On 13-10-18 8:32 PM, Jonathan Greenberg wrote:
R-developers:
Duncan Murdoch suggested I move a post I started on r-help over here,
since it is more at the developer level. Here is my
question/challenge -- to my knowledge, there is not currently an
official way to store a *package*'s options to a standardized location
on a user's computer. Given that OS-level programs have standard
preference locations, I was hoping to first assess:
- Does R, in fact, have a place for a *package* to store preferences
(a file-based "setOptions") that would be persistent across sessions.
One suggestion that was given was to perhaps write these options to
the .RProfile, but this strikes me as potentially dangerous -- a
poorly written function to write to a user's .RProfile could corrupt
it.
I think you misread that suggestion. I think it was a suggestion that
the user should write that information into their own .RProfile.
What I'd suggest you do is have two functions, saveFooOptions and
loadFooOptions in your package Foo. (The exact names aren't important,
but don't use generic names like saveOptions and loadOptions; other
packages may want to follow your model.) Instruct the user to set the
options in a session, then call saveFooOptions to save them. Tell them
how to put loadFooOptions into their .RProfile file if they want them
loaded automatically at startup.
Currently the only files that R writes automatically are .RData and
.RHistory. It only writes those after confirmation from the user, and
they are not written to a standard location, so users can maintain
multiple copies of them. Packages should be no more intrusive.
On Windows, the R GUI maintains a collection of preferences, but they
are never written automatically. The loadRconsole() function can load
them from an arbitrary file; they are saved from a dialog in the GUI.
There's a default set in the R install directory, but often users don't
have write permission there. You could do the same, having a default
set of options in your package installation, but you shouldn't assume
the user has rights to change it.
If the answer to the initial question is "no" (there is not an
official location/approach for a package to store its own files), I'd
like to suggest we open this for a wider discussion amongst the
developers, to perhaps come up with a general (not package-by-package)
solution for a package to store options (and perhaps other files) in a
standard location.
The particular application that has brought me to asking about this is
that I'm writing a package that has external calls to command-line
programs that may not be properly registered with a user's environment
(think: Windows, in particular, although I've found issues with a Mac
as well), so the first step of these R - wrapper functions is to
search a user's local machine for the binaries. If it finds it, it
stores the path to this binary as an option. Since this is a
brute-force search, this can take some time and, ideally, this
information would be preserved across sessions, without the function
having to re-search their drive every time they start R fresh.
That sounds like a case where a user might choose to save the locations.
But you shouldn't do it without asking, and you should allow the user
to decide where the file goes.
Duncan Murdoch
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