Commons IO example source code file (FileSystemUtils.java)

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

Java - Commons IO tags/keywords

command, command, df, df, filesystemutils, io, ioexception, ioexception, list, os, other, posix_unix, string, string, util, windows

The Commons IO FileSystemUtils.java source code

/*
 * 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.File;
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.Locale;
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 1003647 2010-10-01 20:53:59Z niallp $
 * @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;

    /** The path to df */
    private static final String DF;

    static {
        int os = OTHER;
        String dfPath = "df";
        try {
            String osName = System.getProperty("os.name");
            if (osName == null) {
                throw new IOException("os.name not found");
            }
            osName = osName.toLowerCase(Locale.ENGLISH);
            // match
            if (osName.indexOf("windows") != -1) {
                os = WINDOWS;
            } else if (osName.indexOf("linux") != -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("sun os") != -1 ||
                osName.indexOf("sunos") != -1 ||
                osName.indexOf("solaris") != -1) {
                os = POSIX_UNIX;
                dfPath = "/usr/xpg4/bin/df";
            } 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;
        DF = dfPath;
    }

    /**
     * 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. 
     * <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
     */
    @Deprecated
    public static long freeSpace(String path) throws IOException {
        return INSTANCE.freeSpaceOS(path, OS, false, -1);
    }

    //-----------------------------------------------------------------------
    /**
     * 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 freeSpaceKb(path, -1);
    }
    /**
     * 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
     * @param timeout The timout amount in milliseconds or no timeout if the value
     *  is zero or less
     * @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 2.0
     */
    public static long freeSpaceKb(String path, long timeout) throws IOException {
        return INSTANCE.freeSpaceOS(path, OS, true, timeout);
    }

    /**
     * Returns the disk size of the volume which holds the working directory.
     * <p>
     * Identical to:
     * <pre>
     * freeSpaceKb(new File(".").getAbsolutePath())
     * </pre>
     * @return the amount of free drive space on the drive or volume in kilobytes
     * @throws IllegalStateException if an error occurred in initialisation
     * @throws IOException if an error occurs when finding the free space
     * @since Commons IO 2.0
     */
    public static long freeSpaceKb() throws IOException {
        return freeSpaceKb(-1); 
    }

    /**
     * Returns the disk size of the volume which holds the working directory.
     * <p>
     * Identical to:
     * <pre>
     * freeSpaceKb(new File(".").getAbsolutePath())
     * </pre>
     * @param timeout The timout amount in milliseconds or no timeout if the value
     *  is zero or less
     * @return the amount of free drive space on the drive or volume in kilobytes
     * @throws IllegalStateException if an error occurred in initialisation
     * @throws IOException if an error occurs when finding the free space
     * @since Commons IO 2.0
     */
    public static long freeSpaceKb(long timeout) throws IOException {
        return freeSpaceKb(new File(".").getAbsolutePath(), timeout); 
    }
    
    //-----------------------------------------------------------------------
    /**
     * 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
     * @param timeout The timout amount in milliseconds or no timeout if the value
     *  is zero or less
     * @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, long timeout) throws IOException {
        if (path == null) {
            throw new IllegalArgumentException("Path must not be empty");
        }
        switch (os) {
            case WINDOWS:
                return (kb ? freeSpaceWindows(path, timeout) / 1024 : freeSpaceWindows(path, timeout));
            case UNIX:
                return freeSpaceUnix(path, kb, false, timeout);
            case POSIX_UNIX:
                return freeSpaceUnix(path, kb, true, timeout);
            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
     * @param timeout The timout amount in milliseconds or no timeout if the value
     *  is zero or less
     * @return the amount of free drive space on the drive
     * @throws IOException if an error occurs
     */
    long freeSpaceWindows(String path, long timeout) throws IOException {
        path = FilenameUtils.normalize(path, false);
        if (path.length() > 0 && path.charAt(0) != '"') {
            path = "\"" + path + "\"";
        }
        
        // 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<String> lines = performCommand(cmdAttribs, Integer.MAX_VALUE, timeout);
        
        // 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 = 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
        StringBuilder buf = new StringBuilder(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
     * @param timeout The timout amount in milliseconds or no timeout if the value
     *  is zero or less
     * @return the amount of free drive space on the volume
     * @throws IOException if an error occurs
     */
    long freeSpaceUnix(String path, boolean kb, boolean posix, long timeout) throws IOException {
        if (path.length() == 0) {
            throw new IllegalArgumentException("Path must not be empty");
        }

        // 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<String> lines = performCommand(cmdAttribs, 3, timeout);
        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 = 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 = 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 IOExceptionWithCause(
                    "Command line '" + DF + "' did not return numeric data as expected " +
                    "for path '" + path + "'- check path is valid", ex);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Performs the os command.
     *
     * @param cmdAttribs  the command line parameters
     * @param max The maximum limit for the lines returned
     * @param timeout The timout amount in milliseconds or no timeout if the value
     *  is zero or less
     * @return the parsed data
     * @throws IOException if an error occurs
     */
    List<String> performCommand(String[] cmdAttribs, int max, long timeout) 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<String> lines = new ArrayList(20);
        Process proc = null;
        InputStream in = null;
        OutputStream out = null;
        InputStream err = null;
        BufferedReader inr = null;
        try {

            Thread monitor = ThreadMonitor.start(timeout);

            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(Locale.ENGLISH).trim();
                lines.add(line);
                line = inr.readLine();
            }
            
            proc.waitFor();

            ThreadMonitor.stop(monitor);

            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 IOExceptionWithCause(
                    "Command line threw an InterruptedException " +
                    "for command " + Arrays.asList(cmdAttribs) + " timeout=" + timeout, ex);
        } 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);
    }

}