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Android example source code file (Process.java)

This example Android source code file (Process.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, bufferedwriter, i/o, illegalargumentexception, internet, io, ioexception, localsocket, net, network, object, process, securityexception, signal_kill, starting, string, util, vm, zygote, zygotestartfailedex

The Process.java Android example source code

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.os;

import android.net.LocalSocketAddress;
import android.net.LocalSocket;
import android.util.Log;
import dalvik.system.Zygote;

import java.io.BufferedWriter;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.ArrayList;

/*package*/ class ZygoteStartFailedEx extends Exception {
    /**
     * Something prevented the zygote process startup from happening normally
     */

    ZygoteStartFailedEx() {};
    ZygoteStartFailedEx(String s) {super(s);}
    ZygoteStartFailedEx(Throwable cause) {super(cause);}
}

/**
 * Tools for managing OS processes.
 */
public class Process {
    private static final String LOG_TAG = "Process";

    private static final String ZYGOTE_SOCKET = "zygote";

    /**
     * Name of a process for running the platform's media services.
     * {@hide}
     */
    public static final String ANDROID_SHARED_MEDIA = "com.android.process.media";

    /**
     * Name of the process that Google content providers can share.
     * {@hide}
     */
    public static final String GOOGLE_SHARED_APP_CONTENT = "com.google.process.content";

    /**
     * Defines the UID/GID under which system code runs.
     */
    public static final int SYSTEM_UID = 1000;

    /**
     * Defines the UID/GID under which the telephony code runs.
     */
    public static final int PHONE_UID = 1001;

    /**
     * Defines the UID/GID for the user shell.
     * @hide
     */
    public static final int SHELL_UID = 2000;

    /**
     * Defines the UID/GID for the log group.
     * @hide
     */
    public static final int LOG_UID = 1007;

    /**
     * Defines the UID/GID for the WIFI supplicant process.
     * @hide
     */
    public static final int WIFI_UID = 1010;

    /**
     * Defines the start of a range of UIDs (and GIDs), going from this
     * number to {@link #LAST_APPLICATION_UID} that are reserved for assigning
     * to applications.
     */
    public static final int FIRST_APPLICATION_UID = 10000;
    /**
     * Last of application-specific UIDs starting at
     * {@link #FIRST_APPLICATION_UID}.
     */
    public static final int LAST_APPLICATION_UID = 99999;

    /**
     * Defines a secondary group id for access to the bluetooth hardware.
     */
    public static final int BLUETOOTH_GID = 2000;
    
    /**
     * Standard priority of application threads.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_DEFAULT = 0;

    /*
     * ***************************************
     * ** Keep in sync with utils/threads.h **
     * ***************************************
     */
    
    /**
     * Lowest available thread priority.  Only for those who really, really
     * don't want to run if anything else is happening.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_LOWEST = 19;
    
    /**
     * Standard priority background threads.  This gives your thread a slightly
     * lower than normal priority, so that it will have less chance of impacting
     * the responsiveness of the user interface.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_BACKGROUND = 10;
    
    /**
     * Standard priority of threads that are currently running a user interface
     * that the user is interacting with.  Applications can not normally
     * change to this priority; the system will automatically adjust your
     * application threads as the user moves through the UI.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_FOREGROUND = -2;
    
    /**
     * Standard priority of system display threads, involved in updating
     * the user interface.  Applications can not
     * normally change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_DISPLAY = -4;
    
    /**
     * Standard priority of the most important display threads, for compositing
     * the screen and retrieving input events.  Applications can not normally
     * change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_URGENT_DISPLAY = -8;

    /**
     * Standard priority of audio threads.  Applications can not normally
     * change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_AUDIO = -16;

    /**
     * Standard priority of the most important audio threads.
     * Applications can not normally change to this priority.
     * Use with {@link #setThreadPriority(int)} and
     * {@link #setThreadPriority(int, int)}, <b>not with the normal
     * {@link java.lang.Thread} class.
     */
    public static final int THREAD_PRIORITY_URGENT_AUDIO = -19;

    /**
     * Minimum increment to make a priority more favorable.
     */
    public static final int THREAD_PRIORITY_MORE_FAVORABLE = -1;

    /**
     * Minimum increment to make a priority less favorable.
     */
    public static final int THREAD_PRIORITY_LESS_FAVORABLE = +1;

    /**
     * Default thread group - gets a 'normal' share of the CPU
     * @hide
     */
    public static final int THREAD_GROUP_DEFAULT = 0;

    /**
     * Background non-interactive thread group - All threads in
     * this group are scheduled with a reduced share of the CPU.
     * @hide
     */
    public static final int THREAD_GROUP_BG_NONINTERACTIVE = 1;

    /**
     * Foreground 'boost' thread group - All threads in
     * this group are scheduled with an increased share of the CPU
     * @hide
     **/
    public static final int THREAD_GROUP_FG_BOOST = 2;

    public static final int SIGNAL_QUIT = 3;
    public static final int SIGNAL_KILL = 9;
    public static final int SIGNAL_USR1 = 10;
    
    // State for communicating with zygote process

    static LocalSocket sZygoteSocket;
    static DataInputStream sZygoteInputStream;
    static BufferedWriter sZygoteWriter;

    /** true if previous zygote open failed */
    static boolean sPreviousZygoteOpenFailed;

    /**
     * Start a new process.
     * 
     * <p>If processes are enabled, a new process is created and the
     * static main() function of a <var>processClass is executed there.
     * The process will continue running after this function returns.
     * 
     * <p>If processes are not enabled, a new thread in the caller's
     * process is created and main() of <var>processClass called there.
     * 
     * <p>The niceName parameter, if not an empty string, is a custom name to
     * give to the process instead of using processClass.  This allows you to
     * make easily identifyable processes even if you are using the same base
     * <var>processClass to start them.
     * 
     * @param processClass The class to use as the process's main entry
     *                     point.
     * @param niceName A more readable name to use for the process.
     * @param uid The user-id under which the process will run.
     * @param gid The group-id under which the process will run.
     * @param gids Additional group-ids associated with the process.
     * @param enableDebugger True if debugging should be enabled for this process.
     * @param zygoteArgs Additional arguments to supply to the zygote process.
     * 
     * @return int If > 0 the pid of the new process; if 0 the process is
     *         being emulated by a thread
     * @throws RuntimeException on fatal start failure
     * 
     * {@hide}
     */
    public static final int start(final String processClass,
                                  final String niceName,
                                  int uid, int gid, int[] gids,
                                  int debugFlags,
                                  String[] zygoteArgs)
    {
        if (supportsProcesses()) {
            try {
                return startViaZygote(processClass, niceName, uid, gid, gids,
                        debugFlags, zygoteArgs);
            } catch (ZygoteStartFailedEx ex) {
                Log.e(LOG_TAG,
                        "Starting VM process through Zygote failed");
                throw new RuntimeException(
                        "Starting VM process through Zygote failed", ex);
            }
        } else {
            // Running in single-process mode
            
            Runnable runnable = new Runnable() {
                        public void run() {
                            Process.invokeStaticMain(processClass);
                        }
            };
            
            // Thread constructors must not be called with null names (see spec). 
            if (niceName != null) {
                new Thread(runnable, niceName).start();
            } else {
                new Thread(runnable).start();
            }
            
            return 0;
        }
    }
    
    /**
     * Start a new process.  Don't supply a custom nice name.
     * {@hide}
     */
    public static final int start(String processClass, int uid, int gid,
            int[] gids, int debugFlags, String[] zygoteArgs) {
        return start(processClass, "", uid, gid, gids, 
                debugFlags, zygoteArgs);
    }

    private static void invokeStaticMain(String className) {
        Class cl;
        Object args[] = new Object[1];

        args[0] = new String[0];     //this is argv
   
        try {
            cl = Class.forName(className);
            cl.getMethod("main", new Class[] { String[].class })
                    .invoke(null, args);            
        } catch (Exception ex) {
            // can be: ClassNotFoundException,
            // NoSuchMethodException, SecurityException,
            // IllegalAccessException, IllegalArgumentException
            // InvocationTargetException
            // or uncaught exception from main()

            Log.e(LOG_TAG, "Exception invoking static main on " 
                    + className, ex);

            throw new RuntimeException(ex);
        }

    }

    /** retry interval for opening a zygote socket */
    static final int ZYGOTE_RETRY_MILLIS = 500;

    /**
     * Tries to open socket to Zygote process if not already open. If
     * already open, does nothing.  May block and retry.
     */
    private static void openZygoteSocketIfNeeded() 
            throws ZygoteStartFailedEx {

        int retryCount;

        if (sPreviousZygoteOpenFailed) {
            /*
             * If we've failed before, expect that we'll fail again and
             * don't pause for retries.
             */
            retryCount = 0;
        } else {
            retryCount = 10;            
        }

        /*
         * See bug #811181: Sometimes runtime can make it up before zygote.
         * Really, we'd like to do something better to avoid this condition,
         * but for now just wait a bit...
         */
        for (int retry = 0
                ; (sZygoteSocket == null) && (retry < (retryCount + 1))
                ; retry++ ) {

            if (retry > 0) {
                try {
                    Log.i("Zygote", "Zygote not up yet, sleeping...");
                    Thread.sleep(ZYGOTE_RETRY_MILLIS);
                } catch (InterruptedException ex) {
                    // should never happen
                }
            }

            try {
                sZygoteSocket = new LocalSocket();

                sZygoteSocket.connect(new LocalSocketAddress(ZYGOTE_SOCKET, 
                        LocalSocketAddress.Namespace.RESERVED));

                sZygoteInputStream
                        = new DataInputStream(sZygoteSocket.getInputStream());

                sZygoteWriter =
                    new BufferedWriter(
                            new OutputStreamWriter(
                                    sZygoteSocket.getOutputStream()),
                            256);

                Log.i("Zygote", "Process: zygote socket opened");

                sPreviousZygoteOpenFailed = false;
                break;
            } catch (IOException ex) {
                if (sZygoteSocket != null) {
                    try {
                        sZygoteSocket.close();
                    } catch (IOException ex2) {
                        Log.e(LOG_TAG,"I/O exception on close after exception",
                                ex2);
                    }
                }

                sZygoteSocket = null;
            }
        }

        if (sZygoteSocket == null) {
            sPreviousZygoteOpenFailed = true;
            throw new ZygoteStartFailedEx("connect failed");                 
        }
    }

    /**
     * Sends an argument list to the zygote process, which starts a new child
     * and returns the child's pid. Please note: the present implementation
     * replaces newlines in the argument list with spaces.
     * @param args argument list
     * @return PID of new child process
     * @throws ZygoteStartFailedEx if process start failed for any reason
     */
    private static int zygoteSendArgsAndGetPid(ArrayList<String> args)
            throws ZygoteStartFailedEx {

        int pid;

        openZygoteSocketIfNeeded();

        try {
            /**
             * See com.android.internal.os.ZygoteInit.readArgumentList()
             * Presently the wire format to the zygote process is:
             * a) a count of arguments (argc, in essence)
             * b) a number of newline-separated argument strings equal to count
             *
             * After the zygote process reads these it will write the pid of
             * the child or -1 on failure.
             */

            sZygoteWriter.write(Integer.toString(args.size()));
            sZygoteWriter.newLine();

            int sz = args.size();
            for (int i = 0; i < sz; i++) {
                String arg = args.get(i);
                if (arg.indexOf('\n') >= 0) {
                    throw new ZygoteStartFailedEx(
                            "embedded newlines not allowed");
                }
                sZygoteWriter.write(arg);
                sZygoteWriter.newLine();
            }

            sZygoteWriter.flush();

            // Should there be a timeout on this?
            pid = sZygoteInputStream.readInt();

            if (pid < 0) {
                throw new ZygoteStartFailedEx("fork() failed");
            }
        } catch (IOException ex) {
            try {
                if (sZygoteSocket != null) {
                    sZygoteSocket.close();
                }
            } catch (IOException ex2) {
                // we're going to fail anyway
                Log.e(LOG_TAG,"I/O exception on routine close", ex2);
            }

            sZygoteSocket = null;

            throw new ZygoteStartFailedEx(ex);
        }

        return pid;
    }

    /**
     * Starts a new process via the zygote mechanism.
     *
     * @param processClass Class name whose static main() to run
     * @param niceName 'nice' process name to appear in ps
     * @param uid a POSIX uid that the new process should setuid() to
     * @param gid a POSIX gid that the new process shuold setgid() to
     * @param gids null-ok; a list of supplementary group IDs that the
     * new process should setgroup() to.
     * @param enableDebugger True if debugging should be enabled for this process.
     * @param extraArgs Additional arguments to supply to the zygote process.
     * @return PID
     * @throws ZygoteStartFailedEx if process start failed for any reason
     */
    private static int startViaZygote(final String processClass,
                                  final String niceName,
                                  final int uid, final int gid,
                                  final int[] gids,
                                  int debugFlags,
                                  String[] extraArgs)
                                  throws ZygoteStartFailedEx {
        int pid;

        synchronized(Process.class) {
            ArrayList<String> argsForZygote = new ArrayList();

            // --runtime-init, --setuid=, --setgid=,
            // and --setgroups= must go first
            argsForZygote.add("--runtime-init");
            argsForZygote.add("--setuid=" + uid);
            argsForZygote.add("--setgid=" + gid);
            if ((debugFlags & Zygote.DEBUG_ENABLE_SAFEMODE) != 0) {
                argsForZygote.add("--enable-safemode");
            }
            if ((debugFlags & Zygote.DEBUG_ENABLE_DEBUGGER) != 0) {
                argsForZygote.add("--enable-debugger");
            }
            if ((debugFlags & Zygote.DEBUG_ENABLE_CHECKJNI) != 0) {
                argsForZygote.add("--enable-checkjni");
            }
            if ((debugFlags & Zygote.DEBUG_ENABLE_ASSERT) != 0) {
                argsForZygote.add("--enable-assert");
            }

            //TODO optionally enable debuger
            //argsForZygote.add("--enable-debugger");

            // --setgroups is a comma-separated list
            if (gids != null && gids.length > 0) {
                StringBuilder sb = new StringBuilder();
                sb.append("--setgroups=");

                int sz = gids.length;
                for (int i = 0; i < sz; i++) {
                    if (i != 0) {
                        sb.append(',');
                    }
                    sb.append(gids[i]);
                }

                argsForZygote.add(sb.toString());
            }

            if (niceName != null) {
                argsForZygote.add("--nice-name=" + niceName);
            }

            argsForZygote.add(processClass);

            if (extraArgs != null) {
                for (String arg : extraArgs) {
                    argsForZygote.add(arg);
                }
            }
            
            pid = zygoteSendArgsAndGetPid(argsForZygote);
        }

        if (pid <= 0) {
            throw new ZygoteStartFailedEx("zygote start failed:" + pid);
        }

        return pid;
    }
    
    /**
     * Returns elapsed milliseconds of the time this process has run.
     * @return  Returns the number of milliseconds this process has return.
     */
    public static final native long getElapsedCpuTime();
    
    /**
     * Returns the identifier of this process, which can be used with
     * {@link #killProcess} and {@link #sendSignal}.
     */
    public static final native int myPid();

    /**
     * Returns the identifier of the calling thread, which be used with
     * {@link #setThreadPriority(int, int)}.
     */
    public static final native int myTid();

    /**
     * Returns the identifier of this process's user.
     */
    public static final native int myUid();

    /**
     * Returns the UID assigned to a particular user name, or -1 if there is
     * none.  If the given string consists of only numbers, it is converted
     * directly to a uid.
     */
    public static final native int getUidForName(String name);
    
    /**
     * Returns the GID assigned to a particular user name, or -1 if there is
     * none.  If the given string consists of only numbers, it is converted
     * directly to a gid.
     */
    public static final native int getGidForName(String name);

    /**
     * Returns a uid for a currently running process.
     * @param pid the process id
     * @return the uid of the process, or -1 if the process is not running.
     * @hide pending API council review
     */
    public static final int getUidForPid(int pid) {
        String[] procStatusLabels = { "Uid:" };
        long[] procStatusValues = new long[1];
        procStatusValues[0] = -1;
        Process.readProcLines("/proc/" + pid + "/status", procStatusLabels, procStatusValues);
        return (int) procStatusValues[0];
    }

    /**
     * Set the priority of a thread, based on Linux priorities.
     * 
     * @param tid The identifier of the thread/process to change.
     * @param priority A Linux priority level, from -20 for highest scheduling
     * priority to 19 for lowest scheduling priority.
     * 
     * @throws IllegalArgumentException Throws IllegalArgumentException if
     * <var>tid does not exist.
     * @throws SecurityException Throws SecurityException if your process does
     * not have permission to modify the given thread, or to use the given
     * priority.
     */
    public static final native void setThreadPriority(int tid, int priority)
            throws IllegalArgumentException, SecurityException;

    /**
     * Sets the scheduling group for a thread.
     * @hide
     * @param tid The indentifier of the thread/process to change.
     * @param group The target group for this thread/process.
     * 
     * @throws IllegalArgumentException Throws IllegalArgumentException if
     * <var>tid does not exist.
     * @throws SecurityException Throws SecurityException if your process does
     * not have permission to modify the given thread, or to use the given
     * priority.
     */
    public static final native void setThreadGroup(int tid, int group)
            throws IllegalArgumentException, SecurityException;
    /**
     * Sets the scheduling group for a process and all child threads
     * @hide
     * @param pid The indentifier of the process to change.
     * @param group The target group for this process.
     * 
     * @throws IllegalArgumentException Throws IllegalArgumentException if
     * <var>tid does not exist.
     * @throws SecurityException Throws SecurityException if your process does
     * not have permission to modify the given thread, or to use the given
     * priority.
     */
    public static final native void setProcessGroup(int pid, int group)
            throws IllegalArgumentException, SecurityException;
    
    /**
     * Set the priority of the calling thread, based on Linux priorities.  See
     * {@link #setThreadPriority(int, int)} for more information.
     * 
     * @param priority A Linux priority level, from -20 for highest scheduling
     * priority to 19 for lowest scheduling priority.
     * 
     * @throws IllegalArgumentException Throws IllegalArgumentException if
     * <var>tid does not exist.
     * @throws SecurityException Throws SecurityException if your process does
     * not have permission to modify the given thread, or to use the given
     * priority.
     * 
     * @see #setThreadPriority(int, int)
     */
    public static final native void setThreadPriority(int priority)
            throws IllegalArgumentException, SecurityException;
    
    /**
     * Return the current priority of a thread, based on Linux priorities.
     * 
     * @param tid The identifier of the thread/process to change.
     * 
     * @return Returns the current priority, as a Linux priority level,
     * from -20 for highest scheduling priority to 19 for lowest scheduling
     * priority.
     * 
     * @throws IllegalArgumentException Throws IllegalArgumentException if
     * <var>tid does not exist.
     */
    public static final native int getThreadPriority(int tid)
            throws IllegalArgumentException;
    
    /**
     * Determine whether the current environment supports multiple processes.
     * 
     * @return Returns true if the system can run in multiple processes, else
     * false if everything is running in a single process.
     */
    public static final native boolean supportsProcesses();

    /**
     * Set the out-of-memory badness adjustment for a process.
     * 
     * @param pid The process identifier to set.
     * @param amt Adjustment value -- linux allows -16 to +15.
     * 
     * @return Returns true if the underlying system supports this
     *         feature, else false.
     *         
     * {@hide}
     */
    public static final native boolean setOomAdj(int pid, int amt);

    /**
     * Change this process's argv[0] parameter.  This can be useful to show
     * more descriptive information in things like the 'ps' command.
     * 
     * @param text The new name of this process.
     * 
     * {@hide}
     */
    public static final native void setArgV0(String text);

    /**
     * Kill the process with the given PID.
     * Note that, though this API allows us to request to
     * kill any process based on its PID, the kernel will
     * still impose standard restrictions on which PIDs you
     * are actually able to kill.  Typically this means only
     * the process running the caller's packages/application
     * and any additional processes created by that app; packages
     * sharing a common UID will also be able to kill each
     * other's processes.
     */
    public static final void killProcess(int pid) {
        sendSignal(pid, SIGNAL_KILL);
    }

    /** @hide */
    public static final native int setUid(int uid);

    /** @hide */
    public static final native int setGid(int uid);

    /**
     * Send a signal to the given process.
     * 
     * @param pid The pid of the target process.
     * @param signal The signal to send.
     */
    public static final native void sendSignal(int pid, int signal);
    
    /**
     * @hide
     * Private impl for avoiding a log message...  DO NOT USE without doing
     * your own log, or the Android Illuminati will find you some night and
     * beat you up.
     */
    public static final void killProcessQuiet(int pid) {
        sendSignalQuiet(pid, SIGNAL_KILL);
    }

    /**
     * @hide
     * Private impl for avoiding a log message...  DO NOT USE without doing
     * your own log, or the Android Illuminati will find you some night and
     * beat you up.
     */
    public static final native void sendSignalQuiet(int pid, int signal);
    
    /** @hide */
    public static final native long getFreeMemory();
    
    /** @hide */
    public static final native void readProcLines(String path,
            String[] reqFields, long[] outSizes);
    
    /** @hide */
    public static final native int[] getPids(String path, int[] lastArray);
    
    /** @hide */
    public static final int PROC_TERM_MASK = 0xff;
    /** @hide */
    public static final int PROC_ZERO_TERM = 0;
    /** @hide */
    public static final int PROC_SPACE_TERM = (int)' ';
    /** @hide */
    public static final int PROC_TAB_TERM = (int)'\t';
    /** @hide */
    public static final int PROC_COMBINE = 0x100;
    /** @hide */
    public static final int PROC_PARENS = 0x200;
    /** @hide */
    public static final int PROC_OUT_STRING = 0x1000;
    /** @hide */
    public static final int PROC_OUT_LONG = 0x2000;
    /** @hide */
    public static final int PROC_OUT_FLOAT = 0x4000;
    
    /** @hide */
    public static final native boolean readProcFile(String file, int[] format,
            String[] outStrings, long[] outLongs, float[] outFloats);
    
    /** @hide */
    public static final native boolean parseProcLine(byte[] buffer, int startIndex, 
            int endIndex, int[] format, String[] outStrings, long[] outLongs, float[] outFloats);

    /**
     * Gets the total Pss value for a given process, in bytes.
     * 
     * @param pid the process to the Pss for
     * @return the total Pss value for the given process in bytes,
     *  or -1 if the value cannot be determined 
     * @hide
     */
    public static final native long getPss(int pid);
}

Other Android examples (source code examples)

Here is a short list of links related to this Android Process.java source code file:

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