Symbolic link and alias in Mac.

In Mac OS X, you have two choices when you want to have a file that has a link to an exisiting file: alias (Command L), and symbolic link (Shift-Command L).

Command line tools can understand a symbolic link, not an alias. For GUI tools, e.g., PathFinder, both an alias and symbolic link will work. Automator, however, works only with alias. It’s understandable because link is a legacy from UNIX; so is command line tools. Likewise Automator is a legacy from Mac; so is an alias.

You’ll notice that alias link is larger, which means has more information. An alias has two pieces of information: UID of the file that it links to, and the physical path and file name that it links to. As a result alias will understand the changes you make to the original file.

A symbolic link doesn’t contain the UID. As a result symbolic link will be shown as broken when you change the name of the file that it links to.

Demo

1. Using “command-L”, I create an Alias.
2. Rename the progress directory as “progress_update”.
3. Click the “progress_update” to check Path Finder finds the linked directory correctly.

And this is an example for symbolic link.

1. Using “Shift-Command-L”, I create a symbolic link.
2. Change directory name.
3. Check Path Finder finds the link OK.

For the command line tools, the alias is just a file (color in black), however the symbolic link is recognizable (color in pink).

And you can use command line tools for the change.

In short

• Use symbolic link when you want to use command line tools, for example when you want to use Linux to login your mac account.
• Use alias when you work with your mac, as it will understand your changes.

References

• What's the difference between alias and link?
• What's the tool that can do some actions when a file is copied?