如何使用Java代码设置rwxrwxrwx权限？

Question

Hello at all the community ! I'm tring to change the frequency clock of the cpu but i'm a problem. To change the clock frequency i need to modify the file scaling_max_freq (/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq) but... this file has these permissions: rw-rw---- so with a file manager with root permissions i change rw-rw---- to rwxrwxrwx and all works fine (in this mode i can set the cpu frequency, with rw-rw---- permissions i can not do it). The code that i use for set the clock is this

public static boolean setClock(String filePath, String value) {
    try {
        fileWriter = new FileWriter(filePath);
        fileWriter.write(value);
        fileWriter.close();
    } catch (IOException e) {
    // TODO Auto-generated catch block
        e.printStackTrace();
        return false;
    }
    return true;
}

Now the question is: how can i set the permission for the file with code? how can i set rwxrwxrwx for the file scaling_max_freq? Thanks in advance.

Answer 1

You can't using Java 6.

You can using Java 7:

Files.setPosixAttributes(path, EnumSet.allOf(PosixFilePermission.class));

Now the question is why. You normally should not do it at all. Especially on a sysfs file.

Answer 2

您可以尝试使用运行时，但正如fge所述，您可能无法在文件系统上设置权限。