[R] automatic history file append with every command?

[Mike Miller]

In the bash shell we can use PROMPT_COMMAND="history -a" to tell bash to 
always append the last command to the history file.  It will do this with 
every command so that if bash crashes or an ssh connection is lost, the 
command history will still be available in the history file.

With R, I see there is a savehistory() command (link below), but I have 
some questions:

(1) does savehistory() append to the current history file or overwrite it?

(2) if it appends, when savehistory() is evoked repeatedly, does it only 
append commands that haven't already been appended?  Or does it append the 
entire history to the file?

(3) Is there a way to evoke history saving automatically so that the file 
is always updated?


I have the impression that savehistory() only overwrites and cannot 
append.  If that's true, I might still get what I want, but I'd be doing a 
lot of unnecessary writing.  Luckily, my R history is usually quite short. 
So if I were to enter 100 commands, appending would write 100 lines, but 
overwriting would write 5050 lines.


savehistory:

http://stat.ethz.ch/R-manual/R-devel/library/utils/html/savehistory.html


Best,
Mike

--
Michael B. Miller, Ph.D.
Minnesota Center for Twin and Family Research
Department of Psychology
University of Minnesota