Java tutorial
package com.ruizhan.hadoop.hdfs; /** * 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. */ import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.LinkedList; import org.apache.hadoop.util.StringUtils; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.Path; import org.apache.hadoop.fs.shell.CommandFactory; import org.apache.hadoop.fs.shell.CommandFormat; import org.apache.hadoop.fs.shell.FsCommand; import org.apache.hadoop.fs.shell.PathData; /** * Get a listing of all files in that match the file patterns. */ @InterfaceAudience.Private @InterfaceStability.Unstable class Ls extends FsCommand { public static void registerCommands(CommandFactory factory) { factory.addClass(Ls.class, "-ls"); factory.addClass(Lsr.class, "-lsr"); } public static final String NAME = "ls"; public static final String USAGE = "[-d] [-h] [-R] [<path> ...]"; public static final String DESCRIPTION = "List the contents that match the specified file pattern. If\n" + "path is not specified, the contents of /user/<currentUser>\n" + "will be listed. Directory entries are of the form \n" + "\tdirName (full path) <dir> \n" + "and file entries are of the form \n" + "\tfileName(full path) <r n> size \n" + "where n is the number of replicas specified for the file \n" + "and size is the size of the file, in bytes.\n" + " -d Directories are listed as plain files.\n" + " -h Formats the sizes of files in a human-readable fashion\n" + " rather than a number of bytes.\n" + " -R Recursively list the contents of directories."; protected static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm"); protected int maxRepl = 3, maxLen = 10, maxOwner = 0, maxGroup = 0; protected String lineFormat; protected boolean dirRecurse; protected boolean humanReadable = false; protected String formatSize(long size) { return humanReadable ? StringUtils.TraditionalBinaryPrefix.long2String(size, "", 1) : String.valueOf(size); } @Override protected void processOptions(LinkedList<String> args) throws IOException { CommandFormat cf = new CommandFormat(0, Integer.MAX_VALUE, "d", "h", "R"); cf.parse(args); dirRecurse = !cf.getOpt("d"); setRecursive(cf.getOpt("R") && dirRecurse); humanReadable = cf.getOpt("h"); if (args.isEmpty()) args.add(Path.CUR_DIR); } @Override protected void processPathArgument(PathData item) throws IOException { // implicitly recurse once for cmdline directories if (dirRecurse && item.stat.isDirectory()) { recursePath(item); } else { super.processPathArgument(item); } } @Override protected void processPaths(PathData parent, PathData... items) throws IOException { if (!isRecursive() && items.length != 0) { out.println("Found " + items.length + " items"); } adjustColumnWidths(items); super.processPaths(parent, items); } @Override protected void processPath(PathData item) throws IOException { FileStatus stat = item.stat; String line = String.format(lineFormat, (stat.isDirectory() ? "d" : "-"), stat.getPermission(), (stat.isFile() ? stat.getReplication() : "-"), stat.getOwner(), stat.getGroup(), formatSize(stat.getLen()), dateFormat.format(new Date(stat.getModificationTime())), item); out.println(line); } /** * Compute column widths and rebuild the format string * @param items to find the max field width for each column */ private void adjustColumnWidths(PathData items[]) { for (PathData item : items) { FileStatus stat = item.stat; maxRepl = maxLength(maxRepl, stat.getReplication()); maxLen = maxLength(maxLen, stat.getLen()); maxOwner = maxLength(maxOwner, stat.getOwner()); maxGroup = maxLength(maxGroup, stat.getGroup()); } StringBuilder fmt = new StringBuilder(); fmt.append("%s%s "); // permission string fmt.append("%" + maxRepl + "s "); // Do not use '%-0s' as a formatting conversion, since it will throw a // a MissingFormatWidthException if it is used in String.format(). // http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Formatter.html#intFlags fmt.append((maxOwner > 0) ? "%-" + maxOwner + "s " : "%s"); fmt.append((maxGroup > 0) ? "%-" + maxGroup + "s " : "%s"); fmt.append("%" + maxLen + "s "); fmt.append("%s %s"); // mod time & path lineFormat = fmt.toString(); } private int maxLength(int n, Object value) { return Math.max(n, (value != null) ? String.valueOf(value).length() : 0); } /** * Get a recursive listing of all files in that match the file patterns. * Same as "-ls -R" */ public static class Lsr extends Ls { public static final String NAME = "lsr"; @Override protected void processOptions(LinkedList<String> args) throws IOException { args.addFirst("-R"); super.processOptions(args); } @Override public String getReplacementCommand() { return "ls -R"; } } }