Chmod.java

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 *
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 * modification, are permitted provided that the following conditions
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 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */
 
 
import java.nio.file.*;
import java.nio.file.attribute.*;
import static java.nio.file.attribute.PosixFilePermission.*;
import static java.nio.file.FileVisitResult.*;
import java.io.IOException;
import java.util.*;
 
public class Chmod {
 
    public static Changer compile(String exprs) {
        // minimum is who and operator (u= for example)
        if (exprs.length() < 2)
            throw new IllegalArgumentException("Invalid mode");
 
        // permissions that the changer will add or remove
        final Set<PosixFilePermission> toAdd = new HashSet<PosixFilePermission>();
        final Set<PosixFilePermission> toRemove = new HashSet<PosixFilePermission>();
 
        // iterate over each of expression modes
        for (String expr: exprs.split(",")) {
            // minimum of who and operator
            if (expr.length() < 2)
                throw new IllegalArgumentException("Invalid mode");
 
            int pos = 0;
 
            // who
            boolean u = false;
            boolean g = false;
            boolean o = false;
            boolean done = false;
            for (;;) {
                switch (expr.charAt(pos)) {
                    case 'u' : u = true; break;
                    case 'g' : g = true; break;
                    case 'o' : o = true; break;
                    case 'a' : u = true; g = true; o = true; break;
                    default : done = true;
                }
                if (done)
                    break;
                pos++;
            }
            if (!u && !g && !o)
                throw new IllegalArgumentException("Invalid mode");
 
            // get operator and permissions
            char op = expr.charAt(pos++);
            String mask = (expr.length() == pos) ? "" : expr.substring(pos);
 
            // operator
            boolean add = (op == '+');
            boolean remove = (op == '-');
            boolean assign = (op == '=');
            if (!add && !remove && !assign)
                throw new IllegalArgumentException("Invalid mode");
 
            // who= means remove all
            if (assign && mask.length() == 0) {
                assign = false;
                remove = true;
                mask = "rwx";
            }
 
            // permissions
            boolean r = false;
            boolean w = false;
            boolean x = false;
            for (int i=0; i<mask.length(); i++) {
                switch (mask.charAt(i)) {
                    case 'r' : r = true; break;
                    case 'w' : w = true; break;
                    case 'x' : x = true; break;
                    default:
                        throw new IllegalArgumentException("Invalid mode");
                }
            }
 
            // update permissions set
            if (add) {
                if (u) {
                    if (r) toAdd.add(OWNER_READ);
                    if (w) toAdd.add(OWNER_WRITE);
                    if (x) toAdd.add(OWNER_EXECUTE);
                }
                if (g) {
                    if (r) toAdd.add(GROUP_READ);
                    if (w) toAdd.add(GROUP_WRITE);
                    if (x) toAdd.add(GROUP_EXECUTE);
                }
                if (o) {
                    if (r) toAdd.add(OTHERS_READ);
                    if (w) toAdd.add(OTHERS_WRITE);
                    if (x) toAdd.add(OTHERS_EXECUTE);
                }
            }
            if (remove) {
                if (u) {
                    if (r) toRemove.add(OWNER_READ);
                    if (w) toRemove.add(OWNER_WRITE);
                    if (x) toRemove.add(OWNER_EXECUTE);
                }
                if (g) {
                    if (r) toRemove.add(GROUP_READ);
                    if (w) toRemove.add(GROUP_WRITE);
                    if (x) toRemove.add(GROUP_EXECUTE);
                }
                if (o) {
                    if (r) toRemove.add(OTHERS_READ);
                    if (w) toRemove.add(OTHERS_WRITE);
                    if (x) toRemove.add(OTHERS_EXECUTE);
                }
            }
            if (assign) {
                if (u) {
                    if (r) toAdd.add(OWNER_READ);
                      else toRemove.add(OWNER_READ);
                    if (w) toAdd.add(OWNER_WRITE);
                      else toRemove.add(OWNER_WRITE);
                    if (x) toAdd.add(OWNER_EXECUTE);
                      else toRemove.add(OWNER_EXECUTE);
                }
                if (g) {
                    if (r) toAdd.add(GROUP_READ);
                      else toRemove.add(GROUP_READ);
                    if (w) toAdd.add(GROUP_WRITE);
                      else toRemove.add(GROUP_WRITE);
                    if (x) toAdd.add(GROUP_EXECUTE);
                      else toRemove.add(GROUP_EXECUTE);
                }
                if (o) {
                    if (r) toAdd.add(OTHERS_READ);
                      else toRemove.add(OTHERS_READ);
                    if (w) toAdd.add(OTHERS_WRITE);
                      else toRemove.add(OTHERS_WRITE);
                    if (x) toAdd.add(OTHERS_EXECUTE);
                      else toRemove.add(OTHERS_EXECUTE);
                }
            }
        }
 
        // return changer
        return new Changer() {
            @Override
            public Set<PosixFilePermission> change(Set<PosixFilePermission> perms) {
                perms.addAll(toAdd);
                perms.removeAll(toRemove);
                return perms;
            }
        };
    }
 
    public interface Changer {
        Set<PosixFilePermission> change(Set<PosixFilePermission> perms);
    }
 
    static void chmod(Path file, Changer changer) {
        try {
            Set<PosixFilePermission> perms = Files.getPosixFilePermissions(file);
            Files.setPosixFilePermissions(file, changer.change(perms));
        } catch (IOException x) {
            System.err.println(x);
        }
    }
 
    static class TreeVisitor implements FileVisitor<Path> {
        private final Changer changer;
 
        TreeVisitor(Changer changer) {
            this.changer = changer;
        }
 
        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
            chmod(dir, changer);
            return CONTINUE;
        }
 
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
            chmod(file, changer);
            return CONTINUE;
        }
 
        @Override
        public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
            if (exc != null)
                System.err.println("WARNING: " + exc);
            return CONTINUE;
        }
 
        @Override
        public FileVisitResult visitFileFailed(Path file, IOException exc) {
            System.err.println("WARNING: " + exc);
            return CONTINUE;
        }
    }
 
    static void usage() {
        System.err.println("java Chmod [-R] symbolic-mode-list file...");
        System.exit(-1);
    }
 
    public static void main(String[] args) throws IOException {
        if (args.length < 2)
            usage();
        int argi = 0;
        int maxDepth = 0;
        if (args[argi].equals("-R")) {
            if (args.length < 3)
                usage();
            argi++;
            maxDepth = Integer.MAX_VALUE;
        }
 
        // compile the symbolic mode expressions
        Changer changer = compile(args[argi++]);
        TreeVisitor visitor = new TreeVisitor(changer);
 
        Set<FileVisitOption> opts = Collections.emptySet();
        while (argi < args.length) {
            Path file = Paths.get(args[argi]);
            Files.walkFileTree(file, opts, maxDepth, visitor);
            argi++;
        }
    }
}