[ Java 代碼範本 ] JDK 7 » File Attribute » Using PosixFileAttributes

Source From Here 
Preface 
在 Linux/Unix 中你可以透過 chmod 命令來變更檔案的屬性, 在 JDK7 之後提供了類別 PosixFileAttributes 讓你讀取與設定檔案的屬性. 

Sample Code 
下面的範例代碼讓你從命令列參數輸入一個檔案的路徑, 程式會讀出該檔案的屬性並重置該檔案屬性為 0644: 

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1. package john.nio.file.attribute;  
2.   
3. import java.nio.file.Files;  
4. import java.nio.file.Path;  
5. import java.nio.file.Paths;  
6. import java.nio.file.attribute.PosixFileAttributes;  
7. import java.nio.file.attribute.PosixFilePermission;  
8. import static java.nio.file.attribute.PosixFilePermission.*;  
9. import java.nio.file.attribute.PosixFilePermissions;  
10. import java.util.Set;  
11.   
12. public class PosixFileAttributesDemo {  
13.     public static void main(String args[]) throws Exception  
14.     {  
15.         if(args.length==0)   
16.         {  
17.             System.out.printf("\t[Info] Usage: Arg1=File Path\n");  
18.             return;  
19.         }  
20.         Path profile = Paths.get(args[0]);  
21.   
22.         PosixFileAttributes attrs = Files.readAttributes(profile,  
23.             PosixFileAttributes.class);  
24.   
25.         Set posixPermissions = attrs.permissions();        
26.   
27.         String owner = attrs.owner().getName();  
28.         String perms = PosixFilePermissions.toString(posixPermissions);  
29.         System.out.printf("\t[Info] File=%s with permission: ", args[0]);  
30.         System.out.format("%s %s%n", owner, perms);  
31.   
32.         posixPermissions.clear();                 
33.         posixPermissions.add(OWNER_READ);  
34.         posixPermissions.add(OWNER_WRITE);  
35.         posixPermissions.add(GROUP_READ);  
36.         posixPermissions.add(OTHERS_READ);  
37.         System.out.printf("\t[Info] Reset permission to: %s\n", PosixFilePermissions.toString(posixPermissions));  
38.         Files.setPosixFilePermissions(profile, posixPermissions);  
39.     }  
40. }  

上面代碼透過 enum PosixFilePermission 進行屬性設定: 
 

Execution 
假設你將上面代碼封裝到 Test.jar 中, 並設定 main-class 為 PosixFileAttributesDemo, 下面為執行過程: 

$ chmod 777 test.py
$ ls -hl test.py
-rwxrwxrwx. 1 root root 890 Jan 1 13:13 test.py
$ java -jar Test.jar test.py # 執行我們的範例代碼
[Info] File=test.py with permission: root rwxrwxrwx
[Info] Reset permission to: rw-r-----
$ ls -hl test.py
-rw-r-----. 1 root root 890 Jan 1 13:13 test.py

Supplement 
* Stackoverflow - How can I set the umask from within java? 
* Linux Files and File Permission