I thought I’ll make this thread for all of you out there who have questions but are afraid to ask them. This is your chance!
I’ll try my best to answer any questions here, but I hope others in the community will contribute too!
I thought I’ll make this thread for all of you out there who have questions but are afraid to ask them. This is your chance!
I’ll try my best to answer any questions here, but I hope others in the community will contribute too!
How do symlinks work from the point of view of software?
Imagine I have a file in my downloads folder called movie.mp4, and I have a symlink to it in my home folder.
Whenever I open the symlink, does the software (player) understand «oh this file seems like a symlink, I should go and open the original file», or it’s a filesystem level stuff and software (player) basically has no idea if a file I’m opening is a symlink or the original movie.mp4?
Can I use sync software (like Dropbox, Gdrive or whatever) to sync symlinks? Can I use sync software to sync actual files, but only have symlinks in my sync folder?
Is there a rule of thumb to predict how software behaves when dealing with symlinks?
I just don’t grok symbolic links.
A symlink works more closely to the first way you described it. The software opening a symlink has to actually follow it. It’s possible for a software to not follow the symlink (either intentionally or not).
So your sync software has to actually be able to follow symlinks. I’m not familiar with how gdrive and similar solutions work, but I know this is possible with something like rsync
So I guess it’s something like pressing ctrl+c: most software doesn’t specifically handle this hotkey so in general it will interrupt a running process, but software can choose to handle it differently (like in vim ctrl+C does not interrupt it).
Thanks.
Fun fact: pressing X (close button) on a window does not make it that your app is closed, it just sends a signal that you wish to close it, your app can choose what to do with this signal.
An application can know that a file represents a soft link, but they don’t need to do anything differently to follow it. If the program just opens it, reads it, writes to it, etc, as though it were the original file, it will just worktm without them needing to do anything differently.
It is possible for the software to not follow a soft symlink intentionally, yes (if they don’t follow it unintentionally, that might be a bug).
As for hard links, I’m not as certain, but I think these need to be supported at the filesystem level (which is why they often have specific restrictions), and the application can’t tell the difference.
A symlink is a file that contains a shortcut (text string that is automatically interpreted and followed by the operating system) reference to another file or directory in the system. It’s more or less like Windows shortcut.
If a symlink is deleted, its target remains unaffected. If the target is deleted, symlink still continues to point to non-existing file/directory. Symlinks can point to files or directories regardless of volume/partition (hardlinks can’t).
Different programs treat symlinks differently. Majority of software just treats them transparently and acts like they’re operating on a “real” file or directory. Sometimes this has unexpected results when they try to determine what the previous or current directory is.
There’s also software that needs to be “symlink aware” (like shells) and identify and manipulate them directly.
You can upload a symlink to Dropbox/Gdrive etc and it’ll appear as a normal file (probably just very small filesize), but it loses the ability to act like a shortcut, this is sometimes annoying if you use a cloud service for backups as it can create filename conflicts and you need to make sure it’s preserved as “symlink” when restored. Most backup software is “symlink aware”.
Software opens a symlink the same way as a regular file. The kernel reads a path stored in a symlink and then opens a file with that path (or returns a error if unable to do this for some reason). But if a program needs to perform specific actions on symlinks, it is able to check the file type and resolve symlink path.
To determine how some specific software handle symlinks, read its documentation. It may have settigs like “follow symlinks” or “don’t follow symlinks”.
its a pointer.
Others have answered well already, I just will say that symlinks work at the filesystem level, but the operating system is specially programmed to work with them. When a program asks the operating system to open a file at a given path, the OS will automatically “reference” the link, meaning it will detect a symlink and jump to the place where the symlink is pointing.
A program may choose to inspect whether a file is a symlink or not. By default, when a program opens a file, it simply allows the operating system to reference the file path for it.
But some apps that work on directories and files together (like “
find”, “tar”, “zip”, or “git”) do need to worry about symlinks, and will check if a path is a symlink before deciding whether to reference it. For example, you can ask the “find” command to list only symlinks without referencing them:find -type lELI5: when a computer stores something like a file or a folder, it needs to know where it lives and where its contents are stored. Normally where the a file or folder lives is the same place as where its contents are. But there are times where a file may live in one place and its contents are elsewhere. That’s a symlink.
So for your video example, the original video is located in Downloads so the video file will say I am movie.mp4 and I live i live in downloads, and my contents are in downloads. While the symlink says, I am movie.mp4 I live in home, and my contents are in downloads over there.
For a video player, it doesn’t care if the file and the content is in the same place, it just need to know where the content lives.
Now how software will treat a symlink as an absolute. For example if you have 2 PCs synced with cloud storage, and both downloads and home is being synced between your 2 pcs. Your cloud storage will look at the symlink, access the content from pc1 and put your movie.mp4 in pc2’s downloads and home. But it will also put the contents in both places in pc2 since to it, the results are the same. One could make software sync without breaking the symlink, but it depends on the developer and the scope of the software.