Java tutorial
/* * 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.commons.io; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.StringTokenizer; /** * General File System utilities. * <p> * This class provides static utility methods for general file system * functions not provided via the JDK {@link java.io.File File} class. * <p> * The current functions provided are: * <ul> * <li>Get the free space on a drive * </ul> * * @author Frank W. Zammetti * @author Stephen Colebourne * @author Thomas Ledoux * @author James Urie * @author Magnus Grimsell * @author Thomas Ledoux * @version $Id: FileSystemUtils.java 453889 2006-10-07 11:56:25Z scolebourne $ * @since Commons IO 1.1 */ public class FileSystemUtils { /** Singleton instance, used mainly for testing. */ private static final FileSystemUtils INSTANCE = new FileSystemUtils(); /** Operating system state flag for error. */ private static final int INIT_PROBLEM = -1; /** Operating system state flag for neither Unix nor Windows. */ private static final int OTHER = 0; /** Operating system state flag for Windows. */ private static final int WINDOWS = 1; /** Operating system state flag for Unix. */ private static final int UNIX = 2; /** Operating system state flag for Posix flavour Unix. */ private static final int POSIX_UNIX = 3; /** The operating system flag. */ private static final int OS; static { int os = OTHER; try { String osName = System.getProperty("os.name"); if (osName == null) { throw new IOException("os.name not found"); } osName = osName.toLowerCase(); // match if (osName.indexOf("windows") != -1) { os = WINDOWS; } else if (osName.indexOf("linux") != -1 || osName.indexOf("sun os") != -1 || osName.indexOf("sunos") != -1 || osName.indexOf("solaris") != -1 || osName.indexOf("mpe/ix") != -1 || osName.indexOf("freebsd") != -1 || osName.indexOf("irix") != -1 || osName.indexOf("digital unix") != -1 || osName.indexOf("unix") != -1 || osName.indexOf("mac os x") != -1) { os = UNIX; } else if (osName.indexOf("hp-ux") != -1 || osName.indexOf("aix") != -1) { os = POSIX_UNIX; } else { os = OTHER; } } catch (Exception ex) { os = INIT_PROBLEM; } OS = os; } /** * Instances should NOT be constructed in standard programming. */ public FileSystemUtils() { super(); } //----------------------------------------------------------------------- /** * Returns the free space on a drive or volume by invoking * the command line. * This method does not normalize the result, and typically returns * bytes on Windows, 512 byte units on OS X and kilobytes on Unix. * As this is not very useful, this method is deprecated in favour * of {@link #freeSpaceKb(String)} which returns a result in kilobytes. * <p> * Note that some OS's are NOT currently supported, including OS/390, * OpenVMS and and SunOS 5. (SunOS is supported by <code>freeSpaceKb</code>.) * <pre> * FileSystemUtils.freeSpace("C:"); // Windows * FileSystemUtils.freeSpace("/volume"); // *nix * </pre> * The free space is calculated via the command line. * It uses 'dir /-c' on Windows and 'df' on *nix. * * @param path the path to get free space for, not null, not empty on Unix * @return the amount of free drive space on the drive or volume * @throws IllegalArgumentException if the path is invalid * @throws IllegalStateException if an error occurred in initialisation * @throws IOException if an error occurs when finding the free space * @since Commons IO 1.1, enhanced OS support in 1.2 and 1.3 * @deprecated Use freeSpaceKb(String) * Deprecated from 1.3, may be removed in 2.0 */ public static long freeSpace(String path) throws IOException { return INSTANCE.freeSpaceOS(path, OS, false); } //----------------------------------------------------------------------- /** * Returns the free space on a drive or volume in kilobytes by invoking * the command line. * <pre> * FileSystemUtils.freeSpaceKb("C:"); // Windows * FileSystemUtils.freeSpaceKb("/volume"); // *nix * </pre> * The free space is calculated via the command line. * It uses 'dir /-c' on Windows, 'df -kP' on AIX/HP-UX and 'df -k' on other Unix. * <p> * In order to work, you must be running Windows, or have a implementation of * Unix df that supports GNU format when passed -k (or -kP). If you are going * to rely on this code, please check that it works on your OS by running * some simple tests to compare the command line with the output from this class. * If your operating system isn't supported, please raise a JIRA call detailing * the exact result from df -k and as much other detail as possible, thanks. * * @param path the path to get free space for, not null, not empty on Unix * @return the amount of free drive space on the drive or volume in kilobytes * @throws IllegalArgumentException if the path is invalid * @throws IllegalStateException if an error occurred in initialisation * @throws IOException if an error occurs when finding the free space * @since Commons IO 1.2, enhanced OS support in 1.3 */ public static long freeSpaceKb(String path) throws IOException { return INSTANCE.freeSpaceOS(path, OS, true); } //----------------------------------------------------------------------- /** * Returns the free space on a drive or volume in a cross-platform manner. * Note that some OS's are NOT currently supported, including OS/390. * <pre> * FileSystemUtils.freeSpace("C:"); // Windows * FileSystemUtils.freeSpace("/volume"); // *nix * </pre> * The free space is calculated via the command line. * It uses 'dir /-c' on Windows and 'df' on *nix. * * @param path the path to get free space for, not null, not empty on Unix * @param os the operating system code * @param kb whether to normalize to kilobytes * @return the amount of free drive space on the drive or volume * @throws IllegalArgumentException if the path is invalid * @throws IllegalStateException if an error occurred in initialisation * @throws IOException if an error occurs when finding the free space */ long freeSpaceOS(String path, int os, boolean kb) throws IOException { if (path == null) { throw new IllegalArgumentException("Path must not be empty"); } switch (os) { case WINDOWS: return (kb ? freeSpaceWindows(path) / 1024 : freeSpaceWindows(path)); case UNIX: return freeSpaceUnix(path, kb, false); case POSIX_UNIX: return freeSpaceUnix(path, kb, true); case OTHER: throw new IllegalStateException("Unsupported operating system"); default: throw new IllegalStateException("Exception caught when determining operating system"); } } //----------------------------------------------------------------------- /** * Find free space on the Windows platform using the 'dir' command. * * @param path the path to get free space for, including the colon * @return the amount of free drive space on the drive * @throws IOException if an error occurs */ long freeSpaceWindows(String path) throws IOException { path = FilenameUtils.normalize(path); if (path.length() > 2 && path.charAt(1) == ':') { path = path.substring(0, 2); // seems to make it work } // build and run the 'dir' command String[] cmdAttribs = new String[] { "cmd.exe", "/C", "dir /-c " + path }; // read in the output of the command to an ArrayList List lines = performCommand(cmdAttribs, Integer.MAX_VALUE); // now iterate over the lines we just read and find the LAST // non-empty line (the free space bytes should be in the last element // of the ArrayList anyway, but this will ensure it works even if it's // not, still assuming it is on the last non-blank line) for (int i = lines.size() - 1; i >= 0; i--) { String line = (String) lines.get(i); if (line.length() > 0) { return parseDir(line, path); } } // all lines are blank throw new IOException("Command line 'dir /-c' did not return any info " + "for path '" + path + "'"); } /** * Parses the Windows dir response last line * * @param line the line to parse * @param path the path that was sent * @return the number of bytes * @throws IOException if an error occurs */ long parseDir(String line, String path) throws IOException { // read from the end of the line to find the last numeric // character on the line, then continue until we find the first // non-numeric character, and everything between that and the last // numeric character inclusive is our free space bytes count int bytesStart = 0; int bytesEnd = 0; int j = line.length() - 1; innerLoop1: while (j >= 0) { char c = line.charAt(j); if (Character.isDigit(c)) { // found the last numeric character, this is the end of // the free space bytes count bytesEnd = j + 1; break innerLoop1; } j--; } innerLoop2: while (j >= 0) { char c = line.charAt(j); if (!Character.isDigit(c) && c != ',' && c != '.') { // found the next non-numeric character, this is the // beginning of the free space bytes count bytesStart = j + 1; break innerLoop2; } j--; } if (j < 0) { throw new IOException("Command line 'dir /-c' did not return valid info " + "for path '" + path + "'"); } // remove commas and dots in the bytes count StringBuffer buf = new StringBuffer(line.substring(bytesStart, bytesEnd)); for (int k = 0; k < buf.length(); k++) { if (buf.charAt(k) == ',' || buf.charAt(k) == '.') { buf.deleteCharAt(k--); } } return parseBytes(buf.toString(), path); } //----------------------------------------------------------------------- /** * Find free space on the *nix platform using the 'df' command. * * @param path the path to get free space for * @param kb whether to normalize to kilobytes * @param posix whether to use the posix standard format flag * @return the amount of free drive space on the volume * @throws IOException if an error occurs */ long freeSpaceUnix(String path, boolean kb, boolean posix) throws IOException { if (path.length() == 0) { throw new IllegalArgumentException("Path must not be empty"); } path = FilenameUtils.normalize(path); // build and run the 'dir' command String flags = "-"; if (kb) { flags += "k"; } if (posix) { flags += "P"; } String[] cmdAttribs = (flags.length() > 1 ? new String[] { "df", flags, path } : new String[] { "df", path }); // perform the command, asking for up to 3 lines (header, interesting, overflow) List lines = performCommand(cmdAttribs, 3); if (lines.size() < 2) { // unknown problem, throw exception throw new IOException("Command line 'df' did not return info as expected " + "for path '" + path + "'- response was " + lines); } String line2 = (String) lines.get(1); // the line we're interested in // Now, we tokenize the string. The fourth element is what we want. StringTokenizer tok = new StringTokenizer(line2, " "); if (tok.countTokens() < 4) { // could be long Filesystem, thus data on third line if (tok.countTokens() == 1 && lines.size() >= 3) { String line3 = (String) lines.get(2); // the line may be interested in tok = new StringTokenizer(line3, " "); } else { throw new IOException("Command line 'df' did not return data as expected " + "for path '" + path + "'- check path is valid"); } } else { tok.nextToken(); // Ignore Filesystem } tok.nextToken(); // Ignore 1K-blocks tok.nextToken(); // Ignore Used String freeSpace = tok.nextToken(); return parseBytes(freeSpace, path); } //----------------------------------------------------------------------- /** * Parses the bytes from a string. * * @param freeSpace the free space string * @param path the path * @return the number of bytes * @throws IOException if an error occurs */ long parseBytes(String freeSpace, String path) throws IOException { try { long bytes = Long.parseLong(freeSpace); if (bytes < 0) { throw new IOException("Command line 'df' did not find free space in response " + "for path '" + path + "'- check path is valid"); } return bytes; } catch (NumberFormatException ex) { throw new IOException("Command line 'df' did not return numeric data as expected " + "for path '" + path + "'- check path is valid"); } } //----------------------------------------------------------------------- /** * Performs the os command. * * @param cmdAttribs the command line parameters * @param max The maximum limit for the lines returned * @return the parsed data * @throws IOException if an error occurs */ List performCommand(String[] cmdAttribs, int max) throws IOException { // this method does what it can to avoid the 'Too many open files' error // based on trial and error and these links: // http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4784692 // http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4801027 // http://forum.java.sun.com/thread.jspa?threadID=533029&messageID=2572018 // however, its still not perfect as the JDK support is so poor // (see commond-exec or ant for a better multi-threaded multi-os solution) List lines = new ArrayList(20); Process proc = null; InputStream in = null; OutputStream out = null; InputStream err = null; BufferedReader inr = null; try { proc = openProcess(cmdAttribs); in = proc.getInputStream(); out = proc.getOutputStream(); err = proc.getErrorStream(); inr = new BufferedReader(new InputStreamReader(in)); String line = inr.readLine(); while (line != null && lines.size() < max) { line = line.toLowerCase().trim(); lines.add(line); line = inr.readLine(); } proc.waitFor(); if (proc.exitValue() != 0) { // os command problem, throw exception throw new IOException("Command line returned OS error code '" + proc.exitValue() + "' for command " + Arrays.asList(cmdAttribs)); } if (lines.size() == 0) { // unknown problem, throw exception throw new IOException( "Command line did not return any info " + "for command " + Arrays.asList(cmdAttribs)); } return lines; } catch (InterruptedException ex) { throw new IOException("Command line threw an InterruptedException '" + ex.getMessage() + "' for command " + Arrays.asList(cmdAttribs)); } finally { IOUtils.closeQuietly(in); IOUtils.closeQuietly(out); IOUtils.closeQuietly(err); IOUtils.closeQuietly(inr); if (proc != null) { proc.destroy(); } } } /** * Opens the process to the operating system. * * @param cmdAttribs the command line parameters * @return the process * @throws IOException if an error occurs */ Process openProcess(String[] cmdAttribs) throws IOException { return Runtime.getRuntime().exec(cmdAttribs); } }