How do I programmatically change file permissions?

Question

In Java, I\'m dynamically creating a set of files and I\'d like to change the file permissions on these files on a linux/unix file system. I\'d like to be able to execute t

Answer 1

Apache ant chmod (not very elegant, adding it for completeness) credit shared with @msorsky

    Chmod chmod = new Chmod();
    chmod.setProject(new Project());
    FileSet mySet = new FileSet();
    mySet.setDir(new File("/my/path"));
    mySet.setIncludes("**");
    chmod.addFileset(mySet);
    chmod.setPerm("+w");
    chmod.setType(new FileDirBoth());
    chmod.execute();

Answer 2

for windows 7 with nio 2.0:

public static void main(String[] args) throws IOException
{
    Path file = Paths.get("c:/touch.txt");
    AclFileAttributeView aclAttr = Files.getFileAttributeView(file, AclFileAttributeView.class);
    System.out.println(aclAttr.getOwner());
    for(AclEntry aclEntry : aclAttr.getAcl()){
        System.out.println(aclEntry);
    }
    System.out.println();

    UserPrincipalLookupService upls = file.getFileSystem().getUserPrincipalLookupService();
    UserPrincipal user = upls.lookupPrincipalByName(System.getProperty("user.name"));
    AclEntry.Builder builder = AclEntry.newBuilder();       
    builder.setPermissions( EnumSet.of(AclEntryPermission.READ_DATA, AclEntryPermission.EXECUTE, 
            AclEntryPermission.READ_ACL, AclEntryPermission.READ_ATTRIBUTES, AclEntryPermission.READ_NAMED_ATTRS,
            AclEntryPermission.WRITE_ACL, AclEntryPermission.DELETE
    ));
    builder.setPrincipal(user);
    builder.setType(AclEntryType.ALLOW);
    aclAttr.setAcl(Collections.singletonList(builder.build()));
}

Answer 3

If you want to set 777 permission to your created file than you can use the following method:

public void setPermission(File file) throws IOException{
    Set<PosixFilePermission> perms = new HashSet<>();
    perms.add(PosixFilePermission.OWNER_READ);
    perms.add(PosixFilePermission.OWNER_WRITE);
    perms.add(PosixFilePermission.OWNER_EXECUTE);

    perms.add(PosixFilePermission.OTHERS_READ);
    perms.add(PosixFilePermission.OTHERS_WRITE);
    perms.add(PosixFilePermission.OTHERS_EXECUTE);

    perms.add(PosixFilePermission.GROUP_READ);
    perms.add(PosixFilePermission.GROUP_WRITE);
    perms.add(PosixFilePermission.GROUP_EXECUTE);

    Files.setPosixFilePermissions(file.toPath(), perms);
}

Answer 4

Just to update this answer unless anyone comes across this later, since JDK 6 you can use

File file = new File('/directory/to/file');
file.setWritable(boolean);
file.setReadable(boolean);
file.setExecutable(boolean);

you can find the documentation on Oracle File(Java Platform SE 7). Bear in mind that these commands only work if the current working user has ownership or write access to that file. I am aware that OP wanted chmod type access for more intricate user configuration. these will set the option across the board for all users.

Answer 5

You can use the methods of the File class: http://docs.oracle.com/javase/7/docs/api/java/io/File.html

Answer 6

In addition to erickson's suggestions, there's also jna, which allows you to call native libraries without using jni. It's shockingly easy to use, and I've used it on a couple of projects with great success.

The only caveat is that it's slower than jni, so if you're doing this to a very large number of files that might be an issue for you.

(Editing to add example)

Here's a complete jna chmod example:

import com.sun.jna.Library;
import com.sun.jna.Native;

public class Main {
    private static CLibrary libc = (CLibrary) Native.loadLibrary("c", CLibrary.class);

    public static void main(String[] args) {
        libc.chmod("/path/to/file", 0755);
    }
}

interface CLibrary extends Library {
    public int chmod(String path, int mode);
}