Shared data location for Linux and Mac OS X

Question

On Windows, there is a standard location for application data that is shared in common with all users on the machine (i.e. in Vista/7, (root):\ProgramData). I'm looking for a way to get such a folder on other platforms using Qt.

• Does Qt provide a built-in method for doing this? (QDesktopServices looked promising, but does not seem to provide this option.)
• If not, what are the standard locations on Linux and Mac OS X systems for shared application data? Is /usr/share the correct place? Is there a standard at all?

[CLARIFICATION] This is for mutable data.

Answer 1

I don't know if Qt provides an API for that. Here's the OS X specific information.

On OS X, it depends whether it's a GUI app or unix level support libraries. For a GUI app, it's the standard practice to have all the read-only data shared by all users inside the app bundle itself. Typically you have

  YourApp.app/
  YourApp.app/Contents
  YourApp.app/Contents/MacOS
  YourApp.app/Contents/MacOS/YouApp      .... this is the binary
  YourApp.app/Contents/Resources/        .... here are all the shared data

The GUI presents the directory YourApp.app as the application itself, so that you can copy/move it around without any problem. If that's not possible, it's recommended to use the subdirectory of

/Library/Application Support/name_of_your_app/

for data shared among users.

It's a bad idea to have a mutable, shared data among users on a machine; in general it's impossible due to the access restrictions. Note that a standard user might not have, and in fact usually does not have an administrative right to write into a shared location.

For mutable data specific to a user, use

~/Library/Application Support/name_of_your_app/

See this Apple guideline for more info.

Answer 2

The File System Hierarchy Standard suggest that /usr/share should be used for read-only architecture independent data files, and /var/lib should be used for state information pertaining to an application or the system.

You didn't specify whether you're referring to read-only or mutable state, but the wording of your question (specifically the comparison to %COMMONAPPDATA%) suggests mutable state, in which case /var/lib would be appropiate. Don't forget to have a user group with write rights to your subdirectory there available (or created by the package installation script) and have the sysadmin add the appropiate users to that group.

Answer 3

On Mac OS, one solution is to use the /Users/Shared directory, since it is read/write for all users, and is therefore mutable for everyone. Have to make sure any files you create in there are read/write for everyone too.

Or you can use app support as suggested by others, and making any files you need to be mutable read/write for everyone, but that means an admin needs to create them first, either through an installer or first run, which is a little ugly.

My company is using Users/Shared for exactly this purpose, but I don't know how "neat" it is considered.