Advanced Comparison Features

In addition to the already mentioned possibilities to compare file system objects with each other, Sync Checker offers extended functions for specific use cases: One or even both folder hierarchies to compare don’t need to be accessible “live”, but can also have been scanned at an earlier point in time or on a different Mac. Such an archived offline scan can serve as alternative data source for a sync check.

Moreover, it is possible to exclude objects from the comparison in advance. The criterion for exclusion can be the name of the object or the relative folder path where the object resides. We call this feature an ignore list.

Using an Archived Scan as Data Source

An offline scan can take on the role of real objects during a sync check. So for the comparison, not the file system objects currently available, but rather archived data about file system objects will be used. This is especially useful in two cases:

  1. If you like to observe how a specific folder hierarchy changes over a long period of time: You can use an archived scan to capture snapshots of older states. This makes it possible to compare a folder with itself, but at different times.

  2. If you like to compare similar folders on two different computers without using a network and without connecting the two systems otherwise: Create a scan on the first computer, transfer the scan file to the second computer, and use it as a reference source.

An offline scan file of Sync Checker contains the metadata of all file system objects that reside in a given folder on the same volume. The actual contents of the files are not stored, so an archived scan uses less storage space than the data that was scanned.

It would not be practical for later use of an offline scan if the content depended on the access permissions of the user who created the file. For this reason, the scan attempts to capture all existing file system objects. Administrative rights are necessary to do that.

Even if an offline scan does not contain the complete data, it still contains information about the existence of files and folders with specific names and specific sizes, affecting multiple users. This may affect the privacy of the respective file owners. An offline scan may contain critical data and should be protected against unauthorized access.

To create an offline scan file, perform the following steps:

  1. Select the menu item Tools > Scan Folder for Offline Check or press the key combination ⌘ + 0.
  2. In the subsequent file dialog, select the folder that should be scanned. This can be an entire volume. The search will always be restricted to a single volume.
  3. macOS asks for confirmation of administrative permission. After that, all objects in the specified folder will be scanned.
  4. The operation can be canceled any time by clicking the button Stop. When the scan has been completed, you will be asked for name and location of the file that should be created.

Saving this file may take some additional time. Such offline archives use the file extension scos (Sync Checker Offline Scan). Please store the file at a secure place in order to guarantee protection of privacy.

Using an Offline Scan

A created “scos” file can be specified as data source for a Sync Checker comparison in one or both fields of the control window. So if you click the Select … button, you can also choose an offline scan file, or you could drag a file into the upper or lower field of the window using the mouse. As indicator that not a real folder but an archived snapshot will be used as data source, a notice of the pattern Folder …, scanned at … will appear below the respective field.

An additional note indicates whether an offline scan is used as data source.
An additional note indicates whether an offline scan is used as data source.

The archived snapshot can replace the real file system objects almost completely during a comparison. Because the archive only contains metadata but not the full contents, and perhaps different user accounts with different access permissions are used during creation time and use time, the following restrictions will apply:

The report window of Sync Checker will indicate explicitly if such restrictions apply.

Working with Ignore Lists

For a Sync Check, it may be useful not only to hide certain comparison criteria from the final results, but to exclude certain files or folders in general. This is possible if Sync Checker can identify the objects that should be blocked by their names. You can use ignore lists defining objects not to be compared by identifying them as follows:

The following rules apply to all the possible criteria:

Creating an Ignore List

You can create customized ignore lists that use the name condition rules to identify objects that were outlined in the previous section. The lists are saved into files with the name extension scil (Sync Checker Ignore List). Such files are managed by Sync Checker as common macOS document files. Autosave is fully supported. To create a new file, perform the following steps:

  1. Select the menu item File > New Ignore List.
  2. A document window will appear. Enter a descriptive comment for this ignore list into the field Description that indicates which purpose the list should serve later. Sync Checker will show this notice when you are using an ignore list during a sync check.
  3. Use the buttons marked with + below the table to add match criteria to the search list.
You can create ignore lists yourself.
You can create ignore lists yourself.

The button Folder hierarchy adds a path as entry which will later be evaluated as relative path directly within the top folder of the sync check. It does not matter if the path begins with a slash (/). You can enter the path manually, but you can also use the general file navigation dialog of macOS via the button Select…. The second Select… button specifies the relativ anchor point for choosing the actual path. This second path won’t become part of the ignore list. It only helps you to choose paths relative to other paths by mouse click. It does not make sense to select different anchor points for relative paths within a single ignore list, however.

The button Name-based adds an entry which only takes the name of a file system object as match criterion. A pop-up button allows you to choose one of the match conditions mentioned earlier.

Add entries from other file… can be used to combine entries from multiple ignore lists.

One or more entries can be removed with the button . Before you can actually use an ignore list, you must save it into a named file.

Using Custom Ignore Lists

The main window of Sync Checker contains a pop-up button which controls whether an ignore list should be used. By default, the setting Check all file system objects is active, indicating that no ignore list is in use. You can choose a custom ignore list as follows:

  1. Use the mentioned pop-up button to select the menu item Don’t check files in ignore list:.
  2. A file navigation dialog will appear. Open the “scil” file you have created previously.
  3. Name and description of the ignore list will now be shown next to and below the button, respectively. You can disable the ignore list any time or choose a different one with the Select … button.

When starting a sync check or quick test afterwards, your ignore list will be active.

Using Built-in Ignore Lists

Sync Checker also provides useful ignore lists for typical use cases which are built in already. You can also choose one of them via the menu of the pop-up button. These ignore lists are document in the following sections.

Built-in ignore lists are available for typical use cases
Built-in ignore lists are available for typical use cases
Ignore .DS_Store files

When a user opens a window displaying a folder in the Finder and this user has write permission for the folder, the settings of the Finder window for this folder are saved into a hidden file named .DS_Store (Desktop Services Store) within that folder. When the folder is opened later again, the data in this file makes sure that the same view preferences will become active again. This includes size and position of the window, the positions of all icons (in icon view mode), the sort order (in list view mode), color settings, etc.

In most cases it won’t be of interest to include these view preferences of the Finder into a sync check. The ignore list named Ignore .DS_Store files can be activated to do that.

Ignore macOS work files

If you compare two operating system volumes of the same macOS version with each other (or use an offline scan to compare a single volume with itself at different points in time), you may often be interested in files that have changed due to user interaction, but not in changes that essentially occur “anyway” by the pure operation of macOS. A practical ignore list for this case has been prepared under the title Ignore macOS work files. Because it is strongly based on relative folder paths, it will only work correctly if you actually compare two entire macOS volumes with each other. This ignore list will exclude the following items:

Ignore unique macOS files

When comparing two macOS volumes with each other that are based on different installation instances, you will find several mismatches for files which are unique per installation, for example files that contain the internal security keys of the operating system. The ignore list Ignore unique macOS files considers such objects in addition to the work files mentioned in the previous section. In particular, the following items are added to the ignore list: