org.apache.hadoop.fs.Stat.java Source code

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Here is the source code for org.apache.hadoop.fs.Stat.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.fs;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.util.Shell;

import com.google.common.annotations.VisibleForTesting;

/**
 * Wrapper for the Unix stat(1) command. Used to workaround the lack of 
 * lstat(2) in Java 6.
 */
@InterfaceAudience.LimitedPrivate({ "HDFS", "MapReduce" })
@InterfaceStability.Evolving
public class Stat extends Shell {

    private final Path original;
    private final Path qualified;
    private final Path path;
    private final long blockSize;
    private final boolean dereference;

    private FileStatus stat;

    public Stat(Path path, long blockSize, boolean deref, FileSystem fs) throws IOException {
        super(0L, true);
        // Original path
        this.original = path;
        // Qualify the original and strip out URI fragment via toUri().getPath()
        Path stripped = new Path(original.makeQualified(fs.getUri(), fs.getWorkingDirectory()).toUri().getPath());
        // Re-qualify the bare stripped path and store it
        this.qualified = stripped.makeQualified(fs.getUri(), fs.getWorkingDirectory());
        // Strip back down to a plain path
        this.path = new Path(qualified.toUri().getPath());
        this.blockSize = blockSize;
        this.dereference = deref;
        // LANG = C setting
        Map<String, String> env = new HashMap<String, String>();
        env.put("LANG", "C");
        setEnvironment(env);
    }

    public FileStatus getFileStatus() throws IOException {
        run();
        return stat;
    }

    /**
     * Whether Stat is supported on the current platform
     * @return
     */
    public static boolean isAvailable() {
        if (Shell.LINUX || Shell.FREEBSD || Shell.MAC) {
            return true;
        }
        return false;
    }

    @VisibleForTesting
    FileStatus getFileStatusForTesting() {
        return stat;
    }

    @Override
    protected String[] getExecString() {
        String derefFlag = "-";
        if (dereference) {
            derefFlag = "-L";
        }
        if (Shell.LINUX) {
            return new String[] { "stat", derefFlag + "c", "%s,%F,%Y,%X,%a,%U,%G,%N", path.toString() };
        } else if (Shell.FREEBSD || Shell.MAC) {
            return new String[] { "stat", derefFlag + "f", "%z,%HT,%m,%a,%Op,%Su,%Sg,`link' -> `%Y'",
                    path.toString() };
        } else {
            throw new UnsupportedOperationException("stat is not supported on this platform");
        }
    }

    @Override
    protected void parseExecResult(BufferedReader lines) throws IOException {
        // Reset stat
        stat = null;

        String line = lines.readLine();
        if (line == null) {
            throw new IOException("Unable to stat path: " + original);
        }
        if (line.endsWith("No such file or directory") || line.endsWith("Not a directory")) {
            throw new FileNotFoundException("File " + original + " does not exist");
        }
        if (line.endsWith("Too many levels of symbolic links")) {
            throw new IOException("Possible cyclic loop while following symbolic" + " link " + original);
        }
        // 6,symbolic link,6,1373584236,1373584236,lrwxrwxrwx,andrew,andrew,`link' -> `target'
        // OR
        // 6,symbolic link,6,1373584236,1373584236,lrwxrwxrwx,andrew,andrew,'link' -> 'target'
        StringTokenizer tokens = new StringTokenizer(line, ",");
        try {
            long length = Long.parseLong(tokens.nextToken());
            boolean isDir = tokens.nextToken().equalsIgnoreCase("directory") ? true : false;
            // Convert from seconds to milliseconds
            long modTime = Long.parseLong(tokens.nextToken()) * 1000;
            long accessTime = Long.parseLong(tokens.nextToken()) * 1000;
            String octalPerms = tokens.nextToken();
            // FreeBSD has extra digits beyond 4, truncate them
            if (octalPerms.length() > 4) {
                int len = octalPerms.length();
                octalPerms = octalPerms.substring(len - 4, len);
            }
            FsPermission perms = new FsPermission(Short.parseShort(octalPerms, 8));
            String owner = tokens.nextToken();
            String group = tokens.nextToken();
            String symStr = tokens.nextToken();
            // 'notalink'
            // `link' -> `target' OR 'link' -> 'target'
            // '' -> ''
            Path symlink = null;
            String parts[] = symStr.split(" -> ");
            try {
                String target = parts[1];
                target = target.substring(1, target.length() - 1);
                if (!target.isEmpty()) {
                    symlink = new Path(target);
                }
            } catch (ArrayIndexOutOfBoundsException e) {
                // null if not a symlink
            }
            // Set stat
            stat = new FileStatus(length, isDir, 1, blockSize, modTime, accessTime, perms, owner, group, symlink,
                    qualified);
        } catch (NumberFormatException e) {
            throw new IOException("Unexpected stat output: " + line, e);
        } catch (NoSuchElementException e) {
            throw new IOException("Unexpected stat output: " + line, e);
        }
    }
}