On a Mac computer, file names that contain a question mark “?” indicate special system files. These files play an important role in how the Mac operating system runs. Understanding what these files are and why they appear can help users manage their Mac more effectively.
Special system files with question marks allow Mac OS to store metadata and settings on the disk. They are usually hidden from users, but sometimes become visible. Knowing what they are takes away the mystery, and allows users to maintain their Mac properly. This article will provide an overview of these special files, explain how they impact users, and offer tips for managing them.
Hidden System Files
On the Mac operating system, any file that starts with a period “.” is considered a hidden file. These types of files are usually system files and resources that macOS uses to operate properly. The period at the beginning of the filename prevents the average user from easily finding or accessing these files in the Finder app.
In addition to starting with a period, some critical system files also have a question mark “?” appended to the end of the filename. According to Apple’s developer documentation, “The presence of this character flags the file as being a potential problem if deleted, for example a shared library file.”
So the question mark provides an additional layer of protection for vital system resources, warning users against tampering with or deleting these files which could cause problems. It acts as a caution flag, especially for users who choose to view hidden files in the Finder.
Special Meanings
The question mark in file names on Macs often indicates that it is a hidden system file. Some common examples include:
.DS_Store – Stores custom attributes of folders like the position of icons. Created automatically by macOS to remember folder view settings. Can sometimes cause issues when copying folders or pushing to Git.
.Trashes – Tracks files that have been moved to the Trash. Allows files to be retrieved from the Trash if needed.
.Spotlight-V100 – Contains data to speed up Spotlight searches. Automatically indexed by macOS.
These hidden system files allow macOS to function more smoothly, but aren’t needed by the user directly. They can sometimes cause issues when sharing files across platforms.
Impacts on Users
The question mark files that Mac OS creates can potentially cause problems for users in certain situations. One common issue is that the hidden files may interfere with syncing files across devices or to cloud storage. For example, if you have file syncing set up between your Mac and an external hard drive, you may find that the question mark files get synced over as well, taking up unnecessary space on the external drive.
According to an Apple Support article, “If your Mac starts up to a question mark” [1], syncing the question mark files can also lead to warnings about not being able to empty the trash on the external drive. This is because the hidden OS files get synced to the external drive and then can’t be deleted like normal files when the drive is disconnected from the Mac.
In addition, some users report seeing many unwanted question mark files show up on external drives that are used across both Mac and Windows devices [2]. Since Windows does not create these hidden files, they can appear confusing and problematic when external drives are accessed from a Windows PC.
Overall, while useful for the Mac OS, these hidden question mark files can potentially lead to syncing problems, unwarranted space usage, and file clutter on external drives used across multiple devices.
Showing Hidden Files
Mac OS hides certain system files and folders by default to prevent accidental deletion or manipulation. These hidden files are prefixed with a period or dot (.) making them invisible in Finder. To reveal these hidden files, there are a couple methods using Terminal or Finder:
In Finder:
- Open the folder where you want to view hidden files
- Press Command + Shift + . (period key)
- Hidden files and folders will now be visible
- To hide these files again, press Command + Shift + .
In Terminal:
- Open Terminal
- Type
defaults write com.apple.finder AppleShowAllFiles YESand press enter - Restart Finder by holding Option and right-clicking on the Finder icon in the Dock, then click Relaunch
- All hidden files will now be visible in Finder
- To hide files again, type
defaults write com.apple.finder AppleShowAllFiles NOin Terminal
This will reveal system files like .DS_Store, .localized, and files starting with a period. Users can access these hidden files easily using the methods above.
Deleting Question Mark Files
While some hidden macOS system files like .DS_Store can be safely deleted, caution should be taken before removing files that start with a period. Many of these files are important for the system to function properly.
For example, files like .fseventsd store metadata needed by Spotlight search, and deleting them could lead to problems or data loss. The .VolumeIcon.icns file controls the icon image for the volume in Finder.
That said, some hidden files are safe to remove if unwanted. A common one is .DS_Store, which stores custom folder view settings. To delete .DS_Store files, open the Terminal app and run commands like:
“find . -name ‘*.DS_Store’ -delete” to remove from a folder and subfolders.
“sudo rm -rf /.DS_Store” to delete the user’s .DS_Store file.
Just be very careful about removing macOS system files in general. First research whether the file serves an important function or not. Back up data beforehand too in case of unintended consequences.
Sources:
https://macpaw.com/how-to/remove-ds-store-files-on-mac
https://stackoverflow.com/questions/30483670/delete-ds-store-files-in-current-folder-and-all-subfolders-from-command-line-on
Tips for Managing
To avoid issues with these files, it is best to exclude them from version control systems like Git. You can add .DS_Store to your .gitignore file to prevent Git from tracking these files (https://gist.github.com/lohenyumnam/2b127b9c3d1435dc12a33613c44e6308). If the files have already been committed, you can remove them from the repository with `git rm –cached .DS_Store` (https://stackoverflow.com/questions/107701/how-can-i-remove-ds-store-files-from-a-git-repository).
It is also a good idea to exclude these files from backups to avoid wasting space. You can add .DS_Store to your backup exclusion list. On Macs, you can exclude them from Time Machine backups in System Preferences.
Additionally, you may want to disable .DS_Store file creation entirely. This can be done by running `defaults write com.apple.desktopservices DSDontWriteNetworkStores -bool TRUE` in the Terminal (https://www.linkedin.com/pulse/how-remove-dsstore-files-from-git-repositories-chandan-thakur). This will prevent .DS_Store files from being created on network drives.
Origin of Convention
The convention of using a question mark (?) at the beginning of filenames to indicate special hidden files has been a part of Unix-based operating systems like macOS for decades.
This convention originated in Unix systems in the 1970s and 1980s. According to the Unix Stack Exchange, the practice of prefixing filenames with a dot to make them hidden was established very early in Unix history (1). Using a question mark for special hidden files emerged a bit later as a way to differentiate regular dotfiles from special system dotfiles.
Some of the earliest references to this convention come from Version 7 Unix in 1979 and the BSD Unix systems in the early 1980s. The BSD systems in particular made extensive use of filenames starting with “.” and “?” for system files. This convention was then carried over to macOS, since it is built on a BSD Unix foundation.
So in summary, the “?” prefix for special hidden files has been part of Unix and macOS for over 30 years, dating back to some of the earliest Unix systems in the 1970s and 80s.
On Other Platforms
Unlike Mac OS, other operating systems like Windows do not use the question mark symbol (?) to indicate hidden system files. In fact, using a question mark in a filename can cause issues on Windows.
On Windows, the question mark is a reserved character used as a wildcard in file searches. Having a question mark in a filename could lead to unintended results when searching for files. For example, searching for “file?” would return any filename starting with “file” which is not the intended behavior. This is why Windows discourages using ? in filenames.
Instead, Windows uses a different convention to indicate hidden system files. Files and folders prefaced with a dot (.) are hidden in Windows. For example, .DS_Store would be a hidden system file. So the use of the question mark is unique to Mac OS.
Overall, the convention for hidden files differs across platforms. While Mac uses ?, Windows relies on . to denote hidden system files. Being aware of these differences is helpful, especially when transferring files between operating systems.
Summary
In summary, the question mark in file names on Macs indicates that it is a hidden system file generated by macOS. These files help the system track preferences, caches, application states, and other internal data. While normally hidden from users, they can sometimes become visible if Show Hidden Files is enabled in Finder.
Knowing about these special hidden files can help Mac users understand what they are seeing if they do enable showing hidden files. While they can generally be left alone, it’s useful to know they can sometimes be safely deleted if they get too large and start taking up disk space. Overall, the question mark naming convention is just an interesting behind-the-scenes aspect of how macOS manages system files.