检测应用程序是否是从OS X上的只读文件系统启动的

Question

I want to know whether the user launched our Java-based application from a read-only file system like from a .dmg, so functions like auto-update will be able to show meaningful information instead of aborting with an error. I first thought checking the .app's path would be sufficient (when launched from a .dmg it is something like /Volumes/MyApp 1.2.3/MyApp.app , but this won't work, because the user might have installed the application on a different partition. What other things may I check?

Answer 1

You can use -[NSURL getResourceValue:forKey:error:] with the key NSURLVolumeIsReadOnlyKey . You would apply this to the app bundle URL as returned by [[NSBundle mainBundle] bundleURL] . So:

NSBundle* bundle = [NSBundle mainBundle];
NSURL* bundleURL = bundle.bundleURL;
NSNumber* readOnly;
NSError* error;
if ([bundleURL getResourceValue:&readOnly forKey:NSURLVolumeIsReadOnlyKey error:&error])
{
    BOOL isReadOnly = [readOnly boolValue];
    // act on isReadOnly value
}
else
{
    // Handle error
}

Answer 2

If OSX is POSIX compliant, to determine if filesystem is mounted R/O, You can use statvfs() or fstatvfs() , returned struct statvfs field f_flag should have ST_RDONLY bit set for R/O filesystem.

As it was pointed in comments, check if this information is correctly provided by OS.

JNA and this question may be usefull for Java.

A few more ideas, which may be usefull here ( access() , open() , utime() ).

OS X specific statfs() may be used too, but this function is not portable (Linux and *BSD have slightly different statfs() functions).

Answer 3

You can also check directly from Java whether a certain path points to something within a read-only directory by querying the FileStore associated with your path:

 File classpathRoot = new File(MyClass.class.getClassLoader().getResource("").getPath());
 /* getPath() actually returns a String instead of a Path object, 
  * so we need to take this little detour */
 Path yourAppPath = classpathRoot.toPath();
 boolean isReadOnly = Files.getFileStore(yourAppPath).isReadOnly();