rappdirs is a port of appdirs to R.

The problem

What directory should your app use for storing user data? If running on Mac OS X, you should use:

~/Library/Application Support/<AppName>

If on Windows (at least English Win XP) that should be:

C:\Documents and Settings\<User>\Application Data\Local Settings\<AppAuthor>\<AppName>

or possibly:

C:\Documents and Settings\<User>\Application Data\<AppAuthor>\<AppName>

for roaming profiles but that is another story.

On Linux (and other Unices) the dir, according to the XDG spec (and subject to some interpretation), is either:

~/.config/<AppName>     

or possibly:

~/.local/share/<AppName>

rappdirs to the rescue

This kind of thing is what the appdirs module is for. appdirs will help you choose an appropriate:

• user data dir (user_data_dir)
• user config dir (user_config_dir)
• user cache dir (user_cache_dir)
• site data dir (site_data_dir)
• user log dir (user_log_dir)

and also:

• is slightly opinionated on the directory names used. Look for 'Opinion' in documentation and code for when an opinion is being applied.

some example output

On Mac OS X:

library(appdirs)
appname <- "SuperApp"
appauthor <- "Acme"
user_config_dir(appname, appauthor)
# "/Users/trentm/Library/Application Support/SuperApp"
user_data_dir(appname, appauthor)
# "/Users/trentm/Library/Application Support/SuperApp"
site_data_dir(appname, appauthor)
# "/Library/Application Support/SuperApp"
user_cache_dir(appname, appauthor)
"/Users/trentm/Library/Caches/SuperApp"
user_log_dir(appname, appauthor)
"/Users/trentm/Library/Logs/SuperApp"

On Windows 7:

library(appdirs)
appname <- "SuperApp"
appauthor <- "Acme"
user_config_dir(appname, appauthor)
# "C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp"
user_data_dir(appname, appauthor)
# "C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp"
user_data_dir(appname, appauthor, roaming=True)
# "C:\\Users\\trentm\\AppData\\Roaming\\Acme\\SuperApp"
user_cache_dir(appname, appauthor)
# "C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp\\Cache"
user_log_dir(appname, appauthor)
# "C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp\\Logs"

On Linux:

library(appdirs)
appname <- "SuperApp"
appauthor <- "Acme"
user_config_dir(appname, appauthor)
# "/home/trentm/.config/SuperApp
user_data_dir(appname, appauthor)
# "/home/trentm/.local/share/SuperApp
site_config_dir(appname, appauthor)
# "/etc/xdg/SuperApp"
user_cache_dir(appname, appauthor)
# "/home/trentm/.cache/SuperApp"
user_log_dir(appname, appauthor)
# "/home/trentm/.cache/SuperApp/log"

app_dir for convenience

library(appdirs)
dirs <- app_dir("SuperApp", "Acme")
dirs$config()
# "/Users/trentm/Library/Application Support/SuperApp"
dirs$data()
# "/Users/trentm/Library/Application Support/SuperApp"
dirs$site_data()
# "/Library/Application Support/SuperApp"
dirs$cache()
# "/Users/trentm/Library/Caches/SuperApp"
dirs$log()
# "/Users/trentm/Library/Logs/SuperApp"

Per-version isolation

If you have multiple versions of your app in use that you want to be able to run side-by-side, then you may want version-isolation for these dirs:

library(appdirs)
dirs <- app_dir("SuperApp", "Acme", version = "1.0")
dirs$data()
# "/Users/trentm/Library/Application Support/SuperApp/1.0"
dirs$site_data()
# "/Library/Application Support/SuperApp/1.0"
dirs$cache()
# "/Users/trentm/Library/Caches/SuperApp/1.0"
dirs$log()
# "/Users/trentm/Library/Logs/SuperApp/1.0"

If you set the argument expand = TRUE (the default) you can have directories that correspond to R versions:

user_config_dir("R", version="%p-platform/%v")
# "/home/trevorld/.config/R/x86_64-pc-linux-gnu-platform/3.0"