Where/How to save a preferences file in a *nix command line utility? - linux

Question

I am writing a small command line utility. It should hopefully be able to run on OSX, UNIX and Linux.
It needs to save a few preferences somewhere, like in a small YAML config file.
Where would one save such a file?
Language: Python 2.7
OS: *nix

Answer 1

Commonly, these files go somewhere like ~/.rc (eg: ~/.hgrc). This could be the path to a file, or to a directory if you need lots of configuration settings.
For a nice description see http://www.linuxtopia.org/online_books/programming_books/art_of_unix_programming/ch10s03.html

Answer 2

I would avoid putting the file in the ~ directory only because it has gotten totally flooded with crap. The recent trend, at least on ubuntu, is to use ~/.config/<appname>/ for whatever dot files you need. I really like that convention.

Answer 3

If your application is named "someapp" you save the configuration in a file such as $HOME/.someapp. You can give the config file an extension if you like. If you think your app may have more than one config file you can use the directory $HOME/.someapp and create regular-named (not hidden) files in there.

Answer 4

Many cross-platform tools use the same path on OS X as on linux (and other POSIX/non-Windows platforms). The main advantage of using the POSIX locations isn't saving a few lines of code, but saving the need for Mac-specific instructions, and allowing Mac users to get help from the linux users in the community (without any need to translate their suggestions).
The other alternative is to put them in the "Mac-friendly" locations under ~/Library instead. The main advantage of using the Mac locations is basically "Apple says so"—unless you plan to sandbox your code, in which case the main advantage is that you can do so.
If you choose to use the Library locations, you should read About the OS X File System and OS X Library Directory Details in the File System Programming Guide, but here's the short version:
Almost everything: Create a subdirectory with your app's name or bundle ID (unless you're going out of your way to set a bundle ID, you'll get org.python.python, which you don't want…) under ~/Library/Application Support. Ideally you should use APIs like -[NSFileManager URLForDirectory:inDomain:appropriateForURL:create:error:] to get the path; if not, you have to deal with things like localization, sandbox containers, etc. manually.
Anything that can be easily re-created (so it doesn't need to be backed up, migrated, etc.): An identically-named subdirectory of ~/Library/Caches.
Preferences: Use the NSUserDefaults or CFPreferences APIs instead. If you use your own format, the "old" way of doing things is to create a subdirectory under ~/Library/Preferences named with your app's name or bundle ID, and put your files in that. Apple no longer recommends that, but doesn't really recommend an alternative (short of "use CFPreferences, damnit!"); many apps (e.g., Aquamacs) still do it the old way, but others instead pretend they're not preferences and store them under Application Support.
In Python, this works as follows (leaving out the error handling, and assuming you're going by name instead of setting a bundle ID for yourself):
from Foundation import *
fm = NSFileManager.defaultManager()
appsupport = (fm.URLForDirectory_inDomain_appropriateForURL_create_error_(
NSApplicationSupportDirectory, NSUserDomainMask, None, True, None)[0].
URLByAppendingPathComponent_isDirectory_(
appname, True))
caches = (fm.URLForDirectory_inDomain_appropriateForURL_create_error_(
NSCachesDirectory, NSUserDomainMask, None, True, None)[0].
URLByAppendingPathComponent_isDirectory_(
appname, True))
prefs = NSUserDefaults.persistentDomainForName_(appname)