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It is easy to overwrite a file in macOS that you want to keep unchanged. One way to avoid this: select the file in the Finder, choose File> Get Info, and then select the Locked check box. A lock icon appears on the icon or preview of the file. Locking a file does not prevent it from being trashed, but you can not empty the trash with a locked file.

File privileges and locking files

The locked state is prior to Mac OS X and seems to have been postponed for compatibility with OS X and has never been thought. The locked property does not appear to be stored with the permissions package and access control records. This is part of the metadata of a file or directory in macOS. Therefore, when you lock a file, it only affects the instance of the file on a particular Mac.

Indicating how much Apple really did not pay attention to this feature, if a bolted file is mapped to iCloud and then edited on another computer, the file on the original Mac is overwritten and left open. Jeff has tried to use a file-level advantage setting for the file, setting his property permissions to Read-Only. Although it has been superseded by the file owner (as dictated by a framework-level client) and anyone with macOS administrator privileges.

To change privileges on a file: 

1. Select the file in the Finder.
2. Choose File> Get Info.
3. If it does not appear, expand the Sharing and Permissions section.
4. If the Name field has an account name followed by “(Me)”, you can use the shortcut menus next to each entry under Name and change the Privilege context menu. In this case, just change the one next to “your name (Me)” to Read Only.

How to configure default applications to open all files of a format type in Mac OS X

This approach will change the default application universally for all files in a specific format. For example, you can use it to define all PNG files to open in Skitch, all TXT files to open with Text Wrangler, and any ZIP files to open with The Unarchiver.

1. In the Mac file system, select a file of the general format type for which you want to change the default application.
2. Pull down the “File” menu and choose “Get Info” (or press Command-i) to access the Get Info window.
3. Click the “Open with:” submenu, then click the context menu and select the new application to associate all the files of this type of format.
4. Click the “Change All” button and confirm the change when requested.
5. Close the Read Information option, repeat as necessary for other types of file formats.