What Does unlink Actually Do?
Although I now forget the context, a friend once sent me a snippet of shell code that he was using to remove symbolic links to files on his computer, using a shell command that I had never seen before: unlink.
I, like him (and presumably like you if this is your first exposure to the command), assumed that this command is used to remove links to files on a UNIX-like system.
This is quite an understandable assumption, as the name of the command quite literally implies that it undoes links, but more importantly because it works;
if you run unlink path_to_some_link on a link to a file (symbolic or otherwise), the link will be removed.
It seems to me that quite a lot of people use unlink to remove symbolic links to files, and it works perfectly well despite the command not being the link-remover that it appears to be at first glance.
In reality, unlink is not a link-remover (in that sense):
instead, it is an interface to your system’s unlink function, which is how files are deleted “under the hood” on UNIX-like systems.
This is why it works perfectly well for deleting links on your computer: it deletes any file it’s directed to, regardless of whether or not it’s a link to another file.
Strictly speaking, the unlink command (like the rm command) removes a name for a file in the filesystem, and if that name is the last renaming name for the file in that filesystem, the file will be deleted entirely;
if there are other names for the file in the filesystem (if, say, a hard link has been created), then the file will remain in the filesystem until all of its names are removed or unlinked.
The unlink syscall is how the rm command works under the hood:
in this sense, the rm and unlink commands do exactly the same thing, just with slightly different interfaces.
So, while it’s not wrong to delete links to files using the unlink command, it is wrong to think that unlink is necessary to delete links to files or that it’s the only correct way to delete links to files.
The only difference between the two commands is the interface: rm has more options and can delete multiple files at a time, whereas unlink just deletes a single file.