NSFileManager & NSFilePosixPermissions

Question

I want to use the octal permissions (used for chmod) for NSFilePosixPermissions. Here is what I did now:

NSFileManager *manager = [NSFileManager defaultManager];
NSDictionary *attributes;

[attributes setValue:[NSString stringWithFormat:@"%d", 0777] 
             forKey:@"NSFilePosixPermissions"]; // chmod permissions 777
[manager setAttributes:attributes ofItemAtPath:@"/Users/lucky/Desktop/script" error:nil];

I get no error, but when I check the result with "ls -o" the permission are't -rwxrwxrwx.

What's wrong? Thanks for help.

Answer 1

First, NSFilePosixPermissions is the name of a constant. Its value may also be the same, but that’s not guaranteed. The value of the NSFilePosixPermissions constant could change between framework releases, e. g. from @"NSFilePosixPermissions" to @"posixPermisions". This would break your code. The right way is to use the constant as NSFilePosixPermissions, not @"NSFilePosixPermissions".

Also, the NSFilePosixPermissions reference says about NSFilePosixPermisions:

The corresponding value is an NSNumber object. Use the shortValue method to retrieve the integer value for the permissions.

The proper way to set POSIX permissions is:

// chmod permissions 777

// Swift
attributes[NSFilePosixPermissions] = 0o777

// Objective-C
[attributes setValue:[NSNumber numberWithShort:0777] 
             forKey:NSFilePosixPermissions];

Answer 2

Solution in Swift 3

let fm = FileManager.default

var attributes = [FileAttributeKey : Any]()
attributes[.posixPermissions] = 0o777
do {
    try fm.setAttributes(attributes, ofItemAtPath: path.path)
}catch let error {
    print("Permissions error: ", error)
}