javalinuxlastaccesstime

Is it necessary to enable "atime" in /etc/fstab to get the correct last accessed time in java?

I can get the last accessed time by using the below code.

public Date getLastAccessTime(String filePath) throws IOException {
    File f = new File(filePath);
    BasicFileAttributes basicFileAttributes = Files.getFileAttributeView(
        f.toPath(),
        BasicFileAttributeView.class).readAttributes();
    Date accessTime = new Date(basicFileAttributes.lastAccessTime().toMillis());
    return accessTime;
}

But in my linux system, it's configured as "relatime" in /etc/fstab.

Is it necessary to enable "atime" in /etc/fstab to get exact Last Accessed Time?

Solution

  • Is it necessary to enable "atime" in /etc/fstab to get exact Last Accessed Time?

    Short answer: Yes

    On Linux the JDK uses the sys_stat64() syscall to retrieve information about file. If the kernel does not update the st_atime field when the file is accessed then Java can't have this information.

    The default behavior of the Linux kernel regarding the st_atime updating policy has been changed by Linux 2.6.30. relatime is now the default dehavior. It means that st_atime is updated only when st_mtime or st_ctime is updated but not when the file is accessed. If you want the old behavior you can use strictatime. See the mount man page for more information (search for atime, noatime, relatime, strictatime).