Operating systems that implement the + * POSIX family of standards commonly use file systems that have a + * file owner, group-owner, and related access + * permissions. This file attribute view provides read and write access + * to these attributes. + * + *
The {@link #readAttributes() readAttributes} method is used to read the + * file's attributes. The file {@link PosixFileAttributes#owner() owner} is + * represented by a {@link UserPrincipal} that is the identity of the file owner + * for the purposes of access control. The {@link PosixFileAttributes#group() + * group-owner}, represented by a {@link GroupPrincipal}, is the identity of the + * group owner, where a group is an identity created for administrative purposes + * so as to determine the access rights for the members of the group. + * + *
The {@link PosixFileAttributes#permissions() permissions} attribute is a + * set of access permissions. This file attribute view provides access to the nine + * permission defined by the {@link PosixFilePermission} class. + * These nine permission bits determine the read, write, and + * execute access for the file owner, group, and others (others + * meaning identities other than the owner and members of the group). Some + * operating systems and file systems may provide additional permission bits + * but access to these other bits is not defined by this class in this release. + * + *
Usage Example: + * Suppose we need to print out the owner and access permissions of a file: + *
+ * FileRef file = ...
+ * PosixFileAttributes attrs = file.newFileAttributeView(PosixFileAttributeView.class)
+ * .readAttributes();
+ * System.out.format("%s %s%n",
+ * attrs.owner().getName(),
+ * PosixFilePermissions.toString(attrs.permissions()));
+ *
+ *
+ * Where dynamic access to file attributes is required, the attributes + * supported by this attribute view are as defined by {@link + * BasicFileAttributeView} and {@link FileOwnerAttributeView}, and in addition, + * the following attributes are supported: + *
+ *+ * + *+ *
+ *+ * + *Name + *Type + *+ * + *"permissions" + *{@link Set}<{@link PosixFilePermission}> + *+ * + *"group" + *{@link GroupPrincipal} + *
The {@link #getAttribute getAttribute} or {@link + * #readAttributes(String,String[]) readAttributes(String,String[])} methods may + * be used to read any of these attributes, or any of the attributes defined by + * {@link BasicFileAttributeView} as if by invoking the {@link #readAttributes + * readAttributes()} method. + * + *
The {@link #setAttribute setAttribute} method may be used to update the + * file's last modified time, last access time or create time attributes as + * defined by {@link BasicFileAttributeView}. It may also be used to update + * the permissions, owner, or group-owner as if by invoking the {@link + * #setPermissions setPermissions}, {@link #setOwner setOwner}, and {@link + * #setGroup setGroup} methods respectively. + * + *
Implementations supporting this attribute view may also support setting + * the initial permissions when creating a file or directory. The + * initial permissions are provided to the {@link Path#createFile createFile} + * or {@link Path#createDirectory createDirectory} methods as a {@link + * FileAttribute} with {@link FileAttribute#name name} {@code "posix:permissions"} + * and a {@link FileAttribute#value value} that is the set of permissions. The + * following example uses the {@link PosixFilePermissions#asFileAttribute + * asFileAttribute} method to construct a {@code FileAttribute} when creating a + * file: + * + *
+ * Path path = ... + * Set<PosixFilePermission> perms = + * EnumSet.of(OWNER_READ, OWNER_WRITE, OWNER_EXECUTE, GROUP_READ); + * path.createFile(PosixFilePermissions.asFileAttribute(perms)); + *+ * + *
When the access permissions are set at file creation time then the actual
+ * value of the permissions may differ that the value of the attribute object.
+ * The reasons for this are implementation specific. On UNIX systems, for
+ * example, a process has a umask that impacts the permission bits
+ * of newly created files. Where an implementation supports the setting of
+ * the access permissions, and the underlying file system supports access
+ * permissions, then it is required that the value of the actual access
+ * permissions will be equal or less than the value of the attribute
+ * provided to the {@link java.nio.file.Path#createFile createFile} or
+ * {@link java.nio.file.Path#createDirectory createDirectory} methods. In
+ * other words, the file may be more secure than requested.
+ *
+ * @since 1.7
+ *
+ * @see Attributes#readPosixFileAttributes
+ */
+
+public interface PosixFileAttributeView
+ extends BasicFileAttributeView, FileOwnerAttributeView
+{
+ /**
+ * Returns the name of the attribute view. Attribute views of this type
+ * have the name {@code "posix"}.
+ */
+ @Override
+ String name();
+
+ /**
+ * @throws IOException {@inheritDoc}
+ * @throws SecurityException
+ * In the case of the default provider, a security manager is
+ * installed, and it denies {@link RuntimePermission}("accessUserInformation")
+ * or its {@link SecurityManager#checkRead(String) checkRead} method
+ * denies read access to the file.
+ */
+ @Override
+ PosixFileAttributes readAttributes() throws IOException;
+
+ /**
+ * Updates the file permissions.
+ *
+ * @param perms
+ * The new set of permissions
+ *
+ * @throws ClassCastException
+ * If the sets contains elements that are not of type {@code
+ * PosixFilePermission}
+ * @throws IOException
+ * If an I/O error occurs
+ * @throws SecurityException
+ * In the case of the default provider, a security manager is
+ * installed, and it denies {@link RuntimePermission}("accessUserInformation")
+ * or its {@link SecurityManager#checkWrite(String) checkWrite}
+ * method denies write access to the file.
+ */
+ void setPermissions(Set