In Java, we can use the NIO createFile() to assign file permission during file creation.
Files.java
package java.nio.file;
public static Path createFile(Path path, FileAttribute<?>... attrs)
throws IOExceptionBut, the createFile() fails to assign the group writes file permission to a file on the Unix system?
Path path = Paths.get("/home/favtuts/test/runme.sh");
Set<PosixFilePermission> perms =
PosixFilePermissions.fromString("rwxrwxrwx");
Files.createFile(path, PosixFilePermissions.asFileAttribute(perms));$ ls -lsah
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 16:18 runme.shThe Answer
In Java, assign file permission during file creation, first create the file, and assign its file permission later.
Path path = Paths.get("/home/favtuts/test/runme.sh");
Files.createFile(path);
Files.setPosixFilePermissions(path,
PosixFilePermissions.fromString("rwxrwxrwx"));1. PosixFilePermission.GROUP_WRITE
This example tries to assign a 777 file permission during file creation.
CreateFile1.java
package com.favtuts.io.temp;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.EnumSet;
import java.util.Set;
public class CreateFile {
public static void main(String[] args) {
try {
Path path = Paths.get("/home/tvt/workspace/favtuts/temp/test1.log");
Set<PosixFilePermission> perms = EnumSet.of(
PosixFilePermission.OWNER_READ,
PosixFilePermission.OWNER_WRITE,
PosixFilePermission.OWNER_EXECUTE,
PosixFilePermission.GROUP_READ,
PosixFilePermission.GROUP_WRITE,
PosixFilePermission.GROUP_EXECUTE,
PosixFilePermission.OTHERS_READ,
PosixFilePermission.OTHERS_WRITE,
PosixFilePermission.OTHERS_EXECUTE);
Files.createFile(path, PosixFilePermissions.asFileAttribute(perms));
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output, the createFile() failed to assign the group writes file permission?
$ ls -lsah
total 8.0K
4.0K drwxr-xr-x 2 favtuts favtuts 4.0K Jul 20 16:18 .
4.0K drwxr-xr-x 42 favtuts favtuts 4.0K Jul 20 16:06 ..
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 16:18 test1.log2. PosixFilePermissions.fromString(“rwxrwxrwx”)
This example uses the PosixFilePermissions.fromString to assign the 777 file permission during file creation.
CreateTempFile2.java
package com.favtuts.io.temp;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.Set;
public class CreateTempFile2 {
public static void main(String[] args) {
try {
Path path = Paths.get("/home/tvt/workspace/favtuts/temp/test2.log");
Set<PosixFilePermission> perms =
PosixFilePermissions.fromString("rwxrwxrwx");
Files.createFile(path, PosixFilePermissions.asFileAttribute(perms));
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output – The result is the same; the createFile() is still unable to assign the group writes file permission?
$ ls -lsah
total 8.0K
4.0K drwxr-xr-x 2 favtuts favtuts 4.0K Jul 20 16:22 .
4.0K drwxr-xr-x 42 favtuts favtuts 4.0K Jul 20 16:06 ..
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 16:18 test1.log
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 16:22 test2.log3. Create First, Assign Later.
The file permission may be “override by the UNIX umask” (not sure) during the file creation.
To fix it or get the desire 777 file permission, we have to create a file first and assign the file permission later.
CreateTempFile3.java
package com.favtuts.io.temp;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.Set;
public class CreateTempFile3 {
public static void main(String[] args) {
try {
Path path = Paths.get("/home/tvt/workspace/favtuts/temp/test3.log");
/*Set<PosixFilePermission> perms = EnumSet.of(
PosixFilePermission.OWNER_READ,
PosixFilePermission.OWNER_WRITE,
PosixFilePermission.OWNER_EXECUTE,
PosixFilePermission.GROUP_READ,
PosixFilePermission.GROUP_WRITE,
PosixFilePermission.GROUP_EXECUTE,
PosixFilePermission.OTHERS_READ,
PosixFilePermission.OTHERS_WRITE,
PosixFilePermission.OTHERS_EXECUTE
);*/
Set<PosixFilePermission> perms =
PosixFilePermissions.fromString("rwxrwxrwx");
Files.createFile(path);
Files.setPosixFilePermissions(path, perms);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output, finally, we can assign the group writes file permission to a file.
$ ls -lsah
total 8.0K
4.0K drwxr-xr-x 2 favtuts favtuts 4.0K Jul 20 16:27 .
4.0K drwxr-xr-x 42 favtuts favtuts 4.0K Jul 20 16:06 ..
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 16:18 test1.log
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 16:22 test2.log
0 -rwxrwxrwx 1 favtuts favtuts 0 Jul 20 16:27 test3.logDownload Source Code
$ git clone https://github.com/favtuts/java-core-tutorials-examples
$ cd java-io/temp