management/UnixOperatingSystemMXBean/GetOpenFileDescriptorCount.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
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 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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 */

/*
 * @bug     4858522
 * @summary Basic unit test of UnixOperatingSystemMXBean.getOpenFileDescriptorCount()
 * @author  Steve Bohne
 */

/*
 * This test is just a sanity check and does not check for the correct
 * value.  The correct value should be checked manually:
 * Solaris/Linux:
 *   1. Find the pid of the java process.
 *   2. In a shell, enter the command: "ls -1 /proc/<pid>/fd | wc -l"
 */

import com.sun.management.UnixOperatingSystemMXBean;
import java.lang.management.*;

public class GetOpenFileDescriptorCount {

    private static UnixOperatingSystemMXBean mbean =
        (UnixOperatingSystemMXBean)ManagementFactory.getOperatingSystemMXBean();

    // Careful with these values.
    private static final long MIN_COUNT_FOR_PASS = 1;
    // Max count for pass dynamically determined below
    private static long       max_count_for_pass = Long.MAX_VALUE;

    private static boolean trace = false;

    public static void main(String args[]) throws Exception {
        if (args.length > 0 && args[0].equals("trace")) {
            trace = true;
        }

        long max_count = mbean.getMaxFileDescriptorCount();
        if (max_count > 0) {
            max_count_for_pass = max_count;
        }

        long count = mbean.getOpenFileDescriptorCount();

        if (trace) {
            System.out.println("Open file descriptor count: " + count);
        }

        if (count < MIN_COUNT_FOR_PASS || count > max_count_for_pass) {
            throw new RuntimeException("Open file descriptor count " +
                                       "illegal value: " + count + " bytes " +
                                       "(MIN = " + MIN_COUNT_FOR_PASS + "; " +
                                       "MAX = " + max_count_for_pass + ")");
        }

        System.out.println("Test passed.");
    }
}