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 the Java equivalent of chmod  Is that possible Java 5  If so  how   I know in Java 6 the File object has setReadable   setWritable   methods  I also know I could make a system call to do this  but I d like to avoid that if possible

User · Answer

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

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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

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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

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import java io File  import java io IOException  import java nio file Files  import java nio file Path  import java nio file Paths  import java nio file attribute FileAttribute  import java nio file attribute PosixFileAttributes  import java nio file attribute PosixFilePermission  import java nio file attribute PosixFilePermissions  import java util Set   public class FileAndDirectory1       public static void main String   args                     File file   new File  quot fileTest1 txt quot            System out println file getAbsoluteFile             try                 file createNewFile                if  file exists                                    PosixFilePermission is an enum class  PosixFilePermissions is a final class                                    create file permissions from string                 Set lt PosixFilePermission gt  filePermissions   PosixFilePermissions fromString  quot --------- quot     quot rwxrwxrwx quot                       FileAttribute lt   gt  permissions   PosixFilePermissions asFileAttribute filePermissions                   Files createFile file toPath    permissions                      printing the permissions associated with the file                 System out println  quot Executable   quot    file canExecute                     System out println  quot Readable   quot    file canRead                     System out println  quot Writable   quot   file canWrite                      file setExecutable true                   file setReadable true                   file setWritable true                             else                                 modify permissions                                    get the permission using file attributes                 Set lt PosixFilePermission gt  perms   Files readAttributes file toPath    PosixFileAttributes class  permissions                    perms remove PosixFilePermission OWNER WRITE                    perms add PosixFilePermission OWNER READ                   perms add PosixFilePermission OWNER EXECUTE                   perms add PosixFilePermission GROUP WRITE                   perms add PosixFilePermission GROUP READ                   perms add PosixFilePermission GROUP EXECUTE                   perms add PosixFilePermission OTHERS WRITE                   perms add PosixFilePermission OTHERS READ                   perms add PosixFilePermission OTHERS EXECUTE                   Files setPosixFilePermissions file toPath    perms                    System out println  quot Executable   quot    file canExecute                     System out println  quot Readable   quot    file canRead                     System out println  quot Writable   quot   file canWrite                      file delete                            catch  IOException e                e printStackTrace                      Path path   Paths get String valueOf file            System out println path

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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 lt PosixFilePermission gt  perms   new HashSet lt  gt         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

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There is an example class on Oracle Docs which works very much similar to the UNIX chmod  It works with java se 7  though

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Full control over file attributes is available in Java 7  as part of the  new  New IO facility  NIO 2   For example  POSIX permissions can be set on an existing file with setPosixFilePermissions    or atomically at file creation with methods like createFile   or newByteChannel     You can create a set of permissions using EnumSet of    but the helper method PosixFilePermissions fromString   will uses a conventional format that will be more readable to many developers  For APIs that accept a FileAttribute  you can wrap the set of permissions with with PosixFilePermissions asFileAttribute     Set lt PosixFilePermission gt  ownerWritable   PosixFilePermissions fromString  rw-r--r--    FileAttribute lt   gt  permissions   PosixFilePermissions asFileAttribute ownerWritable   Files createFile path  permissions     In earlier versions of Java  using native code of your own  or exec-ing command-line utilities are common approaches

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Prior to Java 6  there is no support of file permission update at Java level  You have to implement your own native method or call Runtime exec   to execute OS level command such as chmod   Starting from Java 6  you can useFile setReadable   File setWritable   File setExecutable   to set file permissions  But it doesn t simulate the POSIX file system which allows to set permission for different users  File setXXX   only allows to set permission for owner and everyone else   Starting from Java 7  POSIX file permission is introduced  You can set file permissions like what you have done on  nix systems  The syntax is    File file   new File  file4 txt    file createNewFile     Set lt PosixFilePermission gt  perms   new HashSet lt  gt     perms add PosixFilePermission OWNER READ   perms add PosixFilePermission OWNER WRITE    Files setPosixFilePermissions file toPath    perms     This method can only be used on POSIX file system  this means you cannot call it on Windows system   For details on file permission management  recommend you to read this post

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

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simple java code  for change file permission in java       String path  D   file  read txt           File file new File path           if  file exists                  System out println  read   file canRead                 System out println  write   file canWrite                 System out println  Execute   file canExecute                 file setReadOnly                     Reference   how to change file permission in java

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For Windows 7 with NIO 2  public static void main String   args  throws IOException       Path file   Paths get  quot c  touch txt quot        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  quot user name quot         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

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for Oralce Java 6   private static int chmod String filename  int mode        try           Class lt   gt  fspClass   Class forName  java util prefs FileSystemPreferences            Method chmodMethod   fspClass getDeclaredMethod  chmod   String class  Integer TYPE           chmodMethod setAccessible true           return  Integer chmodMethod invoke null  filename  mode         catch  Throwable ex            return -1            works under solaris linux

[java] How do I programmatically change file permissions?

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