompletableFuture#complete completed}.
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*
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* @return a new {@code CompletableFuture<ProcessHandle>} for the ProcessHandle
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*
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* @throws IllegalStateException if the process is the current process
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*/
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CompletableFuture<ProcessHandle> onExit();
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/**
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* Returns {@code true} if the implementation of {@link #destroy}
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* normally terminates the process.
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* Returns {@code false} if the implementation of {@code destroy}
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* forcibly and immediately terminates the process.
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*
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* @return {@code true} if the implementation of {@link #destroy}
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* normally terminates the process;
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* otherwise, {@link #destroy} forcibly terminates the process
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*/
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boolean supportsNormalTermination();
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/**
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* Requests the process to be killed.
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* Whether the process represented by this {@code ProcessHandle} object is
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* {@link #supportsNormalTermination normally terminated} or not is
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* implementation dependent.
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* Forcible process destruction is defined as the immediate termination of the
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* process, whereas normal termination allows the process to shut down cleanly.
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* If the process is not alive, no action is taken.
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* The operating system access controls may prevent the process
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* from being killed.
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* <p>
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* The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
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* {@link java.util.concurrent.CompletableFuture#complete completed}
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* when the process has terminated.
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* <p>
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* Note: The process may not terminate immediately.
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* For example, {@code isAlive()} may return true for a brief period
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* after {@code destroy()} is called.
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*
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* @return {@code true} if termination was successfully requested,
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* otherwise {@code false}
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* @throws IllegalStateException if the process is the current process
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*/
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boolean destroy();
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/**
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* Requests the process to be killed forcibly.
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* The process represented by this {@code ProcessHandle} object is
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* forcibly terminated.
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* Forcible process destruction is defined as the immediate termination of the
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* process, whereas normal termination allows the process to shut down cleanly.
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* If the process is not alive, no action is taken.
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* The operating system access controls may prevent the process
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* from being killed.
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* <p>
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* The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
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* {@link java.util.concurrent.CompletableFuture#complete completed}
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* when the process has terminated.
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* <p>
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* Note: The process may not terminate immediately.
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* For example, {@code isAlive()} may return true for a brief period
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* after {@code destroyForcibly()} is called.
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*
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* @return {@code true} if termination was successfully requested,
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* otherwise {@code false}
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* @throws IllegalStateException if the process is the current process
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*/
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boolean destroyForcibly();
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/**
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* Tests whether the process represented by this {@code ProcessHandle} is alive.
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* Process termination is implementation and operating system specific.
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* The process is considered alive as long as the PID is valid.
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*
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* @return {@code true} if the process represented by this
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* {@code ProcessHandle} object has not yet terminated
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*/
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boolean isAlive();
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/**
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* Compares this ProcessHandle with the specified ProcessHandle for order.
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* The order is not specified, but is consistent with {@link Object#equals},
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* which returns {@code true} if and only if two instances of ProcessHandle
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* are of the same implementation and represent the same system process.
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* Comparison is only supported among objects of same implementation.
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* If attempt is made to mutually compare two different implementations
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* of {@link ProcessHandle}s, {@link ClassCastException} is thrown.
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*
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* @param other the ProcessHandle to be compared
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* @return a negative integer, zero, or a positive integer as this object
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* is less than, equal to, or greater than the specified object.
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* @throws NullPointerException if the specified object is null
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* @throws ClassCastException if the specified object is not of same class
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* as this object
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*/
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@Override
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int compareTo(ProcessHandle other);
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}
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